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Williams WPC

2026-09-25T19:28:01Z

The Hammer: /* Opto Switches */ Created a GIF to show the basic operation of the Opto Board circuit.

Click to go back to the [[Williams_Repair_Guides | Williams solid state repair guides index]].

==Introduction==
This guide covers Williams WPC-089, WPC-S, and WPC-95 games. Collectively, they are referred to as WPC games.

==Game List==
===WPC (WPC-089) CPU===
====WPC (Alphanumeric)====
*[[Funhouse]]
*[[Harley-Davidson]]
*[[The Machine: Bride of Pin*Bot]]

====WPC (Dot Matrix)====
*[[Gilligan's Island]]
*[[Terminator 2: Judgement Day]]
*[[Hurricane]]
*[[Party Zone]]

====WPC FlipTronics I & II====
*[[The Addams Family]] / Addams Family Gold (the only Fliptronics I games)
*[[The Getaway: High Speed II]]
*[[Black Rose]]
*[[Fish Tales]]
*[[Doctor Who]]
*[[Creature from the Black Lagoon]]
*[[White Water]]
*[[Bram Stoker's Dracula]]
*[[Twilight Zone]]

====WPC DCS Sound====
*[[Indiana Jones: The Pinball Adventure]]
*[[Judge Dredd]]
*[[Star Trek: The Next Generation]]
*[[Popeye Saves The Earth]]
*[[Demolition Man]]

===WPC-S with DCS Sound===
*[[World Cup Soccer]]
*[[The Flintstones]]
*[[Corvette]]
*[[Red & Ted Road Show]]
*[[The Shadow]]
*[[Dirty Harry]]
*[[Theatre of Magic]]
*[[No Fear: Dangerous Sports]]
*[[Indianapolis 500]]
*[[Johnny Mnemonic]]
*[[Jack*Bot]]
*[[WHO Dunnit]]

===WPC-95 CPU===
*[[Congo]]
*[[Attack from Mars]]
*[[Safecracker|Safe Cracker]]
*[[Tales of the Arabian Nights]]
*[[Scared Stiff]]
*[[Junk Yard]]
*[[NBA Fastbreak]]
*[[Medieval Madness]]
*[[Cirqus Voltaire]]
*[[No Good Gofers]]
*[[The Championship Pub|The Champion Pub]]
*[[Monster Bash]]
*[[Cactus Canyon]]

==Game List Chart==

===WPC-89 & WPC-S===

{| class="wikitable sortable"
|-
!Game
!WPC System
!MPU
!Driver Board
!Display Driver
!Display
!Sound
!Flipper
!Transformer
!Additional Boards
!Notes

|-
|[[Dr. Dude]]
|WPC-89 Alphanumeric / System 11
|WPC-89 (A-12742)
|A-12697-1
|A-12739-1
|Alphanumeric, dual display (A-12793)
|D-11581-2016 with a special power supply board (A-13502)
|N/A
|5610-12718-00 (WPC) or 5610-12136-00 (System 11)?
|Sound overlay board (A-13502)
|Only about 100 Dr. Dude sample games use the WPC boardset. They included a special power supply board (A-13502) to accommodate the System 11 sound board (D-11581), and also includes the System 11 interconnect board (D-12313-2016). The bulk of the production run used the [[Williams System 9 - 11|System 11C boardset]].
|-

|-
|[[Funhouse]]
|WPC-89 Alphanumeric
|WPC-89 (A-12742)
|A-12697-1
|A-12739-1
|Alphanumeric, dual display (A-12793)
|A-12738-50003
|N/A
|5610-12718-00
|
|Early FH games had a System 11 sound board (D-11581 / A-13971) with a special power supply board (A-13502) and a 5610-12425-00 transformer. Later games used the WPC A-12738 sound board. [[media: Williams_1990_Funhouse_Prototype_Manual_Addendum.pdf|Funhouse Manual Addendum]]
|-

|[[Harley-Davidson]]
|WPC-89 Alphanumeric
|WPC-89 (A-12742)
|A-12697-1
|A-12739-1
|Alphanumeric, single display (A-12794)
|A-12738-20001
|N/A
|5610-12718-00
|
|
|-

|[[The Machine: Bride of Pin*Bot]]
|WPC-89 Alphanumeric
|WPC-89 (A-12742)
|A-12697-1
|A-12739-1
|Alphanumeric, dual display (A-12793)
|A-12738-50002
|N/A
|5610-12718-00
|
|
|-

|[[Slugfest]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-60001
|N/A
|5610-12835-00
|
|Pitch & Bat game.
|-

|[[Gilligan's Island]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20003
|N/A
|5610-12835-00
|
|
|-

|[[Terminator 2: Judgement Day]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50013
|N/A
|5610-12835-00
|
|
|-

|[[Hurricane]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50012
|N/A
|5610-12835-00
|
|
|-

|[[Party Zone]]
|WPC-89 Dot Matrix / WPC-89 Fliptronic I
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20004
|N/A
|5610-12835-00
|
|Some later PZ games started transitioning over to use the Fliptronic I board (A-15028). Different game ROMs are used depending upon if the PZ uses solid state flippers or fliptronic/standard flippers.
|-

|[[Hot Shot]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50017
|N/A
|5610-12835-00
|
|Redemption game.
|-

|[[The Addams Family]]
|WPC-89 Fliptronic I
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20017
|A-15028
|5610-12835-00
|Extra flipper power supply (A-15416)
|
|-

|[[The Getaway: High Speed II]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50004
|A-15472
|5610-12835-00
|
|
|-

|[[Black Rose]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20013
|A-15472
|5610-12835-00
|
|
|-

|[[Doctor Who]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20006
|A-15472
|5610-12835-00
|
|
|-

|[[Fish Tales]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50005
|A-15472
|5610-12835-00
|
|
|-

|[[Creature from the Black Lagoon]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20018
|A-15472
|5610-12835-00
|
|
|-

|[[White Water]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50018
|A-15472
|5610-12835-00
|
|
|-

|[[Bram Stoker's Dracula]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50001
|A-15472
|5610-12835-00
|
|
|-

|[[Twilight Zone]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1 or A-12697-3
|A-14039
|DMD
|A-12738-50020
|A-15472
|5610-12835-00
|Auxiliary 8-Driver PCB (A-16100)
|Mid-way through TZ's production run, the A-12697-1 driver board starting being replaced with A-12697-3. At some point during production, a coin door interlock switch was added in order to cut high voltage 20VDC/50VDC power as a safety measure when the coin door was opened; this was included in all WPC titles from this point forward.
|-

|[[Indiana Jones: The Pinball Adventure]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-3
|A-14039
|DMD
|A-16917-50017
|A-15472-1
|5610-13491-00
|Auxiliary 8-Driver PCB (A-16100)
|
|-

|[[Judge Dredd]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-3
|A-14039
|DMD
|A-16917-20020
|A-15472-1
|5610-13491-00
|
|
|-

|[[Star Trek: The Next Generation]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-16917-50023
|A-15472-1
|5610-13491-00
|Auxiliary 8-Driver PCB (A-16100)
|Driver board was changed to A-12697-1.
|-

|[[Demolition Man]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-3
|A-14039
|DMD
|A-16917-50028
|A-15472-1
|5610-13953-00
|Auxiliary 8-Driver PCB (A-16100)
|A few prototype games used a WPC-S MPU, which uses a different ROM in order to work with the WPC-S security PIC. The standard ROM for WPC-89 boards will not work on the WPC-S board, but a WPC-89 MPU can be swapped in to replace the WPC-S MPU. All the sample and production games used a WPC-89 MPU.
|-

|[[Popeye Saves The Earth]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-3
|A-14039
|DMD
|A-16917-50022
|A-15472-1
|5610-13491-00
|
|
|-

|[[World Cup Soccer]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039
|DMD
|A-16917-50031
|A-15472-1
|5610-13953-00
|
|
|-

|[[The Flintstones]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50029
|A-15472-1
|5610-13953-00
|
|Some revisions were made on the A-14039.1 DMD driver board, but it is interchangeable with A-14039.
|-

|[[Corvette]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50036
|A-15472-1
|5610-13953-00
|Auxiliary 8-Driver PCB (A-16100)
|
|-

|[[Red & Ted Road Show|Red & Ted's Road Show]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50024
|A-15472-1
|5610-13953-00
|Auxiliary 8-Driver PCB (A-16100)
|The transformer was moved to the rear of the cabinet starting with this game.
|-

|[[The Shadow]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50032
|A-15472-1
|5610-13953-00
|
|
|-

|[[Dirty Harry]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50030
|A-15472-1
|5610-13953-00
|
|
|-

|[[Theatre of Magic]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50039
|A-15472-1
|5610-14515-00
|
|
|-

|[[No Fear: Dangerous Sports]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50025
|A-15472-1
|5610-14515-00
|
|
|-

|[[Indianapolis 500]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50026
|A-15472-1
|5610-14515-00
|
|
|-

|[[Johnny Mnemonic]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50042
|A-15472-1
|5610-14515-00
|
|
|-

|[[WHO Dunnit]]
|WPC-S
|WPC-S (A-17651)
|A-12697-4
|A-14039.1
|DMD
|A-16917-50044
|A-15472-1
|5610-14515-00
|
|This was the only game to use a A-12697-4 driver board.
|-

|[[Jack*Bot]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50051
|A-15472-1
|5610-14515-00
|
|
|-
|}

===WPC-95===

{| class="wikitable sortable"
|-
!Game
!WPC System
!MPU
!Driver Board
!AV Board
!Display
!Transformer
!Additional Boards
!Notes
|-

|[[Congo]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|The first WPC-95 game. The A-20516 AV Board drives both sound and the DMD. The A-20028 driver board included flipper power circuits, eliminating the need for a separate fliptronic board.
|-

|[[Attack from Mars]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[safecracker|Safe Cracker]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[Ticket Tac Toe]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|?
|
|Redemption game (with flippers).
|-

|[[Tales of the Arabian Nights]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[Scared Stiff]]
|WPC-95
|WPC-95 (A-20119 or A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|The first appearance of a revision to the MPU. A-20119 and A-21377 can be used interchangeably in any WPC-95 games.
|-

|[[Junk Yard]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[NBA Fastbreak]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-01
|
|
|-

|[[Medieval Madness]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-01
|
|
|-

|[[Cirqus Voltaire]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|DMD is mounted on the playfield, rather than in the backbox.
|-

|[[No Good Gofers]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[The Championship Pub|The Champion Pub]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[Monster Bash]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-01
|
|
|-

|[[Cactus Canyon]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-01
|
|
|-

|}

==Recommended Documentation==
===Manuals & Schematics===
Schematics for each game are essential in tracing down connections to lamps, switches, and solenoids. The owner's game manual is a handy resource to have for general game operation, game settings & diagnostics, switch & lamp matrices, fuse lists, circuit boards and parts, playfield assemblies, some basic schematics, and wiring diagrams.

Be aware that although rare, some factory documentation contains errors in schematics, wiring, switch/lamp matrices, and solenoid assignments.

Some games have information split between two manuals: a game manual (for general game operation) and an operations guide (for more technical information).

{| class="wikitable"
|-
!Guide
!Version
!Cover
!Source
!Notes

|-
|Pinball Safety Manual
|16-10371, January 1, 1997
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Manual contains multiple languages.

|}

===Theory of Operation & Schematics===
Details for board and cabinet schematics and theory of operation guides for WPC games can be found in separate documents. There are several versions of each generation. Some copies can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball].

{| class="wikitable"
|-
!Guide
!Version
!Cover
!Source
!Notes

|-
|WPC Theory of Operation and Schematics Manual
|16-9289, October 1991
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/djtz/ Viewer for Guide] [https://online.fliphtml5.com/vrtyz/pgds/ Viewer for Schematics]
|

|-
|WPC Schematic Manual
|16-9473 (undated)
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.

|-
|WPC Schematic Manual
|16-9473-1, May 17, 1993
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/wrhm/ Viewer] [[media:Williams-WPC-Schematics_16-9473-1.pdf|PDF]]
|Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.

|-
|WPC Schematic Manual
|16-9473-2, April 25, 1994
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.

|-
|WPC Schematic Manual
|16-9834, June 1994
|[[file:placeholder.jpg|thumb|left|140px]]
|
|

|-
|WPC Schematic Manual
|16-9834.2, January 1995
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/fsgs/ Viewer]
|

|-
|WPC-S (Security) Schematic Manual
|
|[[file:placeholder.jpg|thumb|left|140px]]
|
|

|-
|WPC-95 Schematic Manual
|16-10159.2, March 1996
|[[file:placeholder.jpg|thumb|left|140px]]
|
|

|-
|WPC-95 Schematic Manual
|16-10159.3, July 1997
|[[file:placeholder.jpg|thumb|left|140px]]
|[[media:Williams-WPC-95-Schematics-Manual_16-10159.3.pdf|PDF]]
|

|}

===Parts Catalogs===
Parts catalogs can also be useful, which include part numbers (helpful for purchasing parts online), exploded views of assemblies (helpful to see how the assemblies are put together), and board layouts & parts lists, and diagrams for controlled lamp, solenoid, and rubber locations. Parts catalogs also had supplementary updates to add and replace pages as newer games were released after the initial release of the catalogs.

Online copies of Bally & Williams parts catalogs can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball].

{| class="wikitable"
|-
!Manufacturer
!Catalog
!Version
!Cover
!Source
!Games
!Notes

|-
|Williams
|Blue Parts Catalog (1984-1987)
|16-9064
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Comet, F-14 Tomcat, Grand Lizard, High Speed, Millionaire, Pin Bot, Road Kings, Sorcerer, Space Shuttle
|This was an early version of the blue parts catalog, and only included 9 pinball titles (and 3 shuffle alley titles). The pages of this catalog were printed on white paper. Additional titles were later included in a "parts catalog supplement" packet (16-9064-A) with blue-colored pages, which added and replaced pages for this earlier version of the parts catalog.

|-
|Williams
|Blue Parts Catalog (Supplementary Catalog) (1987-1988)
|16-9064-A
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Banzai Run, Big Guns, Cyclone, Fire!, Space Station, Swords of Fury, Taxi
|This "parts catalog supplement" packet with blue-colored pages added and replaced pages for the earlier version of the parts catalog. It included 7 new pinball titles not included in the previous version of the parts catalog. Later catalogs had these new pages included and were not colored blue.

|-
|Williams
|'''Blue Parts Catalog (1984-1989)'''
|'''16-9064-B'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/rvsk/ Viewer] [[media:Williams-parts-catalog-blue-book_16-9064-B.pdf|PDF]]
|Banzai Run, Big Guns, Black Knight: 2000, Comet, Cyclone, Earthshaker!, F-14 Tomcat, Fire!, Grand Lizard, High Speed, Jokerz!, Millionaire, Pin Bot, Police Force, Road Kings, Sorcerer, Space Shuttle, Space Station, Swords of Fury, Taxi
|This is the latest version of the blue parts catalog. It included the game titles in the previous version, information from the supplementary parts catalog, a few new pinball titles, and a total of 5 shuffle alley titles. The blue parts catalog came in a blue-colored binder with the catalog's cover and game titles printed on the front, and basic information printed on the spine. The pages of this catalog were printed on pink paper.

|-
|Williams
|Red Parts Catalog (1989-1990)
|16-9190
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Bad Cats, Diner, Rollergames, Whirlwind
|The red parts catalog came in a red-colored binder with some basic information printed on the cover and spine. This version of the parts catalog included 4 pinball titles and 2 shuffle alley titles. The pages were printed on white-colored paper.

|-
|Williams
|Red Parts Catalog
|16-9190-A
|[[file:placeholder.jpg|thumb|left|140px]]
|
|(currently unverified)
|The red parts catalog came in a red-colored binder with some basic information printed on the cover and spine. This was a supplementary parts catalog that updated pages and added titles to the previous version of the red parts catalog. The pages were printed on blue-colored paper.

|-
|Williams
|'''Red Parts Catalog (Supplementary Catalog) (1989-1992)'''
|'''16-9190-B'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/feme/ Viewer] [[media:Williams-parts-catalog-red-book_16-9190-B.pdf|PDF]]
|Bad Cats, Diner, Dracula, Fish Tales, Funhouse, The Getaway, Hurricane, The Machine: Bride of Pin Bot, Riverboat Gambler, Rollergames, Slugfest, Terminator 2, Whirlwind, White Water
|The red parts catalog came in a red-colored binder with some basic information printed on the cover and spine. This version of the parts catalog included 13 pinball titles, and 5 shuffle alley titles, 7 video came titles, and 3 novelty game titles. The pages were printed on gray-colored paper.

|-
|Bally/Midway
|Yellow Parts Catalog (1988-1990)
|16-9147
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Atlantis, Elvira, Game Show, Mousin' Around, Transporter, Truck Stop
|The yellow parts catalog came in a yellow-colored binder with some basic information printed on the cover and spine. The pages were printed on white-colored paper.

|-
|Bally/Midway
|Yellow Parts Catalog (Supplementary Catalog) (1988-1991)
|16-9147-A
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Atlantis, Bugs Bunny, Dr. Dude, Elvira, Game Show, Harley Davidson, Mousin' Around, Pool Sharks, Radical!, Transporter, Truck Stop
|The yellow parts catalog came in a yellow-colored binder with some basic information printed on the cover and spine. This was a supplementary update to the previous version of the catalog, which included 11 pinball titles and 4 video game titles. The pages were printed on yellow-colored paper.

|-
|Bally/Midway
|'''Yellow Parts Catalog (1988-1992)'''
|'''16-9147-B'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/itjk/ Viewer] [[media:Bally-midway-parts-catalog-yellow-book_16-9147-B.pdf|PDF]]
|Addams Family, Atlantis, Black Rose, Bugs Bunny, Dr. Dude, Doctor Who, Elvira, Game Show, Gilligan's Island, Harley Davidson, Mousin' Around, Party Zone, Pool Sharks, Radical!, Transporter, Truck Stop
|The yellow parts catalog came in a yellow-colored binder with some basic information printed on the cover and spine. The pages were printed on gold-colored paper.

|-
|Bally/Midway
|Gray Parts Catalog (1992-1994)
|16-9562
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Creature From the Black Lagoon, Judge Dredd, Popeye Saves the Earth, Twilight Zone
|The gray parts catalog came in a white-colored binder with gray colored paper inserts for the spine and cover that included the company name, parts catalog, and part number. The pages were printed on white-colored paper.
|-
|Bally/Midway
|'''Gray Parts Catalog (Supplementary Catalog) (1992-1995)'''
|'''16-9562-A'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/ckao/ Viewer] [[media:Bally-midway-parts-catalog-gray-book_16-9562-A.pdf|PDF]]
|Addams Family Gold, Corvette, Creature From the Black Lagoon, Indianapolis 500, Judge Dredd, Popeye Saves the Earth, The Shadow, Theatre Of Magic, Twilight Zone, Who Dunnit, World Cup Soccer
|The gray parts catalog came in a white-colored binder with gray colored paper inserts for the spine and cover that included the company name, parts catalog, and part number. This was a supplementary update to the previous version of the catalog. The pages were printed on light blue colored paper.

|-
|Williams
|'''Green Parts Catalog (1993-1995)'''
|'''16-9932'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/foky/ Viewer] [[media:Williams-parts-catalog-green-book_16-9932.pdf ‎|PDF]]
|Demolition Man, Dirty Harry, Demolition Man, Indiana Jones, Road Show, Star Trek - Next Generation
|The green parts catalog came in a white-colored binder with green colored paper inserts for the spine and cover that included the company name, parts catalog, and part number. There was no supplementary update to this catalog.

|-
|Williams
|'''Genuine Replacement Parts Catalog (1997-1998)'''
|10/97
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/yjjv/ Viewer]
|
|This catalog mainly provides listings, parts numbers, and drawings of commonly replaceable generic pinball parts for Bally/Williams games, such as flipper assembly parts, target parts, posts, springs, connectors, coils, plungers, etc. It does not contain any game-specific information.

|}

===Service Bulletins===
Supplementary service bulletin books were released, which included service bulletins that detailed any problems or issues with games that were discovered after they were released.

{| class="wikitable"
|-
!Manufacturer
!Catalog
!Cover
!Source
!Games
!Notes

|-
|Williams
|Service Bulletin Book, 1991
|[[file:Williams-1991-service-bulletin-book-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1991.pdf|PDF]]
|Funhouse, Gilligan's Island, Harley Davidson, Slugfest, Terminator 2
|This book includes some System 11 games.

|-
|Williams
|Service Bulletin Book, 1992
|[[file:Williams-1992-service-bulletin-book-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1992.pdf|PDF]]
|Addams Family, Funhouse, Hurricane, Party Zone, Terminator 2
|

|-
|Williams
|Service Bulletin Book, Fall 1992
|[[file:Williams-1992-fall-service-bulletin-book-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1992-fall.pdf|PDF]]
|Addams Family, The Getaway, Strike Master (shuffle alley)
|

|-
|Williams
|Service Bulletin Book, 1993
|[[file:Williams-1993-service-bulletin-book-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1993.pdf|PDF]]
|Black Rose, Creature From the Black Lagoon, Doctor Who, Dracula, Fish Tales, NBA Jam, White Water
|

|-
|Williams
|Service Bulletin Book, 1994
|[[file:Williams-service-bulletin-book-1994-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1994.pdf|PDF]]
|Dracula, Indiana Jones, Judge Dredd, Star Trek the Next Generaton, Twilight Zone
|

|-
|Williams
|Service Bulletin Book, Fall 1994
|[[file:Williams-service-bulletin-book-1994-fall-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1994-fall.pdf|PDF]]
|Popeye, Indiana Jones, Star Trek, Addams Family, Demolition Man, Flintstones
|

|-
|Williams
|Service Bulletin Book, 1995
|[[file:Williams-service-bulletin-book-1995-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1995.pdf|PDF]]
|World Cup Soccer, Corvette
|

|-
|Williams
|Service Bulletin Book, 1996
|[[file:Williams-service-bulletin-book-1996-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1996.pdf|PDF]]
|Congo, No Fear, Indianapolis 500, Jackbot, Johnny Mnemonic, Road Show, The Shadow, Theatre of Magic
|

|-
|Williams
|Service Bulletin Book, 1997
|[[file:Williams-service-bulletin-book-1997-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1997.pdf|PDF]]
|Johnny Mnemonic, Junkyard, Safecracker, Scared Stiff, Tales of the Arabian Nights
|The last service bulletin included in this book was service bulletin 96.

|-
|Williams
|Service Bulletin Book, 1998
|[[file:Williams-1998-service-bulletin-book-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1998-incomplete.pdf|PDF (incomplete)]]
|Scared Stiff, NBA Fastbreak, Cirqus Voltaire, Medieval Madness
|According to the [[media:Williams-service-bulletin-book-1998-index.jpg|table of contents]], this includes (pinball) service bulletins 98, 99, 101, 102, 104, and two others. The original color of the cover is currently unknown. The PDF scan only includes some of the Medieval madness service bulletin and the fastbreak link kit installation instructions.
|-

|Williams
|Service Bulletin Book, 1999
|[[file:placeholder.jpg|thumb|left|140px]]
|
|
|The original color of the cover is currently unknown. Dated September 10, 1999. Presumably includes at least (pinball) service bulletin 107.
|-
|}

Individual Game-Specific Service Bulletins:

{| class="wikitable sortable"
|-
!Service Bulletin
!Date
!Game(s)
!Subject
!Notes

|-
|[[media:Bally_1996_Scared_Stiff_Service_Bulletin_93.pdf|93]]
|1996-12-20
|Scared Stiff
|Solving mechanism problems
|
|-
|[[media:Bally_1996_Scared_Stiff_Service_Bulletin_98.pdf|98]]
|1997-05-01
|Scared Stiff
|Repair Kit for Left Ramp Assembly
|
|-
|[[media:Bally_1997_NBA_Fastbreak_Service_Bulletin_99.pdf|99]]
|1997-05-14
|NBA Fastbreak
|For a ball trap on the right ramp
|Ball trap fix
|-
|[[media:Bally_1997_Cirqus_Voltaire_Service_Bulletin_101.pdf|101]]
|1997-12-09
|Cirqus Voltaire
|Disappearing Jet Bumper assembly not releasing
|Applies to the first 200 sample games
|-
|[[media:Bally_1997_Cirqus_Voltaire_Service_Bulletin_102.pdf|102]]
|1997-12-09
|Cirqus Voltaire
|Upgrade Kit
|Installation instructions for Upgrade Kit #A-22270
|-
|[[media:Bally_1997_Cirqus_Voltaire_Service_Bulletin_104.pdf|104]]
|1998-04-02
|Cirqus Voltaire
|Cirqus Voltaire Adjustment Sheet
|Adjustment Sheet Update
|-
|?
|1998
|Medieval Madness
|Wireform Adjustment
|Catapult wireform adjustment (description of problem is currently missing, but assumed to help address ball jam issues in catapult wireform)
|-
|?
|1997-05-12
|NBA Fastbreak
|Link Kit
|Installation instructions for the link kit
|-
|[[media:Bally_1998_The_Champion_Pub_Service_Bulletin_107.pdf|107]]
|1998-12-28
|Champion Pub
|Champion Pub arms breaking prematurely
|
|-

|}

===Documentation Errors===
* Schematic errors in Addams Family & Addams Family Gold Manuals for the [[#TAF & TAFG Extra Flipper Power Supply (A-15416)|Extra Flipper Power Supply Board (A-15416)]].
* WPC Schematic Manual 16-9473 to 16-9473-2: Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.
* In Black Rose game manual, the coil/flasher listings at the front of the manual and in the section at the back of the manual that details connections are incorrect. See: [[#Coil_Locks_On_or_Flash_Lamp_Blows_at_Power_On|Coil Locks On or Flash Lamp Blows at Power On]]
*WPC-95 game manual J128 typo.
[[File:WPC95VoltageTypo.jpg|left|thumb|300px|Corrected WPC-95 (all games) manual]] 
It appears that all WPC-95 game manuals contain a typo for connector J128, pins 5/6 and 8/9. These two pairs of pins are shown to be connected to 16VAC from the transformer secondary. They are in fact connected to 50VAC from the transformer secondary.
 
* In the Indiana Jones Operations Manual (July 1993), Page 2-19 shows a diagram of the ''A-17073 Ball Eject Assembly - Special''. It incorrectly lists item #2 "Mounting Bracket Assembly" as part number A-8268 and the diagram incorrectly pictures A-8268. The correct part number is A-8268-1, which is a similar part, but oriented differently.

==Technical Info==
At the heart of the WPC MPU is the Motorola 68B09EP microprocessor, running at 2Mhz. Note that the "E" suffix indicates externally clocked and is necessary to work in a WPC MPU. The "P" suffix merely indicates a "plastic" chip case. 6809 processors lacking the "E" suffix will '''not''' work in a WPC MPU.

The 68B09EP is a 2Mhz, 8-bit/16-bit CPU, with a 64KB address space. Bank switching is required to address more than 64KB. Bank switching is accomplished by the ASIC in WPC systems. The game ROM size varies from 128KB to 8MB, depending on the game. 8KB of battery backed RAM is available to the processor.

For more information, see [https://web.archive.org/web/20110122183733/http://www.oddchange.com/freewpc/manual/The-WPC-Hardware.html The FreeWPC Manual (Archive.org link)]
===Inside WPC Game Backboxes===
<center>
<gallery widths=300px heights=300px perrow=3 caption="Typical WPC-089, WPC-DCS, and WPC-95 backbox configurations">
File:Placeholder.jpg |<center>WPC-089 pre-FlipTronics (Funhouse)</center>
File:WPCFlipTronics1.jpg |<center>WPC-089 pre-DCS with FlipTronics 1 (Addams Family, note separate 50V power supply board)</center>
File:Wpc-dcs-backbox-demolition-man.jpg ‎|<center>WPC-089 with DCS (Demolition Man)</center>
File:WPC-DCS-Backbox.jpg ‎|<center>WPC-S with DCS (Theatre of Magic)</center>
File:WPC95BackboxAFM.jpg |<center>WPC-95 (Attack From Mars, Color DMD Installed)</center>
</gallery>
</center>

===WPC Parts List Lookup===
A really nice utility has been put together by Øyvind Møll, enabling lookup of WPC parts. The utility can be used to see which games used particular parts. The utility can be found [http://www.moll.no/pinball/parts/ here].

===WPC System Generations===
====WPC CPU====
[[File:WPC-089_MPU.jpg|200px|thumb|right|WPC-089 CPU, this one from Twilight Zone, with battery holder removed.]]
The WPC CPU was the cornerstone of the new WPC pinball system, introduced by Williams in 1990.

The board has the following features:
* Motorola 68B09E processor
* Switch matrix inputs
* 8k of CMOS battery-backed memory
* A single EPROM, sized from 128K (1 megabit, 27C128) to 1M (8 megabits, 27C080 / 27C801)
* Watchdog circuit and master reset
* Three digital I/O ports - general-purpose; display; auxiliary (labeled "display")
* WPC ASIC - an 84-pin PLCC that has decoding, watchdog, and real-time clock circuitry.

'''What Goes Wrong'''

'''Loose Chips''' - resets and strange behavior

The natural heating and cooling cycle, and vibration, in a pinball machines causes the socketed chips to slowly walk out of their sockets. This loosening can cause mysterious behavior and resets. Firmly pressing each socketed device - including the ASIC - and listening for a small click can solve many odd problems.

'''Battery Corrosion''' - rows of switches failing

When batteries reach old age, they always leak electrolyte. In WPC boards, this electrolyte drips onto the switch matrix circuits. There, it causes extensive corrosion. The corrosion will eat up traces under the green solder mask, creating a lumpy appearance. This corrosion is extremely destructive. It must be caught early, and gently washed with vinegar. Damaged components must be replaced, and damaged traces cleaned with a fiberglass brush and carefully tinned with a soldering iron. Battery corrosion can render a board unrepairable, or undesirable.

''' The Switch Matrix ''' - assorted switch problems

The WPC system, like many pinball machines, uses a switch matrix to read the switches. The matrix is 8 rows by 8 columns, and can read 64 switches with just 16 wires. Under the playfield, the wires snake between the lights, creating strings of rows and strings of columns. The lights are isolated with diodes.

The root cause of switch matrix problems on the WPC CPU is often a voltage short to the switch matrix. This can happen with residual charge from the solenoid or flasher supply, so the machine does not have to be on for damage to occur. One easy way to do this is to touch a coil lug while adjusting slingshot switches. The row detectors - the LM339s - are quite safe from everything but the 70V solenoid voltage, and will often survive that. The column drivers, however, are directly exposed to the wiring. So many shorts - from the GI; lamp matrix; flashers; or solenoid wiring can destroy the driver. A solenoid wiring short will often destroy the 74LS374 at location U14 ahead of the driver as well.

The symptom of a bad driver is a column short that does not go away when the playfield is disconnected. A bad driver may also be confused by neighboring columns, so switches may register twice.
 

[[File:TheCapacitorToNowhere.jpg|200px|thumb|left|This "missing" bypass capactor isn't missing at all.]] 
The WPC CPU is stuffed with a "bypass capactor" to the right of the ULN2803. Bypass capacitors filter high frequency noise from the 5VDC power at each integrated circuit (generally). This one...in some revisions of the PCB, isn't connected to anything on one side. It can safely be removed, or more likely, simply not be replaced when abating alkaline corrosion.
 

===== Early WPC-089 MPU Board as found in Bride of Pin*Bot =====
[[File:EarlyWPC-089MPU-PinBot.jpg ‎|200px|thumb|left|WPC-089 CPU, this one from Bride of Pin*Bot, with battery holder removed.]]
[[File:PinBotMPUBoardRev.jpg ‎|200px|thumb|right|Board Revision.]]
[[File:PinBotDateStamp.jpg ‎|200px|thumb|right|Board Date Stamp. August 7, 1990]] 
The MPU board pictured here is from a Bride of Pin*Bot. Note that J210 and C31 have been replaced.

Some differences between this early board revision and later production revisions:
*Upper right corner parts are quite different
*Mounting holes vs key-holes
*Some sort of "hack" just to the left of the 68B09EP and game ROM.
*Different brand of bypass capacitors (B).
 

===== WPC-089 Signal Map (pinouts) =====
[[File:WPC89 CPU compnt-side ZAZ FEB2017-10.jpg|200px|thumb|left|Component Side.]][[File:WPC89 CPU solder-side ZAZ FEB2017.PNG|200px|thumb|right|Solder Side.]] 
The two diagrams (left and right) show the signal pinout for the entire WPC-089 MPU, both front and back side view. ''Images provided by Sascha Voskuil.''
 

===== WPC-089 Bare PCB Images =====
The following images are provided for reference.

<center>
<gallery widths=250px heights=200px perrow=4 caption="WPC-089 OEM MPU PCB Traces">
File:WPC-089-U1.JPG|<center>U1</center>
File:WPC-089-U2.JPG|<center>U2</center>
File:WPC-089-U3.JPG|<center>U3</center>
File:WPC-089-U4.JPG|<center>U4</center>
File:WPC-089-U5.JPG|<center>U5</center>
File:WPC-089-U6.JPG|<center>U6</center>
File:WPC-089-U7.JPG|<center>U7</center>
File:WPC-089-U8.JPG|<center>U8</center>
File:WPC-089-U9.jpg|<center>U9</center>
File:WPC-089-U11.JPG|<center>U11</center>
File:WPC-089-U12.JPG|<center>U12</center>
File:WPC-089-U13.JPG|<center>U13</center>
File:WPC-089-U14.JPG|<center>U14</center>
File:WPC-089-U15.JPG|<center>U15</center>
File:WPC-089-U16.JPG|<center>U16</center>
File:WPC-089-U17.JPG|<center>U17</center>
File:WPC-089-U18.JPG|<center>U18</center>
File:WPC-089-U19.JPG|<center>U19</center>
File:WPC-089-U20.JPG|<center>U20</center>
File:WPC-089-U21.JPG|<center>U21</center>
</gallery>
</center>

====WPC-S CPU====
[[File:WPC-SCPU.jpg|300px|thumb|left|WPC-S CPU]]
[[File:WPC-SMPU.jpg|400px|thumb|right|WPC-S CPU with daughter card installed. Battery holder replaced with coin cell battery.]]
The WPC-S CPU is the second generation of WPC CPU board. The designer switched to a remote battery holder, located on a daughter board that clips to posts on the lower half of the board. This approach mostly eliminated the PCB damage caused by battery leakage. The next version of the board, the WPC-95 CPU board, switched to a plastic battery holder that doesn't provide quite as much alkaline corrosion protection to the board.
The board also has different switch matrix connectors than WPC and WPC-95.

The digital I/O connectors remain unchanged from the WPC CPU.

The most significant difference was the introduction of the security PIC. This devices contains a serial number and a handshake mechanism. The serial number is displayed at startup, and allowed the manufacturer to identify the dealer who sold a machine into a particular region. This approach was necessary when substantial price differences were common across Europe, to prevent grey imports.

To prevent simple removal of the PIC, the device also controlled the switch matrix, and would not operate without a correct machine code from the WPC CPU. Therefore, there is one PIC for each machine. An incorrect or defective chip will result in a "G13 error" or "U22 error" at startup.

When buying a used WPC-S MPU, the battery holder is often missing. If connecting a battery pack, a Molex housing and 2 crimp contacts is needed. The part number for the 5 pin housing is 50-57-9405 (Digikey WM2903-ND). The crimp contacts are part number 16-02-1125 (WM2554-ND).
 

====WPC-95 CPU====
[[File:Wpc95-cpu-rev1-MrVT.jpg|300px|thumb|left|WPC-95 CPU Board, part number A-20119. Note that U27 is a 74LS08 in this revision. Image courtesy of PinSider "DumbAss".]]
[[File:Wpc95-cpu-rev3-MrVT-Cropped.jpg|300px|thumb|right|WPC-95 CPU Board, part number A-21377. Note that U27 is a 74LS02 in this revision. Image courtesy of PinSider "DumbAss".]] 
The WPC-95 CPU is the third generation of the WPC CPU design. It includes the security PIC added in the WPC-S system, and returns to an on-board battery holder. The new battery holder has a large plastic shell, designed to shield the PCB from any battery leakage. The pinout of the switch matrix connectors changed again from WPC-S.

Note that these pictures show MPUs with the battery holders removed and with the dual .100 headers replaced with "box" headers.
 

===== WPC-95 CPU Factory Modification =====
[[File:WPC95FactoryMod.png|300px|thumb|left|WPC-95 CPU Board factory mod. Drawing by Sascha Voskuil.]] 
CPUs manufactured for Jack*Bot and Congo sample games before 12-15-95 have a factory modification that includes one cut, an additional diode, and an additional resistor. Williams [http://www.planetarypinball.com/mm5/Williams/tech/sb86.html Service Bulletin 86] details the reason for the mod, premature loss of backup battery voltage.
 

===== The WPC ASIC =====
[[File:WMS-ASICVersions.jpg|300px|thumb|left|An original ASIC (left) and a reproduction ASIC (right).]] 
The ASIC (application specific integrated circuit) lies at the heart of all WPC systems. The same ASIC was used across WPC, WPC-S, and WPC-95.

The ASIC combines much of the digital logic required by prior WMS System 3-11 game systems into a single chip. This workhorse chip rarely fails. The correct tool must be used to remove the ASIC as both the chip and the chip carrier can be damaged by using the incorrect tools.

The -01 version shown at left was reproduced by Mr. Pinball Australia in 1997.
 

===WPC Power/Driver Board Generations===
====WPC-89 Power/Driver Board====
The WPC power-driver board converts AC power from the transformer; drives the solenoids; drives the lamp matrix; drives the GI lamps; and detects flipper switch operation in non-FlipTronics machines.

There are three known variants of the WPC-89 driver board: A-12697-1, A-12697-3, and A-12697-4. The A-12697-1 (aka "-1") board is forward-compatible with all WPC-89 & WPC-S games. Because later board versions A-12697-3 ("-3") and A-12697-4 ("-4") boards had components removed due to the introduction of the fliptronics boards, they are not backwards compatible with non-fliptronics games (unless retrofitted with the missing components for older flipper operation).

The power-driver board includes the following functions:
[[File:WPC089 power summary.png|240px|thumb|left|Summary schematic of WPC '89 Power Driver board showing test LED's and test points. A PDF of this image can be viewed [[Media:WPC089 power summary.pdf|here]]]]
[[File:WPC_Power_-Driver_Board.jpg|200px|thumb|right|WPC Power-Driver board with Flipper Relay, or the -1 version.]]
[[File:WPCPowerDriverBoardWithoutFlipperRelay.jpg|200px|thumb|right|WPC Power-Driver board without Flipper Relay, or the -3 version.]] 

*AC rectification and smoothing for 70VDC solenoid voltage
*AC rectification and smoothing for 20VDC flasher voltage
*AC rectification and smoothing for 18VDC lamp matrix voltage
*AC rectification and smoothing for unregulated 12V supply
*AC rectification and smoothing for 5VDC flasher voltage
*Regulated 12V supply
*Regulated 5V supply
*6.3VAC supply for GI circuits
*Power control for high power solenoids (drives 1 - 8, Q64 through Q82), with clamping diode connected to 50VDC
*Power control for low power solenoids (drives 9 - 16, Q44 through Q58, with clamping diode connected to 50VDC
*Power control for flashers (drives 17 - 20, Q36 through Q42), without a clamping diode at all
*Power control for "special" solenoids (drives 21 - 28, Q20 through Q34), with clamping diode that must be connected to the power source driving the device. In practice, this is always the 50VDC power source.
*Power control for lamp matrix
*Power control for pre-FlipTronics flippers (not on all boards)
*Sense optos for pre-FlipTronics flippers (not on all boards)
*Power control for 5 6.3VAC GI channels using four-sector triacs
*Zero crossing sense for AC line in
*Logic interface to WPC CPU
 

=====Retrofit a later driver board to become a -1 version board=====
[[File:Dash-1Conversion.jpg|300px|thumb|right|A -3 WPC Power/Driver board retrofitted with the minimum parts required to add -1 functionality. Note: R210 and R211 still need to be populated on this board.]] 
The newer generation -3 and -4 boards can be converted to -1 board configuration by populating the following components:
*D39 - 1N4004
*U7/U8 - 4N25 (or 4N35)
*R210/R211 - 3.3K/5W Resistor
*RLY1 - 6VDC 4PDT Relay
*J110 - 9-pin .156 header
*Q99 - 2N5401 transistor
*R208 - 270 ohm 1/4W resistor
*R209 - 4.7K ohm 1/4W resistor

In the image at right, some components remain unpopulated. Those components are part of the line level voltage circuitry that drives LED2 and LED3. The line level voltage circuitry does not work very well and can not be relied upon. Hence, there is no reason to populate those components. 

[[File:WPCPowerDriver-1-3Differences.jpg|300px|thumb|left|A graphical indication of part differences between the -1 and -3 WPC Power/Driver board configurations. Illustration provided with permission of Sascha Voskuil aka Zaza.]] 
The diagram at left depicts the differences between the -1 and -3 WPC Power/Driver board configurations.
 

=====WPC Power/Driver Board Layout Errors=====
======C9 Connection Error======
[[File:WPCPowerDriverBoardC9Correction.jpg|300px|thumb|left|WPC Power/Driver board with C9 connection corrected.]]
[[File:WPCPowerDriverBoardC9CorrectionSchematic.jpg|300px|thumb|right|Image of WPC Power/Driver board schematic, showing LM323K 5VDC regulator and C9.]] 
At the time that this PCB was laid out and manufactured, a small tantalum capacitor, located at C9, was connected to the wrong side of the LM323K 5VDC regulator. While it should have been connected to Vin, it was in fact connected to Vout. The picture at left shows a method to correct the board so that it matches the schematics, also shown at left. In this picture, an additional "tab" was added to the top bolt of the regulator and soldered to ground, creating a redundant path to ground for the regulator.

Note that while the schematics show this capacitor as .33µF, it is listed as 2.2µF in each game's parts listing, matching the capacitor that is actually installed.

This change isn't generally considered necessary and not thought to be a significant contributor to game resets. The original purpose of the cap was to filter high frequency noise. According to the LM323K datasheet, a 1 to 2µF tantalum capacitor should be added to the input of the LM323K if the regulator is more than 4" away from the main filter capacitor. The regulator is just inside of 4" from the 15,000µF filter capacitor at C5. As it sits on Vout, it causes no harm, but does no good either.
 

======J122/J124, pin 1 Connected to Board Ground======
[[File:WPCPowerDriverBoardLayoutError.jpg|300px|thumb|left|Two power/driver boards showing the factory corrected trace routing (bottom) and a later version of the board with the correction incorporated into the PCB mask (top).]] 
Some revisions of the WPC power/driver board, were manufactured with J122 and J124, pin 1, connected to board ground. This would cause whatever is connected to those connector positions, to be turned on constantly. For the game Twilight Zone, this would result in the left mini-playfield magnet being powered constantly. The picture at left shows a factory modification to the power/driver board to rectify the problem.
 

====WPC-95 Power/Driver Board====

The WPC-95 Power/Driver board performs all of the same functions as it's WPC predecessor, and also integrates flipper power circuits into the design, eliminating the need for the FlipTronics board present in WPC FlipTronics I & II games as well as WPC-S games. The bridge rectifiers are replaced by ganged 6A2 diodes and the filter capacitors were spec'd down from 15,000µF to 10,000µF. While the WPC P/D board supported brightness control of 5 general illumination circuits, the WPC-95 P/D board can control brightness of only 3 general illumination circuits. The two remaining GI circuits are used for backbox illumination.
[[File:WPC095 power summary.png|300px|thumb|left|Summary schematic of WPC '95 Power Driver board showing test LED's and test points. A PDF of this image can be viewed [[Media:WPC095 power summary.pdf|here]]]]
[[File:WPC-95PowerDriverBoard.jpg|300px|thumb|right|WPC-95 Power/Driver board. This is the later model, with zero ohm jumpers installed in the GI circuit, lower left.]]
 

===WPC Alphanumeric Display Driver Board===
The Alphanumeric display driver board was used in Funhouse, Harley Davidson, and The Machine: Bride of Pin*bot. The board still contains the high voltage handling ICs, UDN6118 and UDN7180. It also has its own high voltage generation circuit that is a carryover from earlier Williams high voltage display circuits.
[[Image:WPCAlphaNumericDisplayDriverFront.jpg ‎|300px|thumb|left|WPC Alphanumeric Display]]
[[Image:WPCAlphaNumericDisplayDriverRear.jpg ‎|300px|thumb|left|WMS A-12739-1 WPC Alphanumeric Display Driver PCB]]
 

===WPC Dot Matrix Controller board===

[[Image:WPC DMD Controller.jpg|300px|thumb|left|WPC DMD Controller board]]
The WPC DMD display and DMD controllers are common features in Williams 1990's era pinball machines. The display is a high-voltage plasma system that has scanning electronics built in. The WPC dot matrix controller board, or WPC-95 AV (Audio/Video) board in later machines, provides the power for operation, and maintains the display dot images in its memory. The CPU loads these pages ahead of time, then instructs the display controller to "flip" the images onto the screen.

Note that sometimes U12 is stuffed on this board and sometimes it is not. There is no functional difference whether U12 is stuffed or not.

Clive at the Coin-Op Cauldron has written an excellent article detailing some of the nitty gritty of the DMD controller. The article can be found [http://coinopcauldron.com/dotarticle.html here]. 

===WPC Sound Boards===
====WPC pre-DCS Sound Board====
[[Image:WPC Sound Board.jpg|300px|thumb|left|WPC pre-DCS Sound Board, sound ROMs removed]]
Pre-DCS Sound Board issues are discussed [https://www.pinwiki.com/wiki/index.php/Williams_WPC#Pre-DCS_Sound_Board_Issues here]. 
The pre-DCS sound board uses a single LM1875 amp and can accommodate up to 3 sound ROMs. With a single "sound lane" and amp, stereo sound is not possible. The three speakers are connected in series, each of them attempting to accentuate different bands of the audio spectrum. A broken wire to any of the three speakers will result in no sound at all.
 

====WPC DCS Sound Board====

[[File:WPC DCS Sound Board.jpg|300px|thumb|left|The WPC DCS Sound Board]]
DCS Sound Board issues are discussed [https://www.pinwiki.com/wiki/index.php/Williams_WPC#DCS_Sound_Board_Issues here]. 
With Indiana Jones: The Pinball Adventure, Williams introduced the DCS sound system. Its DSP architecture was a significant improvement on earlier systems, and it allowed Williams to use recorded music from EPROM rather than synthesizer music. The board also introduced dual amplifiers and an electronic crossover. DCS allowed Williams to use compressed sound samples, significantly improving the sound quality of the games.

The board dropped the microprocessor controlled synthesizer chip and sound bite system of earlier WPC machines, and replaced them with the still in production Analog Devices ADSP-2105 DSP. For its time, this was an extremely fast device (40MHz), and is capable of providing all of the sound processing needed in a WPC pinball machine. The ADSP-2115 can also be used as a replacement for the 2105. It adds a second serial port which is not used in WMS pinballs. Williams also upgraded the chip amp. The new chip amp operates at a lower voltage, and forced a corresponding change in the transformer voltage (12VAC + 12VAC). Therefore, DCS machines have different transformer winding to previous WPC machines. The system has an electronic crossover, separating high frequencies to the backbox and low frequencies to the cabinet.

The card connects to the WPC CPU through the I/O port. It shares the port with the Fliptronics board and the display board.
 

'''What's on the Board?'''

The DCS sound board has the following subsystems:

* Rectifier and fused power supply for +/-16VDC amplifier power [check - WPC was 35V?]
* Dual-channel power amplifier with electronic crossover
* DSP-based sound synthesizer
* One EPROM for DSP code storage
* Other EPROMS for sound storage
* High-speed program memory for the DSP
* Mailbox interface for WPC-CPU

On power-up, the board runs a diagnostic and sounds a bong. It does this without any help from the WPC CPU. If there is no bong, the board has a problem.

'''What Goes Wrong'''

The smoothing capacitors C20 and C21 are often at the end of their useful lives. The chip amp, like the Honey Badger, really doesn't care, and will accomodate capacitor variance. However, replacing them will make even the pre-DCS sound much richer.

The coupling capacitors at C32 and C41 can fail.
 

====WPC-95 AV Board====
[[File:Wpc95AV.jpg|300px|thumb|right|WPC-95 AV Board]]
WPC-95 AV Board issues are discussed [https://www.pinwiki.com/wiki/index.php/Williams_WPC#WPC-95_A/V_Board_Sound_Issues here]. 
The WPC-95 AV board integrated the sound and video system into a single board, siginifcantly reducing power and space.

The board has the following major subsystems

'''ASIC'''
The ASIC is a 120-pin quad flatpack device. It incorporates the following functions:
*Interface registers to CPU
*Memory control and display output logic for the diaplay subsystem
*Memory interface for the AD2105 DSP

The ASIC has a tendency to fail in such a way that the sound disappears. New ASICs are available, but replacing them requires skill with surface mount devices.

'''Audio DSP'''
The audio susbsystem uses the same part as the DCS sound board the Analog Devices DSP part ADSP-2105 and an AD1851 DAC. For its time, this was an extremely fast device (40MHz), and is capable of providing all of the sound processing needed in a WPC pinball machine. The AD1851N in DIP package was discontinued 2010 but the DSP is still available at Digikey and many other stores (ADSP-2105BPZ-80 ).

Location: lower center of board

'''Serial Port'''
The serial port is rarely populated. Its uses include: machine debugging; machine linking ([[NBA Fastbreak]]); ticket printers

Location: lower left of board

[[File:AVBoardFront.jpg|300px|thumb|left|WPC-95 AV Board Trace Reference (front)]]
[[File:AVBoardBack.jpg|300px|thumb|right|WPC-95 AV Board Trace Reference (back)]]
'''Audio Amplifier'''
The audio amplifier is a dual-channel TDA 2030A operating at X volts. The system has an electronic crossover, separating high frequencies to the backboox and low frequencies to the cabinet.

Location: lower right of board

'''DMD Power'''
The DMD nominally requires 62, -100 and -112VDC to operate. The board uses a temperature-compensated design to supply these voltages.The -112VDC line is built as a 12V offset from the -100VDC line.

Location: upper right of board.
 

===WPC FlipTronics I & II Boards===
Beginning with The Addams Family, Williams implemented the FlipTronics flipper power and switch sensing system. The Addams Family and The Addams Family Gold were the only two games which used the FlipTronics I board. Subsequent games until the WPC-95 board set debuted used the FlipTronics II board. The three FlipTronics II board revisions (A-15472, A-15072-1, and A-15472-1) are interchangeable. The WPC-95 board set integrated the flipper electronics into the driver board.

[[File:WPC_Fliptronics_I_Board.JPG|300px|thumb|left|WPC Fliptronics I Board]]
[[File:WPC Fliptronics II.jpg|300px|thumb|right|WPC Fliptronics II Board]] 
Prior to the FlipTronics system, flipper circuit design had essentially been the same simple circuit. This circuit consisted of power to two flipper coil windings (the "power stroke" and "hold" windings). When the flipper cabinet switch was closed, the power winding and hold winding were both energized. As the flipper plunger was pulled in, the flipper EOS switch opened, interrupting power to the "power stroke" winding, leaving only the "hold winding" energized to hold the flipper in the up position. Flipper coil systems were designed this way so a flipper could be energized indefinitely (in theory). A failed EOS switch could result in weak flipper performance (poor EOS switch conduction) or result in burned flipper coils (EOS switch that never opens). 

[[File:FlipTronicsLayout.png|300px|thumb|left|FlipTronics II Component Identification. Image courtesy of PinSider j_m_.]] 

The FlipTronics system ended reliance on properly operating EOS switches. While FlipTronics systems still have EOS switches, they generally are not used to control power to the coil windings. The EOS switch provides feedback to the MPU that the flipper has completed a stroke. A failed EOS switch will not cause damage to either the coil or to the switch circuitry. If the MPU doesn't receive feedback that the flipper has completed a full stroke within a specific time (milliseconds), the "power stroke" winding power will still be interrupted.

There is a special case where a properly operating EOS switch comes into play. The EOS switch on FlipTronics games helps to keep the flipper bat in the up position when a fast moving pinball strikes the flipper. When the ball strikes the flipper, moving it toward the "at rest" position, a properly operating EOS switch will open. The FlipTronics board will then provide a path to ground for the "power stroke" winding until the flipper completes the upward stroke, closing the EOS switch again. Games with broken or malfunctioning EOS switch(es) may allow the flipper bat to drop all the way to the "at rest" position when struck by a rapidly moving ball, with possible loss of ball, and a great deal of "what the @#$% just happened".
 

'''FlipTronics game flipper operation: '''
#Flipper power is always present at the flipper coil lugs. For the flipper to actuate, that coil power needs to find a path to ground.
#The FlipTronics board switch sensing circuitry recognizes closure of a flipper cabinet switch.
#The FlipTronics board communicates closure of the flipper cabinet switch to the MPU.
#The MPU commands the FlipTronics board to provide ground for the "power stroke" winding of the flipper coil (via a circuit passing through a 2N5401, TIP-102, and TIP-36C). This process is similar to how high powered coils are controlled by the power driver board.
#A few milli-seconds later (thousandths of a second), the MPU commands the FlipTronics board to interrupt the ground path for the power stroke winding and to provide ground for the hold winding portion of the coil (via a circuit passing through a 2N5401 and a TIP-102).
#The FlipTronics board switch sensing circuitry recognizes close of the flipper EOS switch, and communicates that switch closure to the MPU. Again, this switch closure isn't used to control power to the flipper coil windings. It's merely information.
#When the player releases the cabinet flipper switch, the FlipTronics board again senses that open switch, communicates the change in state to the MPU which then commands the FlipTronics board to interrupt ground to the hold winding also, and the flipper returns to it's at rest position.

WPC-95 games use the exact same methods. However, the WPC-95 board set integrates the capabilities of the FlipTronics board into the power driver board.

The FlipTronics II board also rectifies AC voltage sourced from the game transformer, and relayed to it from the Power/Driver board to create the 70VDC flipper power (the FlipTronics I board relies an an "extra flipper power supply" to rectify the flipper voltage). A FlipTronics board can sense 8 switches, and control up to four flipper power and hold windings. In some games, spare flipper cabinet switches, EOS switches, and coil drive circuits are used for other game features.

Note that sometimes C2 is installed on this board and sometimes it is not. The board pictured does not have C2 installed. Since C2 is a 100µF/100V capacitor, it can't be doing too much AC smoothing of the full wave rectified flipper power. Some RGP discussions indicate that C2 may have been designed in originally to reduce EMI (electro-magnetic interference) from the board. Installing C2 will have a negligible affect on flipper power. Some report that installing C2 fixes a "jittery gate" symptom on BSD's "mist" assembly.

More information about bench testing FlipTronics board is available [[Leon_Borre_WPC_Fliptronics_board_repair | here]].
 

======Fliptronics II in The Addams Family======

The Addams Family was designed to use the Fliptronics 1 board system. This consists of a Fliptronics 1 board and a separate external power supply. This external power supply is connected to the upper flippers and the three magnets under the playfield. The lower flippers are connected to the 50V DC power supply in the Power Driver Board.

While the Williams Fliptronics II board could physically be installed in The Addams Family and is plug compatible, it is not advisable to do so. The power supply in the Fliptronics II board will not be connected (without running extra wiring). And the Fliptronics II board does not have the 4-wire ground connector (J801 on the Fliptronics I board). The only ground connection is via 2 wires on J904 (J804 on the Fliptronics I board) and that is intended as the digital ground for +5 and +12.

The only way to properly use the Williams Fliptronics II board in The Addams Family is to run new wiring from the +50V AC Power Driver Board supply to J901 and connect the power supply for the flippers to J907. Or run proper ground wires between the Williams Fliptronics II board to the flipper power supply board.

Most aftermarket Fliptronics board have the ground connector at J801 and can be used in The Addams Family without modifications. However, those aftermarket boards will act like Fliptronics 1 boards and will require the flipper power supply to remain in the game.

===Miscellaneous WPC Boards===

====WPC 7 Opto Board (A-14977, A-15576, A-15595)====

The 7 Opto Board is used in the following games:
*Attack from Mars
*Cirqus Voltaire
*Demolition Man
*Flintstones
*Jackbot
*Judge Dredd
*Johnny Mnemonic
*NBA Fastbreak
*Road Show
*The Addams Family
*The Addams Family Gold
*Theatre of Magic
*Tales of the Arabian Nights
*World Cup Soccer
*White Water
[[File:7OptoBoard.jpg|300px|thumb|left|Example WPC 7 Opto Board, as found in AFM and many other WPC games.]]
[[File:A-155767-OptoBoard.jpg|300px|thumb|right|7 Opto Board Schematics.]]
The connector on the lower left (as pictured) provides the power for seven IR emitters. The emitters are powered from the 12V supply through a 260 ohm resistor (the large blue resistors adjacent to the connector). Williams runs the opto emitters at about 40mA, which results in the resistors becoming hot. The opto boards are often darkened by the heat, as this one is.

The connector on the upper left carries the signals for the photo-transistors. The photo-transistor collector connects to 12V, and its emitter connects to ground through two 2KOhm resistors connected in series. When the transistor is illuminated by the emitter, it passes more current through the resistors, raising the input voltage on the LM339. The other pin on the LM339 is set to about 2.8V buy a 100K/22K voltage divider. Therefore, when the voltage at the junction of the two 2K resistors and the LM339 input is above 2.8V, the switch will read as closed. This happens at 1.4mA.

The two left side connectors can be used for optical trough switches. The connector on the right hand side provides the the row/column switch matrix interface to the MPU. 

=====WPC 7 Opto Board Problems=====
'''What Goes Wrong?'''

The resistor discoloration is cosmetic, and rarely causes problems. The biggest problem for these boards is switch matrix shorts. If any of the power lines hits the switch matrix, it can easily destroy the LM339 and possibly its output diode. This issue will manifest as a ground short on one or more rows. It can be tested by removing the switch matrix connector. If the problem goes away, the associated LM339 and possibly its diode need to be replaced.

If the short was from the 70V supply, multiple LM339s may be damaged.

Replacing LM339s on these boards needs to be done carefully, as it is easy to lift traces and pull the through-hole plating. Always socket replaced ICs.

====WPC 10 Opto Board (A-15430, A-18159, A-20246) ====
[[File:WMS 10 Opto.jpg|300px|thumb|left|Example WPC 10 Opto Board.]]
[[File:A15430-10OptoBoard.jpg|300px|thumb|right|Example WPC 10 Opto Board schematics]] 
The 10 opto board was used in Bram Stoker's Dracula, Dr. Who, Indiana Jones, Pinball Circus, Popeye, Cactus Canyon, Corvette, Monster Bash, Medieval Madness, Revenge From Mars, SafeCracker, SWE1, Shadow, Congo, Indianapolis 500, and World Cup Soccer.

The connector on the upper left carries the power for seven of the IR emitters. The emitters are powered from the +12V supply through a 260 ohm resistor (the large blue resistors adjacent to the connector). Williams runs the opto emitters at about 40mA, which results in the resistors becoming hot. The opto boards are often darkened by the heat, as can be viewed in the adjacent picture.

The connector on the lower left carries the signals for the photo-transistors. The photo-transistor collector connects to +12V, and its emitter connects to ground through two 2KOhm resistors connected in series. When the transistor is illuminated by the emitter, it passes more current through the resistors, raising the input voltage on the LM339. The other pin on the LM339 is set to about 2.8V by a 100K/22K voltage divider. Therefore, when the voltage at the junction of the two 2K resistors and the LM339 input is above 2.8V, the switch will read as closed. This happens at 1.4mA.

These two connectors can be used for optical switch troughs. The three connectors on the right hand side each carry signals for one transmitter/receiver pair. These connections are often used for ramp entrances, and sometimes the pair is mounted on a single bracket.

The connector on the bottom provides the the row/column switch matrix interface to the MPU. 

=====WPC 10 Opto Board Problems=====
'''What Goes Wrong?'''
[[File:10OptoBoardCorrosion.jpg|300px|thumb|right|The leaky capacitor removed and shown in this picture, spewed enough electrolyte to completely eat through the power trace, causing the board fail.]]‎
The resistor discoloration is cosmetic, and rarely causes problems. The biggest problem for these boards is switch matrix shorts. If any of the power lines hits the switch matrix, it can easily destroy the LM339 and possibly its output diode. This issue will manifest as a ground short on one or more rows. It can be tested by removing the switch matrix connector. If the problem goes away, the associated LM339 and possibly its diode need to be replaced.

If the short was from the 70V supply, multiple LM339s may be damaged.

Other symptoms of failed LM339's can include:
* Intermittent ground shorts on one or more switch matrix rows. Sometimes this can be mistaken for a connector issue since the ground short warning message and row(s) of closed switches in the edge switch test may appear and disappear at random.
* Sometimes the switch edge test can show one or multiple opto switches flickering open and closed. This can sometimes be mistaken for a connector or individual opto issue, as it can come and go at random.
* In switch edge test, one opto switch can activate an entire row of opto switches, but might not actually show the ground short warning.

Replacing LM339s on these boards needs to be done carefully, as it is easy to lift traces and pull the through-hole plating. Always socket replaced ICs.

Another common issue is the 100uf/35V electrolytic capacitor at C1 will leak corrosive liquid that eats through the traces under it. This interrupts the power supply.

====WPC Twilight Zone Custom 10-Opto Board (A-16807)====
[[File:TZ10OptoBoard.jpg|300px|thumb|left|Twilight Zone specific 10 Opto Board.]]
[[File:10OptoBoardTZ.jpg|300px|thumb|right|Twilight Zone specific 10 Opto Board schematics]] 
This 10-Opto board appeared only in Twilight Zone. As can be seen, it differs in pinout (at the very least) from the more ubiquitous 10-Opto board above.

'''What Goes Wrong?'''

See "[http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#WPC_10_Opto_Board_.28A-15430.2C_A-18159.2C_A-20246.29 WPC 10 Opto Board (A-15430, A-18159, A-20246)]", above.
 

====WPC 16 Opto Board (A-16998, A-17223)====
[[File:16OptoBoard.jpg|300px|thumb|left|WPC 16 opto boards, both versions]]
[[File:16OptoBoardSchematics.jpg|300px|thumb|right|WPC 16 opto board schematics]] 
This board is used in at least Star Trek: The Next Generation, Junkyard, and Champions Pub. Note the two different "versions". The bracket on one side is believed to be part number 5768-13739-00 while the bracket on the other side is believed to be part number 5768-13739-01. The boards are identical in layout and components. The only difference is bracket mounting, some silk screening, and one version has holes in the PCB which are not used.
 

====WPC Twilight Zone Clock Boards (A-16219, A-16220)====
[[File:TZClockBoardMinute.jpg |300px|thumb|left|A-16220 Twilight Zone specific Clock Mechanism "Minute Hand" Side of paired Boards.]]
[[File:TZClockBoardHour.jpg ‎|300px|thumb|right|A-16219 Twilight Zone specific Clock Mechanism "Hour Hand" Side of paired Boards]] 
The Twilight Zone playfield clock toy employs an ingenious method of driving and detecting the minute and hour hand positions. Two boards are sandwiched together, one with four optos to detect the minute hand and one with four optos to detect the motor rotation position and therefore the hour hand.

This board has been problematic over the years as the original incandescent lamps burned very hot, increasing the temperature inside the clock casing enough to damage the circuit board components. Numerous aftermarket clock boards have been offered with varying degrees of success.
 

[[File:TZClockBoardLampSchematic.jpg ‎|300px|thumb|left|Twilight Zone Clock Lamp Schematic Snippet]] 
Note that the schematic contained in the manual for the clock board lamps shows four diodes (D1-D4). During production, those diodes were swapped with "zero ohm jumpers". The reason for this change was that Williams originally intended the four lamps to be part of the lamp matrix and therefore individually controllable and also therefore requiring an associated lamp matrix isolation diode. When Williams decided to drive these four lamps via general illumination power, those diodes were replaced with "zero ohm jumpers" since diodes would have reduced lamp intensity and the lamps no longer required isolation in a lamp matrix.
 

====8 High Power PCB Assembly (A-16116)====
[[Image:A16116-8-HighPowerPCBAssembly.jpg|300px|thumb|left|A 8 High Power PCB Driver Board as used in ''Twilight Zone'']] 
The 8 High Power PCB was used only on Twilight Zone. It has the capacity to drive 8 high power coils if fully populated. Instead, it drives 5 high power coils as populated for Twilight Zone. This simple board is merely an extension of the power/driver board solenoid drive circuitry designed to accommodate the extra coils incorporated into the Twilight Zone design. It replicates the power/driver board circuitry of the TIP-36c transistors.
 

====Auxiliary 8-Driver Board (A-16100)====
[[Image:8 driver board.JPG|300px|thumb|left|An example 8-Driver board]]
[[Image:A-16100-8DriverBoard.jpg|300px|thumb|right|A-16100 Schematics]] 
The auxiliary 8-driver board sits in the top right of the backbox in a handful of WPC machines. The board is designed to run flashers, low-power solenoids, and perhaps motors.

The connector labeling is tricky as the 8-Driver board is controlled by a ribbon cable that is connected to the "Display" connector on the WPC CPU board (J204). The "Display" label is a historical artifact and refers to the alphanumeric display used in Funhouse. 

The board has 8 outputs, driven by TIP-102 transistors with a 2N4403 pre-driver, similar to the WPC power/driver board (which uses a 2N5401 as a pre-driver). The board is used in the following games:
*Demolition Man
*Indiana Jones
*Road Show
*Star Trek: The Next Generation
*Twilight Zone

The board circuitry can be jumpered to add one or two more columns to the switch matrix. This makes the board more flexible but also may require different jumpers to use the board in different games (i.e. the boards are not completely interchangeable between games "as is").

Jumpers to be installed for Demolition Man and Roadshow should be...
*PW1, PW3, PW5

Jumpers to be installed for Twilight Zone, Star Trek: The Next Generation, and Indiana Jones should be...
*SW2, SW4, SW6

Indiana Jones, Star Trek: The Next Generation and Twilight Zone use Q12 via the J5-1 connection to add this column. Although Twilight Zone adds the column, the column isn't displayed during switch test (T.1). The column is used to read the 8 optos in the clock mechanism.

The board can be jumpered to respond to memory mapped I/O at addresses 3FEB, 3FED, 3FED, 3FEE, and 3FEF via jumpers W1 through W5. In practice, this feature is never utilized as jumper W4 (3FEB) is always in and jumpers W1, W2, W3, and W5 are always out.

=====Auxiliary 8-Driver Board Problems=====
What Goes Wrong? 
This is a pretty simple board. Generally, the problem is going to be a blown transistor, or rarely, a failed 74ALS576 latch.

A problem which may occur are locked-on coils or flashers. This can be caused by the ribbon cable not being firmly seated. This can happen during the game or in attract mode and is caused by floating data line signals to the 8 Driver Board. A remedy has been found to solve this problem. This involves soldering a 10K resistor from the CLK to 5V and a resistor array 8x10K to pull down all data lines to GND. More information about this modification can be found under the [[Star_Trek:_The_Next_Generation#Diode_.22Tie_Back.22_missing_causes_8-Driver_Board_transistor_to_fail|"Diode Tie Back Missing Causes 8-Driver Board Transistor to Fail" section on the Star Trek: The Next Generation page]]

[[Image:STTNGDiodeTieBackAtCoilPower.jpg|300px|thumb|left|Diode tie-back at the single drop target assembly. Note the small purple/green wire soldered to the target reset coil's power side (two larger gauge purple/green wires).]] 
Another thing to watch for is a "diode tieback" connection to the board for games like Star Trek: The Next Generation. Without this "diode tieback", transistors on the 8-Driver board WILL be damaged. The diode tie-back wire is purple/green and connects from the coil power side of one of the drop target assembly coil lugs to J4 pin 1 on the 8-Driver board. If the solder connection at the coil lug is solid, suspect the wire connection at the IDC connector. Repinning this connection with good a quality crimp-on TriFurcon pin is advised.
 

====Sound Overlay Board (A-13502)====
This board acted as a power supply for a small subset of Funhouse and Dr. Dude games during the transition from System 11 to WPC in cases where the WPC boardset still included the [[Williams_System_9_-_11#Sound_Boards|System 11 D-11581 sound board]].
[[File:Placeholder.jpg|300px|thumb|left|Sound Overlay Board (A-13502)]] 

====Attack from Mars "Strobe" Board (A-20669)====
[[Image:AFMStrobeBoard.jpg|300px|thumb|left|A-20669 Attack From Mars Strobe Board]] 
The strobe board at left is unique to Attack from Mars. Williams used underrated 100µF/100V non-polarized caps on the board that often fail with the telltale "bulge" at one end. The "transformer" on the board (blue rectangular box, lower/right in the picture) has very fine legs which can break due to vibration at the back of the playfield.

Excellent repair information for this board can be found [http://www.iobium.com/fixing_the_afm_strobe_board.htm here] and a possible replacement for the overloaded non-polarized capacitors [http://kcpins.com/archives/63 here].

Note: An annotated .pdf of the schematics can be found [https://www.pinwiki.com/wiki/images/8/8f/STROBE.pdf here].
 

====Trough Opto Boards====
When WIlliams moved to the gravity trough, they also switched to optical switches to detect the ball. The trough is covered by a Williams patent.

There are two generations.

[[File:WMS A-17982 WPC Trough Transmitter.JPG|thumb|300px|left|WMS A-17982 Trough Transmitter Board - First Generation]] 
[[File:WMS A-17981 WPC Trough Receiver.JPG|thumb|300px|left|WMS A-17981 Trough Receiver Board - First Generation]] 
The first generation (Judge Dredd - Indiana Jones ???) used a receiver board with all of the switch logic on the board. The vibration in the trough makes extra components subject to failure. The second generation (xxx -) uses a regular opto board, and the trough receiver just has phototransistors.

As with all Williams opto circuits, the transmitters are driven to the very limit, and the series resistors overheat. This overheating destroys the solder joints.

Also, the continued vibration makes the resistor legs crack, and weakens the pins in the IDC connectors.

Later versions used rubber grommets to isolate the boards from the trough. 

=====Trough Problems=====
'''What Goes Wrong?'''

======Broken Parts Leads======

[[File:WMS WPC Trough Transmitter Reworked.JPG|thumb|left|300px|Typical Trough Opto Transmitter Boards after resistors have been replaced or soldered multiple times]]

The resistors on the emitter board are subject to cracked legs. Wiggle them to see if they are good. replace the resistor if there are any signs of trouble. On earlier receiver boards, inspect all components.
 

======Trough Divots======
[[File:WMS_WPC_Gravity_Trough_Dimpled.JPG|thumb|300px|left|Typical Trough Divots Caused by Balls]]
Balls make great hammers and, over time, they will beat divots into the trough floor. Then, they will then rest in the divots and cause all kinds of ball count problems. The problem is exacerbated with slightly magnetized balls.

The fix is to file them out, and then sand the metal smooth. A dremel tool with grinding stone works great for this.

Installing a shim that slides over the divots is also a fix for this issue. There use to be both [https://www.pinballlife.com/williamsbally-trough-shimprotector.html metal versions (now PETG)] and [https://www.marcospecialties.com/pinball-parts/03-16809 PETG plastic versions] on the market. Only the PETG plastic versions are available now, as far as we know. The shim eliminates the ability of balls to rest in the divots as well as breaking any magnetic connection, especially with the PETG plastic version.
 

====WH2O Chaser Lamp Board (A-15761)====
[[File:A-15761ChaseLampBoard.jpg|300px|thumb|left|A-15761 Chase Light Board]]
[[File:A-15761Schematic.jpg|300px|thumb|right|A-15761 Chase Light Board Schematic]] 
This board is used for the chaser lamps on Whitewater. It is a simple lamp sequencing board that causes the lamps to "chase".

The board rectifies 16VAC via BR1 and BR2 to create approximately 12VDC to power the chase lamps. The board also receives 12VDC from the power/driver board and regulates it down to 5VDC via an LM7805. This 5VDC is used for the logic level ICs on the board.
 

====CFTBL Chase Light II Board (A-15541)====
[[File:5768-13221-02.jpg|300px|thumb|left|A-15541 Chase Light II Board]]
[[File:A-15541Schematic.jpg|300px|thumb|right|A-15541 Chase Light II Board Schematic]] 
This board is used for the chaser lamps located around the ramps and whirlpool bowl in Creature From the Black Lagoon. 

Eight BT138 triacs, which are pre-driven by 2N4403 transistors, control eight discrete lamp strings. In addition to the lamps chasing, the lamp strings can be dimmed for effect. 

====High Current Driver Board (C-13963)====
[[File:C-13963HighCurrentDriverBoard.jpg|300px|thumb|left|C-13963 High Current Driver board as used in NBAFB and Funhouse.]]
[[File:HighCurrentDriverBoard.jpg|300px|thumb|right|C-13963 High Current Driver board Schematic]]
This board drives the jaw motor for the playfield heckler Rudy in the game Funhouse.

The circuitry is identical to the "Corvette/Road Show Dual H-Drive Motor Control Board" in the next section except that this board controls a single motor only. 

==== Corvette/Road Show Dual H-Drive Motor Control Board (A-19159/A-19242-1)====
[[File:WMSMotorDriveBoard.jpg|300px|thumb|left|Dual H-Drive Motor Control Board as found in RoadShow (A-19159/A-19242-1)]]
[[File:A-19159DualHDriveMotorControllerSchematic.jpg|300px|thumb|right|Dual H-Drive Motor Control Board Schematic]]
The "Dual H-Driver Motor Control Board" is used on Corvette and on Road Show. For Corvette, it drives the two small motors that animate the two car race track on the right side of the playfield. For Road Show, it controls both Red and Ted's mouth motors.

While the board has two different part number designations, they are, in fact, identical.

Note: Parts enclosed by "Block A" and "Block B" in the schematics are not stuffed.
Parts near "Block C" and "Block D" in the schematics are stuffed with 5.6ohm resistors when used in RoadShow. Those resistors are not stuffed when used in Corvette. Instead, JP1 and JP2 are stuffed.

Operation 
The board is powered by either 12VDC (J118/2, Roadshow) or 20VDC (J107/6, Corvette) from the power/driver board. 
Each "channel" receives a direction and an enable signal. The signal is either grounded or floating. 
Four transistors on the power/driver board provide these signals (three transistors for Corvette as both motors always run in the same direction in game operation, either forward or reverse). 
Grounding the "enable" pin for a channel enables power to the associated motor. 
Grounding the "direction" pin (or leaving it floating) for a channel causes the motor to turn either clockwise or counterclockwise. 
Each channel can be controlled independently. Hence the name, Dual H-Drive.

=====Dual H-Drive Motor Control Board Problems=====
[[File:CorvetteDualHDrive.jpg ‎|300px|thumb|left|Dual H-Drive Motor Control Board as found in Corvette (A-19159/A-19242-1). Note the absence of 5.6ohm sand resistors]]
What Goes Wrong? 
Most failures are caused by the two 100uf/35V electrolytic capacitors on the board. They sometimes leak and destroy the power traces beneath them. After that, the TIP102/TIP-107 transistors can fail. These are easily tested using the "diode test". The LM339 is relatively beefy and rarely fails but of course, this is possible.

[[image:YT.png]] A YouTube video showing repair and test of a Dual H-Driver motor control board can be found [https://youtu.be/d7ODSyDlLrQ here].
 

====Bi-Directional Motor Board (A-15680)====
[[Image:A-15680BiDirectionalMotorBoardSchematic.jpg|300px|thumb|left|A-15680 Bi-directional Motor Board]]
[[Image:TraceCloseup-A15680.jpg|300px|thumb|right|Close up view of traces under A-15680 filter capacitor]] 

This board is used in Cirqus Voltaire, Dr Who, Party Zone and White Water.

One problematic aspect of the board's design is that the 100µF electrolytic cap is mounted over the trace that carries 12VDC power to the drive transistors. If the electrolytic cap fails and leaks it's corrosive contents, it will eat through the trace and the board won't work correctly. If this happens in WH2O, Big Foot will not turn his head during game test at boot up. The board pictured at left exhibited this problem and was repaired.

Note that this cap, C2, was sometimes not stuffed at the factory. It's purpose is to filter noise from the 12VDC power, but the power is clean enough that this cap isn't really necessary. Note also that the schematics for the board are in error, designating this 100µF/25V cap as C1 instead of C2 as is silkscreened onto the board.

Another seemingly prevalent issue with this board is failure of the diodes. If either D8 or D9 fail, the associated motor will turn ONLY counter-clockwise.

The board is controlled by two transistors on the driver board. One transistor "enables" movement of the associated motor. The other determines whether the motor moves clockwise or counter-clockwise.

[[Image:A-15680Schematic.jpg|300px|thumb|left|Schematic for A-15680 Bi-Directional Motor Drive Board.]] 
 

====Double Flipper Opto Switch Board (A-15894) (Type I)====
[[File:Placeholder.jpg|300px|thumb|left|A-15894 Flipper Opto Board Mounted on the Cabinet Wall]] 
This board is used in early WPC games which used the Fliptronics II board starting with Doctor Who (please confirm first game).

Please note when testing these boards, the right flipper board has to be plugged in for the left board to function. This is due to the +12v and ground connections being daisy-chained through the right board PCB to the left board. The manuals will typically claim the opposite. And in some cases, the +12v is daisy-chained via the right opto board, while the ground is daisy-chained via the left opto board.

It is always best to check the wiring in the game. If two gray or orange wires are connected on one side of the cabinet, the +12v and / or ground are daisy-chained to the the opposite side.
 

====Flipper Opto Board Assembly (A-17316) (Type II)====
[[File:A-17316.jpg|300px|thumb|left|A-17316 Flipper Opto Board]] 
This board is used in later WPC games which used the Fliptronics II board starting with Indiana Jones (verify) and was used until Pinball 2000.
 

====HSII & CFTBL Triac board (A-13088-2)====
[[Image:WMS_A-13088-2_Triac_Board.JPG|300px|thumb|left|A-13088-2 Triac Board]]
[[Image:TriacDriverBoard_Schematic.jpg|300px|thumb|right|A-13088-2 Triac Board Schematics]]
 
This board is used in High Speed 2: The Getaway (for the beacon motor), CFTBL (for the hologram motor), and Hot Shot (basketball redemption game). This triac board was also used in the System 11B game, Whirlwind, under board number C-13088. It was used to control the topper fan.

Since the board is single sided, fractured solder joints are frequently a problem with this board, especially at C1 for some reason. The other failure point on this board is the MOC 3031 otpo-isolator.
 

==== 24 Inch Opto Board (A-15646) ====
[[Image:24InchOptoBoard.jpg|300px|thumb|left|WPC 24 Inch Opto Board as used on BSD and Shadow]]
[[Image:24InchOptoBoardSchematics.jpg|300px|thumb|right|WPC 24 Inch Opto Board as used on BSD and Shadow, schematics]]
 
Note: This board is sometimes referred to as the "24 Switch Opto PC Board".

This board is used on Bram Stoker's Dracula to sense the "Mist Ball" and on Shadow to sense when the ball is at the bottom of the mini playfield. The board is also used in Star Wars: Episode 1, NBA Fastbreak, Judge Dredd, and Hot Shot (basketball redemption game). The usual problem with this board is that the large inductor (marked "106C" in the picture) vibrates off the board. The circuitry on this board is similar to a television remote control circuit. It senses a particular signal frequency.
 

==== Eddy Sensor PCB Assembly (A-18543) ====
[[Image:A-18543EddyCurrentSensor.jpg ‎|300px|thumb|left|WPC Eddy Current Sensor Board]]
[[Image:WMS-A-18543-EddyCurrentSensor.jpg ‎|300px|thumb|right|WPC Eddy Current Sensor Board Schematic]] 
This small board is used on Theatre of Magic, Scared Stiff, Road Show and Star Trek: the Next Generation.

This board is connected directly to the WPC switch matrix. Two switch matrix wires, 12VDC and ground are provided at the 4-pin connector. The other two wire connector, as pictured, connects to an inductor mounted into a routed hole in the playfield bottom. Small changes are sensed in the inductor by the board circuitry and indicated on the switch matrix. 

===== Eddy Sensor PCB Assembly (A-18543) Problems =====
'''What Goes Wrong?'''
[[Image:ToMEddyCurrentSensor.jpg ‎|300px|thumb|left|Eddy Current Sensor Board shown "in situ" in a Theatre of Magic. Note how close the proximity sensor is to the bracket.]]
[[Image:EddyCurrentSensor.jpg ‎|300px|thumb|right|Closeup of Eddy Current Sensor. Note how close the proximity sensor is to the bracket.]] 
 
This board can be somewhat problematic.

If the trim POT on the board hasn't been adjusted in quite some time, the POT can form a "dead spot" in the same way that volume POTs do. Twizzling the POT back and forth a few times generally clears this issue.

The POT should be adjusted so that the board is just on the edge of the indicator LED turning off. Test the adjustment by placing a pinball over the sensor on the other side of the playfied.

Note that the sensor will pick up on any metal that is close by. In the picture at left, the playfield brackets were so close that they were causing the sensor to indicate a ball was present. A combination of moving the sensor as far from the metal bracket as possible, and fine adjustment of the trim POT solved the issue.
 

====TAF & TAFG High Power Board (A-15139)====
[[File:WPC A-15139 High Power Board.JPG|300px|thumb|left|A-15139 High Power board as used in TAF and TAFG]]
[[File:TAFHighDriverSchematic.jpg|300px|thumb|right|Schematic for A-15139 High Power board as used in TAF and TAFG]] 
This board (aka magnet board) drives the three under playfield magnets used on The Addams Family and The Addams Family Gold. It is located under the bottom left of the playfield.

If one (or more) of the TIP-102 magnet drive transistors (Q32, Q34, Q44) on the Power/Driver board has failed, be sure to test the TIP-36c transistors on this board. This board is often fragile and therefore quite hacked due to prior repairs. 

====TAF & TAFG Extra Flipper Power Supply (A-15416)====
[[File:WPC A-15416 Extra Flipper PS.JPG|300px|thumb|left|A-15416 Extra Flipper Power Supply board as used in TAF and TAFG]] 
This board powers the upper flippers and the playfield magnets for The Addams Family and The Addams Family Gold. It is located just to the right and just above the driver board in the backbox. 
 
The schematics for this board are incorrect in the Addams Family manual. Specifically J903 is shown incorrectly. J903 Pins 1 and 2 supply 50v for the magnet board under the playfield. Pins 3 and 4 are ground for the magnet board under the playfield. The bridge rectifier diagram is also incorrectly rotated by 90 degrees. 

==== The Shadow Five Switch and Diode P.C.B. (A-13940) ====
[[File:TheShadowDiodeBoard.jpg|300px|thumb|left|This board was used only on "The Shadow" to provide lamp matrix diode isolation for the 4 "Ring Grain of Wheat" lamps, in-situ.]]
[[File:TheShadowDiodeBoardBare.jpg|300px|thumb|right|The bare board.]] 
This board was used only on "The Shadow" to provide lamp matrix diode isolation for the 4 "Ring Grain of Wheat" lamps. Yes, that's really it's name. 

====Coin Door Interface Board====
[[Image:CoinDoorInterfaceBoardAnnotated.jpg|300px|thumb|left|WPC/WPC-95 Coin Door Interface Board]] 
The coin door interface board provides signal connection between the coin door switches and the WPC switch matrix and dedicated switches like the "diagnostic" and volume control buttons. The coin door interface board also creates the "always closed" switch 24 by bridging column 2 and row 4 with a diode. WPC games use this "always closed" switch to identify switch matrix power issues.

If the coin door interface board gets dusty from flipper parts wearing, clean it. That dust is conductive and may cause odd coinage issues. There really isn't much that can go wrong with this board.
 

====WPC Alphanumeric Plasma Display Board====
[[Image:FHDisplayComponentSide.jpg|300px|thumb|left|The component side of the Funhouse / Bride of Pinbot WPC alphanumeric display.]]
[[Image:FHDisplayGlassSide.jpg|300px|thumb|right|The display glass side of the Funhouse / Bride of Pinbot WPC alphanumeric display.]] 
Funhouse and The Machine: Bride of Pin*Bot used dual 16-Alphanumeric displays, and a special (specific) high voltage power supply/logic board. The high voltage circuit is similar, if not identical, to late System 11 high voltage power circuits. 

Harley Davidson also used dual 16-alphanumeric displays, however, they were placed side by side on separate boards, instead of being "stacked" on one board.
 

====Scared Stiff Crate Board====
[[Image:ScaredStiffCrateBoard.jpg|300px|thumb|left|The "Scared Stiff" Crate Board]] 
This simple board mounts to the top of the Scared Stiff crate. It creates the "eyes" that look out the top of the crate. It contains 8 LEDs, 4 current limiting resistors, and 4 diodes, which isolate the LED "lamps" in the lamp matrix. Very little can go wrong with this board other than fractured solder joints, since it lives in a high vibration area of the game.
 

====DC Motor Control Board (A-16120)====
[[Image:A-16120DCMotorControl.jpg|300px|thumb|left|A-16120 DC Motor Control Board]]
[[Image:DCMotorControlBoard.jpg|300px|thumb|right|A-16120 DC Motor Control Board schematics]] 
This board is used in Cactus Canyon, Demo Man, Monster Bash, No Good Gophers, The Shadow, Twilight Zone, Theater of Magic, World Cup Soccer.
 

====Bridge Driver PCB Assembly (A-15946)====
[[Image:A-15946DCMotorControl.jpg|300px|thumb|left|A-15946 Bridge Driver PCB Assembly]]
[[Image:BridgeDriverPCBAssemblySchematics.jpg|300px|thumb|right|A-15946 Bridge Driver PCB Assembly schematics]] 
This board is used in Indiana Jones and Hot Shots Basketball. The board is close in design to the A-16120 DC Motor Control Board (above). For Indiana Jones, it controls the Path of Adventure motor, which must turn both clockwise and counter-clockwise.

This simple assembly receives 12VDC power and ground, along with two solenoid connections to the driver board. Grounding one pin of the connection causes +12VDC to be output at the motor power pins. Grounding the other pin will cause -12VDC to be output at the motor power pins.

Indiana Jones uses solenoid 22 to move the POA left and solenoid 23 to move the POA right.
 

==== Indiana Jones Path of Adventure (POA) Opto Board ====
[[Image:IJPOAOptoBoard.jpg|300px|thumb|left|The Indiana Jones POA opto board. The optos are identical to those used on cabinet flipper switch opto boards.]] 
This simple board is used in Indiana Jones to provide "travel limit" feedback to the MPU for the POA. Typical problems include fractured solder joints, since the board experiences a lot of vibration from the POA motor, as well as simple opto failures.
 

==== Corvette Z5 Master Board (A-18532), Slave Board (A-19625), and Hall Effect Amplification Board (A-19076)====
[[File:Bally Corvette A-18532 Motor Driver Master.jpg|300px|thumb|left|Bally Corvette A-18532 Motor Driver Master]]
[[File:Bally Corvette A-19625 Motor Driver Slave.jpg|300px|thumb|right|Bally Corvette A-19625 Motor Driver Slave]] 
This pair of boards work together to "rev" the ZR1 LT5 engine toy on the upper left side of the playfield. The master board senses the position of the motor unit using a Hall Effect sensor located below the engine toy assembly. The slave board uses 20V power and four TIP-102s to control four coils below the playfield on the ZR1 LT5 assembly.

Debugging information for the ZR1 LT5 assembly can be found [https://www.pinwiki.com/wiki/index.php?title=Corvette#LT-5_Engine_Electronics_issues here].
 
[[File:A-19076CorvettePCB.jpg|300px|thumb|left|Bally Corvette A-19076 Adjustment PCB for the LT-5 assembly]]
[[File:A-19076CorvetteHallSensorAmplifierBoard.jpg|300px|thumb|right|Bally Corvette A-19076 Adjustment PCB for the LT-5 assembly schematics]]
 

==== WPC A-13901 / A-17402-3 (and variants) Opto Ramp Switch Board (3 Opto Controller) ====
[[File:WMS A-17402 3-opto.jpg|300px|thumb|left|WMS 3 Opto Controller Board (as shown under playfield of Indiana Jones)]]
[[File:WMS A-13901 A-17402-3 Schems.png|300px|thumb|right|Schematics for A-13901 / A-17402-3 3 Opto Controller Board (*Note: R10 value was changed to correct 22K value in schems)]] 
There are several variations of the A-13901 / A-17402 3 opto controller board used on several games. Games such as Indiana Jones, CFTBL, Fish Tales, High Speed 2, Hurricane, Slugfest, Funhouse, and Hot Shot all used some version of this board. The part numbers used are:
*A-13901-1-AI
*A-13901-1
*A-13901-2
*A-13901-3
*A-13901-AI
*A-13901
*A-17402-3
 

==== WPC A-19043-1 Stepper Motor Driver Board ====
[[File:A19043-1.jpg|300px|thumb|left|WMS Stepper Motor Driver Board)]]
[[File:Wpc-stepper-motor-driver_a-19043-1_schematics.jpg|300px|thumb|right|Schematics for A-19043-1 Stepper Motor Driver Board. Unfortunately, these schematics do not appear in the WhoDunnit manual or anywhere else.]] 
The Stepper Motor Driver Board is used only in WhoDunnit (Slot Machine Reels). Three of these boards are used to drive the three slot machine reel stepper motors.
 

==== A-21967-2 Serial 24 Drive PCB Assembly; aka The Champion Pub LED Driver Board ====
[[File:TheChampionPubSpecificLEDDriver.jpg|400px|thumb|left|The Champion Pub LED Driver Board. Image courtesy of Chris Hibler]] 
This board is specific to The Champion Pub. While resembling an opto board, it drives LEDs.
 

==== 48 Lamp & Driver P.C.B (A-20909); aka Safe Cracker Backbox Chase Lamp Board ====
[[File:WMSSafeCracterChaseFront.jpg|400px|thumb|left|Safe Cracker Chase Lamp Board front. Image courtesy of PinSider "DumbAss"]]
[[File:WMSSafeCracterChaseBack.jpg|400px|thumb|right|Safe Cracker Chase Lamp Board back. Image courtesy of PinSider "DumbAss"]] 
This board is specific to Safe Cracker. The board uses 4094 shift registers to shift serial data through the 48 lamp board.
 

====NBA Fastbreak Shot Clock Dual PCB Assembly (A-21399)====
[[Image:NBAFBShotclock.jpg|300px|thumb|left|The two PCBs that are sandwiched together for the NBA Fastbreak Shot Clock. Image Courtesy of Chris Hibler]] 
The Shot Clock assembly is driven ("blanking" and "count") from J110 on the PowerDriver board. It is supplied with 12VUR and Ground from J133. ‎During attract mode, the clock will continuously count down from 24 to about 06 (digits blink from 09 on down).

The PCB uses an LM339 to switch blanking and pulse the counter. Onboard are two 4029 binary counter chips and two 4511 7-segment driver chips. Each pulse of the "counter" signal causes the clock to count down one number.

The two PCBs are connected in a similar way as OEM Twilight Zone clock boards are. The male headers are extra long. They mate via the bottom entry female connectors on the dual LED PCB.
 

==== Coin Doubler Board ====
[[Image:WPCCoinDoublerInSitu.jpg|300px|thumb|left|An Aftermarket "Coin Doubler" Board, shown attached to a WPC MPU.]] 
This aftermarket add-on board connects atop the direct switches connector on the WPC MPU. It intercepts the coin switches and, for each switch closure it sees, sends the computer two closures. This "hack" effectively halves game pricing. This was done because Williams removed the one-coin-per-play pricing for some games to try and force a price increase.

These are still for sale from [https://gameboardsusa.com/shop/ols/products/coin-doubler-board-for-wpc-games-turns-50-cent-play-into-25-cent-play Game Boards USA].
 

===Flipper Coils===

WPC games use different flipper coils dependent on flipper placement and application. Below is a chart of the flipper coils used, their wrapper color, and strength.

{| class="wikitable"
!colspan="4" |WPC Flipper Coils
|-
!Part #
!Color
!Strength
!Notes
|-
|FL-11753 || Yellow || Weakest ||
|-
|FL-11722 || Green || Weaker ||
|-
|FL-20867 || White || See notes || Used only in Safecracker
|-
|FL-11630 || Red || Standard ||
|-
|FL-15411 || Orange || Stronger ||
|-
|FL-11629 || Blue || Strongest ||
|}

Notes:

The FL-20867 flipper coil (white wrapper) was used only on Safecracker. The FL-20867 flipper coil is thought to be between an FL-11722 and an FL-11630 in strength.

Williams also produced an FL-17636 flipper coil (blue wrapper) for use in Star Trek: The Next Generation. This coil is somewhat stronger than the FL-11629, and was used on the prototype games - and some number of production games - to facilitate shots to the Delta ramp. At some point during the ST:TNG production run Williams switched back to FL-11629 coils, perhaps because the Delta ramp shot can be made with an FL-11629 coil with new condition flipper mechs, or due to operator reports of breakage. Still, a large number of games seem to show up with FL-17636 coils, leading one to suspect operators may have swapped out the FL-11629 coils to the stronger FL-17636 coils as the flipper mechs wore. (There is probably an increased chance of breaking playfield plastics and other parts with the FL-17636 coils in place.)

[[File:ParallelCoilWindings.jpg|300px|thumb|left|Note the windings of this typical WPC coil. The larger wire is the high power winding, the smaller wire is the hold winding. Both wires are soldered to the lug on the left.]] 

===WPC Transformers===

{| class="wikitable"
|+Transformers
!| Part Number    || Description           || Distinguishing Features || Games
|-
|5610-12718-00 || WPC, 115/230v || 18VAC sound alphanumeric || BoP, FH, HD
|-
|5610-12835-00 || WPC3, 115/230v || 18VAC sound || BoP, BR, BSD, CFTBL, DW, FH, FT, GI, HD, HS2, Hot Shots Basketball, Hurricane, PZ, Slugfest, T2, TAF, TAFG, TZ, WH2O
|-
|5610-13491-00 || WPC Power || 12VAC sound || IJ, JD, Pinball Circus, Popeye, STTNG
|-
|5610-13953-00 || WPC94 || female line input || Corvette, DH, DM, FS, RS, Shadow, WCS
|-
|5610-14515-00 || WPC Wide Mount ||12VAC sound || AFM, Congo, I500, JB, JM, NF, SC, SS, ToM, TOTAN, WD
|-
|5610-14515-01 || WPC Wide Mount || 12VAC sound || AFM, CC, CP, CV, Congo, I500, JB, JM, JY, MB, MM, NBA, NF, NGG, SC, SS, ToM, TotAN, WD
|-
|5610-15930-00 || transformer p2000 || || RFM
|-
|5610-15930-01 || transformer p2000 || || SWE1
|}

====Primary Voltage Selection Jumpers at the Transformer====
On all WPC games, there are either a 9 pin or 12 pin Molex connector used to change the primary voltage setting fed to the transformer. 9 pin connectors were connected to a pigtail off the transformer itself. Later units used a 12 pin connector on the power source metal box located inside the cabinet floor on the right just inside the coin door. Depending on the placement of the jumpers, common configurations are 115v (typical domestic setting), 230v (European setting), and 100v (Japanese setting). 

It is common to change the voltage setting (220 to 120 volt conversion) if a game is re-imported back into the US. Although probably more common at the moment is to convert a domestic game to 220 volts (more games are currently being exported from the US than imported).

All voltage selection pins are .093 molex pins. Removal of the pins requires a special molex tool. See [http://www.pinwiki.com/wiki/index.php?title=General#Headers.2C_Housings.2C_and_Crimping "Headers, Housing, and Crimping].

'''Important Notes:'''
#When jumpered for 120V operation, the line fuse is an 8ASB, and a 130V Varistor is used.
#When jumpered for 230V operation, the line fuse is a 5ASB, and a 260V Varistor is used.
 

====Early WPC Transformers (9 pin connection)====
The 9 pin connectors used are Molex 19-09-2099 (butterfly connection w/jumpers) and Molex 19-09-1099 (connection on transformer pigtail).
[[File:WPCPowerSelectButterfly.jpg|300px|thumb|left|9 Pin WPC Transformer Power Configuration, configured for US 115V systems.]] 
Jumper settings for 115V should be as follows:
*Pin 1 - black - 115v "hot" input
*Pin 7 - white - 115v "neutral" input
*Pins 2 and 3 jumped together
*Pins 8 and 9 jumped together
 

[[File:230VLineVoltageConfiguration.jpg|300px|thumb|left|9 Pin WPC Transformer Power Configuration, configured for 230V systems.]] 
Jumper settings for 230V should be as follows:
*Pin 1 - black - 230v "hot" input
*Pin 7 - white - 230v "neutral" input
*Pins 3 and 9 jumped together
 

====Later WPC Transformers (12 pin connection)====
[[File:Plug2.JPG|300px|thumb|left|12 Pin WPC Transformer Power Configuration, configured for US 120V systems]]
[[File:Plug1.JPG|300px|thumb|right|12 Pin Connector as Found inside later games]] 
'''Jumper settings for 120v should be as follows:'''
*Pins 1 and 11 jumped together
*Pins 2 and 3 jumped together
*Pins 7 and 10 jumped together
*Pins 8 and 9 jumped together

The 12 pin connector used is Molex 19-09-1129.
 

[[File:WPCEuropeanPowerSelectSascha12Pin.jpg|300px|thumb|left|12 Pin WPC Transformer Power Configuration, configured for European 240V systems]] 
'''Jumper settings for 240V should be as follows:'''
*Pins 1 and 11 jumped together
*Pins 7 and 10 jumped together
*Pins 3 and 9 jumped together
 

===Unused Connectors===
[[File:FactoryTestConnectorOrDeletedFeature.jpg|300px|thumb|right|An example of a "leftover connector". This one appears on the game "No Fear".]] 
Some WPC games include connectors in the backbox or under the playfield that are not used in the production configuration of the game. Possible reasons for this include:
* Connectors were originally installed to support features that were later removed when the game went to production. It was easier/cheaper to simply leave the connectors in place.
* The connectors may have been test connectors that could be used during assembly to ensure all features were operating correctly.
* As explained by a former cable harness designer, some automated wire cutters were limited to a maximum cut length (perhaps 100 inches). If the harness required a wire longer than the maximum cut length, the factory would include a molex connector in the design to achieve the necessary length piecemeal.
 

==Problems and Solutions==
=== General Oddball Problems that Seemingly Defy Logic ===
[[file:SystemReset.jpg|300px|left|thumb|Factory Reset option, used to, you guessed it, return the same system to factory settings]]
Occasionally, a problem such as display artifacts, failing display test, or general illumination dimming working incorrectly (just a few among a whole host of oddball problems) can be cured by performing a "Factory Reset". Factory Reset can be found in the "Utility Menu", U.8. Performing a factory reset will delete high scores and all other settings but will also clean up any "garbage" that may reside in the RAM chip (or NVRAM chip) responsible for the oddball behavior.

[[image:YT.png]] A YouTube video demonstrating what appears to be a DMD Controller RAM problem but was actually caused by garbage in MPU RAM can be viewed [https://youtube.com/shorts/awPA_U-9sN4 here].

[[image:YT.png]] A YouTube video demonstrating a factory reset to address a General Illumination problem can be viewed [https://youtu.be/bbYkc-ge6dE?si=EIZJOLSQCQwNooeO here]. 

=== Jumpers, RAM and ROM size ===
[[Image:WPC089Jumpers.jpg|300px|thumb|left|Closeup of WPC-089 MPU that uses a 6264 RAM and a 4M game ROM. Note jumpers W1, and W2 to set ROM size as well as W3 (out) and R93 (in) to set RAM size.]]
[[Image:WPC089MPUwith62256RAM.jpg|300px|thumb|Right|Closeup of WPC-089 MPU that uses a 62256 RAM and a 4M game ROM. Note jumpers W1, and W2 to set ROM size as well as W3 (in) and R93 (out) to set RAM size.]]

RAM Size 
The WPC-089 MPU can be configured for two different RAM sizes. This is done with jumper W3 and resistor R93 as shown below.
*6264 RAM - W3 out, R93 in (a 1.5K 1/4W resistor)
*62256 RAM - W3 in, R93 out
Both RAM sizes work fine in all games. Williams probably provided this flexibility to allow use of whichever RAM was cheaper or more available. Note: Most NVRAM replacements are 6264 replacements.

[[Image:WPC95RAMSizeJumper.jpg|300px|thumb|left|Closeup of WPC-95 MPU that uses a 62256 RAM. Note jumper W3 is installed to set the RAM size for a 62256 RAM.]]

The WPC-95 MPU can be configured for two different RAM sizes. This is done with jumper W3 (only) as shown below. R93 is always installed.
*6264 RAM - W3 out
*62256 RAM - W3 in
Again, both RAM sizes work fine in all games and most NVRAM replacements are 6264 replacements.
 

ROM Size 
The MPU can also (and needs to be) jumpered for different ROM sizes. This becomes important when upgrading ROMs or swapping a CPU (and ROM) into a different game. Games like Funhouse shipped with a 1M ROM, jumper W2 in, and jumper W1 out. Updating the Funhouse ROM to a larger size ROM requires W1 in and W2 out.

The official Williams ROM size/jumper settings are shown below.
* 512K/1M - W1 out, W2 in
* 2M/4M - W1 in, W2 out
 

===Test ROMs===
Test ROMs are available from [http://www.planetarypinball.com/mm5/Williams/tech/testroms.html Planetary Pinball], but they should only be used in conjunction with a [http://pinballrehab.com/1-articles/solid-state-repair/board-rework-test/243-building-a-wpc-test-fixture test fixture] and not installed in an actual game, as per the official recommendation.

=== Country DIP Switch (or jumper) Settings ===
[[File:WPCCountryCodeJumperMessage.jpg|300px|thumb|left|Country Code Jumper message.]] 
The message shown at left occurs sometimes when the game software seems to want the "country code" jumpers to be configured in a certain way. The simple solution (for English speaking users) is to remove the jumpers noted in the message by cutting them off. This sets the board to "AMERICA2". Twilight Zone, and perhaps game ROM version 9.4H, seem to prefer the "AMERICA2" country code. Other country code jumper configurations are shown below.
 

[[File:WPCCountryCodeJumpersExample.jpg|200px|thumb|left|Two WPC-089 MPUs, one configured with DIP switches, the other with "zero ohm resistors" (jumpers).]] 
Two WPC-089 MPUs are shown at left. Early versions of the MPU used "zero ohm resistors" or jumpers to figure the country code. Later versions of the MPU (as well as WPC-S and WPC-95 MPUs, used DIP switches. 

Note: If a dip switch is installed, always leave W11 and W12 in the OFF position. If both are set on ON, the undervoltage detection circuit on the WPC Power/Driver will not work and both LED2 and LED3 will always remain on.
 

[[File:WPCCountryCodeJumperTable.jpg|400px|thumb|left|WPC-089 Country Code Jumper Table]] 
The complete WPC-089 country code jumper table is shown at left.
 

[[File:WPC95CountryCodeJumperTable.jpg|400px|thumb|left|WPC-S/WPC-95 Country Code Jumper Table]] 
The complete WPC-S/WPC-95 country code jumper table is shown at left. WPC-S/WPC-95 MPUs do not have an "AMERICA2" configuration.
 

===Power-On LEDs and Sound Tones (Bongs)===
When the game is booted, several LEDs in the backbox will light, and the game may provide sound "bongs" to indicate diagnostic status.

A properly booting WPC game will show a "progress bar" on the DMD along with a "ticking" sound which results from a series of reset signals being sent to the sound board. After a successful boot, the sound board will create a single "bong" tone.

==== LEDs on the MPU ====

Note: WPC and WPC-S games label the MPU and Power/Driver board LEDs as "Dxx". WPC-95 games label these same LEDs "LEDxxx".
*D19 (LED201) - "Blanking". This LED should light when power is applied, then after about 1 second, go off and stay off. If D19 remains on, this is an indication that the blanking circuit is turned on which prevents the game from powering coils. The blanking circuit was implemented to eliminate the possibility of damaging the game due to locked on coils when the CPU isn't operating properly.
*D20 (LED203) - "Diagnostics". Once the blanking LED turns off, this LED should begin blinking and remain blinking as long as the game is turned on. This LED is a simple "I'm working" indication from the MPU. This LED is toggled from pin 35 of the ASIC (DLED signal). D20 will also indicate basic issues with the MPU by blinking as such...
**One blink - problem with the game ROM.
**Two blinks - problem with the game RAM (or accessing the RAM, i.e. open traces).
**Three blinks - problem with the ASIC (WPC) or a problem with the security chip (WPC-S and WPC-95).
*D21 (LED202) - "5VDC present". This LED provides a simple indication of the presence of 5VDC. This LED isn't CPU controlled. It's illuminated as long as 5VDC is present.

[[image:YT.png]] A YouTube video of an MPU blinking D20 twice, indicating a RAM issue, can be found [https://youtu.be/7ZEYIVXgDTo here]. 
[[image:YT.png]] A YouTube video of a properly working MPU, showing LED behavior at boot can be found [https://youtube.com/shorts/u3pM0WrxlD4?si=I7EiQvek1b4szexS here].

'''Note:''' It is possible for the switch column IC, U20, to be blown and the damage continuing upstream to U14. In this case, it is possible that the data signals become corrupt and prevent the MPU from booting. D19 and D21 will light but D20 will never light.

[[File:WPCLEDBehavior.jpg|800px|thumb|left|Graphic provided by Ingo Kramer. Used with permission.]] 
[[File:WPCLEDBehaviorUpdated.gif|800px|thumb|left|Graphic provided by Sascha Voksuil. Used with permission.]] 
 

==== LEDs and test points on WPC-089 Power/Driver Boards ====
[[File:WPCBowTie.png|700px|thumb|left|WPC Power/Driver Board "bow tie" of LEDs Normally Lit]] 
The image at left shows the 5 LEDs that are normally lit, forming a "bow tie" (or X-Wing Fighter, if you prefer). Note that some WPC Power/Driver boards are populated with LED2 and LED3 which were meant to indicat high/low line voltage. In practice, those LEDs don't provide that information very well, and should be ignored. 

{| class="wikitable"
! LED/Test Point 
!Explanation
|-
|<center> '''LED1-TP3''' </center> || Normally lit. Indicates presence of regulated 12VDC (12VR). AC voltage is rectified to about 18VDC by BR1 and smoothed by C6 and C7 (this power is tapped for the lamp matrix). D1 and D2 are used to drop the voltage by 1.0 to 1.4V and then the voltage is further regulated down by the LM7812 at Q2. This 12VDC power is shown as "+12V Digital" on the schematics. This power is fused by F114. If LED6 isn't lit, LED1 won't be lit either.
|-
|<center> '''LED2-no TP''' </center> || If installed, provides an indication of high/low line voltage. This LED isn't very useful as it will flicker as power consumption by the game fluctuates.
|-
|<center>  '''LED3-no TP'''  </center> || If installed, provides an indication of high/low line voltage. This LED isn't very useful as it will flicker as power consumption by the game fluctuates.
|-
|<center> '''LED4-TP2''' </center> || Normally lit. Indicates presence of regulated 5VDC. AC voltage is rectified by BR2 and smoothed by C5. The voltage is regulated down by the LM323K at Q1. This 5VDC power is shown as "+5V Digital" on the schematics. This power is fused by F113.
|-
|<center> '''LED5-TP7''' </center> || Normally lit. Indicates presence of unregulated 20VDC. AC voltage is rectified by BR4 and smoothed by C11. The voltage is used to power the flash lamps. Note that beginning sometime during production of Twilight Zone in 1993, a "coin door interlock" switch was added. This switch interrupts power to both the 20VDC and 50VDC circuits when the coin door is opened, providing a measure of safety against higher voltage shocks. If the coin door is opened with power applied, this LED will fade to off. It will not light with the coin door open. This power is fused by F111.
|-
|<center> '''LED6-TP8''' </center> || Normally lit. Indicates presence of unregulated 18VDC. AC voltage is rectified to about 18VDC by BR1 and smoothed by C6 and C7. This 18VDC power is used to power the lamp matrix lamps. This power is fused by F114.
|-
|<center> '''LED7-TP1''' </center> || Normally lit. AC voltage is rectified to about 12VDC by BR5 and smoothed by C30 to provide unregulated 12VDC power. This 12VDC power is shown as "+12V Power" on the schematics. It is used to power motors, optos, and other game features that do not require a precise 12VDC. This power is fused by F116.
|-
|<center> '''TP4''' </center> || Zero Cross. By using an oscilloscope, this test point allows testing of the "zero cross" circuitry. "Zero cross" is when the AC sine wave crosses through the zero voltage point relative to ground. Zero cross is important for the proper operation of the general illumination lamp circuit.
|-
|<center> '''TP5''' </center> || Ground. This test point stud may be used to measure all DC voltages against.
|-
|<center> '''TP6''' </center> || 50VDC power. This test point will actually measure 70 - 75VDC, which is normal and expected. This power is used for all coils in the game including the flippers. This power is fused by F112. Individual coil power circuits are fused by F101 thru F105. F112 protects both BR3 and the bridge rectifier circuit on the FlipTronic II board. Should F112 blow, remove J104 (or J105). Replace the fuse. Power on. If the fuse blows, BR3 has probably failed. If it holds, the bridge rectifier on the FlipTronics II board has probably failed.
|}

[[File:WPC089 power summary.png|800px|thumb|center|Summary schematic of WPC-89 Power Driver board showing test LED's and test points. A PDF of this image can be viewed [[Media:WPC089 power summary.pdf|here]]]]
 

==== LEDs and test points on WPC-95 Power/Driver Boards ====

{| class="wikitable"
! LED/Test Point 
!Explanation
|-
|<center>  '''LED100-TP100'''  </center> || Normally lit. Indicates presence of regulated 12VDC. AC voltage is rectified to about 18VDC by D11-D14 and smoothed by C11 and C12. D1 and D2 are used to drop the voltage by 1.0 to 1.4V and then the voltage is further regulated down by the LM7812 at Q2. This 12VDC power is shown as "+12V Digital" on the schematics.
|-
|<center> '''LED101-TP101''' </center> || Normally lit. Indicates presence of regulated 5VDC. AC voltage is rectified by D7-D10 and smoothed by C9. The voltage is regulated down by the LM317K at Q1. This 5VDC power is shown as "+5V Digital" on the schematics.
|-
|<center> '''LED102-TP102''' </center> || Normally lit. Indicates presence of unregulated 18VDC. AC voltage is rectified to about 18VDC by D11-D14 and smoothed by C11 and C12. This 18VDC power is used to power the lamp matrix lamps, and is subsequently regulated to 12V for use in the switch matrix.
|-
|<center> '''LED103-TP103''' </center> || Normally lit. AC voltage is rectified to about 12VDC by D3-D6 and smoothed by C8 to provide unregulated 12VDC power. This 12VDC power is shown as "+12V unreg" on the schematics. It is used to power motors and other game features that do not require a precise 12VDC.
|-
|<center> '''LED104-TP104''' </center> || Normally lit. Indicates presence of unregulated 20VDC. AC voltage is rectified by D15-D18 and smoothed by C10. The voltage is used to power the flash lamps. Note that a "coin door interlock" switch is present on all WPC-95 games. This switch interrupts power to both the 20VDC and 50VDC circuits when the coin door is opened, providing a measure of safety against higher voltage shocks. If the coin door is opened with power applied, this LED will fade to off. It will not light with the coin door open.
|-
|<center> '''LED105-TP105''' </center> || Normally lit. Indicates presence of unregulated 50VDC. This test point will actually measure 70 - 75VDC. This power is used for all coils in the game. AC voltage is rectified to about 75VDC by D19-D22 and smoothed somewhat by C22.
|-
|<center> '''TP106''' </center> || Zero Cross. By using an oscilloscope, this test point allows testing of the "zero cross" circuitry. "Zero cross" is when the AC sine wave crosses through the zero voltage point relative to ground. Zero cross is important for the proper operation of the general illumination lamp circuit.
|-
|<center> '''TP107''' </center> || Ground. This test point stud may be used to measure all DC voltages against.
|}
[[File:WPC095 power summary.png|800px|thumb|center|Summary schematic of WPC-95 Power Driver board showing test LED's and test points. A PDF of this image can be viewed [[media:WPC095_power_summary.pdf|here]]]]

==== Power on Sound Tones (Bongs) ====

After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs.

Pre-DCS Sound Board Games.
*1 - No issues...enjoy a game.
*2 - U9 RAM failure.
*3 - U18 ROM failure.
*4 - U15 ROM failure.
*5 - U14 ROM failure.

DCS Sound Board Games.
*1 - No issues...enjoy a game.
*2 - U2 ROM failure.
*3 - U3 ROM failure.
*4 - U4 ROM failure.
*5 - U5 ROM failure.
*6 - U6 ROM failure.
*7 - U7 ROM failure.
*8 - U8 ROM failure.
*9 - U9 ROM failure.
*10 - U10-U12 RAM failure. Note: DCS sound board RAM failures are indicated by a message on the display, "U10-U12 RAM error".

Audio/Video Board Games (WPC-95).
*1 - No issues...enjoy a game.
*2 - S2 ROM failure. Note: Two bongs also occur if jumper W3 is IN, and the RAM size is 6264. If an NVRAM was just installed, check this jumper. See the section on [[Williams_WPC#Jumpers.2C_RAM_and_ROM_size | jumpers]].
*3 - S3 ROM failure.
*4 - S4 ROM failure.
*5 - S5 ROM failure.
*6 - S6 ROM failure.
*7 - S7 ROM failure.
*10 - U9, U10, or U11 RAM failure (see below)

[[File:WPC95U9-U11Error.jpg|300px|thumb|left|WPC-95 boot time RAM error message, accompanied by 10 very annoying bongs.]]
[[File:WPC95U10U12Message.jpg|300px|thumb|right|WPC-95 boot time RAM error message, accompanied by 10 very annoying bongs.]] 
A/V sound board RAM failures are indicated by a message on the display, either "U9-U11 RAM error" or "U10-U12 RAM error". This is apparently game software dependent. A/V RAM are, in fact, U9-U11. Apparently, this message wasn't updated in the software with the introduction of the A/V board. 

===Fuses===

Fuses are used to protect the various game circuits when a problem arises and the circuit begins to draw more current than originally designed to draw.

The best way to test a fuse is to remove it from it's fuse holder and "buzz" it with a DMM set to continuity. This method will prevent false positives via "sneak circuits". When removing fuses from a RottenDog aftermarket power/driver board should be done with extreme care as the fuse clips are easily bent and damaged.

====WPC/WPC-95 Fuse Tables====

[[File:WPCFuseList.jpg|400px|thumb|left|WPC Fuse Table from Twilight Zone.]]
[[File:WPC95FuseList.jpg|400px|thumb|right|WPC-95 Fuse Table from Monster Bash.]] 
A typical WPC fuse table is shown at left, WPC-95 fuse table at right.
 

==== F111 Blows, Testing BR4 With Board Still Installed====

[[File:TestingWPC-BR4-InSitu.gif|300px|thumb|left|Click this image for an animation showing how to test BR4 without removing the power/driver board. Animated gif provided by Sascha Voksuil, aka PinSider ZaZa. Used with permission..]] 
Fuse F111 sits between the transformer secondary and BR4. BR4 recitifies AC power for the flash lamps. If BR4 failes shorted, F111 will blow, protecting the transformer secondary winding.

BR4 can be tested "in situ" using the method shown in the animated gif at left. The correct values would be between .4-.6 if this is not clear from the gif. 
Note: This test requires a good fuse to be in place at F111 for the test to work properly.
 

===Melted Blue/White Transformer Secondary Wires at Connector J101===
[[File:MeltedTransformerSecondaryBlueWires.jpg|300px|thumb|left|Melted wires originating at transformer secondary. Image courtesy of Scott Mount.]]
[[File:MeltedTransformerSecondaryBlueWiresAtPowerDriverBoard.jpg|300px|thumb|right|Those same wires, at Power/Driver Board connector J101. Note that the wires have been restuffed into a new IDC connector. This wiring is now correct. Image courtesy of Scott Mount.]]
[[File:J101Short.jpg|300px|thumb|left|A depiction of a short circuit created with connector J101 installed "one pin off". Note the connector is shifted one pin "down".]] 
It is poor practice to repin less than the complete connector. Since J101 often burns and can the source of game resets, operators sometimes clip the lower 5 pins of J101, and then "hack" the connector by adding a 4-pin connector for the two blue/white wires that loop through the original IDC connector. With pin 3 being the "key pin", it then becomes possible to connect the hacked 4-pin connector "one pin off". As depicted in the diagram at left, this causes a direct, and un-fused short. The blue/white wires will heat quickly and melt the insulation, acting like fuses. If power is left on long enough, the next victim will the transformer itself.

To avoid this disaster completely, always repin the full connector and always use a key pin and key plug.
 

===Testing DC Voltages on the Power/Driver Board===
[[File:YT.png]] A YouTube video showing how to test each of the voltages on the WPC-089 Power/Driver board can be found [https://www.youtube.com/watch?v=uz6bnFiCki0&lc=UgwKkBxANoJnz3Xjr3Z4AaABAg here].

===Removing or Installing the ASIC===
[[File:ASICRemovalTool.jpg|300px|thumb|left|Using a PLCC puller to properly remove the ASIC. Grip firmly, and "rock" the chip out gently.]]
[[File:AnotherWPCCrackedASICSocket.jpg|300px|thumb|right|A cracked ASIC socket caused by using other than the correct tool to remove the ASIC.]] 
Should ASIC need to be removed from a WPC MPU, it is strongly advised that tthe proper tool is used, as shown at left. The tool is called a PLCC puller. 
[[File:YT.png]] A video showing the proper technique for removing the WPC ASIC can be found [https://www.youtube.com/watch?v=qKmlsTlagfg here].
 

[[File:DamagedWPC-ASIC.jpg|300px|thumb|left|This ASIC was damaged by not using the proper removal tool.]]
[[File:WPCCrackedASICSocket.jpg|300px|thumb|right|This cracked ASIC socket caused intermittent operation of the game.]] 
Using a jewelers screwdriver or other such tool can fracture the ASIC chip carrier socket as shown at right. Since these are 84 pins sockets, replacement is non-trivial. Using the incorrect tool may also irreparably damage the ASIC itself by permanently fracturing leg joints, as shown at left.
 

[[File:WPC89ASICOrientation.jpg|300px|thumb|left|Correct orientation relative to the PLCC socket, shown here for a WPC-089 or WPC-S MPU board.]] 
The ASIC must be oriented correctly when installed. Pin 1 of the ASIC is marked with a dot impression on the top of the chip. Pin 1 of the PLCC socket is marked with an arrow pointing to pin one. This is true for all versions of WPC MPUs. Orient the ASIC as shown in the picture at left relative to the arrow in the socket, center the chip over the socket, and press firmly on the chip center.
 

=== WPC ASIC Pinout ===
[[File:ASICIcon.jpg|300px|thumb|left|WPC ASIC pinout and board connections|link=https://www.pinwiki.com/wiki/index.php?title=File:WPCASICPinOutRevisionA.pdf]] 
Clicking on the thumbnail at left will open a .pdf file containing pin connections for the WPC (in work) and WPC-S MPUs.
 

[[File:ASICPinOutSmall.jpg|300px|thumb|left|WPC ASIC pinout and board connections|link=https://www.pinwiki.com/wiki/images/e/e1/WPCASICPinoutviaZaza.jpg]] 
Clicking on the thumbnail at left will open a .pdf file containing a graphic image of the ASIC pinout, ''provided courtesy of Sascha Voskuil''.
 

===Minimum Parts Required for WPC MPU to Boot===
[[File:WPCMinimumParts.jpg|300px|thumb|left|The exact minimum parts required for a WPC MPU to boot]]
Pictured at left is a partially populated MPU board. It has been included here for those building their own MPU board to indicate a interim state for testing work in progress. The image represents the exact minimum parts required for a WPC MPU to boot. Note that the switch matrix resistors and capacitors are not necessary.
 

===Game blows power line circuit breaker immediately===
[[File:WPCPowerBoxInside.jpg|300px|thumb|left|Underside of power box showing varistor and thermistor]]
Had a thunderstorm roll through or a power surge from the electric company recently?
The varistor in the power box may have done it's job protecting the rest of the game's circuitry from the possibly tremendous power surge. 

Signs of a failed varistor are typically black, charred discoloration throughout the "button" portion (green in the case of the adjacent picture) of the varistor. Likewise, varistors can blow rather violently, and there may be charred or burnt remains in the area surrounding the varistor. 

Over time, the rating of a varistor will lower, causing "occasional" blowing of the mains fuse. The varistor will visually appear to be OK. A good hint is how violently the fuse blows. Likely varistor problems will cause the fuse to totally obliterate.

Varistors can be purchased from [https://www.greatplainselectronics.com/products.asp?cat=76 Great Plains Electronics]. Order the 130V variant for 120VAC (typically games in the US), and the 275V variant for 240VAC (typically games in Europe).
 

===Credit Dot===
[[file:Credit dot sttng.jpg|300px|left|thumb|Example credit dot on Star Trek The Next Generation]] 
The credit dot is a decimal point (a single, lit pixel on the display), that appears after the number of credits or after the words free play on the DMD display on WPC games. It is a quick indicator used to tell the operator or owner that there may be an issue with the game. Most commonly, there is a switch or multiple switch problems with the game. However, a credit dot will appear for other reasons, such as when the date and time are not set. 

If, after 30 balls or 10 games, a particular switch hasn't registered, the credit dot is posted to alert the user to check the diagnostics. Some high usage switches will trigger the alert earlier. The credit dot may or may not indicate a real problem. For the example shown in the pic, it's simply reporting a switch that is hard to hit in the game. So, the credit dot is actually saying "Play Better". :-)
 

===Battery Issues===

====Relocating the battery from the MPU board====
[[File:WPC CPU Bat Damage.JPG|left|thumb|300px|An example of worse than usual battery damage]] 
Relocating the 3xAA battery pack from the MPU board is always a good idea. Leaky alkaline batteries are the #1 killer of MPU boards. Simply removing the batteries is not an option with WPC games as a message stating "Factory Settings Restored" will be received when the game boots.
 

There are several options other than allowing the battery pack to remain on the MPU board. Below are the two most common methods. 

The first, most common, and most economical option is to remotely locate the battery holder off the MPU board and somewhere below all other boards. This ensures that even if the remotely located batteries leak, they won't leak onto (or even drip onto) any circuit board. Replace the batteries annually, dating them with a Sharpie. Connections are as follows. With the CPU oriented as it would be in the game, solder the red (positive) wire to the upper right battery pack position. Solder the black (negative) wire to the lower left battery pack position. Note: most battery packs do not come with wire leads long enough to allow the battery pack to rest in the backbox bottom. Lengthen the wires as necessary. As can be viewed in the adjacent picture, a male / female .093" Molex connector was added to easily remove the battery pack from the MPU board should the need arise.
<center>
<gallery widths=300px heights=300px perrow=3 caption="WPC, WPC-S, and WPC-95 Remote Battery Holder Connections.">
File:WPC MPU Battery Relocate.JPG|<center>WPC-089</center>
File:WPC-SMPUBatteryConnections.jpg|<center>WPC-S</center>
File:WPC95RemoteBatteryHolder.jpg|<center>WPC-95</center>
</gallery>
</center>
 

====Installing an external battery on a WPC-95 CPU using the Auxiliary Battery header (J213)====
[[File:WPC95AuxBatteryHeader.jpg|300px|thumb|left|Installed Remote Battery Connector]]
[[File:WPC95RemoteBatteryOption.jpg|300px|thumb|right|An alternate, but equivalent method. Positive and Negative are clearly labeled.]] 
The WPC-95 CPU board has an unused external battery connector just above the battery holder. The connector is labeled J213 AUX BAT. The 4 pads can be seen in the above picture of the CPU with the old holder removed. Installing this 4-pin connector is a good and clean way to get the batteries off the board and prevent alkaline damage. The Molex part number for the C-Grid® SL™ 70543 4 pin connector is 70543-003 (Digikey WM4802-ND). Crimp pins for the female side are 16-02-1125 (WM2573-ND) and the housing is 50-57-9404 (WM2902-ND). The WPC-S CPU uses a 5 pin version of this connector.
 
Warning: Do not use both the internal and external connector at the same time. Doing so will likely damage the batteries.
 

====Settings Not Held or Battery Depletes Rapidly====
[[File:WPC MPU D1 D2.JPG|left|thumb|300px|A WPC MPU board with D1 and D2 circled. D1 and D2 are in the identical location on the WPC-S MPU]]
[[File:WPC-95MPUD1D2.jpg|right|thumb|300px|A WPC-95 MPU board with D1 and D2 shown in the middle of the picture, just below the battery holder]]
During the process of installing a remote battery holder, it is a good practice to check the diodes utilized in conjunction with the battery power. Diode D2, a 1N4148, is used to keep the MPU board's logic power from charging the batteries in the battery pack. Diode D1, a 1N5817, is used to keep the battery pack from powering the entire MPU board when the games's power is turned off. 
*If D2 fails shorted, 5VDC power will be applied to the batteries while the game is turned on. The end result is batteries which die prematurely, possibly leak, and/or possibly explode (alkaline batteries do not like to be charged).
*If D2 fails open, the batteries will not power the static RAM, and the "FACTORY SETTINGS RESTORED" message will be displayed when the game boots.
*Should D1 fail, the batteries would more than likely just deplete prematurely.
 

[[File:TestingForPowerAtRAM.jpg|left|thumb|300px|Probing pin 28 of the WPC-95 MPU RAM IC for Vbb (battery backup power)]]
[[File:6264RAMPinout.jpg|right|thumb|300px|Pinout of the 6264 RAM. Note Vcc, upper right, pin 28]] 
Testing to see if battery backup power is reaching the RAM with sufficient voltage is easy.
*Set your DMM to DC Voltage
*Connect the black probe to game ground (in the picture at left, a clip lead is attached to the ground screw)
*Use the red lead to probe pin 28 of the RAM
Measuring in this way should yield over 3.5 VDC. If measuring shows 0 VDC, either the batteries are dead, or D2 has failed (see above).

Ideally, this measurement should yield 1.5 VDC * 3 - .6 VDC = 3.9 VDC. This calculation represents the nominal voltage delivered by a single AA battery, times 3 (batteries), less a typical .6 VDC drop across diode D2. Remember that nominal voltage drop across a typical diode is .5 to .7 VDC.
 

===Replacing the CPU RAM with non-volatile RAM===
[[file:WPCR93.jpg|300px|left|thumb|A WPC-089 MPU board with 6264 RAM, jumper W3 removed, and R93 in place.]] 
A second option is to replace the 6264 static RAM with an NVRAM such as the RAMTRON FM1608 (or FM16W08). NVRAMs in the standard DIP package are becoming hard to find but several pinball parts vendors sell a nice 6264 replacement NVRAM based on these parts.

This method requires desoldering the OEM RAM from the board, and installing a socket on the MPU. Using NVRAM also has the down-side of not maintaining the Real Time Clock. This is meaningless in some games. But some games use the Real Time Clock, like Twilight Zone which moves the playfield clock to the current time of day during attract mode, and Who?Dunnit and Junk Yard which has a "Midnight Madness" feature. Note: the WPC MPU is designed to accept either a 6264 or a 62256 static RAM. See: [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Jumpers.2C_RAM_and_ROM_size Jumpers, RAM and ROM size] for a description of jumpers required when installing a new RAM or NVRAM. It is known that a Ramtron FM1608 chip does not like the voltage to be lower than 4.5V. With a voltage drop of 0.5V across D1, a jumper wire over D1 would be a solution to this problem. You can also just replace the diode D1 with a jumper wire. On a WPC-95 CPU-board you have the option to add W5 in stead of the jumper wire for D1. The result is the same.
 

====Special note Concerning Early RottenDog WPC-TH MPUs and NVRAM====
[[file:EarlyRDMPU.jpg|300px|left|thumb|A RottenDog WPC-TH MPU. Note PCB date code of "0701", circled in yellow.]]
[[file:RottenDogCypress.jpg|300px|right|thumb|Another RottenDog WPC-TH MPU. This one has no date codes at.]]
Most RottenDog MPU boards shipped with a 62256 RAM installed vs the 6264 RAM typically installed in Williams OEM boards. Early versions of the RottenDog board marked with "0701" on the silkscreen, as pictured at left, require the use of a 62256 NVRAM. The reason for this is that the address lines to the RAM position are not JEDEC "standard". Pins 9 and 10 (normally A0 and A1) are tied to ground as can be seen in the image below. A4 and A5 are mapped to pins that are not connected (NC) on a 6264. Thus, the RottenDog non-JEDEC compliant PCB layout will not work correctly with a standard 6264 device. But with a 62256, which has two extra address lines mapped as they are on the RottenDog WPC MPU board, will work perfectly fine.

Another early production board that requires a 62256 but is not marked with a date code, is pictured at right. This MPU shares the same non-JEDEC compliant PCB trace connections but has no date codes of any kind anywhere on the board 

[[file:PrototypeRDSurfaceMountMPU.jpg ‎|300px|left|thumb|A prototype RottenDog WPC MPU that used surface mount components.]] 
The surface mount version of a RottenDog MPU pictured at left was probably never productionized. The board featured a Cypress non-JEDEC compliant 62256 RAM. While it would be unlikely see another example of this board, it would require a surface mount FM18W08 NVRAM also. 

<gallery widths=200 heights=400 class=center>
File:RD62256NVRAM.jpg ‎| A RottenDog WPC-TH OEM installed 62256 RAM
File:RD62256Socket.jpg ‎| The RottenDog WPC-TH MPU RAM position. Note connection between pins 9, 10, and 14 (ground), which corresponds to the Cypress 62256 RAM pinout.
File:CypressCY62256.jpg | The pinout of the Cypress 62256 RAM, which matches the PCB design of the WPC-TH board
File:FM1608PinOut.jpg | The pinout for a typical FM1608 (6264) NVRAM, which is JEDEC compliant
</gallery>
 

=== Repairing Alkaline Corrosion ===
[[image:YT.png]] A YouTube video demonstrating techniques discussed below can be found [https://youtu.be/pu3XmcLuRGg here]
[[file:WPCCorrosion.jpg|300px|left|thumb|A WPC-089 MPU board, after a couple hours of alkaline corrosion abatement.]]
[[file:AlkalineCorrosionCleanupWithLampSocketCleaner.jpg|300px|right|thumb|Using a "lamp socket cleaning stick" for precision removal of alkaline corrosion. These can be acquired at The Pinball Resource.]] 
Alkaline damage abatement on WPC MPUs is generally more difficult than Bally -17/-35 or Stern MPU-100/200 or Gottlieb System 80 MPUs. The traces on WPC MPUs are finer, and more abundant than on any of those boards. And, the "banks" of resistors and ceramic capacitors below the ULN-2803 and LM339s provide numerous hiding places for alkaline damage. The small traces under these components implement the switch matrix on the game.

If alkaline abatement is attempted, and if the ULN-2803 or LM339s are damaged, using any technique other than cutting them off the board, heating the alkaline damaged pads, and pulling the leftover legs out, WILL damage the board further. The alkaline adheres to the component legs and through-holes very strongly, making it near impossible to remove the component using typical desoldering tools, no matter how skilled the individual is.

As is normally done during this process, sand with fine grit sandpaper (or use an abrasive stick as shown on the right for precision work) until bare copper can be seen, treat the board with 50/50 white vinegar/water to neutralize bits of alkaline that may remain (but do your best to remove ALL alkaline damage), then rinse thoroughly with isopropyl alcohol or other favorite cleaner. Re-tin or conformal coat the exposed traces.
 

<center>
<gallery widths=300px heights=300px perrow=3 caption="Replacing an Alkaline Corroded LM339 on a WPC-089 MPU">
File:LM339-1.jpg|<center>A corroded LM339</center>
File:LM339-2.jpg|<center>After cutting one side off, then bending repeatedly to break the other side off</center>
File:LM339-3.jpg|<center>Socket installed. All done. A machine pin socket was used here to allow soldering on both sides of the board. Normally, "dual wipe" sockets are preferred as they have a much longer mate/unmate cycle life.</center>
</gallery>
</center>

[[file:RottenDogAlkalineCorrosion.jpg|300px|left|thumb|A Corroded WPC-089 Aftermarket RottenDog MPU board.]] 
The RottenDog WPC-089 MPU board pictured at left is an extreme example of corrosion creep. Corrosion moved all the way up the remote battery holder wires and onto the MPU. Abating alkaline corrosion on RottenDog MPUs is particularly difficult as the traces and vias are very, very small.
 

'''WPC-089 MPU Alkaline Corrosion Zone''' 

[[file:Wpc89-cpu-lower-parts.jpg|300px|left|thumb|Part identification in the WPC-089 MPU corrosion zone. Image courtesy of Pinsider Sascha Voskuil aka Zaza]] 
Part identification in the WPC-089 MPU corrosion zone.
 

'''WPC-95 MPU Alkaline Corrosion Zone''' 

[[file:WPC95MPUCorrosionAreaParts.jpg|300px|left|thumb|Part identification in the WPC-95 MPU corrosion zone.]] 
Williams located the batteries for the WPC-95 MPU in an even worse location than on WPC-089 and WPC-S boards. With the batteries located above the ASIC socket, there is a substantial probability that severe damage could occur from leaky batteries. The usual alkaline abatement process should be followed.

'''Key:''' 

   Resistors - Blue 
   Capacitors - Yellow 
   Diodes - Red 
   Integrated Circuits - Green 
   Headers/Jumpers - Black 

Note that at least two revisions of the WPC-95 MPU board were produced, each with a slightly different part layout.
 

=== Slam Tilt ===

[[file:WPCSlamTilt.jpg|300px|thumb|left|A WPC game (STTNG) that has been "slam tilted".]] 
WPC games incorporate a slam tilt switch on the back side of the coin door. When closed, the game immediately stops, and the display fills with diagonal lines, as pictured at left. Note that this is not a power problem like a "game reset", below.
 

===Stuck Menu Settings (WPC-95)===
* Clear all the audits and reset to factory defaults.
* If using a battery for the RAM, remove/disconnect the batteries for a few minutes. Power up and check the settings to verify whether or not settings have become unstuck, then power off and reconnect the batteries.

====Stuck Language Setting (WPC-95)====
[[file:WPC95CountryCodeJumperTable.jpg|400px|thumb|right|DIP Switch language setting chart]]
If the MPU language can't be changed via the settings menu, it is possible that the DIP switch bank has failed.
* Be sure that the DIP switch language switches are set correctly as detailed in the table at right.
* Ensure that a DIP switch hasn't failed by buzzing for continuity across a closed switch.
* Use test T.15, "Dip Switch Test", to ensure that the MPU is reading the switches correctly. If the physical DIP switch settings do not match the T.15 test indications, then either the DIP switch has failed, or U11, a 74LS240, has failed.
[[file:Wpc95-dip-switch-test.jpg|400px|thumb|right|Test T.15, "DIP Switch Test"]] 

If there is a bad flipper opto board, this may also cause the language to get stuck (possibly in Spanish) and prevent the language from being changed in the menu settings or by using the MPU's DIP switches. Be sure to replace/repair the bad flipper opto board, then the language should then be able to be changed ([https://pinside.com/pinball/forum/topic/wpc-95-stuck-on-spanish-language-setting Discussion on Pinside])

=== Power Problems with the RottenDog aftermarket power/driver board ===
====Fuse Clips====
[[file:RottenDogFuseClips.jpg|300px|thumb|left|Fuse clips on a RottenDog WPC power/driver board.]] 
The fuse clips used on the popular RottenDog aftermarket power/driver boards are a bit brittle and do not snap back into position if too much bending force is applied to them, much like Data East power supply fuse clips. Once the fuse clip has been bent too much, it will not snap back into position to create a solid mechanical connection to the fuse. This can cause one of the various power voltages to be missing or intermittent.
 

====5V Regulator====
[[file:RottenDog5VRegulator.jpg|300px|thumb|left|The PTR08060WVD, used on RottenDog WPC Power/Driver Boards.]] 
Since the LM323K 5V regulator has been obsolete for many years, RottenDog Power/Driver boards were designed to use a DC-to-DC converter manufactured by Texas Instruments, part number PTR08060WVD. The part can be found [https://www.mouser.com/ProductDetail/595-PTR08060WVD here] and possibly at other vendors.

Note: This part is installed on a RottenDog Power/Driver board with the inductor (copper coil) facing the top of the board. Equivalently, pin 1 of the device should be installed into the left-most PCB through-hole.
 

===Game resets===
One of the more annoying faults exhibited by WPC machines is the chronic reset problem. The game will restart, often when both flippers are used at the same time. Note that game resets are a power issue. "Slam Tilts" are something completely different (see above).

There are several possible reasons for game resets. Before doing '''''any''''' work on the circuit boards, it is recommended that a number of much easier to fix, and just as probable root causes, be examined.

Possible causes are listed below, in the recommended order of examination. This order is a derived from a combination of "ease of examination" crossed with "probability of root cause". The standard advice dispensed on RGP to change BR2 and C5 is often wrong and unnecessary. If BR2/C5 are changed out and the game no longer resets, some will conclude that, sure enough, BR2/C5 was the problem. What is being missed is that along with replacing those components, at the very least, the connectors on the board are being reseated, the solder on the cap and bridge is being reflowed, and the board ground to the backplane is perhaps better due to torquing the screws better. Any of these changes can improve voltage/current enough to reduce the frequency or eliminate resets.

==== The "Replace BR2 and C5 Mantra" ====
And now, a word on the classic "BR2/C5 mantra".
[[File:NutAFingaS.jpg ‎|left|300px]]
[[File:BR2Mantra.jpg ‎ ‎|right|300px]]A long time ago…in a pinball galaxy far, far away…a kindly fellow was playing a nice game of pinball, hitting all the shots, and earning multiball after multiball. Just as he was about to beat the game’s high score to date, the WPC MPU reset. "Not-A-Finga" he yelled in some ancient, dead, language.

A visitor from the neighboring planetary system noted that, "I once fixed that by replacing BR2 and C5". And lo...the mantra was born.

Fortunately, through advances in both our knowledge of these game systems, and the application of clearer thinking, we’ve come to realize that leaping to the “solution” of replacing components before doing real testing is not advisable. Most pinball owners do not possess the skill, experience, and tools that would allow them to work on circuit boards without damaging an expensive, and sometimes irreplaceable board.

Still, with regular frequency, a post will be made on one of the Facebook repair groups or on PinSide that goes something like this…"My game was resetting so I replaced BR2 and C5 and the resets vanished." This logical construct is known as [https://en.wikipedia.org/wiki/Post_hoc_ergo_propter_hoc "Post hoc, ergo propter hoc"] (after this, therefore because of this), an insidious logical fallacy that states "Since that event followed this one, then that event must have been caused by this one". Clearly, this is an invalid assumption. The fallacy lies in coming to a conclusion based solely on the order of events, rather than taking into account other factors that might rule out the connection. 

In reality of course, when components are removed and replaced on a circuit board, attendant "changes" to the state of the game system include…

# reseating connectors and possibly improving electrical conductivity
# possibly changing the connectivity through fractured solder joints which may be flexed differently
# reseating the entire board in the backbox and possibly improving ground for the board
# reflowing solder joints on both components possibly improving electrical conductivity
# possibly improving heat dissipation from the bridge to the heat sink by replacing thermal grease
# perhaps an air conditioner, refrigerator, or heater has shut off thereby increasing available electrical current

So please, hold off on heating up the soldering iron until methodically working through the disciplined process in the following section.

==== WPC 5VDC Power Derivation Path ====
Following is the nominal path from the wall plug to eventual consumers of the clean 5VDC power supplied by the Power/Driver board.
[[file:WPCPowerSelectButterfly.jpg|300px|thumb|right|WPC Transformer Power Configuration Plug, configured for US 120V systems.]] 

#120VAC/60Hz power is nominally provided at the wall plug. Different voltages are accommodated also (see below)
#An RFI (radio frequency interference) filter, which is seldom a contributor to game problems.
#Line power is connected to a service outlet sometimes incorporated into the metal "power box" and made available to the tech via a short, uniquely plugged, extension cord. Line power is wired in parallel and does not require the power switch to be in the ON position.
#Both sides of the AC power pass through the double pole/double throw (DPDT) game power switch
#The "black" side of the AC power passes through an 8A FB fuse housed in a bayonet style (screw in) fuse enclosure.
#The "black" side of the AC power then passes through the thermistor, which limits current inrush into the system.
#"Butterfly" voltage select connector used to accommodate typical voltage systems used around the world (120VAC in US, 230VAC abroad, low line voltage, etc). When configured for 120VAC in the US, the connector and wiring resemble a butterfly.
#Transformer Primary windings
#Transformer Secondary windings
#Yet another Molex connector, mating with the harness that will eventually lead to the Power/Driver board.
#Some games incorporate a "coin door interlock switch" which interrupts coil and flasher power when the coin door is open. If the game is equipped with this switch, there will be an extra Molex connector necessary to implement this switch.
#J101 on the Power/Driver board (WPC-95: J129)
#Full Wave AC rectification and smoothing via BR2 and C5 (WPC-95: D7 through D10 and C9)
#Regulation to 5VDC via the LM323K at Q1 (WPC-95: LM317 at Q1))
#Lighting LED4... (WPC-95: LED101)
#And finally, delivery to 5VDC power consumers via J114, J116, J117, and J118 (WPC-95: J101, J138, J140, and J141)

[[file:WPC95LM317VoltageAdjustResistors.jpg|300px|thumb|left|WPC-95 Voltage Adjust resistors R1 and R1]] 
Note that the LM317 is an adjustable voltage regulator where the LM323K is a 5V specific regulator. The LM317 is "programmed" to 5.108V using precision resistors R1 (750 ohms) and R2 (243 ohms), located just to the right of the LM317 heat sink. It is possible, although not advised, to adjust the output of the LM317 regulator to something other than the nominal 5.108 volts.
 

==== Possibly Skip Steps ====
If the game is resetting only within the first minute or two, and plays fine after that, skip to [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Failed_Thermistor Step 8, Failed Thermistor]. If the thermistor turns out to not be the cause, return to step 1.

==== The "Quick" but Temporary "Fix" ====
[[file:WPCJ101InSitu.jpg|300px|thumb|left|Connector J101 In-Situ (bottom of picture)]]
A quick but temporary fix might be to reseat (remove and then reinstall) J101 and J114 on the Power/Driver board and J210 on the MPU board several times. This might help in two ways.

First, the tarnish that builds up on the male/female connections might be removed slightly. This might be enough to return your game to service quickly. But this is not a long term repair. The proper repair is to repin both the male and female sides of the connectors.

Second, the physical point where the male/female pins meet becomes "welded" over time. That is, the pins develop micro-divots or irregularities that detract from a perfect connection. Reseating the connection may smooth out the defects that have formed and also might move the physical point of contact to a different part of the pins.

Again, reseating these connectors is a temporary fix that might work for a day, a week, or a month.

[[File:YT.png]] A Youtube video of this procedure being performed on a Bram Stoker's Dracula can be found [https://www.youtube.com/watch?v=8Pf7gRSlKo4 here].
 

==== Low Line Voltage ====
''Step 1: measure line voltage''
[[file:TestingLinePower.jpg|300px|thumb|right|Measure line power at the wall plug that the game is plugged into (not on the bench, as shown here). Almost 118VAC...Nice...]]
Low line voltage can occur for several different reasons...

*Peak summer usage may cause a drop in line voltage (at the wall). Nominal voltage should be 115VAC minimum.
*Too many games or "power hungry" devices on the same circuit. This is common when numerous devices are plugged into a power strip.
*Game(s) plugged into an extension cord or power strip with too small of wire gauge. If the game is plugged into an extension cord, make sure that it carries all three conductors and is constructed of '''at least''' 16 gauge wire, or specified as 16/3. Using a beefier 14/3 extension cord is better, and advised if more than one game is plugged into the cord.

If the machine is resetting, open the coin door and measure the AC voltage at the auxiliary socket with the machine turned off, and then with the machine turned on. If the voltage at the auxiliary socket is over 105VAC, the problem is most likely inside the game. If the voltage is below 105VAC, there is a line voltage problem and the local electricity company's help will be needed to correct the problem. 

==== Poor Ground Connection for Power/Driver Board ====
''Step 2: Make sure the power/driver board is screwed down tightly''

[[file:PoorWPCDriverBoardConnection.jpg|300px|thumb|left|As my friends in Texas might say, "that dog won't hunt". All backbox boards must be securely screwed down.]] 
A poor ground connection from the power/driver board to the backbox ground plane can reduce 5VDC by as much as .3 volts. Ensure that the screws that hold the power/driver board down, secure it tightly. 

==== Cracked Power or Ground Header Pins and Cracked Solder Joints at the 5V Fuse ====
''Step 3: Examine the header pins at J101, J102, and J103 as well as LM323K regulator solder joints (WPC-95: J136 and J137)''

[[file:WPCGroundHeaders.jpg|300px|thumb|left|Cracked header pin solder joints at J103 in a Twilight Zone, causing game resets.]] 
Similar to step 2 above, cracked header pins where the power enters the board or at the ground connections on the board can cause game resets. In the picture at left, cracked header pins at J103 (ground) in a Twilight Zone caused game resets. Either reflow the solder, or better yet, replace the headers with new pins.
 

[[file:FracturedSolderJointLM323K.jpg|300px|thumb|left|Fractured solder joints at the LM323K 5V regulator (WPC-95: LM317), causing game resets.]] 
Another place to examine for fractured solder joints is on the solder side of the board, where the LM323K (WPC-95: LM317) 5VDC regulator is placed. This area is subjected to very high temperatures that sometimes causes the solder to crystallize. If the solder joint is in any way suspect, remove the old solder and reflow new solder on the joint. Ensure that a nice solder "meniscus" is created (a volcano shaped solder joint) versus a "doughnut" around the wire lead.
 

[[file:LM323KGroundScrew.jpg|300px|thumb|left|Typical solder joint at the lower right screw head. Image courtesy of Chris Hibler]] 
Make sure that the screw head (sometimes nut head) shown in the lower right of the picture at left is solidly soldered to the thick trace beneath it on both sides. This screw head is the LM323K's connection to ground, which is critical to the regulator's ability to produce clean and consistent 5VDC power. A poor connection will cause random resets.

If necessary, scrape part of the solder mask away from the trace on both sides of the screw. Apply solder flux to the joint and flow solder into the joint. A great deal of heat is required to flow the solder to the screw head.
 

[[file:F113CrackedSolderJoint.jpg|300px|thumb|left|Fractured solder joints at fuse F113.]] 
Fuse F113 (WPC-95: F105) fuses the 5V power for the game. Fractured solder joints here may cause the DMM to read near 5V, yet the joint doesn't allow enough current to pass. This can cause game resets and even cause the game to not boot. Reflowing the solder at these joints is prudent.
 

==== Missing diodes, open diodes, or cold solder joints at the Flipper coils ====
''Step 4: Examine flipper coil diodes''

[[File:ParallelCoilWindings.jpg|300px|thumb|left|Example flipper coil diodes shown on a FL-15411 flipper coil.]]
 
WPC flippers are, in general, the only coils in the game that should have diodes across the coil lugs. While diodes seldom fail, sometimes the pounding environment that flipper diodes must live within causes solder joints to fail. Ensure that each flipper coil has the required two diodes, that the diodes are good, and that they are soldered to the coil lugs with a quality solder joint. 

==== Poor Connections between the Transformer Secondary and the Power/Driver Board ====

''Step 5: Examine the "cube shaped" molex connector in the cabinet''

[[file:WPCTransformerSecondaryConnection.jpg|300px|thumb|left|The 15-pin Molex "cube" connector. The red wires carrying 9VAC to the Power/Driver board can be seen here.]] 
The connections from the transformer secondary to the Power/Driver board can degrade over time, a natural result of hours and hours of "power on" time. Try re-seating each connector. If the reset frequency is reduced or disappears, then the root cause has probably discovered. These connectors should be repinned at a minimum with at least new pins (the connector housings may be salvageable) for a long term solution. It is especially important to re-pin the red 9VAC wires that carry power to the Power/Driver board as this is converted to the 5VDC logic voltage.

Note: the molex pin extractor for these "round" pins is relatively expensive but there is no other good way to remove the pins.
 

==== Poor Connection at J101 on the Power/Driver Board ====
"Step 5.5: Examine both male and female connectors at J101 (WPC-95: J129)"

[[file:WPCJ101InSitu.jpg|300px|thumb|left|Connector J101 In-Situ (bottom of picture)]] 
J101 (WPC-95: J129) connects the transformer secondary supply of both 9VAC (solid colored red wires, ultimately used to create 5VDC power) and 13VAC to the power/driver board. This connector often becomes tarnished, increasing resistance and reducing the effectiveness of the circuit. Reseating the connector may temporarily reduce reset frequency. This is an indication that this connector should be repinned. As always, it's best to repin both the male and female connectors.
 

==== Poor Connections between the Power/Driver board, the CPU, and other PCBs ====
''Step 6: Examine other wiring harnesses and the connectors''

[[file:WPCPickingUpGround.jpg|300px|thumb|left|A convenient location to find ground in a WPC backbox.]]
[[file:WPCTesting5VDCatTP2.jpg|300px|thumb|left|Measuring DC voltage at the 5VDC test point, TP2.]] 
Measure DC voltage at TP2 (WPC-95: TP101) on the Power/Driver board.
#DMM set to DC volts (if not an auto-ranging meter, expect to measure 5VDC)
#Black lead secured to game ground (the ground braid in the head is a good place to pick up ground)
#Red lead on TP2 (WPC-95: TP101). Remember the reading.
 

[[file:WPCTesting5VDCatGameROMPin32.jpg|300px|thumb|left|Measuring DC voltage at pin 32 of the game ROM]] 
Measure DC voltage at the CPU board.
#Again, DMM set to DC volts
#Black lead in the same place
#Red lead on pin 32 of the game ROM, or on pin 2 (center pin) of the MC34064 under voltage watchdog at U10
#Record this reading

Compare the two readings. ANY difference indicates voltage loss between J114 on the power/driver board and J210 on the MPU board. Some voltage loss is expected/natural since no circuit path can provide zero resistance. A difference of .1VDC is enough to warrant examination of the connectors between J114 (WPC-95: J105) on the Power/Driver board and J210 on the CPU board.

Reseating the wire harness that connects the power-driver board to the CPU board may identify the root cause (but reseating is not a long term solution).
 

[[file:WPCZConnector.jpg|300px|thumb|left|The "Z" connector, as used in Twilight Zone, etc.]]
[[file:WPCZConnectorHarness.jpg|300px|thumb|right|The entire harness containing the "Z" connector in Twilight Zone can be removed from the game for easier repinning.]] 
Some games use an interceptor harness to power extra boards (IJ, TZ, WH20, STTNG, FT, etc). There is a inline splice connector (commonly called a Z-connector) between the driver board and the CPU board. The Z-connector can become loose and/or oxidized, contributing to a poor electrical connection between the female connectors. The Z-connector can be replaced with a new one, or more robustly, eliminated by splicing the wires together, soldering, and heat-shrinking. This entirely removes the Z-connector as a contributing factor to game resets.

At least on Twilight Zone, the wire harness that contains the "Z" connector can be removed from the game entirely, as shown at right. This harness has been repinned and the "Z" connector eliminated.
 

[[file:PoorIDCConnections.jpg|300px|thumb|left|A poorly "repunched" IDC connector. This connection was probably "punched" with a small flat-blade screwdriver. Note the bare wires where the insulation has been damaged. Yikes!]] 
Some field techs will "repunch" IDC connectors in an attempt to make a better connection. Without the correct punch tool, sometimes an even worse connection is created, as pictured at left. If the decision is to use IDC connectors, at least use the correct tool to punch the wires.
 

[[file:WPCWornPowerConnectionJ210.jpg|300px|thumb|left|MPU connector J210. This connector has had the plating worn off right where the female connector mates with it. When mated with a worn female connector, increased resistance results in reduced voltage, causing resets and possibly failure to boot.]] 
Tarnished, heat damaged, or damage to header pin plating creates resistance and can sometimes be a contributor to game resets. If the male header pins are tarnished, their female mates are probably tarnished also. If tarnished pins are found, now might be a good time to remove that aspect as a contributor to game resets.
 

If following this step-by-step process, now is the first time that a soldering/desoldering station will be needed.

Replace the male header pins, remembering to clip the correct "key" pin before reinstalling the board into the game.

Replace the female connector and pins with good quality Trifurcon crimp-on pins. IDC (Insulation Displacement Connectors) connectors as found originally on the game were used by the OEM to speed the manufacturing process and do not provide the level of robustness that can be achieved using Trifurcon crimp-on pins and good technique.

Another possible contributor to poor power connections is cracked header pin solder joints. Although, with WPC double-sided PCBs and the relatively large header pin through-holes, this is rarely seen. Should you identify cracked header pin solder joints, it's best to remove as much of the old solder as possible before reflowing new solder at the joint.

Be sure to check the power connections on the display as well. One documented repair involved a Funhouse with a reset issue. The game had a strong +5V signal on the MPU/CPU, a new BR2/C5 and digital voltage regulator. It would play perfectly until someone nudged the machine causing it to reset. During troubleshooting, it was noted that the game would reset (even in attract mode) when the display was lifted out of the backbox or placed back in it. It was then observed that the 2 wire/3 pin power connector had a loose IDC connection. The ground short through vibration was resetting the CPU! Repinning both the male and female ends of this connector with a proper molex housing resolved the issue.
 

==== Using a Multimeter to Test the Bridge Rectifier and Capacitors ====
''Step 7: Bridges and Caps in circuit''

[[file:WPCTestingBR2RectifiedDCVoltage.jpg|300px|thumb|left|Measuring "un-smoothed" DC voltage output from BR2. The voltage is smoothed later by C5. This bridge is functioning properly.]] 
There's one last test we can do before disassembling parts of the machine. This test can clearly identify a bad bridge rectifier or capacitor. You will need a clip lead.

#With the machine off, clip the lead onto the top left lead (positive) of BR2. You will have to do this by feel, as you cannot see the lead. This clip point is the output of the bridge rectifier, and is connected to the smoothing (filter) capacitor and LM323K regulator input. It should be at 9V DC.
#Next, place the other clip on the red (+) lead of your meter.
#Connect the black lead to ground by tucking it under the braid. Check your installation to make sure that nothing is shorting.
#Set your meter to DC volts.
#Turn on the game.

The meter should read about 9V. This will be true whether C4/C5 are working or not. If the bridge rectifier is bad, it will read about 7V.

For the capacitor, turn your meter to AC volts. Note that inexpensive meters may give false readings here. Ideally, your meter should be a true RMS meter. Good capacitors will read about 300mV AC. Bad capacitors will read up to 2VAC. Anything over 1VAC indicates a failed/failing filter capacitor at C5 which should be replaced.
 

==== Failed Thermistor ====
''Step 8: Examine the Thermistor''

[[file:WPCPowerBoxInside.jpg|300px|thumb|left|A look inside a typical WPC power box. This particular box was from a Fish Tales. The Thermistor is grey, the varistor is green.]] 
The thermistor is (generally) a black or grey disk, about the size of a dime. It is located inside the power box which is found just inside the coin door and to the right. If your game has one (and not all WPC games do), it will be connected in series between the power box fuse and the black side of AC power. Note that the power box may also contain a "varistor", or MOV, which is essentially a surge protector. The varistor will be wired in parallel with (across) the AC power. The varistor is not a factor in game resets.

The thermistor's job is to limit current inrush into the capacitors when the game is first powered on. This reduces stress on the bridge rectifiers or diodes in the game's power circuits (which is the primary cause of bridge rectifier failures). After a few seconds, the thermistor heats up and drops to a very low resistance. Failing thermistors pass less current and have to get hotter to work. This heating takes time, so the game will often reset in the first 30 minutes of operation, and then be fine afterwards. Obviously, a cold environment will make the symptoms worse, and a warm room may appear to cure the problem. 

Resetting while the game warms up is therefore a key indicator of a failing thermistor. Note also that DCS and WPC-95 A/V boards may reset independent of the MPU. If this is the case, you'll hear the characteristic same "bong" as when the game boots. 

'''***Safety Warning***''' Unplug the game '''AND''' turn the game off before conducting the following test.

Sometimes, the thermistor may be visibly damaged. However, it may look good and still be bad. An easy test of the thermistor is to jumper across the legs of the thermistor with a heavy gauge wire. If the game resets no longer occur, replace the thermistor with the correctly rated part. The original Williams part number is 5016-12978-00. A replacement is available from [http://www.greatplainselectronics.com/search.asp?pg=1&stext=5016-12978-00 Great Plains Electronics].

While you have the box open try wiggling the connectors (the game '''''IS''''' unplugged!) you probably will find at least one that is loose - this can contribute to reset issues. The fix is to solder all the crimp quick connect ([http://www.pinwiki.com/wiki/index.php?title=File:DSCF0810.JPG examples on coil]) wires to the pins they were connected to in the box: cut the quick connects off, one at a time, and then solder the wires directly. Insulate the connections with Heat-Shrink or a good grade of electrical tape.

==== Questionable Prior Rework ====
''Step 9: Examine prior rework''

The printed circuit boards used in pinball machines sometimes have traces on both sides of the board. Most WPC boards are manufactured in this way. The traces are joined through the board by a thin layer of copper, plated to the inside of the hole. This plating is delicate. Without great care, the plating can pull out or crack when components are removed, especially alkaline damaged components as found on MPU boards (after batteries have leaked) and "snap caps" as found on OEM WPC Power/Driver boards (at C5 for instance).

Extreme care as well as good technique must be exercised when removing these components as it is very easy to lift traces or damage through-holes on the board. If the component is known to be bad, it is sometimes easier to snip the component from the board with a flush cutter and remove each leg of the component individually.

An excellent way to repair a lifted trace or cracked through-hole is to create a [http://www.pinwiki.com/wiki/index.php?title=General#Repairing_traces_or_creating_a_.22solder_stitch.22 solder stitch] between the traces on each side of a two sided board. Some PCB repairmen will install jumpers as a "repair" for cracked through-holes or to "guarantee" connectivity between components. Some PCB repairmen will avoid the use of jumpers in favor of better looking rework.

==== Failed Capacitors ====
''Step 10: Power smoothing capacitors at end of life''

[[file:WPC-C4InSitu.jpg|300px|thumb|left|C4, shown "in-situ" on a typical WPC Power/Driver Board. A new C4 cap has been installed on this board (100µF/10V). Nice job by the installer orienting the cap so that its value is in easy view!]] 
Electrolytic capacitors do not last forever. They are designed to operate for about 1,000 hours at their full rating. Capacitor life is a function of temperature: the cooler the capacitor operates, the longer the life. The system designer must select higher voltage and capacitance ratings to achieve the design life, which can be as short as 5 years in a pinball machine operated continuously in a warm environment.

The WPC Power/Driver board uses a 15,000µF, 25V capacitor at C5 to smooth the full wave rectified AC from BR2. When this capacitor is no longer smoothing the rectified AC well enough to produce a clean 5VDC, the voltage may drop below the threshold enforced by the watchdog circuit on the MPU (an MC34064 at U10). When this happens, resets sometimes result.

Note that commonly available replacement capacitors are rated to 35V, and will work fine for this application. In general, you may use a capacitor rated for higher operating voltages but the capacitance specification (µF, or micro-farads) should not be changed.

C4 (spec'd at 100µF, 10V, axial) can sometimes fail and cause the game to reset also. If you've gotten this far and are replacing C5, you might as well replace C4 too.
 

[[file:PulledThroughHole.jpg|300px|thumb|left|A good view of a 15,000uf cap, with a pulled through hole still on the left lead (the brown donut looking object)]]
[[file:DomedFilterCap.jpg|300px|thumb|right|C5 (lower) and C11 (upper) on a WPC-089 power/driver board. C11 is clearly "domed", a physical indication of it's failure.]] 
Removing the big 15,000uf capacitors on a WPC-089 power/driver board is a bit tricky. More often than not, an amateur will damage the through hole that connects one side of the board to the other, either severing the connection completely, or badly enough to cause intermittent reset issues. Should the through hole be pulled, a [http://www.pinwiki.com/wiki/index.php?title=General#Repairing_traces_or_creating_a_.22solder_stitch.22 solder stitch] needs to be installed, or "jumpers" need to be installed connecting the associated bridge rectifier to the capacitor.

Advice: Without the experience, tools, and technique to accomplish this task, most hobbyists would be well advised to send the board to a pro for rehab.

[[File:YT.png]] A video demonstrating an excellent technique for removing snap caps can be found [https://youtu.be/rs90-UMtCww here].
 

==== Failed Bridge Rectifier ====
''Step 11: Test Bridge Rectifier #2 (BR2)''

The thermistor protects the bridge rectifiers from inrush current. Still, bridge rectifiers will occasionally fail.

''Testing a bridge rectifier is simple.''

[[File:TestingABridgeRectifierFourSteps.jpg|300px|thumb|left|Four Connections to Test a Bridge Rectifier. Black/Red dots represent test lead positions.]] 
The picture at left illustrates the 4 readings to be taken when testing a bridge rectifier.

'''Procedure:'''

#Place your DMM into "diode test".
#Put the black lead of your DMM on the "oddball" lead of the bridge rectifier. This will be the lead that isn't oriented the same as the others (as with the "spade" type of bridge) or the lead that prevents the four legs from forming a square (as with the "wire lead" type of bridge). This will also be the DC positive lead of the bridge.
#Place the red lead of the DMM on each of the adjacent legs, one at a time.
#A reading nominally between .5 and .7 should be seen (this represents the voltage drop across the bridge's internal diodes).
#Swap locations of the red and black leads. A reading of "null" should be seen.
#Now place the red lead of the DMM on the lead opposite of the "oddball" lead, or the DC negative lead of the bridge
#Place the black lead of the DMM on each of the adjacent legs, one at a time.
#Again, a nominal reading between .5 and .7 should be seen.
#Swap locations of the red and black leads. A reading of "null" should be seen.
 

[[File:TestingBridgeRectifier.jpg|300px|thumb|left|Testing a Bridge Rectifier in circuit. This part of the bridge is good.]] 
Readings outside of these ranges indicate a failed or failing bridge. Note that these readings are not "hard and fast". For instance, a reading of .462 is probably acceptable. We are looking for an "open" or a "short". Note also that this test is not conducted "under load" and it is possible for the bridge to test "good" when it will in fact fail under load (this is also true when testing diodes, transistors, etc).
 

[[File:WPC Brdg 1and2 Removed2.JPG|300px|thumb|left|Applying heat transfer grease (heat sink compound) to the new bridge rectifiers.]]
[[File:WPC Brdg 1and2 Removed3.JPG|300px|thumb|right|New bridge rectifiers screwed to heat sink before placing on driver board.]] 

[[File:YT.png]] A video demonstrating the procedure to test and properly replace a bridge rectifier can be found [https://youtu.be/QhcnkAKYMlE here].

Should you decide to replace the bridge, it is best to screw the heat sink to the bridge before soldering it in place as the heat sink is shared between BR1 and BR2. A small amount of heat sink compound between the bridge and the heat sink is necessary. This compound improves conduction of the heat away from the bridge and into the sink. 

Some repair tips suggested cutting the heat sink in half, separating it into two parts, one part for each bridge. This technique is no longer considered to be a best practice.

Solder both the top and bottom solder pads of the bridge. Should the through-hole of the bridge leads be cracked or otherwise damaged, use the "[http://www.pinwiki.com/wiki/index.php?title=General#Repairing_traces_or_creating_a_.22solder_stitch.22 solder stitch]" technique noted above or install jumper wires between the DC outputs of the bridge and the terminals of C5. When clipping the leads of the wire bridge, do not cut into the solder "meniscus" (the "volcano" of solder around the wire lead). Cutting into the solder meniscus can cause cracked solder joints later. 

[[File:WPC Brdg 1and2 Removed.JPG|300px|thumb|left|Bridge rectifiers 1 and 2 removed elegantly with a desoldering iron.]]
[[File:WPC Brdg 1and2 Reinstalled.JPG|300px|thumb|right|New bridge rectifiers installed, and replacement date noted.]] 
With proper desoldering tools, like the Hakko 808 or Hakko 470D, removal of bridge rectifiers and other components is greatly simplified. After replacement of bridge rectifiers is made, it's not a bad idea to mark the replacement date. In doing this, you or anyone else will know when these were replaced, and more importantly that they were replaced. 

==== Failed Voltage Regulator ====
''Step 11: When all else fails...''

The LM323K 5V regulator is a robust device, but it can drift over time to below the design requirement of 4.8VDC. If your 5VDC reads less than 4.8VDC at the test point, or less than 4.75V on the CPU board, you have to replace the regulator. Note that these voltages are compliant to the LM323K's spec. However, at the lower end of this spec, this lower voltage may be the cause of resets.

[[File:EZ-SBC-PS5.jpg|300px|thumb|left|The EZ-SBC PSU5 modern adjustable switching voltage regulator]]
If you decide to replace the LM323K regulator you may wish to consider using an [http://www.ezsbc.com EZ-SBC PSU5] instead. The PSU5 is a 5V 3A high-efficiency switch-mode regulator that is a direct replacement for the LM323K in terms of form factor and current capacity; it is superior to the LM323K due to its reduced power dissipation. When using the PSU5 be sure to replace the KEPS nuts (nuts with captive lock washers) originally used to mount the LM323K with discrete #6 split lock washers and #6-32 hex nuts; the external tooth lock washer of the KEPS nut can contact one of the surface-mounted components on the PSU5.

Note: The EZ-SBC PSU5 has one side affect that may be annoying. At power off, instead of the customary "pop", the speakers emit a loud volume "machine gun" or "fart" sound. While this might be unnerving, it is perfectly harmless. An [https://ezsbc.shop/products/psu5-no-noise updated "no noise" version of the PSU5], identified by a yellow solder mask, does not have this side effect at power off. It is otherwise identical to the original PSU5. 
[[File:YT.png]] An example of the sound can be heard [https://youtu.be/L4MDGddZanI?t=80 here] near the end of the video.
 

==== Failed Electrolytic Capacitor on the MPU ====
''Step 12: Failed C31 on the MPU''

[[File:FailedC31onWPCMPU.jpg|300px|thumb|left|C31 on the MPU. This Philips capacitor has most likely failed.]]
There is one more possibility. C31 acts as a filter on the WPC-089 MPU. It is a 100µF, 10V capacitor, connected between incoming 5VDC and ground. Williams used two primary suppliers for this capacitor, Philips and Illinois Capacitor. If the capacitor is grey with black markings and has the logo "iC" on it, then it is from Illinois Capacitor and is likely ok. However, if the capacitor is blue and shows the manufacturer as Philips, you should replace it as it is most likely bad. The small Philips capacitors in particular have shown an increasing failure rate as these machines get older. This does not only apply to their use on the CPU but anywhere else in the machine. Which means the same rule applies to C4 on the power driver board - if it's a Philips capacitor replace it. If it's an iC capacitor it is likely OK. If you have a spare CPU, swapping the suspect one with a known working CPU is a good diagnostic step.

When replacing this capacitor it is best to use a 100uf 25v capacitor. You should note that by the time Williams got to the WPC-95 system, any place where they used to use a 100uf 10v filter capacitor they now had a 100uf 25v capacitor instead.
 

[[Image:BSDcaprs.jpg|300px|thumb|left|Failed C31 from a BSD CPU.]]
[[Image:FHcaprs.jpg|300px|thumb|right|Failed C31 from a Funhouse CPU.]]
Determining whether or not C31 has failed is a challenge without an ESR meter. A simple visual inspection will not indicate whether the part is good or bad. Here are two C31s, one from a Funhouse and one from a BSD. Both of these are bad. Both should have an ESR reading of less than 2 ohms and a capacitance reading, out of circuit, of 100uf if not slightly more. Both the boards these were installed in would boot successfully on the bench hooked up to a dedicated power supply. Without an ESR meter, one might think these capacitors were fine. In fact, if this was the only thing wrong in the machine on the 5v circuit, chances are the game would operate fine with these capacitors as-is. But if the game is resetting, it is probably best to replace C31.
 

==== The Absolute Last Resort ====
''Step 42: We really didn't want to get to this point!''

'''There is a method of absolute last resort.''' 

The LM323K is an adjustable linear regulator. However, Williams provided no means to adjust the output of the LM323K. As such, the LM323K will deliver a voltage anywhere within the spec range of the device. The spec output voltage range for the LM323K is 4.75 to 5.25 VDC. Some percentage of LM323Ks will fall into the lower range of that spec, which is at, or just above the trip point voltage of the MC34064 voltage watchdog on the MPU board.

The following procedure will increase the output voltage of the LM323K slightly. This procedure is not a substitute for addressing all of the considerations mentioned in previous steps, and should be used cautiously.

[[File:LM323KHackComponentSide.jpg|thumb|300px|right|Ground Trace severed leading to C9.]]
The LM323K draws a small current to operate, which it passes to ground. We can use that current to raise the voltage of the whole LM323K, pushing the output closer to 5V. 
'''Procedure:'''
#Isolate the LM323K's metal case from board ground by cutting the ground traces that run left and right from the nut on the back of the board that bolts the LM323K to the board. The neater you make these cuts, the easier it to reverse this hack.
#Some versions of the Power/Driver board include a ground trace on the component side of the board that provides a ground to the tantalum capacitor at C9. This trace must be cut on the component side of the board.
#Add a 1/2W resistor in series, from the LM323K ground to the board's ground trace.
 

[[File:LM323KHackSolderSide.jpg|thumb|300px|right|LM323K case isolated from ground, and a 25ohm resistor added. This raised the nominal voltage by .2VDC.]] 
A 12 ohm resistor will nominally raise the LM323K voltage output by .1 VDC. 
A 24 ohm resistor will nominally raise the LM323K voltage output by .2 VDC. 
 
Example: 
A 4.90V measurement without load before modification is increased as follows... 
*adding a 16.5 ohm resistor resulted in 5.1V. 
*adding a 24.9 ohm resistor resulted in 5.2V. 
 

==== The Conductive Grease Hack ====
[[What is a "Hack"?]]
Some techs will recommend the use of conductive grease to improve conductivity at a connector. While some techs will "swear '''by''' the stuff", other techs will "swear '''at''' the stuff", and as such, this is not considered a best practice. The grease can extend the life of new header pins, and protect against hostile environments that would cause corrosion. However, when used on header pins that are already damaged, grease can only slow further deterioration. Worse, the heat in the connector will turn the grease to gunk. If you find a flaky connector with gunk in it, you've been "greased" and you will want to re-pin it.

Damaged/burnt connectors should always be [http://www.pinwiki.com/wiki/index.php?title=General#Electrical_Tools replaced]. [http://http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod Dow Corning #4] grease can't help them.

On the other hand [http://http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod DC#4] Electrical Insulating Compound Grease does a superior job reducing friction and corrosion on contacts and that would be considered a net benefit to any game. JRR's shop and others have also found a decrease in the temperature of power contacts using [http://http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod DC#4] along with reduced resistance which should increase the life of the connector. This product is also good to use on EM pins for the interconnect plugs/sockets as it reduces friction and improves conductivity.

Note that [http://http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod DC#4] is stable from -57C to 204C (-70F to 399F). If your game has contacts at the high end of those temperatures then certainly, the [http://en.wikipedia.org/wiki/Magic_smoke smoke] would be getting out...

If other products are used, investigate carefully to ensure they are a proper dielectric grease suitable for high temperature applications. There is a time and place to use this type of product, mostly as a preventative measure on newly replaced contact surfaces. Applying it after the plating has burned off is a questionable practice and no substitute for proper connector replacement.

===Check fuses F114 and F115 message===
[[File:CheckFusesF114andF115.jpg|thumb|300px|left|Check Fuses F114 and F115 Message]]
This message is sometimes displayed when the game boots and a game cannot be started. Most of the time, F114/F115 will be found to be just fine.

The game issues this message because it cannot read the switch matrix normally. The crafty designers at Williams inserted an “always closed“ switch into the matrix as switch 24. Switch 24 isn’t a switch at all, but instead provides the game software with a “known closed” switch matrix return. Switch 24 is actually a diode across column 2, row 4 of the switch matrix and is located on the coin door interface board which itself is located just inside the cabinet on the left wall.

Since the WPC switch matrix circuitry on the MPU uses 12V to determine switch state, the game assumes that the 12VDC power has been interrupted. F114/F115 fuse the 12V generation circuit; F114 on the AC side of BR1; F115 on the DC side of BR1. Hence, the game assumes that one of these fuses is blown and the message is displayed.
 
'''Diagnosing the problem'''

Start by checking DC voltage at TP3. You should see about 12VDC. If not, follow these steps.

#Actually check fuses F114 and F115 using the procedure [[General#Testing_fuses| here]]. If a blown fuse is found, replace it. If F114 immediately blows again, then BR1 is probably shorted. Skip to the paragraph below to test the bridge.
#Check LED6. If not lit (indicating the absence of 18V at TP8), then suspect BR1 or the filter caps for BR1, C6 and C7. If BR1 had failed shorted or if C6 or C7 where shorted (rare) then you would expect to see F114 blown. BR1 can be tested using the procedure below.
#Check LED1. If not lit (indicating the absence of “digital” 12V at TP3, then test D1 and D2 (both 1N4004 diodes that can be tested with the game off or board removed using the standard "diode check" on your DMM).
#If D1/D2 test good, then check continuity from pin 2 of the 7812 voltage regulator at Q2 to J114, pin 5. This verifies the path to ground. If no continuity, check C2 - it may have leaked and corroded the traces beneath it. If so, replace C2 and repair broken traces.
#Next, check continuity from pin 3 of the 7812 to J114, pin 2. This verifies the path through F115 to the 12V power header at J114. If no continuity, check C2 - it may have leaked and corroded the traces beneath it. If so, replace C2 and repair broken traces.
#If this all checks out, yet 12VDC is still not at TP3, then suspect the 7812 voltage regulator at Q2. Q2 is in a TO-220 package (like a TIP-102) and has a small heat sink attached.

'''Alternate Problem Determination Method: Test Power Across the Driver Board'''

[[File:WPC12VRegulatedCircuit.png|center|(The regulated 12VDC circuit, diagram by by Sascha Voksuil aka Zaza)]] 
The diagram above shows the simple path for the 12VDC power regulation circuit. Power may be tested across the circuit, as follows.
#Turn the game on.
#Set your meter to DC volts. If your meter isn't an auto-ranging meter, expect to see less than 20VDC.
#Clip the black lead of your DMM to game ground, or tuck it under the backbox ground braid.
#Probe TP8 with the red lead of your DMM. It should measure about 18VDC. If not, suspect F114.
#Probe the banded side of D1. It should measure about 18 minus .5 to .7 volts, (the typical voltage drop across this kind of diode), or about 17.4VDC. If not, suspect D1.
#Probe the banded side of D2. It should measure about 17.4 minus .5 to .7 volts (again), or about 16.8VDC. If not, suspect D2.
#Probe the top leg of the 7812. It should measure about 16.8V. If not, suspect the trace between D2 and the 7812 or a fractured solder joint at the 7812.
#Probe the bottom leg of the 7812. It should measure about 12VDC since the job of this regulator is to produce 12VDC. If not, suspect the 7812 regulator.
#Probe the right side of fuse F115. It should measure about 12VDC. If not, suspect the trace between the lower leg of the 7812 and fuse F115. In particular, suspect that C2 has leaked and corroded the trace carrying the 12VDC. See: "Leaky Capacitor C2 corrodes trace", below.
#Probe the left side of fuse F115. Again it should measure about 12VDC. If not, suspect F115 is blown or the fuse block has a poor mechanical connection to the fuse or to the PCB.
#Finally, probe pin 2 of J114. It should read about 12VDC. If not, suspect the trace from fuse F115, the connection of the F115 fuse block to the PCB, or a fractured pin at J114.

The only circuit path remaining to test is the path to the ground pin of J114 (pins 5 and 7) from the 7812. This is easily accomplished with power off.

#Set your DMM to continuity and "buzz" between the tab of the 7812 to J114, pin 5 and 7. If no continuity, suspect a fractured solder joint at the center pin of the 7812, or corrosion under C2 that has compromised the trace.

'''Short on the MPU causing F115 to blow'''

There is one more way for the 12VDC power to be lost and for F115 to blow. A shorted IC on the MPU that uses 12VDC can cause F115 to blow. To help isolate the problem to the MPU, replace F115, disconnect power going to the MPU at J210, and turn power to the game on. If the fuse does not blow, the problem is almost definitely on the MPU board. Any of the LM339s (theoretically) or the ULN2803 (definitely) can fail and short 12V to ground, causing F115 to blow.

'''Leaky Capacitor C2 corrodes trace'''

[[File:WPCFailed12VRCircuit.jpg|thumb|300px|left|Filter capacitor C2 (removed), leaking it's corrosive electrolytic contents, eating through traces]]
[[File:WPC12VFilterCapLeakDamage.jpg|thumb|300px|right|Filter capacitor C2 (removed), showing damage caused by a leaky cap.]]
 
Yet one more way for the 12VDC regulated power to be lost is shown in the picture at left. In the picture, the electrolytic cap at C2 has failed and leaked corrosive electrolytic contents onto the board. The lower trace from Q2 (7812 voltage regulator) to C2 (+ side), that goes on to connect to F115 on the solder side of the board, has been eaten away, no longer providing a path for the regulated 12VDC power. Corrective action here is the same as alkaline damage abatement.

Shown on the right is another shot of the damage caused by a leaky cap at C2. This one resulted in reducing the 12V power to about half of spec. 

[[File:WPC12VCorrosion.jpg|thumb|300px|right|Corroded parts in the 12V/Zero Cross circuitry]]
The corrosion resulting from a leaky cap at C2 can be quite extensive. Often, the parts immediately left of C2 are damaged and must be replaced. The part list is as follows, to be installed left to right:
*R206 - 27K ohm
*R198 - 10K ohm
*R199 - 1K ohm
*C1     - .001uf ceramic (or 1000pf, marked 102)
*R204 - 270 ohm
*C12   - .001uf ceramic (or 1000pf, marked 102)
*R205 - 270 ohm
*C3 - .33uf ceramic (not shown, located behind heat sink)
*D2 - 1N4004 (not shown, located behind heat sink)
 

[[File:C2MicroFracture.jpg |thumb|300px|left|This clearly etched trace caused the loss of 12VDC]] 
Any fracture in the trace beneath the capacitor can cause a loss of 12VDC. The image at left was taken from a FishTales Power/Driver board.
 

If TP3 does, in fact, have 12VDC present, then we need to dig deeper.

#First check for 12VDC on the CPU board to ensure that the 12V is getting to the board via the 2 (and possibly 4 if your game has a “Z-Connector”) connectors that carry the 12VDC. An easy place to measure 12VDC on the CPU is at pin 10 of the ULN2803 (U20). Pin 10 is on the bottom row of pins, furthest left. Note that this connection (and also the 12VDC connection to pin 3 of the LM339s) is not shown on the schematic.
#If the CPU is receiving 12VDC, and you still have the “Check fuses F114 and F115” message, then the problem lies within the CPUs switch matrix logic circuitry.
#Prime candidates for CPU switch matrix failure are U20 (a ULN2803), the two LM339s at U18 and U19, the 74LS374 at U14, and the 74LS240 at U13. All of these ICs are in the “corrosion zone” caused by leaky alkaline batteries. If your CPU exhibits the “blue/green fuzzies”, address the alkaline damage first.
#Testing the 74LSXXX ICs is simple using the procedure [[General#Testing_an_integrated_circuit| here]].
#If coil power, flasher power, or even lamp power was somehow shorted to the switch matrix, there is a near 100% probability that the ULN2803 at U20 has been damaged. There is no good way to test the ULN2803 other than using a logic probe with the game powered on. Both the input side and the output side of the ULN2803 should be toggling between logic 0 and logic 1. If not, socket and replace the ULN2803.

[[File:TestingBridgeRectifier.jpg|300px|thumb|right|Testing a Bridge Rectifier in circuit]]
'''Testing a bridge rectifier is simple.'''
#Place your DMM into "diode test".
#Put the black lead of your DMM on the "oddball" lead of the bridge rectifier. This will be the lead that isn't oriented the same as the others (as with the "spade" type of bridge) or the lead that prevents the four legs from forming a square (as with the "wire lead" type of bridge). This will also be the DC positive lead of the bridge.
#Place the red lead of the DMM on each of the adjacent legs, one at a time.
#A reading nominally between .5 and .7 should be seen (this represents the voltage drop across the bridge's internal diodes).
#Now place the red lead of the DMM on the lead opposite of the "oddball" lead, or the DC negative lead of the bridge.
#Place the black lead of the DMM on each of the adjacent legs, one at a time.
#Again, a nominal reading between .5 and .7 should be seen.

Readings outside of these ranges indicate a failed or failing bridge. Note that these readings are not "hard and fast". For instance, a reading of .462 is probably acceptable. We are looking for an "open" or a "short". Note also that this test is not conducted "under load" and it is possible for the bridge to test "good" when it will in fact fail under load (this is also true when testing diodes, transistors, etc).
 

'''Testing BR1 "InSitu"'''

It is possible to test BR1 while the power/driver board is still installed in the game. Thanks to PinSider "Zaza" for the procedure and animation.
#Power the game off
#Ensure fuse F114 is good
#Remove connector J101 on the right side of the power/driver board
#Set your DMM to "diode check"
#Probe as indicated in the animated gif pictured below

[[File:TestingBR1InSitu.gif|Testing BR1 "InSitu".]] 

[[File:Wpc-br.jpg|300px|thumb|left|The heat sink covering BR1 and BR2 on a WPC-board]] 
Take special care when replacing a bridge rectifier. It is easy to lift the traces of the plated through holes when removing these. After removing the heat sink, cut the old bridge rectifier off of the board close to the top leaving as much of the lug as possible. Then add a small amount of solder to the connection on the solder side to improve heat transfer. Finally apply the iron to the solder side to heat the joint and remove the remaining lug with small pliers.

When replacing the new bridge rectifier you should remove the old thermal compound and apply a new thin layer. The old compound can be removed with a little rubbing alcohol. Apply the thermal compound to the top of the bridge rectifiers and reattach the heat sink with the screws [[#Failed_Bridge_Rectifier | (see above)]]. It is much easier to replace the heat sink before resoldering the new bridge rectifier. Make sure that the heatsink is sitting flush with the tops of the bridge rectifiers and that you leave about a 5/8" gap between the bridge rectifier and the board to improve air flow.

Splitting the heat sink between BR1 and BR2 was at one time thought to improve reliability. This is no longer considered a best practice and is not recommended. 

[[File:Wps-diodes.jpg|300px|thumb|left|Diodes replaced BR1 and BR2 on WPC-95 boards]] 
In WPC-95 games, BR1 and BR2 were replaced by a series of diodes. D11-D14 replaced BR1. D7-D10 replaced BR2. These are much less prone to failure. Still, they do fail on occasion. If one or more fail, it's best to replace all four in the "gang". These diodes were originally 6A2 diodes. Replace them with 6A4 diodes (6 amp 200V vs 6 amp 400V). See the "Check Fuses F106 and F101" section below for the equivalent WPC-95 message.
 

===Check Fuses F115 and F116, J112 and Opto 12V Supply Message===
[[File:WPC_Check_F115_F116.JPG|thumb|300px|left|Check Fuses F115 and F116 message displayed on Demo Man]]
[[File:CheckFusesF115F116J112Message.jpg|thumb|300px|right|The same message displayed on I500]] 
Similar to the "Check Fuses F114 and F115" above, games like Demolition Man will display this message at power up if the trough optos are seen as closed (remember, the opto switch open/closed logic is inverted). Debug this issue by checking the 12v connectors at the lower left corner of the driver board and the connectors on the trough opto transmitter and receiver board.
 

===WPC-95 Check Fuses F106 and F101 Message===
[[File:CheckFuses106And101.jpg|thumb|300px|left|Check Fuses F106 and F101 Message]] 
If a WPC-95 game detects loss of 12VDC power by not seeing switch 24 as closed, "Check Fuses F106 and F101" will be displayed at power up. This could obviously mean that F101 and/or F106 are blown. It might also indicate failure of the LM7812 12VDC regulator at Q2 in which case LED102 will be on and LED100 will be off or, failure of one or more of the 6A2 diodes that rectify the AC power (D11-D14). In the latter case, both LED102 and LED100 will be off. Use these LED indicators, as well as testing for 18VDC at TP102 and 12VDC at TP100 to guide your repairs.
 

===Line Voltage Detection - LED2 & LED3===

LED2 and LED3 on the Power Driver Board are indicators for the line voltage detection circuit. On on-board comparator circuit uses +5V and +18V to check the line voltage. The comparator consists of a resistor voltage divider and an LM339 comparator.

The following table shows how to interpret the LED states. Note that other problems with the +18V or +5V supply could cause a high or low line voltage indication.

Line Voltage Indicator Chart
{| class="wikitable"
!LED2
!LED3
!Voltage
|-
|<center>On</center> || <center>Off</center> || <center>OK</center>
|-
|<center>Off</center> || <center>Off</center> || <center>High</center>
|-
|<center>On</center> || <center>On</center> || <center>Low</center>
|}

===Exploding or Damaged 15,000uf Capacitor at C11 (C10 on WPC-95)===

A smoking, domed, or in the worst case exploded filter capacitor at C11 can result from cross connecting J124 and J128 on the power/driver board. Doing so creates a circuit that routes 70VDC coil power through C11 which is typically rated at 25VDC and is meant to filter the 20VDC flash lamp circuit. This is made possible since J124 and J128 are identically implemented. Both are 5 pins wide, both keyed at pin 4. This is possible on WhiteWater, Dr. Who and Bram Stokers Dracula at least, and may also be possible on other games. It is possible on any WPC or WPC-S game that uses J124, whether or not J128 is used.

[[File:J106ConnectedToJ132BlowsC11.jpg|thumb|left|300px| J106 flash lamp power connector with red/white wire incorrectly connected to J132 on a Gilligan's Island, perhaps by Gilligan himself. Image courtesy of FB "Pinball Repair Group II" member Criss King]] 
Another very effective way to blow C11 is to connect the flash lamp power connector at J106 to high power coil grounding circuits at J132. The connectors are the same width and keyed identically. This connects 72VDC coil power to the 20VDC flash lamp power which is filtered by C11, a 15,000uf/25V capacitor, with the same results as mentioned above. 

Other possible causes for a damaged C11 are a shorted flipper coil diode, a shorted drive transistor on the FlipTronics board, or installing backbox ribbon connectors incorrectly (bottom female housing row to top male header row).

[[File:J124J128ErrorBlockingDiode.jpg|thumb|left|300px| A 1N4004 blocking diode installed in series with R224. Image courtesy of John Wart Jr.]] 
An effective method of preventing damage to C11 in the event that one of the conditions above is met, is to install a blocking diode in series with the large sand resistor at R224. Install a 1N4004 (for example) with the banded side facing the PCB as pictured at left.
 

===WPC and WPC-S Games With No Solenoid, Flasher or Feature Lamps, A Blanking Signal Issue===
[[File:SeveredBlankingSignal.jpg|300px|thumb|left|The trace emanating to the right from pin 1 in this picture has been severed by corrosion as it passes between pins 19 and 20.]] 
The blanking signal from the MPU is connected to pin 1 of each of the 74LS374 buffers (U1 thru U5 and U18) that drive general illumination, flash lamps, coils, and feature lamps. Normally, this signal is pulled low by the MPU board, indicating that no faults have been detected and the system is running as expected. Without a low blanking signal, none of the game features implemented by the driver board will be enabled.
[[File:WPCBlankingTracesAnnotated.jpg|300px|thumb|right|Blanking signal "test points" on the WPC-089 MPU board]]
As these games begin to age, the 12V filter cap located at C2 begins to leak it's corrosive contents onto the PCB. As noted in the section titled "[https://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Check_fuses_F114_and_F115_message Check Fuses F114 and F115 Message]", the corrosion often damages adjacent parts and sometimes invades the solder mask to sever critical signals, like the blanking signal or even data signals. If continuity can not be "buzzed" between the blanking and data pins of U1 and U2, and C2 has been leaking, then there is a good chance that the signal trace has been severed under or around U1. Corrosion seems to accumulate under the chip and between the legs frequently. To address this issue, cleanly remove the chip, clean up the corrosion, rebuild traces as necessary, install a socket, and replace the 74LS374 if necessary.

The blanking signal on the MPU originates at the ASIC (pin 34). It is inverted 3 times by U21 and U5 before being distributed to J204, J211, J202 and the blanking LED. J211 connects via 34 pin ribbon to the power/driver board. If the blanking signal fails to reach J211 pin 31, the same behavior as described above will occur. A DMM set to continuity mode should indicate a connection between U5 pin 8 and J211 pin 31. Sometimes, the signal is interrupted by a damaged or poorly formed via, shown in the picture at right.
 

[[File:CorrosionOnBlanking.jpg ‎|300px|thumb|left|Corrosion from a leaky C2 capacitor "jumped" onto this trace, severing the blanking signal downstream of the 74LS374 that controls general illumination, resulting in no flashers, coils or feature lamps. Image courtesy of Marcel Gonzalez.]] 
The blanking signal is propagated across the PowerDriver board by a single trace. If that trace becomes severed for any reason the buffer chips for any/all of the flashers, coils, and feature lamps will become inoperative. In the image at left, corrosion severed the blanking signal trace, causing flashers, coils and feature lamps to not work.
 

===WPC Games With No Flashers===
[[file:WPC-driver-20vdc-circuit.png|400px|thumb|right|Schematics for driver board secondary unregulated 20VDC circuit]]On WPC-89 games, if no flashers are working, and if the game uses a motor and that also isn't working (such as the cannon on T2), the problem might be somewhere along the secondary unregulated 12V path on the WPC driver board. It could be a connector issue, blown fuse, bridge failure, or detached bridge eyelets on the PCB.

# First, check the interlock switch (if applicable on your game) to make sure that it isn't disabling the voltage.
# On the driver board, check LED5. This is lit if 20VDC is present, if not, 20VDC (and 12VDC for the flashers/motors) is missing (or too low). If it is lit, then proceed to check R224 (10W resistor) for the correct resistor value (0.12 Ohms) and continuity for the legs.
# On the driver board, if LED5 is off, check fuse F111.
# Check TP7 to see what the reading for 20VDC actually is. If the reading is near zero, then:
# Check connector J102 for 20VAC on pins 1 and 3. If about 20VAC is present, the issue is likely on the driver board.
# Check the BR4 bridge rectifier using [[General#Testing_a_Bridge_Rectifier|this guide]]. If the bridge is bad, replace it. If not, test for continuity:
# Test for continuity between the bridge legs and nearby connection points.
## For the negative leg, test to the negative leg of C11. Also check for continuity to J115 pin 1 or any pins on J103.
## For the positive leg, test to the positive leg of C11 and the leg of R224 (10W resistor).
## For the AC inputs, check the top/upper AC leg to J102 pin 1, and the lower/bottom leg to J102 pin 3.
# If there is a loss of continuity on one or more legs, it is possible that the eyelets separated from the traces. Only the positive leg has a trace on the back side, which helps anchor the eyelet, while the other three legs are more prone to separation since there are no traces on the back side to help anchor them. They can separate due to fatigue or prior repair work.
## Remove BR4. The easiest approach may be to clip off the bridge and then desolder each wire leg individually.
## There are two possible approaches--adding a wire stich on the top side of the PCB, or adding jumper wires on the back side of the PCB.
##* To stitch: If possible, scrape a little bit of the mask off the affected traces, then add a wire stitch to the top side of the PCB from the exposed trace to the leg hole. Once done, install the bridge and solder the legs.
##* [[file:WPC-driver-BR4-jumpers.jpg|thumb|right|400px|Jumper wire diagram for BR4 on driver board]]Or to add jumpers: just install and solder the bridge, then add jumper wires for the appropriate failed eyelets using 18 gauge wire.
##*# For the negative leg, jumper it to the negative leg of C11.
##*# For the positive leg, jumper it to the positive leg of C11.
##*# For the bottom/lower AC leg, jumper it to J104 or J105 pin 4.
##*# For the top/upper AC leg, jumper it to J104 or J105 pin 5.
# If BR4 tests good, BR4 has continuity, LED5 is lit, TP7 has 20VDC, check R224 for 20VDC on one side and 12VDC on the other. Check for 12VDC at J107 pin 5 & 6, J106 pin 5, and J108 pin 3. Check for connector issues and cold/cracked solder joints at those pins.
 

===Solenoid, Flasher, and Motor problems===

Flashers, solenoids, and motors in WPC games are turned on via transistors on the driver board and in some games, transistors on the [[Williams_WPC#Auxiliary_8-Driver_Board_.28A-16100.29| Auxiliary 8 Driver Board]].

Before proceeding to diagnose solenoid or flasher problems, see this section: [[General#How_coils.2C_flashers.2C_and_motors_are_turned_on| How Coils, Flashers, and Motors are Turned On]].

The general logic for providing a path to ground for a coil, solenoid, flasher or motor (subsequently, we'll refer to coils only, but this is true for coils, flashers, and motors) via the driver board is as follows. Operation of the [[Williams_WPC#Auxiliary_8-Driver_Board_.28A-16100.29| Auxiliary 8 Driver Board]] is similar but control is accomplished via the long ribbon cable from the MPU to the 8-Driver Board.

#The MPU places the appropriate bit pattern on the data bus to control a "bank" of 8 transistor circuits. The data bus is extended to the power/driver board via the interboard ribbon cable.
#The MPU/ASIC "clocks" the appropriate [http://www.datasheetcatalog.org/datasheets/90/375622_DS.pdf 74LS374], an "octal latch" on the power/driver board, to latch data on the data bus into the 74LS374.
#The outputs of the 74LS374 turn on a 2N5401 transistor.
#The output of the 2N5401 turns on a TIP-102 transistor.
#The TIP-102 transistor either provides the path to ground for the waiting coil power or, for higher powered coils, turns on a TIP-36c transistor which provides the path to ground.

The reason that (up to) 3 transistors are used in the circuit is to "amplify" the power. A 2N5401 transistor can handle a comparatively small amount of current. A TIP-102 transistor can handle a much greater current load. The TIP-36c in 8 of the WPC power/driver board circuits can handle an even greater current load.

Note: With the exception of flipper coils and coils driven through the "special solenoid" drivers, diodes used to [http://en.wikipedia.org/wiki/Snubber snub] the reverse current caused by the collapse of the coil's electromagnetic field, are located on the driver board. High power and low power playfield and backbox coils (solenoids 1 through 16) should not have a diode on them. This convention eases the tech's job in that he/she doesn't need to be careful with diode orientation on the coil.

Note: Coils driven by a Flash Lamp drive (solenoids 17 through 20) or by special solenoid drives (solenoids 21 through 28) require a "tie back diode" connection. When a flash lamp drive is used, a diode must be added to the circuitry, as was done with the Terminator 2 single drop target for example, as the power/driver board doesn't include this diode. When a special solenoid drive is used, a connection from the coil, back to the appropriate pin on the driver board which leads to the on-board tie back diode, must be made. See the section [[#Blown / Failing Q20 Transistor on the Driver Board and the Tieback Diode|Blown / Failing Q20 Transistor on the Driver Board and the Tieback Diode]] below for more information

====Weak Trough Kicker====
[[File:WPCTroughKickoutMechanismCropped.jpg|300px|thumb|left|A clearly "gunked up" mechanism. Image courtesy of PinSider Gorgar666.]]
For games with the traditional "above playfield ball trough" (pre-WPC95), a weak kickout is often caused by accumulated congealed lubrication on the pivot point of the kickout mechanism as pictured here. Simply removing the mechanism, cleaning it, and relubricating with a drop of teflon lube will resolve the issue.
 

====Transistor "Quick Check"====
[[File:QuickTransistorCheck.jpg|300px|thumb|left|Testing TIP-102s quickly on a WPC power/driver board.]]
A quick check of the TIP-102s on the driver board can save time. Set your DMM to "continuity check". Place the black lead of your DMM on board ground. Touch the tab of each TIP-102. If the meter indicates continuity, then that TIP-102 is shorted. This quick test works only with TIP-102s and NOT with TIP-36c transistors since the tab of a TIP-36c is connected differently.

For WPC power/driver boards, the lamp matrix TIP-107 transistors can also be checked using this method if the black probe is touched to the 18V test point on the right edge of the board.

[[File:YT.png]] A video demonstrating this technique on a Data East MPU can be viewed [https://youtu.be/VXiS04-yY58 here].
 

===="Help" Info Provided by WPC Games====
[[File:WPCHelpSequence.jpg|300px|thumb|right|WPC games provide help during coil test.]] 
During coil test, pressing the credit button provides a bit of information helpful in debugging your game.

With coil test "stopped", pressing the credit button sequences through the following information.
*Solenoid power and ground (drive) wire colors
*Solenoid power and ground (drive) connections
*The fuse that protects the circuit
*The sequence of cascading transistors that provide a path to ground for the solenoid. In the picture at right, Q82 (TIP-36), Q81 (TIP-102), and Q71 (2N5401) provide the path to ground.
 

====Failed TIP-36c====
[[File:WPCSolenoidGroundTraceBlownAndRepairedAnnotated.jpg|300px|thumb|left|A blown trace (inside the yellow circle) caused by a shorted TIP-36c transistor. The damage has been nicely repaired with a solid core jumper, soldered to through hole components versus "tack soldered" to the trace, making a stronger solder joint. Note: solder flux visible on replaced TIP-102 and TIP-36c later removed with isopropyl alcohol.]] 
When replacing shorted transistors, examine the traces connected to the transistor for further damage. In the picture at left, a shorted TIP-36c was replaced. During test, the first time the TIP-36c was called upon to provide a path to ground for the associated coil, the TIP-36c failed shorted again. This was caused by the blown trace. 

====Blown / Failing Q20 Transistor on the Driver Board and the Tieback Diode====
[[Image:Terminator2DiodeTiebackWireAnnotated.jpg|300px|thumb|left|The violet/orange "diode tieback" wire, attached to the power side of the drop target reset coil in Terminator 2. Photo Credit: John Wart Jr.]]
[[Image:Terminator2-Q20ViolentExposionCropped.jpg |300px|thumb|right|Q20, with a major malfunction, due to the diode tieback wire connection being missing. Photo Credit: John Wart Jr.]] 

Several games (Star Trek the Next Generation, Funhouse, Terminator 2, Indiana Jones, and The Addams Family to name a few), employ the use of a "diode tieback" system on a specific coil or motor. A diode tieback is the use of a clamping diode between the drive transistor ground and the voltage source to accommodate the reverse voltage spike induced when a coil's magnetic field collapses. While Williams moved most clamping diodes to the power/driver board, the flashlamp circuits (drives 17 through 20) don't include a clamping diode. Flash lamps don't create the same reverse voltage spike and hence, don't require a clamping diode. A tieback diode must be added to the game wiring when one of these flashlamp drives are used to turn on a coil or a motor.

The "Special Solenoid" drive circuits (drives 21 through 28) do include a clamping diode but that diode isn't connected to a voltage source. Presumably, Williams did this to provide flexibility in voltage levels used to drive a special solenoid. When one of the special solenoid drives is used to drive a coil or motor, a connection must be made from the power side of the coil or motor back to the associated power/driver board clamping diode via the appropriate header pin at connectors J122 through J126.

If the tieback diode connection is lost, the associated drive transistor on the driver board (as pictured on the right) WILL be damaged. Also, the associated coil is likely to be held on continuously and melt. In the example pictured at left from a Terminator 2, the diode tieback wire is the thin violet/orange wire. It connects from the coil power side on the drop target assembly coil lug to J122 pin 9 on the driver board and then to clamping diode D5. If the solder connection at the coil lug is solid, suspect the wire connection at the J122 IDC connector. Repinning this connection with a good quality crimp-on Trifurcon pin is advised.

The Addams Family uses Q20 for the "Swamp Release" coil, Q22 for the "Bookcase Motor", Q24 for the "Thing Eject Hole", and Q26 for the "Thing Motor", all requiring a tieback diode.

Star Trek: the Next Generation drives the subway diverters via the 8-Driver board in the upper right side of the head. These also require a tieback diode as discussed [http://www.pinwiki.com/wiki/index.php?title=Star_Trek:_The_Next_Generation#Diode_.22Tie_Back.22_missing_causes_8-Driver_Board_transistor_to_fail here].

====Coil Locks On or Flash Lamp Blows at Power On====
One particularly confusing way that a coil locks on or a flasher blows immediately is caused by misplaced connectors on the driver board.

[[File:J124J128J132.png|700px|thumb|left|Williams WPC-089 and WPC-S PowerDriver Board Connectors that are identically keyed.]] 
In the picture at left, it is easy to see that connectors J124, J128, and J132 are all 5 pins, keyed at pin 4.

While the results are game dependent, placing the connector that should be at J124 at either J128 or J132 will cause problems.
 

For instance, on the game '''Black Rose''', placing the connector that should be at J124 at J128 will cause the lower pop bumper to lock on and eventually blow the associated transistor.

'''Analysis'''

J127 is the return for the lower pop among other circuits. By placing the J124 connector at J128, this connects 70V coil power to 20V flashlamp power via PCB trace connections (J124/3 return). The only reason more coils aren't locking on is that the "pin location intersection" of J124 and J127 is only pin 8 (lower pop) and pin 9 (not used, not stuffed).
This "cross wiring" is also placing C11 under stress since it is being fed 70VDC and the cap is rated at either 25 or 35VDC.

[[File:70VatBlackRoseSocket.png|300px|thumb|left|Measuring coil power at a flash lamp socket on Black Rose.]]
[[File:BlackRosePowerDriverBoardCorrectConnections.jpeg |400px|thumb|right|Black Rose Power/Driver board with correct connections shown.]] 
Also on the game '''Black Rose''', placing the connector that should be at J124 at J132 sends 70VDC to a flashlamp socket in the backbox, as pictured at right.

The Black Rose game manual is incorrect in both the coil/flasher listing in the front of the manual and in the section in the back of the manual that details connections.
 

[[File:BlackRoseCorrectedSolenoidListingFrontofManual.jpg|300px|thumb|left|Corrected solenoid table for Black Rose.]]
[[File:BlackRoseCorrectedSolenoidListingBackofManual.jpg|300px|thumb|left|Corrected connection listing for Black Rose.]] 
The two images at left depict corrections to the Black Rose manual.
 

====Coil Locks On====
This is the most prevalent problem observed (versus coil not firing). When a coil locks on, this means that the power that is present at the coil at all times has found a path to ground. Normally, a path to ground is provided via a controlled transistor set on the driver board. In rare cases a frayed wire or a wire with an insulation gap/failure will touch ground and the coil will lock on.

Most of the time, the drive transistor on the driver board has shorted internally and is acting as if it's been turned on. Should this be the case, the following steps will isolate the problem transistor.

#Use the "Solenoid/Flasher Table" at the front of the game manual to identify the likely failed transistor(s).
#Remove the driver board from the game.
#Test the drive transistor (TIP-102 or TIP-36c).

Testing a TIP-102 transistor
#Set the DMM to diode check
#Place the black lead on the center leg
#Place the red lead on each of the flanking legs in turn
#A measurement between .5 and .7 should be displayed
#Readings outside of this range (generally dead shorts) indicate the part has failed.

Testing a TIP-36c transistor 
:[[image:YT.png]] A video showing how to test a TIP-36c can be found [https://www.youtube.com/shorts/KzcPThLxQLs here].
#Set the DMM to diode check
#Place the red lead on the center leg
#Place the black lead on each of the flanking legs in turn
#A measurement between .5 and .7 should be displayed
#Readings outside of this range (generally dead shorts) indicate the part has failed.

If the drive transistor tests failed, remove the part using this [http://www.pinwiki.com/wiki/index.php?title=General#Desoldering_Printed_Circuit_Board_Through_Hole_Components procedure] being very careful with the delicate traces and through holes.

Most of the time, the last transistor in the cascading transistor chain is the only one to have failed. But, it's important to test the upstream transistors before placing the board back into service. If a TIP-102 has been found to have failed, test the upstream associated 2N5401 predriver. If a TIP-36c has been found to have failed, test the upstream associated TIP-102 and 2N5401 predrivers.

[[Image:Terminator2-Q20ViolentExposionCropped.jpg |300px|thumb|left|A failure involving other parts connected to the failed transistor Photo Credit: John Wart Jr.]] Sometimes, additional parts connected to the failed transistor will have been damaged too, as pictured at left. It then becomes necessary to replace those parts, remove carbon (it's a conductor) and to rebuild burned traces as necessary.

When a coil has locked on for an extended period of time, the coil wire insulation heats up, melts, and begins to short together. Left locked on for long enough, the coil becomes a dead short. It's important to test the resistance of the failed coil to ensure that it hasn't been damaged. A resistance measurement less than 2 ohms certainly means that the coil is damaged, but comparing the coil's resistance to other known good coils is the best and easiest test. WARNING: If the coil has become a dead short and remains in circuit, and the game is powered on, the associated driver transistor WILL be damaged. 

====Coil Fails to Work====

Before proceeding, see this section: [[General#How_coils.2C_flashers.2C_and_motors_are_turned_on| How Coils, Flashers, and Motors are Turned On]].

Possible causes for coils failing to fire include:
*The switch associated with the coil is not being sensed by the MPU, and hence the MPU doesn't command the coil to fire.
*The coil doesn't have power
*One/both of the coil wires are not solidly soldered to the solder lug
*The coil winding is open
*The coil power is not finding a path to ground
*Interlock switch is not activating when pressed

=====Associated Switch Failure=====
If the MPU isn't commanding the coil to fire, obviously it won't. For instance, if a slingshot switch isn't being "made" or some other switch matrix problem prevents proper switch sensing, then the MPU won't command the slingshot coil to fire. This type of failure is easy to isolate merely by placing the game in switch test and closing the switch. Also, if during game play, points are scored when the switch closes, clearly the switch is being made. If a coil fires in solenoid test but not in game play, then the root cause is a switch problem versus a coil problem.

=====No Power to the Coil, Coil Wire not Solidly Soldered, or Coil Winding Open=====
Testing for power to the coil is easy.
*Set the DMM to DC volts. If not an auto-ranging meter, expect less than 200VDC.
*Turn the game on.
*Place the black lead on a convenient game ground like the ground braid or side rail.
*Place the red lead on the coil lug with the "fat" wire(s). The fat wire carries power to the coil.
*The appropriate voltage should be read (75VDC for coils, 20VDC for flashers)

If the appropriate voltage is not seen, there are two primary reasons. Either the power circuit fuse has blown or there is a discontinuity in the power wiring from the driver board to the coil. Turn the game off. Remove the associated fuse and "buzz" it with a DMM set to continuity test. While the fuse is out of the board, make sure it's rated at the proper amperage. Generally, WPC coil and flasher circuits are fused with a 3ASB fuse. If the fuses tests good, the next test is to ensure continuity from that fuse to the coil power lug. With the DMM still set to continuity, "buzz" between the fuse and the coil power lug. If continuity isn't proven, the task is then to find the break in continuity between the driver board connector and the coil power lug. Remember that power is "daisy chained" through several coils in the game. That is why some coils will appear to have two power wires soldered to one lug.

If the appropriate voltage is seen, then test for a break in the coil windings. With the game still powered on...

*Place the red lead on the other coil lug.
*Again, the appropriate voltage should be seen.

If the appropriate voltage is not seen, then either the coil winding has a break in it or the winding is not solidly soldered to the coil's solder tabs.

=====Coil Power is Not Finding a Path to Ground=====
The smaller wire attached to one of the coil lugs connects the coil to the driver board. The driver board has a drive transistor allocated for each coil in the game. The smaller wire must have a solid connection back to the driver board. There are two ways to test the path to ground.

#Use a DMM set to continuity to "buzz" the connection of the smaller wire between the coil and the female connector on the driver board. Ensure that the connection of the wire at the IDC connector is solid. If the coil is driven by a TIP-102 transistor, buzzing between the smaller wire on the coil and the transistor tab should show continuity.
#With the game powered on, and a short length of wire stripped on both ends, touch one end of the wire to the ground braid in the head. Touch the other end of the wire BRIEFLY to the tab of the associated TIP-102. If the coil pulls in, then the path to ground has been proven and the failure is likely the TIP-102 itself. NOTE: This test can be performed ONLY when a TIP-102 is the drive transistor. TIP-36c transistors are configured differently. The tab of a TIP-36c is not connected in the same way.

Once the wiring and connector have been verified to be in order, the next step is to test the associated drive transistor. Unlike when a coil locks on and the driver transistor has shorted on, in this case the drive transistor may have failed "open". Test the transistor using the same procedure outlined in the prior section. Replace as necessary.

If the drive transistor tests failed, remove the part using [[General#Desoldering_Printed_Circuit_Board_Through_Hole_Components|this desoldering guide]] being very careful with the delicate traces and through holes.
 

=====High Voltage Interlock Switch Failure=====
On later WPC games (beginning sometime during production of Twilight Zone in 1993), there is a push button switch used for disabling high voltage circuits (20VDC and 50VDC) when the coin door is opened, providing a measure of safety against higher voltage shocks.

Sometimes, this interlock switch can get worn or dirty (or there are problems with the movement of the internal parts), and the switch doesn't always form a closed circuit properly. So, while the coin door is closed, the interlock switch may fail to activate the 20VDC and/or 50VDC circuits.

Note that there is a separate push button switch responsible for reporting to the MPU whether or not the coin door is open in order to display the "high voltage disabled" message. So, if the high voltage interlock switch fails to complete a high voltage circuit, the MPU will have no idea about this failure, and thus not display a notification message.

To test for the issue, turn the game off, and use a digital multimeter in continuity mode across the appropriate switch lugs for the two circuits (20VDC and 50VDC) on the interlock switch. If the lugs are dirty, they may need to be cleaned. If there is black gunk that looks like it may be baked onto the lugs, it may need to be sanded or filed off to reach the bare metal of the switch lug. Once the lugs are clean and the multimeter is attached, then slowly press in the switch button. If a switch closure is not detected, there may be a problem with one of the switch's circuits. If there is only a switch closure at a certain point where the button is only pressed part way, then fails again after being pushed all the way in, there is likely a problem with the internal parts of the switch.

The switch can be opened up and inspected for issues, and possibly cleaned and repaired. Or, it can simply be replaced with an E79-00A momentary switch or E79-30A0 momentary pull-on switch (both are DPDT, 10A, 125/250v).

====Low Coil Voltage====
[[File:WPC-C8.jpg|300px|thumb|left|C8, located near the 50VDC test point, can cause reduced coil power.]] 
Coil power for WPC games is nominally about 70VDC. Very little can reduce this voltage. If the game is delivering significantly less than 70VDC, suspect BR3.

It's also possible for C8 to cause reduced voltage. C8 is a 100uf/150V (sometimes installed as 100uf/100V) capacitor.
 

====Q26 Transistor & Coil Locking On with Rottendog Driver Board====
[[File:Rottendog-wdb089-masking-error.jpg|300px|thumb|left|Masking error on Rotendog WDB089 Rev. 2]]
If the Q26 transistor (and associated coil) keeps locking on with a Rottendog WDB089 driver board, there may be an erroneously exposed trace on the back of the PCB near one of the screw mount notches that is causing a short. It is located at the bottom edge of the board near connector J122. The exposed trace is next to the grounding pad for the screw mount, and excess solder may be bridging them together.

The issue was noticed on a revision 2 board. It is not currently known if other board revisions are affected by the issue.

To address the issue, first remove any excess solder that may be bridging the connection between the exposed trace and the grounding pad. Then, seal the exposed trace with a PCB solder mask material (ie, an overcoat pen would work) or clear nail polish.
 

===Lamp problems===

Lamps (or globes for those of you in the UK) fall into two categories. "General Illumination" and "Controlled Lamps". Your game probably has other lamps which are actually "flashers" that require an 89 or 906 bulb. Flashers are covered elsewhere in this Wiki.

General illumination lamps (GI) provide the ambient lighting for the playfield, backbox, and coin door. These lamps are lit most of the time. The only "controllable" aspect of these lamps is their brightness, which of course, includes off.

Controlled lamps (sometimes called "feature lamps") are under complete CPU control via the 8-by-8 lamp matrix. These lamps illuminate the various "features" of the game such as mode inserts, pop bumper lamps, inlane/outlane insert lamps, etc.

====General Lamp Problems====
[[File:PCBMountLampDivot.jpg|300px|thumb|left|"Divots" in the connection pad of a "twist in" lamp.]] 
WPC and WPC-95 systems employed "lamp boards" to ease the manufacturing process. These lamp board PCBs used "twist in" sockets, each with a 555 lamp. Over time, the pads on these sockets develop "divots" which sometimes results in a poor connection to the twist in socket. This can be easily corrected by removing the lamp board from the game and reflowing the solder on the pads.
 

[[File:WPCPCBLampBoardHeaders.jpg|300px|thumb|left|The solder on these header pins has been reflowed nicely.]] 
Another problem with lamp boards is the header connections. The solder joints at the connection pins often fracture due to connector insertion pressure, heat, fatigue, etc, and due to being a single sided PCB. The fix for this is again to reflow the solder around the header pins.
 

[[File:FracturedSolderJointLampBoard.jpg|300px|thumb|left|Fractured solder joints on this lamp socket caused intermittent operation.]] 
One of the less reliable designs Williams used was to "cantilever" lamp sockets over the end of lamp boards. This was done on a great many games such as Twilight Zone, Judge Dredd, etc. The repeated pressure needed to insert a new lamp into the socket causes the solder to fracture. This can be corrected easily by simply reflowing the solder at the joint. 

However in some instances, the socket has become damaged beyond the simple repair of just soldering the legs to the lamp board. Replacement sockets are available from most pinball parts vendors.
 

If after repairing the lamp board divots, reflowing the header connectors, the lamp socket is still completely intact, (the contacts do break off of the socket sometimes), and the bulb is good, suspect that the diode associated with the particular lamp may be bad.
 

====General Illumination Problems====

'''Background'''

[[File:WPCGIConnectors.jpg|thumb|300px|left|WPC/WPC-S General Illumination Connectors J119 (cabinet), J120 and J121 (repinned)]]
[[File:WPCJ115NewWireColors.jpg|thumb|300px|right|WPC/WPC-S General Illumination Connector J115, with the "2nd Generation" transformer secondary general illumination wire colors. Image courtesy of Chuck Sanderson.]] 
The WPC power/driver board provides 5 GI circuits under CPU "brightness control". The WPC-95 power/driver board provides 3 GI circuits under CPU "brightness" control and 2 circuits that are always powered. Those two circuits are always connected to the backbox lamps. 

GI power is provided by the transformer in the form of 6.3VAC at power/driver board connector J115. Although there are five pairs of wires, they are all connected together at the transformer. One side of the AC GI circuit on the power/driver board is fused by F106 through F110 which are all 5ASB fuses. This side runs to the GI lamps, and carries 6.3VAC to the backbox, playfield, and coin door via power driver board connectors J120, J121, and J119 respectively. J119 is a 3-pin header that is always connected to the coin door lamps. J120 and J121 are electrically and physically identical (keyed at pin 4) and therefore can be connected to either the female playfield GI connector or the female backbox GI connector without care. The other side of the GI AC feed is connected to ground. 

The GI power is controlled by a triac in the return line from the playfield. When these triacs are off, no current passes and the lamps are off. When the triac is turned on, the GI lamps glow. The triac is a slightly special part - it must be a "four sector" triac. This means that it can switch both positive and negative sides of the AC cycle with only a positive signal. 

Each triac is switched on/off by a 2N5401 transistor which is controlled by U1, a 74LS374, an octal D-Type Flip-Flop with three state outputs (a fancy way of saying that the device is an 8-bit data buffer). 

U1 is "clocked" by the ASIC via the /TRIAC signal. If you have AC power present at J115, and no GI at all, it's possible that the /TRIAC signal is not getting through to U1. A logic probe applied to pin 11 of U1 will prove that the signal is getting through. If the signal is not present, try (after turning the power OFF)...
*Pressing firmly on the MPU ASIC to "reseat" it.
*"Reseating" the ribbon cable between the MPU and the Power/Driver board.
*Use your logic probe to track the signal from pin 66 of the ASIC, across the MPU to the MPU connector, across the ribbon cable, then across the Power/Driver board to U1 pin 11.

The CPU can dim the GI by switching on the GI for only parts of the AC waveform. To do this, the CPU uses a zero crossing signal on the driver board keyed from the AC that feeds the 5V circuit, diodes D3 and D38, and the LM339 at U6.

[[image:YT.png]] A video further describing operation of the General Illumination circuit can be found [https://youtu.be/RcAHeP_iTBU here].
 

[[File:WPCJ115.jpg|thumb|300px|left|WPC General Illumination Connector J115 (AC power in). Note wire colors, beginning on the bottom with a yellow/white, then three (looped) yellow, then three (looped) yellow/white.]]
[[File:WPC-GI-RepinAlternative.jpg ‎|thumb|300px|right|WPC General Illumination Connector J115 "dongle" that provides an alternative to looping wires. Two wires are crimped into 4 of the 7 .093 pins, which is much easier than crimping two wires into a .156 crimp pin. Note wire colors, with red connected to yellow/white wires and black connected to yellow wires through the connector. The center pin is used for the "ground reference". This method is identical to the method Williams used in late model WPC games, but this connector is added and moved closer to the Power/Driver board.]] 
Wire colors to J115 during the early WPC games were always yellow (AC) and yellow-white (AC return) as pictured at left. Pin 1 of J115 provides the "ground reference". Later WPC games used different wire colors at J115 and instead of "looping" power through the connector at J115, connected two wires to the same pin at the 9-pin connector between the transformer secondary and J115 (note picture at right that implements the same concept for earlier model games.

The colored wire connections for this era of WPC game are yel-wht connected to pin 1, yellow connected to pins 2-6, yel-wht connected to pins 7,8, 10, 11, & 12. Pin 9 is the key.
 

J119 is always keyed at pin 2, with a white-Violet wire at pin 1 and a Violet wire at pin 3

J120 and J121 are 11 pin connectors. Wire color/positions (when used) are identical for all WPC games and are shown in the table.

{| class="wikitable"
!<center> Pin </center>
! Wire color at J120/J121    
|-
|<center>1</center> ||  Brown
|-
|<center>2</center> ||  Orange
|-
|<center>3</center> ||  Yellow (yellow)
|-
|<center>4</center> ||  Key
|-
|<center>5</center> ||  Green
|-
|<center>6</center> ||  Violet
|-
|<center>7</center> ||  White-Brown
|-
|<center>8</center> ||  White-Orange
|-
|<center>9</center> ||  White-Yellow (yellow)
|-
|<center>10</center> ||  White-Green
|-
|<center>11</center> ||  White-Violet
|}

'''Common GI Problem Causes''' (listed by probability/ease of testing and correction)

'''GI Bulbs Not Lighting'''

Let's start by determining if the problem is "off board", i.e. not on your power/driver board, or "on board".

#Take note of the wire color of the GI string that is not working.
#Set your DMM to AC voltage. If your DMM is not an "auto-ranging" model, expect to measure about 7 volts AC.
#Turn the game on.
#Insert one probe of your DMM (either one) into the rear of the female connector position with the same wire color as noted earlier. Make sure you make contact with the conductor.
#Insert the other probe into the rear of the female connector with the white wire that has the same color "tracer" as the color noted earlier.
#You should be measuring 6 to 7 VAC.
#If there is voltage at the connector, then the problem is "off board".
#If there is no voltage at the connector, then the problem is "on board".

'''Off board GI problems'''

#'''All lamps blown.''' Don't laugh. Just for giggles, put a known working lamp into one of the lamp sockets of the suspected GI string. I've seen it more than once. Usually the result of operators never changing a bulb, or somehow connecting higher voltage to the circuit.
#'''"Open" in GI wiring.''' The GI wires leading from J120/J121 may be cut/broken between the connector and the GI lamp sockets. Remove both of the female connectors at J120/J121. Use your DMM to check continuity between the lamp socket and the appropriate wire/pin at J120/J121.

'''On board GI problems'''

#'''Blown fuses.''' This is also the easiest problem to fix. Check each GI fuse following this [[General#Testing_fuses| procedure]]. Don't trust your eyes.
<ol start="2">
<li>'''Loss of "Cross Board" Connectivity.''' This problem is generally caused by burned header pins, traces, or in some cases, poor prior repairs. Use the following table to check cross board connectivity with J120/J121 as your target. Buzz between the pins/parts shown in the table or use the diagrams below.
{| class="wikitable"
!<center> GI Connector/pin </center>
! Connects to 
! ...and to fuse 
! associated circuit wire color 
|-
|<center>J120-1</center> ||  Triac Q18 tab    ||  ||  Brown
|-
|<center>J120-2</center> ||  Triac Q10 tab  ||   ||  Orange
|-
|<center>J120-3</center> ||  Triac Q14 tab  ||   ||  Yellow (yellow)
|-
|<center>J120-4</center> ||  Key pin  ||  ||  
|-
|<center>J120-5</center> ||  Triac Q16 tab  ||   ||  Green
|-
|<center>J120-6</center> ||  Triac Q12 tab  ||  ||  Violet
|-
|<center>J120-7</center> ||  J115-3  || <center> F110 </center> ||  White-Brown
|-
|<center>J120-8</center> ||  J115-4  || <center> F109 </center> ||  White-Orange
|-
|<center>J120-9</center> ||  J115-6  || <center> F108 </center> ||  White-Yellow (yellow)
|-
|<center>J120-10</center> ||  J115-5  || <center> F107 </center> ||  White-Green
|-
|<center>J120-11</center> ||  J115-2  || <center> F106 </center> ||  White-Violet
|}
{| class="wikitable"
!<center> GI Connector/pin </center>
! Connects to 
! associated circuit wire color 
|-
|<center>J115-7</center> ||  Triac Q10 pin 1  ||  Orange
|-
|<center>J115-8</center> ||  Triac Q18 pin 1  ||  Brown
|-
|<center>J115-9</center> ||  Key pin 
|-
|<center>J115-10</center> ||  Triac Q16 pin 1  ||  Green
|-
|<center>J115-11</center> ||  Triac Q14 pin 1  ||  White-Yellow (yellow)
|-
|<center>J115-12</center> ||  Triac Q12 pin 1  ||  Violet
|}

<center>
<gallery widths=140px heights=180px perrow=5 caption="WPC-089 Power/Driver Board GI Buzz Diagrams provided by Sascha Voskuil">
File:GIBuzzBrown.jpg|<center>Brown GI String</center>
File:GIBuzzOrange.jpg|<center>Orange GI String</center>
File:GIBuzzYellow.jpg|<center>Yellow GI String</center>
File:GIBuzzGreen.jpg|<center>Green GI String</center>
File:GIBuzzPurple.jpg|<center>Violet GI String</center>
</gallery>
</center>
<center>Click on the thumbnails above for the full sized GI buzz image</center>
 
<center>The clickable images above, in an animated gif...</center>

[[File:AnimatedGIConnections.gif|center|An animated diagram of WPC-089 GI connections]]
 

[[File:J120-J121SolderPads.jpg|thumb|300px|left|Critical PCB traces for the brown and orange GI circuits that are often compromised with amateurish attempts to replace J120.]] 
Regarding poor prior rework, sometimes when J120 is replaced, the through holes at pins 7 and/or 8, are pulled causing a loss of connectivity from the board front to the board rear. This will prevent the brown and/or orange color GI circuit from working properly. Additionally, the through hole at J121, pin 6, that routes power to the 3-pin connector at J119, if pulled, will cause the cabinet GI (violet) to not light (coin door lights).
 

<li>'''Burned connectors.''' 
Over long periods of time, both the male and female GI connectors at J115, J120, and J121 often burn. 
This was especially prevalent in early WPC games like Terminator 2. 
[[File:WMS WPC Burnt GI Typical.JPG|thumb|300px|left|Typical burned connector on the output (female) side of the backbox GI on the driver board]]
[[File:BurnedJ120-121.jpg|thumb|300px|right|These female housings for J120/121 are burned so much that they are "welded" to the male headers.]]
[[File:BurnedJ120-121Rwmoved.jpg|thumb|300px|left|The connectors after removal. Get your marshmallows ready.]]
Numerous "hacks" have been employed over the years by well meaning repairmen but the only real way to fix burned connectors is to replace both the male header pins and the female housings/pins. "Trifurcon" phosphor-bronze crimp-on pins are recommended to provide a better connection at the female connector. Note that these must be phosphor-bronze (7A rating, as original). Don't buy them unless the supplier calls that out as the brass version looks the same but is only rated at 5A. If you replace burned female connectors, the male connectors are probably burned too and should be replaced. The damaged surface of the male pins will generate heat, and cause early failure of the replacement connector. Plus, the GI will be dimmer than it should be. J115 is a special case. The black Panduit connector that Williams used on many machines is far superior to any crimp pin, with a 12A rating (compared to 7A for phosphor-bronze Trifurcon pins). These, however, can be hard to find. Fortunately, they rarely burn and therefore rarely require service. Another alternative for high current connections is to use Molex MarKK series contacts (Molex part number 45570-3050) along with Molex 41695 series plugs. Although they cost more than the Trifurcon style contacts, these contacts are rated for a current load up to 13 amps.
 
WPC-089 Power/Driver Board J120/J121 connector repair parts list...

{| class="wikitable"
!<center> Qty </center>
! Part 
! Product ID 
|-
|<center>2</center> ||  11 pin .156 male header (cut to size) ||  26-48-1245
|-
|<center>2</center> ||  Connector, .156 Plug, 11 pin (Molex 41695 series) ||  09-50-8111
|-
|<center>10</center> ||  .156 Trifurcon crimp contacts for the larger gauge wires ||  08-52-0113
|-
|<center>10</center> ||  .156 Trifurcon crimp contacts for the smaller gauge wires  ||  08-52-0125
|-
|<center>2</center> ||  "Keying Pins" for Molex 41695 series plugs ||  15-04-0297
|-
|<center>1</center> ||  Crimp tool ||  1028-CT (or equivalent) 
|}
Note: Product IDs shown above can be found at http://www.greatplainselectronics.com/Category-80.asp. Other vendors may carry these same parts.
 
<li>'''Burned AC power input connector.''' There is also a 9-pin (3x3) connector between the transformer secondary and J115. This connector/pins sometimes burn and may require replacement. Check to ensure that AC power is being delivered to the power/driver board at J115.</li>
[[File:WPCGICabinetConnection.jpg|thumb|300px|left|WPC General Illumination power connection between the transformer secondary and J115 (AC power in). This picture is from a Twilight Zone, which used the newer, multicolored wires between this connector and J115 on the power/driver board.]]
*Set your DMM to AC voltage. If your DMM is not an "auto-ranging" model, expect to measure about 7 volts AC.
*Turn the game on.
*Insert one probe of your DMM (either one) into the rear of the female connector at J115, pin 3.
*Insert the other probe into the rear of the female connector at J115, pin 11.
*You should be measuring 6 to 7 VAC.
*If no voltage is present, examine the 9-pin connector between the transformer secondary and J115, pictured at left.
 
<li>'''Burned traces.''' Usually, this is a secondary problem created after the connectors burn. Visual inspection of the traces might uncover the problem, but "buzzing" them for continuity is the best practice.</li>
<li>'''Failed 2N5401.''' These don't fail very often, but are easy to test following this [[How_to..._(solder,_desolder,_"stitch",_test_transistors,_test_ICs,_etc)#Testing_a_Transistor.2C_Silicon_Controlled_Rectifier_.28SCR.29_or_Field_Effect_Transistor_.28FET.29| procedure]].</li>
<li>'''Failed resistors.''' Again, these don't fail very often but are easy to test with your DMM. Keep in mind that "in-circuit" measurements may not be reliable.</li>
<li>'''Failed 74LS374.''' This is rare too but easy to test following this [[How_to..._(solder,_desolder,_"stitch",_test_transistors,_test_ICs,_etc)#Testing_an_integrated_circuit | procedure]]. You can also test the outputs of the LS374 by probing pins 2, 5, 6, 16 and 19 with your logic probe. At full GI brightness (8), these pins should test as solid "low". At the dimmest GI brightness (1), the above referenced pins should all be pulsing "high". Additionally, pin 1 of the LS374 should always test low and pin 11 should always be pulsing "high".
</li>
<li>'''Failed Triac.''' These rarely fail. But, if you've gotten to this step in the procedure, it's time to replace the Triac. Remember, you need a 4-sector triac.</li></ol>

As these boards age it is easy to pull out the little copper hole liners that connect traces from one side of the board to the other. If you install new connector pins, be sure to check continuity from the new pins onto the board somewhere. This only takes a couple minutes and can save you a lot of time.

=====GI Lamps Not Dimming=====

[[File:WPC089BlankingTraces.jpg|thumb|300px|right|Small traces leading from the through holes of BR2's AC solder pads (pads circled) can be easily damaged, causing GI lamps to not dim. On this board revision, the upper/right through-hole has a small trace on the solder side of the board that connects to the "via" visible to the left of the through-hole. These traces lead to vias which can be seen just SouthWest of R194.]]
The primary cause of GI lamps failing to dim is broken traces at BR2, usually caused when BR2 was replaced. These traces lead to D3 and D38. Both of these traces must be intact for dimming to work as they supply the power to generate the signal to the Zero Cross circuit (ZC) which is key to dimming.

Before you go too far diagnosing the hardware, if your WPC game will not dim the general illumination, make sure that Standard Adjustment #25, "Allow Dim Illum.", is set to "YES". If set to "NO", then the GI will never dim, even during General Illumination test.

General dimming "theory of operation"...
*The driver board generates the ZC signal with the BR2, D3/D38 and U6 circuitry (different resistors).
*The ZC signal is connected to the ASIC (across the driver board, the ribbon, and then across the MPU).
*The ASIC uses the ZC signal to determine when to send the /TRIAC signal to U1 pin 11 (an 74LS374 buffer IC) as it simultaneously presents GI string enable data on the data bus.
*U1 latches GI string enable data from the MPU's data bus.
*The output of U1 forms signals T0 thru T4, which enable the TRIAC circuitry.
 

[[File:ZC_broken.jpg|thumb|300px|left|This is the ZC signal from a Doctor Who with a broken trace between the two 270 ohm resistors after D3. Dimming did not work in this example.]]
[[File:ZC_ok.jpg|thumb|300px|right|This is the ZC signal from a properly working Twilight Zone with General Illumination dimming working correctly.]] 
It is possible that D3, D38 (1N4004 diodes) or the LM339 at U6 have failed. If the ZC test point on the power/driver board is not strobing (which can be seen with a logic probe), something upstream of the test point has failed.

U6 is an LM339 comparator. The resistors around it (R16 and R17, both 230 ohm 1/4 watt) help generate the correct ZC signal. If a resistor is burned or out of spec, or if a trace is broken in the circuit (there are several "vias"), then ZC may still strobe but in an incorrect way which the ASIC doesn't recognize as the zero cross signal.

The ZC may be strobing, yet the GI still won't dim. Use a logic probe to test both sides of diodes D3 and D38 as it is necessary for both the positive going and the negative going portions of the AC sine wave to be detected. If the traces buzz out back to BR2, then suspect one side of BR2 being open. Incredibly, it is possible for the game to work correctly in all regards other than GI dimming with half of the bridge open. Odd...but it happens.

[[File:YT.png]] A video discussing this behavior can be found [https://www.youtube.com/shorts/Db_34Zou9mM here].
 

[[File:YT.png]] A video demonstrating how to "buzz" the GI circuit connections can be found [https://youtu.be/9qy2rwJ9IEM?si=VG0YxUMGJrwUwq6n here]. 

====WPC-95 General Illumination Problems====
[[File:WPC95GIToast.jpg|thumb|300px|left|The GI section of a WPC-95 driver board with 6A2 diodes installed. Note the significant burn around the diodes as well as the melted connectors and burned pins.]] 
The General Illumination circuit for WPC-95 games is very similar to WPC games. When the WPC-95 system was implemented, Williams reduced the number of "dimmable" GI circuits from 5 to 3, with 2 of the circuits being lit at all times. Within the two "always on" GI circuits, Williams placed 8 large 6A2 diodes, to create a voltage drop in the circuit which would dim the lamps slightly and presumably lengthen lamp life. However, these big 6A2 diodes create a great deal of heat. Without a heat-sink like those used on the TRIACs, the high heat they produce causes the printed circuit board and traces to burn. 
Later versions of the WPC-95 driver board replaced these 6A2 diodes with zero ohm jumpers.
 

[[File:WPC95GIJumpers.jpg|thumb|300px|left|The back side of a WPC-95 driver board with jumpers installed across the GI circuit.]]
[[File:WPC95Jumpers.jpg ‎|thumb|300px|right|Replacing the 6A2 diodes with 4 zero ohm jumpers.]] 
You can (and probably should) remove the 6A2 diodes, and either replace them with zero ohm jumpers as pictured at right, or add jumpers to the solder side of the board as pictured at left. The solution at left bypasses the diodes completely, by installing the following jumpers.

■ J103 pin 11 jumped to J105 pin 5 
■ J103 pin 12 jumped to J105 pin 6
 

<center>
<gallery widths=160px heights=280px perrow=5 caption="WPC-95 Power/Driver Board GI Buzz Diagrams provided by Sascha Voskuil">
File:Wpc95PinWikiGI-String1-Brown.png|<center>Brown GI String</center>
File:Wpc95PinWikiGI-String2-Orange.png|<center>Orange GI String</center>
File:Wpc95PinWikiGIString3-Yellow.png|<center>Yellow GI String</center>
File:Wpc95PinWikiGI-String4-Green.png|<center>Green GI String</center>
File:Wpc95PinWikiGI-String5-Purple.png|<center>Violet GI String</center>
</gallery>
</center>
<center>Click on the thumbnails above for the full sized GI buzz image</center>
 
<center>The clickable images above, in an animated gif...</center>

[[File:Wpc95PinWikiGI-1-5.gif|center|An animated diagram of WPC-95 GI connections]]
 

====Controlled Lamp Problems====

===== Twist Socket Lamp Not Lighting =====
[[file:wpc-lamp-board-twist-sockets.jpg|thumb|right|300px|A lamp board with twist sockets found in Terminator 2]]
Two things that can fail on lamp boards are individual lamp circuit diodes or the solder pads can develop "divots", where the twist sockets make physical contact with the board. To overcome the divots, simply add a little solder, and carefully reflow the solder pads. Make certain not to apply too much heat...just enough to evenly flow the solder.

With Fire!, a system 11 game, Williams started using lamp boards with .156" header connections for the lamp column and row lines. This allowed for easy removal and service of the lamp boards. However, it introduced some new problems. Because the lamp boards used were single-sided, (this was presumably a cost analysis decision), the .156" header pins can develop cold solder joints and crack due to vibration. The problem can easily be rectified by removing the old solder from the header pins and applying fresh, new solder.
 

<center>
<gallery widths=300px heights=300px perrow=2 caption="Typical issues with lamp board sockets and headers">
File:PCBMountLampDivot.jpg|<center>"Divots" in the connection pad of a "twist in" lamp.</center>
File:WPCPCBLampBoardHeaders.jpg|<center>The solder on these header pins has been reflowed nicely.</center>
</gallery>
</center>

The following actions can help debug an individual socket failure:
# Move the non-working twist socket to another spot that is working. This will test that the bulb and socket itself are working. If not, replace the bulb, try to adjust the socket's contact legs, try to clean off the contact points if they are dirty, and if all that fails, replace the twist socket.
# Move a working twist socket into the position that is not working. If the socket works, the original socket may have been the problem. If the working socket also does not work in the non-working position, there is likely a problem with that position.
# Check the connector, especially if it is an IDC connector. Sometimes a wire can pop out and lose connectivity.
# Remove the lamp board. Check the header pins for cracked solder joints and reflow the solder as necessary. Reinstall and test.
# [[General#Testing_a_Diode|Test the diodes with a multimeter]]. If any are bad, replace them. Make sure to orient the diode the same way that is indicated on the silkscreen. It's sometimes possible that a previous owner installed a diode the wrong way.
# Sometimes the pads on the lamp board that the socket makes contact with get dirty or worn enough to put a divot in the metal. Clean off the contacts, and if that doesn't improve anything, tin the pads with a thin layer of solder.
# If none of this was successful, test for continuity between the lamp board and the driver board.
# If wiring continuity checks out, [[#Controlled_Lamp_Operational_Description|troubleshoot the issue like any other controlled lamp]].
 

===== Controlled Lamp Operational Description =====

WPC feature lamps are controlled from the WPC MPU and ultimately enabled via the driver board. The control signals are as follows.
#The 68B09EP places a data bit pattern on the data bus. This represents the lamp column to be strobed.
#The bit pattern is conveyed to the driver board via the ribbon cable between J211 on the MPU and J113 on the driver board.
#U9 on the driver board (a 74LS240) buffers the column bit pattern for U18 (a 74LS374).
#The ASIC on the MPU asserts the /LMP COL signal which "clocks" the data into U18 by pulsing pin 11.
#U18 outputs are connected to the ULN2803 at U20, which inverts the signal and enables one of eight TIP-107 Darlington transistors (Q91 thru Q98) that enable 18VDC to flow to the enabled column. This completes the column "strobe" portion of lamp matrix operation.
#The 68B09EP places a data bit pattern on the data bus. This represents the lamp rows to be strobed.
#The bit pattern is conveyed to the driver board via the ribbon cable between J211 on the MPU and J113 on the driver board.
#This bit pattern data is presented to four 74LS74s (Dual D-Type Flip-Flops) at U10 thru U13. This sets up a path to ground for the 18V lamp matrix power for each row enabled by the bit pattern
#The ASIC on the MPU asserts the /LMP ROW signal which "clocks" the data into U10 thru U13 via their "reset" signal inputs.
#The (not) Q signal of each 74LS74 enables one of eight TIP-102 Darlington transistors (Q83 thru Q90) that provide the actual path to ground (through a .22 ohm 1 watt resistor) for the 18V lamp matrix power.
#At this point, power flows from the enabled column circuitry, through the game wiring to the lamps, then through the row circuitry to ground for the rows that are enabled.
#The row enable signal is switched off when the LM339 comparators at U15 and U16 detect a voltage rise above the reference voltage present at pins 5, 7, 9, and 11 of both LM339s, via the "set" signal of each 74LS74 (U10 thru U13).

This process repeats itself over and over with the MPU cycling through columns 1 thru 8 while enabling specific rows, lighting lamps at the intersection of the enabled column and the enabled rows.

[[Image:WPC089AlkalineDamagedLampMatrixEnable.jpg|300px|thumb|right|The column trace between the J211 dual row header and the ASIC chip socket (pin 63) clearly corroded away. The lamp row trace is immediately below the column trace and unaffected.]]
There are many possible causes for lamp matrix malfunctions. Some reasons, in order of probability are:
#Lack of 18V lamp matrix power. If LED6 is not lit, or TP8 shows other than 18V, "buzz" F114 for continuity with your DMM. If F114 is blown, test BR1 using the method specified [http://www.pinwiki.com/wiki/index.php?title=General#Testing_a_Bridge_Rectifier here].
#Failure of the row (TIP-102) or column (TIP-107) drive transistor. Both of these are easily diode tested and compared to the other 7 row/column drive transistors.
#For a column failure: Failure of the ULN-2803 at U19. U19 works the same as U20 in the switch matrix, providing a periodic pulse to all columns.
#For a row failure: Failure of a 74LS74 at U10/11/12/13. Again, these parts can either be diode tested for, better yet, use a logic probe to see if they are delivering the necessary pulses. Compare the operation of similar pins.
#Failure of the associated .22 ohm 1 watt resistor in the path between 18VDC lamp matrix power and ground (R150 for example).
#Poor connections between J211 on the MPU and J113 on the power/driver board. Sometimes, reseating the ribbon cable on both ends will "fix" the issue. Replace the ribbon cable and examine the dual row headers if the problem becomes chronic.
#Prior work on the power/driver board. The data bus runs completely across the power/driver board, stopping in at several 74LS374s (U1 thru U5) along the way. The signals pass through the board from component side to solder side at U9. If the same column and row of the lamp matrix are not lighting (i.e. column 5, row 5), it's a good bet that the signal for that row/column is compromised in the area of U9. The traces at each IC are delicate and it's tough for most hobbyists to remove a 20 pin IC without damaging the traces. It's particularly vexing to encounter a problem where a data signal is held low or high by one of the 74LS374s since each data signal is connected to all of them and even using [diode test] sometimes can't identify the faulty IC. Some techs will cut the data signal pin close to the PCB for a 74LS374, using the process of elimination to identify the culprit (not recommended). Enough said, but it's easily seen that power/driver boards can be damaged quite easily by the novice. Send it to a pro.
#Fatigued connections between the ASIC on the MPU and it's chip socket. Since the ASIC provides critical enable signals for the lamp matrix, reseating or [https://www.greatplainselectronics.com/Information.asp?region=139 retensioning] these pins is reasonable course of action. [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Removing_the_ASIC Use a PLCC removal tool] to safely remove the ASIC without damaging the socket.
#Failure of any of the ICs noted above. Each of these ICs can be tested with a DMM set to [http://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit diode test]
#Corrosion on the MPU that might have compromised the enable signals, as seen in the picture at right. Corrosion can and will attack under the header pins at J211 on the MPU.
 

'''Quick Test of Lamp Column Transistors'''

[[Image:CheckingLampColumnDriveTransistors.jpg|300px|thumb|left|"Quick Test" for a shorted lamp column transistor.]]
If the game has an entire column of lamps locked on, there is a good chance that a lamp column transistor has shorted. Testing for this condition is very simple. Set your DMM to continuity. Touch one probe to the 18V lamp matrix test point as pictured at left. Touch the other probe to the tab of each of the TIP-107 transistors. Any that "buzz" are shorted and will need to be replaced.
 

'''General Lamp Matrix Testing'''

The control logic for the WPC lamp matrix can be tested by connecting a spare lamp using two jumper wires. The following sections show the separate procedures for testing the lamp matrix columns and rows. The example applies to WPC-089 power/drive boards. The procedure is the same for WPC-95 power/driver boards, but the connector designations and transistor numbers differ. Images authored by Sascha Voskuil, used with permission)

 
<center>Testing a working lamp matrix circuit on a WPC-95 Power/Driver board
[[File:LampMatrixGeneralTesting.gif|center|General testing of the lamp matrix circuit on a WPC-95 Power/Driver board. All columns operating normally.]]

 
Column 4 shorted in the lamp matrix circuit on a WPC-95 Power/Driver board
[[File:LampMatrixColumn4Shorted.gif|center|Testing the lamp matrix circuit on a WPC-95 Power/Driver board that has column 4 shorted.]]

 
Column 4 inoperative in the lamp matrix circuit on a WPC-95 Power/Driver board Note: In this animation, columns 4 and 2 are inoperative. 
[[File:LampMatrixColumn4Inop.gif|center|Testing the lamp matrix circuit on a WPC-95 Power/Driver board that has column 4 open (inoperative).]]
</center>
 

We provide this section for completeness knowing that WPC games offer independent lamp row and column tests as part of the diagnostics. 

'''Testing the lamp matrix columns:'''

[[Image:Placeholder.jpg|300px|thumb|right|Jumper connection for testing lamp matrix columns.]]
Use the following procedure to test the TIP-107 transistors that drive the lamp matrix columns. Note that a diode is not needed for these tests since it's function is to block current flow and prevent interaction between the lamps in the matrix. In this test we are connecting a single lamp at a time.

#Remove the backglass and open the insert to get access to power/drive board connectors J133/134/135 (row) and J136/137/138 (column).
#Unplug all connectors with red or yellow wires leading to them. These are the lamp matrix connections (lower right corner of power/driver board)
#Turn the game on and start "All Lamps" test in the Test/Diagnostic Menu.
#Clip one end of the test jumper to J137 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to J133 pin 1, the rightmost pin on the connector
#The test lamp should flash to indicate that the column driver is working.
#Repeat the test for the pins 2 through 9 on J137. There is no pin 8 as it is the key.

If a column doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test.

The following table shows the lamp number and driving transistor for each of the column pins.
{| class="wikitable"
!   Pin   
!Wire Colors
!Lamp number
!Transistor number
|-
|<center>J137-1</center> || <center>Yel-Brn</center> || <center>1</center> || <center>Q98</center>
|-
|<center>J137-2</center> || <center>Yel-Red</center> || <center>9</center> || <center>Q97</center>
|-
|<center>J137-3</center> || <center>Yel-Orn</center> || <center>17</center> || <center>Q96</center>
|-
|<center>J137-4</center> || <center>Yel-Blk</center> || <center>25</center> || <center>Q95</center>
|-
|<center>J137-5</center> || <center>Yel-Brn</center> || <center>33</center> || <center>Q94</center>
|-
|<center>J137-6</center> || <center>Yel-Blu</center> || <center>41</center> || <center>Q93</center>
|-
|<center>J137-7</center> || <center>Yel-Vio</center> || <center>49</center> || <center>Q92</center>
|-
|<center>J137-8</center> || <center>Key Pin</center> || <center> </center> || <center> </center>
|-
|<center>J137-9</center> || <center>Yel-Gry</center> || <center>57</center> || <center>Q91</center>
|}

'''Testing the lamp matrix rows:'''
[[Image:Placeholder.jpg|300px|thumb|right|Jumper connection for testing lamp matrix rows.]]
Use the following procedure to test the TIP-102 transistors that drive the lamp matrix rows.

#Remove the backglass and open the insert to get access to power/drive board connectors J133/134/135 (row) and J136/137/138 (column).
#Unplug all connectors with red or yellow wires leading to them. These are the lamp matrix connections (lower right corner of power/driver board)
#Turn the game on and start "All Lamps" test in the Test/Diagnostic Menu.
#Clip one end of the test jumper to J133 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to J137 pin 1, the rightmost pin on the connector
#The test lamp should flash to indicate that the column driver is working.
#Repeat the test for the pins 2 through 9 on J133. There is no pin 3 as it is the key.

If a row doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test.
The following table shows the lamp number and driving transistor for each of the row pins.

{| class="wikitable"
!   Pin   
!Wire Colors
!Lamp number
!Transistor number
|-
|<center>J133-1</center> || <center>Red-Brn</center> || <center>1</center> || <center>Q90</center>
|-
|<center>J133-2</center> || <center>Red-Blk</center> || <center>2</center> || <center>Q89</center>
|-
|<center>J133-3</center> || <center>Key Pin</center> || <center> </center> || <center> </center>
|-
|<center>J133-4</center> || <center>Red-Orn</center> || <center>3</center> || <center>Q88</center>
|-
|<center>J133-5</center> || <center>Red-Yel</center> || <center>4</center> || <center>Q87</center>
|-
|<center>J133-6</center> || <center>Red-Grn</center> || <center>5</center> || <center>Q86</center>
|-
|<center>J133-7</center> || <center>Red-Blu</center> || <center>6</center> || <center>Q85</center>
|-
|<center>J133-8</center> || <center>Red-Vio</center> || <center>7</center> || <center>Q84</center>
|-
|<center>J133-9</center> || <center>Red-Gry</center> || <center>8</center> || <center>Q83</center>
|}

===== Lamp Issue Caused by Connecting "Growth" Connectors =====
[[File:WPCErroneousConnection-1.jpg|300px|thumb|left|A misplaced connector on Judge Dredd. Image courtesy of Chuck Sanderson, CP Pinball]]
[[File:WPCErroneousConnection-2.jpg|300px|thumb|right|The connector, not connected, as it should be.]]
[[File:LampMatrixHeadache.jpg ‎|300px|thumb|left|Lamp Matrix failure "map" created when J136 is erroneously connected on Judge Dredd]]

An issue that seems to come up fairly often is caused by literally placing a square peg into a round hole.

The images shown here from a Judge Dredd shows a "growth" connector wired from the factory that was never used during production. It happens to be in the proximity of J136, a lamp matrix connector and the wires are lamp matrix wires (colored red and colored yellow). One could almost be forgiven for forcing the female housing onto J136 even though the connector types are different.

With this connector in place, all kinds of lamp matrix havoc ensues as shown in one lamp matrix "error map" shown at left.

The solution is simple. Remove the connector.

All images provided by Chuck Sanderson, [https://cppinball.com/ CP Pinball]
 

===Switch Problems===

Switches in WPC games fall into two categories, those within the switch matrix, and "direct" switches.

====Diode and Switch Matrix Wiring Orientation on a Microswitch====
[[File:Submicro Switch Wiing.jpg|300px|left|thumb|Typical wiring for any Microswitch]]
First and foremost, all switches located in the switch matrix MUST have a diode. Secondly, the diode has to be installed in the correct orientation. If a diode is installed "backwards", the end result my be that all of the switches in that particular row get triggered or even stranger issues occur. Finally, the diode legs must not be connected to any of the other wires or terminals of the switch, or the switch will funk up the switch matrix.

Here is the correct orientation for the wiring and the diode on a microswitch. The white wire w/ trace and non-banded side of diode is connected to NC terminal. The banded side of diode is connected to common terminal. Finally, the green wire w/ trace is connected to NO terminal.
 

====Built-in Switch Testing====
WPC games monitor switch closures as the game is played. If a switch is not activated after a certain number of balls (usually 30, but will vary depending on the switch in question), the game will show the "credit dot", an indication to the operator that a switch may be faulty. Some switches are not often closed (like switch 55 located in the White Water pop bumper garden) and some switches simply aren't hit by rookie players (like the upper exit to the Twilight Zone mini playfield). Some switches will be marked non-operational immediately after a certain event where the switch is known to have been activated (switches related to The Shadow's brick wall drop target are one example; any error in the lock sequence causes the credit dot to light immediately). 

There is a table held in RAM that contains counters for all monitored switches. Each ball served decrements the counter for each switch; as soon as that switch is hit on the playfield, the counter is reset to the initial value. The credit dot gets lit when any counter for any monitored switch goes to zero. Switches such as flipper optos are set to very low initial values, as flippers are hit on every ball. It would have been possible to have higher values set for switches that would occasionally be activated but not often by novice players as noted above, however this aspect of the programming was rarely if ever used. 

When a credit dot is lit, often the game will offer "switch compensation", which was a Williams' patented feature, that allowed a nearby or alternate switch to achieve the same result as hitting the original, marked non-operational, switch. This enabled a game with faulty switches to still be played close to the original gameplay. Sometimes the faulty switch will auto-clear itself when activated, but more often than not, the fault would have to be cleared manually. To clear a switch manually, enter the "Switch Edges" test (as described below), and manually activate the switch. If the switch in question is functioning properly, activating the switch will remove the credit dot. 

The first action to be taken is to enter diagnostics. The game will indicate the reason(s) for the credit dot on the display, upon pressing the enter button on the coin door to receive a test report. 

Since the normal switch matrix is 8 by 8, games like Twilight Zone, Star Trek: The Next Generation, and Indiana Jones employ a 9th column of switches. These switches are tested via a dedicated switch test tied to the playfield feature. An example is the Star Trek: The Next Generation cannon switches. 

=====T.1 Switch Edges Test=====
[[file:WPCSwitchTestExample.jpg|400px|thumb|left|An example switch matrix display, this one from Twilight Zone. Note the opto switches in column 7 (for example) are shown as boxed dots.]]
Switches can be tested by entering Test T.1, Switch Edges. Switch Edges Test presents an 8 by 8 switch matrix grid with one or two switch columns outside of the matrix. The additionally columns are for dedicated switches. The left column is for switches located on the coin door (all WPC games), and the right column is for flipper cabinet and flipper EOS switches (WPC games which use a Fliptronics board - Addams Family and newer). Open switches show as a simple dot on the DMD. Closed switches show as a boxed dot on the DMD. Microswitches and leaf switches will show as a dot when open. Optos will show as a boxed dot when the opto beam is not being broken. The last closed switch name and number will be shown on the display along with the two wire colors that are connected to that particular switch. While in switch edges test, manually closing properly operating switches will be shown on the display. 

=====T.2 Switch Levels Test=====

====Direct Switch Problems====

'''Direct switch operation'''

Direct switches include:
*Left coin chute
*Center coin chute
*Right coin chute
*4th coin chute
*Service Credits/Escape (referred to as "escape" here)
*Volume down/Down
*Volume up/Up
*Begin Test/Enter

Direct switches are not part of the WPC switch matrix. All of the direct switches are located on the coin door, and connect to the MPU at J205. The MPU senses these switches individually, and apart from the switch matrix. Therefore, isolation diodes are not used with direct switches.

Normally, with the switch open, the LM339s at U16 and U17 compare 12V (supplied on the MPU to both the switch and to the LM339) with 5V (as a comparison level) and signals the 74LS240 at U15 that the switch is open. When the switch closes, it shorts the 12V to ground and the comparison at the LM339 then indicates to U15 that the switch is closed. U15 is "clocked" by pin 48 of the ASIC (SW DIR), causing U15 to present its data to the data bus. The 6809/ASIC "debounces" the switch. Debouncing is not a factor to be considered here and doesn't factor in switch testing at all.

'''Direct Switch Pinout at J205 for both WPC and WPC-S MPUs''' 
Notes: 
:J205, pin 5 is the "key" pin.
:J205, pin 10 provides ground (black wire)
:J205, pin 11 is unused
:J205, pin 12 is an "enable" back to the coin door interface board 

{| class="wikitable"
!Signal
!Wire color at J205
!MPU pin
!Diode
!LM339 & input pin
!U15 input pin
|-
|Left chute || <center>orange/brown</center> || <center>J205-1</center> || <center>D15</center> || <center>U17-5</center> || <center>11</center>
|-
|Center chute || <center>orange/red</center> || <center>J205-2</center> || <center>D16</center> || <center>U17-7</center> || <center>13</center>
|-
|Right chute || <center>orange/black</center> || <center>J205-3</center> || <center>D17</center> || <center>U17-11</center> || <center>15</center>
|-
|4th chute || <center>orange/yellow</center> || <center>J205-4</center> || <center>D18</center> || <center>U17-9</center> || <center>17</center>
|-
|Escape || <center>orange/green</center> || <center>J205-6</center> || <center>D11</center> || <center>U16-9</center> || <center>2</center>
|-
|Down || <center>orange/blue</center> || <center>J205-7</center> || <center>D12</center> || <center>U16-11</center> || <center>4</center>
|-
|Up || <center>orange/violet</center> || <center>J205-8</center> || <center>D13</center> || <center>U16-7</center> || <center>6</center>
|-
|Enter || <center>orange/gray</center> || <center>J205-9</center> || <center>D14</center> || <center>U16-5</center> || <center>8</center>
|}

'''Debugging direct switch problems'''

To discover the problem as quickly as possible, we'll divide the problem into smaller pieces. We must first determine if the problem is on the MPU board or the problem lies with the wiring to the coin door and/or the specific switch. If your MPU has obvious alkaline damage at U15, U16, or U17, address the alkaline damage first.

Begin testing with the game OFF.

'''Isolate the problem to the MPU or to the game wiring/switch '''
#Remove connector J205 from the MPU.
#Build a jumper wire with alligator clips on both ends.
#Clip one end of the jumper wire to the game's ground braid in the game head.
#Turn the game on
#Carefully touch the other end of your jumper wire to the appropriate pin on J205 as shown in the table.
#If the MPU carries out the function of the switch, the problem is not on the MPU.
#If the MPU does nothing, the problem is on the MPU.
#Skip to the appropriate section below.

'''Identifying problems NOT on the MPU '''

'''Test the direct switch's path to ground '''
#Your game should still be turned off.
#DMM set to continuity.
#Clip the black lead of your DMM to any game ground, like the lockdown bar or ground braid.
#Red lead on the solder joint between the switch and the black wire that provides ground.
#You should hear "tone". If not, further diagnose the break in the black wire between the solder joint and game ground.

'''Test the direct switch itself '''
#Black lead of your DMM still clipped to game ground.
#Red lead on the solder joint opposite the black wire (or bare wire jumper) of the switch under test.
#Depress the switch. You should hear "tone". If not, the switch is defective and not "making". See the section below that describes cleaning these switches.

'''Test the signal path to the MPU '''
#Clip the black lead of your DMM on the solder joint opposite the black wire (or bare wire jumper) for the switch under test.
#Remove the connector plug at J205 from the MPU.
#Red lead on the appropriate pin of J205 for the switch under test. See the table above. It's easiest to access the pin through the rectangular hole in the back of the connector where the pin's "tang" snaps in.
#You should hear "tone". If not, there is a discontinuity in the wire between the direct switch and J205. Note that the coin door interface board is between these two points. The coin door interface board is a "pass-through" for these signals and rarely causes a problem. Still, reseating connectors J1, J3, and J4 on the coin door interface board might uncover the problem. More likely, the wire between J1 on the coin door interface board and J205 has a break in it.

'''Identifying problems on the MPU '''

'''Test the signal path through J205 and onto the MPU '''
J205 is right below the battery holder and as such, sometimes receives the unwanted gift of dripping alkaline from depleted batteries. Carefully examine both the male and female connections of J205 for alkaline "greenies". Assuming no alkaline damage... 
#Begin with your game turned off.
#Connect J205 to the MPU.
#Clip the black lead of your DMM to the solder joint opposite the black wire (or bare wire jumper) for the switch under test.
#Red lead on the banded end of the appropriate diode shown in the table above.
#You should hear "tone". If not, there is either a problem with the physical connection at J205 or the alkaline "greenies" are sneakier than you gave them credit for. Re-examine J205 and the surrounding area of the board for alkaline damage. The traces from the switch connectors are very small and it takes very little alkaline damage to compromise them. You may also re-pin the female side of J205.

At this point, a logic probe would be the best tool to use. You can pick up 5V power for your probe across the electrolytic cap at C31 which is immediately to the right of the battery holder. Black lead on the negative side (top of the cap). Red lead on positive side (bottom). The board is silkscreened with polarity markings. Set the logic probe to "CMOS" test mode, as you will be measuring 12VDC.

If you don't already have a logic probe, you should. Although for this test, you can still get by with your trusty DMM. Clip the black lead of your DMM to game ground. The ground braid in the head is a good place to pickup ground at this point. Set your DMM to DC volts.

'''Test the LM339 inputs '''
#Start with the game turned off.
#Again, set your logic probe to "CMOS"
#Clip one end of your jumper wire to the appropriate pin of J205. Leave the other end of your jumper wire unconnected, but handy as you'll touch it to ground later.
#You now need to turn the game ON.
#Measure the signal at the appropriate LM339's appropriate pin shown in the table above. Either place your logic probe on the pin or place the Red lead of your DMM on the pin. The signal should measure high (or about 12VDC with your DMM).
#Now, with your other hand, touch the free end of your jumper wire to the ground braid in the backbox as you observe the results.
#You should see the signal transition to low. If you still measure high, then the pin isn't being grounded correctly. Candidates are a failed diode/resistor in the circuit, the board trace between the diode and the LM339 is compromised, or a badly failed LM339.

'''Test the LM339 outputs/74LS240 (U15) inputs '''
#Set your logic probe back to TTL as you will be measuring 0 - 5V signals
#Measure the signal at the appropriate pin (see table) of U15. The signal should measure high (or about 5VDC with your DMM).
#Touch the free end of your jumper wire to the ground braid in the backbox as you observe the results.
#You should see the signal transition to low. If you still measure high with the jumper wire grounded, then either the LM339 outputs have failed, the board trace between the LM339 and U15 is compromised, or the 74LS240 has failed and is corrupting the signal. You can test U15 using the procedure in the "How to..." section of PinWiki, [https://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit here].

The output side of U15 can't be tested effectively since that is the processor/ASIC data bus and should be constantly and irregularly changing states.

If you've followed this process step-by-step, you should have identified the problem with the signal and will be able to effectively perform the appropriate repair.

'''Cleaning direct switches'''

Coming soon...will describe disassembly and cleaning...
Sometimes, several rigorous open/close cycles will "clean" corrosion from the switch.

====Switch Matrix Problems====

'''Isolate the problem to the MPU or to the game wiring/diodes/switches '''

Follow these steps to determine if the switch matrix problem is on the CPU or somewhere in the game wiring.

#Remove connectors J206/J207, J208/209 and J212 from the bottom of the CPU (J206 and J207 are electronically the same and J208 and J209 are electronically the same).
#Clip one lead of a test jumper to pin one of J207 making sure you don't touch any of the nearby pins on J207.
#Power the game on, and enter Switch Edge test (you've left J205 on the CPU so the diagnostics switches still work).
#Touch the other end of the jumper to pin one on J209, then pin two and so on. You should see (and hear) the CPU indicate that switches #11, #12, #13, etc. are being "made" as you touch the pins of J209. You should *never* see multiple switches being made.
#Move the jumper from J207 pin 1 to pin 2. Re-test to every pin on J209, listening for the machine to read every switch as closed. Continue in a similar manner testing each pin of J207 to every pin in J209.

The following images, provided by Sascha Voksuil, grapically depict the above tests of the on-board switch matrix circuitry with a jumper wire. A diode is not required since the test jumpers directly from a single pin to a single pin. Remember, the purpose of switch diodes is switch isolation. Also, have no fear conducting this test. Unless you connect one end of the wire to high voltage, nothing can be damaged.

[[File:Switch matrix test ROWs1-8 with COL1.gif|left]][[File:Switch matrix test COLs1-8 with ROW1.gif|right]]
 

If only one switch shows on the Switch Edge test for each pin combination, then the CPU's switch matrix is working properly and you can confidently assume that any switch problems lie elsewhere. Possibilities include a shorted wire, bad/broken/shorted diode, bad under playfield opto board, bad coin door interface board, etc. If the problem is observed with row 2 of the switch matrix, and you're game has a "-1 Power/Driver" board installed (the one with the flipper power relay), it is possible that one/both of the 4N25 opto-isolators on the power/driver board have failed. These opto-isolators communicate flipper switch closures for pre-FlipTronics games.

If multiple switch closures are reported when you touch one pin of the connector, or if the CPU reports a row or column short, then there is a fault with the switch matrix circuitry on the CPU board itself. Be aware that an additional fault may still be present on the playfield. Switch matrix chips do not simply blow for no reason!

<center>
<gallery widths=300px heights=300px perrow=3 caption="Blown ULN2803 (U20) Examples">
File:BlownULN2803.jpg|<center>An obviously blown ULN2803 (U20) caused by shorting 50V coil power to the switch matrix. Ouch!</center>
File:WPCBlownULN2803.jpg|<center>Another obviously blown ULN2803...happens all the time...Don't work on your game with power on.</center>
File:WOCBlownU14.jpg|<center>Another obviously blown ULN2803...the HV jolt also took out U14, a 74LS374 which buffers the ULN2803 from the processor data bus.</center>
</gallery>
</center>

Catastrophic Failure of ULN2803 or Other Switch Matrix Parts

[[Image:CoilLugShortedToMetal.jpg|300px |thumb|left|Example jumper connection for testing the switch matrix. Image courtesy of PinSider "sturner".]]
[[Image:CoilWrapperRubAE-23-800.jpg ‎|300px |thumb|right|A coil wrapper that has rubbed through to the copper windings due to long term vibration against a loose screw used to secure the coil bracket. This coil is from the "Thing Kickout" in The Addams Family. It electrified the entire "thing" mechanism box and caused the ULN2803 to be destroyed. Image courtesy of JT Amusements.]] 
One fairly common reason that a ULN2803 or other switch matrix circuitry may blow is a short to coil power. In the picture at left, the coil that actuates the "Bridge Diverter" on the game Twilight Zone, is touching the coil bracket on one side. Since coil power is present at both coil lugs (which is normal), a coil lug touching metal will conduct coil power to that metal. In this case, the coil bracket touches the bridge diverter piano wire and then the coil diverter and then the entire wireform. If a switch matrix solder tab or switch blade metal shorts to the wireform, poof! Get ready to replace the ULN2803.

Another way for HV to destroy the ULN2803 and other switch matrix circuitry is shown at left. Here, the coil wrapper has worn through, and then the enamel coating on the coil winding rubbed away, causing a short of coil power to the coil bracket. Just as the instance above showed, this places coil power onto the coil bracket and anything touching it, including switches.
 

===== MPU Circuitry Switch Matrix Problem Diagnosis =====

====== Quick Switch Column Strobe Testing ======

[[File:WPCSwitchColumnStrobeBenchTest.jpg|300px |thumb|left|Testing the switch column strobes quickly with a logic probe. The picture also shows a convenient place to connect logic probe power leads.]] 
A quick way to test that switch column strobes are working properly, is to use a logic probe as shown in the picture at left. Each pin of J206/J207 (all WPC MPU versions) should be pulsing high. 

====== Further MPU Circuitry Diagnosis ======

The following image (authored by Sascha Voskuil, used with permission) will help diagnose particular ICs at fault on the MPU.
[[File:WPC-089MPULayout.jpg|300px|thumb|left|Color Coded Switch Matrix Circuitry.click image to enlarge]] 

Let's use the diagram above to walk through a simple "on board" switch matrix issue.

A board presented with very slight alkaline damage to U20, the ULN2803. After socketing, and replacing the ULN2803, column 3 still failed to strobe. We used out logic probe to determine that pin 16 of U20 was strobing. Therefore, there MUST have been an on board fracture of the trace. Setting our DMM to continuity, and buzzing between J206 pin 3 (marked with a gray "3" in the diagram) and U20 pin 16 failed. Moving our probe from J206 pin 3 to the junction of R69 and C13 (also marked with a gray "3" in the diagram) succeeded. However, buzzing between the junction of R69/C13 and U20 pin 16 succeeded. Using this information, we must conclude that the discontinuity in the trace was between J206 pin 3 and the junction of R69/C13.

[[File:WPCSwitchMatrixCorrodedTraceAnnotated.jpg|300px|thumb|left|A look under connector J206 showing alkaline corrosion damage. This caused column 3 of the switch matrix to malfunction.]]
[[File:WPCSwitchColumnOpenTrace.jpg|300px|thumb|right|Another trace destroyed by prior alkaline corrosion that had seeped under column header connector.]] 
The picture at left shows the problem. Once the J206 header was removed, we could see that alkaline had dripped onto the connector and leached down to the solder joint. The corrosion etched enough of the trace away to prevent connectivity.

The image at right shows yet another example of a switch column trace eaten away by alkaline corrosion.

[[image:YT.png]] A YouTube video demonstrating diagnosis of this issue can be found [https://www.youtube.com/watch?v=EFqM21DR438&t=240s here]
 

[[File:WPCSwitchMatrixHeaderCorrosion.jpg|300px|thumb|left|A different board, with a similar problem at the header pins...]]
[[File:WPCSwitchMatrixConnectorCorrosion.jpg|300px|thumb|right|...and the matching female housings.]] 
The picture at left shows another WPC-089 MPU board with a similar problem, but much worse. This board was the victim of dripping alkaline which invaded the trace which runs under the "C17" label to J206-9 and J207-9.

The picture at right shows the female connector housings that were the victim, and transportation medium, for the alkaline corrosion. The connector on the left required repinning. The connector on the right showed only light damage which was cleaned up with a vinegar swab.
 

[[File:CorrodedWPCConnector.jpg ‎|300px|thumb|left|Corrosion...]]
[[File:ImprovedSwitchMatrixDiagram.jpg|300px|thumb|right|Switch Matrix Circuit Operation. Note: Colors are coordinated with the prior diagram (authored by Sascha Voskuil, used with permission). Click image to enlarge.]] 
Another clear example of a connector requiring replacement is shown at left.
 
[[File:CorrodedWPCConnector1.jpg ‎|300px|thumb|left|More Corrosion...this one from a SlugFest]]
 

===== Switch 11 or Switch 12 Reported as Closed With All Switch Matrix Connectors Removed =====
[[File:4N25Failed.jpg|300px|thumb|left|In this image, the switch matrix connectors have been removed yet switch 11 is shown closed. One of the two 4N25 opto-isolators has failed.]]
A seemingly impossible behavior can be caused by a failed 4N25 Opto Isolator on a "-1" version of the WPC Power/Driver board including RottenDog Power/Driver boards. After removing all switch matrix connectors (not the direct switch connector) from the MPU, switch 11 and/or switch 12 will be reported as closed. This can also lead to all of column 1 being reported closed when any switch is closed outside of column 1. All of the column that switch is in will also be reported as closed.

The 4N25s can be tested as described below.

Another quick test is to remove the ribbon between the MPU and the Driver board. This prevents the driver board from reporting closed switches.
 

===== Cabinet Flipper Switch Detection Problem Diagnosis for Pre-FlipTronics Games =====

[[File:WPCOptoIsolators.jpg|300px|thumb|right|Dual 4N25 Opto Isolators on the "-1" version of the WPC Power/Driver board can be seen in the top center of this picture (two 6 leg ICs at U7 and U8).]]
Pre-FlipTronics games detect closure of the flipper cabinet switches via two 4N25 Opto Isolators on the "-1" version of the power/driver board. If the "cursor" can't be moved during entry of HSTD initials or if the cabinet flipper buttons don't control video mode correctly, there is a good chance that one/both of the 4N25 opto isolators is shot. Games that shipped with the "-1" Power/Driver board include:
*Funhouse
*Harley-Davidson
*The Machine: Bride of Pin*Bot
*Gilligan's Island
*Slugfest
*Terminator 2: Judgement Day
*Hurricane
*Party Zone
 

[[File:WPCEarly-1PowerDriverBoard4N25.jpg|457px|thumb|left|Illustration provided by, and used with the permission of, Sascha Voskuil aka "Zaza"..]] 
The image at left illustrates the switch matrix connection between the 4N25 Opto Isolators on the Power/Driver board and the MPU board.
 

[[File:WPCSwitchRowSchematicError.jpg|457px|thumb|left|Illustration provided by, and used with the permission of, Sascha Voskuil aka "Zaza".]] 
Note that some revisions of the WPC schematics contain an error, as illustrated by the image at left.
 

Fortunately, testing an opto coupler is simple using the diode test function provided by most DMMs. Set the DMM to diode test, compare results against those pictured below (this test conducted on a 4N25 contained on a System 11 Interconnect Board).

<center>
<gallery widths=300px heights=300px perrow=4 caption="Testing a 4N25 Opto Coupler">
File:4N25Internal.jpg|<center>The internal schematic of the 4N25. Pins 1 and 2 connect to an internal diode (LED). Pins 4 thru 6 connect to a PNP photo transistor.</center>
File:4N25Test3.jpg‎|<center>Testing the diode connected to pins 1 and 2. Red on pin 1, black on pin 2</center>
File:4N25Test2.jpg‎|<center>Testing part of the photo transistor. Black on pin 5, red on pin 6</center>
File:4N25Test1.jpg‎|<center>Testing part of the photo transistor. Black on pin 4, red on pin 6</center>
</gallery>
</center>
 

====== Special Note regarding RottenDog Power/Driver boards manufactured prior to February, 2012 ======

[[File:WPCRottenDog4N25Error.jpg|300px|thumb|left|Illustration provided by, and used with the permission of, Sascha Voskuil aka "Zaza".]] 
RottenDog aftermarket power/driver boards manufactured prior to February, 2012 contain a trace layout/connection error that exchanges the function of the two 4N25 Opto Isolators on the board. That is, the 4N25 that should report a left flipper closure actually reports a right flipper closure, and vice-versa. This error can be corrected via two cuts and two jumpers, as illustrated in the image at left.
 

[[File:WPCRottenDog4N25ErrorCorrected.jpg|300px|thumb|left|Image provided by, and used with the permission of, PinSider "troxel".]] 
Shown at left is the correction implemented by PinSider "troxel".
 

[[File:WPCRottenDog4N25ErrorCorrected1.jpg|300px|thumb|left|Image provided by, and used with the permission of, PinSider "troxel".]] 
The same image, annotated by Pinsider "zaza", calls out the need for caution when making this mod. As can be seen, 75VDC is present in the area. A better implementation might be to route the jumper wires around the 4N25 instead of under it.
 

==== WPC95 Flipper Cabinet Switch Processing====

[[File:WPC95CabinetSwitchCorrosion.jpg|300px|thumb|left|Corrosion between pins 9 and 10 on this WPC-95 MPU caused a short between cabinet flipper switch circuits resulting in both flippers actuating when either cabinet switch was closed.]]
[[File:J212Corrosion.jpg|300px|thumb|right|Corrosion on some of these pins caused erratic cabinet switch operation.]] 
The WPC-95 system implementation moved the cabinet flipper button and EOS switch sensing from the FlipTronics II board to the MPU board. Simple voltage level comparison via LM339s senses shorts to ground for those switches. The connector that cabinet switch wiring is connected to (J212) is directly below the battery holder where leaky batteries can "drip" onto the connector, corroding both under the connector and the pins on the connector. Corrosion can cause many odd problems. If this happens, the corrosion can cause the flipper buttons to be sensed intermittently and/or incorrectly.

Pictured at left is one case of corrosion impacting flipper operation. The corrosion caused the circuit to sense that both of the cabinet flipper buttons had been pressed when only one had been pressed. Standard alkaline corrosion cleanup takes care of this issue.
 

====Opto Switches====

=====Basic Operation=====
Williams opto switches are comprised of a "transmitter" and a "receiver" opto, which are each unique parts. This is different from later Sega and some Stern game systems where the optos that serve as transmitter and receiver are identical.

The transmitter opto is housed in a white plastic frame. It is powered by unregulated 12VDC. If the opto is good, measuring either solder joint of the opto should read about 12VDC as long as the game is turned on.

Note that the ball trough uses these opto transmitters also. Orient the ball trough transmitter flat side as is silkscreened on the board.
{| border="0"
|[[file:OptoTransmitter.jpg|300px|thumb|left|The solder side of a typical Williams opto transmitter.]]
|[[file:OptoTransmitterLED.jpg|300px|thumb|right|The component side of a typical Williams opto transmitter. When replacing the opto, orient the flat side toward the "K" (equivalently, orient the "short" leg of the opto toward the "K")]]
|[[file:UOptoGuts.jpg ‎|300px|thumb|right|The "guts" of a "U" opto. These are simply miniaturized versions of the larger optos, with a transmitter side and a receiver side]]
|}

The receiver opto is housed in a black plastic frame. This "IR detector" opto conducts the 12VDC supplied to it, as long as the transmitter's "light" is cast upon it. Once the transmitter light is removed, the opto no longer conducts the 12VDC. Typically, circuitry on an "opto switch board" interprets the lack of 12VDC using an LM339 comparator, and indicates that the switch is open. Remember that the "sense" of opto switches is reversed from regular "hard" switches such as leaf switches and micro-switches.

Note that the ball trough uses these opto receivers also. Orient the ball trough receivers flat side so that the leg on the flat side is furthest away from the "ear" that is silkscreened on the board.
{| border="0"
|[[file:OptoReceiver.jpg|300px|thumb|left|The solder side of a typical Williams opto receiver.]]
|[[file:OptoReceiverLED.jpg|300px|thumb|right|The component side of a typical Williams opto receiver with an aftermarket receiver LED. When replacing the opto, orient the flat side toward the "C" (equivalently, orient the "short" leg of the opto toward the "C"). OEM LEDs have an "ear" that matches the silkscreen on the board]]
|}

=====Opto Testing=====
[[file:OptoTestingWithDigitalCamera.jpg|300px|thumb|left|Testing an opto "sending" unit with a digital camera. This opto pair senses "Rudy Hits" in Funhouse. The white opto housing can be seen (upside down)]] 
The "sending side" or transmitter side of an opto pair, which should be housed in a white plastic frame, can be tested with just about any digital camera. In the picture at left, an iPhone camera was used to clearly see the purplish glow of a working opto sender.

The "receiving side" of an opto pair, which should be housed in a black plastic frame, can be tested with just about any strong incandescent flashlight. Note that an LED flashlight does not typically work too well for this test. Place the game in switch test. Block the sending opto that would normally illuminate the receiver under test. Shine your bright incandescent flashlight on the receiver opto. The switch state as shown on the display should change.
 

=====Basic Operation Opto Board=====
Note that the following description does not apply to the Twilight Zone opto board. It applies only to those boards that use LM339 Quad Single Supply Comparators. 
[[file:Opto-board-schematic-demo.gif|1000px|thumb|The operation of an single Opto Board circuit.]]

The standard Williams WPC opto board is connected to one or more columns and three or more rows of the switch matrix. The LM339 Comparator simulates the closure of a physical switch and it isolates the switch matrix from the opto phototransistor. 

The column voltages are held high by the pull up resistors in the MPU and drop to near zero when that column is strobed by the MPU. 

The LM339 works by comparing the (+) input voltage vs. the (-) input voltage. When the (+) input is a higher voltage than the (-) input, the output of the LM339 is off (floating) and the row connection is held high by pull up resistors in the MPU. When the (+) input is a lower voltage than the (-) input, then the LM339 pulls the line low (near zero V DC). 

The opto board "closes the switch" and the LM339 pulls the row voltage low only if the opto is not blocked (open) and the column is strobed. It is only under these two conditions that the (-) input is higher than the (+) input. 

If the column is strobed and the opto is blocked, the output of the LM339 is left floating and the MPU senses that the switch is open. The opto board leaves the row high if the column is not strobed no matter what the status is of the opto. 

=====7 Opto Board Testing=====
[[File:7OptoBoard.jpg|400px|thumb|right|An example WPC 7 Opto Board, as found in AFM, WH2O, and many other WPC games.]]
The 7-Opto Board (A-14977, A-15576, A-15595) pictured at right, can be tested "in-situ" with a simple jumper wire and a DMM.

'''Procedure''' 
Test the LM339 comparators

#Place the game into switch test (T.1)
#Remove the balls from the game to prevent them from crashing down on the playfield (or stuff a rag into the ball loading hole)
#Place the playfield in the vertical position
#Remove the J2 connector on the 7 opto board
#Clip one end of a jumper to J2/pin 10
#In turn, touch the other end of the jumper to pins 1 through 7 of J2
#With each connection, a opto switch activation should be enunciated on the display
#If all 7 switch activations are enunciated, this proves that all of the LM339 comparator circuits are working.

Test the 12VDC power supply circuits
#Set a DMM to DC volts (less than 20 if not using an auto-ranging DMM)
#Remove the J1 connector
#Clip the black lead of a DMM to J1/pin 10 (ground)
#With the DMM red lead, measure DC voltage at pins 1 through 8 (excluding pin 4)
#Each pin should measure about 12VDC
#If all 7 pins measure about 12VDC, this proves that each of the 12V power circuits (and the 270 ohm current limiting resistors) are working.

If a game opto pair fails to function properly, yet both of the above tests pass, then either the opto transmitter or receiver has failed or the wire/connector connection between the opto board and one/both playfield optos has failed.

==== "Jittery" Opto Switches ====
It is possible for all opto switches in the game to act erratically. This can be difficult to diagnose because the problem can manifest itself in various ways during game play. For instance, the bulldozer blade in "Roadshow" may occasionally be unable to find it's home position. Or, the auto launcher in "Twilight Zone" may seem to want to launch a ball when none is present. Since the cabinet flipper switches are sometimes optos as well, the game's flippers may also behave strangely.

The first step is to check the optos in switch edge test. If the optos appear to blink on and then off, when the actual physical state of the opto is open, suspect an issue with the unregulated 12VDC voltage.

Measure for about 12VDC at TP1 on the power/driver board. If the voltage is significantly below 12VDC (i.e. around 10VDC) then there may be a problem with the bridge rectifier at BR5 or the 15,000uf filter capacitor at C30. Examine the solder joints at C30, especially if that capacitor has been replaced in the past. A damaged through hole may effectively remove the filter cap from the circuit, AC voltage will remain in the power circuit, and the optos will be flakey.

Use your DMM to [http://www.pinwiki.com/wiki/index.php?title=General#Testing_a_Bridge_Rectifier test the bridge rectifier] and to "buzz" between the solder joints at the cap and the appropriate legs of BR5. If this connection is flakey, repair it using a [http://www.pinwiki.com/wiki/index.php?title=General#Repairing_traces_or_creating_a_.22solder_stitch.22 solder stitch] or connect jumpers from the C30 to BR5.

====Other Switch "Jitter" Reasons====

[[File:WPC-C2-Leaking.jpg|300px|thumb|left|A leaky electrolytic cap at C2 caused the "digital" 12V to drop to about 10.5VDC.]] 
The electrolytic cap C2 in the regulated 12VDC circuit leaks quite often, eroding the traces, sometimes severing the connection completely and sometimes reducing the 12VDC power output to something lower. This can wreak havoc on the switch matrix as the regulated 12VDC is used by the LM339 comparators on the MPU board to detect switch closures. Normal cleanup procedures can be used; wipe clean, sand as necessary, retin traces, and replace the cap with a 100uf/35VDC cap (an upgrade).
 

==== Sub-microswitch Issues ====

[[file:WPCMicroSwitch.jpg|300px|thumb|left|A typical micro-switch and wireform.]] 
Some WPC games have an issue with micro-switches that are heat damaged during game assembly. When soldering the wire lead(s) onto the switch, flux leaches into the switch body and, over time, causes the switches to become "sticky".

Game switches from smoky environments often become intermittent or fail. You may be able to repeatedly actuate the switch with your finger and get it to work for a game session, but when you return to the game later, the switch will have failed again.

Tightening the screws too tightly on the switch can damage the switch internals making the switch intermittent.

The switches in games that were played on location for many years simply wear out.

When micro-switches are damaged or past their useful lifetime, there is nothing to repair, adjust, or clean inside them. Simply replace them for reliable operation. You can purchase generic switch bodies and transfer the wireform carefully to the new body.
 

====Switch Wiring====

[[File:SwitchWiringSchematic.jpg|left|thumb|300px|Williams Individual Switch Connection Schematic. The green wire is the switch column. The white wire is the switch row.]] 
Williams switches are always wired the same. The white (plus tracer) colored wire (row) always attaches to the same solder lug as the NON-banded end of the diode. The green (plus tracer) colored wire (column) always attaches to a lug by itself. The banded end of the diode always attaches to a lug by itself. This creates the following circuit, shown schematically at left.
 

The picture gallery below provides an example of correct wiring for different types of switches.

<center>
<gallery widths=300px heights=300px perrow=3 caption="Connections for Various Types of Williams Switches">
File:StandUpSwitchWiring.jpg|<center>Slingshot Switch. The Green and White wires go off-frame to the other slingshot switch in the pair.</center>
File:StandUpSwitchWiring-A.jpg|<center>Standup Target</center>
File:PopBumperSwitchWiring.jpg|<center>Typical Pop Bumper Switch</center>
File:MicroSwitchWiring.jpg|<center>Older Style Micro Switch</center>
File:SubMicroSwitchWiring.jpg|<center>The Pervasive Sub-MicroSwitch</center>
File:ReedSwitchWiring.jpg|<center>Reed Switches, as found in Cactus Canyon and NBA Fastbreak. The diodes are located elsewhere.</center>
</gallery>
</center>
 

===Display problems===
Display problems are usually the result of failing dot matrix displays themselves, flakey ribbon cables or connectors, ribbon cables installed "one row off" (or even one column off), failing high voltage sections of the dot matrix controller board, and rarely logic IC problems on the dot matrix controller board.

Start by checking the easy things first...

#Reseat the narrow ribbon cable between the DMD controller board and the DMD.
#Reseat the wide ribbon cables from the MPU to the DMD controller.
#Ensure each ribbon cable is correctly mated, and not "one row off" or even "one column off".

====Display Panel Problems====
[[File:DMDDisplayFailure.jpg ‎|left|thumb|300px|This DMD Display Panel shows two partial columns out. This failure looks much like a RAM error but the missing pixels are all adjacent. The failure is internal to the DMD display itself. (the entire column that is out is part of normal display test)]] 

The display panel itself may have problems. The glass component has a limited life. The continued electrical discharge releases gases inside the display, which eventually stop the pixels from glowing, and the dots will slowly fade over time. If the voltages are too high, the panel will show sparkles, clouds or ghosting.
 

====DMD Repair Warnings====
'''''Be careful when repairing the DMD Controller Boards, you are dealing with High Voltages when the boards are running'''''.
A good safety measure is to put one hand in a back pocket (or behind your back) when testing voltages.

It's also fairly easy to lift traces on the PCB or ruin the 'through holes' when removing components. If this happens, you may have to check continuity and 'stitch' the component hole with a thin wire strand. It's a good idea to practice on some useless PCB boards first, before taking on the DMD Controller Boards. For details on a stitch see the [[General#Repairing_traces_or_creating_a_.22solder_stitch.22| "How to Stitch"]] section of the Wiki.

High Voltage Repair Kits are sometimes available from various pinball parts suppliers. '''If you do not have decent soldering and de-soldering skills, DMD HV work should be left to a professional.'''

Bally/Williams and Data East have similarities with the 128x32 display and the display itself is interchangeable between manufacturers. DMDs have a limited lifetime and will eventually outgas. Please see the [[Data_East/Sega#Score_Display_Issues | information about outgassing displays]] in the Data East section.

====Testing DMD Controller Power====

[[File:TestingDMDVoltagesAtTheDMDConnector.jpg|300px|thumb|left|Testing DMD Controller voltages at the display. The hand model is Theresa Hibler]] 
After you've checked the easy things, measure the voltages supplied by the DMD controller to the DMD display panel. To test the DMD controller voltages, first open the backbox, and rest the DMD panel face down on the glass. The simplest place to test the voltages provided by the DMD controller is at the display end of the power wire bundle as shown in the picture. SAFETY WARNING: Your left hand should be in your pocket, to avoid a potentially serious shock. We are working with high voltages, so be VERY CAREFUL. Keeping one hand in your pocket is a good practice to follow as it eliminates the easy electric current pathway across your heart. A DMD controller provides enough electric current to kill you! 

[[File:OverDrivenDMDDisplay.jpg|300px|thumb|left|A manifestation of overdriving a DMD with too much voltage.]] 
Most high voltage problems are lack of the proper voltage levels. This results in no display at all. It is possible however, for the high voltage circuitry to fail in such a way that too much voltage is supplied. Or, a game might be jumpered for a lower expected voltage but connected to higher voltage. This manifests as a "plasma" or "cloudy" look on the display, as shown on the left. Note that this looks very much like an outgassed display.

[[image:YT.png]] A YouTube video showing the manifestation of high voltage being too high can be viewed [https://youtu.be/QtSXbrHBnmw?si=3R3tGq2yiUjXLNz_ here].
 

[[File:WPCDotPowerTest.gif|300px|thumb|left|Testing AC input voltages to the DMD Controller board. Click on the image to show the animation. Image provided by Sascha Voksuil aka Pinsider Zaza.]] 
If the display image has a "plasma" affect or a "cloudy" look, it's a good idea to test the input voltage to the DMD Controller board, as depicted in the animated image at left. Nominal voltages are 80VAC and 100VAC. If measurements indicate voltages significantly higher than the nominal voltages, ensure the voltage select jumpers are correct, as discussed [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Primary_Voltage_Selection_Jumpers_at_the_Transformer here].
 

The dot matrix display needs three voltages to operate. Williams designed the DMD controller to drive the the DMD display panel just a bit below its specified voltages, presumably to extend the life of the panel. You can find the specification of a panel [http://www.vishay.com/docs/37006/apd128g.pdf here].

Place the black lead of the DMM under the ground braid in the game's head or use clip leads to secure the black lead to ground. Remember, you are working one-handed, so this becomes a necessity. Place the red lead of your DMM on each of the pins supplying power as shown in the picture. At some point in the production of DMD controllers, Williams changed the Anode and offset voltages from about -124VDC and -112VDC to about -112VDC and -100VDC. As long as there is a 12VDC difference between the Anode and 12VDC offset voltages, your DMD controller is providing correct voltage levels.

{| class="wikitable"
!Function
! J604 Pin 
! Spec 
! nominal WPC voltage 
!Notes
|-
|  Anode || <center>1</center> || <center>-110V</center> || <center>'''-112V'''</center> ||  -124V in early DMD machines
|-
|  12VDC Offset  || <center>2</center> || <center>-98V</center> || <center>'''-100V'''</center> ||  Must be 12V less than anode voltage. Will be about 20V less than anode voltage if display not connected
|-
|  Key || <center>3</center> || || ||
|-
|  Ground || <center>4</center> || || ||
|-
|  Ground || <center>5</center> || || ||
|-
|  5VDC || <center>6</center> || <center>5V</center> || <center>'''5V'''</center> ||
|-
|  12VDC || <center>7</center> || <center>12V</center> || <center>'''12V'''</center> ||
|-
|  Cathode || <center>8</center> || <center>75V</center> || <center>'''62V'''</center> ||  Williams runs this voltage low
|}

If the high voltages are off by more than a few volts, turn the game off, disconnect the power connector at the DMD controller, and test the voltages at the DMD controller male header pins. If the voltages return to nominal WPC voltages, the zener diodes on the DMD controller are probably OK but the resistors and transistors around them are suspect. As shown in the table above, if DMD controller power is not connected to the display, the nominal 12VDC offset will be about 20VDC.

Note that a failing or failed DMD display glass can drag these voltages down. Before you begin any work on the DMD controller board, perform the above test with the DMD display power disconnected. If the voltages return to nominal WPC voltages, it's possible that your display is the culprit. Test the DMD controller with a known good display to isolate the fault to either the DMD controller or the display panel.

[[File:LowHVSupply.jpg|300px|thumb|left|Measuring for 62VDC, and finding only 19.95VDC. The result of this low component of the high voltage trio can be seen in the picture. The manifestation is similar to an outgassed display. The display is showing "FREE PLAY".]] 
For the 62V and -112V circuits Williams used a relatively sophisticated regulator circuit. The problem is, the resistors and diodes dissipate quite a lot of heat. In a warm operating environment, this leads to burned components and circuit boards. The board traces are often weakened. Repair in the area is tricky.

Here's a description of the function of the parts in the -112V circuit.

Q1 is an output buffer. It just follows the voltage set at the top of zener diode D2.
Q2 and Q3 form a constant current 5mA driver for the diode.
Q2 is a current control for D2. By pulling on the base of Q2, the zener current can be reduced to compensate for the diode leaking as it
warms.
Q3 is a current sensor for D2. Note the very low 120 ohm resistor. If D2 passes more than 5mA, Q3 will start to turn on, and reduce the current through the diode by pulling on the base of Q3. So the zener diode always operates at 5mA.

The transistors can be tested in circuit, just watch out for the 120 ohm resistors across the base and emitter of Q3.

The board is subject to transistor shorts, which can also blow out the resistors. Open resistors are a common problem if Q2 and Q3 are bad.

Sometimes when you are missing a voltage, check resistors R3 and R6 (both are 47K 1/2W). Used for switching on the transistors Q2 and Q5
In the same spot are also R12 and R13, which are also 47K 1/2W. Used for discharging the capacitors C4 and C7.
A good thing is to replace all four resistors.
 

====Schematic Diagram for WPC and WPC-95 DMD Controller Board====
Schematic for DMD HV section WPC only (adapted from TZ manual, same as link below):
[http://firepowerpinball.com/2ya/tz/wpc-dmd-hv-tz.pdf WPC DMD HV]

Schematic for DMD HV section WPC95 only (adapted from AFM manual):
[http://firepowerpinball.com/2ya/tz/wpc95-dmd-hv-afm.pdf WPC95 DMD HV]

Here’s a schematic with a list of the parts needed for both WPC and WPC-95 high voltage section repairs. the two boards are similar in the high voltage regulation sections.

[[File:DotControllerHVIcon.jpg|300px|thumb|left|Click on the hyperlink at right for the .pdf of this circuit.]] 
[[media:Wpc-dmd-hv-all.pdf|DMD HV Schematics]]
 

[[File:WPC-089-HV-CheatSheet.jpg|300px|thumb|left|Click on the hyperlink at right for the .pdf HV section cheatsheet.]] 
[[media:WPC-HV-Section.pdf|DMD HV Components]]
 

Another area which will help with troubleshooting the DMD Controller Board can be found in the DE section of the PinWiki (DE copied the Williams board designs), [http://www.pinwiki.com/wiki/index.php?title=Data_East/Sega#PS_520-5047-01_-_High_Voltage_Missing_at_the_DMD_display Data East High Voltage Repair].

The following images of a fairly crispy WPC-089 DMD controller will assist you in ensuring that all traces are repaired.

<center>
<gallery widths=300px heights=200px perrow=2 caption="DMD Controller, High Voltage Section Parts removed">
File:DMDControllerFrontSideTraces.jpg|<center>Front side traces. The yellow line shows where a trace had burned off of this board.</center>
File:DMDControllerRearSideTraces.jpg|<center>Rear side traces.</center>
</gallery>
</center>
 

====Diode Test Reference for WPC DMD Controller High Voltage Transistors====
[[File:DMDControllerDiodeTestValues.jpg|300px|thumb|right|Anticipated "Diode Test" Measurements for the WPC DMD Controller Board. Click to enlarge]] 
The image at right delineates expected diode check values for a working WPC DMD Controller.

#Set your DMM to "diode check".
#Place the black or red lead as indicated on the center leg of the transistor.
#Measurements should match the indicated values within reasonable range. i.e. "Close is good enough"
#Gross discrepancies indicate that the part has failed.

Additional note regarding high voltage resistors 
Two of the 47K 1/2W resistors (R12, R13) adjacent to the 160V filter capacitors can be measured "in circuit" and will measure about 47KOhms. 

The other two resistors (R3, R6) cannot be measured "in circuit". Valid measurements of those resistors can only be made with one lead lifted. 
 

====DMD Controller High Voltage Repair Kit Parts====
When rebuilding the high voltage DMD controller sections on WPC/WPC-95, there is a list of parts that should normally be replaced because of heat damage. Note that for some components (especially the resistors), they have higher specs than the original components in order to prevent the same heat fatigue issues from reoccurring like with the original components.

'''WPC High Voltage Repair Kit Parts'''
* 1N4759A, 62V, zener diode - D3
* 1N4758A, 56V, zener diode - D4, D5
* 1N4742A, 12V, zener diode - D8, D6
* 1N4004 diode - D7
* 2N5551 (MPSD02) transistor - Q2, Q10
* 2N5401 (MPSD52) transistor - Q4, Q5
* MJE15030 transistor - Q3, Q7
* MJE15031 transistor - Q6
* 120 ohm, 1 watt, resistor - R4, R5
* 47K ohm, 1 watt, resistor - R3, R6, R12, R13
* 56 ohm, 1/4 watt, resistor - R7
* 4.7K ohm, 5 watt, resistor - R8
* 1.8K ohm, 5 watt, resistor - R9
* 120 ohm, 5 watt, resistor - R11
* 220 uF, 160V, axial capacitor - C4, C7 (often left out of repair kits)
* .001 uF, 50V, disc capacitor - C11

'''WPC-95 High Voltage Repair Kit Parts'''
* 1N4759A, 62V, zener diode - D2
* 1N4758A, 56V, zener diode - D1, D18
* 1N4742A, 12V, zener diode - D3, D5
* 1N4004 diode - D4
* 2N5551 (MPSD02) transistor - Q2, Q3
* 2N5401 (MPSD52) transistor - Q4, Q5
* MJE15030 transistor - Q1, Q7
* MJE15031 transistor - Q6
* 120 ohm, 1 watt, resistor - R30, R31
* 47K ohm, 1 watt, resistor - R25, R26, R27, R29
* 56 ohm, 1/4 watt, resistor - R24
* 4.7K ohm, 5 watt, radial resistor - R43
* 1.8K ohm 5 watt, radial resistor - R44
* 120 ohm, 5 watt, radial resistor - R28
* .001 uF, 50V, disc capacitor - C11

=====Step-by-Step Repair Video=====
[[File:DMDController.png|300px|thumb|left]] 
[[image:YT.png]] A video showing the steps necessary to rebuild the high voltage section of the DMD Controller can be found [https://youtu.be/bvTKIsqnC2A here].
 

====Specific Problems & Solutions====

===== Outgassing Displays =====
[[File:OutGassedDMDDisplay.jpg|300px|thumb|left|An "outgassed" display on a Williams FishTales during display test (all pixels should be on except the single vertical line). This display took several minutes to "warm up". The plasma seemed to "float" with various portions at the top of the display appearing dark.]] 
:DMDs will eventually fail. It is important to replace an outgassing display as they place extra strain on the power supply, and will eventually damage the power supply. One sign of an outgassing display is that areas of the display need to 'warm up' before becoming fully bright or that the display will remain completely blank for a few seconds and then appear normal.

Outgassing displays look very much like a display that is being overdriven by too much voltage. The acid test is to measure the high voltage using the technique described later in this section.

Before concluding that the display is outgassing, be sure to measure the high voltages. Excessive high voltage can cause a very similar "plasma" effect.

[[image:YT.png]] A YouTube video showing the manifestation of high voltage being too high can be viewed [https://youtu.be/QtSXbrHBnmw?si=3R3tGq2yiUjXLNz_ here]. 

=====Slow Animations=====
[[File:Pre-DCSSoundCardSolderBridge.jpg|thumb|300px|left|A solder bridge formed on a pre-DCS sound card, affecting speed of display animations.]] 
Slow animations along with sound synced to the animation is a very unusual problem. It is caused by a manufacturing defect in pre-DCS sound boards. As shown at left, an imperfect solder mask led to a solder bridge connecting pins 31 (R/W, read/write) and 34 (FIRQ) on the solder side of the sound board. By connecting the FIRQ signal and the R/W signal, the whole system slows down due to extraneous FIRQ interrupts to the MPU ASIC. The correction for this is straightforward, remove the solder bridge. 

[[File:TZSlowAnimations.jpg|thumb|300px|left|A screen shot from the YouTube video showing slow animations on a Twilight Zone.]] 
[[File:YT.png]] A YouTube video of this problem can be found [http://www.youtube.com/embed/gThgBHVuwio?autoplay=1&rel=0 here].

A PinSide thread leading to this solution can be found [http://pinside.com/pinball/forum/topic/tz-slow-dmd-animations-and-parts-suggestions here]. 

====="SuperScript or SubScript" Characters=====
One of the more interesting display failures is the appearance of characters on some display formats that appear to be shifted up/down 1/2 character or SuperScripted/SubScripted. The cause of this failure is not the display or the dot controller. This failure is caused by a poor connection between the ASIC on the MPU board and it's socket. Reseating the ASIC generally solves this problem. You can "retension" the ASIC leads using this [http://www.greatplainselectronics.com/tech_wms_asics.asp method] provided by Ed at GPE.
<center>
<gallery widths=300px heights=200px perrow=2 caption="Super/Subscripted Characters">
File:DisplaySuperScript.jpg|<center>Superscripted characters...</center>
File:SubscriptNoFear.jpg|<center>No Fear subscripted characters...</center>
File:DisplaySubScript.jpg|<center>Subscripted characters...</center>
</gallery>
</center>
 

===== "Rolling" Horizontal Line on WPC-95 Display =====
This problem resembles an old CRT with a vertical hold problem. A wide horizontal line "rolls" through the display from top to bottom.

This problem is easily rectified by replacing C28 and C42 on the Audio/Video board. The original value of these radial capacitors was 150µF/160V. If the original valued capacitors can't be located, the more common 220µF/160V cap is a good replacement.
 

===== Display is "delayed" after turn on =====
There are cases of import machines incorporating an aftermarket circuit that delays the DMD display from appearing for a fixed amount of time after the game is booted. This was done by some operators so that serial number and location information could not be seen when the machine is powered on, thereby preventing identification of a game and potential sales/operation outside a given geographic area. This circuit will not damage anything but is not standard. More information about this can be found in a [https://groups.google.com/d/topic/rec.games.pinball/Q7_FezXgJ7Y/discussion rec.games.pinball discussion.]
 

====="Snow" on Display=====
"Snow" in this case means rapidly flowing, left to right, "sprays" of dots, almost like can be seen when "spraying" the gun while moving it left to right in Attack from Mars video mode, but much faster.

The cause of this in at least one case was found to be a failed 74HC74 (dual D-Type Flip-Flop) at U4. Pin 5 is the "serial clock" signal to the DMD display. Diode testing indicated that the gate had failed. Replacement of the IC returned the board to normal service.

=====Fuse F601 or F602 blows=====
[[File:WPCDMDControllerBridgeTestingStep1.jpg|300px|thumb|left|Testing the bridge, step 1, red lead on negative.]] 
The WPC DMD controller rectifies AC voltage via two small 1 amp bridge rectifiers. If a bridge shorts, generally the associated fuse will blow. Sometimes the current draw on the other side of the bridge is so great that the fuse blows too. Whatever the reason, the bridge can be easily tested using the same general bridge testing technique.

The pin layout for these small bridges is different from the larger 35A bridges on the power/driver board.

Begin with your DMM set to diode check, and the red probe on the leg marked with a negative sign as shown in the picture at left. Placing the black lead on each of the AC legs in turn should yield a reading between .5 and .7 volts. If your measurements fall outside of this range, replace the bridge.
 
[[File:WPCDMDControllerBridgeTestingStep2.jpg|300px|thumb|left|Testing the bridge, step 2, black lead on positive.]] 
Next, move the black probe to the leg marked with a positive sign as shown in the picture at left. Placing the red lead on each of the AC legs in turn should yield a reading between .5 and .7 volts. If your measurements fall outside of this range, replace the bridge.

[[File:YT.png]] A YouTube video showing how to perform this test can be found [https://www.youtube.com/watch?v=sOlBRkxXKGQ here].
 

[[File:ArcToGroundBlowsF601.jpg|300px|thumb|left|The circled area clearly shows where this trace arced to ground.]] 
Another reason for F601 to blow is shown at left. Some revisions of the DMD Controller routed the trace from one side of BR1's AC power to F601 too close to the lower right screw that secures the board to the backbox ground. If the star washer for this screw bites through the solder mask, this creates a direct path to ground, blowing F601, as it should. This can be corrected by either leaving the screw out, using a nylon washer, or using a nylon screw. Any of these three methods will work fine.
 

===== Heat Damaged Trace Under R9 =====
[[File:WPCDotControllerRoastedTrace.jpg|300px|thumb|left|The burn spot in the center of this picture obliterated the trace that runs from R3/C4 to R11, indicated by the yellow line.]] 
Resistor R9 eats a lot of current and becomes very hot, especially as the associated circuit components age. This damages the trace and PCB beneath it, sometimes to the extent that the trace is severed. "Buzzing" the connection between C4 and R11 is a simple test to ensure continuity of this trace.
 

=====Evenly Spaced Vertical Lines=====
Evenly spaced vertical lines with 8 columns between the lines can indicate a connectivity issue along a ribbon cable. Running the display test may show a "page error" message.

<center>
<gallery widths=350px heights=100px perrow=2>
file:Dmd-vertical-lines-error-2.jpg|Example
File:Dmd-vertical-lines-error-1.jpg|Example during display test
</gallery>
</center> 

First (and with the game turned off), try reseating every the ribbon cable connector along the full length of the ribbon cables that connect to the upper left side of the DMD controller.

[[file:Wpc-reseat-ribbon-cable-connectors.png|thumb|left|350px|Reseat all the ribbon cable connectors for the wide upper ribbon cable]] 

If that doesn't resolve the issue:
* Try replacing the ribbon cable.
* Check for dirty, corroded, or broken connector pins on each of the ribbon cable headers on the DMD controller board, driver board, and MPU.
* Also check for cracked soldier joints on the header pins of each ribbon connector header on the DMD controller board, driver board, and MPU.

=====Failed RAM=====
Most failures of the DMD controller that are not attributed to the high voltage section are caused by failed 6264 static RAM at U24. Since the RAM is very susceptible to electrostatic discharge, they are often damaged by improper handling. Sometimes, they just fail. Failure of this RAM manifests in many ways, including some shown below. At the very end of "display test" the MPU performs a read/write test of the RAM. If the MPU is able to communicate properly with the DMD controller, writing to and reading from the 6264 at U6, then the message "RAM TEST OK" is shown on the display. Any other message indicates a failure of the test. Test failure may be due to the I/O buffers on either the MPU or the DMD controller, the ribbon cable, or the actual RAM.

Note: It appears that Terminator 2, MPU ROM level 8, does not cause the "RAM TEST OK" message to appear. Instead, the screen goes blank for about the time that the message would have been written, and then the test continues.

[[File:YT.png]] A YouTube video of a successful display test can be found [https://www.youtube.com/watch?v=-IK6PZL8I5o here].

=====Page Errors=====
There are 2 pages of 16 memory locations (0 to 15) stored in RAM on the DMD controller board. In the Display diagnostics it will run the page test and display any possible faults on either the low page or the high page (page 1 and 2 respectively) If you are only seeing errors on page 1, look to change out U33, most likely at least one output stuck high (pins 2,7,10,15). Page 2 errors the likely culprit is U35. Both devices are 74LS175. If you are seeing the same errors on both page tests, most likely it will be U16, a 74LS157, which is the A/B selector between the two page addresses.

Page errors will also throw up a RAM address error. The RAM is not at fault, just how it is addressed by the page selectors. It should clear after attending to the above

'''Note:''' the coin door buttons for advance/go back can be held down to quickly move through display test. 

<center>
<gallery widths=350px heights=100px perrow=2 caption="Various display issues resulting from failed 6264 RAM on the WPC-089 DMD Controller board.">
File:BadRAM-1.jpg|<center>Example 1</center>
File:BadRAM-2.jpg|<center>Example 2</center>
File:BadRAM-3.jpg|<center>Example 3</center>
File:BadRAM-4.jpg|<center>Example 4</center>
File:BadRAM-5.jpg|<center>Example 5</center>
File:Blown6264.jpg|<center>This random pattern caused by a blown 6264 RAM. It was blown by sending Flipper Coil power (nominally 70VDC) down the data lines (D0-D7).</center>
File:BadRAM-7.jpg|<center>Example 7</center></gallery>
</center>
 

=====Failures of Various Logic ICs on the DMD Controller=====
The following images represent various failures associated with specific ICs on the DMD Controller board. Of course, the specific way that an IC fails will influence what is displayed. That is, your mileage may vary. 

[[File:WPCDotControllerU1Failure.jpg|400px|thumb|left|]] 
U1 - 74HCT138 - evenly distributed non-moving "snow"
 

The display works in the game and attract-mode but in the test menu it shows nothing. U31 and/or U32 was defective. Think the opposite when the display shows nothing its worth to go into the test because possible it shows only the test.

When the display shows nothing but the data between U31 and U32 seems to be good and also there is data on BD0...BD7 to U29. Test Pin 2 of U29. If there is no clock then follow the line in the schematic to U20. There must be a clock at Pin 1. If no clock coming out from U17 Pin 9 the display shows nothing. After replace U17 the clock signal was there but corrupted from IC U4. After replace U4 too the DMD controller works.

The display shows nothing. The following lines send data to the display SERIAL_DATA SERIAL_CLOCK COLUMN_LATCH ROW-WRITE but ROW-DATA is static High or Low. U13 was defect.

 

===Sound problems===

Before going any further, check all of the basics in the [http://www.pinwiki.com/wiki/index.php?title=General#Basic_Sound_Troubleshooting Basic Sound Troubleshooting] section. 

==== Sound Board Interface Error ====

A "Sound Board Interface" error occurs when the MPU board can not communicate properly with the sound board at boot up. There could be several reasons for this problem.

#Ribbon connector not properly seated. The ribbon to the sound board(s) originates at J202 on the MPU board, goes to the FlipTronics board, then to the sound board (whether pre-DCS or DCS), then on to the DMD controller board.
#Failed ribbon cable. Due to over-flexing, the ribbon may have failed.
#Mismatched ROMs between the MPU and sound board. This isn't as big of an issue as with Data East games, but updating the game ROM to a newer version while leaving the sound ROMs at an older, even prototype version, could cause this problem.
#Solder bridges, or corrosion under the ribbon connector.
#Failed I/O buffer ICs on either the sound board or on the MPU board

On '''DCS sound boards''', U18 buffers data '''from''' the MPU. U19 buffers data '''to''' the MPU. Testing these ICs using the [http://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit this method] should yield similar results to the values listed below. Note that this test method can't identify either a good or a bad integrated circuit with 100% certainty but using this test is preferable to removing chips unnecessarily. These readings were taken using a Fluke 179 DMM. Different meters, different manufacturers chips, and even individual variation in manufacture will probably cause your readings to be slightly different, yet consistently different. i.e. If the table shows .657 and your meter yields .630, then every pin listed at .657 should read close to .630 with your meter.

Probe pin 10 with the DMM red lead. Probe each of the other pins with the black lead.

{| class="wikitable"
! Pin 
! Diode Test Value U18 
! Diode Test Value U19 

|-
| <center> 1 </center> || <center>.583</center> || <center>.580</center>
|-
| <center> 2 </center> || <center>.519</center> || <center>.659</center>
|-
| <center> 3 </center> || <center>.657</center> || <center>.510</center>
|-
| <center> 4 </center> || <center>.657</center> || <center>.516</center>
|-
| <center> 5 </center> || <center>.511</center> || <center>.656</center>
|-
| <center> 6 </center> || <center>.511</center> || <center>.656</center>
|-
| <center> 7 </center> || <center>.657</center> || <center>.510</center>
|-
| <center> 8 </center> || <center>.657</center> || <center>.510</center>
|-
| <center> 9 </center> || <center>.511</center> || <center>.656</center>
|-
| <center> 10 </center> || <center>Red Lead</center> || <center>Red Lead</center>
|-
| <center> 11 </center> || <center>.580</center> || <center>.580</center>
|-
| <center> 12 </center> || <center>.510</center> || <center>.657</center>
|-
| <center> 13 </center> || <center>.657</center> || <center>.518</center>
|-
| <center> 14 </center> || <center>.657</center> || <center>.516</center>
|-
| <center> 15 </center> || <center>.519</center> || <center>.656</center>
|-
| <center> 16 </center> || <center>.517</center> || <center>.578</center>
|-
| <center> 17 </center> || <center>.657</center> || <center>.517</center>
|-
| <center> 18 </center> || <center>.578</center> || <center>.509</center>
|-
| <center> 19 </center> || <center>.517</center> || <center>.657</center>
|-
| <center> 20 </center> || <center>.398</center> || <center>.398</center>
|}

[[File:WPCSoundBoardInterfaceErrorCorrosion.jpg|300px|thumb|left|Corrosion in the area of a critical signal caused a "Sound Board Interface Error".]] 
The root cause of a "Sound Board Interface Error" on a Star Trek:The Next Generation game is shown at left. The corrosion on the trace leading to pin 28, created a conductive bridge to pin 29, which is a critical signal to the sound board (WDEN).
 

[[File:WPCpreDCSSoundBoardSolderBridgeatU16.jpg|300px|thumb|left|A solder bridge at the circled location (U16), connecting pin 7 of the IC (ground) to the via and hence connecting pin 2 to ground, manifested as a "Sound Board Interface Error".]] 
Another physical PCB problem pictured at left (but repaired), caused a "Sound Board Interface Error". The sounds on this board operated fine since the error was in the hardware that talks back to the MPU.

A similar problem can be the cut component lead just left above the yellow circle. If it is bend towards the printed trace and making contact, it can also manifest itself as the "Sound Board Interface Error".
 

==== Shorting the Speaker Leads or a Shorted Speaker ====

[[File:BlownTDA2030.jpg‎|300px|thumb|left|Clearly, a major malfunction.]] 
A blown sound amp will cause a loud buzz when the game is powered on. Generally, amps blow due to reduced impedance (aka resistance, ohms) in the speaker(s). If a speaker shorts, the associated amp(s) will blow. Or, if the drive connection (not ground) to a speaker breaks free of the speaker connection lug and touches ground with the power on, the associated amp(s) will blow. Note that the speaker metal housing is connected to ground.

The image at left shows two amps from the same WPC-95 AV board that were blown when the non-ground speaker wire broke free and touched the speaker housing. It is good practice to solder the speaker wires onto the speaker connection lugs to prevent this from every happening.

Diode testing is an effective method of determining that an amp is blown. Place the red lead of your DMM on the center leg of the amp and test each of the remaining four legs. Compare results to a known good amp of the same type. Generally, readings between .5 and .8 should be observed. 

==== Lowering the Minimum Volume ====
By default the game volume can be set no lower than '8' to prevent an operator from setting the volume too low. This can be overridden by entering the adjustments menu and setting Adjustment 1.28 (Minimum Volume Override) to yes. You can now set the volume as low as you like.

====High Frequency Sound Only====
This applies to pre-DCS and DCS sound boards. This has not been proven to apply to WPC-95 AV boards, yet.

There is a situation where only the tweeter / high frequency sound can only be heard. This will result in the game sounding much quieter than usual. Most speaker systems are parallel circuits. However, the woofer on a pre-DCS sound system is in series with the midrange speaker. The high frequency speaker is in a parallel circuit to the mid and low range speakers. If there is no sound from the woofer in the bottom of the cabinet, there will be no midrange from the speaker panel.

First, make certain that the speaker output wiring from the sound board is connected correctly. Also, there is a bullet connection located inline which must be connected. This bullet connections ties the low and midrange speakers in series. Finally, check the connections at the woofer in the bottom of the cabinet to make certain the female spade connectors are secured to the speaker terminals. If all connections are secure, there is a chance that the woofer speaker is blown.

====Pre-DCS Sound Board Issues====

The blue Philips 47µF 35v axial electrolytic capacitors on these sound boards are prone to failure, often testing with no capacitance or extremely high equivalent series resistance.

===== Schematic for preDCS Sound Board =====
[[Image:LM1875.jpg ‎|300px|thumb|left|]] 
Schematics for the preDCS sound board can be found [https://www.pinwiki.com/wiki/images/1/1d/PreDCS.pdf here].
 

===== Power on Sound Tones (Bongs) =====

After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs. Instances have occurred where the U9 RAM chip had failed, but only 1 "bong" was sounded. In this case, other than the bong, the board produced no sound at all. This calls into question the robustness of the power on RAM test.

Pre-DCS Sound Board Games.
*1 - No issues...enjoy a game.
*2 - U9 RAM failure.
*3 - U18 ROM failure.
*4 - U15 ROM failure.
*5 - U14 ROM failure.

=====No Sound at all=====
[[File:SoundBoardU9RAMError.jpg |thumb|left|500px| Infrequently seen preDCS sound board RAM error message. Image courtesy of PinSider "DownSouthPinball"]]
The highest probability reason for the complete lack of sound is connections to the speakers. The IDC connectors at J504 and J505 carry the sound to all speakers in the game. Since the speakers are connected in series on a pre-DCS game, any break in the speaker signal loop will cause loss of all sound. First check the small gauge wires at connectors J504 and J505. Since they are IDC connectors, they are prone to breaking free from the connector. Next ensure that all speaker connections are solid.

It is possible for a speaker to fail, commonly called "blown". You can test a speaker by applying anything from an AA battery to a 9V battery to the speaker terminals. You should see the speaker cone react when the battery is touched to the terminals.

Another possible cause of no sound at all is a failed 6264 RAM chip at U9. It is possible for the RAM to be failed, the board passes the power on self test, a single "bong" is heard, no convenient message as shown at left appears, and yet the board produces no other sound at all.
 

In one case, while the amplifier was clearly working as it would "buzz" at power on, one of the four diodes configured to rectify AC power into DC power had shorted. This cascaded into a failure of the 7912 negative 12V regulator which was delivering about -5VDC. Further analysis showed that both TL084 operational amplifiers and the TL082 operational amplifier had failed. After replacing the TL084 operational amplifiers, most sound returned but sound from the "DAC lane" was still missing, which indicated the TL082 operational amplifier had failed. Replacement of that operational amplifier returned the sound board to proper operation.

[[image:YT.png]] A YouTube video demonstrating this failure and the repair can be found [https://youtu.be/-pQ_Zlsmq38 here]

In the video, which uses Addams Family ROMs, sound 7 within sound test, "Thing Multiball" is clearly missing the classic two finger snaps that are contributed to the sound mix by the AD7524 DAC.

Another known DAC channel contribution is in The Getaway: High Speed 2, sound 3 within sound test, "Super Jackpot", the drumming that can be heard at the start of the clip. Interestingly, if that sound test is set to repeat, the drumming sound is omitted entirely. This isn't a DAC or other sound board failure. The omission is caused by a software coding error where the first part of the "compound sound" is never called for.
 

=====Static Replaces Power On Bong But Ceases Upon Diagnostics Entry=====
A failed 6264 RAM chip can cause numerous "oddball" behaviors. In one such case, the power on "bong" sound was replaced with static. Upon entering diagnostics, the static was silenced and the board operated normally and would continue normal operation until powered down and back up again. Replacing the RAM solved this issue. 
[[image:YT.png]] A YouTube video demonstrating this failure and the repair can be found [https://www.youtube.com/watch?v=B78G1Zkj_aY here]
 

=====Unbalanced Sound=====
[[Image:WMSpreDCSR23R24.jpg ‎|300px|thumb|left|56Kohm Resistors at R23 and R24 for games Hot Shots through Addams Family Gold (last preDCS game).]]
[[Image:WMSpreDCSSoundR23R24.jpg ‎|300px|thumb|right|150Kohm Resistors at R23 and R24 for games Funhouse through Party Zone.]] 
Pre-DCS sound boards are not 100% interchangeable across games without modification. Games from Funhouse to Party Zone (including Funhouse, Harley Davidson, Bride of Pinbot, Slugfest, Gilligan's Island, Terminator 2, Hurricane, and Party Zone) use different resistor values at R23/R24 than the remaining games that used the pre-DCS sound board (games from Hot Shots basketball through The Addams Family Gold). If you find the sound "unbalanced" between background sounds and voices, for instance, check the following resistor values.
 
R23/R24 values for... 
::Funhouse through Party Zone - 150Kohms (color bands brown, green, yellow, gold) 
::Hot Shots through TAFG - 56Kohms (color bands green, blue, orange, gold) 

Note that the resistor value indicated in the schematics for pre-DCS sound boards at R22 and R25 are wrong. The schematics indicate 150K ohms. The correct value is 120K ohms.
 

=====No Sound or Low Volume Sound from Right Speaker=====
[[Image:WPCSpeakerAndCap.jpg|300px|thumb|left|The 10uf non-polarized capacitor on the "Tweeter" (right) speaker of a pre-DCS game (Twilight Zone).]] 
As Joe "Tony" Dziedzic discusses [http://www.dziedzic.us/wpc_speaker_sound_info.html here], "the back box speakers are wired in parallel, with a 10uf non-polarized capacitor in series with the right speaker (the tweeter). The capacitor is used to block lower frequency sounds from being reproduced by the speaker. Technically, the capacitor forms a first-order high-pass filter with a crossover frequency of 4000 Hertz. This configuration presents an effective impedance of around 4 ohms."

If the 10uf capacitor fails "open", then the signal to the speaker is open and the speaker will remain silent.

The repair is simple...replace the capacitor.
 

=====Distorted or slightly "off" sounds=====
[[Image:PreDCSSoundBoardC38NotStuffed.jpg|300px|thumb|left|C38 is not stuffed on some pre-DCS sound boards.]] 
The pre-DCS sound board uses 47µF capacitors as filters in the sound circuit; C15, C36, and C38. If one or more of these caps fail, certain sounds may not be as loud or as clear as intended. The game will just sound "off" with perhaps slightly unbalanced sounds. An amazingly high percentage of these caps fail. It is recommended that if your sounds are a bit "off" that you replace all of these caps.

'''Note:''' as shown at left, C38 is sometimes not stuffed at the factory. It appears that audio channel 1 and channel 2 (in C38s path) from the Yamaha YM3012 are redundant, making this cap unnecessary.
 

[[Image:preDCSSoundBoardCapComparison.jpg|300px|thumb|left|C49, implemented in two different ways on the pre-DCS sound board.]] 
Also, some pre-DCS sound boards looked to have been "hacked" to add a ceramic capacitor just below the clock crystal X1. This is not in fact a hack. It appears to "fix" the omission of C49 on some versions of the PCB. C49 is located at the edge of the board, just above the crystal.
 

=====Static or Scratchy and Low Volume Sound=====
[[Image:WMSpreDCSSoundC21.jpg|300px|thumb|left|C21, a 10uf tantalum capacitor, sometimes fails causing static or scratchy sound.]] 
The entire audio stream passes through a 10uf tantalum capacitor at C21 just before the MC3340 audio attenuator. While extremely rare, this capacitor can partially fail and cause static or scratchy audio in ALL (CVSD, FM Synthesizers, and the DAC) channels. The audio volume may vary from normal to very low or no volume.
 

=====Popping, Scratchy Sound, Very Hot LM1875 Heat Sink, or Shorted Speakers=====
[[File:PreDCSSoundCaps.png|300px|thumb|left|Ceramic, electrolytic, and Tantalum caps to suspect with this behavior. Image courtesy of Chris Hibler.]] 
Sometimes, the tantalum/ceramic caps in the amp circuit fail too. This can result in too much AC "ripple" feeding the amp as well as DC output to the speakers, which they do not like. The following components are all suspect...

*C20 (10µF, 20V tantalum)
*C46 and C47 (both 1µF, 35V tantalum)
*C22 (22µF, 35v electrolytic)
*C23 (.22µF, 10V, ceramic)

Normally, the positive side of the tantalum cap at C26 will measure about 50mv of AC referenced to game ground. Anything more indicates a problem with these tantalum caps. You will also be able to measure DC voltage across the speaker outputs. There should normally be no DC voltage across the speaker outputs.

The LM1875 may also run very hot. Normally, you can grasp the heat sink without burning your hand. It will be hot, but not so hot that you can not squeeze it or grasp it very long. '''Note:''' this assumes that the volume is set to about 8. Setting the volume to 18 will require the heat sink to dissipate more heat. The heat sink will be too hot to grasp (for very long). If at "normal" volume levels and the heat sink is so hot that you can not grip it, failing tantalum caps should be suspected. If after replacing the tantalum caps the popping and scratchiness persist, the LM1875 amp may have been damaged.
 

=====Volume Not Adjustable and/or Stuck at Low Volume=====
This problem manifests as a very low volume from the speakers, equivalent to the lowest sound level setting. The volume setting may be adjusted from the coin door, and the DMD volume "thermometer" will move normally, but the speaker volume will not change. While the cause of this issue could be a failed digital POT as discussed [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Volume_Suddenly_at_Maximum here], a failed MC3340 electronic attenuator may also be the cause. You may be able to identify the MC3340 as the problem by comparing "diode test" results with a known good MC3340.

In one such case, pins 7 and 8 of the device where shorted together, causing the symptoms described. The failed MC3340 may also have caused the amp to become very hot, but this has not been conclusively proven.

Take care to ensure the MC3340 is actually at fault as this obsolete part is pricey and hard to find.

=====Volume at zero but still audible=====
If you set the volume to zero via the coin door buttons and you can still clearly hear it, there is a good chance that the axial capcitor C18 (47 µF, 10 V) is bad. If this capacitor fails, the output voltage of the digital pot U5 (X9503) might not go high enough to silence the sound completely. When the volume is set to zero, a voltage of approx. 3.5 V should be measured at U5 pin 7 or jumper W9 or U2 pin 2. Lower voltage will result in clearly audible sound even when set to zero.

=====Wrong sounds being played=====
[[File:FunHouseSoundTest.jpg|300px|thumb|right|An obnoxious dummy enquiring about what just happened.]]
Generally, this problem boils down to a communication problem between the MPU and the sound board. Possible failure points are:

*Ribbon cables
*Male header pins on both MPU and sound board
*74LS374 data buffer ICs on the sound board used to communicate between the MPU and the sound board.
*Rarely, the data output buffer ICs on the MPU board used to communicate with the FlipTronics, Sound, and DMD Controller boards.
*Rarely, a failed 6264 RAM can cause this. The RAM is "tested" by the MPU. Sometimes the test will pass, no message is displayed, and yet, the part fails during game play. Odd...I know.

[[image:YT.png]] A YouTube video documenting the behavior of a failed preDCS RAM chip at U9 can be viewed [https://youtu.be/B3pWA7eg4Kg here].
 

=====Volume Suddenly at Maximum=====

If the volume suddenly jumps to full volume and control of the volume via the coin door buttons does not work, check C18, a 47µF 35v axial electrolytic capacitor. The blue Philips capacitors on these sound boards are prone to failure and can cause this issue if bad. If that does not solve the problem there is a good chance that the digital POT (volume control) on the sound board has failed. The part is located at U5 and is an X9503. The X9503 is obsolete but it's successor the X9C503 works fine here.

=====Blown 1uF or 10uF Tantalum Capacitor=====
[[Image:WPCpreDCSBlownTantalumCap.jpg|300px|thumb|left|C46 blew up and burned quite spectacularly on this pre-DCS sound board.]]
[[Image:Wpc_pre-dcs_cap-failure-c28.jpg|300px|thumb|right|C28 failed on this pre-DCS sound board.]] 
The pre-DCS sound board uses 1uf tantalum caps in the amp circuit. Sometimes, for no good reason than simply being old, one of these caps will explode and burst into flames at game power on. C46 on the board shown at left did just that. In the great majority of instances, simply replacing the cap returns the board to service. This "burning into flames" can also happen to the +12V and -12V section with C26 and C28.

[[Image:BlownTantalum.jpg|300px|thumb|left|Closeup of blown 1uf cap on a pre-DCS sound board. The actual size of the cap is less than one inch in length]]
When the 1uF tantalum at C27 or C29 shorts internally, it will cause the +12V or -12V to disappear. The LM7812 (U4) or LM7912 (U3) will run very hot. The tantalum draws all the current. The LM7812 and LM7912 have a limit of 1 Amp. The voltage will drop to zero when this happens, leaving the amplifier without power.

Other tantalum caps have been documented to explosively fail, including C28 and C47.

A tantalum capacitor can be tested by desoldering one leg and using a DMM (in diode check) to check for a short. Simply replacing the tantalum will solve the problem.

A contributing factor to these explosive failures was that the voltage rating on the capacitors that were used was too close to the operating voltage running through them (undersized components were typically used as a cost saving measure). As a general rule of thumb, the operating voltage should be 50% of the voltage rating of the tantalum capacitors. So, for a 12V circuit, at least a 25V capacitor should be used; a 50V minimum rating would be better.

All the tantalum capacitors used on the pre-DCS sound board are listed below:
* C20,C21: 10uF axial tantalum capacitor (original rating was 10V; use at least 35v instead).
* C26,C27,C28,C29,C37,C46,C47,C48: 1uF axial tantalum capacitor (original rating was 35V; use at least 50v instead).

Note that the tapered end is the positive side and also has a "+" symbol near it (however, with a burnt part, this might be impossible to see). Since the board was not silkscreened with any indications of component polarity, make note of the direction on the original part before removing it. 

[[Image:Wpc_pre-dcs_tantalum-cap-polarity.jpg|500px|thumb|center|Diagram showing the tantalum capacitor locations and polarity]] 

After replacing one blown tantalum capacitor, it is possible that a second power up might blow a different one. Therefore, it might be a good idea to preemptively replace all the tantalum capacitors, especially if one has already experienced an explosive failure.
 

[[File:Failed1ufTantalumCap.jpg|300px|thumb|left|Another failed 1uf tantalum capacitor.]]
[[File:ReplacementCapForTantalum.jpg |300px|thumb|right|The replacement 1uf electrolytic capacitor installed, with the lead insulated to prevent the unlikely short to the heat sink.]] 
The tantalum caps on this board can be replaced with the same rated (1uf) electrolytic caps. The two caps adjacent to the large heat sink need to be positioned to allow space for the large 4700uf caps also adjacent to the large heat sink.
 

=====Sound Is Very Faint Even at Maximum Volume (CVSD Failure)=====
[[Image:55536-CVSD.jpg|300px|thumb|right|Two hard to find 55536 CVSD ICs.]] 
While most techs would suspect either a TL082 or a TL084 amplifier (on a pre-DCS sound board) or a 1458 amplifier (on a System 11 MPU) as the cause of this issue, the 55516/55532/55536/55564 CVSD (Continuously Variable Slope Delta-Modulator) can also cause this issue.

Isolation to the CVSD is pretty simple.

*Place the game into sound test.
*Use an oscilloscope to probe pins 9 and 12. A scope must be used since the signals are too subtle for a logic probe to detect.
*Pin 9 is a clock signal.
*Pin 12 is a data signal.

When the game is making sounds that use the CVSD (generally voice calls), both pin 9 and pin 12 should show "off nominal" signals. If the CVSD is working correctly, the output at pin 3 should be showing signal also. If pin 3 is not showing signal, then the CVSD has failed.
 

[[Image:CVSDReplacementFront.jpg|300px|thumb|left|A "daughter card" used to replace the 55536 CVSD (front).]]
[[Image:CVSDReplacementBack.jpg|300px|thumb|right|A "daughter card" used to replace the 55536 CVSD (rear).]]
During the run of the pre-DCS sound board, it is suspected that the 55536 CVSD part (and it's close cousins) was becoming hard/expensive to acquire. Williams created a "daughter card" to use in lieu of the CVSD. The daughter card used an MC3417 CVSD along with additional "tuning" resistors and capacitors. The sound quality result is indistinguishable from a 55536. Williams used a closed frame machine pin socket to accept the daughter card. The "chip notch" should be oriented just as you would the CVSD. That is, more of the card will be south of the chip socket than north of it.

While it might seem like a good idea to duplicate the design of this Williams card (part number 5768-14714-00) to replace the even harder to find 55536, the main part used, the MC3417, is equally hard to find today.

[[File:YT.png]] Jeri Ellsworth reverse engineered the 55564 (55536 equivalent) and posted [https://www.youtube.com/watch?v=2FRGwuxFDE4 this video] in October, 2011. She makes it seem "intuitively obvious to even the most casual observer"...
 

=====Sound Lane Reference=====
[[File:SoundScopeTrace.jpg ‎‎|300px|thumb|right|"White Noise" scope trace]]
That is, which sounds use which of the 4 sound "lanes" on the pre-DCS sound board?

The pre-DCS sound board produces sounds via one or more sound lane which are:
*YM2151/YM3012 FM Synthesis (2 lanes)
*AD7524 DAC
*55536 CVSD (continuously variable slope delta)

Using Addams Family game and sound ROM (U18), in test mode, 36 sounds are played.

Sounds 1-16 use both the DAC and the Yamaha synthesizers.
Sounds 17-36 use the CVSD.

[[image:YT.png]] A video demonstrating the use of an oscilloscope for detecting a properly working sound lane can be found [https://youtu.be/vpBHrccwPbc here].
 

====DCS Sound Board Issues====

The DCS sound board was used in 18 games including:

*Indiana Jones: the Pinball Adventure
*Judge Dredd
*Star Trek: The Next Generation
*Demolition Man
*Popeye Saves the Earth
*World Cup Soccer
*The Pinball Circus
*The Flintstones
*Corvette
*Red & Ted's Road Show
*The Shadow
*Dirty Harry
*Theatre of Magic
*No Fear: Dangerous Sports
*Indianapolis 500
*Johnny Mnemonic
*WHO Dunnit
*Jack*Bot

===== Power on Sound Tones (Bongs) =====

After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs.

DCS Sound Board Games.
*1 - No issues...enjoy a game.
*2 - U2 ROM failure.
*3 - U3 ROM failure.
*4 - U4 ROM failure.
*5 - U5 ROM failure.
*6 - U6 ROM failure.
*7 - U7 ROM failure.
*8 - U8 ROM failure.
*9 - U9 ROM failure.
*10 - U10-U12 RAM error. Not always identified from the main CPU board program. DCS sound board RAM failures are indicated by a message on the display, "U10-U12 RAM error".

=====Very Loud Humming at Power On=====
The DCS sound board uses two 10,000µF caps at location C20 and C21 to smooth rectified AC power. The negative side of C21 and the positive side of C20 are connected to analog ground at header J4, pins 6 and 7. This connection is fragile. If the game hums really loudly, immediately at power on, test for continuity between these points as shown in the pictures below. Often this loud hum is diagnosed as a failing cap when the real problem is simply a fractured trace. If the caps have been replaced previously, there is a good chance that the PCB through holes have been damaged.

<center>
<gallery widths=300px heights=300px perrow=3 caption="DCS Sound Board Filter Capacitor Connections. Continuity is shown as a zero ohm connection.">
File:DCSCapThroughHoleBungled.jpg|<center>The remains of through holes heinously ripped from a DCS sound board PCB. These "brown donuts" are still attached to the 10,000uf filter capacitor.</center>
File:DCSCapConnection1.jpg|<center>The first of two tests ensuring continuity between the filter capacitors and analog ground.</center>
File:DCSCapConnection2.jpg|<center>The second of two tests ensuring continuity between the filter capacitors and analog ground.</center>
</gallery>
</center>
 

=====U10-12 RAM ERROR (10 Bongs)=====
[[File:WPC95U10U12Message.jpg|300px|thumb|left|A DCS game boot time RAM error message, accompanied by 10 very annoying bongs.]]
Replacement RAM ICs for the DCS sound board are becoming harder to find. The board uses three, 2Kb skinny dip 6116 cache rams with an access time of 35nS or better. These are obsolete and long gone. The good news is that the board has jumpers for 6264 type 8Kb cache rams. Jumper W4 is installed for 2Kb rams. Jumper W4 should be removed and jumper W5 installed to use 8Kb rams. All RAM ICs need to be replaced at the same time for this configuration to work.

A relatively inexpensive, and still in production replacement, is the IDT 7164S20TPG.

RAM testers are not able to detect chips that do not meet the speed requirement. While slower RAM may pass chip test, it may fail on the board and cause the "10 bongs" error indication.

[[image:YT.png]] A YouTube video showing a DCS sound board and the "10 bongs" error can be found [https://youtu.be/jX0yLXSeEto here]
 

===== Muffled Sound and Speech/No Sound =====
[[File:DCSSoundBoardCaps.jpg|300px|thumb|left|C32 and C41, both electrolytic caps, are in series in the sound amplification circuit of the DCS sound board.]] 
Muffled audio can be caused by failure of the two 1uf/63V electrolytic capacitors that are in the audio circuit for each amplifier. Simply replacing them may clean up the audio. A typical 1uf/50V axial electrolytic capacitor will work fine.
 
It is also possible for one or both of these capacitors to fail completely open. In that case, no sound at all will come out of that capacitor's channel since they are in series with amplifier (C32 for the cabinet speaker and C41 for the backbox speakers.) Replacing the appropriate capacitor can restore sound to the silenced channel.
 

===== Volume Jumps to Max on Indiana Jones=====

The DCS sound board software has a bug in early versions that cause this issue. 
Updating ROM S2 on the DCS sound board to the latest ROM revision will correct this.

===== Scratchy Audio or mumbled speech =====

[[File:DCSSoundBoardCeramicCaps.jpg|300px|thumb|left|C37 and C45, both ceramic caps, sometimes cause scratchy audio.]] 
During production of WPC-95 games, Williams removed two small ceramic caps (C47 and C51) from the A/V board to clean up the sound. This update should also be applied to the DCS sound board. On the DCS board C37 and C45 are the equivalent caps to be removed. Simply clip the caps from the board. You do not need to desolder them. This cleans up the sound and speech on some games like Demo Man quite well.
 

===== Notes regarding the TL084 part =====
The following was authored by Ed Krzycki, in a PinSide post [https://pinside.com/pinball/forum/topic/dcs-tl084cn-vs-tl084acn#post-7091884 here]. 
The suffix on these parts indicates how far off the output 'offset' can be. The offset is an added bias to the output voltage that is typically undesired in an audio device.

The offset is measured in millivolts. Higher the value, the more offset and the output is less 'true' to original input.

*TL084CN = worst case offset (standard part) = 20mV
*TL084ACN = 7.5mV
*TL084BCN = 5mV
*TL084IN = 9mV but has a much wider temperature 'industrial' temperature range.

The TL084BCN is better than the TL084ACN and the TL084ACN is better than the TL084CN. 
The TL084IN is the same as the TL084ACN when used at normal room temperature. But the TL084IN version can withstand higher temps.

Any introduced DC voltage offset is typically removed if there is a capacitor in series with the output (common) but can still add a bit of distortion. Keep in mind that pinball sound boards are not exactly high end audio equipment so any of these TL084 parts will work with no noticeable difference. There are other components in the design that are far greater at introducing noise into the sound.
 

===== DCS Audio Format Technical Reference =====
A very informative, very detailed look at the DCS sound board audio formats etc., authored by Michael Roberts, can be found [https://www.pinwiki.com/wiki/images/a/aa/DCS_Audio_Format_Technical_Reference.pdf here].

====WPC-95 A/V Board Sound Issues====
[[File:WPCAVBoardASIC.jpg|300px|thumb|right|The location of the 120 pin Quad Flat Pack ASIC with ASIC neatly removed]]
The WPC-95 A/V Board was introduced, along with the WPC-95 system, with Congo and was used through the end of the WPC game system run. WPC-95 games using the A/B Board are listed below. The sound ROM part number is shown in parenthesis.

*Congo (5343-50050)
*Attack from Mars (5343-50041)
*Safe Cracker (5343-90003)
*Ticket Tac Toe (not a pinball)
*Tales of the Arabian Nights (5343-50047)
*Scared Stiff (5341-15191)
*Junk Yard (5341-15403)
*NBA Fastbreak (5341-15418)
*Medieval Madness (5341-15451)
*Cirqus Voltaire (5341-15584)
*No Good Gofers (5341-15591)
*The Champion Pub (5341-15703)
*Monster Bash (5341-15931)
*Cactus Canyon (5341-15191)

Always check the speaker connections to the A/V board (J504 and J505) and the wiring at the speakers before assuming there is a problem with the board. The speakers themselves can go bad; you can do a quick "click test" with a D-cell battery and a set of jumper leads to rule out dead speakers. Disconnect the speaker connections at the A/V board and connect your battery jumper leads to the pairs of wires in the J504 and J505 connectors; you should hear a click from the speaker if it is good. If you don't hear the click try the connection at the speaker itself to rule out wiring issues.

The analog output of the A/V board feeds into a TLO84 op-amp (U1) that is configured as a pair of low-pass and high-pass filters; these are used to separate the low-frequency sounds (destined for the cabinet speaker) and the high-frequency sounds (destined for the back box speakers). These two channels - signified on the schematic as AUDIO_R (cabinet) and AUDIO_L (back box) feed into a pair of TDA2030AV amplifiers; U5 drives the back box speakers and U6 drives the cabinet speaker.

The outputs of U1B and U1C (pins 7 & 8) can be briefly connected with a jumper lead to help narrow down issues when one of the two channels is not working or has weak/distorted output. When the two pins are jumpered you should be able to hear approximately the same level of sound from the cabinet and back box speakers. (Use the T.7 diagnostic test to play sound clips for the game during your testing.)

===== On Board Voltage Regulation =====
The WPC-95 A/V Board "digital" side is powered by the same 5VDC that is regulated by the power/driver board. The "analog" side of the A/V board, specifically the two TL084s and the AD1851 D-to-A converter, all use +5VDC and -5VDC that is regulated by the 78L05 and 79L05 respectively. Four rectifying diodes provide about +/- 17VDC to these regulators. If the sound is low or scratchy, check these two voltages first. Both +5VDC and -5VDC can be easily measured at pins 4 and 11 of either TL084.

===== Power on Sound Tones (Bongs) =====

After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs. Note that if more than one sound ROM exhibits a checksum error, only the first failed ROM will be indicated. Once that failed ROM is replaced, the next failed ROM will be indicated upon subsequent boots.

[[File:SoundROMChecksumError.jpg|300px|thumb|Right|WPC-95 boot time Sound Board ROM error message, accompanied by three bongs.]]

Audio/Video Board Games (WPC-95).
*1 - No issues...enjoy a game.
*2 - S2 ROM failure. Note: Two bongs also occur if jumper W3 is IN on the MPU board, and the installed RAM size is 6264. If an NVRAM was just installed, check this jumper. See the section on [[Williams_WPC#Jumpers.2C_RAM_and_ROM_size | jumpers]].
*3 - S3 ROM failure.
*4 - S4 ROM failure.
*5 - S5 ROM failure.
*6 - S6 ROM failure.
*7 - S7 ROM failure.
*10 - U9, U10, or U11 RAM failure (see below)

[[File:WPC95U9-U11Error.jpg|300px|thumb|left|WPC-95 boot time RAM error message, accompanied by 10 very annoying bongs.]]
[[File:WPC95U10U12Message.jpg|300px|thumb|right|WPC-95 boot time RAM error message, accompanied by 10 very annoying bongs.]] 
A/V sound board RAM failures are indicated by a message on the display, either "U9-U11 RAM error" or "U10-U12 RAM error". This is apparently game software dependent. A/V RAM are, in fact, U9-U11. Apparently, this message wasn't updated in some of the software with the introduction of the A/V board.

[[image:YT.png]] A Youtube video showing "10 Bongs" can be found [https://youtu.be/UFSEkHRaVvs?si=p66fWpdnTozts93o here.]
 

[[File:AligningSockets.jpg ‎|300px|thumb|left|A neat trick to ensure two sockets are aligned]] 
Should it become necessary to replace one of the skinny DIP RAM chips, in lieu of a 28 pin skinny DIP socket, two 14 pin sockets may be used. Align the sockets using the trick shown here.

Sometimes it is obvious to see that the text on one of the ram ICs is darker than the other chips. This might be a clear sign of an overloaded chip. When you replace these ICs make sure you replace them as a triplet and with (preferably) identical ICs. They should all be rated the same access time since the SRAM is treated as a vector and not individual bytes. Think RAID. In place of the 61C64 sram ICs you can also use th 61C256 chips. Those ICs should be 35ns access time at a minimum.
 

===== Loss of One Channel =====

[[File:WPC95AVBoardSoundIssue.jpg|300px|thumb|left|C38 and C39, which can cause loss of a single channel]] 

If one channel is out or weak/distorted try the jumper at U1 pins 7 & 8 noted above. If no change is detected in the sound output it is likely the associated TDA2030AV amplifier (U5 or U6) has failed. Before replacing the amplifier jumper a 1 MFD 63 volt capacitor across C38 and C39 in turn (observe polarity!) to rule out a defective coupling capacitor. If jumpering pins 7 & 8 of U1 significantly improves the sound levels it is likely that U1 itself has failed.
 

===== Scratchy Audio =====

[[File:AVBoardCapsRemoved.jpg|300px|thumb|left|A later production Williams WPC-95 AV Board, with C47 and C51 intentionally unstuffed at the factory]] 
Williams removed two small ceramic caps (C47, C51, pictured at left) later in the production run of AV boards. If your game's audio is just a bit scratchy, and these caps have not been removed, you may be able to improve audio quality by removing them. Simply clip both sides of the cap. There is no real need to desolder them.

 

===== Really Loud buzzing sound for a second or two =====

If your game sometimes produces a really loud buzzing sound at random, check the version of your S2 sound rom. This problem was fixed with the latest S2 sound ROM for Attack from Mars, Congo, Safe Cracker and Tales of the Arabian Nights. Scared Stiff might also be affected but no version history for sound 1.1 exists for this game. Later games are not affected.
 

===Flipper Problems===

In most instances, an inexperienced tech will immediately blame the flipper coil itself for weak or non-functioning flippers. It is logical to blame the coil for the source of the problem. The flipper coil is, after all, the end reason why a flipper becomes engaged. However, its failure is the least probable reason that a flipper is not working. 

====Flipper does not work====
In this case, you've started a game, you press the flipper cabinet switch, and nothing happens.

The first thing to do is inspect the wire connections to the flipper coil lugs. The most common reason a WPC flipper does not function is that either one of the wires broke from the game to the lug, or one of the coil winding wires, has broken away from the coil lug and is no longer connected to the coil. This is a pretty simple fix. Make a clean cut to the wire, strip or sand 1/4" to 3/8" of insulation back, and make a nice solder joint on the coil.

[[Image:WPC95FlipperSpadeConnectors.jpg|300px|thumb|left|A good reason to nip spade connectors off and solder directly to the coil lug. This spade connector simply fell off the coil lug. Luckily, it didn't come to rest on an adjacent lug.]] 
Some WPC-95 titles used "spade connectors" (also known as FASTON connectors) to attach wires to the coil lugs. This was done for ease of manufacture and for that reason only. Similar to a wire breaking free, these spade connectors sometimes do not provide a solid connection and sometimes simply fall off. In that case, cut the spade connector off and solder the wire directly to the coil lug. This makes a much better connection that is also much more reliable. Should a spade connector fall onto an adjacent coil lug, it's very possible that a short circuit will be created, possibly damaging the FlipTronics board. 

=====Mechanical Reasons=====
There are a couple of mechanical reasons a flipper may not be working, including:
*Broken flipper link
*Flipper crank not "biting" flipper shaft (this would most likely manifest as a flipper that continues to move backwards, out of adjustment)

Simple inspection of the flipper mechanism should guide your corrective actions.

=====Pre-FlipTronics Games Electrical Reasons=====
*Failed flipper power supply - make sure that DC flipper power is present at the coil using your DMM. Place the red lead on a coil lug, the black lead on game ground (siderail or ground braid anywhere in the game). You should read about 70VDC.
*Flipper cabinet switch not "making" or fouled so badly that it doesn't conduct flipper power
*Fouled or missing flipper end-of-stroke switch. Pre-FlipTronics games relied on EOS switches in the same way that older games do. That is, power is routed to the power stroke winding of the coil via the EOS switch. If the EOS switch is fouled, only the hold winding will receive power; perhaps inadequate to move the flipper at all.

=====FlipTronics Games Electrical Reasons=====
*Failed flipper power supply. Flipper power originates at the transformer. It is routed through the power/driver board (which does nothing to it) and then to the FlipTronics board. The FlipTronics board rectifies the AC power via an onboard bridge rectifier. Power may be interrupted anywhere along this path, including a failed bridge rectifier or blown fuse.
*Failed flipper coil "power stroke" winding
*Flipper cabinet switch not "making" or flipper opto board not working
*Damaged connection between flipper cabinet switch and FlipTronics board
*FlipTronics board not recognizing flipper cabinet button switch closure
[[File:MissingPinFlipTronics.jpg|300px|thumb|left|A missing pin in the FlipTonics-to-MPU interface. The missing pin prevented transmission of the F8 signal (D7), which is the upper left flipper switch closed signal.]] 
An unusual reason for the flipper switch closure signal not being sent to the MPU is shown at left. 
*Failed logic path on the FlipTronics board including the transistors. See: [[Williams_WPC#WPC_FlipTronics_I_.26_II_Boards| WPC FlipTronics I and II Boards]] for a description of the signal path.
*Improperly seated or failed ribbon connectors between MPU and FlipTronics board

====Flipper is weak====
In this case, the flipper makes a stroke, but it's a weak stroke, not striking the ball with normal force.

=====Mechanical Reasons=====
*Not enough vertical movement in flipper bat (crank tightened too close to bushing)
*Cracked, broken or egged flipper bushing
*Mushroomed coil stop and plunger (replace coil sleeve too)
*Missing link bushing or oval link "eyelet"
*Tired flipper crank (will not tighten on bat shaft)

[[File:WPC Flipper Link Plunger.JPG|thumb|left|300px|An Example of an Egged Flipper Link and Mushroomed Flipper Plunger - Lower Link and Plunger Shown in Picture is new]]
 

=====Pre-FlipTronics Games Electrical Reasons=====
*Flipper cabinet switch not "making" or fouled so badly that it does not conduct
*Failed flipper end-of-stroke switch

=====FlipTronics Games Electrical Reasons=====

*Dirty flipper cabinet switch optos
*Power stroke winding of coil failed
*Failed or partially failed bridge rectifier on the FlipTronics II board or on the 50V power supply board as used in The Addams Family

====Flipper locks on or fails to fall to resting position====
In this case, the flipper locks in the up position, either at game power on or when the flipper cabinet switch is pressed.

=====Mechanical Reasons=====

=====Pre-FlipTronics Games Electrical Reasons=====

=====FlipTronics Games Electrical Reasons=====
*Flipper cabinet switch opto interupter not returning to proper at rest position
*Sticky flipper buttons, which can lead to opto interupter not returning to at rest position.

=====Fodder (may be useful to complete this section)=====
*Fouled or broken "normally closed" EOS switch
*Fouled or broken flipper cabinet switch
*Flipper relay not enabled
*Fouled / dirty or non-functioning flipper opto switches
*Upper flipper switch closures in switch test, when there aren't any upper flippers on game

==Parts Substitutions & Replacements==
===WPC-95 A/V Board RAM chips===
If one of the 65764 RAM chips needs to be replaced, but is unavailable, according to [https://pinside.com/pinball/forum/topic/wpc-95-av-board-1/page/3#post-8884790 this discussion on Pinside], IS61C256AH-15N RAM chips can be used as a replacement. However, since the address lines are different between the two different chips, all three RAM chips will need to be replaced with IS61C256AH-15N in order for the address lines on the chips to match up with each other.

==Repair Logs and Game Specific Problems and Fixes==
Since WPC games are overwhelmingly the most popular pinball titles at the moment, and there are a vast amount of titles with so many game specific issues, please refer to the [http://pinwiki.com/wiki/index.php?title=Williams_WPC#Game_List Game List] section of this guide. Click on the specific game, and a new page will open regarding repair logs and game specific problems and fixes for that particular game title.
 

=== World Cup Soccer locks on Right Sling and both Left and Right Kickout Holes at Power On ===
[[Image:WPCDriverBoardKeying.jpg|400px|thumb|left|Board layout diagram showing identical connector and keying at J124, J128, and J132)]] 
[[Image:WPCJ124J128Keying.jpg|400px|thumb|left|Image showing identical connector and keying at J124, J128, and J132)]] 
<ul>Problem</ul>
Upon power on, and with the coin door closed (defeating the high voltage interlock switch), the right slingshot as well as the left and right saucer kickout hole coils lock on.

<ul>Cause</ul>
The flash lamp drive connector that should be connected to J124 is instead connected to J128.

<ul>Discussion</ul>
Connecting the female plug to the wrong header pins is entirely possible since the connectors are the same width and are keyed identically. In World Cup Soccer (at least), the wire bundle is long enough to be connected (properly) to J124 or (improperly) to J128 or J132.
 

===S2 Sound ROM Failure on WPC-95 After a Successful Boot===
[[File:AnotherWPCCrackedASICSocket.jpg | thumb | left| 300px| An ASIC socket that has been cracked by using the wrong tool to remove the ASIC.]] 
If game is turned on and has a successful boot, but after a few minutes, the game bongs twice indicating an S2 sound ROM failure and becomes unresponsive, try reseating the ASIC chip on the MPU. Make sure to use the proper removal tool and not a screwdriver. Using an improper tool will damage the chip and/or socket.
 

===Replacement for opto part number QVE11233.0086 as used on Corvette and Twilight Zone ===

The QVE11233.0086 optos were specially screened for Williams production. They were used in the Twilight Zone clock and the Corvette race track. These special optos are no longer (easily) available.

Possible substitutions may be:
*H22B2 (found on AliExpress, tested and working in Corvette, has a gap of 3mm as opposed to 3.8mm on the original optos), and
*KTIR0621DS (not tested, has a wider gap of 5mm). 

=== Dr. Who Playfield Glass Present Switch ===
[[File:DrWhoTimeExpander.jpg ‎‎|300px|thumb|left|Heed the warning.]]

Dr. Who is unique in that it has a switch installed on the cabinet inside, top left, which indicates that the playfield glass is installed. When this switch opens, a loud safety message is voiced along with a message on the DMD display. These messages are meant to alert repairmen to the safety issue with the "Time Expander" Mini Playfield.

The mini playfield has no "bind detected" mechanism as a garage door might have. If something becomes jammed in the mechanism, like a finger, the motor will continue to run, possibly causing serious injury.

Defeating this switch is not advised. Extreme caution is certainly warranted.

File:Opto-board-schematic-demo.gif

2026-09-25T18:16:31Z

The Hammer: A GIF demonstrating the operation of one section of a Williams WPC opto board.

== Summary ==
A GIF demonstrating the operation of one section of a Williams WPC opto board.

Talk:Williams WPC

2026-09-19T21:00:07Z

The Hammer: /* WPC 10 Opto Board Problems */

We should push game-specific comments into the game page. Having them all up front is messy. We can always create compendium pages later.--[[User:Mr|Mr]] 04:04, 7 May 2011 (BST)

Hey Martin...I agree...After the other reorganizing I did...I ran out of energy.
BTW, I made a new page called "WPC DMD Controller Board"...just to be a bit more consistent with other namings. I copied your crack at it into that page. I don't know how to delete old pages.
--Chris Hibler 04:49, 7 May 2011 (BST)

OK Martin, et.al....moved game specific issues and fixes to a subpage for now...Eventually, these should be moved to the game specific page. 
--Chris Hibler 04:58, 7 May 2011 (BST)

Moved all game specific issues to the game's subpage...
--Chris Hibler 03:58, 9 May 2011 (BST)

OK, I am going to push a few other repairs into their appropriate pages. --[[User:Mr|Mr]] 07:16, 21 May 2011 (BST)

Dielectric grease is not conductive

Corrected pin count on ASIC 108->84. TerryB 10:49, 7 Jan 2016 (PST)

== WPC 10 Opto Board Problems ==

"Sometimes the switch edge test can show one or multiple opto switches flickering open and closed."

I am looking for clarification on this statement. Will it only affect other optos or will it also affect physical switches which would only be apparent if they are closed?

I am guessing from that statement that this would affect all switches on either the columns and/or rows that are connected to this 10 Opto Board, but I am looking for confirmation.

For example, if U2 were affected, that could affect on column (labelled as column 1 in the schematic but can be any column in the switch matrix).
It might also affect rows 5, 6 & 7 as U2 is connected to one column and three rows. U1 would affect rows 1 - 4. U3 would affect rows 1 - 3 and one column (labelled 2 in the schematic).[[User:The Hammer|The Hammer]] ([[User talk:The Hammer|talk]]) 16:00, 19 September 2026 (CDT)

Talk:Williams WPC

2026-09-19T20:59:15Z

The Hammer: /* WPC 10 Opto Board Problems */

Talk:Williams WPC

2026-09-19T14:49:54Z

The Hammer: /* WPC 10 Opto Board Problems */

Talk:Williams WPC

2026-09-19T14:48:40Z

The Hammer: /* WPC 10 Opto Board Problems */

We should push game-specific comments into the game page. Having them all up front is messy. We can always create compendium pages later.--[[User:Mr|Mr]] 04:04, 7 May 2011 (BST)

Hey Martin...I agree...After the other reorganizing I did...I ran out of energy.
BTW, I made a new page called "WPC DMD Controller Board"...just to be a bit more consistent with other namings. I copied your crack at it into that page. I don't know how to delete old pages.
--Chris Hibler 04:49, 7 May 2011 (BST)

OK Martin, et.al....moved game specific issues and fixes to a subpage for now...Eventually, these should be moved to the game specific page. 
--Chris Hibler 04:58, 7 May 2011 (BST)

Moved all game specific issues to the game's subpage...
--Chris Hibler 03:58, 9 May 2011 (BST)

OK, I am going to push a few other repairs into their appropriate pages. --[[User:Mr|Mr]] 07:16, 21 May 2011 (BST)

Dielectric grease is not conductive

Corrected pin count on ASIC 108->84. TerryB 10:49, 7 Jan 2016 (PST)

== WPC 10 Opto Board Problems ==

"Sometimes the switch edge test can show one or multiple opto switches flickering open and closed."

I am looking for clarification on this statement. Will it only affect other optos or will it also affect physical switches which would only be apparent if they are closed?

I am guessing from that statement that this would affect all switches on either the columns and/or rows that are connected to this 10 Opto Board, but I am looking for confirmation.

For example, if U2 were affected, that could affect on column (labeled as column 1 in the schematic but can be any column in the switch matrix).
It might also affect rows 5, 6 & 7 as U2 is connected to one column and three rows. U1 would affect rows 1 - 4. U3 would affect rows 1 - 3 and one column (labelled 2 in the schematic).

Talk:Williams WPC

2026-09-19T14:46:04Z

The Hammer: /* WPC 10 Opto Board Problems */ new section

We should push game-specific comments into the game page. Having them all up front is messy. We can always create compendium pages later.--[[User:Mr|Mr]] 04:04, 7 May 2011 (BST)

Hey Martin...I agree...After the other reorganizing I did...I ran out of energy.
BTW, I made a new page called "WPC DMD Controller Board"...just to be a bit more consistent with other namings. I copied your crack at it into that page. I don't know how to delete old pages.
--Chris Hibler 04:49, 7 May 2011 (BST)

OK Martin, et.al....moved game specific issues and fixes to a subpage for now...Eventually, these should be moved to the game specific page. 
--Chris Hibler 04:58, 7 May 2011 (BST)

Moved all game specific issues to the game's subpage...
--Chris Hibler 03:58, 9 May 2011 (BST)

OK, I am going to push a few other repairs into their appropriate pages. --[[User:Mr|Mr]] 07:16, 21 May 2011 (BST)

Dielectric grease is not conductive

Corrected pin count on ASIC 108->84. TerryB 10:49, 7 Jan 2016 (PST)

== WPC 10 Opto Board Problems ==

"Sometimes the switch edge test can show one or multiple opto switches flickering open and closed."

I am looking for clarification on this statement. Will it only affect other optos or will it also affect physical switches which would only be apparent if they are closed?

I am guessing from that statement that this would affect all switches on either the columns and/or rows that are connected to this 10 Opto Board, but I am looking for confirmation.

For example, if U2 were affected, that could affect two columns (labeled as columns 1 & 2 in the schematic but can be any two columns in the switch matrix).
It might also affect rows 5, 6 & 7 as U2 is connected to those two columns and three rows. U1 would affect rows 1 - 4. U3 would affect rows 1 - 3.

User:The Hammer

2026-09-18T19:18:10Z

The Hammer: Created page with "Larry Hammer has been working on pinball machines since the early 1970's. His first pin was one that his father-in-law gave his wife when she was a kid. It was a Gottlieb Atlas EM. His hobby has always included electronics. He first played around with his parents "black and white" CRT TV and brushed against the B+ voltage which threw him back against the wall. He was 8 years old. Through the years, he built many HealthKits, Dynaco, Eico, and others. These kits incl..."

Larry Hammer has been working on pinball machines since the early 1970's. His first pin was one that his father-in-law gave his wife when she was a kid. It was a Gottlieb Atlas EM.

His hobby has always included electronics. He first played around with his parents "black and white" CRT TV and brushed against the B+ voltage which threw him back against the wall. He was 8 years old.

Through the years, he built many HealthKits, Dynaco, Eico, and others. These kits included stereos, FM tuners, "color" TVs and several others including test equipment (signal generators, oscilloscopes, etc.), all without getting killed once.

He later repaired electronics equipment for friends, family and himself for fun.

After playing around with early generation computers, the pinball bug bit him again hard and he feverishly collected them during the 1990's and on as the arcades shut down.

Now, during retirement, he volunteers at the Roanoke Pinball Museum and tries to help out more than he annoys, not always successfully.

Williams WPC

2026-06-19T19:33:33Z

The Hammer: /* WPC FlipTronics I & II Boards */ Using the Williams Fliptronics 2 Board in The Addams Family

Click to go back to the [[Williams_Repair_Guides | Williams solid state repair guides index]].

==Introduction==
This guide covers Williams WPC-089, WPC-S, and WPC-95 games. Collectively, they are referred to as WPC games.

==Game List==
===WPC (WPC-089) CPU===
====WPC (Alphanumeric)====
*[[Funhouse]]
*[[Harley-Davidson]]
*[[The Machine: Bride of Pin*Bot]]

====WPC (Dot Matrix)====
*[[Gilligan's Island]]
*[[Terminator 2: Judgement Day]]
*[[Hurricane]]
*[[Party Zone]]

====WPC FlipTronics I & II====
*[[The Addams Family]] / Addams Family Gold (the only Fliptronics I games)
*[[The Getaway: High Speed II]]
*[[Black Rose]]
*[[Fish Tales]]
*[[Doctor Who]]
*[[Creature from the Black Lagoon]]
*[[White Water]]
*[[Bram Stoker's Dracula]]
*[[Twilight Zone]]

====WPC DCS Sound====
*[[Indiana Jones: The Pinball Adventure]]
*[[Judge Dredd]]
*[[Star Trek: The Next Generation]]
*[[Popeye Saves The Earth]]
*[[Demolition Man]]

===WPC-S with DCS Sound===
*[[World Cup Soccer]]
*[[The Flintstones]]
*[[Corvette]]
*[[Red & Ted Road Show]]
*[[The Shadow]]
*[[Dirty Harry]]
*[[Theatre of Magic]]
*[[No Fear: Dangerous Sports]]
*[[Indianapolis 500]]
*[[Johnny Mnemonic]]
*[[Jack*Bot]]
*[[WHO Dunnit]]

===WPC-95 CPU===
*[[Congo]]
*[[Attack from Mars]]
*[[Safecracker|Safe Cracker]]
*[[Tales of the Arabian Nights]]
*[[Scared Stiff]]
*[[Junk Yard]]
*[[NBA Fastbreak]]
*[[Medieval Madness]]
*[[Cirqus Voltaire]]
*[[No Good Gofers]]
*[[The Championship Pub|The Champion Pub]]
*[[Monster Bash]]
*[[Cactus Canyon]]

==Game List Chart==

===WPC-89 & WPC-S===

{| class="wikitable sortable"
|-
!Game
!WPC System
!MPU
!Driver Board
!Display Driver
!Display
!Sound
!Flipper
!Transformer
!Additional Boards
!Notes

|-
|[[Dr. Dude]]
|WPC-89 Alphanumeric / System 11
|WPC-89 (A-12742)
|A-12697-1
|A-12739-1
|Alphanumeric, dual display (A-12793)
|D-11581-2016 with a special power supply board (A-13502)
|N/A
|5610-12718-00 (WPC) or 5610-12136-00 (System 11)?
|Sound overlay board (A-13502)
|Only about 100 Dr. Dude sample games use the WPC boardset. They included a special power supply board (A-13502) to accommodate the System 11 sound board (D-11581), and also includes the System 11 interconnect board (D-12313-2016). The bulk of the production run used the [[Williams System 9 - 11|System 11C boardset]].
|-

|-
|[[Funhouse]]
|WPC-89 Alphanumeric
|WPC-89 (A-12742)
|A-12697-1
|A-12739-1
|Alphanumeric, dual display (A-12793)
|A-12738-50003
|N/A
|5610-12718-00
|
|Early FH games had a System 11 sound board (D-11581 / A-13971) with a special power supply board (A-13502) and a 5610-12425-00 transformer. Later games used the WPC A-12738 sound board. [[media: Williams_1990_Funhouse_Prototype_Manual_Addendum.pdf|Funhouse Manual Addendum]]
|-

|[[Harley-Davidson]]
|WPC-89 Alphanumeric
|WPC-89 (A-12742)
|A-12697-1
|A-12739-1
|Alphanumeric, single display (A-12794)
|A-12738-20001
|N/A
|5610-12718-00
|
|
|-

|[[The Machine: Bride of Pin*Bot]]
|WPC-89 Alphanumeric
|WPC-89 (A-12742)
|A-12697-1
|A-12739-1
|Alphanumeric, dual display (A-12793)
|A-12738-50002
|N/A
|5610-12718-00
|
|
|-

|[[Slugfest]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-60001
|N/A
|5610-12835-00
|
|Pitch & Bat game.
|-

|[[Gilligan's Island]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20003
|N/A
|5610-12835-00
|
|
|-

|[[Terminator 2: Judgement Day]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50013
|N/A
|5610-12835-00
|
|
|-

|[[Hurricane]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50012
|N/A
|5610-12835-00
|
|
|-

|[[Party Zone]]
|WPC-89 Dot Matrix / WPC-89 Fliptronic I
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20004
|N/A
|5610-12835-00
|
|Some later PZ games started transitioning over to use the Fliptronic I board (A-15028). Different game ROMs are used depending upon if the PZ uses solid state flippers or fliptronic/standard flippers.
|-

|[[Hot Shot]]
|WPC-89 Dot Matrix
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50017
|N/A
|5610-12835-00
|
|Redemption game.
|-

|[[The Addams Family]]
|WPC-89 Fliptronic I
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20017
|A-15028
|5610-12835-00
|Extra flipper power supply (A-15416)
|
|-

|[[The Getaway: High Speed II]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50004
|A-15472
|5610-12835-00
|
|
|-

|[[Black Rose]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20013
|A-15472
|5610-12835-00
|
|
|-

|[[Doctor Who]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20006
|A-15472
|5610-12835-00
|
|
|-

|[[Fish Tales]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50005
|A-15472
|5610-12835-00
|
|
|-

|[[Creature from the Black Lagoon]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-20018
|A-15472
|5610-12835-00
|
|
|-

|[[White Water]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50018
|A-15472
|5610-12835-00
|
|
|-

|[[Bram Stoker's Dracula]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-12738-50001
|A-15472
|5610-12835-00
|
|
|-

|[[Twilight Zone]]
|WPC-89 Fliptronic II
|WPC-89 (A-12742)
|A-12697-1 or A-12697-3
|A-14039
|DMD
|A-12738-50020
|A-15472
|5610-12835-00
|Auxiliary 8-Driver PCB (A-16100)
|Mid-way through TZ's production run, the A-12697-1 driver board starting being replaced with A-12697-3. At some point during production, a coin door interlock switch was added in order to cut high voltage 20VDC/50VDC power as a safety measure when the coin door was opened; this was included in all WPC titles from this point forward.
|-

|[[Indiana Jones: The Pinball Adventure]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-3
|A-14039
|DMD
|A-16917-50017
|A-15472-1
|5610-13491-00
|Auxiliary 8-Driver PCB (A-16100)
|
|-

|[[Judge Dredd]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-3
|A-14039
|DMD
|A-16917-20020
|A-15472-1
|5610-13491-00
|
|
|-

|[[Star Trek: The Next Generation]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-1
|A-14039
|DMD
|A-16917-50023
|A-15472-1
|5610-13491-00
|Auxiliary 8-Driver PCB (A-16100)
|Driver board was changed to A-12697-1.
|-

|[[Demolition Man]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-3
|A-14039
|DMD
|A-16917-50028
|A-15472-1
|5610-13953-00
|Auxiliary 8-Driver PCB (A-16100)
|A few prototype games used a WPC-S MPU, which uses a different ROM in order to work with the WPC-S security PIC. The standard ROM for WPC-89 boards will not work on the WPC-S board, but a WPC-89 MPU can be swapped in to replace the WPC-S MPU. All the sample and production games used a WPC-89 MPU.
|-

|[[Popeye Saves The Earth]]
|WPC-DCS
|WPC-89 (A-12742)
|A-12697-3
|A-14039
|DMD
|A-16917-50022
|A-15472-1
|5610-13491-00
|
|
|-

|[[World Cup Soccer]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039
|DMD
|A-16917-50031
|A-15472-1
|5610-13953-00
|
|
|-

|[[The Flintstones]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50029
|A-15472-1
|5610-13953-00
|
|Some revisions were made on the A-14039.1 DMD driver board, but it is interchangeable with A-14039.
|-

|[[Corvette]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50036
|A-15472-1
|5610-13953-00
|Auxiliary 8-Driver PCB (A-16100)
|
|-

|[[Red & Ted Road Show|Red & Ted's Road Show]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50024
|A-15472-1
|5610-13953-00
|Auxiliary 8-Driver PCB (A-16100)
|The transformer was moved to the rear of the cabinet starting with this game.
|-

|[[The Shadow]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50032
|A-15472-1
|5610-13953-00
|
|
|-

|[[Dirty Harry]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50030
|A-15472-1
|5610-13953-00
|
|
|-

|[[Theatre of Magic]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50039
|A-15472-1
|5610-14515-00
|
|
|-

|[[No Fear: Dangerous Sports]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50025
|A-15472-1
|5610-14515-00
|
|
|-

|[[Indianapolis 500]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50026
|A-15472-1
|5610-14515-00
|
|
|-

|[[Johnny Mnemonic]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50042
|A-15472-1
|5610-14515-00
|
|
|-

|[[WHO Dunnit]]
|WPC-S
|WPC-S (A-17651)
|A-12697-4
|A-14039.1
|DMD
|A-16917-50044
|A-15472-1
|5610-14515-00
|
|This was the only game to use a A-12697-4 driver board.
|-

|[[Jack*Bot]]
|WPC-S
|WPC-S (A-17651)
|A-12697-3
|A-14039.1
|DMD
|A-16917-50051
|A-15472-1
|5610-14515-00
|
|
|-
|}

===WPC-95===

{| class="wikitable sortable"
|-
!Game
!WPC System
!MPU
!Driver Board
!AV Board
!Display
!Transformer
!Additional Boards
!Notes
|-

|[[Congo]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|The first WPC-95 game. The A-20516 AV Board drives both sound and the DMD. The A-20028 driver board included flipper power circuits, eliminating the need for a separate fliptronic board.
|-

|[[Attack from Mars]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[safecracker|Safe Cracker]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[Ticket Tac Toe]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|?
|
|Redemption game (with flippers).
|-

|[[Tales of the Arabian Nights]]
|WPC-95
|WPC-95 (A-20119)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[Scared Stiff]]
|WPC-95
|WPC-95 (A-20119 or A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|The first appearance of a revision to the MPU. A-20119 and A-21377 can be used interchangeably in any WPC-95 games.
|-

|[[Junk Yard]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[NBA Fastbreak]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-01
|
|
|-

|[[Medieval Madness]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-01
|
|
|-

|[[Cirqus Voltaire]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|DMD is mounted on the playfield, rather than in the backbox.
|-

|[[No Good Gofers]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[The Championship Pub|The Champion Pub]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-00
|
|
|-

|[[Monster Bash]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-01
|
|
|-

|[[Cactus Canyon]]
|WPC-95
|WPC-95 (A-21377)
|A-20028
|A-20516
|DMD
|5610-14515-01
|
|
|-

|}

==Recommended Documentation==
===Manuals & Schematics===
Schematics for each game are essential in tracing down connections to lamps, switches, and solenoids. The owner's game manual is a handy resource to have for general game operation, game settings & diagnostics, switch & lamp matrices, fuse lists, circuit boards and parts, playfield assemblies, some basic schematics, and wiring diagrams.

Be aware that although rare, some factory documentation contains errors in schematics, wiring, switch/lamp matrices, and solenoid assignments.

Some games have information split between two manuals: a game manual (for general game operation) and an operations guide (for more technical information).

{| class="wikitable"
|-
!Guide
!Version
!Cover
!Source
!Notes

|-
|Pinball Safety Manual
|16-10371, January 1, 1997
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Manual contains multiple languages.

|}

===Theory of Operation & Schematics===
Details for board and cabinet schematics and theory of operation guides for WPC games can be found in separate documents. There are several versions of each generation. Some copies can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball].

{| class="wikitable"
|-
!Guide
!Version
!Cover
!Source
!Notes

|-
|WPC Theory of Operation and Schematics Manual
|16-9289, October 1991
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/djtz/ Viewer for Guide] [https://online.fliphtml5.com/vrtyz/pgds/ Viewer for Schematics]
|

|-
|WPC Schematic Manual
|16-9473 (undated)
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.

|-
|WPC Schematic Manual
|16-9473-1, May 17, 1993
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/wrhm/ Viewer] [[media:Williams-WPC-Schematics_16-9473-1.pdf|PDF]]
|Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.

|-
|WPC Schematic Manual
|16-9473-2, April 25, 1994
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.

|-
|WPC Schematic Manual
|16-9834, June 1994
|[[file:placeholder.jpg|thumb|left|140px]]
|
|

|-
|WPC Schematic Manual
|16-9834.2, January 1995
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/fsgs/ Viewer]
|

|-
|WPC-S (Security) Schematic Manual
|
|[[file:placeholder.jpg|thumb|left|140px]]
|
|

|-
|WPC-95 Schematic Manual
|16-10159.2, March 1996
|[[file:placeholder.jpg|thumb|left|140px]]
|
|

|-
|WPC-95 Schematic Manual
|16-10159.3, July 1997
|[[file:placeholder.jpg|thumb|left|140px]]
|[[media:Williams-WPC-95-Schematics-Manual_16-10159.3.pdf|PDF]]
|

|}

===Parts Catalogs===
Parts catalogs can also be useful, which include part numbers (helpful for purchasing parts online), exploded views of assemblies (helpful to see how the assemblies are put together), and board layouts & parts lists, and diagrams for controlled lamp, solenoid, and rubber locations. Parts catalogs also had supplementary updates to add and replace pages as newer games were released after the initial release of the catalogs.

Online copies of Bally & Williams parts catalogs can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball].

{| class="wikitable"
|-
!Manufacturer
!Catalog
!Version
!Cover
!Source
!Games
!Notes

|-
|Williams
|Blue Parts Catalog (1984-1987)
|16-9064
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Comet, F-14 Tomcat, Grand Lizard, High Speed, Millionaire, Pin Bot, Road Kings, Sorcerer, Space Shuttle
|This was an early version of the blue parts catalog, and only included 9 pinball titles (and 3 shuffle alley titles). The pages of this catalog were printed on white paper. Additional titles were later included in a "parts catalog supplement" packet (16-9064-A) with blue-colored pages, which added and replaced pages for this earlier version of the parts catalog.

|-
|Williams
|Blue Parts Catalog (Supplementary Catalog) (1987-1988)
|16-9064-A
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Banzai Run, Big Guns, Cyclone, Fire!, Space Station, Swords of Fury, Taxi
|This "parts catalog supplement" packet with blue-colored pages added and replaced pages for the earlier version of the parts catalog. It included 7 new pinball titles not included in the previous version of the parts catalog. Later catalogs had these new pages included and were not colored blue.

|-
|Williams
|'''Blue Parts Catalog (1984-1989)'''
|'''16-9064-B'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/rvsk/ Viewer] [[media:Williams-parts-catalog-blue-book_16-9064-B.pdf|PDF]]
|Banzai Run, Big Guns, Black Knight: 2000, Comet, Cyclone, Earthshaker!, F-14 Tomcat, Fire!, Grand Lizard, High Speed, Jokerz!, Millionaire, Pin Bot, Police Force, Road Kings, Sorcerer, Space Shuttle, Space Station, Swords of Fury, Taxi
|This is the latest version of the blue parts catalog. It included the game titles in the previous version, information from the supplementary parts catalog, a few new pinball titles, and a total of 5 shuffle alley titles. The blue parts catalog came in a blue-colored binder with the catalog's cover and game titles printed on the front, and basic information printed on the spine. The pages of this catalog were printed on pink paper.

|-
|Williams
|Red Parts Catalog (1989-1990)
|16-9190
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Bad Cats, Diner, Rollergames, Whirlwind
|The red parts catalog came in a red-colored binder with some basic information printed on the cover and spine. This version of the parts catalog included 4 pinball titles and 2 shuffle alley titles. The pages were printed on white-colored paper.

|-
|Williams
|Red Parts Catalog
|16-9190-A
|[[file:placeholder.jpg|thumb|left|140px]]
|
|(currently unverified)
|The red parts catalog came in a red-colored binder with some basic information printed on the cover and spine. This was a supplementary parts catalog that updated pages and added titles to the previous version of the red parts catalog. The pages were printed on blue-colored paper.

|-
|Williams
|'''Red Parts Catalog (Supplementary Catalog) (1989-1992)'''
|'''16-9190-B'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/feme/ Viewer] [[media:Williams-parts-catalog-red-book_16-9190-B.pdf|PDF]]
|Bad Cats, Diner, Dracula, Fish Tales, Funhouse, The Getaway, Hurricane, The Machine: Bride of Pin Bot, Riverboat Gambler, Rollergames, Slugfest, Terminator 2, Whirlwind, White Water
|The red parts catalog came in a red-colored binder with some basic information printed on the cover and spine. This version of the parts catalog included 13 pinball titles, and 5 shuffle alley titles, 7 video came titles, and 3 novelty game titles. The pages were printed on gray-colored paper.

|-
|Bally/Midway
|Yellow Parts Catalog (1988-1990)
|16-9147
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Atlantis, Elvira, Game Show, Mousin' Around, Transporter, Truck Stop
|The yellow parts catalog came in a yellow-colored binder with some basic information printed on the cover and spine. The pages were printed on white-colored paper.

|-
|Bally/Midway
|Yellow Parts Catalog (Supplementary Catalog) (1988-1991)
|16-9147-A
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Atlantis, Bugs Bunny, Dr. Dude, Elvira, Game Show, Harley Davidson, Mousin' Around, Pool Sharks, Radical!, Transporter, Truck Stop
|The yellow parts catalog came in a yellow-colored binder with some basic information printed on the cover and spine. This was a supplementary update to the previous version of the catalog, which included 11 pinball titles and 4 video game titles. The pages were printed on yellow-colored paper.

|-
|Bally/Midway
|'''Yellow Parts Catalog (1988-1992)'''
|'''16-9147-B'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/itjk/ Viewer] [[media:Bally-midway-parts-catalog-yellow-book_16-9147-B.pdf|PDF]]
|Addams Family, Atlantis, Black Rose, Bugs Bunny, Dr. Dude, Doctor Who, Elvira, Game Show, Gilligan's Island, Harley Davidson, Mousin' Around, Party Zone, Pool Sharks, Radical!, Transporter, Truck Stop
|The yellow parts catalog came in a yellow-colored binder with some basic information printed on the cover and spine. The pages were printed on gold-colored paper.

|-
|Bally/Midway
|Gray Parts Catalog (1992-1994)
|16-9562
|[[file:placeholder.jpg|thumb|left|140px]]
|
|Creature From the Black Lagoon, Judge Dredd, Popeye Saves the Earth, Twilight Zone
|The gray parts catalog came in a white-colored binder with gray colored paper inserts for the spine and cover that included the company name, parts catalog, and part number. The pages were printed on white-colored paper.
|-
|Bally/Midway
|'''Gray Parts Catalog (Supplementary Catalog) (1992-1995)'''
|'''16-9562-A'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/ckao/ Viewer] [[media:Bally-midway-parts-catalog-gray-book_16-9562-A.pdf|PDF]]
|Addams Family Gold, Corvette, Creature From the Black Lagoon, Indianapolis 500, Judge Dredd, Popeye Saves the Earth, The Shadow, Theatre Of Magic, Twilight Zone, Who Dunnit, World Cup Soccer
|The gray parts catalog came in a white-colored binder with gray colored paper inserts for the spine and cover that included the company name, parts catalog, and part number. This was a supplementary update to the previous version of the catalog. The pages were printed on light blue colored paper.

|-
|Williams
|'''Green Parts Catalog (1993-1995)'''
|'''16-9932'''
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/foky/ Viewer] [[media:Williams-parts-catalog-green-book_16-9932.pdf ‎|PDF]]
|Demolition Man, Dirty Harry, Demolition Man, Indiana Jones, Road Show, Star Trek - Next Generation
|The green parts catalog came in a white-colored binder with green colored paper inserts for the spine and cover that included the company name, parts catalog, and part number. There was no supplementary update to this catalog.

|-
|Williams
|'''Genuine Replacement Parts Catalog (1997-1998)'''
|10/97
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/yjjv/ Viewer]
|
|This catalog mainly provides listings, parts numbers, and drawings of commonly replaceable generic pinball parts for Bally/Williams games, such as flipper assembly parts, target parts, posts, springs, connectors, coils, plungers, etc. It does not contain any game-specific information.

|}

===Service Bulletins===
Supplementary service bulletin books were released, which included service bulletins that detailed any problems or issues with games that were discovered after they were released.

{| class="wikitable"
|-
!Manufacturer
!Catalog
!Cover
!Source
!Games
!Notes

|-
|Williams
|Service Bulletin Book, 1991
|[[file:Williams-1991-service-bulletin-book-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1991.pdf|PDF]]
|Funhouse, Gilligan's Island, Harley Davidson, Slugfest, Terminator 2
|This book includes some System 11 games.

|-
|Williams
|Service Bulletin Book, 1992
|[[file:Williams-1992-service-bulletin-book-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1992.pdf|PDF]]
|Addams Family, Funhouse, Hurricane, Party Zone, Terminator 2
|

|-
|Williams
|Service Bulletin Book, Fall 1992
|[[file:Williams-1992-fall-service-bulletin-book-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1992-fall.pdf|PDF]]
|Addams Family, The Getaway, Strike Master (shuffle alley)
|

|-
|Williams
|Service Bulletin Book, 1993
|[[file:Williams-1993-service-bulletin-book-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1993.pdf|PDF]]
|Black Rose, Creature From the Black Lagoon, Doctor Who, Dracula, Fish Tales, NBA Jam, White Water
|

|-
|Williams
|Service Bulletin Book, 1994
|[[file:Williams-service-bulletin-book-1994-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1994.pdf|PDF]]
|Dracula, Indiana Jones, Judge Dredd, Star Trek the Next Generaton, Twilight Zone
|

|-
|Williams
|Service Bulletin Book, Fall 1994
|[[file:Williams-service-bulletin-book-1994-fall-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1994-fall.pdf|PDF]]
|Popeye, Indiana Jones, Star Trek, Addams Family, Demolition Man, Flintstones
|

|-
|Williams
|Service Bulletin Book, 1995
|[[file:Williams-service-bulletin-book-1995-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1995.pdf|PDF]]
|World Cup Soccer, Corvette
|

|-
|Williams
|Service Bulletin Book, 1996
|[[file:Williams-service-bulletin-book-1996-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1996.pdf|PDF]]
|Congo, No Fear, Indianapolis 500, Jackbot, Johnny Mnemonic, Road Show, The Shadow, Theatre of Magic
|

|-
|Williams
|Service Bulletin Book, 1997
|[[file:Williams-service-bulletin-book-1997-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1997.pdf|PDF]]
|Johnny Mnemonic, Junkyard, Safecracker, Scared Stiff, Tales of the Arabian Nights
|The last service bulletin included in this book was service bulletin 96.

|-
|Williams
|Service Bulletin Book, 1998
|[[file:Williams-1998-service-bulletin-book-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1998-incomplete.pdf|PDF (incomplete)]]
|Scared Stiff, NBA Fastbreak, Cirqus Voltaire, Medieval Madness
|According to the [[media:Williams-service-bulletin-book-1998-index.jpg|table of contents]], this includes (pinball) service bulletins 98, 99, 101, 102, 104, and two others. The original color of the cover is currently unknown. The PDF scan only includes some of the Medieval madness service bulletin and the fastbreak link kit installation instructions.
|-

|Williams
|Service Bulletin Book, 1999
|[[file:placeholder.jpg|thumb|left|140px]]
|
|
|The original color of the cover is currently unknown. Dated September 10, 1999. Presumably includes at least (pinball) service bulletin 107.
|-
|}

Individual Game-Specific Service Bulletins:

{| class="wikitable sortable"
|-
!Service Bulletin
!Date
!Game(s)
!Subject
!Notes

|-
|[[media:Bally_1996_Scared_Stiff_Service_Bulletin_93.pdf|93]]
|1996-12-20
|Scared Stiff
|Solving mechanism problems
|
|-
|[[media:Bally_1996_Scared_Stiff_Service_Bulletin_98.pdf|98]]
|1997-05-01
|Scared Stiff
|Repair Kit for Left Ramp Assembly
|
|-
|[[media:Bally_1997_NBA_Fastbreak_Service_Bulletin_99.pdf|99]]
|1997-05-14
|NBA Fastbreak
|For a ball trap on the right ramp
|Ball trap fix
|-
|[[media:Bally_1997_Cirqus_Voltaire_Service_Bulletin_101.pdf|101]]
|1997-12-09
|Cirqus Voltaire
|Disappearing Jet Bumper assembly not releasing
|Applies to the first 200 sample games
|-
|[[media:Bally_1997_Cirqus_Voltaire_Service_Bulletin_102.pdf|102]]
|1997-12-09
|Cirqus Voltaire
|Upgrade Kit
|Installation instructions for Upgrade Kit #A-22270
|-
|[[media:Bally_1997_Cirqus_Voltaire_Service_Bulletin_104.pdf|104]]
|1998-04-02
|Cirqus Voltaire
|Cirqus Voltaire Adjustment Sheet
|Adjustment Sheet Update
|-
|?
|1998
|Medieval Madness
|Wireform Adjustment
|Catapult wireform adjustment (description of problem is currently missing, but assumed to help address ball jam issues in catapult wireform)
|-
|?
|1997-05-12
|NBA Fastbreak
|Link Kit
|Installation instructions for the link kit
|-
|[[media:Bally_1998_The_Champion_Pub_Service_Bulletin_107.pdf|107]]
|1998-12-28
|Champion Pub
|Champion Pub arms breaking prematurely
|
|-

|}

===Documentation Errors===
* Schematic errors in Addams Family & Addams Family Gold Manuals for the [[#TAF & TAFG Extra Flipper Power Supply (A-15416)|Extra Flipper Power Supply Board (A-15416)]].
* WPC Schematic Manual 16-9473 to 16-9473-2: Switch row 7 & 8 are reversed from what is printed. Row 7 should be pin 5 of U19, and row 8 should be pin 7 of U19.
* In Black Rose game manual, the coil/flasher listings at the front of the manual and in the section at the back of the manual that details connections are incorrect. See: [[#Coil_Locks_On_or_Flash_Lamp_Blows_at_Power_On|Coil Locks On or Flash Lamp Blows at Power On]]
*WPC-95 game manual J128 typo.
[[File:WPC95VoltageTypo.jpg|left|thumb|300px|Corrected WPC-95 (all games) manual]] 
It appears that all WPC-95 game manuals contain a typo for connector J128, pins 5/6 and 8/9. These two pairs of pins are shown to be connected to 16VAC from the transformer secondary. They are in fact connected to 50VAC from the transformer secondary.
 
* In the Indiana Jones Operations Manual (July 1993), Page 2-19 shows a diagram of the ''A-17073 Ball Eject Assembly - Special''. It incorrectly lists item #2 "Mounting Bracket Assembly" as part number A-8268 and the diagram incorrectly pictures A-8268. The correct part number is A-8268-1, which is a similar part, but oriented differently.

==Technical Info==
At the heart of the WPC MPU is the Motorola 68B09EP microprocessor, running at 2Mhz. Note that the "E" suffix indicates externally clocked and is necessary to work in a WPC MPU. The "P" suffix merely indicates a "plastic" chip case. 6809 processors lacking the "E" suffix will '''not''' work in a WPC MPU.

The 68B09EP is a 2Mhz, 8-bit/16-bit CPU, with a 64KB address space. Bank switching is required to address more than 64KB. Bank switching is accomplished by the ASIC in WPC systems. The game ROM size varies from 128KB to 8MB, depending on the game. 8KB of battery backed RAM is available to the processor.

For more information, see [https://web.archive.org/web/20110122183733/http://www.oddchange.com/freewpc/manual/The-WPC-Hardware.html The FreeWPC Manual (Archive.org link)]
===Inside WPC Game Backboxes===
<center>
<gallery widths=300px heights=300px perrow=3 caption="Typical WPC-089, WPC-DCS, and WPC-95 backbox configurations">
File:Placeholder.jpg |<center>WPC-089 pre-FlipTronics (Funhouse)</center>
File:WPCFlipTronics1.jpg |<center>WPC-089 pre-DCS with FlipTronics 1 (Addams Family, note separate 50V power supply board)</center>
File:Wpc-dcs-backbox-demolition-man.jpg ‎|<center>WPC-089 with DCS (Demolition Man)</center>
File:WPC-DCS-Backbox.jpg ‎|<center>WPC-S with DCS (Theatre of Magic)</center>
File:WPC95BackboxAFM.jpg |<center>WPC-95 (Attack From Mars, Color DMD Installed)</center>
</gallery>
</center>

===WPC Parts List Lookup===
A really nice utility has been put together by Øyvind Møll, enabling lookup of WPC parts. The utility can be used to see which games used particular parts. The utility can be found [http://www.moll.no/pinball/parts/ here].

===WPC System Generations===
====WPC CPU====
[[File:WPC-089_MPU.jpg|200px|thumb|right|WPC-089 CPU, this one from Twilight Zone, with battery holder removed.]]
The WPC CPU was the cornerstone of the new WPC pinball system, introduced by Williams in 1990.

The board has the following features:
* Motorola 68B09E processor
* Switch matrix inputs
* 8k of CMOS battery-backed memory
* A single EPROM, sized from 128K (1 megabit, 27C128) to 1M (8 megabits, 27C080 / 27C801)
* Watchdog circuit and master reset
* Three digital I/O ports - general-purpose; display; auxiliary (labeled "display")
* WPC ASIC - an 84-pin PLCC that has decoding, watchdog, and real-time clock circuitry.

'''What Goes Wrong'''

'''Loose Chips''' - resets and strange behavior

The natural heating and cooling cycle, and vibration, in a pinball machines causes the socketed chips to slowly walk out of their sockets. This loosening can cause mysterious behavior and resets. Firmly pressing each socketed device - including the ASIC - and listening for a small click can solve many odd problems.

'''Battery Corrosion''' - rows of switches failing

When batteries reach old age, they always leak electrolyte. In WPC boards, this electrolyte drips onto the switch matrix circuits. There, it causes extensive corrosion. The corrosion will eat up traces under the green solder mask, creating a lumpy appearance. This corrosion is extremely destructive. It must be caught early, and gently washed with vinegar. Damaged components must be replaced, and damaged traces cleaned with a fiberglass brush and carefully tinned with a soldering iron. Battery corrosion can render a board unrepairable, or undesirable.

''' The Switch Matrix ''' - assorted switch problems

The WPC system, like many pinball machines, uses a switch matrix to read the switches. The matrix is 8 rows by 8 columns, and can read 64 switches with just 16 wires. Under the playfield, the wires snake between the lights, creating strings of rows and strings of columns. The lights are isolated with diodes.

The root cause of switch matrix problems on the WPC CPU is often a voltage short to the switch matrix. This can happen with residual charge from the solenoid or flasher supply, so the machine does not have to be on for damage to occur. One easy way to do this is to touch a coil lug while adjusting slingshot switches. The row detectors - the LM339s - are quite safe from everything but the 70V solenoid voltage, and will often survive that. The column drivers, however, are directly exposed to the wiring. So many shorts - from the GI; lamp matrix; flashers; or solenoid wiring can destroy the driver. A solenoid wiring short will often destroy the 74LS374 at location U14 ahead of the driver as well.

The symptom of a bad driver is a column short that does not go away when the playfield is disconnected. A bad driver may also be confused by neighboring columns, so switches may register twice.
 

[[File:TheCapacitorToNowhere.jpg|200px|thumb|left|This "missing" bypass capactor isn't missing at all.]] 
The WPC CPU is stuffed with a "bypass capactor" to the right of the ULN2803. Bypass capacitors filter high frequency noise from the 5VDC power at each integrated circuit (generally). This one...in some revisions of the PCB, isn't connected to anything on one side. It can safely be removed, or more likely, simply not be replaced when abating alkaline corrosion.
 

===== Early WPC-089 MPU Board as found in Bride of Pin*Bot =====
[[File:EarlyWPC-089MPU-PinBot.jpg ‎|200px|thumb|left|WPC-089 CPU, this one from Bride of Pin*Bot, with battery holder removed.]]
[[File:PinBotMPUBoardRev.jpg ‎|200px|thumb|right|Board Revision.]]
[[File:PinBotDateStamp.jpg ‎|200px|thumb|right|Board Date Stamp. August 7, 1990]] 
The MPU board pictured here is from a Bride of Pin*Bot. Note that J210 and C31 have been replaced.

Some differences between this early board revision and later production revisions:
*Upper right corner parts are quite different
*Mounting holes vs key-holes
*Some sort of "hack" just to the left of the 68B09EP and game ROM.
*Different brand of bypass capacitors (B).
 

===== WPC-089 Signal Map (pinouts) =====
[[File:WPC89 CPU compnt-side ZAZ FEB2017-10.jpg|200px|thumb|left|Component Side.]][[File:WPC89 CPU solder-side ZAZ FEB2017.PNG|200px|thumb|right|Solder Side.]] 
The two diagrams (left and right) show the signal pinout for the entire WPC-089 MPU, both front and back side view. ''Images provided by Sascha Voskuil.''
 

===== WPC-089 Bare PCB Images =====
The following images are provided for reference.

<center>
<gallery widths=250px heights=200px perrow=4 caption="WPC-089 OEM MPU PCB Traces">
File:WPC-089-U1.JPG|<center>U1</center>
File:WPC-089-U2.JPG|<center>U2</center>
File:WPC-089-U3.JPG|<center>U3</center>
File:WPC-089-U4.JPG|<center>U4</center>
File:WPC-089-U5.JPG|<center>U5</center>
File:WPC-089-U6.JPG|<center>U6</center>
File:WPC-089-U7.JPG|<center>U7</center>
File:WPC-089-U8.JPG|<center>U8</center>
File:WPC-089-U9.jpg|<center>U9</center>
File:WPC-089-U11.JPG|<center>U11</center>
File:WPC-089-U12.JPG|<center>U12</center>
File:WPC-089-U13.JPG|<center>U13</center>
File:WPC-089-U14.JPG|<center>U14</center>
File:WPC-089-U15.JPG|<center>U15</center>
File:WPC-089-U16.JPG|<center>U16</center>
File:WPC-089-U17.JPG|<center>U17</center>
File:WPC-089-U18.JPG|<center>U18</center>
File:WPC-089-U19.JPG|<center>U19</center>
File:WPC-089-U20.JPG|<center>U20</center>
File:WPC-089-U21.JPG|<center>U21</center>
</gallery>
</center>

====WPC-S CPU====
[[File:WPC-SCPU.jpg|300px|thumb|left|WPC-S CPU]]
[[File:WPC-SMPU.jpg|400px|thumb|right|WPC-S CPU with daughter card installed. Battery holder replaced with coin cell battery.]]
The WPC-S CPU is the second generation of WPC CPU board. The designer switched to a remote battery holder, located on a daughter board that clips to posts on the lower half of the board. This approach mostly eliminated the PCB damage caused by battery leakage. The next version of the board, the WPC-95 CPU board, switched to a plastic battery holder that doesn't provide quite as much alkaline corrosion protection to the board.
The board also has different switch matrix connectors than WPC and WPC-95.

The digital I/O connectors remain unchanged from the WPC CPU.

The most significant difference was the introduction of the security PIC. This devices contains a serial number and a handshake mechanism. The serial number is displayed at startup, and allowed the manufacturer to identify the dealer who sold a machine into a particular region. This approach was necessary when substantial price differences were common across Europe, to prevent grey imports.

To prevent simple removal of the PIC, the device also controlled the switch matrix, and would not operate without a correct machine code from the WPC CPU. Therefore, there is one PIC for each machine. An incorrect or defective chip will result in a "G13 error" or "U22 error" at startup.

When buying a used WPC-S MPU, the battery holder is often missing. If connecting a battery pack, a Molex housing and 2 crimp contacts is needed. The part number for the 5 pin housing is 50-57-9405 (Digikey WM2903-ND). The crimp contacts are part number 16-02-1125 (WM2554-ND).
 

====WPC-95 CPU====
[[File:Wpc95-cpu-rev1-MrVT.jpg|300px|thumb|left|WPC-95 CPU Board, part number A-20119. Note that U27 is a 74LS08 in this revision. Image courtesy of PinSider "DumbAss".]]
[[File:Wpc95-cpu-rev3-MrVT-Cropped.jpg|300px|thumb|right|WPC-95 CPU Board, part number A-21377. Note that U27 is a 74LS02 in this revision. Image courtesy of PinSider "DumbAss".]] 
The WPC-95 CPU is the third generation of the WPC CPU design. It includes the security PIC added in the WPC-S system, and returns to an on-board battery holder. The new battery holder has a large plastic shell, designed to shield the PCB from any battery leakage. The pinout of the switch matrix connectors changed again from WPC-S.

Note that these pictures show MPUs with the battery holders removed and with the dual .100 headers replaced with "box" headers.
 

===== WPC-95 CPU Factory Modification =====
[[File:WPC95FactoryMod.png|300px|thumb|left|WPC-95 CPU Board factory mod. Drawing by Sascha Voskuil.]] 
CPUs manufactured for Jack*Bot and Congo sample games before 12-15-95 have a factory modification that includes one cut, an additional diode, and an additional resistor. Williams [http://www.planetarypinball.com/mm5/Williams/tech/sb86.html Service Bulletin 86] details the reason for the mod, premature loss of backup battery voltage.
 

===== The WPC ASIC =====
[[File:WMS-ASICVersions.jpg|300px|thumb|left|An original ASIC (left) and a reproduction ASIC (right).]] 
The ASIC (application specific integrated circuit) lies at the heart of all WPC systems. The same ASIC was used across WPC, WPC-S, and WPC-95.

The ASIC combines much of the digital logic required by prior WMS System 3-11 game systems into a single chip. This workhorse chip rarely fails. The correct tool must be used to remove the ASIC as both the chip and the chip carrier can be damaged by using the incorrect tools.

The -01 version shown at left was reproduced by Mr. Pinball Australia in 1997.
 

===WPC Power/Driver Board Generations===
====WPC-89 Power/Driver Board====
The WPC power-driver board converts AC power from the transformer; drives the solenoids; drives the lamp matrix; drives the GI lamps; and detects flipper switch operation in non-FlipTronics machines.

There are three known variants of the WPC-89 driver board: A-12697-1, A-12697-3, and A-12697-4. The A-12697-1 (aka "-1") board is forward-compatible with all WPC-89 & WPC-S games. Because later board versions A-12697-3 ("-3") and A-12697-4 ("-4") boards had components removed due to the introduction of the fliptronics boards, they are not backwards compatible with non-fliptronics games (unless retrofitted with the missing components for older flipper operation).

The power-driver board includes the following functions:
[[File:WPC089 power summary.png|240px|thumb|left|Summary schematic of WPC '89 Power Driver board showing test LED's and test points. A PDF of this image can be viewed [[Media:WPC089 power summary.pdf|here]]]]
[[File:WPC_Power_-Driver_Board.jpg|200px|thumb|right|WPC Power-Driver board with Flipper Relay, or the -1 version.]]
[[File:WPCPowerDriverBoardWithoutFlipperRelay.jpg|200px|thumb|right|WPC Power-Driver board without Flipper Relay, or the -3 version.]] 

*AC rectification and smoothing for 70VDC solenoid voltage
*AC rectification and smoothing for 20VDC flasher voltage
*AC rectification and smoothing for 18VDC lamp matrix voltage
*AC rectification and smoothing for unregulated 12V supply
*AC rectification and smoothing for 5VDC flasher voltage
*Regulated 12V supply
*Regulated 5V supply
*6.3VAC supply for GI circuits
*Power control for high power solenoids (drives 1 - 8, Q64 through Q82), with clamping diode connected to 50VDC
*Power control for low power solenoids (drives 9 - 16, Q44 through Q58, with clamping diode connected to 50VDC
*Power control for flashers (drives 17 - 20, Q36 through Q42), without a clamping diode at all
*Power control for "special" solenoids (drives 21 - 28, Q20 through Q34), with clamping diode that must be connected to the power source driving the device. In practice, this is always the 50VDC power source.
*Power control for lamp matrix
*Power control for pre-FlipTronics flippers (not on all boards)
*Sense optos for pre-FlipTronics flippers (not on all boards)
*Power control for 5 6.3VAC GI channels using four-sector triacs
*Zero crossing sense for AC line in
*Logic interface to WPC CPU
 

=====Retrofit a later driver board to become a -1 version board=====
[[File:Dash-1Conversion.jpg|300px|thumb|right|A -3 WPC Power/Driver board retrofitted with the minimum parts required to add -1 functionality. Note: R210 and R211 still need to be populated on this board.]] 
The newer generation -3 and -4 boards can be converted to -1 board configuration by populating the following components:
*D39 - 1N4004
*U7/U8 - 4N25 (or 4N35)
*R210/R211 - 3.3K/5W Resistor
*RLY1 - 6VDC 4PDT Relay
*J110 - 9-pin .156 header
*Q99 - 2N5401 transistor
*R208 - 270 ohm 1/4W resistor
*R209 - 4.7K ohm 1/4W resistor

In the image at right, some components remain unpopulated. Those components are part of the line level voltage circuitry that drives LED2 and LED3. The line level voltage circuitry does not work very well and can not be relied upon. Hence, there is no reason to populate those components. 

[[File:WPCPowerDriver-1-3Differences.jpg|300px|thumb|left|A graphical indication of part differences between the -1 and -3 WPC Power/Driver board configurations. Illustration provided with permission of Sascha Voskuil aka Zaza.]] 
The diagram at left depicts the differences between the -1 and -3 WPC Power/Driver board configurations.
 

=====WPC Power/Driver Board Layout Errors=====
======C9 Connection Error======
[[File:WPCPowerDriverBoardC9Correction.jpg|300px|thumb|left|WPC Power/Driver board with C9 connection corrected.]]
[[File:WPCPowerDriverBoardC9CorrectionSchematic.jpg|300px|thumb|right|Image of WPC Power/Driver board schematic, showing LM323K 5VDC regulator and C9.]] 
At the time that this PCB was laid out and manufactured, a small tantalum capacitor, located at C9, was connected to the wrong side of the LM323K 5VDC regulator. While it should have been connected to Vin, it was in fact connected to Vout. The picture at left shows a method to correct the board so that it matches the schematics, also shown at left. In this picture, an additional "tab" was added to the top bolt of the regulator and soldered to ground, creating a redundant path to ground for the regulator.

Note that while the schematics show this capacitor as .33µF, it is listed as 2.2µF in each game's parts listing, matching the capacitor that is actually installed.

This change isn't generally considered necessary and not thought to be a significant contributor to game resets. The original purpose of the cap was to filter high frequency noise. According to the LM323K datasheet, a 1 to 2µF tantalum capacitor should be added to the input of the LM323K if the regulator is more than 4" away from the main filter capacitor. The regulator is just inside of 4" from the 15,000µF filter capacitor at C5. As it sits on Vout, it causes no harm, but does no good either.
 

======J122/J124, pin 1 Connected to Board Ground======
[[File:WPCPowerDriverBoardLayoutError.jpg|300px|thumb|left|Two power/driver boards showing the factory corrected trace routing (bottom) and a later version of the board with the correction incorporated into the PCB mask (top).]] 
Some revisions of the WPC power/driver board, were manufactured with J122 and J124, pin 1, connected to board ground. This would cause whatever is connected to those connector positions, to be turned on constantly. For the game Twilight Zone, this would result in the left mini-playfield magnet being powered constantly. The picture at left shows a factory modification to the power/driver board to rectify the problem.
 

====WPC-95 Power/Driver Board====

The WPC-95 Power/Driver board performs all of the same functions as it's WPC predecessor, and also integrates flipper power circuits into the design, eliminating the need for the FlipTronics board present in WPC FlipTronics I & II games as well as WPC-S games. The bridge rectifiers are replaced by ganged 6A2 diodes and the filter capacitors were spec'd down from 15,000µF to 10,000µF. While the WPC P/D board supported brightness control of 5 general illumination circuits, the WPC-95 P/D board can control brightness of only 3 general illumination circuits. The two remaining GI circuits are used for backbox illumination.
[[File:WPC095 power summary.png|300px|thumb|left|Summary schematic of WPC '95 Power Driver board showing test LED's and test points. A PDF of this image can be viewed [[Media:WPC095 power summary.pdf|here]]]]
[[File:WPC-95PowerDriverBoard.jpg|300px|thumb|right|WPC-95 Power/Driver board. This is the later model, with zero ohm jumpers installed in the GI circuit, lower left.]]
 

===WPC Alphanumeric Display Driver Board===
The Alphanumeric display driver board was used in Funhouse, Harley Davidson, and The Machine: Bride of Pin*bot. The board still contains the high voltage handling ICs, UDN6118 and UDN7180. It also has its own high voltage generation circuit that is a carryover from earlier Williams high voltage display circuits.
[[Image:WPCAlphaNumericDisplayDriverFront.jpg ‎|300px|thumb|left|WPC Alphanumeric Display]]
[[Image:WPCAlphaNumericDisplayDriverRear.jpg ‎|300px|thumb|left|WMS A-12739-1 WPC Alphanumeric Display Driver PCB]]
 

===WPC Dot Matrix Controller board===

[[Image:WPC DMD Controller.jpg|300px|thumb|left|WPC DMD Controller board]]
The WPC DMD display and DMD controllers are common features in Williams 1990's era pinball machines. The display is a high-voltage plasma system that has scanning electronics built in. The WPC dot matrix controller board, or WPC-95 AV (Audio/Video) board in later machines, provides the power for operation, and maintains the display dot images in its memory. The CPU loads these pages ahead of time, then instructs the display controller to "flip" the images onto the screen.

Note that sometimes U12 is stuffed on this board and sometimes it is not. There is no functional difference whether U12 is stuffed or not.

Clive at the Coin-Op Cauldron has written an excellent article detailing some of the nitty gritty of the DMD controller. The article can be found [http://coinopcauldron.com/dotarticle.html here]. 

===WPC Sound Boards===
====WPC pre-DCS Sound Board====
[[Image:WPC Sound Board.jpg|300px|thumb|left|WPC pre-DCS Sound Board, sound ROMs removed]]
Pre-DCS Sound Board issues are discussed [https://www.pinwiki.com/wiki/index.php/Williams_WPC#Pre-DCS_Sound_Board_Issues here]. 
The pre-DCS sound board uses a single LM1875 amp and can accommodate up to 3 sound ROMs. With a single "sound lane" and amp, stereo sound is not possible. The three speakers are connected in series, each of them attempting to accentuate different bands of the audio spectrum. A broken wire to any of the three speakers will result in no sound at all.
 

====WPC DCS Sound Board====

[[File:WPC DCS Sound Board.jpg|300px|thumb|left|The WPC DCS Sound Board]]
DCS Sound Board issues are discussed [https://www.pinwiki.com/wiki/index.php/Williams_WPC#DCS_Sound_Board_Issues here]. 
With Indiana Jones: The Pinball Adventure, Williams introduced the DCS sound system. Its DSP architecture was a significant improvement on earlier systems, and it allowed Williams to use recorded music from EPROM rather than synthesizer music. The board also introduced dual amplifiers and an electronic crossover. DCS allowed Williams to use compressed sound samples, significantly improving the sound quality of the games.

The board dropped the microprocessor controlled synthesizer chip and sound bite system of earlier WPC machines, and replaced them with the still in production Analog Devices ADSP-2105 DSP. For its time, this was an extremely fast device (40MHz), and is capable of providing all of the sound processing needed in a WPC pinball machine. The ADSP-2115 can also be used as a replacement for the 2105. It adds a second serial port which is not used in WMS pinballs. Williams also upgraded the chip amp. The new chip amp operates at a lower voltage, and forced a corresponding change in the transformer voltage (12VAC + 12VAC). Therefore, DCS machines have different transformer winding to previous WPC machines. The system has an electronic crossover, separating high frequencies to the backbox and low frequencies to the cabinet.

The card connects to the WPC CPU through the I/O port. It shares the port with the Fliptronics board and the display board.
 

'''What's on the Board?'''

The DCS sound board has the following subsystems:

* Rectifier and fused power supply for +/-16VDC amplifier power [check - WPC was 35V?]
* Dual-channel power amplifier with electronic crossover
* DSP-based sound synthesizer
* One EPROM for DSP code storage
* Other EPROMS for sound storage
* High-speed program memory for the DSP
* Mailbox interface for WPC-CPU

On power-up, the board runs a diagnostic and sounds a bong. It does this without any help from the WPC CPU. If there is no bong, the board has a problem.

'''What Goes Wrong'''

The smoothing capacitors C20 and C21 are often at the end of their useful lives. The chip amp, like the Honey Badger, really doesn't care, and will accomodate capacitor variance. However, replacing them will make even the pre-DCS sound much richer.

The coupling capacitors at C32 and C41 can fail.
 

====WPC-95 AV Board====
[[File:Wpc95AV.jpg|300px|thumb|right|WPC-95 AV Board]]
WPC-95 AV Board issues are discussed [https://www.pinwiki.com/wiki/index.php/Williams_WPC#WPC-95_A/V_Board_Sound_Issues here]. 
The WPC-95 AV board integrated the sound and video system into a single board, siginifcantly reducing power and space.

The board has the following major subsystems

'''ASIC'''
The ASIC is a 120-pin quad flatpack device. It incorporates the following functions:
*Interface registers to CPU
*Memory control and display output logic for the diaplay subsystem
*Memory interface for the AD2105 DSP

The ASIC has a tendency to fail in such a way that the sound disappears. New ASICs are available, but replacing them requires skill with surface mount devices.

'''Audio DSP'''
The audio susbsystem uses the same part as the DCS sound board the Analog Devices DSP part ADSP-2105 and an AD1851 DAC. For its time, this was an extremely fast device (40MHz), and is capable of providing all of the sound processing needed in a WPC pinball machine. The AD1851N in DIP package was discontinued 2010 but the DSP is still available at Digikey and many other stores (ADSP-2105BPZ-80 ).

Location: lower center of board

'''Serial Port'''
The serial port is rarely populated. Its uses include: machine debugging; machine linking ([[NBA Fastbreak]]); ticket printers

Location: lower left of board

[[File:AVBoardFront.jpg|300px|thumb|left|WPC-95 AV Board Trace Reference (front)]]
[[File:AVBoardBack.jpg|300px|thumb|right|WPC-95 AV Board Trace Reference (back)]]
'''Audio Amplifier'''
The audio amplifier is a dual-channel TDA 2030A operating at X volts. The system has an electronic crossover, separating high frequencies to the backboox and low frequencies to the cabinet.

Location: lower right of board

'''DMD Power'''
The DMD nominally requires 62, -100 and -112VDC to operate. The board uses a temperature-compensated design to supply these voltages.The -112VDC line is built as a 12V offset from the -100VDC line.

Location: upper right of board.
 

===WPC FlipTronics I & II Boards===
Beginning with The Addams Family, Williams implemented the FlipTronics flipper power and switch sensing system. The Addams Family and The Addams Family Gold were the only two games which used the FlipTronics I board. Subsequent games until the WPC-95 board set debuted used the FlipTronics II board. The three FlipTronics II board revisions (A-15472, A-15072-1, and A-15472-1) are interchangeable. The WPC-95 board set integrated the flipper electronics into the driver board.

[[File:WPC_Fliptronics_I_Board.JPG|300px|thumb|left|WPC Fliptronics I Board]]
[[File:WPC Fliptronics II.jpg|300px|thumb|right|WPC Fliptronics II Board]] 
Prior to the FlipTronics system, flipper circuit design had essentially been the same simple circuit. This circuit consisted of power to two flipper coil windings (the "power stroke" and "hold" windings). When the flipper cabinet switch was closed, the power winding and hold winding were both energized. As the flipper plunger was pulled in, the flipper EOS switch opened, interrupting power to the "power stroke" winding, leaving only the "hold winding" energized to hold the flipper in the up position. Flipper coil systems were designed this way so a flipper could be energized indefinitely (in theory). A failed EOS switch could result in weak flipper performance (poor EOS switch conduction) or result in burned flipper coils (EOS switch that never opens). 

[[File:FlipTronicsLayout.png|300px|thumb|left|FlipTronics II Component Identification. Image courtesy of PinSider j_m_.]] 

The FlipTronics system ended reliance on properly operating EOS switches. While FlipTronics systems still have EOS switches, they generally are not used to control power to the coil windings. The EOS switch provides feedback to the MPU that the flipper has completed a stroke. A failed EOS switch will not cause damage to either the coil or to the switch circuitry. If the MPU doesn't receive feedback that the flipper has completed a full stroke within a specific time (milliseconds), the "power stroke" winding power will still be interrupted.

There is a special case where a properly operating EOS switch comes into play. The EOS switch on FlipTronics games helps to keep the flipper bat in the up position when a fast moving pinball strikes the flipper. When the ball strikes the flipper, moving it toward the "at rest" position, a properly operating EOS switch will open. The FlipTronics board will then provide a path to ground for the "power stroke" winding until the flipper completes the upward stroke, closing the EOS switch again. Games with broken or malfunctioning EOS switch(es) may allow the flipper bat to drop all the way to the "at rest" position when struck by a rapidly moving ball, with possible loss of ball, and a great deal of "what the @#$% just happened".
 

'''FlipTronics game flipper operation: '''
#Flipper power is always present at the flipper coil lugs. For the flipper to actuate, that coil power needs to find a path to ground.
#The FlipTronics board switch sensing circuitry recognizes closure of a flipper cabinet switch.
#The FlipTronics board communicates closure of the flipper cabinet switch to the MPU.
#The MPU commands the FlipTronics board to provide ground for the "power stroke" winding of the flipper coil (via a circuit passing through a 2N5401, TIP-102, and TIP-36C). This process is similar to how high powered coils are controlled by the power driver board.
#A few milli-seconds later (thousandths of a second), the MPU commands the FlipTronics board to interrupt the ground path for the power stroke winding and to provide ground for the hold winding portion of the coil (via a circuit passing through a 2N5401 and a TIP-102).
#The FlipTronics board switch sensing circuitry recognizes close of the flipper EOS switch, and communicates that switch closure to the MPU. Again, this switch closure isn't used to control power to the flipper coil windings. It's merely information.
#When the player releases the cabinet flipper switch, the FlipTronics board again senses that open switch, communicates the change in state to the MPU which then commands the FlipTronics board to interrupt ground to the hold winding also, and the flipper returns to it's at rest position.

WPC-95 games use the exact same methods. However, the WPC-95 board set integrates the capabilities of the FlipTronics board into the power driver board.

The FlipTronics II board also rectifies AC voltage sourced from the game transformer, and relayed to it from the Power/Driver board to create the 70VDC flipper power (the FlipTronics I board relies an an "extra flipper power supply" to rectify the flipper voltage). A FlipTronics board can sense 8 switches, and control up to four flipper power and hold windings. In some games, spare flipper cabinet switches, EOS switches, and coil drive circuits are used for other game features.

Note that sometimes C2 is installed on this board and sometimes it is not. The board pictured does not have C2 installed. Since C2 is a 100µF/100V capacitor, it can't be doing too much AC smoothing of the full wave rectified flipper power. Some RGP discussions indicate that C2 may have been designed in originally to reduce EMI (electro-magnetic interference) from the board. Installing C2 will have a negligible affect on flipper power. Some report that installing C2 fixes a "jittery gate" symptom on BSD's "mist" assembly.

More information about bench testing FlipTronics board is available [[Leon_Borre_WPC_Fliptronics_board_repair | here]].
 

======Fliptronics II in The Addams Family======

The Addams Family was designed to use the Fliptronics 1 board system. This consists of a Fliptronics 1 board and a separate external power supply. This external power supply is connected to the upper flippers and the three magnets under the playfield. The lower flippers are connected to the 50V DC power supply in the Power Driver Board.

While the Williams Fliptronics II board could physically be installed in The Addams Family and is plug compatible, it is not advisable to do so. The power supply in the Fliptronics II board will not be connected (without running extra wiring). And the Fliptronics II board does not have the 4-wire ground connector (J801 on the Fliptronics I board). The only ground connection is via 2 wires on J904 (J804 on the Fliptronics I board) and that is intended as the digital ground for +5 and +12.

The only way to properly use the Williams Fliptronics II board in The Addams Family is to run new wiring from the +50V AC Power Driver Board supply to J901 and connect the power supply for the flippers to J907. Or run proper ground wires between the Williams Fliptronics II board to the flipper power supply board.

Most aftermarket Fliptronics board have the ground connector at J801 and can be used in The Addams Family without modifications. However, those aftermarket boards will act like Fliptronics 1 boards and will require the flipper power supply to remain in the game.

===Miscellaneous WPC Boards===

====WPC 7 Opto Board (A-14977, A-15576, A-15595)====

The 7 Opto Board is used in the following games:
*Attack from Mars
*Cirqus Voltaire
*Demolition Man
*Flintstones
*Jackbot
*Judge Dredd
*Johnny Mnemonic
*NBA Fastbreak
*Road Show
*The Addams Family
*The Addams Family Gold
*Theatre of Magic
*Tales of the Arabian Nights
*World Cup Soccer
*White Water
[[File:7OptoBoard.jpg|300px|thumb|left|Example WPC 7 Opto Board, as found in AFM and many other WPC games.]]
[[File:A-155767-OptoBoard.jpg|300px|thumb|right|7 Opto Board Schematics.]]
The connector on the lower left (as pictured) provides the power for seven IR emitters. The emitters are powered from the 12V supply through a 260 ohm resistor (the large blue resistors adjacent to the connector). Williams runs the opto emitters at about 40mA, which results in the resistors becoming hot. The opto boards are often darkened by the heat, as this one is.

The connector on the upper left carries the signals for the photo-transistors. The photo-transistor collector connects to 12V, and its emitter connects to ground through two 2KOhm resistors connected in series. When the transistor is illuminated by the emitter, it passes more current through the resistors, raising the input voltage on the LM339. The other pin on the LM339 is set to about 2.8V buy a 100K/22K voltage divider. Therefore, when the voltage at the junction of the two 2K resistors and the LM339 input is above 2.8V, the switch will read as closed. This happens at 1.4mA.

The two left side connectors can be used for optical trough switches. The connector on the right hand side provides the the row/column switch matrix interface to the MPU. 

=====WPC 7 Opto Board Problems=====
'''What Goes Wrong?'''

The resistor discoloration is cosmetic, and rarely causes problems. The biggest problem for these boards is switch matrix shorts. If any of the power lines hits the switch matrix, it can easily destroy the LM339 and possibly its output diode. This issue will manifest as a ground short on one or more rows. It can be tested by removing the switch matrix connector. If the problem goes away, the associated LM339 and possibly its diode need to be replaced.

If the short was from the 70V supply, multiple LM339s may be damaged.

Replacing LM339s on these boards needs to be done carefully, as it is easy to lift traces and pull the through-hole plating. Always socket replaced ICs.

====WPC 10 Opto Board (A-15430, A-18159, A-20246) ====
[[File:WMS 10 Opto.jpg|300px|thumb|left|Example WPC 10 Opto Board.]]
[[File:A15430-10OptoBoard.jpg|300px|thumb|right|Example WPC 10 Opto Board schematics]] 
The 10 opto board was used in Bram Stoker's Dracula, Dr. Who, Indiana Jones, Pinball Circus, Popeye, Cactus Canyon, Corvette, Monster Bash, Medieval Madness, Revenge From Mars, SafeCracker, SWE1, Shadow, Congo, Indianapolis 500, and World Cup Soccer.

The connector on the upper left carries the power for seven of the IR emitters. The emitters are powered from the +12V supply through a 260 ohm resistor (the large blue resistors adjacent to the connector). Williams runs the opto emitters at about 40mA, which results in the resistors becoming hot. The opto boards are often darkened by the heat, as can be viewed in the adjacent picture.

The connector on the lower left carries the signals for the photo-transistors. The photo-transistor collector connects to +12V, and its emitter connects to ground through two 2KOhm resistors connected in series. When the transistor is illuminated by the emitter, it passes more current through the resistors, raising the input voltage on the LM339. The other pin on the LM339 is set to about 2.8V by a 100K/22K voltage divider. Therefore, when the voltage at the junction of the two 2K resistors and the LM339 input is above 2.8V, the switch will read as closed. This happens at 1.4mA.

These two connectors can be used for optical switch troughs. The three connectors on the right hand side each carry signals for one transmitter/receiver pair. These connections are often used for ramp entrances, and sometimes the pair is mounted on a single bracket.

The connector on the bottom provides the the row/column switch matrix interface to the MPU. 

=====WPC 10 Opto Board Problems=====
'''What Goes Wrong?'''
[[File:10OptoBoardCorrosion.jpg|300px|thumb|right|The leaky capacitor removed and shown in this picture, spewed enough electrolyte to completely eat through the power trace, causing the board fail.]]‎
The resistor discoloration is cosmetic, and rarely causes problems. The biggest problem for these boards is switch matrix shorts. If any of the power lines hits the switch matrix, it can easily destroy the LM339 and possibly its output diode. This issue will manifest as a ground short on one or more rows. It can be tested by removing the switch matrix connector. If the problem goes away, the associated LM339 and possibly its diode need to be replaced.

If the short was from the 70V supply, multiple LM339s may be damaged.

Other symptoms of failed LM339's can include:
* Intermittent ground shorts on one or more switch matrix rows. Sometimes this can be mistaken for a connector issue since the ground short warning message and row(s) of closed switches in the edge switch test may appear and disappear at random.
* Sometimes the switch edge test can show one or multiple opto switches flickering open and closed. This can sometimes be mistaken for a connector or individual opto issue, as it can come and go at random.
* In switch edge test, one opto switch can activate an entire row of opto switches, but might not actually show the ground short warning.

Replacing LM339s on these boards needs to be done carefully, as it is easy to lift traces and pull the through-hole plating. Always socket replaced ICs.

Another common issue is the 100uf/35V electrolytic capacitor at C1 will leak corrosive liquid that eats through the traces under it. This interrupts the power supply.

====WPC Twilight Zone Custom 10-Opto Board (A-16807)====
[[File:TZ10OptoBoard.jpg|300px|thumb|left|Twilight Zone specific 10 Opto Board.]]
[[File:10OptoBoardTZ.jpg|300px|thumb|right|Twilight Zone specific 10 Opto Board schematics]] 
This 10-Opto board appeared only in Twilight Zone. As can be seen, it differs in pinout (at the very least) from the more ubiquitous 10-Opto board above.

'''What Goes Wrong?'''

See "[http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#WPC_10_Opto_Board_.28A-15430.2C_A-18159.2C_A-20246.29 WPC 10 Opto Board (A-15430, A-18159, A-20246)]", above.
 

====WPC 16 Opto Board (A-16998, A-17223)====
[[File:16OptoBoard.jpg|300px|thumb|left|WPC 16 opto boards, both versions]]
[[File:16OptoBoardSchematics.jpg|300px|thumb|right|WPC 16 opto board schematics]] 
This board is used in at least Star Trek: The Next Generation, Junkyard, and Champions Pub. Note the two different "versions". The bracket on one side is believed to be part number 5768-13739-00 while the bracket on the other side is believed to be part number 5768-13739-01. The boards are identical in layout and components. The only difference is bracket mounting, some silk screening, and one version has holes in the PCB which are not used.
 

====WPC Twilight Zone Clock Boards (A-16219, A-16220)====
[[File:TZClockBoardMinute.jpg |300px|thumb|left|A-16220 Twilight Zone specific Clock Mechanism "Minute Hand" Side of paired Boards.]]
[[File:TZClockBoardHour.jpg ‎|300px|thumb|right|A-16219 Twilight Zone specific Clock Mechanism "Hour Hand" Side of paired Boards]] 
The Twilight Zone playfield clock toy employs an ingenious method of driving and detecting the minute and hour hand positions. Two boards are sandwiched together, one with four optos to detect the minute hand and one with four optos to detect the motor rotation position and therefore the hour hand.

This board has been problematic over the years as the original incandescent lamps burned very hot, increasing the temperature inside the clock casing enough to damage the circuit board components. Numerous aftermarket clock boards have been offered with varying degrees of success.
 

[[File:TZClockBoardLampSchematic.jpg ‎|300px|thumb|left|Twilight Zone Clock Lamp Schematic Snippet]] 
Note that the schematic contained in the manual for the clock board lamps shows four diodes (D1-D4). During production, those diodes were swapped with "zero ohm jumpers". The reason for this change was that Williams originally intended the four lamps to be part of the lamp matrix and therefore individually controllable and also therefore requiring an associated lamp matrix isolation diode. When Williams decided to drive these four lamps via general illumination power, those diodes were replaced with "zero ohm jumpers" since diodes would have reduced lamp intensity and the lamps no longer required isolation in a lamp matrix.
 

====8 High Power PCB Assembly (A-16116)====
[[Image:A16116-8-HighPowerPCBAssembly.jpg|300px|thumb|left|A 8 High Power PCB Driver Board as used in ''Twilight Zone'']] 
The 8 High Power PCB was used only on Twilight Zone. It has the capacity to drive 8 high power coils if fully populated. Instead, it drives 5 high power coils as populated for Twilight Zone. This simple board is merely an extension of the power/driver board solenoid drive circuitry designed to accommodate the extra coils incorporated into the Twilight Zone design. It replicates the power/driver board circuitry of the TIP-36c transistors.
 

====Auxiliary 8-Driver Board (A-16100)====
[[Image:8 driver board.JPG|300px|thumb|left|An example 8-Driver board]]
[[Image:A-16100-8DriverBoard.jpg|300px|thumb|right|A-16100 Schematics]] 
The auxiliary 8-driver board sits in the top right of the backbox in a handful of WPC machines. The board is designed to run flashers, low-power solenoids, and perhaps motors.

The connector labeling is tricky as the 8-Driver board is controlled by a ribbon cable that is connected to the "Display" connector on the WPC CPU board (J204). The "Display" label is a historical artifact and refers to the alphanumeric display used in Funhouse. 

The board has 8 outputs, driven by TIP-102 transistors with a 2N4403 pre-driver, similar to the WPC power/driver board (which uses a 2N5401 as a pre-driver). The board is used in the following games:
*Demolition Man
*Indiana Jones
*Road Show
*Star Trek: The Next Generation
*Twilight Zone

The board circuitry can be jumpered to add one or two more columns to the switch matrix. This makes the board more flexible but also may require different jumpers to use the board in different games (i.e. the boards are not completely interchangeable between games "as is").

Jumpers to be installed for Demolition Man and Roadshow should be...
*PW1, PW3, PW5

Jumpers to be installed for Twilight Zone, Star Trek: The Next Generation, and Indiana Jones should be...
*SW2, SW4, SW6

Indiana Jones, Star Trek: The Next Generation and Twilight Zone use Q12 via the J5-1 connection to add this column. Although Twilight Zone adds the column, the column isn't displayed during switch test (T.1). The column is used to read the 8 optos in the clock mechanism.

The board can be jumpered to respond to memory mapped I/O at addresses 3FEB, 3FED, 3FED, 3FEE, and 3FEF via jumpers W1 through W5. In practice, this feature is never utilized as jumper W4 (3FEB) is always in and jumpers W1, W2, W3, and W5 are always out.

=====Auxiliary 8-Driver Board Problems=====
What Goes Wrong? 
This is a pretty simple board. Generally, the problem is going to be a blown transistor, or rarely, a failed 74ALS576 latch.

A problem which may occur are locked-on coils or flashers. This can be caused by the ribbon cable not being firmly seated. This can happen during the game or in attract mode and is caused by floating data line signals to the 8 Driver Board. A remedy has been found to solve this problem. This involves soldering a 10K resistor from the CLK to 5V and a resistor array 8x10K to pull down all data lines to GND. More information about this modification can be found under the [[Star_Trek:_The_Next_Generation#Diode_.22Tie_Back.22_missing_causes_8-Driver_Board_transistor_to_fail|"Diode Tie Back Missing Causes 8-Driver Board Transistor to Fail" section on the Star Trek: The Next Generation page]]

[[Image:STTNGDiodeTieBackAtCoilPower.jpg|300px|thumb|left|Diode tie-back at the single drop target assembly. Note the small purple/green wire soldered to the target reset coil's power side (two larger gauge purple/green wires).]] 
Another thing to watch for is a "diode tieback" connection to the board for games like Star Trek: The Next Generation. Without this "diode tieback", transistors on the 8-Driver board WILL be damaged. The diode tie-back wire is purple/green and connects from the coil power side of one of the drop target assembly coil lugs to J4 pin 1 on the 8-Driver board. If the solder connection at the coil lug is solid, suspect the wire connection at the IDC connector. Repinning this connection with good a quality crimp-on TriFurcon pin is advised.
 

====Sound Overlay Board (A-13502)====
This board acted as a power supply for a small subset of Funhouse and Dr. Dude games during the transition from System 11 to WPC in cases where the WPC boardset still included the [[Williams_System_9_-_11#Sound_Boards|System 11 D-11581 sound board]].
[[File:Placeholder.jpg|300px|thumb|left|Sound Overlay Board (A-13502)]] 

====Attack from Mars "Strobe" Board (A-20669)====
[[Image:AFMStrobeBoard.jpg|300px|thumb|left|A-20669 Attack From Mars Strobe Board]] 
The strobe board at left is unique to Attack from Mars. Williams used underrated 100µF/100V non-polarized caps on the board that often fail with the telltale "bulge" at one end. The "transformer" on the board (blue rectangular box, lower/right in the picture) has very fine legs which can break due to vibration at the back of the playfield.

Excellent repair information for this board can be found [http://www.iobium.com/fixing_the_afm_strobe_board.htm here] and a possible replacement for the overloaded non-polarized capacitors [http://kcpins.com/archives/63 here].

Note: An annotated .pdf of the schematics can be found [https://www.pinwiki.com/wiki/images/8/8f/STROBE.pdf here].
 

====Trough Opto Boards====
When WIlliams moved to the gravity trough, they also switched to optical switches to detect the ball. The trough is covered by a Williams patent.

There are two generations.

[[File:WMS A-17982 WPC Trough Transmitter.JPG|thumb|300px|left|WMS A-17982 Trough Transmitter Board - First Generation]] 
[[File:WMS A-17981 WPC Trough Receiver.JPG|thumb|300px|left|WMS A-17981 Trough Receiver Board - First Generation]] 
The first generation (Judge Dredd - Indiana Jones ???) used a receiver board with all of the switch logic on the board. The vibration in the trough makes extra components subject to failure. The second generation (xxx -) uses a regular opto board, and the trough receiver just has phototransistors.

As with all Williams opto circuits, the transmitters are driven to the very limit, and the series resistors overheat. This overheating destroys the solder joints.

Also, the continued vibration makes the resistor legs crack, and weakens the pins in the IDC connectors.

Later versions used rubber grommets to isolate the boards from the trough. 

=====Trough Problems=====
'''What Goes Wrong?'''

======Broken Parts Leads======

[[File:WMS WPC Trough Transmitter Reworked.JPG|thumb|left|300px|Typical Trough Opto Transmitter Boards after resistors have been replaced or soldered multiple times]]

The resistors on the emitter board are subject to cracked legs. Wiggle them to see if they are good. replace the resistor if there are any signs of trouble. On earlier receiver boards, inspect all components.
 

======Trough Divots======
[[File:WMS_WPC_Gravity_Trough_Dimpled.JPG|thumb|300px|left|Typical Trough Divots Caused by Balls]]
Balls make great hammers and, over time, they will beat divots into the trough floor. Then, they will then rest in the divots and cause all kinds of ball count problems. The problem is exacerbated with slightly magnetized balls.

The fix is to file them out, and then sand the metal smooth. A dremel tool with grinding stone works great for this.

Installing a shim that slides over the divots is also a fix for this issue. There use to be both [https://www.pinballlife.com/williamsbally-trough-shimprotector.html metal versions (now PETG)] and [https://www.marcospecialties.com/pinball-parts/03-16809 PETG plastic versions] on the market. Only the PETG plastic versions are available now, as far as we know. The shim eliminates the ability of balls to rest in the divots as well as breaking any magnetic connection, especially with the PETG plastic version.
 

====WH2O Chaser Lamp Board (A-15761)====
[[File:A-15761ChaseLampBoard.jpg|300px|thumb|left|A-15761 Chase Light Board]]
[[File:A-15761Schematic.jpg|300px|thumb|right|A-15761 Chase Light Board Schematic]] 
This board is used for the chaser lamps on Whitewater. It is a simple lamp sequencing board that causes the lamps to "chase".

The board rectifies 16VAC via BR1 and BR2 to create approximately 12VDC to power the chase lamps. The board also receives 12VDC from the power/driver board and regulates it down to 5VDC via an LM7805. This 5VDC is used for the logic level ICs on the board.
 

====CFTBL Chase Light II Board (A-15541)====
[[File:5768-13221-02.jpg|300px|thumb|left|A-15541 Chase Light II Board]]
[[File:A-15541Schematic.jpg|300px|thumb|right|A-15541 Chase Light II Board Schematic]] 
This board is used for the chaser lamps located around the ramps and whirlpool bowl in Creature From the Black Lagoon. 

Eight BT138 triacs, which are pre-driven by 2N4403 transistors, control eight discrete lamp strings. In addition to the lamps chasing, the lamp strings can be dimmed for effect. 

====High Current Driver Board (C-13963)====
[[File:C-13963HighCurrentDriverBoard.jpg|300px|thumb|left|C-13963 High Current Driver board as used in NBAFB and Funhouse.]]
[[File:HighCurrentDriverBoard.jpg|300px|thumb|right|C-13963 High Current Driver board Schematic]]
This board drives the jaw motor for the playfield heckler Rudy in the game Funhouse.

The circuitry is identical to the "Corvette/Road Show Dual H-Drive Motor Control Board" in the next section except that this board controls a single motor only. 

==== Corvette/Road Show Dual H-Drive Motor Control Board (A-19159/A-19242-1)====
[[File:WMSMotorDriveBoard.jpg|300px|thumb|left|Dual H-Drive Motor Control Board as found in RoadShow (A-19159/A-19242-1)]]
[[File:A-19159DualHDriveMotorControllerSchematic.jpg|300px|thumb|right|Dual H-Drive Motor Control Board Schematic]]
The "Dual H-Driver Motor Control Board" is used on Corvette and on Road Show. For Corvette, it drives the two small motors that animate the two car race track on the right side of the playfield. For Road Show, it controls both Red and Ted's mouth motors.

While the board has two different part number designations, they are, in fact, identical.

Note: Parts enclosed by "Block A" and "Block B" in the schematics are not stuffed.
Parts near "Block C" and "Block D" in the schematics are stuffed with 5.6ohm resistors when used in RoadShow. Those resistors are not stuffed when used in Corvette. Instead, JP1 and JP2 are stuffed.

Operation 
The board is powered by either 12VDC (J118/2, Roadshow) or 20VDC (J107/6, Corvette) from the power/driver board. 
Each "channel" receives a direction and an enable signal. The signal is either grounded or floating. 
Four transistors on the power/driver board provide these signals (three transistors for Corvette as both motors always run in the same direction in game operation, either forward or reverse). 
Grounding the "enable" pin for a channel enables power to the associated motor. 
Grounding the "direction" pin (or leaving it floating) for a channel causes the motor to turn either clockwise or counterclockwise. 
Each channel can be controlled independently. Hence the name, Dual H-Drive.

=====Dual H-Drive Motor Control Board Problems=====
[[File:CorvetteDualHDrive.jpg ‎|300px|thumb|left|Dual H-Drive Motor Control Board as found in Corvette (A-19159/A-19242-1). Note the absence of 5.6ohm sand resistors]]
What Goes Wrong? 
Most failures are caused by the two 100uf/35V electrolytic capacitors on the board. They sometimes leak and destroy the power traces beneath them. After that, the TIP102/TIP-107 transistors can fail. These are easily tested using the "diode test". The LM339 is relatively beefy and rarely fails but of course, this is possible.

[[image:YT.png]] A YouTube video showing repair and test of a Dual H-Driver motor control board can be found [https://youtu.be/d7ODSyDlLrQ here].
 

====Bi-Directional Motor Board (A-15680)====
[[Image:A-15680BiDirectionalMotorBoardSchematic.jpg|300px|thumb|left|A-15680 Bi-directional Motor Board]]
[[Image:TraceCloseup-A15680.jpg|300px|thumb|right|Close up view of traces under A-15680 filter capacitor]] 

This board is used in Cirqus Voltaire, Dr Who, Party Zone and White Water.

One problematic aspect of the board's design is that the 100µF electrolytic cap is mounted over the trace that carries 12VDC power to the drive transistors. If the electrolytic cap fails and leaks it's corrosive contents, it will eat through the trace and the board won't work correctly. If this happens in WH2O, Big Foot will not turn his head during game test at boot up. The board pictured at left exhibited this problem and was repaired.

Note that this cap, C2, was sometimes not stuffed at the factory. It's purpose is to filter noise from the 12VDC power, but the power is clean enough that this cap isn't really necessary. Note also that the schematics for the board are in error, designating this 100µF/25V cap as C1 instead of C2 as is silkscreened onto the board.

Another seemingly prevalent issue with this board is failure of the diodes. If either D8 or D9 fail, the associated motor will turn ONLY counter-clockwise.

The board is controlled by two transistors on the driver board. One transistor "enables" movement of the associated motor. The other determines whether the motor moves clockwise or counter-clockwise.

[[Image:A-15680Schematic.jpg|300px|thumb|left|Schematic for A-15680 Bi-Directional Motor Drive Board.]] 
 

====Double Flipper Opto Switch Board (A-15894) (Type I)====
[[File:Placeholder.jpg|300px|thumb|left|A-15894 Flipper Opto Board Mounted on the Cabinet Wall]] 
This board is used in early WPC games which used the Fliptronics II board starting with Doctor Who (please confirm first game).

Please note when testing these boards, the right flipper board has to be plugged in for the left board to function. This is due to the +12v and ground connections being daisy-chained through the right board PCB to the left board. The manuals will typically claim the opposite. And in some cases, the +12v is daisy-chained via the right opto board, while the ground is daisy-chained via the left opto board.

It is always best to check the wiring in the game. If two gray or orange wires are connected on one side of the cabinet, the +12v and / or ground are daisy-chained to the the opposite side.
 

====Flipper Opto Board Assembly (A-17316) (Type II)====
[[File:A-17316.jpg|300px|thumb|left|A-17316 Flipper Opto Board]] 
This board is used in later WPC games which used the Fliptronics II board starting with Indiana Jones (verify) and was used until Pinball 2000.
 

====HSII & CFTBL Triac board (A-13088-2)====
[[Image:WMS_A-13088-2_Triac_Board.JPG|300px|thumb|left|A-13088-2 Triac Board]]
[[Image:TriacDriverBoard_Schematic.jpg|300px|thumb|right|A-13088-2 Triac Board Schematics]]
 
This board is used in High Speed 2: The Getaway (for the beacon motor), CFTBL (for the hologram motor), and Hot Shot (basketball redemption game). This triac board was also used in the System 11B game, Whirlwind, under board number C-13088. It was used to control the topper fan.

Since the board is single sided, fractured solder joints are frequently a problem with this board, especially at C1 for some reason. The other failure point on this board is the MOC 3031 otpo-isolator.
 

==== 24 Inch Opto Board (A-15646) ====
[[Image:24InchOptoBoard.jpg|300px|thumb|left|WPC 24 Inch Opto Board as used on BSD and Shadow]]
[[Image:24InchOptoBoardSchematics.jpg|300px|thumb|right|WPC 24 Inch Opto Board as used on BSD and Shadow, schematics]]
 
Note: This board is sometimes referred to as the "24 Switch Opto PC Board".

This board is used on Bram Stoker's Dracula to sense the "Mist Ball" and on Shadow to sense when the ball is at the bottom of the mini playfield. The board is also used in Star Wars: Episode 1, NBA Fastbreak, Judge Dredd, and Hot Shot (basketball redemption game). The usual problem with this board is that the large inductor (marked "106C" in the picture) vibrates off the board. The circuitry on this board is similar to a television remote control circuit. It senses a particular signal frequency.
 

==== Eddy Sensor PCB Assembly (A-18543) ====
[[Image:A-18543EddyCurrentSensor.jpg ‎|300px|thumb|left|WPC Eddy Current Sensor Board]]
[[Image:WMS-A-18543-EddyCurrentSensor.jpg ‎|300px|thumb|right|WPC Eddy Current Sensor Board Schematic]] 
This small board is used on Theatre of Magic, Scared Stiff, Road Show and Star Trek: the Next Generation.

This board is connected directly to the WPC switch matrix. Two switch matrix wires, 12VDC and ground are provided at the 4-pin connector. The other two wire connector, as pictured, connects to an inductor mounted into a routed hole in the playfield bottom. Small changes are sensed in the inductor by the board circuitry and indicated on the switch matrix. 

===== Eddy Sensor PCB Assembly (A-18543) Problems =====
'''What Goes Wrong?'''
[[Image:ToMEddyCurrentSensor.jpg ‎|300px|thumb|left|Eddy Current Sensor Board shown "in situ" in a Theatre of Magic. Note how close the proximity sensor is to the bracket.]]
[[Image:EddyCurrentSensor.jpg ‎|300px|thumb|right|Closeup of Eddy Current Sensor. Note how close the proximity sensor is to the bracket.]] 
 
This board can be somewhat problematic.

If the trim POT on the board hasn't been adjusted in quite some time, the POT can form a "dead spot" in the same way that volume POTs do. Twizzling the POT back and forth a few times generally clears this issue.

The POT should be adjusted so that the board is just on the edge of the indicator LED turning off. Test the adjustment by placing a pinball over the sensor on the other side of the playfied.

Note that the sensor will pick up on any metal that is close by. In the picture at left, the playfield brackets were so close that they were causing the sensor to indicate a ball was present. A combination of moving the sensor as far from the metal bracket as possible, and fine adjustment of the trim POT solved the issue.
 

====TAF & TAFG High Power Board (A-15139)====
[[File:WPC A-15139 High Power Board.JPG|300px|thumb|left|A-15139 High Power board as used in TAF and TAFG]]
[[File:TAFHighDriverSchematic.jpg|300px|thumb|right|Schematic for A-15139 High Power board as used in TAF and TAFG]] 
This board (aka magnet board) drives the three under playfield magnets used on The Addams Family and The Addams Family Gold. It is located under the bottom left of the playfield.

If one (or more) of the TIP-102 magnet drive transistors (Q32, Q34, Q44) on the Power/Driver board has failed, be sure to test the TIP-36c transistors on this board. This board is often fragile and therefore quite hacked due to prior repairs. 

====TAF & TAFG Extra Flipper Power Supply (A-15416)====
[[File:WPC A-15416 Extra Flipper PS.JPG|300px|thumb|left|A-15416 Extra Flipper Power Supply board as used in TAF and TAFG]] 
This board powers the upper flippers and the playfield magnets for The Addams Family and The Addams Family Gold. It is located just to the right and just above the driver board in the backbox. 
 
The schematics for this board are incorrect in the Addams Family manual. Specifically J903 is shown incorrectly. J903 Pins 1 and 2 supply 50v for the magnet board under the playfield. Pins 3 and 4 are ground for the magnet board under the playfield. The bridge rectifier diagram is also incorrectly rotated by 90 degrees. 

==== The Shadow Five Switch and Diode P.C.B. (A-13940) ====
[[File:TheShadowDiodeBoard.jpg|300px|thumb|left|This board was used only on "The Shadow" to provide lamp matrix diode isolation for the 4 "Ring Grain of Wheat" lamps, in-situ.]]
[[File:TheShadowDiodeBoardBare.jpg|300px|thumb|right|The bare board.]] 
This board was used only on "The Shadow" to provide lamp matrix diode isolation for the 4 "Ring Grain of Wheat" lamps. Yes, that's really it's name. 

====Coin Door Interface Board====
[[Image:CoinDoorInterfaceBoardAnnotated.jpg|300px|thumb|left|WPC/WPC-95 Coin Door Interface Board]] 
The coin door interface board provides signal connection between the coin door switches and the WPC switch matrix and dedicated switches like the "diagnostic" and volume control buttons. The coin door interface board also creates the "always closed" switch 24 by bridging column 2 and row 4 with a diode. WPC games use this "always closed" switch to identify switch matrix power issues.

If the coin door interface board gets dusty from flipper parts wearing, clean it. That dust is conductive and may cause odd coinage issues. There really isn't much that can go wrong with this board.
 

====WPC Alphanumeric Plasma Display Board====
[[Image:FHDisplayComponentSide.jpg|300px|thumb|left|The component side of the Funhouse / Bride of Pinbot WPC alphanumeric display.]]
[[Image:FHDisplayGlassSide.jpg|300px|thumb|right|The display glass side of the Funhouse / Bride of Pinbot WPC alphanumeric display.]] 
Funhouse and The Machine: Bride of Pin*Bot used dual 16-Alphanumeric displays, and a special (specific) high voltage power supply/logic board. The high voltage circuit is similar, if not identical, to late System 11 high voltage power circuits. 

Harley Davidson also used dual 16-alphanumeric displays, however, they were placed side by side on separate boards, instead of being "stacked" on one board.
 

====Scared Stiff Crate Board====
[[Image:ScaredStiffCrateBoard.jpg|300px|thumb|left|The "Scared Stiff" Crate Board]] 
This simple board mounts to the top of the Scared Stiff crate. It creates the "eyes" that look out the top of the crate. It contains 8 LEDs, 4 current limiting resistors, and 4 diodes, which isolate the LED "lamps" in the lamp matrix. Very little can go wrong with this board other than fractured solder joints, since it lives in a high vibration area of the game.
 

====DC Motor Control Board (A-16120)====
[[Image:A-16120DCMotorControl.jpg|300px|thumb|left|A-16120 DC Motor Control Board]]
[[Image:DCMotorControlBoard.jpg|300px|thumb|right|A-16120 DC Motor Control Board schematics]] 
This board is used in Cactus Canyon, Demo Man, Monster Bash, No Good Gophers, The Shadow, Twilight Zone, Theater of Magic, World Cup Soccer.
 

====Bridge Driver PCB Assembly (A-15946)====
[[Image:A-15946DCMotorControl.jpg|300px|thumb|left|A-15946 Bridge Driver PCB Assembly]]
[[Image:BridgeDriverPCBAssemblySchematics.jpg|300px|thumb|right|A-15946 Bridge Driver PCB Assembly schematics]] 
This board is used in Indiana Jones and Hot Shots Basketball. The board is close in design to the A-16120 DC Motor Control Board (above). For Indiana Jones, it controls the Path of Adventure motor, which must turn both clockwise and counter-clockwise.

This simple assembly receives 12VDC power and ground, along with two solenoid connections to the driver board. Grounding one pin of the connection causes +12VDC to be output at the motor power pins. Grounding the other pin will cause -12VDC to be output at the motor power pins.

Indiana Jones uses solenoid 22 to move the POA left and solenoid 23 to move the POA right.
 

==== Indiana Jones Path of Adventure (POA) Opto Board ====
[[Image:IJPOAOptoBoard.jpg|300px|thumb|left|The Indiana Jones POA opto board. The optos are identical to those used on cabinet flipper switch opto boards.]] 
This simple board is used in Indiana Jones to provide "travel limit" feedback to the MPU for the POA. Typical problems include fractured solder joints, since the board experiences a lot of vibration from the POA motor, as well as simple opto failures.
 

==== Corvette Z5 Master Board (A-18532), Slave Board (A-19625), and Hall Effect Amplification Board (A-19076)====
[[File:Bally Corvette A-18532 Motor Driver Master.jpg|300px|thumb|left|Bally Corvette A-18532 Motor Driver Master]]
[[File:Bally Corvette A-19625 Motor Driver Slave.jpg|300px|thumb|right|Bally Corvette A-19625 Motor Driver Slave]] 
This pair of boards work together to "rev" the ZR1 LT5 engine toy on the upper left side of the playfield. The master board senses the position of the motor unit using a Hall Effect sensor located below the engine toy assembly. The slave board uses 20V power and four TIP-102s to control four coils below the playfield on the ZR1 LT5 assembly.

Debugging information for the ZR1 LT5 assembly can be found [https://www.pinwiki.com/wiki/index.php?title=Corvette#LT-5_Engine_Electronics_issues here].
 
[[File:A-19076CorvettePCB.jpg|300px|thumb|left|Bally Corvette A-19076 Adjustment PCB for the LT-5 assembly]]
[[File:A-19076CorvetteHallSensorAmplifierBoard.jpg|300px|thumb|right|Bally Corvette A-19076 Adjustment PCB for the LT-5 assembly schematics]]
 

==== WPC A-13901 / A-17402-3 (and variants) Opto Ramp Switch Board (3 Opto Controller) ====
[[File:WMS A-17402 3-opto.jpg|300px|thumb|left|WMS 3 Opto Controller Board (as shown under playfield of Indiana Jones)]]
[[File:WMS A-13901 A-17402-3 Schems.png|300px|thumb|right|Schematics for A-13901 / A-17402-3 3 Opto Controller Board (*Note: R10 value was changed to correct 22K value in schems)]] 
There are several variations of the A-13901 / A-17402 3 opto controller board used on several games. Games such as Indiana Jones, CFTBL, Fish Tales, High Speed 2, Hurricane, Slugfest, Funhouse, and Hot Shot all used some version of this board. The part numbers used are:
*A-13901-1-AI
*A-13901-1
*A-13901-2
*A-13901-3
*A-13901-AI
*A-13901
*A-17402-3
 

==== WPC A-19043-1 Stepper Motor Driver Board ====
[[File:A19043-1.jpg|300px|thumb|left|WMS Stepper Motor Driver Board)]]
[[File:Wpc-stepper-motor-driver_a-19043-1_schematics.jpg|300px|thumb|right|Schematics for A-19043-1 Stepper Motor Driver Board. Unfortunately, these schematics do not appear in the WhoDunnit manual or anywhere else.]] 
The Stepper Motor Driver Board is used only in WhoDunnit (Slot Machine Reels). Three of these boards are used to drive the three slot machine reel stepper motors.
 

==== A-21967-2 Serial 24 Drive PCB Assembly; aka The Champion Pub LED Driver Board ====
[[File:TheChampionPubSpecificLEDDriver.jpg|400px|thumb|left|The Champion Pub LED Driver Board. Image courtesy of Chris Hibler]] 
This board is specific to The Champion Pub. While resembling an opto board, it drives LEDs.
 

==== 48 Lamp & Driver P.C.B (A-20909); aka Safe Cracker Backbox Chase Lamp Board ====
[[File:WMSSafeCracterChaseFront.jpg|400px|thumb|left|Safe Cracker Chase Lamp Board front. Image courtesy of PinSider "DumbAss"]]
[[File:WMSSafeCracterChaseBack.jpg|400px|thumb|right|Safe Cracker Chase Lamp Board back. Image courtesy of PinSider "DumbAss"]] 
This board is specific to Safe Cracker. The board uses 4094 shift registers to shift serial data through the 48 lamp board.
 

====NBA Fastbreak Shot Clock Dual PCB Assembly (A-21399)====
[[Image:NBAFBShotclock.jpg|300px|thumb|left|The two PCBs that are sandwiched together for the NBA Fastbreak Shot Clock. Image Courtesy of Chris Hibler]] 
The Shot Clock assembly is driven ("blanking" and "count") from J110 on the PowerDriver board. It is supplied with 12VUR and Ground from J133. ‎During attract mode, the clock will continuously count down from 24 to about 06 (digits blink from 09 on down).

The PCB uses an LM339 to switch blanking and pulse the counter. Onboard are two 4029 binary counter chips and two 4511 7-segment driver chips. Each pulse of the "counter" signal causes the clock to count down one number.

The two PCBs are connected in a similar way as OEM Twilight Zone clock boards are. The male headers are extra long. They mate via the bottom entry female connectors on the dual LED PCB.
 

==== Coin Doubler Board ====
[[Image:WPCCoinDoublerInSitu.jpg|300px|thumb|left|An Aftermarket "Coin Doubler" Board, shown attached to a WPC MPU.]] 
This aftermarket add-on board connects atop the direct switches connector on the WPC MPU. It intercepts the coin switches and, for each switch closure it sees, sends the computer two closures. This "hack" effectively halves game pricing. This was done because Williams removed the one-coin-per-play pricing for some games to try and force a price increase.

These are still for sale from [https://gameboardsusa.com/shop/ols/products/coin-doubler-board-for-wpc-games-turns-50-cent-play-into-25-cent-play Game Boards USA].
 

===Flipper Coils===

WPC games use different flipper coils dependent on flipper placement and application. Below is a chart of the flipper coils used, their wrapper color, and strength.

{| class="wikitable"
!colspan="4" |WPC Flipper Coils
|-
!Part #
!Color
!Strength
!Notes
|-
|FL-11753 || Yellow || Weakest ||
|-
|FL-11722 || Green || Weaker ||
|-
|FL-20867 || White || See notes || Used only in Safecracker
|-
|FL-11630 || Red || Standard ||
|-
|FL-15411 || Orange || Stronger ||
|-
|FL-11629 || Blue || Strongest ||
|}

Notes:

The FL-20867 flipper coil (white wrapper) was used only on Safecracker. The FL-20867 flipper coil is thought to be between an FL-11722 and an FL-11630 in strength.

Williams also produced an FL-17636 flipper coil (blue wrapper) for use in Star Trek: The Next Generation. This coil is somewhat stronger than the FL-11629, and was used on the prototype games - and some number of production games - to facilitate shots to the Delta ramp. At some point during the ST:TNG production run Williams switched back to FL-11629 coils, perhaps because the Delta ramp shot can be made with an FL-11629 coil with new condition flipper mechs, or due to operator reports of breakage. Still, a large number of games seem to show up with FL-17636 coils, leading one to suspect operators may have swapped out the FL-11629 coils to the stronger FL-17636 coils as the flipper mechs wore. (There is probably an increased chance of breaking playfield plastics and other parts with the FL-17636 coils in place.)

[[File:ParallelCoilWindings.jpg|300px|thumb|left|Note the windings of this typical WPC coil. The larger wire is the high power winding, the smaller wire is the hold winding. Both wires are soldered to the lug on the left.]] 

===WPC Transformers===

{| class="wikitable"
|+Transformers
!| Part Number    || Description           || Distinguishing Features || Games
|-
|5610-12718-00 || WPC, 115/230v || 18VAC sound alphanumeric || BoP, FH, HD
|-
|5610-12835-00 || WPC3, 115/230v || 18VAC sound || BoP, BR, BSD, CFTBL, DW, FH, FT, GI, HD, HS2, Hot Shots Basketball, Hurricane, PZ, Slugfest, T2, TAF, TAFG, TZ, WH2O
|-
|5610-13491-00 || WPC Power || 12VAC sound || IJ, JD, Pinball Circus, Popeye, STTNG
|-
|5610-13953-00 || WPC94 || female line input || Corvette, DH, DM, FS, RS, Shadow, WCS
|-
|5610-14515-00 || WPC Wide Mount ||12VAC sound || AFM, Congo, I500, JB, JM, NF, SC, SS, ToM, TOTAN, WD
|-
|5610-14515-01 || WPC Wide Mount || 12VAC sound || AFM, CC, CP, CV, Congo, I500, JB, JM, JY, MB, MM, NBA, NF, NGG, SC, SS, ToM, TotAN, WD
|-
|5610-15930-00 || transformer p2000 || || RFM
|-
|5610-15930-01 || transformer p2000 || || SWE1
|}

====Primary Voltage Selection Jumpers at the Transformer====
On all WPC games, there are either a 9 pin or 12 pin Molex connector used to change the primary voltage setting fed to the transformer. 9 pin connectors were connected to a pigtail off the transformer itself. Later units used a 12 pin connector on the power source metal box located inside the cabinet floor on the right just inside the coin door. Depending on the placement of the jumpers, common configurations are 115v (typical domestic setting), 230v (European setting), and 100v (Japanese setting). 

It is common to change the voltage setting (220 to 120 volt conversion) if a game is re-imported back into the US. Although probably more common at the moment is to convert a domestic game to 220 volts (more games are currently being exported from the US than imported).

All voltage selection pins are .093 molex pins. Removal of the pins requires a special molex tool. See [http://www.pinwiki.com/wiki/index.php?title=General#Headers.2C_Housings.2C_and_Crimping "Headers, Housing, and Crimping].

'''Important Notes:'''
#When jumpered for 120V operation, the line fuse is an 8ASB, and a 130V Varistor is used.
#When jumpered for 230V operation, the line fuse is a 5ASB, and a 260V Varistor is used.
 

====Early WPC Transformers (9 pin connection)====
The 9 pin connectors used are Molex 19-09-2099 (butterfly connection w/jumpers) and Molex 19-09-1099 (connection on transformer pigtail).
[[File:WPCPowerSelectButterfly.jpg|300px|thumb|left|9 Pin WPC Transformer Power Configuration, configured for US 115V systems.]] 
Jumper settings for 115V should be as follows:
*Pin 1 - black - 115v "hot" input
*Pin 7 - white - 115v "neutral" input
*Pins 2 and 3 jumped together
*Pins 8 and 9 jumped together
 

[[File:230VLineVoltageConfiguration.jpg|300px|thumb|left|9 Pin WPC Transformer Power Configuration, configured for 230V systems.]] 
Jumper settings for 230V should be as follows:
*Pin 1 - black - 230v "hot" input
*Pin 7 - white - 230v "neutral" input
*Pins 3 and 9 jumped together
 

====Later WPC Transformers (12 pin connection)====
[[File:Plug2.JPG|300px|thumb|left|12 Pin WPC Transformer Power Configuration, configured for US 120V systems]]
[[File:Plug1.JPG|300px|thumb|right|12 Pin Connector as Found inside later games]] 
'''Jumper settings for 120v should be as follows:'''
*Pins 1 and 11 jumped together
*Pins 2 and 3 jumped together
*Pins 7 and 10 jumped together
*Pins 8 and 9 jumped together

The 12 pin connector used is Molex 19-09-1129.
 

[[File:WPCEuropeanPowerSelectSascha12Pin.jpg|300px|thumb|left|12 Pin WPC Transformer Power Configuration, configured for European 240V systems]] 
'''Jumper settings for 240V should be as follows:'''
*Pins 1 and 11 jumped together
*Pins 7 and 10 jumped together
*Pins 3 and 9 jumped together
 

===Unused Connectors===
[[File:FactoryTestConnectorOrDeletedFeature.jpg|300px|thumb|right|An example of a "leftover connector". This one appears on the game "No Fear".]] 
Some WPC games include connectors in the backbox or under the playfield that are not used in the production configuration of the game. Possible reasons for this include:
* Connectors were originally installed to support features that were later removed when the game went to production. It was easier/cheaper to simply leave the connectors in place.
* The connectors may have been test connectors that could be used during assembly to ensure all features were operating correctly.
* As explained by a former cable harness designer, some automated wire cutters were limited to a maximum cut length (perhaps 100 inches). If the harness required a wire longer than the maximum cut length, the factory would include a molex connector in the design to achieve the necessary length piecemeal.
 

==Problems and Solutions==
=== General Oddball Problems that Seemingly Defy Logic ===
[[file:SystemReset.jpg|300px|left|thumb|Factory Reset option, used to, you guessed it, return the same system to factory settings]]
Occasionally, a problem such as display artifacts, failing display test, or general illumination dimming working incorrectly (just a few among a whole host of oddball problems) can be cured by performing a "Factory Reset". Factory Reset can be found in the "Utility Menu", U.8. Performing a factory reset will delete high scores and all other settings but will also clean up any "garbage" that may reside in the RAM chip (or NVRAM chip) responsible for the oddball behavior.

[[image:YT.png]] A YouTube video demonstrating what appears to be a DMD Controller RAM problem but was actually caused by garbage in MPU RAM can be viewed [https://youtube.com/shorts/awPA_U-9sN4 here].

[[image:YT.png]] A YouTube video demonstrating a factory reset to address a General Illumination problem can be viewed [https://youtu.be/bbYkc-ge6dE?si=EIZJOLSQCQwNooeO here]. 

=== Jumpers, RAM and ROM size ===
[[Image:WPC089Jumpers.jpg|300px|thumb|left|Closeup of WPC-089 MPU that uses a 6264 RAM and a 4M game ROM. Note jumpers W1, and W2 to set ROM size as well as W3 (out) and R93 (in) to set RAM size.]]
[[Image:WPC089MPUwith62256RAM.jpg|300px|thumb|Right|Closeup of WPC-089 MPU that uses a 62256 RAM and a 4M game ROM. Note jumpers W1, and W2 to set ROM size as well as W3 (in) and R93 (out) to set RAM size.]]

RAM Size 
The WPC-089 MPU can be configured for two different RAM sizes. This is done with jumper W3 and resistor R93 as shown below.
*6264 RAM - W3 out, R93 in (a 1.5K 1/4W resistor)
*62256 RAM - W3 in, R93 out
Both RAM sizes work fine in all games. Williams probably provided this flexibility to allow use of whichever RAM was cheaper or more available. Note: Most NVRAM replacements are 6264 replacements.

[[Image:WPC95RAMSizeJumper.jpg|300px|thumb|left|Closeup of WPC-95 MPU that uses a 62256 RAM. Note jumper W3 is installed to set the RAM size for a 62256 RAM.]]

The WPC-95 MPU can be configured for two different RAM sizes. This is done with jumper W3 (only) as shown below. R93 is always installed.
*6264 RAM - W3 out
*62256 RAM - W3 in
Again, both RAM sizes work fine in all games and most NVRAM replacements are 6264 replacements.
 

ROM Size 
The MPU can also (and needs to be) jumpered for different ROM sizes. This becomes important when upgrading ROMs or swapping a CPU (and ROM) into a different game. Games like Funhouse shipped with a 1M ROM, jumper W2 in, and jumper W1 out. Updating the Funhouse ROM to a larger size ROM requires W1 in and W2 out.

The official Williams ROM size/jumper settings are shown below.
* 512K/1M - W1 out, W2 in
* 2M/4M - W1 in, W2 out
 

===Test ROMs===
Test ROMs are available from [http://www.planetarypinball.com/mm5/Williams/tech/testroms.html Planetary Pinball], but they should only be used in conjunction with a [http://pinballrehab.com/1-articles/solid-state-repair/board-rework-test/243-building-a-wpc-test-fixture test fixture] and not installed in an actual game, as per the official recommendation.

=== Country DIP Switch (or jumper) Settings ===
[[File:WPCCountryCodeJumperMessage.jpg|300px|thumb|left|Country Code Jumper message.]] 
The message shown at left occurs sometimes when the game software seems to want the "country code" jumpers to be configured in a certain way. The simple solution (for English speaking users) is to remove the jumpers noted in the message by cutting them off. This sets the board to "AMERICA2". Twilight Zone, and perhaps game ROM version 9.4H, seem to prefer the "AMERICA2" country code. Other country code jumper configurations are shown below.
 

[[File:WPCCountryCodeJumpersExample.jpg|200px|thumb|left|Two WPC-089 MPUs, one configured with DIP switches, the other with "zero ohm resistors" (jumpers).]] 
Two WPC-089 MPUs are shown at left. Early versions of the MPU used "zero ohm resistors" or jumpers to figure the country code. Later versions of the MPU (as well as WPC-S and WPC-95 MPUs, used DIP switches. 

Note: If a dip switch is installed, always leave W11 and W12 in the OFF position. If both are set on ON, the undervoltage detection circuit on the WPC Power/Driver will not work and both LED2 and LED3 will always remain on.
 

[[File:WPCCountryCodeJumperTable.jpg|400px|thumb|left|WPC-089 Country Code Jumper Table]] 
The complete WPC-089 country code jumper table is shown at left.
 

[[File:WPC95CountryCodeJumperTable.jpg|400px|thumb|left|WPC-S/WPC-95 Country Code Jumper Table]] 
The complete WPC-S/WPC-95 country code jumper table is shown at left. WPC-S/WPC-95 MPUs do not have an "AMERICA2" configuration.
 

===Power-On LEDs and Sound Tones (Bongs)===
When the game is booted, several LEDs in the backbox will light, and the game may provide sound "bongs" to indicate diagnostic status.

A properly booting WPC game will show a "progress bar" on the DMD along with a "ticking" sound which results from a series of reset signals being sent to the sound board. After a successful boot, the sound board will create a single "bong" tone.

==== LEDs on the MPU ====

Note: WPC and WPC-S games label the MPU and Power/Driver board LEDs as "Dxx". WPC-95 games label these same LEDs "LEDxxx".
*D19 (LED201) - "Blanking". This LED should light when power is applied, then after about 1 second, go off and stay off. If D19 remains on, this is an indication that the blanking circuit is turned on which prevents the game from powering coils. The blanking circuit was implemented to eliminate the possibility of damaging the game due to locked on coils when the CPU isn't operating properly.
*D20 (LED203) - "Diagnostics". Once the blanking LED turns off, this LED should begin blinking and remain blinking as long as the game is turned on. This LED is a simple "I'm working" indication from the MPU. This LED is toggled from pin 35 of the ASIC (DLED signal). D20 will also indicate basic issues with the MPU by blinking as such...
**One blink - problem with the game ROM.
**Two blinks - problem with the game RAM (or accessing the RAM, i.e. open traces).
**Three blinks - problem with the ASIC (WPC) or a problem with the security chip (WPC-S and WPC-95).
*D21 (LED202) - "5VDC present". This LED provides a simple indication of the presence of 5VDC. This LED isn't CPU controlled. It's illuminated as long as 5VDC is present.

[[image:YT.png]] A YouTube video of an MPU blinking D20 twice, indicating a RAM issue, can be found [https://youtu.be/7ZEYIVXgDTo here]. 
[[image:YT.png]] A YouTube video of a properly working MPU, showing LED behavior at boot can be found [https://youtube.com/shorts/u3pM0WrxlD4?si=I7EiQvek1b4szexS here].

'''Note:''' It is possible for the switch column IC, U20, to be blown and the damage continuing upstream to U14. In this case, it is possible that the data signals become corrupt and prevent the MPU from booting. D19 and D21 will light but D20 will never light.

[[File:WPCLEDBehavior.jpg|800px|thumb|left|Graphic provided by Ingo Kramer. Used with permission.]] 
[[File:WPCLEDBehaviorUpdated.gif|800px|thumb|left|Graphic provided by Sascha Voksuil. Used with permission.]] 
 

==== LEDs and test points on WPC-089 Power/Driver Boards ====
[[File:WPCBowTie.png|700px|thumb|left|WPC Power/Driver Board "bow tie" of LEDs Normally Lit]] 
The image at left shows the 5 LEDs that are normally lit, forming a "bow tie" (or X-Wing Fighter, if you prefer). Note that some WPC Power/Driver boards are populated with LED2 and LED3 which were meant to indicat high/low line voltage. In practice, those LEDs don't provide that information very well, and should be ignored. 

{| class="wikitable"
! LED/Test Point 
!Explanation
|-
|<center> '''LED1-TP3''' </center> || Normally lit. Indicates presence of regulated 12VDC (12VR). AC voltage is rectified to about 18VDC by BR1 and smoothed by C6 and C7 (this power is tapped for the lamp matrix). D1 and D2 are used to drop the voltage by 1.0 to 1.4V and then the voltage is further regulated down by the LM7812 at Q2. This 12VDC power is shown as "+12V Digital" on the schematics. This power is fused by F114. If LED6 isn't lit, LED1 won't be lit either.
|-
|<center> '''LED2-no TP''' </center> || If installed, provides an indication of high/low line voltage. This LED isn't very useful as it will flicker as power consumption by the game fluctuates.
|-
|<center>  '''LED3-no TP'''  </center> || If installed, provides an indication of high/low line voltage. This LED isn't very useful as it will flicker as power consumption by the game fluctuates.
|-
|<center> '''LED4-TP2''' </center> || Normally lit. Indicates presence of regulated 5VDC. AC voltage is rectified by BR2 and smoothed by C5. The voltage is regulated down by the LM323K at Q1. This 5VDC power is shown as "+5V Digital" on the schematics. This power is fused by F113.
|-
|<center> '''LED5-TP7''' </center> || Normally lit. Indicates presence of unregulated 20VDC. AC voltage is rectified by BR4 and smoothed by C11. The voltage is used to power the flash lamps. Note that beginning sometime during production of Twilight Zone in 1993, a "coin door interlock" switch was added. This switch interrupts power to both the 20VDC and 50VDC circuits when the coin door is opened, providing a measure of safety against higher voltage shocks. If the coin door is opened with power applied, this LED will fade to off. It will not light with the coin door open. This power is fused by F111.
|-
|<center> '''LED6-TP8''' </center> || Normally lit. Indicates presence of unregulated 18VDC. AC voltage is rectified to about 18VDC by BR1 and smoothed by C6 and C7. This 18VDC power is used to power the lamp matrix lamps. This power is fused by F114.
|-
|<center> '''LED7-TP1''' </center> || Normally lit. AC voltage is rectified to about 12VDC by BR5 and smoothed by C30 to provide unregulated 12VDC power. This 12VDC power is shown as "+12V Power" on the schematics. It is used to power motors, optos, and other game features that do not require a precise 12VDC. This power is fused by F116.
|-
|<center> '''TP4''' </center> || Zero Cross. By using an oscilloscope, this test point allows testing of the "zero cross" circuitry. "Zero cross" is when the AC sine wave crosses through the zero voltage point relative to ground. Zero cross is important for the proper operation of the general illumination lamp circuit.
|-
|<center> '''TP5''' </center> || Ground. This test point stud may be used to measure all DC voltages against.
|-
|<center> '''TP6''' </center> || 50VDC power. This test point will actually measure 70 - 75VDC, which is normal and expected. This power is used for all coils in the game including the flippers. This power is fused by F112. Individual coil power circuits are fused by F101 thru F105. F112 protects both BR3 and the bridge rectifier circuit on the FlipTronic II board. Should F112 blow, remove J104 (or J105). Replace the fuse. Power on. If the fuse blows, BR3 has probably failed. If it holds, the bridge rectifier on the FlipTronics II board has probably failed.
|}

[[File:WPC089 power summary.png|800px|thumb|center|Summary schematic of WPC-89 Power Driver board showing test LED's and test points. A PDF of this image can be viewed [[Media:WPC089 power summary.pdf|here]]]]
 

==== LEDs and test points on WPC-95 Power/Driver Boards ====

{| class="wikitable"
! LED/Test Point 
!Explanation
|-
|<center>  '''LED100-TP100'''  </center> || Normally lit. Indicates presence of regulated 12VDC. AC voltage is rectified to about 18VDC by D11-D14 and smoothed by C11 and C12. D1 and D2 are used to drop the voltage by 1.0 to 1.4V and then the voltage is further regulated down by the LM7812 at Q2. This 12VDC power is shown as "+12V Digital" on the schematics.
|-
|<center> '''LED101-TP101''' </center> || Normally lit. Indicates presence of regulated 5VDC. AC voltage is rectified by D7-D10 and smoothed by C9. The voltage is regulated down by the LM317K at Q1. This 5VDC power is shown as "+5V Digital" on the schematics.
|-
|<center> '''LED102-TP102''' </center> || Normally lit. Indicates presence of unregulated 18VDC. AC voltage is rectified to about 18VDC by D11-D14 and smoothed by C11 and C12. This 18VDC power is used to power the lamp matrix lamps, and is subsequently regulated to 12V for use in the switch matrix.
|-
|<center> '''LED103-TP103''' </center> || Normally lit. AC voltage is rectified to about 12VDC by D3-D6 and smoothed by C8 to provide unregulated 12VDC power. This 12VDC power is shown as "+12V unreg" on the schematics. It is used to power motors and other game features that do not require a precise 12VDC.
|-
|<center> '''LED104-TP104''' </center> || Normally lit. Indicates presence of unregulated 20VDC. AC voltage is rectified by D15-D18 and smoothed by C10. The voltage is used to power the flash lamps. Note that a "coin door interlock" switch is present on all WPC-95 games. This switch interrupts power to both the 20VDC and 50VDC circuits when the coin door is opened, providing a measure of safety against higher voltage shocks. If the coin door is opened with power applied, this LED will fade to off. It will not light with the coin door open.
|-
|<center> '''LED105-TP105''' </center> || Normally lit. Indicates presence of unregulated 50VDC. This test point will actually measure 70 - 75VDC. This power is used for all coils in the game. AC voltage is rectified to about 75VDC by D19-D22 and smoothed somewhat by C22.
|-
|<center> '''TP106''' </center> || Zero Cross. By using an oscilloscope, this test point allows testing of the "zero cross" circuitry. "Zero cross" is when the AC sine wave crosses through the zero voltage point relative to ground. Zero cross is important for the proper operation of the general illumination lamp circuit.
|-
|<center> '''TP107''' </center> || Ground. This test point stud may be used to measure all DC voltages against.
|}
[[File:WPC095 power summary.png|800px|thumb|center|Summary schematic of WPC-95 Power Driver board showing test LED's and test points. A PDF of this image can be viewed [[media:WPC095_power_summary.pdf|here]]]]

==== Power on Sound Tones (Bongs) ====

After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs.

Pre-DCS Sound Board Games.
*1 - No issues...enjoy a game.
*2 - U9 RAM failure.
*3 - U18 ROM failure.
*4 - U15 ROM failure.
*5 - U14 ROM failure.

DCS Sound Board Games.
*1 - No issues...enjoy a game.
*2 - U2 ROM failure.
*3 - U3 ROM failure.
*4 - U4 ROM failure.
*5 - U5 ROM failure.
*6 - U6 ROM failure.
*7 - U7 ROM failure.
*8 - U8 ROM failure.
*9 - U9 ROM failure.
*10 - U10-U12 RAM failure. Note: DCS sound board RAM failures are indicated by a message on the display, "U10-U12 RAM error".

Audio/Video Board Games (WPC-95).
*1 - No issues...enjoy a game.
*2 - S2 ROM failure. Note: Two bongs also occur if jumper W3 is IN, and the RAM size is 6264. If an NVRAM was just installed, check this jumper. See the section on [[Williams_WPC#Jumpers.2C_RAM_and_ROM_size | jumpers]].
*3 - S3 ROM failure.
*4 - S4 ROM failure.
*5 - S5 ROM failure.
*6 - S6 ROM failure.
*7 - S7 ROM failure.
*10 - U9, U10, or U11 RAM failure (see below)

[[File:WPC95U9-U11Error.jpg|300px|thumb|left|WPC-95 boot time RAM error message, accompanied by 10 very annoying bongs.]]
[[File:WPC95U10U12Message.jpg|300px|thumb|right|WPC-95 boot time RAM error message, accompanied by 10 very annoying bongs.]] 
A/V sound board RAM failures are indicated by a message on the display, either "U9-U11 RAM error" or "U10-U12 RAM error". This is apparently game software dependent. A/V RAM are, in fact, U9-U11. Apparently, this message wasn't updated in the software with the introduction of the A/V board. 

===Fuses===

Fuses are used to protect the various game circuits when a problem arises and the circuit begins to draw more current than originally designed to draw.

The best way to test a fuse is to remove it from it's fuse holder and "buzz" it with a DMM set to continuity. This method will prevent false positives via "sneak circuits". When removing fuses from a RottenDog aftermarket power/driver board should be done with extreme care as the fuse clips are easily bent and damaged.

====WPC/WPC-95 Fuse Tables====

[[File:WPCFuseList.jpg|400px|thumb|left|WPC Fuse Table from Twilight Zone.]]
[[File:WPC95FuseList.jpg|400px|thumb|right|WPC-95 Fuse Table from Monster Bash.]] 
A typical WPC fuse table is shown at left, WPC-95 fuse table at right.
 

==== F111 Blows, Testing BR4 With Board Still Installed====

[[File:TestingWPC-BR4-InSitu.gif|300px|thumb|left|Click this image for an animation showing how to test BR4 without removing the power/driver board. Animated gif provided by Sascha Voksuil, aka PinSider ZaZa. Used with permission..]] 
Fuse F111 sits between the transformer secondary and BR4. BR4 recitifies AC power for the flash lamps. If BR4 failes shorted, F111 will blow, protecting the transformer secondary winding.

BR4 can be tested "in situ" using the method shown in the animated gif at left. The correct values would be between .4-.6 if this is not clear from the gif. 
Note: This test requires a good fuse to be in place at F111 for the test to work properly.
 

===Melted Blue/White Transformer Secondary Wires at Connector J101===
[[File:MeltedTransformerSecondaryBlueWires.jpg|300px|thumb|left|Melted wires originating at transformer secondary. Image courtesy of Scott Mount.]]
[[File:MeltedTransformerSecondaryBlueWiresAtPowerDriverBoard.jpg|300px|thumb|right|Those same wires, at Power/Driver Board connector J101. Note that the wires have been restuffed into a new IDC connector. This wiring is now correct. Image courtesy of Scott Mount.]]
[[File:J101Short.jpg|300px|thumb|left|A depiction of a short circuit created with connector J101 installed "one pin off". Note the connector is shifted one pin "down".]] 
It is poor practice to repin less than the complete connector. Since J101 often burns and can the source of game resets, operators sometimes clip the lower 5 pins of J101, and then "hack" the connector by adding a 4-pin connector for the two blue/white wires that loop through the original IDC connector. With pin 3 being the "key pin", it then becomes possible to connect the hacked 4-pin connector "one pin off". As depicted in the diagram at left, this causes a direct, and un-fused short. The blue/white wires will heat quickly and melt the insulation, acting like fuses. If power is left on long enough, the next victim will the transformer itself.

To avoid this disaster completely, always repin the full connector and always use a key pin and key plug.
 

===Testing DC Voltages on the Power/Driver Board===
[[File:YT.png]] A YouTube video showing how to test each of the voltages on the WPC-089 Power/Driver board can be found [https://www.youtube.com/watch?v=uz6bnFiCki0&lc=UgwKkBxANoJnz3Xjr3Z4AaABAg here].

===Removing or Installing the ASIC===
[[File:ASICRemovalTool.jpg|300px|thumb|left|Using a PLCC puller to properly remove the ASIC. Grip firmly, and "rock" the chip out gently.]]
[[File:AnotherWPCCrackedASICSocket.jpg|300px|thumb|right|A cracked ASIC socket caused by using other than the correct tool to remove the ASIC.]] 
Should ASIC need to be removed from a WPC MPU, it is strongly advised that tthe proper tool is used, as shown at left. The tool is called a PLCC puller. 
[[File:YT.png]] A video showing the proper technique for removing the WPC ASIC can be found [https://www.youtube.com/watch?v=qKmlsTlagfg here].
 

[[File:DamagedWPC-ASIC.jpg|300px|thumb|left|This ASIC was damaged by not using the proper removal tool.]]
[[File:WPCCrackedASICSocket.jpg|300px|thumb|right|This cracked ASIC socket caused intermittent operation of the game.]] 
Using a jewelers screwdriver or other such tool can fracture the ASIC chip carrier socket as shown at right. Since these are 84 pins sockets, replacement is non-trivial. Using the incorrect tool may also irreparably damage the ASIC itself by permanently fracturing leg joints, as shown at left.
 

[[File:WPC89ASICOrientation.jpg|300px|thumb|left|Correct orientation relative to the PLCC socket, shown here for a WPC-089 or WPC-S MPU board.]] 
The ASIC must be oriented correctly when installed. Pin 1 of the ASIC is marked with a dot impression on the top of the chip. Pin 1 of the PLCC socket is marked with an arrow pointing to pin one. This is true for all versions of WPC MPUs. Orient the ASIC as shown in the picture at left relative to the arrow in the socket, center the chip over the socket, and press firmly on the chip center.
 

=== WPC ASIC Pinout ===
[[File:ASICIcon.jpg|300px|thumb|left|WPC ASIC pinout and board connections|link=https://www.pinwiki.com/wiki/index.php?title=File:WPCASICPinOutRevisionA.pdf]] 
Clicking on the thumbnail at left will open a .pdf file containing pin connections for the WPC (in work) and WPC-S MPUs.
 

[[File:ASICPinOutSmall.jpg|300px|thumb|left|WPC ASIC pinout and board connections|link=https://www.pinwiki.com/wiki/images/e/e1/WPCASICPinoutviaZaza.jpg]] 
Clicking on the thumbnail at left will open a .pdf file containing a graphic image of the ASIC pinout, ''provided courtesy of Sascha Voskuil''.
 

===Minimum Parts Required for WPC MPU to Boot===
[[File:WPCMinimumParts.jpg|300px|thumb|left|The exact minimum parts required for a WPC MPU to boot]]
Pictured at left is a partially populated MPU board. It has been included here for those building their own MPU board to indicate a interim state for testing work in progress. The image represents the exact minimum parts required for a WPC MPU to boot. Note that the switch matrix resistors and capacitors are not necessary.
 

===Game blows power line circuit breaker immediately===
[[File:WPCPowerBoxInside.jpg|300px|thumb|left|Underside of power box showing varistor and thermistor]]
Had a thunderstorm roll through or a power surge from the electric company recently?
The varistor in the power box may have done it's job protecting the rest of the game's circuitry from the possibly tremendous power surge. 

Signs of a failed varistor are typically black, charred discoloration throughout the "button" portion (green in the case of the adjacent picture) of the varistor. Likewise, varistors can blow rather violently, and there may be charred or burnt remains in the area surrounding the varistor. 

Over time, the rating of a varistor will lower, causing "occasional" blowing of the mains fuse. The varistor will visually appear to be OK. A good hint is how violently the fuse blows. Likely varistor problems will cause the fuse to totally obliterate.

Varistors can be purchased from [https://www.greatplainselectronics.com/products.asp?cat=76 Great Plains Electronics]. Order the 130V variant for 120VAC (typically games in the US), and the 275V variant for 240VAC (typically games in Europe).
 

===Credit Dot===
[[file:Credit dot sttng.jpg|300px|left|thumb|Example credit dot on Star Trek The Next Generation]] 
The credit dot is a decimal point (a single, lit pixel on the display), that appears after the number of credits or after the words free play on the DMD display on WPC games. It is a quick indicator used to tell the operator or owner that there may be an issue with the game. Most commonly, there is a switch or multiple switch problems with the game. However, a credit dot will appear for other reasons, such as when the date and time are not set. 

If, after 30 balls or 10 games, a particular switch hasn't registered, the credit dot is posted to alert the user to check the diagnostics. Some high usage switches will trigger the alert earlier. The credit dot may or may not indicate a real problem. For the example shown in the pic, it's simply reporting a switch that is hard to hit in the game. So, the credit dot is actually saying "Play Better". :-)
 

===Battery Issues===

====Relocating the battery from the MPU board====
[[File:WPC CPU Bat Damage.JPG|left|thumb|300px|An example of worse than usual battery damage]] 
Relocating the 3xAA battery pack from the MPU board is always a good idea. Leaky alkaline batteries are the #1 killer of MPU boards. Simply removing the batteries is not an option with WPC games as a message stating "Factory Settings Restored" will be received when the game boots.
 

There are several options other than allowing the battery pack to remain on the MPU board. Below are the two most common methods. 

The first, most common, and most economical option is to remotely locate the battery holder off the MPU board and somewhere below all other boards. This ensures that even if the remotely located batteries leak, they won't leak onto (or even drip onto) any circuit board. Replace the batteries annually, dating them with a Sharpie. Connections are as follows. With the CPU oriented as it would be in the game, solder the red (positive) wire to the upper right battery pack position. Solder the black (negative) wire to the lower left battery pack position. Note: most battery packs do not come with wire leads long enough to allow the battery pack to rest in the backbox bottom. Lengthen the wires as necessary. As can be viewed in the adjacent picture, a male / female .093" Molex connector was added to easily remove the battery pack from the MPU board should the need arise.
<center>
<gallery widths=300px heights=300px perrow=3 caption="WPC, WPC-S, and WPC-95 Remote Battery Holder Connections.">
File:WPC MPU Battery Relocate.JPG|<center>WPC-089</center>
File:WPC-SMPUBatteryConnections.jpg|<center>WPC-S</center>
File:WPC95RemoteBatteryHolder.jpg|<center>WPC-95</center>
</gallery>
</center>
 

====Installing an external battery on a WPC-95 CPU using the Auxiliary Battery header (J213)====
[[File:WPC95AuxBatteryHeader.jpg|300px|thumb|left|Installed Remote Battery Connector]]
[[File:WPC95RemoteBatteryOption.jpg|300px|thumb|right|An alternate, but equivalent method. Positive and Negative are clearly labeled.]] 
The WPC-95 CPU board has an unused external battery connector just above the battery holder. The connector is labeled J213 AUX BAT. The 4 pads can be seen in the above picture of the CPU with the old holder removed. Installing this 4-pin connector is a good and clean way to get the batteries off the board and prevent alkaline damage. The Molex part number for the C-Grid® SL™ 70543 4 pin connector is 70543-003 (Digikey WM4802-ND). Crimp pins for the female side are 16-02-1125 (WM2573-ND) and the housing is 50-57-9404 (WM2902-ND). The WPC-S CPU uses a 5 pin version of this connector.
 
Warning: Do not use both the internal and external connector at the same time. Doing so will likely damage the batteries.
 

====Settings Not Held or Battery Depletes Rapidly====
[[File:WPC MPU D1 D2.JPG|left|thumb|300px|A WPC MPU board with D1 and D2 circled. D1 and D2 are in the identical location on the WPC-S MPU]]
[[File:WPC-95MPUD1D2.jpg|right|thumb|300px|A WPC-95 MPU board with D1 and D2 shown in the middle of the picture, just below the battery holder]]
During the process of installing a remote battery holder, it is a good practice to check the diodes utilized in conjunction with the battery power. Diode D2, a 1N4148, is used to keep the MPU board's logic power from charging the batteries in the battery pack. Diode D1, a 1N5817, is used to keep the battery pack from powering the entire MPU board when the games's power is turned off. 
*If D2 fails shorted, 5VDC power will be applied to the batteries while the game is turned on. The end result is batteries which die prematurely, possibly leak, and/or possibly explode (alkaline batteries do not like to be charged).
*If D2 fails open, the batteries will not power the static RAM, and the "FACTORY SETTINGS RESTORED" message will be displayed when the game boots.
*Should D1 fail, the batteries would more than likely just deplete prematurely.
 

[[File:TestingForPowerAtRAM.jpg|left|thumb|300px|Probing pin 28 of the WPC-95 MPU RAM IC for Vbb (battery backup power)]]
[[File:6264RAMPinout.jpg|right|thumb|300px|Pinout of the 6264 RAM. Note Vcc, upper right, pin 28]] 
Testing to see if battery backup power is reaching the RAM with sufficient voltage is easy.
*Set your DMM to DC Voltage
*Connect the black probe to game ground (in the picture at left, a clip lead is attached to the ground screw)
*Use the red lead to probe pin 28 of the RAM
Measuring in this way should yield over 3.5 VDC. If measuring shows 0 VDC, either the batteries are dead, or D2 has failed (see above).

Ideally, this measurement should yield 1.5 VDC * 3 - .6 VDC = 3.9 VDC. This calculation represents the nominal voltage delivered by a single AA battery, times 3 (batteries), less a typical .6 VDC drop across diode D2. Remember that nominal voltage drop across a typical diode is .5 to .7 VDC.
 

===Replacing the CPU RAM with non-volatile RAM===
[[file:WPCR93.jpg|300px|left|thumb|A WPC-089 MPU board with 6264 RAM, jumper W3 removed, and R93 in place.]] 
A second option is to replace the 6264 static RAM with an NVRAM such as the RAMTRON FM1608 (or FM16W08). NVRAMs in the standard DIP package are becoming hard to find but several pinball parts vendors sell a nice 6264 replacement NVRAM based on these parts.

This method requires desoldering the OEM RAM from the board, and installing a socket on the MPU. Using NVRAM also has the down-side of not maintaining the Real Time Clock. This is meaningless in some games. But some games use the Real Time Clock, like Twilight Zone which moves the playfield clock to the current time of day during attract mode, and Who?Dunnit and Junk Yard which has a "Midnight Madness" feature. Note: the WPC MPU is designed to accept either a 6264 or a 62256 static RAM. See: [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Jumpers.2C_RAM_and_ROM_size Jumpers, RAM and ROM size] for a description of jumpers required when installing a new RAM or NVRAM. It is known that a Ramtron FM1608 chip does not like the voltage to be lower than 4.5V. With a voltage drop of 0.5V across D1, a jumper wire over D1 would be a solution to this problem. You can also just replace the diode D1 with a jumper wire. On a WPC-95 CPU-board you have the option to add W5 in stead of the jumper wire for D1. The result is the same.
 

====Special note Concerning Early RottenDog WPC-TH MPUs and NVRAM====
[[file:EarlyRDMPU.jpg|300px|left|thumb|A RottenDog WPC-TH MPU. Note PCB date code of "0701", circled in yellow.]]
[[file:RottenDogCypress.jpg|300px|right|thumb|Another RottenDog WPC-TH MPU. This one has no date codes at.]]
Most RottenDog MPU boards shipped with a 62256 RAM installed vs the 6264 RAM typically installed in Williams OEM boards. Early versions of the RottenDog board marked with "0701" on the silkscreen, as pictured at left, require the use of a 62256 NVRAM. The reason for this is that the address lines to the RAM position are not JEDEC "standard". Pins 9 and 10 (normally A0 and A1) are tied to ground as can be seen in the image below. A4 and A5 are mapped to pins that are not connected (NC) on a 6264. Thus, the RottenDog non-JEDEC compliant PCB layout will not work correctly with a standard 6264 device. But with a 62256, which has two extra address lines mapped as they are on the RottenDog WPC MPU board, will work perfectly fine.

Another early production board that requires a 62256 but is not marked with a date code, is pictured at right. This MPU shares the same non-JEDEC compliant PCB trace connections but has no date codes of any kind anywhere on the board 

[[file:PrototypeRDSurfaceMountMPU.jpg ‎|300px|left|thumb|A prototype RottenDog WPC MPU that used surface mount components.]] 
The surface mount version of a RottenDog MPU pictured at left was probably never productionized. The board featured a Cypress non-JEDEC compliant 62256 RAM. While it would be unlikely see another example of this board, it would require a surface mount FM18W08 NVRAM also. 

<gallery widths=200 heights=400 class=center>
File:RD62256NVRAM.jpg ‎| A RottenDog WPC-TH OEM installed 62256 RAM
File:RD62256Socket.jpg ‎| The RottenDog WPC-TH MPU RAM position. Note connection between pins 9, 10, and 14 (ground), which corresponds to the Cypress 62256 RAM pinout.
File:CypressCY62256.jpg | The pinout of the Cypress 62256 RAM, which matches the PCB design of the WPC-TH board
File:FM1608PinOut.jpg | The pinout for a typical FM1608 (6264) NVRAM, which is JEDEC compliant
</gallery>
 

=== Repairing Alkaline Corrosion ===
[[file:WPCCorrosion.jpg|300px|left|thumb|A WPC-089 MPU board, after a couple hours of alkaline corrosion abatement.]]
[[file:AlkalineCorrosionCleanupWithLampSocketCleaner.jpg|300px|right|thumb|Using a "lamp socket cleaning stick" for precision removal of alkaline corrosion. These can be acquired at The Pinball Resource.]] 
Alkaline damage abatement on WPC MPUs is generally more difficult than Bally -17/-35 or Stern MPU-100/200 or Gottlieb System 80 MPUs. The traces on WPC MPUs are finer, and more abundant than on any of those boards. And, the "banks" of resistors and ceramic capacitors below the ULN-2803 and LM339s provide numerous hiding places for alkaline damage. The small traces under these components implement the switch matrix on the game.

If alkaline abatement is attempted, and if the ULN-2803 or LM339s are damaged, using any technique other than cutting them off the board, heating the alkaline damaged pads, and pulling the leftover legs out, WILL damage the board further. The alkaline adheres to the component legs and through-holes very strongly, making it near impossible to remove the component using typical desoldering tools, no matter how skilled the individual is.

As is normally done during this process, sand with fine grit sandpaper (or use an abrasive stick as shown on the right for precision work) until bare copper can be seen, treat the board with 50/50 white vinegar/water to neutralize bits of alkaline that may remain (but do your best to remove ALL alkaline damage), then rinse thoroughly with isopropyl alcohol or other favorite cleaner. Re-tin or conformal coat the exposed traces.
 

<center>
<gallery widths=300px heights=300px perrow=3 caption="Replacing an Alkaline Corroded LM339 on a WPC-089 MPU">
File:LM339-1.jpg|<center>A corroded LM339</center>
File:LM339-2.jpg|<center>After cutting one side off, then bending repeatedly to break the other side off</center>
File:LM339-3.jpg|<center>Socket installed. All done. A machine pin socket was used here to allow soldering on both sides of the board. Normally, "dual wipe" sockets are preferred as they have a much longer mate/unmate cycle life.</center>
</gallery>
</center>

[[file:RottenDogAlkalineCorrosion.jpg|300px|left|thumb|A Corroded WPC-089 Aftermarket RottenDog MPU board.]] 
The RottenDog WPC-089 MPU board pictured at left is an extreme example of corrosion creep. Corrosion moved all the way up the remote battery holder wires and onto the MPU. Abating alkaline corrosion on RottenDog MPUs is particularly difficult as the traces and vias are very, very small.
 

'''WPC-089 MPU Alkaline Corrosion Zone''' 

[[file:Wpc89-cpu-lower-parts.jpg|300px|left|thumb|Part identification in the WPC-089 MPU corrosion zone. Image courtesy of Pinsider Sascha Voskuil aka Zaza]] 
Part identification in the WPC-089 MPU corrosion zone.
 

'''WPC-95 MPU Alkaline Corrosion Zone''' 

[[file:WPC95MPUCorrosionAreaParts.jpg|300px|left|thumb|Part identification in the WPC-95 MPU corrosion zone.]] 
Williams located the batteries for the WPC-95 MPU in an even worse location than on WPC-089 and WPC-S boards. With the batteries located above the ASIC socket, there is a substantial probability that severe damage could occur from leaky batteries. The usual alkaline abatement process should be followed.

'''Key:''' 

   Resistors - Blue 
   Capacitors - Yellow 
   Diodes - Red 
   Integrated Circuits - Green 
   Headers/Jumpers - Black 

Note that at least two revisions of the WPC-95 MPU board were produced, each with a slightly different part layout.
 

=== Slam Tilt ===

[[file:WPCSlamTilt.jpg|300px|thumb|left|A WPC game (STTNG) that has been "slam tilted".]] 
WPC games incorporate a slam tilt switch on the back side of the coin door. When closed, the game immediately stops, and the display fills with diagonal lines, as pictured at left. Note that this is not a power problem like a "game reset", below.
 

===Stuck Menu Settings (WPC-95)===
* Clear all the audits and reset to factory defaults.
* If using a battery for the RAM, remove/disconnect the batteries for a few minutes. Power up and check the settings to verify whether or not settings have become unstuck, then power off and reconnect the batteries.

====Stuck Language Setting (WPC-95)====
[[file:WPC95CountryCodeJumperTable.jpg|400px|thumb|right|DIP Switch language setting chart]]
If the MPU language can't be changed via the settings menu, it is possible that the DIP switch bank has failed.
* Be sure that the DIP switch language switches are set correctly as detailed in the table at right.
* Ensure that a DIP switch hasn't failed by buzzing for continuity across a closed switch.
* Use test T.15, "Dip Switch Test", to ensure that the MPU is reading the switches correctly. If the physical DIP switch settings do not match the T.15 test indications, then either the DIP switch has failed, or U11, a 74LS240, has failed.
[[file:Wpc95-dip-switch-test.jpg|400px|thumb|right|Test T.15, "DIP Switch Test"]] 

If there is a bad flipper opto board, this may also cause the language to get stuck (possibly in Spanish) and prevent the language from being changed in the menu settings or by using the MPU's DIP switches. Be sure to replace/repair the bad flipper opto board, then the language should then be able to be changed ([https://pinside.com/pinball/forum/topic/wpc-95-stuck-on-spanish-language-setting Discussion on Pinside])

=== Power Problems with the RottenDog aftermarket power/driver board ===
====Fuse Clips====
[[file:RottenDogFuseClips.jpg|300px|thumb|left|Fuse clips on a RottenDog WPC power/driver board.]] 
The fuse clips used on the popular RottenDog aftermarket power/driver boards are a bit brittle and do not snap back into position if too much bending force is applied to them, much like Data East power supply fuse clips. Once the fuse clip has been bent too much, it will not snap back into position to create a solid mechanical connection to the fuse. This can cause one of the various power voltages to be missing or intermittent.
 

====5V Regulator====
[[file:RottenDog5VRegulator.jpg|300px|thumb|left|The PTR08060WVD, used on RottenDog WPC Power/Driver Boards.]] 
Since the LM323K 5V regulator has been obsolete for many years, RottenDog Power/Driver boards were designed to use a DC-to-DC converter manufactured by Texas Instruments, part number PTR08060WVD. The part can be found [https://www.mouser.com/ProductDetail/595-PTR08060WVD here] and possibly at other vendors.

Note: This part is installed on a RottenDog Power/Driver board with the inductor (copper coil) facing the top of the board. Equivalently, pin 1 of the device should be installed into the left-most PCB through-hole.
 

===Game resets===
One of the more annoying faults exhibited by WPC machines is the chronic reset problem. The game will restart, often when both flippers are used at the same time. Note that game resets are a power issue. "Slam Tilts" are something completely different (see above).

There are several possible reasons for game resets. Before doing '''''any''''' work on the circuit boards, it is recommended that a number of much easier to fix, and just as probable root causes, be examined.

Possible causes are listed below, in the recommended order of examination. This order is a derived from a combination of "ease of examination" crossed with "probability of root cause". The standard advice dispensed on RGP to change BR2 and C5 is often wrong and unnecessary. If BR2/C5 are changed out and the game no longer resets, some will conclude that, sure enough, BR2/C5 was the problem. What is being missed is that along with replacing those components, at the very least, the connectors on the board are being reseated, the solder on the cap and bridge is being reflowed, and the board ground to the backplane is perhaps better due to torquing the screws better. Any of these changes can improve voltage/current enough to reduce the frequency or eliminate resets.

==== The "Replace BR2 and C5 Mantra" ====
And now, a word on the classic "BR2/C5 mantra".
[[File:NutAFingaS.jpg ‎|left|300px]]
[[File:BR2Mantra.jpg ‎ ‎|right|300px]]A long time ago…in a pinball galaxy far, far away…a kindly fellow was playing a nice game of pinball, hitting all the shots, and earning multiball after multiball. Just as he was about to beat the game’s high score to date, the WPC MPU reset. "Not-A-Finga" he yelled in some ancient, dead, language.

A visitor from the neighboring planetary system noted that, "I once fixed that by replacing BR2 and C5". And lo...the mantra was born.

Fortunately, through advances in both our knowledge of these game systems, and the application of clearer thinking, we’ve come to realize that leaping to the “solution” of replacing components before doing real testing is not advisable. Most pinball owners do not possess the skill, experience, and tools that would allow them to work on circuit boards without damaging an expensive, and sometimes irreplaceable board.

Still, with regular frequency, a post will be made on one of the Facebook repair groups or on PinSide that goes something like this…"My game was resetting so I replaced BR2 and C5 and the resets vanished." This logical construct is known as [https://en.wikipedia.org/wiki/Post_hoc_ergo_propter_hoc "Post hoc, ergo propter hoc"] (after this, therefore because of this), an insidious logical fallacy that states "Since that event followed this one, then that event must have been caused by this one". Clearly, this is an invalid assumption. The fallacy lies in coming to a conclusion based solely on the order of events, rather than taking into account other factors that might rule out the connection. 

In reality of course, when components are removed and replaced on a circuit board, attendant "changes" to the state of the game system include…

# reseating connectors and possibly improving electrical conductivity
# possibly changing the connectivity through fractured solder joints which may be flexed differently
# reseating the entire board in the backbox and possibly improving ground for the board
# reflowing solder joints on both components possibly improving electrical conductivity
# possibly improving heat dissipation from the bridge to the heat sink by replacing thermal grease
# perhaps an air conditioner, refrigerator, or heater has shut off thereby increasing available electrical current

So please, hold off on heating up the soldering iron until methodically working through the disciplined process in the following section.

==== WPC 5VDC Power Derivation Path ====
Following is the nominal path from the wall plug to eventual consumers of the clean 5VDC power supplied by the Power/Driver board.
[[file:WPCPowerSelectButterfly.jpg|300px|thumb|right|WPC Transformer Power Configuration Plug, configured for US 120V systems.]] 

#120VAC/60Hz power is nominally provided at the wall plug. Different voltages are accommodated also (see below)
#An RFI (radio frequency interference) filter, which is seldom a contributor to game problems.
#Line power is connected to a service outlet sometimes incorporated into the metal "power box" and made available to the tech via a short, uniquely plugged, extension cord. Line power is wired in parallel and does not require the power switch to be in the ON position.
#Both sides of the AC power pass through the double pole/double throw (DPDT) game power switch
#The "black" side of the AC power passes through an 8A FB fuse housed in a bayonet style (screw in) fuse enclosure.
#The "black" side of the AC power then passes through the thermistor, which limits current inrush into the system.
#"Butterfly" voltage select connector used to accommodate typical voltage systems used around the world (120VAC in US, 230VAC abroad, low line voltage, etc). When configured for 120VAC in the US, the connector and wiring resemble a butterfly.
#Transformer Primary windings
#Transformer Secondary windings
#Yet another Molex connector, mating with the harness that will eventually lead to the Power/Driver board.
#Some games incorporate a "coin door interlock switch" which interrupts coil and flasher power when the coin door is open. If the game is equipped with this switch, there will be an extra Molex connector necessary to implement this switch.
#J101 on the Power/Driver board (WPC-95: J129)
#Full Wave AC rectification and smoothing via BR2 and C5 (WPC-95: D7 through D10 and C9)
#Regulation to 5VDC via the LM323K at Q1 (WPC-95: LM317 at Q1))
#Lighting LED4... (WPC-95: LED101)
#And finally, delivery to 5VDC power consumers via J114, J116, J117, and J118 (WPC-95: J101, J138, J140, and J141)

[[file:WPC95LM317VoltageAdjustResistors.jpg|300px|thumb|left|WPC-95 Voltage Adjust resistors R1 and R1]] 
Note that the LM317 is an adjustable voltage regulator where the LM323K is a 5V specific regulator. The LM317 is "programmed" to 5.108V using precision resistors R1 (750 ohms) and R2 (243 ohms), located just to the right of the LM317 heat sink. It is possible, although not advised, to adjust the output of the LM317 regulator to something other than the nominal 5.108 volts.
 

==== Possibly Skip Steps ====
If the game is resetting only within the first minute or two, and plays fine after that, skip to [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Failed_Thermistor Step 8, Failed Thermistor]. If the thermistor turns out to not be the cause, return to step 1.

==== The "Quick" but Temporary "Fix" ====
[[file:WPCJ101InSitu.jpg|300px|thumb|left|Connector J101 In-Situ (bottom of picture)]]
A quick but temporary fix might be to reseat (remove and then reinstall) J101 and J114 on the Power/Driver board and J210 on the MPU board several times. This might help in two ways.

First, the tarnish that builds up on the male/female connections might be removed slightly. This might be enough to return your game to service quickly. But this is not a long term repair. The proper repair is to repin both the male and female sides of the connectors.

Second, the physical point where the male/female pins meet becomes "welded" over time. That is, the pins develop micro-divots or irregularities that detract from a perfect connection. Reseating the connection may smooth out the defects that have formed and also might move the physical point of contact to a different part of the pins.

Again, reseating these connectors is a temporary fix that might work for a day, a week, or a month.

[[File:YT.png]] A Youtube video of this procedure being performed on a Bram Stoker's Dracula can be found [https://www.youtube.com/watch?v=8Pf7gRSlKo4 here].
 

==== Low Line Voltage ====
''Step 1: measure line voltage''
[[file:TestingLinePower.jpg|300px|thumb|right|Measure line power at the wall plug that the game is plugged into (not on the bench, as shown here). Almost 118VAC...Nice...]]
Low line voltage can occur for several different reasons...

*Peak summer usage may cause a drop in line voltage (at the wall). Nominal voltage should be 115VAC minimum.
*Too many games or "power hungry" devices on the same circuit. This is common when numerous devices are plugged into a power strip.
*Game(s) plugged into an extension cord or power strip with too small of wire gauge. If the game is plugged into an extension cord, make sure that it carries all three conductors and is constructed of '''at least''' 16 gauge wire, or specified as 16/3. Using a beefier 14/3 extension cord is better, and advised if more than one game is plugged into the cord.

If the machine is resetting, open the coin door and measure the AC voltage at the auxiliary socket with the machine turned off, and then with the machine turned on. If the voltage at the auxiliary socket is over 105VAC, the problem is most likely inside the game. If the voltage is below 105VAC, there is a line voltage problem and the local electricity company's help will be needed to correct the problem. 

==== Poor Ground Connection for Power/Driver Board ====
''Step 2: Make sure the power/driver board is screwed down tightly''

[[file:PoorWPCDriverBoardConnection.jpg|300px|thumb|left|As my friends in Texas might say, "that dog won't hunt". All backbox boards must be securely screwed down.]] 
A poor ground connection from the power/driver board to the backbox ground plane can reduce 5VDC by as much as .3 volts. Ensure that the screws that hold the power/driver board down, secure it tightly. 

==== Cracked Power or Ground Header Pins and Cracked Solder Joints at the 5V Fuse ====
''Step 3: Examine the header pins at J101, J102, and J103 as well as at the LM323K regulator (WPC-95: J136 and J137)''

[[file:WPCGroundHeaders.jpg|300px|thumb|left|Cracked header pin solder joints at J103 in a Twilight Zone, causing game resets.]] 
Similar to step 2 above, cracked header pins where the power enters the board or at the ground connections on the board can cause game resets. In the picture at left, cracked header pins at J103 (ground) in a Twilight Zone caused game resets. Either reflow the solder, or better yet, replace the headers with new pins.
 

[[file:FracturedSolderJointLM323K.jpg|300px|thumb|left|Fractured solder joints at the LM323K 5V regulator (WPC-95: LM317), causing game resets.]] 
Another place to examine for fractured solder joints is on the solder side of the board, where the LM323K (WPC-95: LM317) 5VDC regulator is placed. This area is subjected to very high temperatures that sometimes causes the solder to crystallize. If the solder joint is in any way suspect, remove the old solder and reflow new solder on the joint. Ensure that a nice solder "meniscus" is created (a volcano shaped solder joint) versus a "doughnut" around the wire lead.
 

[[file:F113CrackedSolderJoint.jpg|300px|thumb|left|Fractured solder joints at fuse F113.]] 
Fuse F113 (WPC-95: F105) fuses the 5V power for the game. Fractured solder joints here may cause the DMM to read near 5V, yet the joint doesn't allow enough current to pass. This can cause game resets and even cause the game to not boot. Reflowing the solder at these joints is prudent.
 

==== Missing diodes, open diodes, or cold solder joints at the Flipper coils ====
''Step 4: Examine flipper coil diodes''

[[File:ParallelCoilWindings.jpg|300px|thumb|left|Example flipper coil diodes shown on a FL-15411 flipper coil.]]
 
WPC flippers are, in general, the only coils in the game that should have diodes across the coil lugs. While diodes seldom fail, sometimes the pounding environment that flipper diodes must live within causes solder joints to fail. Ensure that each flipper coil has the required two diodes, that the diodes are good, and that they are soldered to the coil lugs with a quality solder joint. 

==== Poor Connections between the Transformer Secondary and the Power/Driver Board ====

''Step 5: Examine the "cube shaped" molex connector in the cabinet''

[[file:WPCTransformerSecondaryConnection.jpg|300px|thumb|left|The 15-pin Molex "cube" connector. The red wires carrying 9VAC to the Power/Driver board can be seen here.]] 
The connections from the transformer secondary to the Power/Driver board can degrade over time, a natural result of hours and hours of "power on" time. Try re-seating each connector. If the reset frequency is reduced or disappears, then the root cause has probably discovered. These connectors should be repinned at a minimum with at least new pins (the connector housings may be salvageable) for a long term solution. It is especially important to re-pin the red 9VAC wires that carry power to the Power/Driver board as this is converted to the 5VDC logic voltage.

Note: the molex pin extractor for these "round" pins is relatively expensive but there is no other good way to remove the pins.
 

==== Poor Connection at J101 on the Power/Driver Board ====
"Step 5.5: Examine both male and female connectors at J101 (WPC-95: J129)"

[[file:WPCJ101InSitu.jpg|300px|thumb|left|Connector J101 In-Situ (bottom of picture)]] 
J101 (WPC-95: J129) connects the transformer secondary supply of both 9VAC (solid colored red wires, ultimately used to create 5VDC power) and 13VAC to the power/driver board. This connector often becomes tarnished, increasing resistance and reducing the effectiveness of the circuit. Reseating the connector may temporarily reduce reset frequency. This is an indication that this connector should be repinned. As always, it's best to repin both the male and female connectors.
 

==== Poor Connections between the Power/Driver board, the CPU, and other PCBs ====
''Step 6: Examine other wiring harnesses and the connectors''

[[file:WPCPickingUpGround.jpg|300px|thumb|left|A convenient location to find ground in a WPC backbox.]]
[[file:WPCTesting5VDCatTP2.jpg|300px|thumb|left|Measuring DC voltage at the 5VDC test point, TP2.]] 
Measure DC voltage at TP2 (WPC-95: TP101) on the Power/Driver board.
#DMM set to DC volts (if not an auto-ranging meter, expect to measure 5VDC)
#Black lead secured to game ground (the ground braid in the head is a good place to pick up ground)
#Red lead on TP2 (WPC-95: TP101). Remember the reading.
 

[[file:WPCTesting5VDCatGameROMPin32.jpg|300px|thumb|left|Measuring DC voltage at pin 32 of the game ROM]] 
Measure DC voltage at the CPU board.
#Again, DMM set to DC volts
#Black lead in the same place
#Red lead on pin 32 of the game ROM, or on pin 2 (center pin) of the MC34064 under voltage watchdog at U10
#Record this reading

Compare the two readings. ANY difference indicates voltage loss between J114 on the power/driver board and J210 on the MPU board. Some voltage loss is expected/natural since no circuit path can provide zero resistance. A difference of .1VDC is enough to warrant examination of the connectors between J114 (WPC-95: J105) on the Power/Driver board and J210 on the CPU board.

Reseating the wire harness that connects the power-driver board to the CPU board may identify the root cause (but reseating is not a long term solution).
 

[[file:WPCZConnector.jpg|300px|thumb|left|The "Z" connector, as used in Twilight Zone, etc.]]
[[file:WPCZConnectorHarness.jpg|300px|thumb|right|The entire harness containing the "Z" connector in Twilight Zone can be removed from the game for easier repinning.]] 
Some games use an interceptor harness to power extra boards (IJ, TZ, WH20, STTNG, FT, etc). There is a inline splice connector (commonly called a Z-connector) between the driver board and the CPU board. The Z-connector can become loose and/or oxidized, contributing to a poor electrical connection between the female connectors. The Z-connector can be replaced with a new one, or more robustly, eliminated by splicing the wires together, soldering, and heat-shrinking. This entirely removes the Z-connector as a contributing factor to game resets.

At least on Twilight Zone, the wire harness that contains the "Z" connector can be removed from the game entirely, as shown at right. This harness has been repinned and the "Z" connector eliminated.
 

[[file:PoorIDCConnections.jpg|300px|thumb|left|A poorly "repunched" IDC connector. This connection was probably "punched" with a small flat-blade screwdriver. Note the bare wires where the insulation has been damaged. Yikes!]] 
Some field techs will "repunch" IDC connectors in an attempt to make a better connection. Without the correct punch tool, sometimes an even worse connection is created, as pictured at left. If the decision is to use IDC connectors, at least use the correct tool to punch the wires.
 

[[file:WPCWornPowerConnectionJ210.jpg|300px|thumb|left|MPU connector J210. This connector has had the plating worn off right where the female connector mates with it. When mated with a worn female connector, increased resistance results in reduced voltage, causing resets and possibly failure to boot.]] 
Tarnished, heat damaged, or damage to header pin plating creates resistance and can sometimes be a contributor to game resets. If the male header pins are tarnished, their female mates are probably tarnished also. If tarnished pins are found, now might be a good time to remove that aspect as a contributor to game resets.
 

If following this step-by-step process, now is the first time that a soldering/desoldering station will be needed.

Replace the male header pins, remembering to clip the correct "key" pin before reinstalling the board into the game.

Replace the female connector and pins with good quality Trifurcon crimp-on pins. IDC (Insulation Displacement Connectors) connectors as found originally on the game were used by the OEM to speed the manufacturing process and do not provide the level of robustness that can be achieved using Trifurcon crimp-on pins and good technique.

Another possible contributor to poor power connections is cracked header pin solder joints. Although, with WPC double-sided PCBs and the relatively large header pin through-holes, this is rarely seen. Should you identify cracked header pin solder joints, it's best to remove as much of the old solder as possible before reflowing new solder at the joint.

Be sure to check the power connections on the display as well. One documented repair involved a Funhouse with a reset issue. The game had a strong +5V signal on the MPU/CPU, a new BR2/C5 and digital voltage regulator. It would play perfectly until someone nudged the machine causing it to reset. During troubleshooting, it was noted that the game would reset (even in attract mode) when the display was lifted out of the backbox or placed back in it. It was then observed that the 2 wire/3 pin power connector had a loose IDC connection. The ground short through vibration was resetting the CPU! Repinning both the male and female ends of this connector with a proper molex housing resolved the issue.
 

==== Using a Multimeter to Test the Bridge Rectifier and Capacitors ====
''Step 7: Bridges and Caps in circuit''

[[file:WPCTestingBR2RectifiedDCVoltage.jpg|300px|thumb|left|Measuring "un-smoothed" DC voltage output from BR2. The voltage is smoothed later by C5. This bridge is functioning properly.]] 
There's one last test we can do before disassembling parts of the machine. This test can clearly identify a bad bridge rectifier or capacitor. You will need a clip lead.

#With the machine off, clip the lead onto the top left lead (positive) of BR2. You will have to do this by feel, as you cannot see the lead. This clip point is the output of the bridge rectifier, and is connected to the smoothing (filter) capacitor and LM323K regulator input. It should be at 9V DC.
#Next, place the other clip on the red (+) lead of your meter.
#Connect the black lead to ground by tucking it under the braid. Check your installation to make sure that nothing is shorting.
#Set your meter to DC volts.
#Turn on the game.

The meter should read about 9V. This will be true whether C4/C5 are working or not. If the bridge rectifier is bad, it will read about 7V.

For the capacitor, turn your meter to AC volts. Note that inexpensive meters may give false readings here. Ideally, your meter should be a true RMS meter. Good capacitors will read about 300mV AC. Bad capacitors will read up to 2VAC. Anything over 1VAC indicates a failed/failing filter capacitor at C5 which should be replaced.
 

==== Failed Thermistor ====
''Step 8: Examine the Thermistor''

[[file:WPCPowerBoxInside.jpg|300px|thumb|left|A look inside a typical WPC power box. This particular box was from a Fish Tales. The Thermistor is grey, the varistor is green.]] 
The thermistor is (generally) a black or grey disk, about the size of a dime. It is located inside the power box which is found just inside the coin door and to the right. If your game has one (and not all WPC games do), it will be connected in series between the power box fuse and the black side of AC power. Note that the power box may also contain a "varistor", or MOV, which is essentially a surge protector. The varistor will be wired in parallel with (across) the AC power. The varistor is not a factor in game resets.

The thermistor's job is to limit current inrush into the capacitors when the game is first powered on. This reduces stress on the bridge rectifiers or diodes in the game's power circuits (which is the primary cause of bridge rectifier failures). After a few seconds, the thermistor heats up and drops to a very low resistance. Failing thermistors pass less current and have to get hotter to work. This heating takes time, so the game will often reset in the first 30 minutes of operation, and then be fine afterwards. Obviously, a cold environment will make the symptoms worse, and a warm room may appear to cure the problem. 

Resetting while the game warms up is therefore a key indicator of a failing thermistor. Note also that DCS and WPC-95 A/V boards may reset independent of the MPU. If this is the case, you'll hear the characteristic same "bong" as when the game boots. 

'''***Safety Warning***''' Unplug the game '''AND''' turn the game off before conducting the following test.

Sometimes, the thermistor may be visibly damaged. However, it may look good and still be bad. An easy test of the thermistor is to jumper across the legs of the thermistor with a heavy gauge wire. If the game resets no longer occur, replace the thermistor with the correctly rated part. The original Williams part number is 5016-12978-00. A replacement is available from [http://www.greatplainselectronics.com/search.asp?pg=1&stext=5016-12978-00 Great Plains Electronics].

While you have the box open try wiggling the connectors (the game '''''IS''''' unplugged!) you probably will find at least one that is loose - this can contribute to reset issues. The fix is to solder all the crimp quick connect ([http://www.pinwiki.com/wiki/index.php?title=File:DSCF0810.JPG examples on coil]) wires to the pins they were connected to in the box: cut the quick connects off, one at a time, and then solder the wires directly. Insulate the connections with Heat-Shrink or a good grade of electrical tape.

==== Questionable Prior Rework ====
''Step 9: Examine prior rework''

The printed circuit boards used in pinball machines sometimes have traces on both sides of the board. Most WPC boards are manufactured in this way. The traces are joined through the board by a thin layer of copper, plated to the inside of the hole. This plating is delicate. Without great care, the plating can pull out or crack when components are removed, especially alkaline damaged components as found on MPU boards (after batteries have leaked) and "snap caps" as found on OEM WPC Power/Driver boards (at C5 for instance).

Extreme care as well as good technique must be exercised when removing these components as it is very easy to lift traces or damage through-holes on the board. If the component is known to be bad, it is sometimes easier to snip the component from the board with a flush cutter and remove each leg of the component individually.

An excellent way to repair a lifted trace or cracked through-hole is to create a [http://www.pinwiki.com/wiki/index.php?title=General#Repairing_traces_or_creating_a_.22solder_stitch.22 solder stitch] between the traces on each side of a two sided board. Some PCB repairmen will install jumpers as a "repair" for cracked through-holes or to "guarantee" connectivity between components. Some PCB repairmen will avoid the use of jumpers in favor of better looking rework.

==== Failed Capacitors ====
''Step 10: Power smoothing capacitors at end of life''

[[file:WPC-C4InSitu.jpg|300px|thumb|left|C4, shown "in-situ" on a typical WPC Power/Driver Board. A new C4 cap has been installed on this board (100µF/10V). Nice job by the installer orienting the cap so that its value is in easy view!]] 
Electrolytic capacitors do not last forever. They are designed to operate for about 1,000 hours at their full rating. Capacitor life is a function of temperature: the cooler the capacitor operates, the longer the life. The system designer must select higher voltage and capacitance ratings to achieve the design life, which can be as short as 5 years in a pinball machine operated continuously in a warm environment.

The WPC Power/Driver board uses a 15,000µF, 25V capacitor at C5 to smooth the full wave rectified AC from BR2. When this capacitor is no longer smoothing the rectified AC well enough to produce a clean 5VDC, the voltage may drop below the threshold enforced by the watchdog circuit on the MPU (an MC34064 at U10). When this happens, resets sometimes result.

Note that commonly available replacement capacitors are rated to 35V, and will work fine for this application. In general, you may use a capacitor rated for higher operating voltages but the capacitance specification (µF, or micro-farads) should not be changed.

C4 (spec'd at 100µF, 10V, axial) can sometimes fail and cause the game to reset also. If you've gotten this far and are replacing C5, you might as well replace C4 too.
 

[[file:PulledThroughHole.jpg|300px|thumb|left|A good view of a 15,000uf cap, with a pulled through hole still on the left lead (the brown donut looking object)]]
[[file:DomedFilterCap.jpg|300px|thumb|right|C5 (lower) and C11 (upper) on a WPC-089 power/driver board. C11 is clearly "domed", a physical indication of it's failure.]] 
Removing the big 15,000uf capacitors on a WPC-089 power/driver board is a bit tricky. More often than not, an amateur will damage the through hole that connects one side of the board to the other, either severing the connection completely, or badly enough to cause intermittent reset issues. Should the through hole be pulled, a [http://www.pinwiki.com/wiki/index.php?title=General#Repairing_traces_or_creating_a_.22solder_stitch.22 solder stitch] needs to be installed, or "jumpers" need to be installed connecting the associated bridge rectifier to the capacitor.

Advice: Without the experience, tools, and technique to accomplish this task, most hobbyists would be well advised to send the board to a pro for rehab.

[[File:YT.png]] A video demonstrating an excellent technique for removing snap caps can be found [https://youtu.be/rs90-UMtCww here].
 

==== Failed Bridge Rectifier ====
''Step 11: Test Bridge Rectifier #2 (BR2)''

The thermistor protects the bridge rectifiers from inrush current. Still, bridge rectifiers will occasionally fail.

''Testing a bridge rectifier is simple.''

[[File:TestingABridgeRectifierFourSteps.jpg|300px|thumb|left|Four Connections to Test a Bridge Rectifier. Black/Red dots represent test lead positions.]] 
The picture at left illustrates the 4 readings to be taken when testing a bridge rectifier.

'''Procedure:'''

#Place your DMM into "diode test".
#Put the black lead of your DMM on the "oddball" lead of the bridge rectifier. This will be the lead that isn't oriented the same as the others (as with the "spade" type of bridge) or the lead that prevents the four legs from forming a square (as with the "wire lead" type of bridge). This will also be the DC positive lead of the bridge.
#Place the red lead of the DMM on each of the adjacent legs, one at a time.
#A reading nominally between .5 and .7 should be seen (this represents the voltage drop across the bridge's internal diodes).
#Swap locations of the red and black leads. A reading of "null" should be seen.
#Now place the red lead of the DMM on the lead opposite of the "oddball" lead, or the DC negative lead of the bridge
#Place the black lead of the DMM on each of the adjacent legs, one at a time.
#Again, a nominal reading between .5 and .7 should be seen.
#Swap locations of the red and black leads. A reading of "null" should be seen.
 

[[File:TestingBridgeRectifier.jpg|300px|thumb|left|Testing a Bridge Rectifier in circuit. This part of the bridge is good.]] 
Readings outside of these ranges indicate a failed or failing bridge. Note that these readings are not "hard and fast". For instance, a reading of .462 is probably acceptable. We are looking for an "open" or a "short". Note also that this test is not conducted "under load" and it is possible for the bridge to test "good" when it will in fact fail under load (this is also true when testing diodes, transistors, etc).
 

[[File:WPC Brdg 1and2 Removed2.JPG|300px|thumb|left|Applying heat transfer grease (heat sink compound) to the new bridge rectifiers.]]
[[File:WPC Brdg 1and2 Removed3.JPG|300px|thumb|right|New bridge rectifiers screwed to heat sink before placing on driver board.]] 

[[File:YT.png]] A video demonstrating the procedure to test and properly replace a bridge rectifier can be found [https://youtu.be/QhcnkAKYMlE here].

Should you decide to replace the bridge, it is best to screw the heat sink to the bridge before soldering it in place as the heat sink is shared between BR1 and BR2. A small amount of heat sink compound between the bridge and the heat sink is necessary. This compound improves conduction of the heat away from the bridge and into the sink. 

Some repair tips suggested cutting the heat sink in half, separating it into two parts, one part for each bridge. This technique is no longer considered to be a best practice.

Solder both the top and bottom solder pads of the bridge. Should the through-hole of the bridge leads be cracked or otherwise damaged, use the "[http://www.pinwiki.com/wiki/index.php?title=General#Repairing_traces_or_creating_a_.22solder_stitch.22 solder stitch]" technique noted above or install jumper wires between the DC outputs of the bridge and the terminals of C5. When clipping the leads of the wire bridge, do not cut into the solder "meniscus" (the "volcano" of solder around the wire lead). Cutting into the solder meniscus can cause cracked solder joints later. 

[[File:WPC Brdg 1and2 Removed.JPG|300px|thumb|left|Bridge rectifiers 1 and 2 removed elegantly with a desoldering iron.]]
[[File:WPC Brdg 1and2 Reinstalled.JPG|300px|thumb|right|New bridge rectifiers installed, and replacement date noted.]] 
With proper desoldering tools, like the Hakko 808 or Hakko 470D, removal of bridge rectifiers and other components is greatly simplified. After replacement of bridge rectifiers is made, it's not a bad idea to mark the replacement date. In doing this, you or anyone else will know when these were replaced, and more importantly that they were replaced. 

==== Failed Voltage Regulator ====
''Step 11: When all else fails...''

The LM323K 5V regulator is a robust device, but it can drift over time to below the design requirement of 4.8VDC. If your 5VDC reads less than 4.8VDC at the test point, or less than 4.75V on the CPU board, you have to replace the regulator. Note that these voltages are compliant to the LM323K's spec. However, at the lower end of this spec, this lower voltage may be the cause of resets.

[[File:EZ-SBC-PS5.jpg|300px|thumb|left|The EZ-SBC PSU5 modern adjustable switching voltage regulator]]
If you decide to replace the LM323K regulator you may wish to consider using an [http://www.ezsbc.com EZ-SBC PSU5] instead. The PSU5 is a 5V 3A high-efficiency switch-mode regulator that is a direct replacement for the LM323K in terms of form factor and current capacity; it is superior to the LM323K due to its reduced power dissipation. When using the PSU5 be sure to replace the KEPS nuts (nuts with captive lock washers) originally used to mount the LM323K with discrete #6 split lock washers and #6-32 hex nuts; the external tooth lock washer of the KEPS nut can contact one of the surface-mounted components on the PSU5.

Note: The EZ-SBC PSU5 has one side affect that may be annoying. At power off, instead of the customary "pop", the speakers emit a loud volume "machine gun" or "fart" sound. While this might be unnerving, it is perfectly harmless. An [https://ezsbc.shop/products/psu5-no-noise updated "no noise" version of the PSU5], identified by a yellow solder mask, does not have this side effect at power off. It is otherwise identical to the original PSU5. 
[[File:YT.png]] An example of the sound can be heard [https://youtu.be/L4MDGddZanI?t=80 here] near the end of the video.
 

==== Failed Electrolytic Capacitor on the MPU ====
''Step 12: Failed C31 on the MPU''

[[File:FailedC31onWPCMPU.jpg|300px|thumb|left|C31 on the MPU. This Philips capacitor has most likely failed.]]
There is one more possibility. C31 acts as a filter on the WPC-089 MPU. It is a 100µF, 10V capacitor, connected between incoming 5VDC and ground. Williams used two primary suppliers for this capacitor, Philips and Illinois Capacitor. If the capacitor is grey with black markings and has the logo "iC" on it, then it is from Illinois Capacitor and is likely ok. However, if the capacitor is blue and shows the manufacturer as Philips, you should replace it as it is most likely bad. The small Philips capacitors in particular have shown an increasing failure rate as these machines get older. This does not only apply to their use on the CPU but anywhere else in the machine. Which means the same rule applies to C4 on the power driver board - if it's a Philips capacitor replace it. If it's an iC capacitor it is likely OK. If you have a spare CPU, swapping the suspect one with a known working CPU is a good diagnostic step.

When replacing this capacitor it is best to use a 100uf 25v capacitor. You should note that by the time Williams got to the WPC-95 system, any place where they used to use a 100uf 10v filter capacitor they now had a 100uf 25v capacitor instead.
 

[[Image:BSDcaprs.jpg|300px|thumb|left|Failed C31 from a BSD CPU.]]
[[Image:FHcaprs.jpg|300px|thumb|right|Failed C31 from a Funhouse CPU.]]
Determining whether or not C31 has failed is a challenge without an ESR meter. A simple visual inspection will not indicate whether the part is good or bad. Here are two C31s, one from a Funhouse and one from a BSD. Both of these are bad. Both should have an ESR reading of less than 2 ohms and a capacitance reading, out of circuit, of 100uf if not slightly more. Both the boards these were installed in would boot successfully on the bench hooked up to a dedicated power supply. Without an ESR meter, one might think these capacitors were fine. In fact, if this was the only thing wrong in the machine on the 5v circuit, chances are the game would operate fine with these capacitors as-is. But if the game is resetting, it is probably best to replace C31.
 

==== The Absolute Last Resort ====
''Step 42: We really didn't want to get to this point!''

'''There is a method of absolute last resort.''' 

The LM323K is an adjustable linear regulator. However, Williams provided no means to adjust the output of the LM323K. As such, the LM323K will deliver a voltage anywhere within the spec range of the device. The spec output voltage range for the LM323K is 4.75 to 5.25 VDC. Some percentage of LM323Ks will fall into the lower range of that spec, which is at, or just above the trip point voltage of the MC34064 voltage watchdog on the MPU board.

The following procedure will increase the output voltage of the LM323K slightly. This procedure is not a substitute for addressing all of the considerations mentioned in previous steps, and should be used cautiously.

[[File:LM323KHackComponentSide.jpg|thumb|300px|right|Ground Trace severed leading to C9.]]
The LM323K draws a small current to operate, which it passes to ground. We can use that current to raise the voltage of the whole LM323K, pushing the output closer to 5V. 
'''Procedure:'''
#Isolate the LM323K's metal case from board ground by cutting the ground traces that run left and right from the nut on the back of the board that bolts the LM323K to the board. The neater you make these cuts, the easier it to reverse this hack.
#Some versions of the Power/Driver board include a ground trace on the component side of the board that provides a ground to the tantalum capacitor at C9. This trace must be cut on the component side of the board.
#Add a 1/2W resistor in series, from the LM323K ground to the board's ground trace.
 

[[File:LM323KHackSolderSide.jpg|thumb|300px|right|LM323K case isolated from ground, and a 25ohm resistor added. This raised the nominal voltage by .2VDC.]] 
A 12 ohm resistor will nominally raise the LM323K voltage output by .1 VDC. 
A 24 ohm resistor will nominally raise the LM323K voltage output by .2 VDC. 
 
Example: 
A 4.90V measurement without load before modification is increased as follows... 
*adding a 16.5 ohm resistor resulted in 5.1V. 
*adding a 24.9 ohm resistor resulted in 5.2V. 
 

==== The Conductive Grease Hack ====
[[What is a "Hack"?]]
Some techs will recommend the use of conductive grease to improve conductivity at a connector. While some techs will "swear '''by''' the stuff", other techs will "swear '''at''' the stuff", and as such, this is not considered a best practice. The grease can extend the life of new header pins, and protect against hostile environments that would cause corrosion. However, when used on header pins that are already damaged, grease can only slow further deterioration. Worse, the heat in the connector will turn the grease to gunk. If you find a flaky connector with gunk in it, you've been "greased" and you will want to re-pin it.

Damaged/burnt connectors should always be [http://www.pinwiki.com/wiki/index.php?title=General#Electrical_Tools replaced]. [http://http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod Dow Corning #4] grease can't help them.

On the other hand [http://http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod DC#4] Electrical Insulating Compound Grease does a superior job reducing friction and corrosion on contacts and that would be considered a net benefit to any game. JRR's shop and others have also found a decrease in the temperature of power contacts using [http://http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod DC#4] along with reduced resistance which should increase the life of the connector. This product is also good to use on EM pins for the interconnect plugs/sockets as it reduces friction and improves conductivity.

Note that [http://http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod DC#4] is stable from -57C to 204C (-70F to 399F). If your game has contacts at the high end of those temperatures then certainly, the [http://en.wikipedia.org/wiki/Magic_smoke smoke] would be getting out...

If other products are used, investigate carefully to ensure they are a proper dielectric grease suitable for high temperature applications. There is a time and place to use this type of product, mostly as a preventative measure on newly replaced contact surfaces. Applying it after the plating has burned off is a questionable practice and no substitute for proper connector replacement.

===Check fuses F114 and F115 message===
[[File:CheckFusesF114andF115.jpg|thumb|300px|left|Check Fuses F114 and F115 Message]]
This message is sometimes displayed when the game boots and a game cannot be started. Most of the time, F114/F115 will be found to be just fine.

The game issues this message because it cannot read the switch matrix normally. The crafty designers at Williams inserted an “always closed“ switch into the matrix as switch 24. Switch 24 isn’t a switch at all, but instead provides the game software with a “known closed” switch matrix return. Switch 24 is actually a diode across column 2, row 4 of the switch matrix and is located on the coin door interface board which itself is located just inside the cabinet on the left wall.

Since the WPC switch matrix circuitry on the MPU uses 12V to determine switch state, the game assumes that the 12VDC power has been interrupted. F114/F115 fuse the 12V generation circuit; F114 on the AC side of BR1; F115 on the DC side of BR1. Hence, the game assumes that one of these fuses is blown and the message is displayed.
 
'''Diagnosing the problem'''

Start by checking DC voltage at TP3. You should see about 12VDC. If not, follow these steps.

#Actually check fuses F114 and F115 using the procedure [[General#Testing_fuses| here]]. If a blown fuse is found, replace it. If F114 immediately blows again, then BR1 is probably shorted. Skip to the paragraph below to test the bridge.
#Check LED6. If not lit (indicating the absence of 18V at TP8), then suspect BR1 or the filter caps for BR1, C6 and C7. If BR1 had failed shorted or if C6 or C7 where shorted (rare) then you would expect to see F114 blown. BR1 can be tested using the procedure below.
#Check LED1. If not lit (indicating the absence of “digital” 12V at TP3, then test D1 and D2 (both 1N4004 diodes that can be tested with the game off or board removed using the standard "diode check" on your DMM).
#If D1/D2 test good, then check continuity from pin 2 of the 7812 voltage regulator at Q2 to J114, pin 5. This verifies the path to ground. If no continuity, check C2 - it may have leaked and corroded the traces beneath it. If so, replace C2 and repair broken traces.
#Next, check continuity from pin 3 of the 7812 to J114, pin 2. This verifies the path through F115 to the 12V power header at J114. If no continuity, check C2 - it may have leaked and corroded the traces beneath it. If so, replace C2 and repair broken traces.
#If this all checks out, yet 12VDC is still not at TP3, then suspect the 7812 voltage regulator at Q2. Q2 is in a TO-220 package (like a TIP-102) and has a small heat sink attached.

'''Alternate Problem Determination Method: Test Power Across the Driver Board'''

[[File:WPC12VRegulatedCircuit.png|center|(The regulated 12VDC circuit, diagram by by Sascha Voksuil aka Zaza)]] 
The diagram above shows the simple path for the 12VDC power regulation circuit. Power may be tested across the circuit, as follows.
#Turn the game on.
#Set your meter to DC volts. If your meter isn't an auto-ranging meter, expect to see less than 20VDC.
#Clip the black lead of your DMM to game ground, or tuck it under the backbox ground braid.
#Probe TP8 with the red lead of your DMM. It should measure about 18VDC. If not, suspect F114.
#Probe the banded side of D1. It should measure about 18 minus .5 to .7 volts, (the typical voltage drop across this kind of diode), or about 17.4VDC. If not, suspect D1.
#Probe the banded side of D2. It should measure about 17.4 minus .5 to .7 volts (again), or about 16.8VDC. If not, suspect D2.
#Probe the top leg of the 7812. It should measure about 16.8V. If not, suspect the trace between D2 and the 7812 or a fractured solder joint at the 7812.
#Probe the bottom leg of the 7812. It should measure about 12VDC since the job of this regulator is to produce 12VDC. If not, suspect the 7812 regulator.
#Probe the right side of fuse F115. It should measure about 12VDC. If not, suspect the trace between the lower leg of the 7812 and fuse F115. In particular, suspect that C2 has leaked and corroded the trace carrying the 12VDC. See: "Leaky Capacitor C2 corrodes trace", below.
#Probe the left side of fuse F115. Again it should measure about 12VDC. If not, suspect F115 is blown or the fuse block has a poor mechanical connection to the fuse or to the PCB.
#Finally, probe pin 2 of J114. It should read about 12VDC. If not, suspect the trace from fuse F115, the connection of the F115 fuse block to the PCB, or a fractured pin at J114.

The only circuit path remaining to test is the path to the ground pin of J114 (pins 5 and 7) from the 7812. This is easily accomplished with power off.

#Set your DMM to continuity and "buzz" between the tab of the 7812 to J114, pin 5 and 7. If no continuity, suspect a fractured solder joint at the center pin of the 7812, or corrosion under C2 that has compromised the trace.

'''Short on the MPU causing F115 to blow'''

There is one more way for the 12VDC power to be lost and for F115 to blow. A shorted IC on the MPU that uses 12VDC can cause F115 to blow. To help isolate the problem to the MPU, replace F115, disconnect power going to the MPU at J210, and turn power to the game on. If the fuse does not blow, the problem is almost definitely on the MPU board. Any of the LM339s (theoretically) or the ULN2803 (definitely) can fail and short 12V to ground, causing F115 to blow.

'''Leaky Capacitor C2 corrodes trace'''

[[File:WPCFailed12VRCircuit.jpg|thumb|300px|left|Filter capacitor C2 (removed), leaking it's corrosive electrolytic contents, eating through traces]]
[[File:WPC12VFilterCapLeakDamage.jpg|thumb|300px|right|Filter capacitor C2 (removed), showing damage caused by a leaky cap.]]
 
Yet one more way for the 12VDC regulated power to be lost is shown in the picture at left. In the picture, the electrolytic cap at C2 has failed and leaked corrosive electrolytic contents onto the board. The lower trace from Q2 (7812 voltage regulator) to C2 (+ side), that goes on to connect to F115 on the solder side of the board, has been eaten away, no longer providing a path for the regulated 12VDC power. Corrective action here is the same as alkaline damage abatement.

Shown on the right is another shot of the damage caused by a leaky cap at C2. This one resulted in reducing the 12V power to about half of spec. 

[[File:WPC12VCorrosion.jpg|thumb|300px|right|Corroded parts in the 12V/Zero Cross circuitry]]
The corrosion resulting from a leaky cap at C2 can be quite extensive. Often, the parts immediately left of C2 are damaged and must be replaced. The part list is as follows, to be installed left to right:
*R206 - 27K ohm
*R198 - 10K ohm
*R199 - 1K ohm
*C1     - .001uf ceramic (or 1000pf, marked 102)
*R204 - 270 ohm
*C12   - .001uf ceramic (or 1000pf, marked 102)
*R205 - 270 ohm
*C3 - .33uf ceramic (not shown, located behind heat sink)
*D2 - 1N4004 (not shown, located behind heat sink)
 

[[File:C2MicroFracture.jpg |thumb|300px|left|This clearly etched trace caused the loss of 12VDC]] 
Any fracture in the trace beneath the capacitor can cause a loss of 12VDC. The image at left was taken from a FishTales Power/Driver board.
 

If TP3 does, in fact, have 12VDC present, then we need to dig deeper.

#First check for 12VDC on the CPU board to ensure that the 12V is getting to the board via the 2 (and possibly 4 if your game has a “Z-Connector”) connectors that carry the 12VDC. An easy place to measure 12VDC on the CPU is at pin 10 of the ULN2803 (U20). Pin 10 is on the bottom row of pins, furthest left. Note that this connection (and also the 12VDC connection to pin 3 of the LM339s) is not shown on the schematic.
#If the CPU is receiving 12VDC, and you still have the “Check fuses F114 and F115” message, then the problem lies within the CPUs switch matrix logic circuitry.
#Prime candidates for CPU switch matrix failure are U20 (a ULN2803), the two LM339s at U18 and U19, the 74LS374 at U14, and the 74LS240 at U13. All of these ICs are in the “corrosion zone” caused by leaky alkaline batteries. If your CPU exhibits the “blue/green fuzzies”, address the alkaline damage first.
#Testing the 74LSXXX ICs is simple using the procedure [[General#Testing_an_integrated_circuit| here]].
#If coil power, flasher power, or even lamp power was somehow shorted to the switch matrix, there is a near 100% probability that the ULN2803 at U20 has been damaged. There is no good way to test the ULN2803 other than using a logic probe with the game powered on. Both the input side and the output side of the ULN2803 should be toggling between logic 0 and logic 1. If not, socket and replace the ULN2803.

[[File:TestingBridgeRectifier.jpg|300px|thumb|right|Testing a Bridge Rectifier in circuit]]
'''Testing a bridge rectifier is simple.'''
#Place your DMM into "diode test".
#Put the black lead of your DMM on the "oddball" lead of the bridge rectifier. This will be the lead that isn't oriented the same as the others (as with the "spade" type of bridge) or the lead that prevents the four legs from forming a square (as with the "wire lead" type of bridge). This will also be the DC positive lead of the bridge.
#Place the red lead of the DMM on each of the adjacent legs, one at a time.
#A reading nominally between .5 and .7 should be seen (this represents the voltage drop across the bridge's internal diodes).
#Now place the red lead of the DMM on the lead opposite of the "oddball" lead, or the DC negative lead of the bridge.
#Place the black lead of the DMM on each of the adjacent legs, one at a time.
#Again, a nominal reading between .5 and .7 should be seen.

Readings outside of these ranges indicate a failed or failing bridge. Note that these readings are not "hard and fast". For instance, a reading of .462 is probably acceptable. We are looking for an "open" or a "short". Note also that this test is not conducted "under load" and it is possible for the bridge to test "good" when it will in fact fail under load (this is also true when testing diodes, transistors, etc).
 

'''Testing BR1 "InSitu"'''

It is possible to test BR1 while the power/driver board is still installed in the game. Thanks to PinSider "Zaza" for the procedure and animation.
#Power the game off
#Ensure fuse F114 is good
#Remove connector J101 on the right side of the power/driver board
#Set your DMM to "diode check"
#Probe as indicated in the animated gif pictured below

[[File:TestingBR1InSitu.gif|Testing BR1 "InSitu".]] 

[[File:Wpc-br.jpg|300px|thumb|left|The heat sink covering BR1 and BR2 on a WPC-board]] 
Take special care when replacing a bridge rectifier. It is easy to lift the traces of the plated through holes when removing these. After removing the heat sink, cut the old bridge rectifier off of the board close to the top leaving as much of the lug as possible. Then add a small amount of solder to the connection on the solder side to improve heat transfer. Finally apply the iron to the solder side to heat the joint and remove the remaining lug with small pliers.

When replacing the new bridge rectifier you should remove the old thermal compound and apply a new thin layer. The old compound can be removed with a little rubbing alcohol. Apply the thermal compound to the top of the bridge rectifiers and reattach the heat sink with the screws [[#Failed_Bridge_Rectifier | (see above)]]. It is much easier to replace the heat sink before resoldering the new bridge rectifier. Make sure that the heatsink is sitting flush with the tops of the bridge rectifiers and that you leave about a 5/8" gap between the bridge rectifier and the board to improve air flow.

Splitting the heat sink between BR1 and BR2 was at one time thought to improve reliability. This is no longer considered a best practice and is not recommended. 

[[File:Wps-diodes.jpg|300px|thumb|left|Diodes replaced BR1 and BR2 on WPC-95 boards]] 
In WPC-95 games, BR1 and BR2 were replaced by a series of diodes. D11-D14 replaced BR1. D7-D10 replaced BR2. These are much less prone to failure. Still, they do fail on occasion. If one or more fail, it's best to replace all four in the "gang". These diodes were originally 6A2 diodes. Replace them with 6A4 diodes (6 amp 200V vs 6 amp 400V). See the "Check Fuses F106 and F101" section below for the equivalent WPC-95 message.
 

===Check Fuses F115 and F116, J112 and Opto 12V Supply Message===
[[File:WPC_Check_F115_F116.JPG|thumb|300px|left|Check Fuses F115 and F116 message displayed on Demo Man]]
[[File:CheckFusesF115F116J112Message.jpg|thumb|300px|right|The same message displayed on I500]] 
Similar to the "Check Fuses F114 and F115" above, games like Demolition Man will display this message at power up if the trough optos are seen as closed (remember, the opto switch open/closed logic is inverted). Debug this issue by checking the 12v connectors at the lower left corner of the driver board and the connectors on the trough opto transmitter and receiver board.
 

===WPC-95 Check Fuses F106 and F101 Message===
[[File:CheckFuses106And101.jpg|thumb|300px|left|Check Fuses F106 and F101 Message]] 
If a WPC-95 game detects loss of 12VDC power by not seeing switch 24 as closed, "Check Fuses F106 and F101" will be displayed at power up. This could obviously mean that F101 and/or F106 are blown. It might also indicate failure of the LM7812 12VDC regulator at Q2 in which case LED102 will be on and LED100 will be off or, failure of one or more of the 6A2 diodes that rectify the AC power (D11-D14). In the latter case, both LED102 and LED100 will be off. Use these LED indicators, as well as testing for 18VDC at TP102 and 12VDC at TP100 to guide your repairs.
 

===Line Voltage Detection - LED2 & LED3===

LED2 and LED3 on the Power Driver Board are indicators for the line voltage detection circuit. On on-board comparator circuit uses +5V and +18V to check the line voltage. The comparator consists of a resistor voltage divider and an LM339 comparator.

The following table shows how to interpret the LED states. Note that other problems with the +18V or +5V supply could cause a high or low line voltage indication.

Line Voltage Indicator Chart
{| class="wikitable"
!LED2
!LED3
!Voltage
|-
|<center>On</center> || <center>Off</center> || <center>OK</center>
|-
|<center>Off</center> || <center>Off</center> || <center>High</center>
|-
|<center>On</center> || <center>On</center> || <center>Low</center>
|}

===Exploding or Damaged 15,000uf Capacitor at C11 (C10 on WPC-95)===

A smoking, domed, or in the worst case exploded filter capacitor at C11 can result from cross connecting J124 and J128 on the power/driver board. Doing so creates a circuit that routes 70VDC coil power through C11 which is typically rated at 25VDC and is meant to filter the 20VDC flash lamp circuit. This is made possible since J124 and J128 are identically implemented. Both are 5 pins wide, both keyed at pin 4. This is possible on WhiteWater, Dr. Who and Bram Stokers Dracula at least, and may also be possible on other games. It is possible on any WPC or WPC-S game that uses J124, whether or not J128 is used.

[[File:J106ConnectedToJ132BlowsC11.jpg|thumb|left|300px| J106 flash lamp power connector with red/white wire incorrectly connected to J132 on a Gilligan's Island, perhaps by Gilligan himself. Image courtesy of FB "Pinball Repair Group II" member Criss King]] 
Another very effective way to blow C11 is to connect the flash lamp power connector at J106 to high power coil grounding circuits at J132. The connectors are the same width and keyed identically. This connects 72VDC coil power to the 20VDC flash lamp power which is filtered by C11, a 15,000uf/25V capacitor, with the same results as mentioned above. 

Other possible causes for a damaged C11 are a shorted flipper coil diode, a shorted drive transistor on the FlipTronics board, or installing backbox ribbon connectors incorrectly (bottom female housing row to top male header row).

[[File:J124J128ErrorBlockingDiode.jpg|thumb|left|300px| A 1N4004 blocking diode installed in series with R224. Image courtesy of John Wart Jr.]] 
An effective method of preventing damage to C11 in the event that one of the conditions above is met, is to install a blocking diode in series with the large sand resistor at R224. Install a 1N4004 (for example) with the banded side facing the PCB as pictured at left.
 

===WPC and WPC-S Games With No Solenoid, Flasher or Feature Lamps, A Blanking Signal Issue===
[[File:SeveredBlankingSignal.jpg|300px|thumb|left|The trace emanating to the right from pin 1 in this picture has been severed by corrosion as it passes between pins 19 and 20.]] 
The blanking signal from the MPU is connected to pin 1 of each of the 74LS374 buffers (U1 thru U5 and U18) that drive general illumination, flash lamps, coils, and feature lamps. Normally, this signal is pulled low by the MPU board, indicating that no faults have been detected and the system is running as expected. Without a low blanking signal, none of the game features implemented by the driver board will be enabled.
[[File:WPCBlankingTracesAnnotated.jpg|300px|thumb|right|Blanking signal "test points" on the WPC-089 MPU board]]
As these games begin to age, the 12V filter cap located at C2 begins to leak it's corrosive contents onto the PCB. As noted in the section titled "[https://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Check_fuses_F114_and_F115_message Check Fuses F114 and F115 Message]", the corrosion often damages adjacent parts and sometimes invades the solder mask to sever critical signals, like the blanking signal or even data signals. If continuity can not be "buzzed" between the blanking and data pins of U1 and U2, and C2 has been leaking, then there is a good chance that the signal trace has been severed under or around U1. Corrosion seems to accumulate under the chip and between the legs frequently. To address this issue, cleanly remove the chip, clean up the corrosion, rebuild traces as necessary, install a socket, and replace the 74LS374 if necessary.

The blanking signal on the MPU originates at the ASIC (pin 34). It is inverted 3 times by U21 and U5 before being distributed to J204, J211, J202 and the blanking LED. J211 connects via 34 pin ribbon to the power/driver board. If the blanking signal fails to reach J211 pin 31, the same behavior as described above will occur. A DMM set to continuity mode should indicate a connection between U5 pin 8 and J211 pin 31. Sometimes, the signal is interrupted by a damaged or poorly formed via, shown in the picture at right.
 

===WPC Games With No Flashers===
[[file:WPC-driver-20vdc-circuit.png|400px|thumb|right|Schematics for driver board secondary unregulated 20VDC circuit]]On WPC-89 games, if no flashers are working, and if the game uses a motor and that also isn't working (such as the cannon on T2), the problem might be somewhere along the secondary unregulated 12V path on the WPC driver board. It could be a connector issue, blown fuse, bridge failure, or detached bridge eyelets on the PCB.

# First, check the interlock switch (if applicable on your game) to make sure that it isn't disabling the voltage.
# On the driver board, check LED5. This is lit if 20VDC is present, if not, 20VDC (and 12VDC for the flashers/motors) is missing (or too low). If it is lit, then proceed to check R224 (10W resistor) for the correct resistor value (0.12 Ohms) and continuity for the legs.
# On the driver board, if LED5 is off, check fuse F111.
# Check TP7 to see what the reading for 20VDC actually is. If the reading is near zero, then:
# Check connector J102 for 20VAC on pins 1 and 3. If about 20VAC is present, the issue is likely on the driver board.
# Check the BR4 bridge rectifier using [[General#Testing_a_Bridge_Rectifier|this guide]]. If the bridge is bad, replace it. If not, test for continuity:
# Test for continuity between the bridge legs and nearby connection points.
## For the negative leg, test to the negative leg of C11. Also check for continuity to J115 pin 1 or any pins on J103.
## For the positive leg, test to the positive leg of C11 and the leg of R224 (10W resistor).
## For the AC inputs, check the top/upper AC leg to J102 pin 1, and the lower/bottom leg to J102 pin 3.
# If there is a loss of continuity on one or more legs, it is possible that the eyelets separated from the traces. Only the positive leg has a trace on the back side, which helps anchor the eyelet, while the other three legs are more prone to separation since there are no traces on the back side to help anchor them. They can separate due to fatigue or prior repair work.
## Remove BR4. The easiest approach may be to clip off the bridge and then desolder each wire leg individually.
## There are two possible approaches--adding a wire stich on the top side of the PCB, or adding jumper wires on the back side of the PCB.
##* To stitch: If possible, scrape a little bit of the mask off the affected traces, then add a wire stitch to the top side of the PCB from the exposed trace to the leg hole. Once done, install the bridge and solder the legs.
##* [[file:WPC-driver-BR4-jumpers.jpg|thumb|right|400px|Jumper wire diagram for BR4 on driver board]]Or to add jumpers: just install and solder the bridge, then add jumper wires for the appropriate failed eyelets using 18 gauge wire.
##*# For the negative leg, jumper it to the negative leg of C11.
##*# For the positive leg, jumper it to the positive leg of C11.
##*# For the bottom/lower AC leg, jumper it to J104 or J105 pin 4.
##*# For the top/upper AC leg, jumper it to J104 or J105 pin 5.
# If BR4 tests good, BR4 has continuity, LED5 is lit, TP7 has 20VDC, check R224 for 20VDC on one side and 12VDC on the other. Check for 12VDC at J107 pin 5 & 6, J106 pin 5, and J108 pin 3. Check for connector issues and cold/cracked solder joints at those pins.
 

===Solenoid, Flasher, and Motor problems===

Flashers, solenoids, and motors in WPC games are turned on via transistors on the driver board and in some games, transistors on the [[Williams_WPC#Auxiliary_8-Driver_Board_.28A-16100.29| Auxiliary 8 Driver Board]].

Before proceeding to diagnose solenoid or flasher problems, see this section: [[General#How_coils.2C_flashers.2C_and_motors_are_turned_on| How Coils, Flashers, and Motors are Turned On]].

The general logic for providing a path to ground for a coil, solenoid, flasher or motor (subsequently, we'll refer to coils only, but this is true for coils, flashers, and motors) via the driver board is as follows. Operation of the [[Williams_WPC#Auxiliary_8-Driver_Board_.28A-16100.29| Auxiliary 8 Driver Board]] is similar but control is accomplished via the long ribbon cable from the MPU to the 8-Driver Board.

#The MPU places the appropriate bit pattern on the data bus to control a "bank" of 8 transistor circuits. The data bus is extended to the power/driver board via the interboard ribbon cable.
#The MPU/ASIC "clocks" the appropriate [http://www.datasheetcatalog.org/datasheets/90/375622_DS.pdf 74LS374], an "octal latch" on the power/driver board, to latch data on the data bus into the 74LS374.
#The outputs of the 74LS374 turn on a 2N5401 transistor.
#The output of the 2N5401 turns on a TIP-102 transistor.
#The TIP-102 transistor either provides the path to ground for the waiting coil power or, for higher powered coils, turns on a TIP-36c transistor which provides the path to ground.

The reason that (up to) 3 transistors are used in the circuit is to "amplify" the power. A 2N5401 transistor can handle a comparatively small amount of current. A TIP-102 transistor can handle a much greater current load. The TIP-36c in 8 of the WPC power/driver board circuits can handle an even greater current load.

Note: With the exception of flipper coils and coils driven through the "special solenoid" drivers, diodes used to [http://en.wikipedia.org/wiki/Snubber snub] the reverse current caused by the collapse of the coil's electromagnetic field, are located on the driver board. High power and low power playfield and backbox coils (solenoids 1 through 16) should not have a diode on them. This convention eases the tech's job in that he/she doesn't need to be careful with diode orientation on the coil.

Note: Coils driven by a Flash Lamp drive (solenoids 17 through 20) or by special solenoid drives (solenoids 21 through 28) require a "tie back diode" connection. When a flash lamp drive is used, a diode must be added to the circuitry, as was done with the Terminator 2 single drop target for example, as the power/driver board doesn't include this diode. When a special solenoid drive is used, a connection from the coil, back to the appropriate pin on the driver board which leads to the on-board tie back diode, must be made. See the section [[#Blown / Failing Q20 Transistor on the Driver Board and the Tieback Diode|Blown / Failing Q20 Transistor on the Driver Board and the Tieback Diode]] below for more information

====Weak Trough Kicker====
[[File:WPCTroughKickoutMechanismCropped.jpg|300px|thumb|left|A clearly "gunked up" mechanism. Image courtesy of PinSider Gorgar666.]]
For games with the traditional "above playfield ball trough" (pre-WPC95), a weak kickout is often caused by accumulated congealed lubrication on the pivot point of the kickout mechanism as pictured here. Simply removing the mechanism, cleaning it, and relubricating with a drop of teflon lube will resolve the issue.
 

====Transistor "Quick Check"====
[[File:QuickTransistorCheck.jpg|300px|thumb|left|Testing TIP-102s quickly on a WPC power/driver board.]]
A quick check of the TIP-102s on the driver board can save time. Set your DMM to "continuity check". Place the black lead of your DMM on board ground. Touch the tab of each TIP-102. If the meter indicates continuity, then that TIP-102 is shorted. This quick test works only with TIP-102s and NOT with TIP-36c transistors since the tab of a TIP-36c is connected differently.

For WPC power/driver boards, the lamp matrix TIP-107 transistors can also be checked using this method if the black probe is touched to the 18V test point on the right edge of the board.

[[File:YT.png]] A video demonstrating this technique on a Data East MPU can be viewed [https://youtu.be/VXiS04-yY58 here].
 

===="Help" Info Provided by WPC Games====
[[File:WPCHelpSequence.jpg|300px|thumb|right|WPC games provide help during coil test.]] 
During coil test, pressing the credit button provides a bit of information helpful in debugging your game.

With coil test "stopped", pressing the credit button sequences through the following information.
*Solenoid power and ground (drive) wire colors
*Solenoid power and ground (drive) connections
*The fuse that protects the circuit
*The sequence of cascading transistors that provide a path to ground for the solenoid. In the picture at right, Q82 (TIP-36), Q81 (TIP-102), and Q71 (2N5401) provide the path to ground.
 

====Failed TIP-36c====
[[File:WPCSolenoidGroundTraceBlownAndRepairedAnnotated.jpg|300px|thumb|left|A blown trace (inside the yellow circle) caused by a shorted TIP-36c transistor. The damage has been nicely repaired with a solid core jumper, soldered to through hole components versus "tack soldered" to the trace, making a stronger solder joint. Note: solder flux visible on replaced TIP-102 and TIP-36c later removed with isopropyl alcohol.]] 
When replacing shorted transistors, examine the traces connected to the transistor for further damage. In the picture at left, a shorted TIP-36c was replaced. During test, the first time the TIP-36c was called upon to provide a path to ground for the associated coil, the TIP-36c failed shorted again. This was caused by the blown trace. 

====Blown / Failing Q20 Transistor on the Driver Board and the Tieback Diode====
[[Image:Terminator2DiodeTiebackWireAnnotated.jpg|300px|thumb|left|The violet/orange "diode tieback" wire, attached to the power side of the drop target reset coil in Terminator 2. Photo Credit: John Wart Jr.]]
[[Image:Terminator2-Q20ViolentExposionCropped.jpg |300px|thumb|right|Q20, with a major malfunction, due to the diode tieback wire connection being missing. Photo Credit: John Wart Jr.]] 

Several games (Star Trek the Next Generation, Funhouse, Terminator 2, Indiana Jones, and The Addams Family to name a few), employ the use of a "diode tieback" system on a specific coil or motor. A diode tieback is the use of a clamping diode between the drive transistor ground and the voltage source to accommodate the reverse voltage spike induced when a coil's magnetic field collapses. While Williams moved most clamping diodes to the power/driver board, the flashlamp circuits (drives 17 through 20) don't include a clamping diode. Flash lamps don't create the same reverse voltage spike and hence, don't require a clamping diode. A tieback diode must be added to the game wiring when one of these flashlamp drives are used to turn on a coil or a motor.

The "Special Solenoid" drive circuits (drives 21 through 28) do include a clamping diode but that diode isn't connected to a voltage source. Presumably, Williams did this to provide flexibility in voltage levels used to drive a special solenoid. When one of the special solenoid drives is used to drive a coil or motor, a connection must be made from the power side of the coil or motor back to the associated power/driver board clamping diode via the appropriate header pin at connectors J122 through J126.

If the tieback diode connection is lost, the associated drive transistor on the driver board (as pictured on the right) WILL be damaged. Also, the associated coil is likely to be held on continuously and melt. In the example pictured at left from a Terminator 2, the diode tieback wire is the thin violet/orange wire. It connects from the coil power side on the drop target assembly coil lug to J122 pin 9 on the driver board and then to clamping diode D5. If the solder connection at the coil lug is solid, suspect the wire connection at the J122 IDC connector. Repinning this connection with a good quality crimp-on Trifurcon pin is advised.

The Addams Family uses Q20 for the "Swamp Release" coil, Q22 for the "Bookcase Motor", Q24 for the "Thing Eject Hole", and Q26 for the "Thing Motor", all requiring a tieback diode.

Star Trek: the Next Generation drives the subway diverters via the 8-Driver board in the upper right side of the head. These also require a tieback diode as discussed [http://www.pinwiki.com/wiki/index.php?title=Star_Trek:_The_Next_Generation#Diode_.22Tie_Back.22_missing_causes_8-Driver_Board_transistor_to_fail here].

====Coil Locks On or Flash Lamp Blows at Power On====
One particularly confusing way that a coil locks on or a flasher blows immediately is caused by misplaced connectors on the driver board.

[[File:J124J128J132.png|700px|thumb|left|Williams WPC-089 and WPC-S PowerDriver Board Connectors that are identically keyed.]] 
In the picture at left, it is easy to see that connectors J124, J128, and J132 are all 5 pins, keyed at pin 4.

While the results are game dependent, placing the connector that should be at J124 at either J128 or J132 will cause problems.
 

For instance, on the game '''Black Rose''', placing the connector that should be at J124 at J128 will cause the lower pop bumper to lock on and eventually blow the associated transistor.

'''Analysis'''

J127 is the return for the lower pop among other circuits. By placing the J124 connector at J128, this connects 70V coil power to 20V flashlamp power via PCB trace connections (J124/3 return). The only reason more coils aren't locking on is that the "pin location intersection" of J124 and J127 is only pin 8 (lower pop) and pin 9 (not used, not stuffed).
This "cross wiring" is also placing C11 under stress since it is being fed 70VDC and the cap is rated at either 25 or 35VDC.

[[File:70VatBlackRoseSocket.png|300px|thumb|left|Measuring coil power at a flash lamp socket on Black Rose.]]
[[File:BlackRosePowerDriverBoardCorrectConnections.jpeg |400px|thumb|right|Black Rose Power/Driver board with correct connections shown.]] 
Also on the game '''Black Rose''', placing the connector that should be at J124 at J132 sends 70VDC to a flashlamp socket in the backbox, as pictured at right.

The Black Rose game manual is incorrect in both the coil/flasher listing in the front of the manual and in the section in the back of the manual that details connections.
 

[[File:BlackRoseCorrectedSolenoidListingFrontofManual.jpg|300px|thumb|left|Corrected solenoid table for Black Rose.]]
[[File:BlackRoseCorrectedSolenoidListingBackofManual.jpg|300px|thumb|left|Corrected connection listing for Black Rose.]] 
The two images at left depict corrections to the Black Rose manual.
 

====Coil Locks On====
This is the most prevalent problem observed (versus coil not firing). When a coil locks on, this means that the power that is present at the coil at all times has found a path to ground. Normally, a path to ground is provided via a controlled transistor set on the driver board. In rare cases a frayed wire or a wire with an insulation gap/failure will touch ground and the coil will lock on.

Most of the time, the drive transistor on the driver board has shorted internally and is acting as if it's been turned on. Should this be the case, the following steps will isolate the problem transistor.

#Use the "Solenoid/Flasher Table" at the front of the game manual to identify the likely failed transistor(s).
#Remove the driver board from the game.
#Test the drive transistor (TIP-102 or TIP-36c).

Testing a TIP-102 transistor
#Set the DMM to diode check
#Place the black lead on the center leg
#Place the red lead on each of the flanking legs in turn
#A measurement between .5 and .7 should be displayed
#Readings outside of this range (generally dead shorts) indicate the part has failed.

Testing a TIP-36c transistor 
:[[image:YT.png]] A video showing how to test a TIP-36c can be found [https://www.youtube.com/shorts/KzcPThLxQLs here].
#Set the DMM to diode check
#Place the red lead on the center leg
#Place the black lead on each of the flanking legs in turn
#A measurement between .5 and .7 should be displayed
#Readings outside of this range (generally dead shorts) indicate the part has failed.

If the drive transistor tests failed, remove the part using this [http://www.pinwiki.com/wiki/index.php?title=General#Desoldering_Printed_Circuit_Board_Through_Hole_Components procedure] being very careful with the delicate traces and through holes.

Most of the time, the last transistor in the cascading transistor chain is the only one to have failed. But, it's important to test the upstream transistors before placing the board back into service. If a TIP-102 has been found to have failed, test the upstream associated 2N5401 predriver. If a TIP-36c has been found to have failed, test the upstream associated TIP-102 and 2N5401 predrivers.

[[Image:Terminator2-Q20ViolentExposionCropped.jpg |300px|thumb|left|A failure involving other parts connected to the failed transistor Photo Credit: John Wart Jr.]] Sometimes, additional parts connected to the failed transistor will have been damaged too, as pictured at left. It then becomes necessary to replace those parts, remove carbon (it's a conductor) and to rebuild burned traces as necessary.

When a coil has locked on for an extended period of time, the coil wire insulation heats up, melts, and begins to short together. Left locked on for long enough, the coil becomes a dead short. It's important to test the resistance of the failed coil to ensure that it hasn't been damaged. A resistance measurement less than 2 ohms certainly means that the coil is damaged, but comparing the coil's resistance to other known good coils is the best and easiest test. WARNING: If the coil has become a dead short and remains in circuit, and the game is powered on, the associated driver transistor WILL be damaged. 

====Coil Fails to Work====

Before proceeding, see this section: [[General#How_coils.2C_flashers.2C_and_motors_are_turned_on| How Coils, Flashers, and Motors are Turned On]].

Possible causes for coils failing to fire include:
*The switch associated with the coil is not being sensed by the MPU, and hence the MPU doesn't command the coil to fire.
*The coil doesn't have power
*One/both of the coil wires are not solidly soldered to the solder lug
*The coil winding is open
*The coil power is not finding a path to ground
*Interlock switch is not activating when pressed

=====Associated Switch Failure=====
If the MPU isn't commanding the coil to fire, obviously it won't. For instance, if a slingshot switch isn't being "made" or some other switch matrix problem prevents proper switch sensing, then the MPU won't command the slingshot coil to fire. This type of failure is easy to isolate merely by placing the game in switch test and closing the switch. Also, if during game play, points are scored when the switch closes, clearly the switch is being made. If a coil fires in solenoid test but not in game play, then the root cause is a switch problem versus a coil problem.

=====No Power to the Coil, Coil Wire not Solidly Soldered, or Coil Winding Open=====
Testing for power to the coil is easy.
*Set the DMM to DC volts. If not an auto-ranging meter, expect less than 200VDC.
*Turn the game on.
*Place the black lead on a convenient game ground like the ground braid or side rail.
*Place the red lead on the coil lug with the "fat" wire(s). The fat wire carries power to the coil.
*The appropriate voltage should be read (75VDC for coils, 20VDC for flashers)

If the appropriate voltage is not seen, there are two primary reasons. Either the power circuit fuse has blown or there is a discontinuity in the power wiring from the driver board to the coil. Turn the game off. Remove the associated fuse and "buzz" it with a DMM set to continuity test. While the fuse is out of the board, make sure it's rated at the proper amperage. Generally, WPC coil and flasher circuits are fused with a 3ASB fuse. If the fuses tests good, the next test is to ensure continuity from that fuse to the coil power lug. With the DMM still set to continuity, "buzz" between the fuse and the coil power lug. If continuity isn't proven, the task is then to find the break in continuity between the driver board connector and the coil power lug. Remember that power is "daisy chained" through several coils in the game. That is why some coils will appear to have two power wires soldered to one lug.

If the appropriate voltage is seen, then test for a break in the coil windings. With the game still powered on...

*Place the red lead on the other coil lug.
*Again, the appropriate voltage should be seen.

If the appropriate voltage is not seen, then either the coil winding has a break in it or the winding is not solidly soldered to the coil's solder tabs.

=====Coil Power is Not Finding a Path to Ground=====
The smaller wire attached to one of the coil lugs connects the coil to the driver board. The driver board has a drive transistor allocated for each coil in the game. The smaller wire must have a solid connection back to the driver board. There are two ways to test the path to ground.

#Use a DMM set to continuity to "buzz" the connection of the smaller wire between the coil and the female connector on the driver board. Ensure that the connection of the wire at the IDC connector is solid. If the coil is driven by a TIP-102 transistor, buzzing between the smaller wire on the coil and the transistor tab should show continuity.
#With the game powered on, and a short length of wire stripped on both ends, touch one end of the wire to the ground braid in the head. Touch the other end of the wire BRIEFLY to the tab of the associated TIP-102. If the coil pulls in, then the path to ground has been proven and the failure is likely the TIP-102 itself. NOTE: This test can be performed ONLY when a TIP-102 is the drive transistor. TIP-36c transistors are configured differently. The tab of a TIP-36c is not connected in the same way.

Once the wiring and connector have been verified to be in order, the next step is to test the associated drive transistor. Unlike when a coil locks on and the driver transistor has shorted on, in this case the drive transistor may have failed "open". Test the transistor using the same procedure outlined in the prior section. Replace as necessary.

If the drive transistor tests failed, remove the part using [[General#Desoldering_Printed_Circuit_Board_Through_Hole_Components|this desoldering guide]] being very careful with the delicate traces and through holes.
 

=====High Voltage Interlock Switch Failure=====
On later WPC games (beginning sometime during production of Twilight Zone in 1993), there is a push button switch used for disabling high voltage circuits (20VDC and 50VDC) when the coin door is opened, providing a measure of safety against higher voltage shocks.

Sometimes, this interlock switch can get worn or dirty (or there are problems with the movement of the internal parts), and the switch doesn't always form a closed circuit properly. So, while the coin door is closed, the interlock switch may fail to activate the 20VDC and/or 50VDC circuits.

Note that there is a separate push button switch responsible for reporting to the MPU whether or not the coin door is open in order to display the "high voltage disabled" message. So, if the high voltage interlock switch fails to complete a high voltage circuit, the MPU will have no idea about this failure, and thus not display a notification message.

To test for the issue, turn the game off, and use a digital multimeter in continuity mode across the appropriate switch lugs for the two circuits (20VDC and 50VDC) on the interlock switch. If the lugs are dirty, they may need to be cleaned. If there is black gunk that looks like it may be baked onto the lugs, it may need to be sanded or filed off to reach the bare metal of the switch lug. Once the lugs are clean and the multimeter is attached, then slowly press in the switch button. If a switch closure is not detected, there may be a problem with one of the switch's circuits. If there is only a switch closure at a certain point where the button is only pressed part way, then fails again after being pushed all the way in, there is likely a problem with the internal parts of the switch.

The switch can be opened up and inspected for issues, and possibly cleaned and repaired. Or, it can simply be replaced with an E79-00A momentary switch or E79-30A0 momentary pull-on switch (both are DPDT, 10A, 125/250v).

====Low Coil Voltage====
[[File:WPC-C8.jpg|300px|thumb|left|C8, located near the 50VDC test point, can cause reduced coil power.]] 
Coil power for WPC games is nominally about 70VDC. Very little can reduce this voltage. If the game is delivering significantly less than 70VDC, suspect BR3.

It's also possible for C8 to cause reduced voltage. C8 is a 100uf/150V (sometimes installed as 100uf/100V) capacitor.
 

====Q26 Transistor & Coil Locking On with Rottendog Driver Board====
[[File:Rottendog-wdb089-masking-error.jpg|300px|thumb|left|Masking error on Rotendog WDB089 Rev. 2]]
If the Q26 transistor (and associated coil) keeps locking on with a Rottendog WDB089 driver board, there may be an erroneously exposed trace on the back of the PCB near one of the screw mount notches that is causing a short. It is located at the bottom edge of the board near connector J122. The exposed trace is next to the grounding pad for the screw mount, and excess solder may be bridging them together.

The issue was noticed on a revision 2 board. It is not currently known if other board revisions are affected by the issue.

To address the issue, first remove any excess solder that may be bridging the connection between the exposed trace and the grounding pad. Then, seal the exposed trace with a PCB solder mask material (ie, an overcoat pen would work) or clear nail polish.
 

===Lamp problems===

Lamps (or globes for those of you in the UK) fall into two categories. "General Illumination" and "Controlled Lamps". Your game probably has other lamps which are actually "flashers" that require an 89 or 906 bulb. Flashers are covered elsewhere in this Wiki.

General illumination lamps (GI) provide the ambient lighting for the playfield, backbox, and coin door. These lamps are lit most of the time. The only "controllable" aspect of these lamps is their brightness, which of course, includes off.

Controlled lamps (sometimes called "feature lamps") are under complete CPU control via the 8-by-8 lamp matrix. These lamps illuminate the various "features" of the game such as mode inserts, pop bumper lamps, inlane/outlane insert lamps, etc.

====General Lamp Problems====
[[File:PCBMountLampDivot.jpg|300px|thumb|left|"Divots" in the connection pad of a "twist in" lamp.]] 
WPC and WPC-95 systems employed "lamp boards" to ease the manufacturing process. These lamp board PCBs used "twist in" sockets, each with a 555 lamp. Over time, the pads on these sockets develop "divots" which sometimes results in a poor connection to the twist in socket. This can be easily corrected by removing the lamp board from the game and reflowing the solder on the pads.
 

[[File:WPCPCBLampBoardHeaders.jpg|300px|thumb|left|The solder on these header pins has been reflowed nicely.]] 
Another problem with lamp boards is the header connections. The solder joints at the connection pins often fracture due to connector insertion pressure, heat, fatigue, etc, and due to being a single sided PCB. The fix for this is again to reflow the solder around the header pins.
 

[[File:FracturedSolderJointLampBoard.jpg|300px|thumb|left|Fractured solder joints on this lamp socket caused intermittent operation.]] 
One of the less reliable designs Williams used was to "cantilever" lamp sockets over the end of lamp boards. This was done on a great many games such as Twilight Zone, Judge Dredd, etc. The repeated pressure needed to insert a new lamp into the socket causes the solder to fracture. This can be corrected easily by simply reflowing the solder at the joint. 

However in some instances, the socket has become damaged beyond the simple repair of just soldering the legs to the lamp board. Replacement sockets are available from most pinball parts vendors.
 

If after repairing the lamp board divots, reflowing the header connectors, the lamp socket is still completely intact, (the contacts do break off of the socket sometimes), and the bulb is good, suspect that the diode associated with the particular lamp may be bad.
 

====General Illumination Problems====

'''Background'''

[[File:WPCGIConnectors.jpg|thumb|300px|left|WPC/WPC-S General Illumination Connectors J119 (cabinet), J120 and J121 (repinned)]]
[[File:WPCJ115NewWireColors.jpg|thumb|300px|right|WPC/WPC-S General Illumination Connector J115, with the "2nd Generation" transformer secondary general illumination wire colors. Image courtesy of Chuck Sanderson.]] 
The WPC power/driver board provides 5 GI circuits under CPU "brightness control". The WPC-95 power/driver board provides 3 GI circuits under CPU "brightness" control and 2 circuits that are always powered. Those two circuits are always connected to the backbox lamps. 

GI power is provided by the transformer in the form of 6.3VAC at power/driver board connector J115. Although there are five pairs of wires, they are all connected together at the transformer. One side of the AC GI circuit on the power/driver board is fused by F106 through F110 which are all 5ASB fuses. This side runs to the GI lamps, and carries 6.3VAC to the backbox, playfield, and coin door via power driver board connectors J120, J121, and J119 respectively. J119 is a 3-pin header that is always connected to the coin door lamps. J120 and J121 are electrically and physically identical (keyed at pin 4) and therefore can be connected to either the female playfield GI connector or the female backbox GI connector without care. The other side of the GI AC feed is connected to ground. 

The GI power is controlled by a triac in the return line from the playfield. When these triacs are off, no current passes and the lamps are off. When the triac is turned on, the GI lamps glow. The triac is a slightly special part - it must be a "four sector" triac. This means that it can switch both positive and negative sides of the AC cycle with only a positive signal. 

Each triac is switched on/off by a 2N5401 transistor which is controlled by U1, a 74LS374, an octal D-Type Flip-Flop with three state outputs (a fancy way of saying that the device is an 8-bit data buffer). 

U1 is "clocked" by the ASIC via the /TRIAC signal. If you have AC power present at J115, and no GI at all, it's possible that the /TRIAC signal is not getting through to U1. A logic probe applied to pin 11 of U1 will prove that the signal is getting through. If the signal is not present, try (after turning the power OFF)...
*Pressing firmly on the MPU ASIC to "reseat" it.
*"Reseating" the ribbon cable between the MPU and the Power/Driver board.
*Use your logic probe to track the signal from pin 66 of the ASIC, across the MPU to the MPU connector, across the ribbon cable, then across the Power/Driver board to U1 pin 11.

The CPU can dim the GI by switching on the GI for only parts of the AC waveform. To do this, the CPU uses a zero crossing signal on the driver board keyed from the AC that feeds the 5V circuit, diodes D3 and D38, and the LM339 at U6.

[[image:YT.png]] A video further describing operation of the General Illumination circuit can be found [https://youtu.be/RcAHeP_iTBU here].
 

[[File:WPCJ115.jpg|thumb|300px|left|WPC General Illumination Connector J115 (AC power in). Note wire colors, beginning on the bottom with a yellow/white, then three (looped) yellow, then three (looped) yellow/white.]]
[[File:WPC-GI-RepinAlternative.jpg ‎|thumb|300px|right|WPC General Illumination Connector J115 "dongle" that provides an alternative to looping wires. Two wires are crimped into 4 of the 7 .093 pins, which is much easier than crimping two wires into a .156 crimp pin. Note wire colors, with red connected to yellow/white wires and black connected to yellow wires through the connector. The center pin is used for the "ground reference". This method is identical to the method Williams used in late model WPC games, but this connector is added and moved closer to the Power/Driver board.]] 
Wire colors to J115 during the early WPC games were always yellow (AC) and yellow-white (AC return) as pictured at left. Pin 1 of J115 provides the "ground reference". Later WPC games used different wire colors at J115 and instead of "looping" power through the connector at J115, connected two wires to the same pin at the 9-pin connector between the transformer secondary and J115 (note picture at right that implements the same concept for earlier model games.

The colored wire connections for this era of WPC game are yel-wht connected to pin 1, yellow connected to pins 2-6, yel-wht connected to pins 7,8, 10, 11, & 12. Pin 9 is the key.
 

J119 is always keyed at pin 2, with a white-Violet wire at pin 1 and a Violet wire at pin 3

J120 and J121 are 11 pin connectors. Wire color/positions (when used) are identical for all WPC games and are shown in the table.

{| class="wikitable"
!<center> Pin </center>
! Wire color at J120/J121    
|-
|<center>1</center> ||  Brown
|-
|<center>2</center> ||  Orange
|-
|<center>3</center> ||  Yellow (yellow)
|-
|<center>4</center> ||  Key
|-
|<center>5</center> ||  Green
|-
|<center>6</center> ||  Violet
|-
|<center>7</center> ||  White-Brown
|-
|<center>8</center> ||  White-Orange
|-
|<center>9</center> ||  White-Yellow (yellow)
|-
|<center>10</center> ||  White-Green
|-
|<center>11</center> ||  White-Violet
|}

'''Common GI Problem Causes''' (listed by probability/ease of testing and correction)

'''GI Bulbs Not Lighting'''

Let's start by determining if the problem is "off board", i.e. not on your power/driver board, or "on board".

#Take note of the wire color of the GI string that is not working.
#Set your DMM to AC voltage. If your DMM is not an "auto-ranging" model, expect to measure about 7 volts AC.
#Turn the game on.
#Insert one probe of your DMM (either one) into the rear of the female connector position with the same wire color as noted earlier. Make sure you make contact with the conductor.
#Insert the other probe into the rear of the female connector with the white wire that has the same color "tracer" as the color noted earlier.
#You should be measuring 6 to 7 VAC.
#If there is voltage at the connector, then the problem is "off board".
#If there is no voltage at the connector, then the problem is "on board".

'''Off board GI problems'''

#'''All lamps blown.''' Don't laugh. Just for giggles, put a known working lamp into one of the lamp sockets of the suspected GI string. I've seen it more than once. Usually the result of operators never changing a bulb, or somehow connecting higher voltage to the circuit.
#'''"Open" in GI wiring.''' The GI wires leading from J120/J121 may be cut/broken between the connector and the GI lamp sockets. Remove both of the female connectors at J120/J121. Use your DMM to check continuity between the lamp socket and the appropriate wire/pin at J120/J121.

'''On board GI problems'''

#'''Blown fuses.''' This is also the easiest problem to fix. Check each GI fuse following this [[General#Testing_fuses| procedure]]. Don't trust your eyes.
<ol start="2">
<li>'''Loss of "Cross Board" Connectivity.''' This problem is generally caused by burned header pins, traces, or in some cases, poor prior repairs. Use the following table to check cross board connectivity with J120/J121 as your target. Buzz between the pins/parts shown in the table or use the diagrams below.
{| class="wikitable"
!<center> GI Connector/pin </center>
! Connects to 
! ...and to fuse 
! associated circuit wire color 
|-
|<center>J120-1</center> ||  Triac Q18 tab    ||  ||  Brown
|-
|<center>J120-2</center> ||  Triac Q10 tab  ||   ||  Orange
|-
|<center>J120-3</center> ||  Triac Q14 tab  ||   ||  Yellow (yellow)
|-
|<center>J120-4</center> ||  Key pin  ||  ||  
|-
|<center>J120-5</center> ||  Triac Q16 tab  ||   ||  Green
|-
|<center>J120-6</center> ||  Triac Q12 tab  ||  ||  Violet
|-
|<center>J120-7</center> ||  J115-3  || <center> F110 </center> ||  White-Brown
|-
|<center>J120-8</center> ||  J115-4  || <center> F109 </center> ||  White-Orange
|-
|<center>J120-9</center> ||  J115-6  || <center> F108 </center> ||  White-Yellow (yellow)
|-
|<center>J120-10</center> ||  J115-5  || <center> F107 </center> ||  White-Green
|-
|<center>J120-11</center> ||  J115-2  || <center> F106 </center> ||  White-Violet
|}
{| class="wikitable"
!<center> GI Connector/pin </center>
! Connects to 
! associated circuit wire color 
|-
|<center>J115-7</center> ||  Triac Q10 pin 1  ||  Orange
|-
|<center>J115-8</center> ||  Triac Q18 pin 1  ||  Brown
|-
|<center>J115-9</center> ||  Key pin 
|-
|<center>J115-10</center> ||  Triac Q16 pin 1  ||  Green
|-
|<center>J115-11</center> ||  Triac Q14 pin 1  ||  White-Yellow (yellow)
|-
|<center>J115-12</center> ||  Triac Q12 pin 1  ||  Violet
|}

<center>
<gallery widths=140px heights=180px perrow=5 caption="WPC-089 Power/Driver Board GI Buzz Diagrams provided by Sascha Voskuil">
File:GIBuzzBrown.jpg|<center>Brown GI String</center>
File:GIBuzzOrange.jpg|<center>Orange GI String</center>
File:GIBuzzYellow.jpg|<center>Yellow GI String</center>
File:GIBuzzGreen.jpg|<center>Green GI String</center>
File:GIBuzzPurple.jpg|<center>Violet GI String</center>
</gallery>
</center>
<center>Click on the thumbnails above for the full sized GI buzz image</center>
 
<center>The clickable images above, in an animated gif...</center>

[[File:AnimatedGIConnections.gif|center|An animated diagram of WPC-089 GI connections]]
 

[[File:J120-J121SolderPads.jpg|thumb|300px|left|Critical PCB traces for the brown and orange GI circuits that are often compromised with amateurish attempts to replace J120.]] 
Regarding poor prior rework, sometimes when J120 is replaced, the through holes at pins 7 and/or 8, are pulled causing a loss of connectivity from the board front to the board rear. This will prevent the brown and/or orange color GI circuit from working properly. Additionally, the through hole at J121, pin 6, that routes power to the 3-pin connector at J119, if pulled, will cause the cabinet GI (violet) to not light (coin door lights).
 

<li>'''Burned connectors.''' 
Over long periods of time, both the male and female GI connectors at J115, J120, and J121 often burn. 
This was especially prevalent in early WPC games like Terminator 2. 
[[File:WMS WPC Burnt GI Typical.JPG|thumb|300px|left|Typical burned connector on the output (female) side of the backbox GI on the driver board]]
[[File:BurnedJ120-121.jpg|thumb|300px|right|These female housings for J120/121 are burned so much that they are "welded" to the male headers.]]
[[File:BurnedJ120-121Rwmoved.jpg|thumb|300px|left|The connectors after removal. Get your marshmallows ready.]]
Numerous "hacks" have been employed over the years by well meaning repairmen but the only real way to fix burned connectors is to replace both the male header pins and the female housings/pins. "Trifurcon" phosphor-bronze crimp-on pins are recommended to provide a better connection at the female connector. Note that these must be phosphor-bronze (7A rating, as original). Don't buy them unless the supplier calls that out as the brass version looks the same but is only rated at 5A. If you replace burned female connectors, the male connectors are probably burned too and should be replaced. The damaged surface of the male pins will generate heat, and cause early failure of the replacement connector. Plus, the GI will be dimmer than it should be. J115 is a special case. The black Panduit connector that Williams used on many machines is far superior to any crimp pin, with a 12A rating (compared to 7A for phosphor-bronze Trifurcon pins). These, however, can be hard to find. Fortunately, they rarely burn and therefore rarely require service. Another alternative for high current connections is to use Molex MarKK series contacts (Molex part number 45570-3050) along with Molex 41695 series plugs. Although they cost more than the Trifurcon style contacts, these contacts are rated for a current load up to 13 amps.
 
WPC-089 Power/Driver Board J120/J121 connector repair parts list...

{| class="wikitable"
!<center> Qty </center>
! Part 
! Product ID 
|-
|<center>2</center> ||  11 pin .156 male header (cut to size) ||  26-48-1245
|-
|<center>2</center> ||  Connector, .156 Plug, 11 pin (Molex 41695 series) ||  09-50-8111
|-
|<center>10</center> ||  .156 Trifurcon crimp contacts for the larger gauge wires ||  08-52-0113
|-
|<center>10</center> ||  .156 Trifurcon crimp contacts for the smaller gauge wires  ||  08-52-0125
|-
|<center>2</center> ||  "Keying Pins" for Molex 41695 series plugs ||  15-04-0297
|-
|<center>1</center> ||  Crimp tool ||  1028-CT (or equivalent) 
|}
Note: Product IDs shown above can be found at http://www.greatplainselectronics.com/Category-80.asp. Other vendors may carry these same parts.
 
<li>'''Burned AC power input connector.''' There is also a 9-pin (3x3) connector between the transformer secondary and J115. This connector/pins sometimes burn and may require replacement. Check to ensure that AC power is being delivered to the power/driver board at J115.</li>
[[File:WPCGICabinetConnection.jpg|thumb|300px|left|WPC General Illumination power connection between the transformer secondary and J115 (AC power in). This picture is from a Twilight Zone, which used the newer, multicolored wires between this connector and J115 on the power/driver board.]]
*Set your DMM to AC voltage. If your DMM is not an "auto-ranging" model, expect to measure about 7 volts AC.
*Turn the game on.
*Insert one probe of your DMM (either one) into the rear of the female connector at J115, pin 3.
*Insert the other probe into the rear of the female connector at J115, pin 11.
*You should be measuring 6 to 7 VAC.
*If no voltage is present, examine the 9-pin connector between the transformer secondary and J115, pictured at left.
 
<li>'''Burned traces.''' Usually, this is a secondary problem created after the connectors burn. Visual inspection of the traces might uncover the problem, but "buzzing" them for continuity is the best practice.</li>
<li>'''Failed 2N5401.''' These don't fail very often, but are easy to test following this [[How_to..._(solder,_desolder,_"stitch",_test_transistors,_test_ICs,_etc)#Testing_a_Transistor.2C_Silicon_Controlled_Rectifier_.28SCR.29_or_Field_Effect_Transistor_.28FET.29| procedure]].</li>
<li>'''Failed resistors.''' Again, these don't fail very often but are easy to test with your DMM. Keep in mind that "in-circuit" measurements may not be reliable.</li>
<li>'''Failed 74LS374.''' This is rare too but easy to test following this [[How_to..._(solder,_desolder,_"stitch",_test_transistors,_test_ICs,_etc)#Testing_an_integrated_circuit | procedure]]. You can also test the outputs of the LS374 by probing pins 2, 5, 6, 16 and 19 with your logic probe. At full GI brightness (8), these pins should test as solid "low". At the dimmest GI brightness (1), the above referenced pins should all be pulsing "high". Additionally, pin 1 of the LS374 should always test low and pin 11 should always be pulsing "high".
</li>
<li>'''Failed Triac.''' These rarely fail. But, if you've gotten to this step in the procedure, it's time to replace the Triac. Remember, you need a 4-sector triac.</li></ol>

As these boards age it is easy to pull out the little copper hole liners that connect traces from one side of the board to the other. If you install new connector pins, be sure to check continuity from the new pins onto the board somewhere. This only takes a couple minutes and can save you a lot of time.

=====GI Lamps Not Dimming=====

[[File:WPC089BlankingTraces.jpg|thumb|300px|right|Small traces leading from the through holes of BR2's AC solder pads (pads circled) can be easily damaged, causing GI lamps to not dim. On this board revision, the upper/right through-hole has a small trace on the solder side of the board that connects to the "via" visible to the left of the through-hole. These traces lead to vias which can be seen just SouthWest of R194.]]
The primary cause of GI lamps failing to dim is broken traces at BR2, usually caused when BR2 was replaced. These traces lead to D3 and D38. Both of these traces must be intact for dimming to work as they supply the power to generate the signal to the Zero Cross circuit (ZC) which is key to dimming.

Before you go too far diagnosing the hardware, if your WPC game will not dim the general illumination, make sure that Standard Adjustment #25, "Allow Dim Illum.", is set to "YES". If set to "NO", then the GI will never dim, even during General Illumination test.

General dimming "theory of operation"...
*The driver board generates the ZC signal with the BR2, D3/D38 and U6 circuitry (different resistors).
*The ZC signal is connected to the ASIC (across the driver board, the ribbon, and then across the MPU).
*The ASIC uses the ZC signal to determine when to send the /TRIAC signal to U1 pin 11 (an 74LS374 buffer IC) as it simultaneously presents GI string enable data on the data bus.
*U1 latches GI string enable data from the MPU's data bus.
*The output of U1 forms signals T0 thru T4, which enable the TRIAC circuitry.
 

[[File:ZC_broken.jpg|thumb|300px|left|This is the ZC signal from a Doctor Who with a broken trace between the two 270 ohm resistors after D3. Dimming did not work in this example.]]
[[File:ZC_ok.jpg|thumb|300px|right|This is the ZC signal from a properly working Twilight Zone with General Illumination dimming working correctly.]] 
It is possible that D3, D38 (1N4004 diodes) or the LM339 at U6 have failed. If the ZC test point on the power/driver board is not strobing (which can be seen with a logic probe), something upstream of the test point has failed.

U6 is an LM339 comparator. The resistors around it (R16 and R17, both 230 ohm 1/4 watt) help generate the correct ZC signal. If a resistor is burned or out of spec, or if a trace is broken in the circuit (there are several "vias"), then ZC may still strobe but in an incorrect way which the ASIC doesn't recognize as the zero cross signal.

The ZC may be strobing, yet the GI still won't dim. Use a logic probe to test both sides of diodes D3 and D38 as it is necessary for both the positive going and the negative going portions of the AC sine wave to be detected. If the traces buzz out back to BR2, then suspect one side of BR2 being open. Incredibly, it is possible for the game to work correctly in all regards other than GI dimming with half of the bridge open. Odd...but it happens.
 

[[File:YT.png]] A video demonstrating how to "buzz" the GI circuit connections can be found [https://youtu.be/9qy2rwJ9IEM?si=VG0YxUMGJrwUwq6n here].

====WPC-95 General Illumination Problems====
[[File:WPC95GIToast.jpg|thumb|300px|left|The GI section of a WPC-95 driver board with 6A2 diodes installed. Note the significant burn around the diodes as well as the melted connectors and burned pins.]] 
The General Illumination circuit for WPC-95 games is very similar to WPC games. When the WPC-95 system was implemented, Williams reduced the number of "dimmable" GI circuits from 5 to 3, with 2 of the circuits being lit at all times. Within the two "always on" GI circuits, Williams placed 8 large 6A2 diodes, to create a voltage drop in the circuit which would dim the lamps slightly and presumably lengthen lamp life. However, these big 6A2 diodes create a great deal of heat. Without a heat-sink like those used on the TRIACs, the high heat they produce causes the printed circuit board and traces to burn. 
Later versions of the WPC-95 driver board replaced these 6A2 diodes with zero ohm jumpers.
 

[[File:WPC95GIJumpers.jpg|thumb|300px|left|The back side of a WPC-95 driver board with jumpers installed across the GI circuit.]]
[[File:WPC95Jumpers.jpg ‎|thumb|300px|right|Replacing the 6A2 diodes with 4 zero ohm jumpers.]] 
You can (and probably should) remove the 6A2 diodes, and either replace them with zero ohm jumpers as pictured at right, or add jumpers to the solder side of the board as pictured at left. The solution at left bypasses the diodes completely, by installing the following jumpers.

■ J103 pin 11 jumped to J105 pin 5 
■ J103 pin 12 jumped to J105 pin 6
 

<center>
<gallery widths=160px heights=280px perrow=5 caption="WPC-95 Power/Driver Board GI Buzz Diagrams provided by Sascha Voskuil">
File:Wpc95PinWikiGI-String1-Brown.png|<center>Brown GI String</center>
File:Wpc95PinWikiGI-String2-Orange.png|<center>Orange GI String</center>
File:Wpc95PinWikiGIString3-Yellow.png|<center>Yellow GI String</center>
File:Wpc95PinWikiGI-String4-Green.png|<center>Green GI String</center>
File:Wpc95PinWikiGI-String5-Purple.png|<center>Violet GI String</center>
</gallery>
</center>
<center>Click on the thumbnails above for the full sized GI buzz image</center>
 
<center>The clickable images above, in an animated gif...</center>

[[File:Wpc95PinWikiGI-1-5.gif|center|An animated diagram of WPC-95 GI connections]]
 

====Controlled Lamp Problems====

===== Twist Socket Lamp Not Lighting =====
[[file:wpc-lamp-board-twist-sockets.jpg|thumb|right|300px|A lamp board with twist sockets found in Terminator 2]]
Two things that can fail on lamp boards are individual lamp circuit diodes or the solder pads can develop "divots", where the twist sockets make physical contact with the board. To overcome the divots, simply add a little solder, and carefully reflow the solder pads. Make certain not to apply too much heat...just enough to evenly flow the solder.

With Fire!, a system 11 game, Williams started using lamp boards with .156" header connections for the lamp column and row lines. This allowed for easy removal and service of the lamp boards. However, it introduced some new problems. Because the lamp boards used were single-sided, (this was presumably a cost analysis decision), the .156" header pins can develop cold solder joints and crack due to vibration. The problem can easily be rectified by removing the old solder from the header pins and applying fresh, new solder.
 

<center>
<gallery widths=300px heights=300px perrow=2 caption="Typical issues with lamp board sockets and headers">
File:PCBMountLampDivot.jpg|<center>"Divots" in the connection pad of a "twist in" lamp.</center>
File:WPCPCBLampBoardHeaders.jpg|<center>The solder on these header pins has been reflowed nicely.</center>
</gallery>
</center>

The following actions can help debug an individual socket failure:
# Move the non-working twist socket to another spot that is working. This will test that the bulb and socket itself are working. If not, replace the bulb, try to adjust the socket's contact legs, try to clean off the contact points if they are dirty, and if all that fails, replace the twist socket.
# Move a working twist socket into the position that is not working. If the socket works, the original socket may have been the problem. If the working socket also does not work in the non-working position, there is likely a problem with that position.
# Check the connector, especially if it is an IDC connector. Sometimes a wire can pop out and lose connectivity.
# Remove the lamp board. Check the header pins for cracked solder joints and reflow the solder as necessary. Reinstall and test.
# [[General#Testing_a_Diode|Test the diodes with a multimeter]]. If any are bad, replace them. Make sure to orient the diode the same way that is indicated on the silkscreen. It's sometimes possible that a previous owner installed a diode the wrong way.
# Sometimes the pads on the lamp board that the socket makes contact with get dirty or worn enough to put a divot in the metal. Clean off the contacts, and if that doesn't improve anything, tin the pads with a thin layer of solder.
# If none of this was successful, test for continuity between the lamp board and the driver board.
# If wiring continuity checks out, [[#Controlled_Lamp_Operational_Description|troubleshoot the issue like any other controlled lamp]].
 

===== Controlled Lamp Operational Description =====

WPC feature lamps are controlled from the WPC MPU and ultimately enabled via the driver board. The control signals are as follows.
#The 68B09EP places a data bit pattern on the data bus. This represents the lamp column to be strobed.
#The bit pattern is conveyed to the driver board via the ribbon cable between J211 on the MPU and J113 on the driver board.
#U9 on the driver board (a 74LS240) buffers the column bit pattern for U18 (a 74LS374).
#The ASIC on the MPU asserts the /LMP COL signal which "clocks" the data into U18 by pulsing pin 11.
#U18 outputs are connected to the ULN2803 at U20, which inverts the signal and enables one of eight TIP-107 Darlington transistors (Q91 thru Q98) that enable 18VDC to flow to the enabled column. This completes the column "strobe" portion of lamp matrix operation.
#The 68B09EP places a data bit pattern on the data bus. This represents the lamp rows to be strobed.
#The bit pattern is conveyed to the driver board via the ribbon cable between J211 on the MPU and J113 on the driver board.
#This bit pattern data is presented to four 74LS74s (Dual D-Type Flip-Flops) at U10 thru U13. This sets up a path to ground for the 18V lamp matrix power for each row enabled by the bit pattern
#The ASIC on the MPU asserts the /LMP ROW signal which "clocks" the data into U10 thru U13 via their "reset" signal inputs.
#The (not) Q signal of each 74LS74 enables one of eight TIP-102 Darlington transistors (Q83 thru Q90) that provide the actual path to ground (through a .22 ohm 1 watt resistor) for the 18V lamp matrix power.
#At this point, power flows from the enabled column circuitry, through the game wiring to the lamps, then through the row circuitry to ground for the rows that are enabled.
#The row enable signal is switched off when the LM339 comparators at U15 and U16 detect a voltage rise above the reference voltage present at pins 5, 7, 9, and 11 of both LM339s, via the "set" signal of each 74LS74 (U10 thru U13).

This process repeats itself over and over with the MPU cycling through columns 1 thru 8 while enabling specific rows, lighting lamps at the intersection of the enabled column and the enabled rows.

[[Image:WPC089AlkalineDamagedLampMatrixEnable.jpg|300px|thumb|right|The column trace between the J211 dual row header and the ASIC chip socket (pin 63) clearly corroded away. The lamp row trace is immediately below the column trace and unaffected.]]
There are many possible causes for lamp matrix malfunctions. Some reasons, in order of probability are:
#Lack of 18V lamp matrix power. If LED6 is not lit, or TP8 shows other than 18V, "buzz" F114 for continuity with your DMM. If F114 is blown, test BR1 using the method specified [http://www.pinwiki.com/wiki/index.php?title=General#Testing_a_Bridge_Rectifier here].
#Failure of the row (TIP-102) or column (TIP-107) drive transistor. Both of these are easily diode tested and compared to the other 7 row/column drive transistors.
#For a column failure: Failure of the ULN-2803 at U19. U19 works the same as U20 in the switch matrix, providing a periodic pulse to all columns.
#For a row failure: Failure of a 74LS74 at U10/11/12/13. Again, these parts can either be diode tested for, better yet, use a logic probe to see if they are delivering the necessary pulses. Compare the operation of similar pins.
#Failure of the associated .22 ohm 1 watt resistor in the path between 18VDC lamp matrix power and ground (R150 for example).
#Poor connections between J211 on the MPU and J113 on the power/driver board. Sometimes, reseating the ribbon cable on both ends will "fix" the issue. Replace the ribbon cable and examine the dual row headers if the problem becomes chronic.
#Prior work on the power/driver board. The data bus runs completely across the power/driver board, stopping in at several 74LS374s (U1 thru U5) along the way. The signals pass through the board from component side to solder side at U9. If the same column and row of the lamp matrix are not lighting (i.e. column 5, row 5), it's a good bet that the signal for that row/column is compromised in the area of U9. The traces at each IC are delicate and it's tough for most hobbyists to remove a 20 pin IC without damaging the traces. It's particularly vexing to encounter a problem where a data signal is held low or high by one of the 74LS374s since each data signal is connected to all of them and even using [diode test] sometimes can't identify the faulty IC. Some techs will cut the data signal pin close to the PCB for a 74LS374, using the process of elimination to identify the culprit (not recommended). Enough said, but it's easily seen that power/driver boards can be damaged quite easily by the novice. Send it to a pro.
#Fatigued connections between the ASIC on the MPU and it's chip socket. Since the ASIC provides critical enable signals for the lamp matrix, reseating or [https://www.greatplainselectronics.com/Information.asp?region=139 retensioning] these pins is reasonable course of action. [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Removing_the_ASIC Use a PLCC removal tool] to safely remove the ASIC without damaging the socket.
#Failure of any of the ICs noted above. Each of these ICs can be tested with a DMM set to [http://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit diode test]
#Corrosion on the MPU that might have compromised the enable signals, as seen in the picture at right. Corrosion can and will attack under the header pins at J211 on the MPU.
 

'''Quick Test of Lamp Column Transistors'''

[[Image:CheckingLampColumnDriveTransistors.jpg|300px|thumb|left|"Quick Test" for a shorted lamp column transistor.]]
If the game has an entire column of lamps locked on, there is a good chance that a lamp column transistor has shorted. Testing for this condition is very simple. Set your DMM to continuity. Touch one probe to the 18V lamp matrix test point as pictured at left. Touch the other probe to the tab of each of the TIP-107 transistors. Any that "buzz" are shorted and will need to be replaced.
 

'''General Lamp Matrix Testing'''

The control logic for the WPC lamp matrix can be tested by connecting a spare lamp using two jumper wires. The following sections show the separate procedures for testing the lamp matrix columns and rows. The example applies to WPC-089 power/drive boards. The procedure is the same for WPC-95 power/driver boards, but the connector designations and transistor numbers differ. Images authored by Sascha Voskuil, used with permission)

 
<center>Testing a working lamp matrix circuit on a WPC-95 Power/Driver board
[[File:LampMatrixGeneralTesting.gif|center|General testing of the lamp matrix circuit on a WPC-95 Power/Driver board. All columns operating normally.]]

 
Column 4 shorted in the lamp matrix circuit on a WPC-95 Power/Driver board
[[File:LampMatrixColumn4Shorted.gif|center|Testing the lamp matrix circuit on a WPC-95 Power/Driver board that has column 4 shorted.]]

 
Column 4 inoperative in the lamp matrix circuit on a WPC-95 Power/Driver board Note: In this animation, columns 4 and 2 are inoperative. 
[[File:LampMatrixColumn4Inop.gif|center|Testing the lamp matrix circuit on a WPC-95 Power/Driver board that has column 4 open (inoperative).]]
</center>
 

We provide this section for completeness knowing that WPC games offer independent lamp row and column tests as part of the diagnostics. 

'''Testing the lamp matrix columns:'''

[[Image:Placeholder.jpg|300px|thumb|right|Jumper connection for testing lamp matrix columns.]]
Use the following procedure to test the TIP-107 transistors that drive the lamp matrix columns. Note that a diode is not needed for these tests since it's function is to block current flow and prevent interaction between the lamps in the matrix. In this test we are connecting a single lamp at a time.

#Remove the backglass and open the insert to get access to power/drive board connectors J133/134/135 (row) and J136/137/138 (column).
#Unplug all connectors with red or yellow wires leading to them. These are the lamp matrix connections (lower right corner of power/driver board)
#Turn the game on and start "All Lamps" test in the Test/Diagnostic Menu.
#Clip one end of the test jumper to J137 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to J133 pin 1, the rightmost pin on the connector
#The test lamp should flash to indicate that the column driver is working.
#Repeat the test for the pins 2 through 9 on J137. There is no pin 8 as it is the key.

If a column doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test.

The following table shows the lamp number and driving transistor for each of the column pins.
{| class="wikitable"
!   Pin   
!Wire Colors
!Lamp number
!Transistor number
|-
|<center>J137-1</center> || <center>Yel-Brn</center> || <center>1</center> || <center>Q98</center>
|-
|<center>J137-2</center> || <center>Yel-Red</center> || <center>9</center> || <center>Q97</center>
|-
|<center>J137-3</center> || <center>Yel-Orn</center> || <center>17</center> || <center>Q96</center>
|-
|<center>J137-4</center> || <center>Yel-Blk</center> || <center>25</center> || <center>Q95</center>
|-
|<center>J137-5</center> || <center>Yel-Brn</center> || <center>33</center> || <center>Q94</center>
|-
|<center>J137-6</center> || <center>Yel-Blu</center> || <center>41</center> || <center>Q93</center>
|-
|<center>J137-7</center> || <center>Yel-Vio</center> || <center>49</center> || <center>Q92</center>
|-
|<center>J137-8</center> || <center>Key Pin</center> || <center> </center> || <center> </center>
|-
|<center>J137-9</center> || <center>Yel-Gry</center> || <center>57</center> || <center>Q91</center>
|}

'''Testing the lamp matrix rows:'''
[[Image:Placeholder.jpg|300px|thumb|right|Jumper connection for testing lamp matrix rows.]]
Use the following procedure to test the TIP-102 transistors that drive the lamp matrix rows.

#Remove the backglass and open the insert to get access to power/drive board connectors J133/134/135 (row) and J136/137/138 (column).
#Unplug all connectors with red or yellow wires leading to them. These are the lamp matrix connections (lower right corner of power/driver board)
#Turn the game on and start "All Lamps" test in the Test/Diagnostic Menu.
#Clip one end of the test jumper to J133 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to J137 pin 1, the rightmost pin on the connector
#The test lamp should flash to indicate that the column driver is working.
#Repeat the test for the pins 2 through 9 on J133. There is no pin 3 as it is the key.

If a row doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test.
The following table shows the lamp number and driving transistor for each of the row pins.

{| class="wikitable"
!   Pin   
!Wire Colors
!Lamp number
!Transistor number
|-
|<center>J133-1</center> || <center>Red-Brn</center> || <center>1</center> || <center>Q90</center>
|-
|<center>J133-2</center> || <center>Red-Blk</center> || <center>2</center> || <center>Q89</center>
|-
|<center>J133-3</center> || <center>Key Pin</center> || <center> </center> || <center> </center>
|-
|<center>J133-4</center> || <center>Red-Orn</center> || <center>3</center> || <center>Q88</center>
|-
|<center>J133-5</center> || <center>Red-Yel</center> || <center>4</center> || <center>Q87</center>
|-
|<center>J133-6</center> || <center>Red-Grn</center> || <center>5</center> || <center>Q86</center>
|-
|<center>J133-7</center> || <center>Red-Blu</center> || <center>6</center> || <center>Q85</center>
|-
|<center>J133-8</center> || <center>Red-Vio</center> || <center>7</center> || <center>Q84</center>
|-
|<center>J133-9</center> || <center>Red-Gry</center> || <center>8</center> || <center>Q83</center>
|}

===== Lamp Issue Caused by Connecting "Growth" Connectors =====
[[File:WPCErroneousConnection-1.jpg|300px|thumb|left|A misplaced connector on Judge Dredd. Image courtesy of Chuck Sanderson, CP Pinball]]
[[File:WPCErroneousConnection-2.jpg|300px|thumb|right|The connector, not connected, as it should be.]]
[[File:LampMatrixHeadache.jpg ‎|300px|thumb|left|Lamp Matrix failure "map" created when J136 is erroneously connected on Judge Dredd]]

An issue that seems to come up fairly often is caused by literally placing a square peg into a round hole.

The images shown here from a Judge Dredd shows a "growth" connector wired from the factory that was never used during production. It happens to be in the proximity of J136, a lamp matrix connector and the wires are lamp matrix wires (colored red and colored yellow). One could almost be forgiven for forcing the female housing onto J136 even though the connector types are different.

With this connector in place, all kinds of lamp matrix havoc ensues as shown in one lamp matrix "error map" shown at left.

The solution is simple. Remove the connector.

All images provided by Chuck Sanderson, [https://cppinball.com/ CP Pinball]
 

===Switch Problems===

Switches in WPC games fall into two categories, those within the switch matrix, and "direct" switches.

====Diode and Switch Matrix Wiring Orientation on a Microswitch====
[[File:Submicro Switch Wiing.jpg|300px|left|thumb|Typical wiring for any Microswitch]]
First and foremost, all switches located in the switch matrix MUST have a diode. Secondly, the diode has to be installed in the correct orientation. If a diode is installed "backwards", the end result my be that all of the switches in that particular row get triggered or even stranger issues occur. Finally, the diode legs must not be connected to any of the other wires or terminals of the switch, or the switch will funk up the switch matrix.

Here is the correct orientation for the wiring and the diode on a microswitch. The white wire w/ trace and non-banded side of diode is connected to NC terminal. The banded side of diode is connected to common terminal. Finally, the green wire w/ trace is connected to NO terminal.
 

====Built-in Switch Testing====
WPC games monitor switch closures as the game is played. If a switch is not activated after a certain number of balls (usually 30, but will vary depending on the switch in question), the game will show the "credit dot", an indication to the operator that a switch may be faulty. Some switches are not often closed (like switch 55 located in the White Water pop bumper garden) and some switches simply aren't hit by rookie players (like the upper exit to the Twilight Zone mini playfield). Some switches will be marked non-operational immediately after a certain event where the switch is known to have been activated (switches related to The Shadow's brick wall drop target are one example; any error in the lock sequence causes the credit dot to light immediately). 

There is a table held in RAM that contains counters for all monitored switches. Each ball served decrements the counter for each switch; as soon as that switch is hit on the playfield, the counter is reset to the initial value. The credit dot gets lit when any counter for any monitored switch goes to zero. Switches such as flipper optos are set to very low initial values, as flippers are hit on every ball. It would have been possible to have higher values set for switches that would occasionally be activated but not often by novice players as noted above, however this aspect of the programming was rarely if ever used. 

When a credit dot is lit, often the game will offer "switch compensation", which was a Williams' patented feature, that allowed a nearby or alternate switch to achieve the same result as hitting the original, marked non-operational, switch. This enabled a game with faulty switches to still be played close to the original gameplay. Sometimes the faulty switch will auto-clear itself when activated, but more often than not, the fault would have to be cleared manually. To clear a switch manually, enter the "Switch Edges" test (as described below), and manually activate the switch. If the switch in question is functioning properly, activating the switch will remove the credit dot. 

The first action to be taken is to enter diagnostics. The game will indicate the reason(s) for the credit dot on the display, upon pressing the enter button on the coin door to receive a test report. 

Since the normal switch matrix is 8 by 8, games like Twilight Zone, Star Trek: The Next Generation, and Indiana Jones employ a 9th column of switches. These switches are tested via a dedicated switch test tied to the playfield feature. An example is the Star Trek: The Next Generation cannon switches. 

=====T.1 Switch Edges Test=====
[[file:WPCSwitchTestExample.jpg|400px|thumb|left|An example switch matrix display, this one from Twilight Zone. Note the opto switches in column 7 (for example) are shown as boxed dots.]]
Switches can be tested by entering Test T.1, Switch Edges. Switch Edges Test presents an 8 by 8 switch matrix grid with one or two switch columns outside of the matrix. The additionally columns are for dedicated switches. The left column is for switches located on the coin door (all WPC games), and the right column is for flipper cabinet and flipper EOS switches (WPC games which use a Fliptronics board - Addams Family and newer). Open switches show as a simple dot on the DMD. Closed switches show as a boxed dot on the DMD. Microswitches and leaf switches will show as a dot when open. Optos will show as a boxed dot when the opto beam is not being broken. The last closed switch name and number will be shown on the display along with the two wire colors that are connected to that particular switch. While in switch edges test, manually closing properly operating switches will be shown on the display. 

=====T.2 Switch Levels Test=====

====Direct Switch Problems====

'''Direct switch operation'''

Direct switches include:
*Left coin chute
*Center coin chute
*Right coin chute
*4th coin chute
*Service Credits/Escape (referred to as "escape" here)
*Volume down/Down
*Volume up/Up
*Begin Test/Enter

Direct switches are not part of the WPC switch matrix. All of the direct switches are located on the coin door, and connect to the MPU at J205. The MPU senses these switches individually, and apart from the switch matrix. Therefore, isolation diodes are not used with direct switches.

Normally, with the switch open, the LM339s at U16 and U17 compare 12V (supplied on the MPU to both the switch and to the LM339) with 5V (as a comparison level) and signals the 74LS240 at U15 that the switch is open. When the switch closes, it shorts the 12V to ground and the comparison at the LM339 then indicates to U15 that the switch is closed. U15 is "clocked" by pin 48 of the ASIC (SW DIR), causing U15 to present its data to the data bus. The 6809/ASIC "debounces" the switch. Debouncing is not a factor to be considered here and doesn't factor in switch testing at all.

'''Direct Switch Pinout at J205 for both WPC and WPC-S MPUs''' 
Notes: 
:J205, pin 5 is the "key" pin.
:J205, pin 10 provides ground (black wire)
:J205, pin 11 is unused
:J205, pin 12 is an "enable" back to the coin door interface board 

{| class="wikitable"
!Signal
!Wire color at J205
!MPU pin
!Diode
!LM339 & input pin
!U15 input pin
|-
|Left chute || <center>orange/brown</center> || <center>J205-1</center> || <center>D15</center> || <center>U17-5</center> || <center>11</center>
|-
|Center chute || <center>orange/red</center> || <center>J205-2</center> || <center>D16</center> || <center>U17-7</center> || <center>13</center>
|-
|Right chute || <center>orange/black</center> || <center>J205-3</center> || <center>D17</center> || <center>U17-11</center> || <center>15</center>
|-
|4th chute || <center>orange/yellow</center> || <center>J205-4</center> || <center>D18</center> || <center>U17-9</center> || <center>17</center>
|-
|Escape || <center>orange/green</center> || <center>J205-6</center> || <center>D11</center> || <center>U16-9</center> || <center>2</center>
|-
|Down || <center>orange/blue</center> || <center>J205-7</center> || <center>D12</center> || <center>U16-11</center> || <center>4</center>
|-
|Up || <center>orange/violet</center> || <center>J205-8</center> || <center>D13</center> || <center>U16-7</center> || <center>6</center>
|-
|Enter || <center>orange/gray</center> || <center>J205-9</center> || <center>D14</center> || <center>U16-5</center> || <center>8</center>
|}

'''Debugging direct switch problems'''

To discover the problem as quickly as possible, we'll divide the problem into smaller pieces. We must first determine if the problem is on the MPU board or the problem lies with the wiring to the coin door and/or the specific switch. If your MPU has obvious alkaline damage at U15, U16, or U17, address the alkaline damage first.

Begin testing with the game OFF.

'''Isolate the problem to the MPU or to the game wiring/switch '''
#Remove connector J205 from the MPU.
#Build a jumper wire with alligator clips on both ends.
#Clip one end of the jumper wire to the game's ground braid in the game head.
#Turn the game on
#Carefully touch the other end of your jumper wire to the appropriate pin on J205 as shown in the table.
#If the MPU carries out the function of the switch, the problem is not on the MPU.
#If the MPU does nothing, the problem is on the MPU.
#Skip to the appropriate section below.

'''Identifying problems NOT on the MPU '''

'''Test the direct switch's path to ground '''
#Your game should still be turned off.
#DMM set to continuity.
#Clip the black lead of your DMM to any game ground, like the lockdown bar or ground braid.
#Red lead on the solder joint between the switch and the black wire that provides ground.
#You should hear "tone". If not, further diagnose the break in the black wire between the solder joint and game ground.

'''Test the direct switch itself '''
#Black lead of your DMM still clipped to game ground.
#Red lead on the solder joint opposite the black wire (or bare wire jumper) of the switch under test.
#Depress the switch. You should hear "tone". If not, the switch is defective and not "making". See the section below that describes cleaning these switches.

'''Test the signal path to the MPU '''
#Clip the black lead of your DMM on the solder joint opposite the black wire (or bare wire jumper) for the switch under test.
#Remove the connector plug at J205 from the MPU.
#Red lead on the appropriate pin of J205 for the switch under test. See the table above. It's easiest to access the pin through the rectangular hole in the back of the connector where the pin's "tang" snaps in.
#You should hear "tone". If not, there is a discontinuity in the wire between the direct switch and J205. Note that the coin door interface board is between these two points. The coin door interface board is a "pass-through" for these signals and rarely causes a problem. Still, reseating connectors J1, J3, and J4 on the coin door interface board might uncover the problem. More likely, the wire between J1 on the coin door interface board and J205 has a break in it.

'''Identifying problems on the MPU '''

'''Test the signal path through J205 and onto the MPU '''
J205 is right below the battery holder and as such, sometimes receives the unwanted gift of dripping alkaline from depleted batteries. Carefully examine both the male and female connections of J205 for alkaline "greenies". Assuming no alkaline damage... 
#Begin with your game turned off.
#Connect J205 to the MPU.
#Clip the black lead of your DMM to the solder joint opposite the black wire (or bare wire jumper) for the switch under test.
#Red lead on the banded end of the appropriate diode shown in the table above.
#You should hear "tone". If not, there is either a problem with the physical connection at J205 or the alkaline "greenies" are sneakier than you gave them credit for. Re-examine J205 and the surrounding area of the board for alkaline damage. The traces from the switch connectors are very small and it takes very little alkaline damage to compromise them. You may also re-pin the female side of J205.

At this point, a logic probe would be the best tool to use. You can pick up 5V power for your probe across the electrolytic cap at C31 which is immediately to the right of the battery holder. Black lead on the negative side (top of the cap). Red lead on positive side (bottom). The board is silkscreened with polarity markings. Set the logic probe to "CMOS" test mode, as you will be measuring 12VDC.

If you don't already have a logic probe, you should. Although for this test, you can still get by with your trusty DMM. Clip the black lead of your DMM to game ground. The ground braid in the head is a good place to pickup ground at this point. Set your DMM to DC volts.

'''Test the LM339 inputs '''
#Start with the game turned off.
#Again, set your logic probe to "CMOS"
#Clip one end of your jumper wire to the appropriate pin of J205. Leave the other end of your jumper wire unconnected, but handy as you'll touch it to ground later.
#You now need to turn the game ON.
#Measure the signal at the appropriate LM339's appropriate pin shown in the table above. Either place your logic probe on the pin or place the Red lead of your DMM on the pin. The signal should measure high (or about 12VDC with your DMM).
#Now, with your other hand, touch the free end of your jumper wire to the ground braid in the backbox as you observe the results.
#You should see the signal transition to low. If you still measure high, then the pin isn't being grounded correctly. Candidates are a failed diode/resistor in the circuit, the board trace between the diode and the LM339 is compromised, or a badly failed LM339.

'''Test the LM339 outputs/74LS240 (U15) inputs '''
#Set your logic probe back to TTL as you will be measuring 0 - 5V signals
#Measure the signal at the appropriate pin (see table) of U15. The signal should measure high (or about 5VDC with your DMM).
#Touch the free end of your jumper wire to the ground braid in the backbox as you observe the results.
#You should see the signal transition to low. If you still measure high with the jumper wire grounded, then either the LM339 outputs have failed, the board trace between the LM339 and U15 is compromised, or the 74LS240 has failed and is corrupting the signal. You can test U15 using the procedure in the "How to..." section of PinWiki, [https://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit here].

The output side of U15 can't be tested effectively since that is the processor/ASIC data bus and should be constantly and irregularly changing states.

If you've followed this process step-by-step, you should have identified the problem with the signal and will be able to effectively perform the appropriate repair.

'''Cleaning direct switches'''

Coming soon...will describe disassembly and cleaning...
Sometimes, several rigorous open/close cycles will "clean" corrosion from the switch.

====Switch Matrix Problems====

'''Isolate the problem to the MPU or to the game wiring/diodes/switches '''

Follow these steps to determine if the switch matrix problem is on the CPU or somewhere in the game wiring.

#Remove connectors J206/J207, J208/209 and J212 from the bottom of the CPU (J206 and J207 are electronically the same and J208 and J209 are electronically the same).
#Clip one lead of a test jumper to pin one of J207 making sure you don't touch any of the nearby pins on J207.
#Power the game on, and enter Switch Edge test (you've left J205 on the CPU so the diagnostics switches still work).
#Touch the other end of the jumper to pin one on J209, then pin two and so on. You should see (and hear) the CPU indicate that switches #11, #12, #13, etc. are being "made" as you touch the pins of J209. You should *never* see multiple switches being made.
#Move the jumper from J207 pin 1 to pin 2. Re-test to every pin on J209, listening for the machine to read every switch as closed. Continue in a similar manner testing each pin of J207 to every pin in J209.

The following images, provided by Sascha Voksuil, grapically depict the above tests of the on-board switch matrix circuitry with a jumper wire. A diode is not required since the test jumpers directly from a single pin to a single pin. Remember, the purpose of switch diodes is switch isolation. Also, have no fear conducting this test. Unless you connect one end of the wire to high voltage, nothing can be damaged.

[[File:Switch matrix test ROWs1-8 with COL1.gif|left]][[File:Switch matrix test COLs1-8 with ROW1.gif|right]]
 

If only one switch shows on the Switch Edge test for each pin combination, then the CPU's switch matrix is working properly and you can confidently assume that any switch problems lie elsewhere. Possibilities include a shorted wire, bad/broken/shorted diode, bad under playfield opto board, bad coin door interface board, etc. If the problem is observed with row 2 of the switch matrix, and you're game has a "-1 Power/Driver" board installed (the one with the flipper power relay), it is possible that one/both of the 4N25 opto-isolators on the power/driver board have failed. These opto-isolators communicate flipper switch closures for pre-FlipTronics games.

If multiple switch closures are reported when you touch one pin of the connector, or if the CPU reports a row or column short, then there is a fault with the switch matrix circuitry on the CPU board itself. Be aware that an additional fault may still be present on the playfield. Switch matrix chips do not simply blow for no reason!

<center>
<gallery widths=300px heights=300px perrow=3 caption="Blown ULN2803 (U20) Examples">
File:BlownULN2803.jpg|<center>An obviously blown ULN2803 (U20) caused by shorting 50V coil power to the switch matrix. Ouch!</center>
File:WPCBlownULN2803.jpg|<center>Another obviously blown ULN2803...happens all the time...Don't work on your game with power on.</center>
File:WOCBlownU14.jpg|<center>Another obviously blown ULN2803...the HV jolt also took out U14, a 74LS374 which buffers the ULN2803 from the processor data bus.</center>
</gallery>
</center>

Catastrophic Failure of ULN2803 or Other Switch Matrix Parts

[[Image:CoilLugShortedToMetal.jpg|300px |thumb|left|Example jumper connection for testing the switch matrix. Image courtesy of PinSider "sturner".]]
[[Image:CoilWrapperRubAE-23-800.jpg ‎|300px |thumb|right|A coil wrapper that has rubbed through to the copper windings due to long term vibration against a loose screw used to secure the coil bracket. This coil is from the "Thing Kickout" in The Addams Family. It electrified the entire "thing" mechanism box and caused the ULN2803 to be destroyed. Image courtesy of JT Amusements.]] 
One fairly common reason that a ULN2803 or other switch matrix circuitry may blow is a short to coil power. In the picture at left, the coil that actuates the "Bridge Diverter" on the game Twilight Zone, is touching the coil bracket on one side. Since coil power is present at both coil lugs (which is normal), a coil lug touching metal will conduct coil power to that metal. In this case, the coil bracket touches the bridge diverter piano wire and then the coil diverter and then the entire wireform. If a switch matrix solder tab or switch blade metal shorts to the wireform, poof! Get ready to replace the ULN2803.

Another way for HV to destroy the ULN2803 and other switch matrix circuitry is shown at left. Here, the coil wrapper has worn through, and then the enamel coating on the coil winding rubbed away, causing a short of coil power to the coil bracket. Just as the instance above showed, this places coil power onto the coil bracket and anything touching it, including switches.
 

===== MPU Circuitry Switch Matrix Problem Diagnosis =====

====== Quick Switch Column Strobe Testing ======

[[File:WPCSwitchColumnStrobeBenchTest.jpg|300px |thumb|left|Testing the switch column strobes quickly with a logic probe. The picture also shows a convenient place to connect logic probe power leads.]] 
A quick way to test that switch column strobes are working properly, is to use a logic probe as shown in the picture at left. Each pin of J206/J207 (all WPC MPU versions) should be pulsing high. 

====== Further MPU Circuitry Diagnosis ======

The following image (authored by Sascha Voskuil, used with permission) will help diagnose particular ICs at fault on the MPU.
[[File:WPC-089MPULayout.jpg|300px|thumb|left|Color Coded Switch Matrix Circuitry.click image to enlarge]] 

Let's use the diagram above to walk through a simple "on board" switch matrix issue.

A board presented with very slight alkaline damage to U20, the ULN2803. After socketing, and replacing the ULN2803, column 3 still failed to strobe. We used out logic probe to determine that pin 16 of U20 was strobing. Therefore, there MUST have been an on board fracture of the trace. Setting our DMM to continuity, and buzzing between J206 pin 3 (marked with a gray "3" in the diagram) and U20 pin 16 failed. Moving our probe from J206 pin 3 to the junction of R69 and C13 (also marked with a gray "3" in the diagram) succeeded. However, buzzing between the junction of R69/C13 and U20 pin 16 succeeded. Using this information, we must conclude that the discontinuity in the trace was between J206 pin 3 and the junction of R69/C13.

[[File:WPCSwitchMatrixCorrodedTraceAnnotated.jpg|300px|thumb|left|A look under connector J206 showing alkaline corrosion damage. This caused column 3 of the switch matrix to malfunction.]]
[[File:WPCSwitchColumnOpenTrace.jpg|300px|thumb|right|Another trace destroyed by prior alkaline corrosion that had seeped under column header connector.]] 
The picture at left shows the problem. Once the J206 header was removed, we could see that alkaline had dripped onto the connector and leached down to the solder joint. The corrosion etched enough of the trace away to prevent connectivity.

The image at right shows yet another example of a switch column trace eaten away by alkaline corrosion.

[[image:YT.png]] A YouTube video demonstrating diagnosis of this issue can be found [https://www.youtube.com/watch?v=EFqM21DR438&t=240s here]
 

[[File:WPCSwitchMatrixHeaderCorrosion.jpg|300px|thumb|left|A different board, with a similar problem at the header pins...]]
[[File:WPCSwitchMatrixConnectorCorrosion.jpg|300px|thumb|right|...and the matching female housings.]] 
The picture at left shows another WPC-089 MPU board with a similar problem, but much worse. This board was the victim of dripping alkaline which invaded the trace which runs under the "C17" label to J206-9 and J207-9.

The picture at right shows the female connector housings that were the victim, and transportation medium, for the alkaline corrosion. The connector on the left required repinning. The connector on the right showed only light damage which was cleaned up with a vinegar swab.
 

[[File:CorrodedWPCConnector.jpg ‎|300px|thumb|left|Corrosion...]]
[[File:ImprovedSwitchMatrixDiagram.jpg|300px|thumb|right|Switch Matrix Circuit Operation. Note: Colors are coordinated with the prior diagram (authored by Sascha Voskuil, used with permission). Click image to enlarge.]] 
Another clear example of a connector requiring replacement is shown at left.
 
[[File:CorrodedWPCConnector1.jpg ‎|300px|thumb|left|More Corrosion...this one from a SlugFest]]
 

===== Switch 11 or Switch 12 Reported as Closed With All Switch Matrix Connectors Removed =====
[[File:4N25Failed.jpg|300px|thumb|left|In this image, the switch matrix connectors have been removed yet switch 11 is shown closed. One of the two 4N25 opto-isolators has failed.]]
A seemingly impossible behavior can be caused by a failed 4N25 Opto Isolator on a "-1" version of the WPC Power/Driver board including RottenDog Power/Driver boards. After removing all switch matrix connectors (not the direct switch connector) from the MPU, switch 11 and/or switch 12 will be reported as closed. This can also lead to all of column 1 being reported closed when any switch is closed outside of column 1. All of the column that switch is in will also be reported as closed.

The 4N25s can be tested as described below.

Another quick test is to remove the ribbon between the MPU and the Driver board. This prevents the driver board from reporting closed switches.
 

===== Cabinet Flipper Switch Detection Problem Diagnosis for Pre-FlipTronics Games =====

[[File:WPCOptoIsolators.jpg|300px|thumb|right|Dual 4N25 Opto Isolators on the "-1" version of the WPC Power/Driver board can be seen in the top center of this picture (two 6 leg ICs at U7 and U8).]]
Pre-FlipTronics games detect closure of the flipper cabinet switches via two 4N25 Opto Isolators on the "-1" version of the power/driver board. If the "cursor" can't be moved during entry of HSTD initials or if the cabinet flipper buttons don't control video mode correctly, there is a good chance that one/both of the 4N25 opto isolators is shot. Games that shipped with the "-1" Power/Driver board include:
*Funhouse
*Harley-Davidson
*The Machine: Bride of Pin*Bot
*Gilligan's Island
*Slugfest
*Terminator 2: Judgement Day
*Hurricane
*Party Zone
 

[[File:WPCEarly-1PowerDriverBoard4N25.jpg|457px|thumb|left|Illustration provided by, and used with the permission of, Sascha Voskuil aka "Zaza"..]] 
The image at left illustrates the switch matrix connection between the 4N25 Opto Isolators on the Power/Driver board and the MPU board.
 

[[File:WPCSwitchRowSchematicError.jpg|457px|thumb|left|Illustration provided by, and used with the permission of, Sascha Voskuil aka "Zaza".]] 
Note that some revisions of the WPC schematics contain an error, as illustrated by the image at left.
 

Fortunately, testing an opto coupler is simple using the diode test function provided by most DMMs. Set the DMM to diode test, compare results against those pictured below (this test conducted on a 4N25 contained on a System 11 Interconnect Board).

<center>
<gallery widths=300px heights=300px perrow=4 caption="Testing a 4N25 Opto Coupler">
File:4N25Internal.jpg|<center>The internal schematic of the 4N25. Pins 1 and 2 connect to an internal diode (LED). Pins 4 thru 6 connect to a PNP photo transistor.</center>
File:4N25Test3.jpg‎|<center>Testing the diode connected to pins 1 and 2. Red on pin 1, black on pin 2</center>
File:4N25Test2.jpg‎|<center>Testing part of the photo transistor. Black on pin 5, red on pin 6</center>
File:4N25Test1.jpg‎|<center>Testing part of the photo transistor. Black on pin 4, red on pin 6</center>
</gallery>
</center>
 

====== Special Note regarding RottenDog Power/Driver boards manufactured prior to February, 2012 ======

[[File:WPCRottenDog4N25Error.jpg|300px|thumb|left|Illustration provided by, and used with the permission of, Sascha Voskuil aka "Zaza".]] 
RottenDog aftermarket power/driver boards manufactured prior to February, 2012 contain a trace layout/connection error that exchanges the function of the two 4N25 Opto Isolators on the board. That is, the 4N25 that should report a left flipper closure actually reports a right flipper closure, and vice-versa. This error can be corrected via two cuts and two jumpers, as illustrated in the image at left.
 

[[File:WPCRottenDog4N25ErrorCorrected.jpg|300px|thumb|left|Image provided by, and used with the permission of, PinSider "troxel".]] 
Shown at left is the correction implemented by PinSider "troxel".
 

[[File:WPCRottenDog4N25ErrorCorrected1.jpg|300px|thumb|left|Image provided by, and used with the permission of, PinSider "troxel".]] 
The same image, annotated by Pinsider "zaza", calls out the need for caution when making this mod. As can be seen, 75VDC is present in the area. A better implementation might be to route the jumper wires around the 4N25 instead of under it.
 

==== WPC95 Flipper Cabinet Switch Processing====

[[File:WPC95CabinetSwitchCorrosion.jpg|300px|thumb|left|Corrosion between pins 9 and 10 on this WPC-95 MPU caused a short between cabinet flipper switch circuits resulting in both flippers actuating when either cabinet switch was closed.]]
[[File:J212Corrosion.jpg|300px|thumb|right|Corrosion on some of these pins caused erratic cabinet switch operation.]] 
The WPC-95 system implementation moved the cabinet flipper button and EOS switch sensing from the FlipTronics II board to the MPU board. Simple voltage level comparison via LM339s senses shorts to ground for those switches. The connector that cabinet switch wiring is connected to (J212) is directly below the battery holder where leaky batteries can "drip" onto the connector, corroding both under the connector and the pins on the connector. Corrosion can cause many odd problems. If this happens, the corrosion can cause the flipper buttons to be sensed intermittently and/or incorrectly.

Pictured at left is one case of corrosion impacting flipper operation. The corrosion caused the circuit to sense that both of the cabinet flipper buttons had been pressed when only one had been pressed. Standard alkaline corrosion cleanup takes care of this issue.
 

====Opto Switches====

=====Basic Operation=====
Williams opto switches are comprised of a "transmitter" and a "receiver" opto, which are each unique parts. This is different from later Sega and some Stern game systems where the optos that serve as transmitter and receiver are identical.

The transmitter opto is housed in a white plastic frame. It is powered by unregulated 12VDC. If the opto is good, measuring either solder joint of the opto should read about 12VDC as long as the game is turned on.

Note that the ball trough uses these opto transmitters also. Orient the ball trough transmitter flat side as is silkscreened on the board.
{| border="0"
|[[file:OptoTransmitter.jpg|300px|thumb|left|The solder side of a typical Williams opto transmitter.]]
|[[file:OptoTransmitterLED.jpg|300px|thumb|right|The component side of a typical Williams opto transmitter. When replacing the opto, orient the flat side toward the "K" (equivalently, orient the "short" leg of the opto toward the "K")]]
|[[file:UOptoGuts.jpg ‎|300px|thumb|right|The "guts" of a "U" opto. These are simply miniaturized versions of the larger optos, with a transmitter side and a receiver side]]
|}

The receiver opto is housed in a black plastic frame. This "IR detector" opto conducts the 12VDC supplied to it, as long as the transmitter's "light" is cast upon it. Once the transmitter light is removed, the opto no longer conducts the 12VDC. Typically, circuitry on an "opto switch board" interprets the lack of 12VDC using an LM339 comparator, and indicates that the switch is open. Remember that the "sense" of opto switches is reversed from regular "hard" switches such as leaf switches and micro-switches.

Note that the ball trough uses these opto receivers also. Orient the ball trough receivers flat side so that the leg on the flat side is furthest away from the "ear" that is silkscreened on the board.
{| border="0"
|[[file:OptoReceiver.jpg|300px|thumb|left|The solder side of a typical Williams opto receiver.]]
|[[file:OptoReceiverLED.jpg|300px|thumb|right|The component side of a typical Williams opto receiver with an aftermarket receiver LED. When replacing the opto, orient the flat side toward the "C" (equivalently, orient the "short" leg of the opto toward the "C"). OEM LEDs have an "ear" that matches the silkscreen on the board]]
|}

=====Opto Testing=====
[[file:OptoTestingWithDigitalCamera.jpg|300px|thumb|left|Testing an opto "sending" unit with a digital camera. This opto pair senses "Rudy Hits" in Funhouse. The white opto housing can be seen (upside down)]] 
The "sending side" or transmitter side of an opto pair, which should be housed in a white plastic frame, can be tested with just about any digital camera. In the picture at left, an iPhone camera was used to clearly see the purplish glow of a working opto sender.

The "receiving side" of an opto pair, which should be housed in a black plastic frame, can be tested with just about any strong incandescent flashlight. Note that an LED flashlight does not typically work too well for this test. Place the game in switch test. Block the sending opto that would normally illuminate the receiver under test. Shine your bright incandescent flashlight on the receiver opto. The switch state as shown on the display should change.
 

=====7 Opto Board Testing=====
[[File:7OptoBoard.jpg|400px|thumb|right|An example WPC 7 Opto Board, as found in AFM, WH2O, and many other WPC games.]]
The 7-Opto Board (A-14977, A-15576, A-15595) pictured at right, can be tested "in-situ" with a simple jumper wire and a DMM.

'''Procedure''' 
Test the LM339 comparators

#Place the game into switch test (T.1)
#Remove the balls from the game to prevent them from crashing down on the playfield (or stuff a rag into the ball loading hole)
#Place the playfield in the vertical position
#Remove the J2 connector on the 7 opto board
#Clip one end of a jumper to J2/pin 10
#In turn, touch the other end of the jumper to pins 1 through 7 of J2
#With each connection, a opto switch activation should be enunciated on the display
#If all 7 switch activations are enunciated, this proves that all of the LM339 comparator circuits are working.

Test the 12VDC power supply circuits
#Set a DMM to DC volts (less than 20 if not using an auto-ranging DMM)
#Remove the J1 connector
#Clip the black lead of a DMM to J1/pin 10 (ground)
#With the DMM red lead, measure DC voltage at pins 1 through 8 (excluding pin 4)
#Each pin should measure about 12VDC
#If all 7 pins measure about 12VDC, this proves that each of the 12V power circuits (and the 270 ohm current limiting resistors) are working.

If a game opto pair fails to function properly, yet both of the above tests pass, then either the opto transmitter or receiver has failed or the wire/connector connection between the opto board and one/both playfield optos has failed.

==== "Jittery" Opto Switches ====
It is possible for all opto switches in the game to act erratically. This can be difficult to diagnose because the problem can manifest itself in various ways during game play. For instance, the bulldozer blade in "Roadshow" may occasionally be unable to find it's home position. Or, the auto launcher in "Twilight Zone" may seem to want to launch a ball when none is present. Since the cabinet flipper switches are sometimes optos as well, the game's flippers may also behave strangely.

The first step is to check the optos in switch edge test. If the optos appear to blink on and then off, when the actual physical state of the opto is open, suspect an issue with the unregulated 12VDC voltage.

Measure for about 12VDC at TP1 on the power/driver board. If the voltage is significantly below 12VDC (i.e. around 10VDC) then there may be a problem with the bridge rectifier at BR5 or the 15,000uf filter capacitor at C30. Examine the solder joints at C30, especially if that capacitor has been replaced in the past. A damaged through hole may effectively remove the filter cap from the circuit, AC voltage will remain in the power circuit, and the optos will be flakey.

Use your DMM to [http://www.pinwiki.com/wiki/index.php?title=General#Testing_a_Bridge_Rectifier test the bridge rectifier] and to "buzz" between the solder joints at the cap and the appropriate legs of BR5. If this connection is flakey, repair it using a [http://www.pinwiki.com/wiki/index.php?title=General#Repairing_traces_or_creating_a_.22solder_stitch.22 solder stitch] or connect jumpers from the C30 to BR5.

====Other Switch "Jitter" Reasons====

[[File:WPC-C2-Leaking.jpg|300px|thumb|left|A leaky electrolytic cap at C2 caused the "digital" 12V to drop to about 10.5VDC.]] 
The electrolytic cap C2 in the regulated 12VDC circuit leaks quite often, eroding the traces, sometimes severing the connection completely and sometimes reducing the 12VDC power output to something lower. This can wreak havoc on the switch matrix as the regulated 12VDC is used by the LM339 comparators on the MPU board to detect switch closures. Normal cleanup procedures can be used; wipe clean, sand as necessary, retin traces, and replace the cap with a 100uf/35VDC cap (an upgrade).
 

==== Sub-microswitch Issues ====

[[file:WPCMicroSwitch.jpg|300px|thumb|left|A typical micro-switch and wireform.]] 
Some WPC games have an issue with micro-switches that are heat damaged during game assembly. When soldering the wire lead(s) onto the switch, flux leaches into the switch body and, over time, causes the switches to become "sticky".

Game switches from smoky environments often become intermittent or fail. You may be able to repeatedly actuate the switch with your finger and get it to work for a game session, but when you return to the game later, the switch will have failed again.

Tightening the screws too tightly on the switch can damage the switch internals making the switch intermittent.

The switches in games that were played on location for many years simply wear out.

When micro-switches are damaged or past their useful lifetime, there is nothing to repair, adjust, or clean inside them. Simply replace them for reliable operation. You can purchase generic switch bodies and transfer the wireform carefully to the new body.
 

====Switch Wiring====

[[File:SwitchWiringSchematic.jpg|left|thumb|300px|Williams Individual Switch Connection Schematic. The green wire is the switch column. The white wire is the switch row.]] 
Williams switches are always wired the same. The white (plus tracer) colored wire (row) always attaches to the same solder lug as the NON-banded end of the diode. The green (plus tracer) colored wire (column) always attaches to a lug by itself. The banded end of the diode always attaches to a lug by itself. This creates the following circuit, shown schematically at left.
 

The picture gallery below provides an example of correct wiring for different types of switches.

<center>
<gallery widths=300px heights=300px perrow=3 caption="Connections for Various Types of Williams Switches">
File:StandUpSwitchWiring.jpg|<center>Slingshot Switch. The Green and White wires go off-frame to the other slingshot switch in the pair.</center>
File:StandUpSwitchWiring-A.jpg|<center>Standup Target</center>
File:PopBumperSwitchWiring.jpg|<center>Typical Pop Bumper Switch</center>
File:MicroSwitchWiring.jpg|<center>Older Style Micro Switch</center>
File:SubMicroSwitchWiring.jpg|<center>The Pervasive Sub-MicroSwitch</center>
File:ReedSwitchWiring.jpg|<center>Reed Switches, as found in Cactus Canyon and NBA Fastbreak. The diodes are located elsewhere.</center>
</gallery>
</center>
 

===Display problems===
Display problems are usually the result of failing dot matrix displays themselves, flakey ribbon cables or connectors, ribbon cables installed "one row off" (or even one column off), failing high voltage sections of the dot matrix controller board, and rarely logic IC problems on the dot matrix controller board.

Start by checking the easy things first...

#Reseat the narrow ribbon cable between the DMD controller board and the DMD.
#Reseat the wide ribbon cables from the MPU to the DMD controller.
#Ensure each ribbon cable is correctly mated, and not "one row off" or even "one column off".

====Display Panel Problems====
[[File:DMDDisplayFailure.jpg ‎|left|thumb|300px|This DMD Display Panel shows two partial columns out. This failure looks much like a RAM error but the missing pixels are all adjacent. The failure is internal to the DMD display itself. (the entire column that is out is part of normal display test)]] 

The display panel itself may have problems. The glass component has a limited life. The continued electrical discharge releases gases inside the display, which eventually stop the pixels from glowing, and the dots will slowly fade over time. If the voltages are too high, the panel will show sparkles, clouds or ghosting.
 

====DMD Repair Warnings====
'''''Be careful when repairing the DMD Controller Boards, you are dealing with High Voltages when the boards are running'''''.
A good safety measure is to put one hand in a back pocket (or behind your back) when testing voltages.

It's also fairly easy to lift traces on the PCB or ruin the 'through holes' when removing components. If this happens, you may have to check continuity and 'stitch' the component hole with a thin wire strand. It's a good idea to practice on some useless PCB boards first, before taking on the DMD Controller Boards. For details on a stitch see the [[General#Repairing_traces_or_creating_a_.22solder_stitch.22| "How to Stitch"]] section of the Wiki.

High Voltage Repair Kits are sometimes available from various pinball parts suppliers. '''If you do not have decent soldering and de-soldering skills, DMD HV work should be left to a professional.'''

Bally/Williams and Data East have similarities with the 128x32 display and the display itself is interchangeable between manufacturers. DMDs have a limited lifetime and will eventually outgas. Please see the [[Data_East/Sega#Score_Display_Issues | information about outgassing displays]] in the Data East section.

====Testing DMD Controller Power====

[[File:TestingDMDVoltagesAtTheDMDConnector.jpg|300px|thumb|left|Testing DMD Controller voltages at the display. The hand model is Theresa Hibler]] 
After you've checked the easy things, measure the voltages supplied by the DMD controller to the DMD display panel. To test the DMD controller voltages, first open the backbox, and rest the DMD panel face down on the glass. The simplest place to test the voltages provided by the DMD controller is at the display end of the power wire bundle as shown in the picture. SAFETY WARNING: Your left hand should be in your pocket, to avoid a potentially serious shock. We are working with high voltages, so be VERY CAREFUL. Keeping one hand in your pocket is a good practice to follow as it eliminates the easy electric current pathway across your heart. A DMD controller provides enough electric current to kill you! 

[[File:OverDrivenDMDDisplay.jpg|300px|thumb|left|A manifestation of overdriving a DMD with too much voltage.]] 
Most high voltage problems are lack of the proper voltage levels. This results in no display at all. It is possible however, for the high voltage circuitry to fail in such a way that too much voltage is supplied. Or, a game might be jumpered for a lower expected voltage but connected to higher voltage. This manifests as a "plasma" or "cloudy" look on the display, as shown on the left. Note that this looks very much like an outgassed display.

[[image:YT.png]] A YouTube video showing the manifestation of high voltage being too high can be viewed [https://youtu.be/QtSXbrHBnmw?si=3R3tGq2yiUjXLNz_ here].
 

[[File:WPCDotPowerTest.gif|300px|thumb|left|Testing AC input voltages to the DMD Controller board. Click on the image to show the animation. Image provided by Sascha Voksuil aka Pinsider Zaza.]] 
If the display image has a "plasma" affect or a "cloudy" look, it's a good idea to test the input voltage to the DMD Controller board, as depicted in the animated image at left. Nominal voltages are 80VAC and 100VAC. If measurements indicate voltages significantly higher than the nominal voltages, ensure the voltage select jumpers are correct, as discussed [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Primary_Voltage_Selection_Jumpers_at_the_Transformer here].
 

The dot matrix display needs three voltages to operate. Williams designed the DMD controller to drive the the DMD display panel just a bit below its specified voltages, presumably to extend the life of the panel. You can find the specification of a panel [http://www.vishay.com/docs/37006/apd128g.pdf here].

Place the black lead of the DMM under the ground braid in the game's head or use clip leads to secure the black lead to ground. Remember, you are working one-handed, so this becomes a necessity. Place the red lead of your DMM on each of the pins supplying power as shown in the picture. At some point in the production of DMD controllers, Williams changed the Anode and offset voltages from about -124VDC and -112VDC to about -112VDC and -100VDC. As long as there is a 12VDC difference between the Anode and 12VDC offset voltages, your DMD controller is providing correct voltage levels.

{| class="wikitable"
!Function
! J604 Pin 
! Spec 
! nominal WPC voltage 
!Notes
|-
|  Anode || <center>1</center> || <center>-110V</center> || <center>'''-112V'''</center> ||  -124V in early DMD machines
|-
|  12VDC Offset  || <center>2</center> || <center>-98V</center> || <center>'''-100V'''</center> ||  Must be 12V less than anode voltage. Will be about 20V less than anode voltage if display not connected
|-
|  Key || <center>3</center> || || ||
|-
|  Ground || <center>4</center> || || ||
|-
|  Ground || <center>5</center> || || ||
|-
|  5VDC || <center>6</center> || <center>5V</center> || <center>'''5V'''</center> ||
|-
|  12VDC || <center>7</center> || <center>12V</center> || <center>'''12V'''</center> ||
|-
|  Cathode || <center>8</center> || <center>75V</center> || <center>'''62V'''</center> ||  Williams runs this voltage low
|}

If the high voltages are off by more than a few volts, turn the game off, disconnect the power connector at the DMD controller, and test the voltages at the DMD controller male header pins. If the voltages return to nominal WPC voltages, the zener diodes on the DMD controller are probably OK but the resistors and transistors around them are suspect. As shown in the table above, if DMD controller power is not connected to the display, the nominal 12VDC offset will be about 20VDC.

Note that a failing or failed DMD display glass can drag these voltages down. Before you begin any work on the DMD controller board, perform the above test with the DMD display power disconnected. If the voltages return to nominal WPC voltages, it's possible that your display is the culprit. Test the DMD controller with a known good display to isolate the fault to either the DMD controller or the display panel.

[[File:LowHVSupply.jpg|300px|thumb|left|Measuring for 62VDC, and finding only 19.95VDC. The result of this low component of the high voltage trio can be seen in the picture. The manifestation is similar to an outgassed display. The display is showing "FREE PLAY".]] 
For the 62V and -112V circuits Williams used a relatively sophisticated regulator circuit. The problem is, the resistors and diodes dissipate quite a lot of heat. In a warm operating environment, this leads to burned components and circuit boards. The board traces are often weakened. Repair in the area is tricky.

Here's a description of the function of the parts in the -112V circuit.

Q1 is an output buffer. It just follows the voltage set at the top of zener diode D2.
Q2 and Q3 form a constant current 5mA driver for the diode.
Q2 is a current control for D2. By pulling on the base of Q2, the zener current can be reduced to compensate for the diode leaking as it
warms.
Q3 is a current sensor for D2. Note the very low 120 ohm resistor. If D2 passes more than 5mA, Q3 will start to turn on, and reduce the current through the diode by pulling on the base of Q3. So the zener diode always operates at 5mA.

The transistors can be tested in circuit, just watch out for the 120 ohm resistors across the base and emitter of Q3.

The board is subject to transistor shorts, which can also blow out the resistors. Open resistors are a common problem if Q2 and Q3 are bad.

Sometimes when you are missing a voltage, check resistors R3 and R6 (both are 47K 1/2W). Used for switching on the transistors Q2 and Q5
In the same spot are also R12 and R13, which are also 47K 1/2W. Used for discharging the capacitors C4 and C7.
A good thing is to replace all four resistors.
 

====Schematic Diagram for WPC and WPC-95 DMD Controller Board====
Schematic for DMD HV section WPC only (adapted from TZ manual, same as link below):
[http://firepowerpinball.com/2ya/tz/wpc-dmd-hv-tz.pdf WPC DMD HV]

Schematic for DMD HV section WPC95 only (adapted from AFM manual):
[http://firepowerpinball.com/2ya/tz/wpc95-dmd-hv-afm.pdf WPC95 DMD HV]

Here’s a schematic with a list of the parts needed for both WPC and WPC-95 high voltage section repairs. the two boards are similar in the high voltage regulation sections.

[[File:DotControllerHVIcon.jpg|300px|thumb|left|Click on the hyperlink at right for the .pdf of this circuit.]] 
[[media:Wpc-dmd-hv-all.pdf|DMD HV Schematics]]
 

[[File:WPC-089-HV-CheatSheet.jpg|300px|thumb|left|Click on the hyperlink at right for the .pdf HV section cheatsheet.]] 
[[media:WPC-HV-Section.pdf|DMD HV Components]]
 

Another area which will help with troubleshooting the DMD Controller Board can be found in the DE section of the PinWiki (DE copied the Williams board designs), [http://www.pinwiki.com/wiki/index.php?title=Data_East/Sega#PS_520-5047-01_-_High_Voltage_Missing_at_the_DMD_display Data East High Voltage Repair].

The following images of a fairly crispy WPC-089 DMD controller will assist you in ensuring that all traces are repaired.

<center>
<gallery widths=300px heights=200px perrow=2 caption="DMD Controller, High Voltage Section Parts removed">
File:DMDControllerFrontSideTraces.jpg|<center>Front side traces. The yellow line shows where a trace had burned off of this board.</center>
File:DMDControllerRearSideTraces.jpg|<center>Rear side traces.</center>
</gallery>
</center>
 

====DMD Controller High Voltage Repair Kit Parts====
When rebuilding the high voltage DMD controller sections on WPC/WPC-95, there is a list of parts that should normally be replaced because of heat damage. Note that for some components (especially the resistors), they have higher specs than the original components in order to prevent the same heat fatigue issues from reoccurring like with the original components.

'''WPC High Voltage Repair Kit Parts'''
* 1N4759A, 62V, zener diode - D3
* 1N4758A, 56V, zener diode - D4, D5
* 1N4742A, 12V, zener diode - D8, D6
* 1N4004 diode - D7
* 2N5551 (MPSD02) transistor - Q2, Q10
* 2N5401 (MPSD52) transistor - Q4, Q5
* MJE15030 transistor - Q3, Q7
* MJE15031 transistor - Q6
* 120 ohm, 1 watt, resistor - R4, R5
* 47K ohm, 1 watt, resistor - R3, R6, R12, R13
* 56 ohm, 1/4 watt, resistor - R7
* 4.7K ohm, 5 watt, resistor - R8
* 1.8K ohm, 5 watt, resistor - R9
* 120 ohm, 5 watt, resistor - R11
* 220 uF, 160V, axial capacitor - C4, C7 (often left out of repair kits)
* .001 uF, 50V, disc capacitor - C11

'''WPC-95 High Voltage Repair Kit Parts'''
* 1N4759A, 62V, zener diode - D2
* 1N4758A, 56V, zener diode - D1, D18
* 1N4742A, 12V, zener diode - D3, D5
* 1N4004 diode - D4
* 2N5551 (MPSD02) transistor - Q2, Q3
* 2N5401 (MPSD52) transistor - Q4, Q5
* MJE15030 transistor - Q1, Q7
* MJE15031 transistor - Q6
* 120 ohm, 1 watt, resistor - R30, R31
* 47K ohm, 1 watt, resistor - R25, R26, R27, R29
* 56 ohm, 1/4 watt, resistor - R24
* 4.7K ohm, 5 watt, radial resistor - R43
* 1.8K ohm 5 watt, radial resistor - R44
* 120 ohm, 5 watt, radial resistor - R28
* .001 uF, 50V, disc capacitor - C11

=====Step-by-Step Repair Video=====
[[File:DMDController.png|300px|thumb|left]] 
[[image:YT.png]] A video showing the steps necessary to rebuild the high voltage section of the DMD Controller can be found [https://youtu.be/bvTKIsqnC2A here].
 

====Specific Problems & Solutions====

===== Outgassing Displays =====
[[File:OutGassedDMDDisplay.jpg|300px|thumb|left|An "outgassed" display on a Williams FishTales during display test (all pixels should be on except the single vertical line). This display took several minutes to "warm up". The plasma seemed to "float" with various portions at the top of the display appearing dark.]] 
:DMDs will eventually fail. It is important to replace an outgassing display as they place extra strain on the power supply, and will eventually damage the power supply. One sign of an outgassing display is that areas of the display need to 'warm up' before becoming fully bright or that the display will remain completely blank for a few seconds and then appear normal.

Outgassing displays look very much like a display that is being overdriven by too much voltage. The acid test is to measure the high voltage using the technique described later in this section.

Before concluding that the display is outgassing, be sure to measure the high voltages. Excessive high voltage can cause a very similar "plasma" effect.

[[image:YT.png]] A YouTube video showing the manifestation of high voltage being too high can be viewed [https://youtu.be/QtSXbrHBnmw?si=3R3tGq2yiUjXLNz_ here]. 

=====Slow Animations=====
[[File:Pre-DCSSoundCardSolderBridge.jpg|thumb|300px|left|A solder bridge formed on a pre-DCS sound card, affecting speed of display animations.]] 
Slow animations along with sound synced to the animation is a very unusual problem. It is caused by a manufacturing defect in pre-DCS sound boards. As shown at left, an imperfect solder mask led to a solder bridge connecting pins 31 (R/W, read/write) and 34 (FIRQ) on the solder side of the sound board. By connecting the FIRQ signal and the R/W signal, the whole system slows down due to extraneous FIRQ interrupts to the MPU ASIC. The correction for this is straightforward, remove the solder bridge. 

[[File:TZSlowAnimations.jpg|thumb|300px|left|A screen shot from the YouTube video showing slow animations on a Twilight Zone.]] 
[[File:YT.png]] A YouTube video of this problem can be found [http://www.youtube.com/embed/gThgBHVuwio?autoplay=1&rel=0 here].

A PinSide thread leading to this solution can be found [http://pinside.com/pinball/forum/topic/tz-slow-dmd-animations-and-parts-suggestions here]. 

====="SuperScript or SubScript" Characters=====
One of the more interesting display failures is the appearance of characters on some display formats that appear to be shifted up/down 1/2 character or SuperScripted/SubScripted. The cause of this failure is not the display or the dot controller. This failure is caused by a poor connection between the ASIC on the MPU board and it's socket. Reseating the ASIC generally solves this problem. You can "retension" the ASIC leads using this [http://www.greatplainselectronics.com/tech_wms_asics.asp method] provided by Ed at GPE.
<center>
<gallery widths=300px heights=200px perrow=2 caption="Super/Subscripted Characters">
File:DisplaySuperScript.jpg|<center>Superscripted characters...</center>
File:SubscriptNoFear.jpg|<center>No Fear subscripted characters...</center>
File:DisplaySubScript.jpg|<center>Subscripted characters...</center>
</gallery>
</center>
 

===== "Rolling" Horizontal Line on WPC-95 Display =====
This problem resembles an old CRT with a vertical hold problem. A wide horizontal line "rolls" through the display from top to bottom.

This problem is easily rectified by replacing C28 and C42 on the Audio/Video board. The original value of these radial capacitors was 150µF/160V. If the original valued capacitors can't be located, the more common 220µF/160V cap is a good replacement.
 

===== Display is "delayed" after turn on =====
There are cases of import machines incorporating an aftermarket circuit that delays the DMD display from appearing for a fixed amount of time after the game is booted. This was done by some operators so that serial number and location information could not be seen when the machine is powered on, thereby preventing identification of a game and potential sales/operation outside a given geographic area. This circuit will not damage anything but is not standard. More information about this can be found in a [https://groups.google.com/d/topic/rec.games.pinball/Q7_FezXgJ7Y/discussion rec.games.pinball discussion.]
 

====="Snow" on Display=====
"Snow" in this case means rapidly flowing, left to right, "sprays" of dots, almost like can be seen when "spraying" the gun while moving it left to right in Attack from Mars video mode, but much faster.

The cause of this in at least one case was found to be a failed 74HC74 (dual D-Type Flip-Flop) at U4. Pin 5 is the "serial clock" signal to the DMD display. Diode testing indicated that the gate had failed. Replacement of the IC returned the board to normal service.

=====Fuse F601 or F602 blows=====
[[File:WPCDMDControllerBridgeTestingStep1.jpg|300px|thumb|left|Testing the bridge, step 1, red lead on negative.]] 
The WPC DMD controller rectifies AC voltage via two small 1 amp bridge rectifiers. If a bridge shorts, generally the associated fuse will blow. Sometimes the current draw on the other side of the bridge is so great that the fuse blows too. Whatever the reason, the bridge can be easily tested using the same general bridge testing technique.

The pin layout for these small bridges is different from the larger 35A bridges on the power/driver board.

Begin with your DMM set to diode check, and the red probe on the leg marked with a negative sign as shown in the picture at left. Placing the black lead on each of the AC legs in turn should yield a reading between .5 and .7 volts. If your measurements fall outside of this range, replace the bridge.
 
[[File:WPCDMDControllerBridgeTestingStep2.jpg|300px|thumb|left|Testing the bridge, step 2, black lead on positive.]] 
Next, move the black probe to the leg marked with a positive sign as shown in the picture at left. Placing the red lead on each of the AC legs in turn should yield a reading between .5 and .7 volts. If your measurements fall outside of this range, replace the bridge.

[[File:YT.png]] A YouTube video showing how to perform this test can be found [https://www.youtube.com/watch?v=sOlBRkxXKGQ here].
 

[[File:ArcToGroundBlowsF601.jpg|300px|thumb|left|The circled area clearly shows where this trace arced to ground.]] 
Another reason for F601 to blow is shown at left. Some revisions of the DMD Controller routed the trace from one side of BR1's AC power to F601 too close to the lower right screw that secures the board to the backbox ground. If the star washer for this screw bites through the solder mask, this creates a direct path to ground, blowing F601, as it should. This can be corrected by either leaving the screw out, using a nylon washer, or using a nylon screw. Any of these three methods will work fine.
 

===== Heat Damaged Trace Under R9 =====
[[File:WPCDotControllerRoastedTrace.jpg|300px|thumb|left|The burn spot in the center of this picture obliterated the trace that runs from R3/C4 to R11, indicated by the yellow line.]] 
Resistor R9 eats a lot of current and becomes very hot, especially as the associated circuit components age. This damages the trace and PCB beneath it, sometimes to the extent that the trace is severed. "Buzzing" the connection between C4 and R11 is a simple test to ensure continuity of this trace.
 

=====Evenly Spaced Vertical Lines=====
Evenly spaced vertical lines with 8 columns between the lines can indicate a connectivity issue along a ribbon cable. Running the display test may show a "page error" message.

<center>
<gallery widths=350px heights=100px perrow=2>
file:Dmd-vertical-lines-error-2.jpg|Example
File:Dmd-vertical-lines-error-1.jpg|Example during display test
</gallery>
</center> 

First (and with the game turned off), try reseating every the ribbon cable connector along the full length of the ribbon cables that connect to the upper left side of the DMD controller.

[[file:Wpc-reseat-ribbon-cable-connectors.png|thumb|left|350px|Reseat all the ribbon cable connectors for the wide upper ribbon cable]] 

If that doesn't resolve the issue:
* Try replacing the ribbon cable.
* Check for dirty, corroded, or broken connector pins on each of the ribbon cable headers on the DMD controller board, driver board, and MPU.
* Also check for cracked soldier joints on the header pins of each ribbon connector header on the DMD controller board, driver board, and MPU.

=====Failed RAM=====
Most failures of the DMD controller that are not attributed to the high voltage section are caused by failed 6264 static RAM at U24. Since the RAM is very susceptible to electrostatic discharge, they are often damaged by improper handling. Sometimes, they just fail. Failure of this RAM manifests in many ways, including some shown below. At the very end of "display test" the MPU performs a read/write test of the RAM. If the MPU is able to communicate properly with the DMD controller, writing to and reading from the 6264 at U6, then the message "RAM TEST OK" is shown on the display. Any other message indicates a failure of the test. Test failure may be due to the I/O buffers on either the MPU or the DMD controller, the ribbon cable, or the actual RAM.

Note: It appears that Terminator 2, MPU ROM level 8, does not cause the "RAM TEST OK" message to appear. Instead, the screen goes blank for about the time that the message would have been written, and then the test continues.

[[File:YT.png]] A YouTube video of a successful display test can be found [https://www.youtube.com/watch?v=-IK6PZL8I5o here].

=====Page Errors=====
There are 2 pages of 16 memory locations (0 to 15) stored in RAM on the DMD controller board. In the Display diagnostics it will run the page test and display any possible faults on either the low page or the high page (page 1 and 2 respectively) If you are only seeing errors on page 1, look to change out U33, most likely at least one output stuck high (pins 2,7,10,15). Page 2 errors the likely culprit is U35. Both devices are 74LS175. If you are seeing the same errors on both page tests, most likely it will be U16, a 74LS157, which is the A/B selector between the two page addresses.

Page errors will also throw up a RAM address error. The RAM is not at fault, just how it is addressed by the page selectors. It should clear after attending to the above

'''Note:''' the coin door buttons for advance/go back can be held down to quickly move through display test. 

<center>
<gallery widths=350px heights=100px perrow=2 caption="Various display issues resulting from failed 6264 RAM on the WPC-089 DMD Controller board.">
File:BadRAM-1.jpg|<center>Example 1</center>
File:BadRAM-2.jpg|<center>Example 2</center>
File:BadRAM-3.jpg|<center>Example 3</center>
File:BadRAM-4.jpg|<center>Example 4</center>
File:BadRAM-5.jpg|<center>Example 5</center>
File:Blown6264.jpg|<center>This random pattern caused by a blown 6264 RAM. It was blown by sending Flipper Coil power (nominally 70VDC) down the data lines (D0-D7).</center>
File:BadRAM-7.jpg|<center>Example 7</center></gallery>
</center>
 

=====Failures of Various Logic ICs on the DMD Controller=====
The following images represent various failures associated with specific ICs on the DMD Controller board. Of course, the specific way that an IC fails will influence what is displayed. That is, your mileage may vary. 

[[File:WPCDotControllerU1Failure.jpg|400px|thumb|left|]] 
U1 - 74HCT138 - evenly distributed non-moving "snow"
 

The display works in the game and attract-mode but in the test menu it shows nothing. U31 and/or U32 was defective. Think the opposite when the display shows nothing its worth to go into the test because possible it shows only the test.

When the display shows nothing but the data between U31 and U32 seems to be good and also there is data on BD0...BD7 to U29. Test Pin 2 of U29. If there is no clock then follow the line in the schematic to U20. There must be a clock at Pin 1. If no clock coming out from U17 Pin 9 the display shows nothing. After replace U17 the clock signal was there but corrupted from IC U4. After replace U4 too the DMD controller works.

The display shows nothing. The following lines send data to the display SERIAL_DATA SERIAL_CLOCK COLUMN_LATCH ROW-WRITE but ROW-DATA is static High or Low. U13 was defect.

 

===Sound problems===

Before going any further, check all of the basics in the [http://www.pinwiki.com/wiki/index.php?title=General#Basic_Sound_Troubleshooting Basic Sound Troubleshooting] section. 

==== Sound Board Interface Error ====

A "Sound Board Interface" error occurs when the MPU board can not communicate properly with the sound board at boot up. There could be several reasons for this problem.

#Ribbon connector not properly seated. The ribbon to the sound board(s) originates at J202 on the MPU board, goes to the FlipTronics board, then to the sound board (whether pre-DCS or DCS), then on to the DMD controller board.
#Failed ribbon cable. Due to over-flexing, the ribbon may have failed.
#Mismatched ROMs between the MPU and sound board. This isn't as big of an issue as with Data East games, but updating the game ROM to a newer version while leaving the sound ROMs at an older, even prototype version, could cause this problem.
#Solder bridges, or corrosion under the ribbon connector.
#Failed I/O buffer ICs on either the sound board or on the MPU board

On '''DCS sound boards''', U18 buffers data '''from''' the MPU. U19 buffers data '''to''' the MPU. Testing these ICs using the [http://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit this method] should yield similar results to the values listed below. Note that this test method can't identify either a good or a bad integrated circuit with 100% certainty but using this test is preferable to removing chips unnecessarily. These readings were taken using a Fluke 179 DMM. Different meters, different manufacturers chips, and even individual variation in manufacture will probably cause your readings to be slightly different, yet consistently different. i.e. If the table shows .657 and your meter yields .630, then every pin listed at .657 should read close to .630 with your meter.

Probe pin 10 with the DMM red lead. Probe each of the other pins with the black lead.

{| class="wikitable"
! Pin 
! Diode Test Value U18 
! Diode Test Value U19 

|-
| <center> 1 </center> || <center>.583</center> || <center>.580</center>
|-
| <center> 2 </center> || <center>.519</center> || <center>.659</center>
|-
| <center> 3 </center> || <center>.657</center> || <center>.510</center>
|-
| <center> 4 </center> || <center>.657</center> || <center>.516</center>
|-
| <center> 5 </center> || <center>.511</center> || <center>.656</center>
|-
| <center> 6 </center> || <center>.511</center> || <center>.656</center>
|-
| <center> 7 </center> || <center>.657</center> || <center>.510</center>
|-
| <center> 8 </center> || <center>.657</center> || <center>.510</center>
|-
| <center> 9 </center> || <center>.511</center> || <center>.656</center>
|-
| <center> 10 </center> || <center>Red Lead</center> || <center>Red Lead</center>
|-
| <center> 11 </center> || <center>.580</center> || <center>.580</center>
|-
| <center> 12 </center> || <center>.510</center> || <center>.657</center>
|-
| <center> 13 </center> || <center>.657</center> || <center>.518</center>
|-
| <center> 14 </center> || <center>.657</center> || <center>.516</center>
|-
| <center> 15 </center> || <center>.519</center> || <center>.656</center>
|-
| <center> 16 </center> || <center>.517</center> || <center>.578</center>
|-
| <center> 17 </center> || <center>.657</center> || <center>.517</center>
|-
| <center> 18 </center> || <center>.578</center> || <center>.509</center>
|-
| <center> 19 </center> || <center>.517</center> || <center>.657</center>
|-
| <center> 20 </center> || <center>.398</center> || <center>.398</center>
|}

[[File:WPCSoundBoardInterfaceErrorCorrosion.jpg|300px|thumb|left|Corrosion in the area of a critical signal caused a "Sound Board Interface Error".]] 
The root cause of a "Sound Board Interface Error" on a Star Trek:The Next Generation game is shown at left. The corrosion on the trace leading to pin 28, created a conductive bridge to pin 29, which is a critical signal to the sound board (WDEN).
 

[[File:WPCpreDCSSoundBoardSolderBridgeatU16.jpg|300px|thumb|left|A solder bridge at the circled location (U16), connecting pin 7 of the IC (ground) to the via and hence connecting pin 2 to ground, manifested as a "Sound Board Interface Error".]] 
Another physical PCB problem pictured at left (but repaired), caused a "Sound Board Interface Error". The sounds on this board operated fine since the error was in the hardware that talks back to the MPU.

A similar problem can be the cut component lead just left above the yellow circle. If it is bend towards the printed trace and making contact, it can also manifest itself as the "Sound Board Interface Error".
 

==== Shorting the Speaker Leads or a Shorted Speaker ====

[[File:BlownTDA2030.jpg‎|300px|thumb|left|Clearly, a major malfunction.]] 
A blown sound amp will cause a loud buzz when the game is powered on. Generally, amps blow due to reduced impedance (aka resistance, ohms) in the speaker(s). If a speaker shorts, the associated amp(s) will blow. Or, if the drive connection (not ground) to a speaker breaks free of the speaker connection lug and touches ground with the power on, the associated amp(s) will blow. Note that the speaker metal housing is connected to ground.

The image at left shows two amps from the same WPC-95 AV board that were blown when the non-ground speaker wire broke free and touched the speaker housing. It is good practice to solder the speaker wires onto the speaker connection lugs to prevent this from every happening.

Diode testing is an effective method of determining that an amp is blown. Place the red lead of your DMM on the center leg of the amp and test each of the remaining four legs. Compare results to a known good amp of the same type. Generally, readings between .5 and .8 should be observed. 

==== Lowering the Minimum Volume ====
By default the game volume can be set no lower than '8' to prevent an operator from setting the volume too low. This can be overridden by entering the adjustments menu and setting Adjustment 1.28 (Minimum Volume Override) to yes. You can now set the volume as low as you like.

====High Frequency Sound Only====
This applies to pre-DCS and DCS sound boards. This has not been proven to apply to WPC-95 AV boards, yet.

There is a situation where only the tweeter / high frequency sound can only be heard. This will result in the game sounding much quieter than usual. Most speaker systems are parallel circuits. However, the woofer on a pre-DCS sound system is in series with the midrange speaker. The high frequency speaker is in a parallel circuit to the mid and low range speakers. If there is no sound from the woofer in the bottom of the cabinet, there will be no midrange from the speaker panel.

First, make certain that the speaker output wiring from the sound board is connected correctly. Also, there is a bullet connection located inline which must be connected. This bullet connections ties the low and midrange speakers in series. Finally, check the connections at the woofer in the bottom of the cabinet to make certain the female spade connectors are secured to the speaker terminals. If all connections are secure, there is a chance that the woofer speaker is blown.

====Pre-DCS Sound Board Issues====

The blue Philips 47µF 35v axial electrolytic capacitors on these sound boards are prone to failure, often testing with no capacitance or extremely high equivalent series resistance.

===== Schematic for preDCS Sound Board =====
[[Image:LM1875.jpg ‎|300px|thumb|left|]] 
Schematics for the preDCS sound board can be found [https://www.pinwiki.com/wiki/images/1/1d/PreDCS.pdf here].
 

===== Power on Sound Tones (Bongs) =====

After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs. Instances have occurred where the U9 RAM chip had failed, but only 1 "bong" was sounded. In this case, other than the bong, the board produced no sound at all. This calls into question the robustness of the power on RAM test.

Pre-DCS Sound Board Games.
*1 - No issues...enjoy a game.
*2 - U9 RAM failure.
*3 - U18 ROM failure.
*4 - U15 ROM failure.
*5 - U14 ROM failure.

=====No Sound at all=====
[[File:SoundBoardU9RAMError.jpg |thumb|left|500px| Infrequently seen preDCS sound board RAM error message. Image courtesy of PinSider "DownSouthPinball"]]
The highest probability reason for the complete lack of sound is connections to the speakers. The IDC connectors at J504 and J505 carry the sound to all speakers in the game. Since the speakers are connected in series on a pre-DCS game, any break in the speaker signal loop will cause loss of all sound. First check the small gauge wires at connectors J504 and J505. Since they are IDC connectors, they are prone to breaking free from the connector. Next ensure that all speaker connections are solid.

It is possible for a speaker to fail, commonly called "blown". You can test a speaker by applying anything from an AA battery to a 9V battery to the speaker terminals. You should see the speaker cone react when the battery is touched to the terminals.

Another possible cause of no sound at all is a failed 6264 RAM chip at U9. It is possible for the RAM to be failed, the board passes the power on self test, a single "bong" is heard, no convenient message as shown at left appears, and yet the board produces no other sound at all.
 

In one case, while the amplifier was clearly working as it would "buzz" at power on, one of the four diodes configured to rectify AC power into DC power had shorted. This cascaded into a failure of the 7912 negative 12V regulator which was delivering about -5VDC. Further analysis showed that both TL084 operational amplifiers and the TL082 operational amplifier had failed. After replacing the TL084 operational amplifiers, most sound returned but sound from the "DAC lane" was still missing, which indicated the TL082 operational amplifier had failed. Replacement of that operational amplifier returned the sound board to proper operation.

[[image:YT.png]] A YouTube video demonstrating this failure and the repair can be found [https://youtu.be/-pQ_Zlsmq38 here]

In the video, which uses Addams Family ROMs, sound 7 within sound test, "Thing Multiball" is clearly missing the classic two finger snaps that are contributed to the sound mix by the AD7524 DAC.

Another known DAC channel contribution is in The Getaway: High Speed 2, sound 3 within sound test, "Super Jackpot", the drumming that can be heard at the start of the clip. Interestingly, if that sound test is set to repeat, the drumming sound is omitted entirely. This isn't a DAC or other sound board failure. The omission is caused by a software coding error where the first part of the "compound sound" is never called for.
 

=====Unbalanced Sound=====
[[Image:WMSpreDCSR23R24.jpg ‎|300px|thumb|left|56Kohm Resistors at R23 and R24 for games Hot Shots through Addams Family Gold (last preDCS game).]]
[[Image:WMSpreDCSSoundR23R24.jpg ‎|300px|thumb|right|150Kohm Resistors at R23 and R24 for games Funhouse through Party Zone.]] 
Pre-DCS sound boards are not 100% interchangeable across games without modification. Games from Funhouse to Party Zone (including Funhouse, Harley Davidson, Bride of Pinbot, Slugfest, Gilligan's Island, Terminator 2, Hurricane, and Party Zone) use different resistor values at R23/R24 than the remaining games that used the pre-DCS sound board (games from Hot Shots basketball through The Addams Family Gold). If you find the sound "unbalanced" between background sounds and voices, for instance, check the following resistor values.
 
R23/R24 values for... 
::Funhouse through Party Zone - 150Kohms (color bands brown, green, yellow, gold) 
::Hot Shots through TAFG - 56Kohms (color bands green, blue, orange, gold) 

Note that the resistor value indicated in the schematics for pre-DCS sound boards at R22 and R25 are wrong. The schematics indicate 150K ohms. The correct value is 120K ohms.
 

=====No Sound or Low Volume Sound from Right Speaker=====
[[Image:WPCSpeakerAndCap.jpg|300px|thumb|left|The 10uf non-polarized capacitor on the "Tweeter" (right) speaker of a pre-DCS game (Twilight Zone).]] 
As Joe "Tony" Dziedzic discusses [http://www.dziedzic.us/wpc_speaker_sound_info.html here], "the back box speakers are wired in parallel, with a 10uf non-polarized capacitor in series with the right speaker (the tweeter). The capacitor is used to block lower frequency sounds from being reproduced by the speaker. Technically, the capacitor forms a first-order high-pass filter with a crossover frequency of 4000 Hertz. This configuration presents an effective impedance of around 4 ohms."

If the 10uf capacitor fails "open", then the signal to the speaker is open and the speaker will remain silent.

The repair is simple...replace the capacitor.
 

=====Distorted or slightly "off" sounds=====
[[Image:PreDCSSoundBoardC38NotStuffed.jpg|300px|thumb|left|C38 is not stuffed on some pre-DCS sound boards.]] 
The pre-DCS sound board uses 47µF capacitors as filters in the sound circuit; C15, C36, and C38. If one or more of these caps fail, certain sounds may not be as loud or as clear as intended. The game will just sound "off" with perhaps slightly unbalanced sounds. An amazingly high percentage of these caps fail. It is recommended that if your sounds are a bit "off" that you replace all of these caps.

'''Note:''' as shown at left, C38 is sometimes not stuffed at the factory. It appears that audio channel 1 and channel 2 (in C38s path) from the Yamaha YM3012 are redundant, making this cap unnecessary.
 

[[Image:preDCSSoundBoardCapComparison.jpg|300px|thumb|left|C49, implemented in two different ways on the pre-DCS sound board.]] 
Also, some pre-DCS sound boards looked to have been "hacked" to add a ceramic capacitor just below the clock crystal X1. This is not in fact a hack. It appears to "fix" the omission of C49 on some versions of the PCB. C49 is located at the edge of the board, just above the crystal.
 

=====Static or Scratchy and Low Volume Sound=====
[[Image:WMSpreDCSSoundC21.jpg|300px|thumb|left|C21, a 10uf tantalum capacitor, sometimes fails causing static or scratchy sound.]] 
The entire audio stream passes through a 10uf tantalum capacitor at C21 just before the MC3340 audio attenuator. While extremely rare, this capacitor can partially fail and cause static or scratchy audio in ALL (CVSD, FM Synthesizers, and the DAC) channels. The audio volume may vary from normal to very low or no volume.
 

=====Popping, Scratchy Sound, Very Hot LM1875 Heat Sink, or Shorted Speakers=====
[[File:PreDCSSoundCaps.png|300px|thumb|left|Ceramic, electrolytic, and Tantalum caps to suspect with this behavior. Image courtesy of Chris Hibler.]] 
Sometimes, the tantalum/ceramic caps in the amp circuit fail too. This can result in too much AC "ripple" feeding the amp as well as DC output to the speakers, which they do not like. The following components are all suspect...

*C20 (10µF, 20V tantalum)
*C46 and C47 (both 1µF, 35V tantalum)
*C22 (22µF, 35v electrolytic)
*C23 (.22µF, 10V, ceramic)

Normally, the positive side of the tantalum cap at C26 will measure about 50mv of AC referenced to game ground. Anything more indicates a problem with these tantalum caps. You will also be able to measure DC voltage across the speaker outputs. There should normally be no DC voltage across the speaker outputs.

The LM1875 may also run very hot. Normally, you can grasp the heat sink without burning your hand. It will be hot, but not so hot that you can not squeeze it or grasp it very long. '''Note:''' this assumes that the volume is set to about 8. Setting the volume to 18 will require the heat sink to dissipate more heat. The heat sink will be too hot to grasp (for very long). If at "normal" volume levels and the heat sink is so hot that you can not grip it, failing tantalum caps should be suspected. If after replacing the tantalum caps the popping and scratchiness persist, the LM1875 amp may have been damaged.
 

=====Volume Not Adjustable and/or Stuck at Low Volume=====
This problem manifests as a very low volume from the speakers, equivalent to the lowest sound level setting. The volume setting may be adjusted from the coin door, and the DMD volume "thermometer" will move normally, but the speaker volume will not change. While the cause of this issue could be a failed digital POT as discussed [http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Volume_Suddenly_at_Maximum here], a failed MC3340 electronic attenuator may also be the cause. You may be able to identify the MC3340 as the problem by comparing "diode test" results with a known good MC3340.

In one such case, pins 7 and 8 of the device where shorted together, causing the symptoms described. The failed MC3340 may also have caused the amp to become very hot, but this has not been conclusively proven.

Take care to ensure the MC3340 is actually at fault as this obsolete part is pricey and hard to find.

=====Volume at zero but still audible=====
If you set the volume to zero via the coin door buttons and you can still clearly hear it, there is a good chance that the axial capcitor C18 (47 µF, 10 V) is bad. If this capacitor fails, the output voltage of the digital pot U5 (X9503) might not go high enough to silence the sound completely. When the volume is set to zero, a voltage of approx. 3.5 V should be measured at U5 pin 7 or jumper W9 or U2 pin 2. Lower voltage will result in clearly audible sound even when set to zero.

=====Wrong sounds being played=====
[[File:FunHouseSoundTest.jpg|300px|thumb|right|An obnoxious dummy enquiring about what just happened.]]
Generally, this problem boils down to a communication problem between the MPU and the sound board. Possible failure points are:

*Ribbon cables
*Male header pins on both MPU and sound board
*74LS374 data buffer ICs on the sound board used to communicate between the MPU and the sound board.
*Rarely, the data output buffer ICs on the MPU board used to communicate with the FlipTronics, Sound, and DMD Controller boards.
*Rarely, a failed 6264 RAM can cause this. The RAM is "tested" by the MPU. Sometimes the test will pass, no message is displayed, and yet, the part fails during game play. Odd...I know.

[[image:YT.png]] A YouTube video documenting the behavior of a failed preDCS RAM chip at U9 can be viewed [https://youtu.be/B3pWA7eg4Kg here].
 

=====Volume Suddenly at Maximum=====

If the volume suddenly jumps to full volume and control of the volume via the coin door buttons does not work, check C18, a 47µF 35v axial electrolytic capacitor. The blue Philips capacitors on these sound boards are prone to failure and can cause this issue if bad. If that does not solve the problem there is a good chance that the digital POT (volume control) on the sound board has failed. The part is located at U5 and is an X9503. The X9503 is obsolete but it's successor the X9C503 works fine here.

=====Blown 1uF or 10uF Tantalum Capacitor=====
[[Image:WPCpreDCSBlownTantalumCap.jpg|300px|thumb|left|C46 blew up and burned quite spectacularly on this pre-DCS sound board.]]
[[Image:Wpc_pre-dcs_cap-failure-c28.jpg|300px|thumb|right|C28 failed on this pre-DCS sound board.]] 
The pre-DCS sound board uses 1uf tantalum caps in the amp circuit. Sometimes, for no good reason than simply being old, one of these caps will explode and burst into flames at game power on. C46 on the board shown at left did just that. In the great majority of instances, simply replacing the cap returns the board to service. This "burning into flames" can also happen to the +12V and -12V section with C26 and C28.

[[Image:BlownTantalum.jpg|300px|thumb|left|Closeup of blown 1uf cap on a pre-DCS sound board. The actual size of the cap is less than one inch in length]]
When the 1uF tantalum at C27 or C29 shorts internally, it will cause the +12V or -12V to disappear. The LM7812 (U4) or LM7912 (U3) will run very hot. The tantalum draws all the current. The LM7812 and LM7912 have a limit of 1 Amp. The voltage will drop to zero when this happens, leaving the amplifier without power.

Other tantalum caps have been documented to explosively fail, including C28 and C47.

A tantalum capacitor can be tested by desoldering one leg and using a DMM (in diode check) to check for a short. Simply replacing the tantalum will solve the problem.

A contributing factor to these explosive failures was that the voltage rating on the capacitors that were used was too close to the operating voltage running through them (undersized components were typically used as a cost saving measure). As a general rule of thumb, the operating voltage should be 50% of the voltage rating of the tantalum capacitors. So, for a 12V circuit, at least a 25V capacitor should be used; a 50V minimum rating would be better.

All the tantalum capacitors used on the pre-DCS sound board are listed below:
* C20,C21: 10uF axial tantalum capacitor (original rating was 10V; use at least 35v instead).
* C26,C27,C28,C29,C37,C46,C47,C48: 1uF axial tantalum capacitor (original rating was 35V; use at least 50v instead).

Note that the tapered end is the positive side and also has a "+" symbol near it (however, with a burnt part, this might be impossible to see). Since the board was not silkscreened with any indications of component polarity, make note of the direction on the original part before removing it. 

[[Image:Wpc_pre-dcs_tantalum-cap-polarity.jpg|500px|thumb|center|Diagram showing the tantalum capacitor locations and polarity]] 

After replacing one blown tantalum capacitor, it is possible that a second power up might blow a different one. Therefore, it might be a good idea to preemptively replace all the tantalum capacitors, especially if one has already experienced an explosive failure.
 

[[File:Failed1ufTantalumCap.jpg|300px|thumb|left|Another failed 1uf tantalum capacitor.]]
[[File:ReplacementCapForTantalum.jpg |300px|thumb|right|The replacement 1uf electrolytic capacitor installed, with the lead insulated to prevent the unlikely short to the heat sink.]] 
The tantalum caps on this board can be replaced with the same rated (1uf) electrolytic caps. The two caps adjacent to the large heat sink need to be positioned to allow space for the large 4700uf caps also adjacent to the large heat sink.
 

=====Sound Is Very Faint Even at Maximum Volume (CVSD Failure)=====
[[Image:55536-CVSD.jpg|300px|thumb|right|Two hard to find 55536 CVSD ICs.]] 
While most techs would suspect either a TL082 or a TL084 amplifier (on a pre-DCS sound board) or a 1458 amplifier (on a System 11 MPU) as the cause of this issue, the 55516/55532/55536/55564 CVSD (Continuously Variable Slope Delta-Modulator) can also cause this issue.

Isolation to the CVSD is pretty simple.

*Place the game into sound test.
*Use an oscilloscope to probe pins 9 and 12. A scope must be used since the signals are too subtle for a logic probe to detect.
*Pin 9 is a clock signal.
*Pin 12 is a data signal.

When the game is making sounds that use the CVSD (generally voice calls), both pin 9 and pin 12 should show "off nominal" signals. If the CVSD is working correctly, the output at pin 3 should be showing signal also. If pin 3 is not showing signal, then the CVSD has failed.
 

[[Image:CVSDReplacementFront.jpg|300px|thumb|left|A "daughter card" used to replace the 55536 CVSD (front).]]
[[Image:CVSDReplacementBack.jpg|300px|thumb|right|A "daughter card" used to replace the 55536 CVSD (rear).]]
During the run of the pre-DCS sound board, it is suspected that the 55536 CVSD part (and it's close cousins) was becoming hard/expensive to acquire. Williams created a "daughter card" to use in lieu of the CVSD. The daughter card used an MC3417 CVSD along with additional "tuning" resistors and capacitors. The sound quality result is indistinguishable from a 55536. Williams used a closed frame machine pin socket to accept the daughter card. The "chip notch" should be oriented just as you would the CVSD. That is, more of the card will be south of the chip socket than north of it.

While it might seem like a good idea to duplicate the design of this Williams card (part number 5768-14714-00) to replace the even harder to find 55536, the main part used, the MC3417, is equally hard to find today.

[[File:YT.png]] Jeri Ellsworth reverse engineered the 55564 (55536 equivalent) and posted [https://www.youtube.com/watch?v=2FRGwuxFDE4 this video] in October, 2011. She makes it seem "intuitively obvious to even the most casual observer"...
 

=====Sound Lane Reference=====
[[File:SoundScopeTrace.jpg ‎‎|300px|thumb|right|"White Noise" scope trace]]
That is, which sounds use which of the 4 sound "lanes" on the preDCS sound board?

The preDCS sound board produces sounds via one or more sound lane which are:
*YM2151/YM3012 FM Synthesis (2 lanes)
*AD7524 DAC
*55536 CVSD (continuously variable slope delta)

Using Adddams Family game and sound ROM (U18), in test mode, 36 sounds are played.

Sounds 1-16 use both the DAC and the Yamaha synthesizers.
Sounds 17-36 use the CVSD.

[[image:YT.png]] A video demonstrating the use of an oscilloscope for detecting a properly working sound lane can be found [https://youtu.be/vpBHrccwPbc here].
 

====DCS Sound Board Issues====

The DCS sound board was used in 18 games including:

*Indiana Jones: the Pinball Adventure
*Judge Dredd
*Star Trek: The Next Generation
*Demolition Man
*Popeye Saves the Earth
*World Cup Soccer
*The Pinball Circus
*The Flintstones
*Corvette
*Red & Ted's Road Show
*The Shadow
*Dirty Harry
*Theatre of Magic
*No Fear: Dangerous Sports
*Indianapolis 500
*Johnny Mnemonic
*WHO Dunnit
*Jack*Bot

===== Power on Sound Tones (Bongs) =====

After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs.

DCS Sound Board Games.
*1 - No issues...enjoy a game.
*2 - U2 ROM failure.
*3 - U3 ROM failure.
*4 - U4 ROM failure.
*5 - U5 ROM failure.
*6 - U6 ROM failure.
*7 - U7 ROM failure.
*8 - U8 ROM failure.
*9 - U9 ROM failure.
*10 - U10-U12 RAM error. Not always identified from the main CPU board program. DCS sound board RAM failures are indicated by a message on the display, "U10-U12 RAM error".

=====Very Loud Humming at Power On=====
The DCS sound board uses two 10,000µF caps at location C20 and C21 to smooth rectified AC power. The negative side of C21 and the positive side of C20 are connected to analog ground at header J4, pins 6 and 7. This connection is fragile. If the game hums really loudly, immediately at power on, test for continuity between these points as shown in the pictures below. Often this loud hum is diagnosed as a failing cap when the real problem is simply a fractured trace. If the caps have been replaced previously, there is a good chance that the PCB through holes have been damaged.

<center>
<gallery widths=300px heights=300px perrow=3 caption="DCS Sound Board Filter Capacitor Connections. Continuity is shown as a zero ohm connection.">
File:DCSCapThroughHoleBungled.jpg|<center>The remains of through holes heinously ripped from a DCS sound board PCB. These "brown donuts" are still attached to the 10,000uf filter capacitor.</center>
File:DCSCapConnection1.jpg|<center>The first of two tests ensuring continuity between the filter capacitors and analog ground.</center>
File:DCSCapConnection2.jpg|<center>The second of two tests ensuring continuity between the filter capacitors and analog ground.</center>
</gallery>
</center>
 

=====U10-12 RAM ERROR (10 Bongs)=====
[[File:WPC95U10U12Message.jpg|300px|thumb|left|A DCS game boot time RAM error message, accompanied by 10 very annoying bongs.]]
Replacement RAM ICs for the DCS sound board are becoming harder to find. The board uses three, 2Kb skinny dip 6116 cache rams with an access time of 35nS or better. These are obsolete and long gone. The good news is that the board has jumpers for 6264 type 8Kb cache rams. Jumper W4 is installed for 2Kb rams. Jumper W4 should be removed and jumper W5 installed to use 8Kb rams. All RAM ICs need to be replaced at the same time for this configuration to work.

A relatively inexpensive, and still in production replacement, is the IDT 7164S20TPG.

RAM testers are not able to detect chips that do not meet the speed requirement. While slower RAM may pass chip test, it may fail on the board and cause the "10 bongs" error indication.

[[image:YT.png]] A YouTube video showing a DCS sound board and the "10 bongs" error can be found [https://youtu.be/jX0yLXSeEto here]
 

===== Muffled Sound and Speech/No Sound =====
[[File:DCSSoundBoardCaps.jpg|300px|thumb|left|C32 and C41, both electrolytic caps, are in series in the sound amplification circuit of the DCS sound board.]] 
Muffled audio can be caused by failure of the two 1uf/63V electrolytic capacitors that are in the audio circuit for each amplifier. Simply replacing them may clean up the audio. A typical 1uf/50V axial electrolytic capacitor will work fine.
 
It is also possible for one or both of these capacitors to fail completely open. In that case, no sound at all will come out of that capacitor's channel since they are in series with amplifier (C32 for the cabinet speaker and C41 for the backbox speakers.) Replacing the appropriate capacitor can restore sound to the silenced channel.
 

===== Volume Jumps to Max on Indiana Jones=====

The DCS sound board software has a bug in early versions that cause this issue. 
Updating ROM S2 on the DCS sound board to the latest ROM revision will correct this.

===== Scratchy Audio or mumbled speech =====

[[File:DCSSoundBoardCeramicCaps.jpg|300px|thumb|left|C37 and C45, both ceramic caps, sometimes cause scratchy audio.]] 
During production of WPC-95 games, Williams removed two small ceramic caps (C47 and C51) from the A/V board to clean up the sound. This update should also be applied to the DCS sound board. On the DCS board C37 and C45 are the equivalent caps to be removed. Simply clip the caps from the board. You do not need to desolder them. This cleans up the sound and speech on some games like Demo Man quite well.
 

===== Notes regarding the TL084 part =====
The following was authored by Ed Krzycki, in a PinSide post [https://pinside.com/pinball/forum/topic/dcs-tl084cn-vs-tl084acn#post-7091884 here]. 
The suffix on these parts indicates how far off the output 'offset' can be. The offset is an added bias to the output voltage that is typically undesired in an audio device.

The offset is measured in millivolts. Higher the value, the more offset and the output is less 'true' to original input.

*TL084CN = worst case offset (standard part) = 20mV
*TL084ACN = 7.5mV
*TL084BCN = 5mV
*TL084IN = 9mV but has a much wider temperature 'industrial' temperature range.

The TL084BCN is better than the TL084ACN and the TL084ACN is better than the TL084CN. 
The TL084IN is the same as the TL084ACN when used at normal room temperature. But the TL084IN version can withstand higher temps.

Any introduced DC voltage offset is typically removed if there is a capacitor in series with the output (common) but can still add a bit of distortion. Keep in mind that pinball sound boards are not exactly high end audio equipment so any of these TL084 parts will work with no noticeable difference. There are other components in the design that are far greater at introducing noise into the sound.
 

===== DCS Audio Format Technical Reference =====
A very informative, very detailed look at the DCS sound board audio formats etc., authored by Michael Roberts, can be found [https://www.pinwiki.com/wiki/images/a/aa/DCS_Audio_Format_Technical_Reference.pdf here].

====WPC-95 A/V Board Sound Issues====
[[File:WPCAVBoardASIC.jpg|300px|thumb|right|The location of the 120 pin Quad Flat Pack ASIC with ASIC neatly removed]]
The WPC-95 A/V Board was introduced, along with the WPC-95 system, with Congo and was used through the end of the WPC game system run. WPC-95 games using the A/B Board are listed below. The sound ROM part number is shown in parenthesis.

*Congo (5343-50050)
*Attack from Mars (5343-50041)
*Safe Cracker (5343-90003)
*Ticket Tac Toe (not a pinball)
*Tales of the Arabian Nights (5343-50047)
*Scared Stiff (5341-15191)
*Junk Yard (5341-15403)
*NBA Fastbreak (5341-15418)
*Medieval Madness (5341-15451)
*Cirqus Voltaire (5341-15584)
*No Good Gofers (5341-15591)
*The Champion Pub (5341-15703)
*Monster Bash (5341-15931)
*Cactus Canyon (5341-15191)

Always check the speaker connections to the A/V board (J504 and J505) and the wiring at the speakers before assuming there is a problem with the board. The speakers themselves can go bad; you can do a quick "click test" with a D-cell battery and a set of jumper leads to rule out dead speakers. Disconnect the speaker connections at the A/V board and connect your battery jumper leads to the pairs of wires in the J504 and J505 connectors; you should hear a click from the speaker if it is good. If you don't hear the click try the connection at the speaker itself to rule out wiring issues.

The analog output of the A/V board feeds into a TLO84 op-amp (U1) that is configured as a pair of low-pass and high-pass filters; these are used to separate the low-frequency sounds (destined for the cabinet speaker) and the high-frequency sounds (destined for the back box speakers). These two channels - signified on the schematic as AUDIO_R (cabinet) and AUDIO_L (back box) feed into a pair of TDA2030AV amplifiers; U5 drives the back box speakers and U6 drives the cabinet speaker.

The outputs of U1B and U1C (pins 7 & 8) can be briefly connected with a jumper lead to help narrow down issues when one of the two channels is not working or has weak/distorted output. When the two pins are jumpered you should be able to hear approximately the same level of sound from the cabinet and back box speakers. (Use the T.7 diagnostic test to play sound clips for the game during your testing.)

===== On Board Voltage Regulation =====
The WPC-95 A/V Board "digital" side is powered by the same 5VDC that is regulated by the power/driver board. The "analog" side of the A/V board, specifically the two TL084s and the AD1851 D-to-A converter, all use +5VDC and -5VDC that is regulated by the 78L05 and 79L05 respectively. Four rectifying diodes provide about +/- 17VDC to these regulators. If the sound is low or scratchy, check these two voltages first. Both +5VDC and -5VDC can be easily measured at pins 4 and 11 of either TL084.

===== Power on Sound Tones (Bongs) =====

After a successful boot, the game should make a single "bong" sound. The game provides a sound board problem indication with the following number of bongs. Note that if more than one sound ROM exhibits a checksum error, only the first failed ROM will be indicated. Once that failed ROM is replaced, the next failed ROM will be indicated upon subsequent boots.

[[File:SoundROMChecksumError.jpg|300px|thumb|Right|WPC-95 boot time Sound Board ROM error message, accompanied by three bongs.]]

Audio/Video Board Games (WPC-95).
*1 - No issues...enjoy a game.
*2 - S2 ROM failure. Note: Two bongs also occur if jumper W3 is IN on the MPU board, and the installed RAM size is 6264. If an NVRAM was just installed, check this jumper. See the section on [[Williams_WPC#Jumpers.2C_RAM_and_ROM_size | jumpers]].
*3 - S3 ROM failure.
*4 - S4 ROM failure.
*5 - S5 ROM failure.
*6 - S6 ROM failure.
*7 - S7 ROM failure.
*10 - U9, U10, or U11 RAM failure (see below)

[[File:WPC95U9-U11Error.jpg|300px|thumb|left|WPC-95 boot time RAM error message, accompanied by 10 very annoying bongs.]]
[[File:WPC95U10U12Message.jpg|300px|thumb|right|WPC-95 boot time RAM error message, accompanied by 10 very annoying bongs.]] 
A/V sound board RAM failures are indicated by a message on the display, either "U9-U11 RAM error" or "U10-U12 RAM error". This is apparently game software dependent. A/V RAM are, in fact, U9-U11. Apparently, this message wasn't updated in some of the software with the introduction of the A/V board.

[[image:YT.png]] A Youtube video showing "10 Bongs" can be found [https://youtu.be/UFSEkHRaVvs?si=p66fWpdnTozts93o here.]
 

[[File:AligningSockets.jpg ‎|300px|thumb|left|A neat trick to ensure two sockets are aligned]] 
Should it become necessary to replace one of the skinny DIP RAM chips, in lieu of a 28 pin skinny DIP socket, two 14 pin sockets may be used. Align the sockets using the trick shown here.

Sometimes it is obvious to see that the text on one of the ram ICs is darker than the other chips. This might be a clear sign of an overloaded chip. When you replace these ICs make sure you replace them as a triplet and with (preferably) identical ICs. They should all be rated the same access time since the SRAM is treated as a vector and not individual bytes. Think RAID. In place of the 61C64 sram ICs you can also use th 61C256 chips. Those ICs should be 35ns access time at a minimum.
 

===== Loss of One Channel =====

[[File:WPC95AVBoardSoundIssue.jpg|300px|thumb|left|C38 and C39, which can cause loss of a single channel]] 

If one channel is out or weak/distorted try the jumper at U1 pins 7 & 8 noted above. If no change is detected in the sound output it is likely the associated TDA2030AV amplifier (U5 or U6) has failed. Before replacing the amplifier jumper a 1 MFD 63 volt capacitor across C38 and C39 in turn (observe polarity!) to rule out a defective coupling capacitor. If jumpering pins 7 & 8 of U1 significantly improves the sound levels it is likely that U1 itself has failed.
 

===== Scratchy Audio =====

[[File:AVBoardCapsRemoved.jpg|300px|thumb|left|A later production Williams WPC-95 AV Board, with C47 and C51 intentionally unstuffed at the factory]] 
Williams removed two small ceramic caps (C47, C51, pictured at left) later in the production run of AV boards. If your game's audio is just a bit scratchy, and these caps have not been removed, you may be able to improve audio quality by removing them. Simply clip both sides of the cap. There is no real need to desolder them.

 

===== Really Loud buzzing sound for a second or two =====

If your game sometimes produces a really loud buzzing sound at random, check the version of your S2 sound rom. This problem was fixed with the latest S2 sound ROM for Attack from Mars, Congo, Safe Cracker and Tales of the Arabian Nights. Scared Stiff might also be affected but no version history for sound 1.1 exists for this game. Later games are not affected.
 

===Flipper Problems===

In most instances, an inexperienced tech will immediately blame the flipper coil itself for weak or non-functioning flippers. It is logical to blame the coil for the source of the problem. The flipper coil is, after all, the end reason why a flipper becomes engaged. However, its failure is the least probable reason that a flipper is not working. 

====Flipper does not work====
In this case, you've started a game, you press the flipper cabinet switch, and nothing happens.

The first thing to do is inspect the wire connections to the flipper coil lugs. The most common reason a WPC flipper does not function is that either one of the wires broke from the game to the lug, or one of the coil winding wires, has broken away from the coil lug and is no longer connected to the coil. This is a pretty simple fix. Make a clean cut to the wire, strip or sand 1/4" to 3/8" of insulation back, and make a nice solder joint on the coil.

[[Image:WPC95FlipperSpadeConnectors.jpg|300px|thumb|left|A good reason to nip spade connectors off and solder directly to the coil lug. This spade connector simply fell off the coil lug. Luckily, it didn't come to rest on an adjacent lug.]] 
Some WPC-95 titles used "spade connectors" (also known as FASTON connectors) to attach wires to the coil lugs. This was done for ease of manufacture and for that reason only. Similar to a wire breaking free, these spade connectors sometimes do not provide a solid connection and sometimes simply fall off. In that case, cut the spade connector off and solder the wire directly to the coil lug. This makes a much better connection that is also much more reliable. Should a spade connector fall onto an adjacent coil lug, it's very possible that a short circuit will be created, possibly damaging the FlipTronics board. 

=====Mechanical Reasons=====
There are a couple of mechanical reasons a flipper may not be working, including:
*Broken flipper link
*Flipper crank not "biting" flipper shaft (this would most likely manifest as a flipper that continues to move backwards, out of adjustment)

Simple inspection of the flipper mechanism should guide your corrective actions.

=====Pre-FlipTronics Games Electrical Reasons=====
*Failed flipper power supply - make sure that DC flipper power is present at the coil using your DMM. Place the red lead on a coil lug, the black lead on game ground (siderail or ground braid anywhere in the game). You should read about 70VDC.
*Flipper cabinet switch not "making" or fouled so badly that it doesn't conduct flipper power
*Fouled or missing flipper end-of-stroke switch. Pre-FlipTronics games relied on EOS switches in the same way that older games do. That is, power is routed to the power stroke winding of the coil via the EOS switch. If the EOS switch is fouled, only the hold winding will receive power; perhaps inadequate to move the flipper at all.

=====FlipTronics Games Electrical Reasons=====
*Failed flipper power supply. Flipper power originates at the transformer. It is routed through the power/driver board (which does nothing to it) and then to the FlipTronics board. The FlipTronics board rectifies the AC power via an onboard bridge rectifier. Power may be interrupted anywhere along this path, including a failed bridge rectifier or blown fuse.
*Failed flipper coil "power stroke" winding
*Flipper cabinet switch not "making" or flipper opto board not working
*Damaged connection between flipper cabinet switch and FlipTronics board
*FlipTronics board not recognizing flipper cabinet button switch closure
[[File:MissingPinFlipTronics.jpg|300px|thumb|left|A missing pin in the FlipTonics-to-MPU interface. The missing pin prevented transmission of the F8 signal (D7), which is the upper left flipper switch closed signal.]] 
An unusual reason for the flipper switch closure signal not being sent to the MPU is shown at left. 
*Failed logic path on the FlipTronics board including the transistors. See: [[Williams_WPC#WPC_FlipTronics_I_.26_II_Boards| WPC FlipTronics I and II Boards]] for a description of the signal path.
*Improperly seated or failed ribbon connectors between MPU and FlipTronics board

====Flipper is weak====
In this case, the flipper makes a stroke, but it's a weak stroke, not striking the ball with normal force.

=====Mechanical Reasons=====
*Not enough vertical movement in flipper bat (crank tightened too close to bushing)
*Cracked, broken or egged flipper bushing
*Mushroomed coil stop and plunger (replace coil sleeve too)
*Missing link bushing or oval link "eyelet"
*Tired flipper crank (will not tighten on bat shaft)

[[File:WPC Flipper Link Plunger.JPG|thumb|left|300px|An Example of an Egged Flipper Link and Mushroomed Flipper Plunger - Lower Link and Plunger Shown in Picture is new]]
 

=====Pre-FlipTronics Games Electrical Reasons=====
*Flipper cabinet switch not "making" or fouled so badly that it does not conduct
*Failed flipper end-of-stroke switch

=====FlipTronics Games Electrical Reasons=====

*Dirty flipper cabinet switch optos
*Power stroke winding of coil failed
*Failed or partially failed bridge rectifier on the FlipTronics II board or on the 50V power supply board as used in The Addams Family

====Flipper locks on or fails to fall to resting position====
In this case, the flipper locks in the up position, either at game power on or when the flipper cabinet switch is pressed.

=====Mechanical Reasons=====

=====Pre-FlipTronics Games Electrical Reasons=====

=====FlipTronics Games Electrical Reasons=====
*Flipper cabinet switch opto interupter not returning to proper at rest position
*Sticky flipper buttons, which can lead to opto interupter not returning to at rest position.

=====Fodder (may be useful to complete this section)=====
*Fouled or broken "normally closed" EOS switch
*Fouled or broken flipper cabinet switch
*Flipper relay not enabled
*Fouled / dirty or non-functioning flipper opto switches
*Upper flipper switch closures in switch test, when there aren't any upper flippers on game

==Parts Substitutions & Replacements==
===WPC-95 A/V Board RAM chips===
If one of the 65764 RAM chips needs to be replaced, but is unavailable, according to [https://pinside.com/pinball/forum/topic/wpc-95-av-board-1/page/3#post-8884790 this discussion on Pinside], IS61C256AH-15N RAM chips can be used as a replacement. However, since the address lines are different between the two different chips, all three RAM chips will need to be replaced with IS61C256AH-15N in order for the address lines on the chips to match up with each other.

==Repair Logs and Game Specific Problems and Fixes==
Since WPC games are overwhelmingly the most popular pinball titles at the moment, and there are a vast amount of titles with so many game specific issues, please refer to the [http://pinwiki.com/wiki/index.php?title=Williams_WPC#Game_List Game List] section of this guide. Click on the specific game, and a new page will open regarding repair logs and game specific problems and fixes for that particular game title.
 

=== World Cup Soccer locks on Right Sling and both Left and Right Kickout Holes at Power On ===
[[Image:WPCDriverBoardKeying.jpg|400px|thumb|left|Board layout diagram showing identical connector and keying at J124, J128, and J132)]] 
[[Image:WPCJ124J128Keying.jpg|400px|thumb|left|Image showing identical connector and keying at J124, J128, and J132)]] 
<ul>Problem</ul>
Upon power on, and with the coin door closed (defeating the high voltage interlock switch), the right slingshot as well as the left and right saucer kickout hole coils lock on.

<ul>Cause</ul>
The flash lamp drive connector that should be connected to J124 is instead connected to J128.

<ul>Discussion</ul>
Connecting the female plug to the wrong header pins is entirely possible since the connectors are the same width and are keyed identically. In World Cup Soccer (at least), the wire bundle is long enough to be connected (properly) to J124 or (improperly) to J128 or J132.
 

===S2 Sound ROM Failure on WPC-95 After a Successful Boot===
[[File:AnotherWPCCrackedASICSocket.jpg | thumb | left| 300px| An ASIC socket that has been cracked by using the wrong tool to remove the ASIC.]] 
If game is turned on and has a successful boot, but after a few minutes, the game bongs twice indicating an S2 sound ROM failure and becomes unresponsive, try reseating the ASIC chip on the MPU. Make sure to use the proper removal tool and not a screwdriver. Using an improper tool will damage the chip and/or socket.
 

===Replacement for opto part number QVE11233.0086 as used on Corvette and Twilight Zone ===

The QVE11233.0086 optos were specially screened for Williams production. They were used in the Twilight Zone clock and the Corvette race track. These special optos are no longer (easily) available.

Possible substitutions may be:
*H22B2 (found on AliExpress, tested and working in Corvette, has a gap of 3mm as opposed to 3.8mm on the original optos), and
*KTIR0621DS (not tested, has a wider gap of 5mm). 

=== Dr. Who Playfield Glass Present Switch ===
[[File:DrWhoTimeExpander.jpg ‎‎|300px|thumb|left|Heed the warning.]]

Dr. Who is unique in that it has a switch installed on the cabinet inside, top left, which indicates that the playfield glass is installed. When this switch opens, a loud safety message is voiced along with a message on the DMD display. These messages are meant to alert repairmen to the safety issue with the "Time Expander" Mini Playfield.

The mini playfield has no "bind detected" mechanism as a garage door might have. If something becomes jammed in the mechanism, like a finger, the motor will continue to run, possibly causing serious injury.

Defeating this switch is not advised. Extreme caution is certainly warranted.

Leon Borre WPC Fliptronics board repair

2026-04-26T21:20:56Z

The Hammer: Fixed typo

'''Bench testing the Fliptronic board.'''

[[Image:swash4.gif]]

'''Some early machines of the WPC series do not yet have this board , Party zone was the first machine using the fliptronic board. You will find Fliptronic type 1 only in Addams family, all others are Fliptronic type2 boards. The Fliptronic 2 board has a extra bridge rectifier and some fuses and one extra connector J907, and furthermore connector 901 is the same connector as on the Fliptronic 1 board but has another function. '''

'''[[Image:flip1.JPG|200px]]'''

'''The Fliptronic 1 board.'''

'''[[Image:flip2.JPG|200px]]'''

'''The Fliptronic 2 board. Red arrow indicates the connector J901 and blue arrow the extra connector J907 , both are used to connect the 70 volt AC in DC out.'''

'''Some very strange things could happen when this board is faulty. Only one example: Addams Family , the top flipper on the right, when used stay "up" and came down again when pushing the flippers on the left !!! Of course in most cases it is just the flipper that will not work at all, or stay up once it is energised, or all the time..'''

'''Look first if the end of stroke contacts are working properly , it has to close when the flipper is excitated. If you are shure it is the board that is faulty proceed as follows. . '''

'''[[Image:swash1.gif]]'''

'''We need 5 and 12 volts to operate the board on the bench. Connect the tensions at J804/904, pin 4 and 5 is ground , pin 1 is 5 and pin 3 is 12.'''

'''All connectors have two numbers , ( 802/902) this because the numbers are different on fliptronic 1 and fliptronic 2 type boards. The test is the same for both type boards.'''

'''Ground all 4 pins of J801( Only on a Fliptronic type 1 board it is useless to ground J901 on a Fliptronic type 2 board.) Connect a LED strip at J802./902( the LED strip and how to make one,see at repair of Bally driver board) the common of the LED strip is connected at 5 volts.'''

'''[[Image:1boel.jpg|200px]]'''

'''Fliptronic 1 connected . Red arrow the tensions ar applied here 5, 12 and ground. Blue arrow , the LED strip connected. Orange arrow these 4 pins shoud be grounded during testing. Black arrow here the input pins , ground them one by one during test of the LM339 input IC's.'''

'''[[Image:boel2.JPG|200px]]'''

'''The Fliptronic 2 board , the same as type 1 blue arrow the LED strip , Red arrow the tensions 5, 12 and ground, and orange arrow the input pins to ground one by one, during input test. '''

'''[[Image:swash1.gif]]'''

'''We will check the input circuitry, always one of the ( or both) LM339's that will fail.U4 and U6.'''

'''Check with a logic tester or voltmeter the output pins 1,2,13 and 14 at U4 and U6 , these must change from 5 to 0 volt when grounding pins at input connectors J805/905 and J806/906,'''

'''Pin 2 at U4 changes when pin 1 J806/906 is grounded. Pin 1 at U4 changes when pin 1 at J805/905 is grounded.'''

'''Pin 14 at U4 changes when pin 3 at J806/906 is grounded. Pin 13 at U4 changes when pin 2 at J805/905 is grounded.'''

'''Pin 2 at U6 changes when pin 4 at J806/906 is grounded. Pin 1 at U6 changes when pin 3 at J805/905 is grounded.'''

'''Pin 14 at U6 changes when pin 5 at J806/906 is grounded. Pin 13 at U6 changes when pin 5 at J805/905 is grounded.'''

'''If no change replace the a ppropriated LM339.'''

'''[[Image:swash1.gif]]'''

'''Next we check the complete transistor drive circuitry.'''

'''As there is a LED test strip on J802/902 , the LED will go "on" if the circuit is ok. '''

'''Grounding the apropriated pins at U2 will excitate the whole circuit for one of the outputs. '''

'''To check output on J802/902 pins 13 12 ground pin 2 at U2'''

'''To check ouput on J802/902 pin11 ground pin 19 at U2.'''

'''To check output on J802/902 pins 9 8 ground pin 16 at U2.'''

'''To check output on J802/902 pin 7 ground pin 5 at U2.'''

'''To check output on J802/902 pin 5 6 ground pin 6 at U2.'''

'''To check output on J802/902 pin 4 ground pin 15 at U2.'''

'''To check output on J802/902 pin 3 2 ground pin 12 at U2'''

'''To check output at J802/902 pin 1 ground pin 9 at U2.'''

'''When one of the LEDs will not light up follow the signal change , at the bases of the transistors in that circuit. When applying the ground connection at U2 the base always has to show some polarity change..If not it's the transistor at the left ( on schematic) from the base resistor that shows no change ,who is faulty.'''

'''The IC's that are not tested using this repair method, are some input and output couplers U2, U3, U5 these are directly connected to the CPU board and are not connected with the input or outputs, in general it's always the input and/or output circuits that are the trouble makers as there is more chance for shorts or excesive load on these circuits.'''

MPU Battery Replacement Options

2026-02-01T16:11:39Z

The Hammer: /* Remote Battery Pack */ minor

{{WIP}}
=Introduction=
RAM chips are typically used to store game settings and bookkeeping data. However, RAM is volatile and can only store data if power is applied to the chip. If power is lost, so is the data. So, the solution to this was to include a battery on the MPU to retain the data in RAM when the game was turned off.

Unfortunately, many of these batteries leak and damage or destroy circuit boards in the process. So, it is imperative that the battery is removed from the MPU in order to prevent this damage in the future.

In order to retain the data for game settings and bookkeeping, there are a few different options to replace the original battery and prevent future problems from leakage.

This guide assumes that the old battery has already been removed from the MPU and any damaged caused by a leaking battery has been cleaned up and repaired.

==Remote Battery Pack==
The remote battery solution is when a battery pack is installed in a game, but lead wires are attached to the positive and negative solder points on the MPU.

[[File:Leaked batteries.jpg|left|thumb|200px|Battery pack installed on a Gottlieb Genesis. User failed to install a blocking diode. Pic courtesy of Ray Brackins at Wide Area Repair]] 
On older game systems that originally had a rechargeable battery installed, a diode must also be installed to prevent the MPU from attempting to charge the non-rechargeable batteries (referred to as a "blocking diode"), otherwise the batteries may expand, leak, and/or explode.

Place the blocking diode on the plus (+) lead of the battery pack, with the banded end of the diode towards the plus (+) connection on the MPU board.
 

The safest place to mount a remote battery pack is below any circuit boards and as far away from them as possible, so as to avoid escaping gas and drippings from leaks. It has been reported that circuit boards have been affected by the gas from leaking batteries as far as 6 inches away.

Additionally, it can be a good idea to put the battery pack inside a zip lock bag to help limit damage from a leaking battery.

==Lithium Battery==
Classic Williams games had a build-in battery holder that could fit AA batteries. Unfortunately, it was common to see standard alkaline batteries used in these holders, which always leaked.

Lithium batteries are produced in the AA battery footprint, so can be installed in the battery holders used on classic Williams MPUs. Lithium batteries are less prone to leaking, but it is still a good idea to mount them off the MPU in a remote battery pack.

Installing batteries directly onto the MPU leaves the game open to the possibility of an owner replacing a dead AA lithium battery with a AA alkaline battery if they don't have a lithium battery on-hand because it's the easy and lazy thing to do. As a result, battery leakage becomes a serious risk again.

==Memory Capacitor==
Memory capacitors are special capacitors that hold a charge for an extended period of time and take the place of a battery. The downside is that the game has to be turned on at least once for several hours every 14-30 days in order to build up to a full charge. However, there are reported instances where a memory capacitor has held for over a year on a Gottlieb System 80B MPU.

Note that on some game systems, a resistor with a higher resistance and/or wattage must be installed in order to handle the inrush of current, especially since a depleted memory capacitor can briefly act as a dead short.

Note that on games systems with a real-time clock, a memory capacitor will only last a few days, since energy is being drained by both the clock and the RAM.

Additionally, lower quality capacitors are prone to leaking, though not as spectacularly as alkaline or NiCad batteries, so it is important to stick with a reputable brand.

Memory capacitors have fallen from favor for some people, because of only holding a short-term charge, as well as the introduction and economical prices of lithium batteries, lithium coin cell batteries, and NVRAM.

Systems which are best fit to use a memory capacitor are Gottlieb System 80/ 80A /80B, Bally -17 / -35 / 6803, and Stern M-100 and M-200. Data East MPUs fare pretty well too, however, Williams System 11 and its variants for some reason do not.

==Coin Cell / Button Battery==
Lithium coin cell batteries (also known as button batteries) are much less prone to leakage than the batteries originally used on MPUs. They typically have about a 10-year life span when used on an MPU. Gottlieb System 3 MPUs were the first to utilize coin cell batteries.

On older game systems that originally had a rechargeable battery installed, a diode must also be installed to prevent the MPU from attempting to charge the non-rechargeable lithium battery (referred to as a "blocking diode"), otherwise the battery may expand, leak, and/or explode.

Note that through normal usage, the risk of a lithium battery leaking is pretty small, but they still can--and do--leak after enough time. Poor storage conditions are also sometimes a contributing factor.

[[file:gtb-sys3-mpu-battery-leak.jpg|thumb|left|250px|Gottlieb System 3 MPU with a leaking coin cell battery]] 

==NVRAM==
NVRAM (non-volitile RAM) is being used to replace volatile RAM installed on the MPU. Volatile RAM can only store data if power is applied to the chip. If power is lost, so is the data. NVRAM can retain data without needing any power. It is essentially "frozen" in the chip.

Various game systems use different types of RAM, so adapters are needed to adapt the footprint and pinout of the 6264 NVRAM pinout to the RAM footprint/socket that the game system is using.

NVRAM adapters typically list which RAM footprints/sockets and/or game systems they are intended to support.

===Products===
Most NVRAM developers sell directly on their websites, but some are also available from various pinball suppliers.

* [http://lockwhenlit.com/anyPin.htm AnyPin Adapter] ([https://www.pinballlife.com/search.html?Search=nvram Pinball Life])
* [http://www.pinitech.com/products/cat_memory.php Pinitech Adapters]
* [http://nvram.weebly.com/ Pinball Electronics Adapters (barakandl)]
* [https://pinballelectronics.com/ Pinball Electronics]

=Game Systems=

==Allied Leisure==
===Generation 1===
Game data is not saved. A battery solution is not necessary.

===Generation 2===

==Alvin G==
* Remote Battery

==Atari==
===Generation 1===
Game data is not saved. A battery solution is not necessary.

===Generation 2===
* Remote battery
* Coin cell battery
* [[Atari_Repair#MPU_Issues|Memory capacitor]]

Note: Generation 2 games generally suffer no ill effects when running without a battery, other than that high scores and bookkeeping data would not be retained.

==Bally==

===-17/-35/-133 MPU===
* [[Bally/Stern#AA_Battery_pack|Remote Battery]]
* [[Bally/Stern#Memory_Capacitor|Memory Capacitor]]
* Coin Cell Battery
* NVRAM

Note: running some classic Bally games without a battery or battery replacement will cause the game to play default sounds, and not the correct sounds for the game. This affects games like Xenon, Eight Ball Deluxe, Flash Gordon, Skateball, Centaur, Cybernaut, and Fathom.

===6803 MPU===
* [[Bally_6803#Relocating_the_Factory_NiCad_Battery_off_the_MPU|Remote Battery]]
* NVRAM

==Capcom==
* NVRAM

==Data East==
* [[Data_East/Sega#Relocating_the_Battery_from_the_MPU_board|Remote Battery]]
* [[Data_East/Sega#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory Capacitor]]
* [[Data_East/Sega#Installing_a_Lithium_.22Button_Cell.22_Battery|Coin Cell Battery]]
* NVRAM

==GamePlan==
* Remote Battery
* NVRAM (not fully tested)

==Gottlieb==

===System 1===
* [[Gottlieb_System_1#Relocating_the_Battery_from_the_CPU_board|Remote Battery]]
* [[Gottlieb_System_1#Installing_a_Coin_Cell_Battery|Coin Cell Battery]]
* [http://www.pinitech.com/products/gottlieb_sys1_nvram.php NVRAM]

Note: Running without a battery attached can sometimes introduce garbage data for the high scores and bookeeping data at power up.

===System 80/80A/80B===
* [[Gottlieb_System_80#Relocating_the_battery_from_the_MPU_board|Remote Battery]]
* [[Gottlieb_System_80#Relocating_the_battery_from_the_MPU_board|Memory Capacitor]]
* Coin Cell Battery
* NVRAM

===System 3===
* [[Gottlieb_System_3#Relocating_the_battery_from_the_MPU_board|Remote Battery]]
* [http://www.pinrepair.com/sys3/#battery Coin Cell Battery]
* [[Gottlieb_System_3#NVRAM_Installation|NVRAM]]

[[File:GottliebSystem3NVRAM.jpg|left|thumb|200px|NVRAM installed with jumpers pictured on a Gottlieb System 3 MPU]] 

Some experimentation leading to the development of an NVRAM solution can be found [https://pinside.com/pinball/forum/topic/nvram-gottlieb-system-3-success here].

Note: Operating the game with no battery or a failing battery will display the message "low battery or bad U3 or U6". To bypass this error message, press the reset button (SW1) on the MPU.

==Heighway Pinball==

==Jersey Jack Pinball==
* A coin cell battery is [http://www.ipdb.org/showpic.pl?id=5800&picno=63749&zoom=1 installed on the motherboard].

==Sega==
* [[Sega/Stern_White_Star_Repair#Relocating_the_Battery_from_the_MPU_board|Remote Battery]]
* Coin Cell Battery
* [[Sega/Stern_White_Star_Repair#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory capacitor]]
* NVRAM

==Spooky Pinball==

==Stern==

===MPU-100/MPU-200===
* [[Bally/Stern#AA_Battery_pack|Remote Battery]]
* [[Bally/Stern#Memory_Capacitor|Memory Capacitor]]
* Coin Cell Battery
* NVRAM

Note: The MPU-200 uses two RAM chips and has two RAM sockets. Two separate 5101 adapters can be used, or an adapter that specifically accommodates this board can be used.

Note: When using NVRAM with [[Meteor]]'s production game ROMs, [https://pinside.com/pinball/forum/topic/price-check-1980-sterns-quicksilver-stargazer-seawitch/page/114#post-6486584 there is a sound bug] in that version. An [[Media:Meteora2(1).zip|unofficial updated bug fix ROM]] (by slochar) is available, which clears the sound registers on boot-up before game initialization.

===Whitestar===
* [[Sega/Stern_White_Star_Repair#Relocating_the_Battery_from_the_MPU_board|Remote Battery]]
* Coin Cell Battery
* [[Sega/Stern_White_Star_Repair#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory capacitor]]
* NVRAM

===SAM===
* [[Stern_S.A.M._System_Repair#Relocating_the_battery_from_the_MPU_board|Remote Battery]]
* Coin Cell Battery
* NVRAM

===SPIKE===
* A coin cell battery is mounted vertically on the PCB in the backbox.

==Williams==

===System 3-7===
* [[Williams_System_3_-_7#Relocating_the_batteries_away_from_the_MPU_board|Remote Battery]]
* [[Williams_System_3_-_7#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory Capacitor]]. [http://tuukan.fliput.net/goldcap_en.html Alternate guide].
* Coin Cell Battery
* [[Williams_System_3_-_7#Installing_NVRAM_Instead_of_Batteries|NVRAM]]

===System 9===
* [[Williams_System_9_-_11#Relocating_the_battery_from_the_System_9_MPU_board|Remote Battery]]
* [[Williams_System_9_-_11#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory Capacitor]]
* Coin Cell Battery
* [[Williams_System_9_-_11#Installing_NVRAM_instead_of_batteries|NVRAM]]

===System 11/11A/11B/11C===
* [[Williams_System_9_-_11#Relocating_the_battery_from_the_System_11_MPU_board|Remote Battery]]
* [[Williams_System_9_-_11#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory Capacitor]]
* Coin Cell Battery
* [[Williams_System_9_-_11#Installing_NVRAM_instead_of_batteries|NVRAM]]

===WPC===
* [[Williams_WPC#Relocating_the_battery_from_the_MPU_board|Remote Battery]]
* [[Williams_WPC#Installing_an_external_battery_on_a_WPC-95_CPU_using_the_Auxiliary_Battery_header_.28J213.29|Remote Battery on WPC-95]]
* Coin Cell Battery
* [[Williams_WPC#Replacing_the_CPU_RAM_with_non-volatile_RAM|NVRAM]]

Note: Games that utilize a real-time clock will need a battery instead of NVRAM to keep proper time. Otherwise, the date/time will not advance while the game is powered off.

====Games Affected By a Real-Time Clock====

WPC (Fliptronics II)
* Creature from the Black Lagoon (different music plays based on the date)
* Twilight Zone (clock on the playfield shows correct time)

WPC-S
* Dirty Harry (midnight madness)
* Johnny Mnemonic (midnight madness)
* WHO dunnit (midnight madness)
* Theatre of Magic ("hermaphrodite position" - midnight madness does not depend on real time clock since it is a game mode)

WPC-95
* Congo (midnight madness)
* Junk Yard (midnight madness)
* NBA Fastbreak (midnight madness)
* Medieval Madness (midnight madness, but special mode needs to be enabled to activate it)

Note that on games systems with a real-time clock, a memory capacitor will keep the clock going, but since energy will be drained by both the RAM and the clock, a fully charged memory capacitor is reported to be able to keep the clock active for about 2-4 days, while the RAM will lose its settings after about 10 days. Additionally, on WPC systems, a minimum of 3v is required to keep the real-time clock alive, while the RAM can sometimes be kept alive until the memory capacitor has drained to as low as 2v with 6264 RAM and 1v with 5101 RAM.

===Pin2000===
* [[Pinball_2000_Repair#CMOS_and_Prism_card_batteries|Coin Cell Battery]]

==Zaccaria==

===8060 MPU===

===Generation 1===
* [http://www.zaccaria-pinball.com/gen1/cpu.html|Remote Battery or Memory Capacitor]
* NVRAM

===Generation 2===
* [http://www.zaccaria-pinball.com/gen2/cpu.html|Remote Battery or Memory Capacitor]
* NVRAM

MPU Battery Replacement Options

2026-01-31T23:16:34Z

The Hammer: /* Remote Battery Pack */

{{WIP}}
=Introduction=
RAM chips are typically used to store game settings and bookkeeping data. However, RAM is volatile and can only store data if power is applied to the chip. If power is lost, so is the data. So, the solution to this was to include a battery on the MPU to retain the data in RAM when the game was turned off.

Unfortunately, many of these batteries leak and damage or destroy circuit boards in the process. So, it is imperative that the battery is removed from the MPU in order to prevent this damage in the future.

In order to retain the data for game settings and bookkeeping, there are a few different options to replace the original battery and prevent future problems from leakage.

This guide assumes that the old battery has already been removed from the MPU and any damaged caused by a leaking battery has been cleaned up and repaired.

==Remote Battery Pack==
The remote battery solution is when a battery pack is installed in a game, but lead wires are attached to the positive and negative solder points on the MPU.

[[File:Leaked batteries.jpg|left|thumb|200px|Battery pack installed on a Gottlieb Genesis. User failed to install a blocking diode. Pic courtesy of Ray Brackins at Wide Area Repair]] 
On older game systems that originally had a rechargeable battery installed, a diode must also be installed to prevent the MPU from attempting to charge the non-rechargeable batteries (referred to as a "blocking diode"), otherwise the batteries may expand, leak, and/or explode.

Place the blocking diode on the plus (+) lead with the banded end of the diode towards the plus (+) connection on the MPU board.
 

The safest place to mount a remote battery pack is below any circuit boards and as far away from them as possible, so as to avoid escaping gas and drippings from leaks. It has been reported that circuit boards have been affected by the gas from leaking batteries as far as 6 inches away.

Additionally, it can be a good idea to put the battery pack inside a zip lock bag to help limit damage from a leaking battery.

==Lithium Battery==
Classic Williams games had a build-in battery holder that could fit AA batteries. Unfortunately, it was common to see standard alkaline batteries used in these holders, which always leaked.

Lithium batteries are produced in the AA battery footprint, so can be installed in the battery holders used on classic Williams MPUs. Lithium batteries are less prone to leaking, but it is still a good idea to mount them off the MPU in a remote battery pack.

Installing batteries directly onto the MPU leaves the game open to the possibility of an owner replacing a dead AA lithium battery with a AA alkaline battery if they don't have a lithium battery on-hand because it's the easy and lazy thing to do. As a result, battery leakage becomes a serious risk again.

==Memory Capacitor==
Memory capacitors are special capacitors that hold a charge for an extended period of time and take the place of a battery. The downside is that the game has to be turned on at least once for several hours every 14-30 days in order to build up to a full charge. However, there are reported instances where a memory capacitor has held for over a year on a Gottlieb System 80B MPU.

Note that on some game systems, a resistor with a higher resistance and/or wattage must be installed in order to handle the inrush of current, especially since a depleted memory capacitor can briefly act as a dead short.

Note that on games systems with a real-time clock, a memory capacitor will only last a few days, since energy is being drained by both the clock and the RAM.

Additionally, lower quality capacitors are prone to leaking, though not as spectacularly as alkaline or NiCad batteries, so it is important to stick with a reputable brand.

Memory capacitors have fallen from favor for some people, because of only holding a short-term charge, as well as the introduction and economical prices of lithium batteries, lithium coin cell batteries, and NVRAM.

Systems which are best fit to use a memory capacitor are Gottlieb System 80/ 80A /80B, Bally -17 / -35 / 6803, and Stern M-100 and M-200. Data East MPUs fare pretty well too, however, Williams System 11 and its variants for some reason do not.

==Coin Cell / Button Battery==
Lithium coin cell batteries (also known as button batteries) are much less prone to leakage than the batteries originally used on MPUs. They typically have about a 10-year life span when used on an MPU. Gottlieb System 3 MPUs were the first to utilize coin cell batteries.

On older game systems that originally had a rechargeable battery installed, a diode must also be installed to prevent the MPU from attempting to charge the non-rechargeable lithium battery (referred to as a "blocking diode"), otherwise the battery may expand, leak, and/or explode.

Note that through normal usage, the risk of a lithium battery leaking is pretty small, but they still can--and do--leak after enough time. Poor storage conditions are also sometimes a contributing factor.

[[file:gtb-sys3-mpu-battery-leak.jpg|thumb|left|250px|Gottlieb System 3 MPU with a leaking coin cell battery]] 

==NVRAM==
NVRAM (non-volitile RAM) is being used to replace volatile RAM installed on the MPU. Volatile RAM can only store data if power is applied to the chip. If power is lost, so is the data. NVRAM can retain data without needing any power. It is essentially "frozen" in the chip.

Various game systems use different types of RAM, so adapters are needed to adapt the footprint and pinout of the 6264 NVRAM pinout to the RAM footprint/socket that the game system is using.

NVRAM adapters typically list which RAM footprints/sockets and/or game systems they are intended to support.

===Products===
Most NVRAM developers sell directly on their websites, but some are also available from various pinball suppliers.

* [http://lockwhenlit.com/anyPin.htm AnyPin Adapter] ([https://www.pinballlife.com/search.html?Search=nvram Pinball Life])
* [http://www.pinitech.com/products/cat_memory.php Pinitech Adapters]
* [http://nvram.weebly.com/ Pinball Electronics Adapters (barakandl)]
* [https://pinballelectronics.com/ Pinball Electronics]

=Game Systems=

==Allied Leisure==
===Generation 1===
Game data is not saved. A battery solution is not necessary.

===Generation 2===

==Alvin G==
* Remote Battery

==Atari==
===Generation 1===
Game data is not saved. A battery solution is not necessary.

===Generation 2===
* Remote battery
* Coin cell battery
* [[Atari_Repair#MPU_Issues|Memory capacitor]]

Note: Generation 2 games generally suffer no ill effects when running without a battery, other than that high scores and bookkeeping data would not be retained.

==Bally==

===-17/-35/-133 MPU===
* [[Bally/Stern#AA_Battery_pack|Remote Battery]]
* [[Bally/Stern#Memory_Capacitor|Memory Capacitor]]
* Coin Cell Battery
* NVRAM

Note: running some classic Bally games without a battery or battery replacement will cause the game to play default sounds, and not the correct sounds for the game. This affects games like Xenon, Eight Ball Deluxe, Flash Gordon, Skateball, Centaur, Cybernaut, and Fathom.

===6803 MPU===
* [[Bally_6803#Relocating_the_Factory_NiCad_Battery_off_the_MPU|Remote Battery]]
* NVRAM

==Capcom==
* NVRAM

==Data East==
* [[Data_East/Sega#Relocating_the_Battery_from_the_MPU_board|Remote Battery]]
* [[Data_East/Sega#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory Capacitor]]
* [[Data_East/Sega#Installing_a_Lithium_.22Button_Cell.22_Battery|Coin Cell Battery]]
* NVRAM

==GamePlan==
* Remote Battery
* NVRAM (not fully tested)

==Gottlieb==

===System 1===
* [[Gottlieb_System_1#Relocating_the_Battery_from_the_CPU_board|Remote Battery]]
* [[Gottlieb_System_1#Installing_a_Coin_Cell_Battery|Coin Cell Battery]]
* [http://www.pinitech.com/products/gottlieb_sys1_nvram.php NVRAM]

Note: Running without a battery attached can sometimes introduce garbage data for the high scores and bookeeping data at power up.

===System 80/80A/80B===
* [[Gottlieb_System_80#Relocating_the_battery_from_the_MPU_board|Remote Battery]]
* [[Gottlieb_System_80#Relocating_the_battery_from_the_MPU_board|Memory Capacitor]]
* Coin Cell Battery
* NVRAM

===System 3===
* [[Gottlieb_System_3#Relocating_the_battery_from_the_MPU_board|Remote Battery]]
* [http://www.pinrepair.com/sys3/#battery Coin Cell Battery]
* [[Gottlieb_System_3#NVRAM_Installation|NVRAM]]

[[File:GottliebSystem3NVRAM.jpg|left|thumb|200px|NVRAM installed with jumpers pictured on a Gottlieb System 3 MPU]] 

Some experimentation leading to the development of an NVRAM solution can be found [https://pinside.com/pinball/forum/topic/nvram-gottlieb-system-3-success here].

Note: Operating the game with no battery or a failing battery will display the message "low battery or bad U3 or U6". To bypass this error message, press the reset button (SW1) on the MPU.

==Heighway Pinball==

==Jersey Jack Pinball==
* A coin cell battery is [http://www.ipdb.org/showpic.pl?id=5800&picno=63749&zoom=1 installed on the motherboard].

==Sega==
* [[Sega/Stern_White_Star_Repair#Relocating_the_Battery_from_the_MPU_board|Remote Battery]]
* Coin Cell Battery
* [[Sega/Stern_White_Star_Repair#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory capacitor]]
* NVRAM

==Spooky Pinball==

==Stern==

===MPU-100/MPU-200===
* [[Bally/Stern#AA_Battery_pack|Remote Battery]]
* [[Bally/Stern#Memory_Capacitor|Memory Capacitor]]
* Coin Cell Battery
* NVRAM

Note: The MPU-200 uses two RAM chips and has two RAM sockets. Two separate 5101 adapters can be used, or an adapter that specifically accommodates this board can be used.

Note: When using NVRAM with [[Meteor]]'s production game ROMs, [https://pinside.com/pinball/forum/topic/price-check-1980-sterns-quicksilver-stargazer-seawitch/page/114#post-6486584 there is a sound bug] in that version. An [[Media:Meteora2(1).zip|unofficial updated bug fix ROM]] (by slochar) is available, which clears the sound registers on boot-up before game initialization.

===Whitestar===
* [[Sega/Stern_White_Star_Repair#Relocating_the_Battery_from_the_MPU_board|Remote Battery]]
* Coin Cell Battery
* [[Sega/Stern_White_Star_Repair#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory capacitor]]
* NVRAM

===SAM===
* [[Stern_S.A.M._System_Repair#Relocating_the_battery_from_the_MPU_board|Remote Battery]]
* Coin Cell Battery
* NVRAM

===SPIKE===
* A coin cell battery is mounted vertically on the PCB in the backbox.

==Williams==

===System 3-7===
* [[Williams_System_3_-_7#Relocating_the_batteries_away_from_the_MPU_board|Remote Battery]]
* [[Williams_System_3_-_7#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory Capacitor]]. [http://tuukan.fliput.net/goldcap_en.html Alternate guide].
* Coin Cell Battery
* [[Williams_System_3_-_7#Installing_NVRAM_Instead_of_Batteries|NVRAM]]

===System 9===
* [[Williams_System_9_-_11#Relocating_the_battery_from_the_System_9_MPU_board|Remote Battery]]
* [[Williams_System_9_-_11#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory Capacitor]]
* Coin Cell Battery
* [[Williams_System_9_-_11#Installing_NVRAM_instead_of_batteries|NVRAM]]

===System 11/11A/11B/11C===
* [[Williams_System_9_-_11#Relocating_the_battery_from_the_System_11_MPU_board|Remote Battery]]
* [[Williams_System_9_-_11#Installing_a_Memory_Capacitor_Instead_of_Batteries|Memory Capacitor]]
* Coin Cell Battery
* [[Williams_System_9_-_11#Installing_NVRAM_instead_of_batteries|NVRAM]]

===WPC===
* [[Williams_WPC#Relocating_the_battery_from_the_MPU_board|Remote Battery]]
* [[Williams_WPC#Installing_an_external_battery_on_a_WPC-95_CPU_using_the_Auxiliary_Battery_header_.28J213.29|Remote Battery on WPC-95]]
* Coin Cell Battery
* [[Williams_WPC#Replacing_the_CPU_RAM_with_non-volatile_RAM|NVRAM]]

Note: Games that utilize a real-time clock will need a battery instead of NVRAM to keep proper time. Otherwise, the date/time will not advance while the game is powered off.

====Games Affected By a Real-Time Clock====

WPC (Fliptronics II)
* Creature from the Black Lagoon (different music plays based on the date)
* Twilight Zone (clock on the playfield shows correct time)

WPC-S
* Dirty Harry (midnight madness)
* Johnny Mnemonic (midnight madness)
* WHO dunnit (midnight madness)
* Theatre of Magic ("hermaphrodite position" - midnight madness does not depend on real time clock since it is a game mode)

WPC-95
* Congo (midnight madness)
* Junk Yard (midnight madness)
* NBA Fastbreak (midnight madness)
* Medieval Madness (midnight madness, but special mode needs to be enabled to activate it)

Note that on games systems with a real-time clock, a memory capacitor will keep the clock going, but since energy will be drained by both the RAM and the clock, a fully charged memory capacitor is reported to be able to keep the clock active for about 2-4 days, while the RAM will lose its settings after about 10 days. Additionally, on WPC systems, a minimum of 3v is required to keep the real-time clock alive, while the RAM can sometimes be kept alive until the memory capacitor has drained to as low as 2v with 6264 RAM and 1v with 5101 RAM.

===Pin2000===
* [[Pinball_2000_Repair#CMOS_and_Prism_card_batteries|Coin Cell Battery]]

==Zaccaria==

===8060 MPU===

===Generation 1===
* [http://www.zaccaria-pinball.com/gen1/cpu.html|Remote Battery or Memory Capacitor]
* NVRAM

===Generation 2===
* [http://www.zaccaria-pinball.com/gen2/cpu.html|Remote Battery or Memory Capacitor]
* NVRAM

Talk:Post-Purchase Checklist

2026-01-10T15:48:56Z

The Hammer: Asking for input as to the fire hazards listed here.

About 3.10 Game Specific Safety & Fire Hazards

Someone posted on Pinside that they are now concerned about their WMS sound board catching fire. I have had a few tantalum caps explode which leaves a char mark, but no true fire. A char mark on a board is pretty common but I have never seen a fire (meaning fire extinguisher or fire department call needed) as a result.

Yes on the WD40.

Certainly the 'missing fuses' on Williams 3 - 7, 9, 11 and DE 1 - 3 are crucial. I suspect a shorted bridge could cause a lot of damage before the line fuse blows. Has anyone seen flames when this happens.

I don't want to overstate nor understate this issue and I know that others have more field experience than I do. I appreciate ForceFlow for bringing this up for attention.

Vehicles for Moving Pinball Machines

2026-01-01T15:27:43Z

The Hammer: /* Toyota */

=Introduction=
Often on the rec.games.pinball newsgroup, there are discussions over which vehicles will or will not hold a pinball machine (Here's a link to the [http://groups.google.com/group/rec.games.pinball/search?hl=en&group=rec.games.pinball&q=will+a+pin+fit+in+a question as asked on RGP] and [https://pinside.com/pinball/forum/topic/vehicles-that-a-pinball-machine-fits-in a discussion on pinside]).

Word of caution: Gottlieb System 3 games (and some 80B games) with the head/backbox folded for transport are taller than any other manufacturer / platform. The folded height for Gottlieb System 3 games is about 34", and the width of the backbox is 27". The height of the cabinet when the backbox is removed is 28". However, Gottlieb's "street level" System 3 games are less tall when folded for transport, and are instead about the same height as other traditional folded games from other manufacturers. 

Below is a listing of vehicles, as well as specifics regarding said vehicles.

=Cabinet Sizes=

==Standard Cabinet Sizes==

{| class="wikitable sortable"
!Manufacturer
!System
!Game Style
!Folded Height
!Cabinet Body Dimensions
!Backbox Dimensions
!Notes
|-
|Gottlieb
|System 1
|Standard
|n/a
|H:21", L:52" (without shooter), 22-1/4"
|H:29-1/2", W:28-1/4", D:10-1/2" (bottom) to 12" (top)
|
|-
|Gottlieb
|System 80A/80B
|Standard
|26"
|H:19.5", L:49.5" (with shooter rod), W22"
|W:28.5"
|Only games with the thin backbox (Super Orbit, Royal Flush Deluxe, Amazon Hunt, Rack 'em Up, Ready Aim Fire, Jacks to Open, Alien Star, The Games, El Dorado, Touchdown, Ice Fever, Chicago Cubs Triple Play, Bounty Hunter, Tag-Team)
|-
|Gottlieb
|System 3, DMD
|Standard
|34"
|H:28", L:54-1/2" (with shooter rod), W:27"
|W:27"
|Folded height is taller than any other manufacturer. A few games have toppers.
|-
|Bally
|6803
|Standard
|33"
|H:?, L:53" (with shooter rod), 50-1/2" (w/o shooter rod) W:?"
|
|Motordome, Special Forces, Hardbody, etc. Dungeons & Dragons, Blackwater 100, and Escape from the Lost World are exceptions
|-
|Bally/Williams
|WPC
|Standard
|29-1/2"
|H:24", L:52" (without shooter), W:22-1/2"
|H:28-1/2", W:28-3/4", D:6-1/2" (bottom) to 9-3/4" (top)
|Some games come with a gun handle, which adds 6"-7" to the length of the cabinet.
|-
|Bally/Williams
|WPC
|SuperPin
|29-1/2"
|H:24", L:52" (without shooter), W:25"
|H:28-1/2", W:29", D:6-1/2" (bottom) to 9-3/4" (top)
|Some games come with a gun handle, which adds 6"-7" to the length of the cabinet.
|-
|}

==Cabinet Size Exceptions==

{| class="wikitable sortable"
!Manufacturer
!Game Title
!System
!Game Style
!Folded Dimensions
!Cabinet Dimensions
!Backbox Dimensions
!Notes
|-
|}

=Vehicles=

== Acura ==

MDX (2000-2006) - Will fit most games. STTNG fit.

MDX (2007-2013) - 2007+ lowered hatch height, TAF barely fit and left marks in ceiling. Will fit Stern, DE and Williams Widebody

RDX (Unspecified Year) - pins fit great, moved newer Sterns and older Bally's with no problems.

RDX(2014+) - Will not fit a pin

== Audi ==

A3 Hatchback (Unspecified year) - fits a pin with the backbox disconnected.

Q7 (Unspecified year) - about 1" too short

Q7 w/ third row seating (2013) - BARELY fits...very tight

== BMW ==

525 Wagon (1993) - Fits any older pin without folding head. Folding head units must be removed.

X3 first generation E83 (2003-2010) & second generation F25 (2010-2014) - Fits any standard pin when folded down (not in box)

X5 - Fits most standard sized modern pins. With Gottlieb DMD's you need to loosen the head and slide it down a little.

== Buick ==

Enclave (2008-Current) - Will fit all standard and wide body pinball machines with back seat folded down, some games like Gottlieb System 3 may need to be put on their sides.

Rendezvous (2001-2007) - Will fit all standard and wide body pinball machines with back seat folded down.

== Cadillac ==

SRX (2004-2009) - Will fit most standard and wide body pinball machines. The backbox needs to be removed on Gottlieb System 3 pins.

SRX (2010+) - Will not fit

== Chevrolet ==

Avalanche (Unspecified year) - Will fit at least two pins (and 5 people).

Chevette (1985) - fit a Bally Playboy. Back seat folded down - loaded body through hatch, legs next to it, head on passenger seat (have to use right hand to hold head and shift). FYI — yes I got the hatch closed!

City Express (Unspecified year) - Will fit at least one pin comfortably. City Express is rebadged Nissan NV200.

Blazer (1995-2005) - Will fit all standard and wide body pinball machines with back seat folded down.

Equinox (2005+) - Will fit all standard and wide body pinball machines with back seat folded down. System 3s will not fit.

HHR (Unspecified year) - Will NOT fit, can put in head first but will hit roof and stick out back so hatch can't close

Lumina (1995-2001) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

Impala (2006) - System 11 with the backbox removed, but it is a tight fit.

Sonic (Hatchback) (Unspecified year) - EM's will fit, not sure on modern machines.

Suburban (Chevy&GMC) (Unspecified year) - Will fit up to three machines providing one head can be removed(EM, Early SS, or lots of unplugging/unbolting).

Tahoe (Unspecified year) - Will fit all standard and wide body pinball machines with back seat folded down.

Tracker 4 Door (1999-2004) - with the rear seat cushions removed will haul all standard and widebody machines. It still leaves room for a passenger, too. Will also fit modern New In Box - but driver's seat will need to be forward quite a bit.

Trailblazer (2002-2009) - Will fit all standard and wide body pinball machines with back seat folded down. Note: rear seats do not fold down completely flat giving the cargo area a slanted surface - making it more difficult to load a machine (and you must be careful of the cabinet artwork).

Traverse (2009-2014) - Will fit all standard and wide body pinball machines with back seat folded down. Acadia (GMC) will fit Stern in box, Traverse must be unboxed due to hatch shape.

== Chrysler ==

PT Cruiser (Unspecified year) - Will fit with rear seats removed.

Concorde (1993-1997) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

LHS (1994-1997) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

New Yorker (1994-1996) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

Town & Country (Unspecified year) - Fits widebody pin easily with one back seat still up. Rest of the back seats need to be folded down. Head must be folded or removed. Can fit 2 machines easily, possibly 3.

== Dodge ==

Durango (2011+) - Fits any size pin with room to spare. Will fit two regular size pins if the back boxes are removed.

Grand Caravan (Unspecified year) - Fits widebody pin easily with one back seat still up. Rest of the back seats need to be folded down. Head must be folded or removed. Can fit 2 machines easily, possibly 3.

Intrepid (1993-1997) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

Journey (Unspecified year) - Will NOT fit.

Magnum (Unspecified year) - Fits Williams system 3-7 standard width machines with head removed and back seats folded down. Head must be put in flat, then tipped vertical at the gap where the back seats folded. Very tight fit for head box. Definitely will NOT fit WPC machines, or widebodies.

Sprinter Van (Unspecified year) - Fits all machines.

== Eagle ==

Vision (1993-1997) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

== Ford ==

Bronco (1966-1977) - All with tailgate down; backbox folded down or removed.

Bronco Sport (2021-2025+) - All with rear seats folded down; new stern with head folded fits perfectly.

Crown Victoria LTD 4dr (1982-1991) - All standard machines with removable backbox; main cabinet in trunk with trunk lid tied down; backbox on back seat.

Edge (Unspecified year) - Will hold a pin with head folded down.

Edge (2006-2014) - Will fit B/W and modern Stern with vertical space to spare

Edge (2015+) - Folded WPC, Capcom, and modern Stern are a tight fit. The backbox latch may need to be removed to avoid damaging the roof.

Escape (2000-2012) - Will hold a pin with head folded down. 2012 will fit a NIB.

Escape (2013-2016) - Fits Sterns, DE and Sega. Gottlieb System 3's are an inch too long.

Expedition (2007-2015+) - Fits most pins.

Explorer 4 door (1990+) - Will fit all standard and wide body pinball machines with back seat folded down. 2008 will fit NIB Stern.

F-100 (1972-73) - Full bed truck, can hold easily hold two games on legs (not recommended), or up to 6 games on end. 2-3 heads can be snugged onto the bench seat and room for driver.

Fiesta (2007) - Will not fit a folded machine. Appears to be able to fit most EMs and early solid state games with the backbox removed, but the front seats may need to be pushed forward.

Flex (2014, but likely applies to all years) - Will fit all WMS & Stern machines plus a dolly. Will fit games where the head detaches plus a dolly. Will not fit a GTB sys 3 upright without beheading due to cabinet height. Can fit GTB sys 3 laying down. Can fit a WMS game, a dolly, and a third person if you leave the second row passenger seat up. Will fit a boxed Stern, but the box will be crinkled. (i.e. it's tight.)

[[File:Flex with pin.jpg|200px|thumb|none|Ford Flex with pinball machine]] 

Focus wagon (Unspecified year) - Will hold WPC machine + dolly.

Freestar(Unspecified year) - Will hold at least two (one from back, one from side door (sideways)), possibly three if heads are removed or loosened.

Ranger (all years) Will fit.

Transit Cargo Van (2015+) - 8 Fit in a medium or high top Ford Transit cargo van (on their chocks). Just did it, nice ride too.
Loading is super easy with a scissor lift or pin dolly. Back the back of the game to the rear bumper or side door and just stand it up into the van. Walk it to its desired load location, drape it with a moving blanket if you didn't wrap the game prior to loading and ratchet strap it to the wall. If you put them all bottoms (power switch) facing the walls you still have use of rear view mirror. Plenty of room to put legs down the middle or between each game.

Transit Connect (Unspecified year) - Will fit a couple pins.

 

== GMC ==

Acadia (2009-2014) - Will fit all standard and wide body pinball machines with back seat folded down. Acadia will fit Stern in box, Chevy Traverse must be unboxed due to hatch shape.

Envoy (2002-2009) - Will fit all standard and wide body pinball machines with back seat folded down. Note: rear seats do not fold down completely flat giving the cargo area a slanted surface - making it more difficult to load a machine (and you must be careful of the cabinet artwork.

Jimmy (1995-2005) - Will fit all standard and wide body pinball machines with back seat folded down.

Suburban(Chevy&GMC)(Unspecified year) - Will fit up to three machines providing one head can be removed(EM, Early SS, or lots of unplugging/unbolting).

Terrain (2005+) - Will fit all standard and wide body pinball machines with back seat folded down.

GMC Yukon (Unspecified year) - Will fit all standard and wide body pinball machines with back seat folded down.

Yukon XL (Unspecified year) - Will fit up to three machines providing one head can be removed(EM, Early SS, or lots of unplugging/unbolting).

== Honda ==

CR-V (2002-2006, 2012+) - Can fit one pinball machine easily; fold down back of the seat only seat (do not fold it all the way forward) and using cardboard to slide game at angle into the car; coin door should be facing toward the front of the vehicle. 2014 will hold boxed Stern pinball.

Element (2003-2011) - Will hold any pin.

Fit (2001-2014) - Will hold most pins from 70s-current. Including widebody WPCs.

Fit (2013) - A folded Sega Godzilla did not fit, and needed to be turned on its side.

Fit (2015) - Will hold pin but cargo area slightly shorter than old body style.

S2000 (all years) - Will not fit.

Odyssey (1999-2004) - Can fit one pinball machine in the back with the middle seats installed. Can fit two if the middle seats are removed and the machine is slid in through the sliding doors. Front seats may have to be moved forward some to allow the second machine to be slid in.

Odyssey (2004+) - Two EMs with heads off fit in the back with the middle seats still in and heads behind the front seats (but it's tight). For pins with heads folded, only one fits.

Odyssey (2011-2015) - One game will fit in the rear cargo area with the middle seats installed. A new in box game will fit with the middle seats installed if the seatbacks are folded down.

If the handle on the pillar between the doors is removed a second game can be slid in through the sliding doors (with middle seats removed of course). Front seats may have to be moved forward some to allow the second machine to be slid in. The sliding doors do not open as wide as the 1999-2004 models, so you may have to angle the game to get the head into the van. Stern games fit easier through the sliding doors as the head is narrower than WPC and Data East games.

Odyssey (2018) - If you remove the middle row, you can fit 2 Sterns. One horizontal along the middle row, another will slide straight in from the back and it will also fit a dolly straight in.

Pilot (2009) - Can easily fit one pinball machine or possibly two; back two rows of seating need to be folded down; will also fit two standard width games if the heads are removable; has also been used to move one older game with the head removed and one game with the head still on (both standard width games: The Simpsons Pinball
Party and Eight Ball).

Pilot (2010-2015) - Can fit two standard sized machines with folding heads without removing the heads. One machine is loaded through the rear, then turned sideways over the folded down rear seats. Head remains attached and folded down - it will be a tight fit with the headliner (ie - touching it), but works nonetheless without damage. The other game can be placed in the rear with the front of the cabinet facing the side of the sideways facing game sitting on the folded rear seats. Recommend putting some sturdy thick padding between the games just in case. Games moved this way : Williams 1995 "No Fear!" and Sega 1999 "Harley Davidson".

== Hyundai ==
Elantra (2011-2016) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

Santa Fe (2001-2012) - Machines fit easily, can also fit NIB machines.

Tuson (2006) - Will fit one pin. Will also fit NIB Stern with pallet still strapped on (hatch still closes)

Veracruz (Unspecified year) - STTNG fit easily in, but the rear seats don't fold flat. Have to do some maneuvering to get it to slide the rest of the way.

Santa Fe Sport (2015) - We fit in a DE/Sega Maverick but it wasn't easy. It's definitely a 2-person job. Nothing can be under the pin, not even a cargo mat. Take off the back seat headrests, fold the seats down, and slide the back seats as far forward as they'll go. Slide the pin in front-end first, then one person needs to push the back seats down as hard as you can and lift the front of the pin while the other person slowly slides it in from the cargo door. It should just barely fit below the headliner in the cargo door. The angle of the floor above the folded back seats makes things tight, and you have to lift the pin because it can't slide due to the angled floor. Getting it out was much easier and can be done by one person. Or take the head of the pin off and everything would fit with no problem. Update -- a White Water fit with no problem

== Infiniti ==

QX4 (1997-2003) - will fit any one pin.

== Jeep ==
Cherokee: XJ (1997-2001) - Will fit most machines. Pinball 2000 is very tight.

Compass (2007) - Will NOT work. Machine sticks out the back by about 18 inches and hatch does not close. Maybe if emergency situation, but not ideal.

Grand Cherokee (1999-2004) - Can easily fit two wedgies, or one wedgie and one multi player EM game. Typically one wedgie head goes on the passenger seat. The larger of the two heads goes immediately behind the passenger seat. Two 2x4 platforms need to be constructed and used to raise the games above the wheel wells. This model series will also hold 1 DMD style game, with the head on. There is not a lot of vertical clearance, but enough. There is plenty of length and width, the choke point is with the height.

Grand Cherokee (2005-2010) - Not enough vertical clearance to fit a pin without moving the head.

Grand Cherokee (2011-2015) - Should fit most game models, but not much vertical clearance. Well I tried and was able to get a BSD in the back of a 2011 grand Cherokee. It was a loaner I got from a local dealer. It's a standard GC version, so I don't know if options change anything. It has about 30 1/4 inch vertical clearance carpet to opening bottom; giving about 1/2 inch clearance with the BSD head. Don't know about other games/manufacturers, but a Williams WPC does fit. Will not fit NIB Stern (about 1" interference with plastic hatch trim), unboxed fit but still tight. Will not fit Gottlieb System 3 - nothingnesses enough height clearance. Will fit Data East / Sega pins with a vertical clearance of about an inch. Some models come with a removable rubber mat which should be removed for the extra height clearance.

Liberty (2002-2007) - Will fit a pin easily

Trailhawk - Vertical clearance is 28-1/2" and will not fit a WPC/modern folded pin.

Wrangler 2 door models: CJ, YJ, TJ, JK (1986+) - Will NOT fit.

Wrangler Unlimited 4 door model(2007+) - With the rear seats down, holds a Guns N' Roses (with the gun handle), so should hold any pin with a longer-than normal plunger.

== Kia ==

Sorento (2011) - DMD games with the head folded down (i.e. Alvin G Pistol Poker) will '''not''' fit into this vehicle without removing the head. 

Sorento (Unspecified year) - The second generation System 80B cabinet (Raven to Victory) will '''not''' fit through the rear door's opening, when the game is folded. However, the head hinges can be unbolted, so the head is able to slid down the cabinet body descreasing the overall height. The single ground strap going from the body to the head will have to be removed, as will the 2-pin inline connection used for the 110v feeding the fluorescent lamp. The main harness which is snaked between the driver board and CPU board may have to be removed from some of the straps holding it in place. 

The game used to confirm this was a Hollywood Heat. Even though Rock has the same backbox as the other games mentioned, it may acually fit, because the cabinet body is not as tall.

Soul (Unspecified year) - With the rear seats down, the Soul can fit either a Gottlieb System 1 game or a Bally -17 game with the backbox removed.

Sportage 2nd Gen(2005-2010) - Most pins will fit, Gottlieb System 3 are too tight and must be on their sides.

Sportage 3rd Gen(2011+) - Will NOT fit.

Telluride Gen(2020+) - Will fit NIB Stern and most other pins.

== Land Rover ==
Range Rover - Non Sport Model (Unspecified year) - Will fit a pinball machine

Range Rover - Sport Model (Unspecified year) - Will NOT fit

== Lexus ==
RX 350 (2012) - Will fit WPC pinball machines

RX 330 (2005) - Will fit almost every make of pinball machine (with the sole exception of Data East)

== Mazda ==

CX-5 (2012-up) - Should fit any pin backbox folded, system 3 will be tight vertically

CX-7 (2010) - Tried to move a badcats and it did not fit. Needed about another 2 inches of clearance. So, pins with a backbox that folds down will not fit; but older em/ss where the head comes off should be fine. You also could unbolt the head of the ones that fold and bring it down the playfield a bit; and they might fit.

CX-9 (2013) - Will fit all modern, folding pins. Biggest I've personally tried is Fish Tales with the topper.

Mazda5 (2010) - Will fit most modern, folding pins.

Tribute (2002) - Will fit all modern, folding pins.

== Mitsubishi ==

Outlander (2009) - Has been used to move Williams Black Knight, Gottlieb 300, Williams Pin*Bot, Williams Flash, Gottlieb World Fair; will likely not hold a game with a non-standard plunger, such as a Terminator 2, Shadow, or Guns N' Roses.

== Mercedes ==

Benz ML-350 (2005) - Will fit most pins.

== Nissan ==

NV200 (2013-19) - Will fit at least one pin comfortably. Cargo area is 81" deep (with bulkhead partition installed) x 48" wide between wheel wells.

Pathfinder (Unspecified year) - Will fit any standard or wide body with the two back rows of seats folded down.

Rogue (2012) - Folded WPC will not fit. 29" from floor without mat to top of hatch. Must remove head.

Rogue Sport (2017) - Bally Arena fit snug when laid on its side, still had room length wise, height was snug.Had room for a dolly as well

[[File:Arena Pinball 2017 Nissan Rogue Sport.jpg|200px|thumb|none|Nissan Rouge Sport with Pinball Machine]] 

Rogue (2023) - WPC will fit (Fish Tales with fishing rod shooter). SPIKE 2 will fit.

Murano (2012) - Folded WPC will not fit. Bumps on ceiling for hatch hinge and seat belt shoulder strap.

Versa (Unspecified year) - Will fit a WPC game, if the head is removed. Body sits in passenger seat with seat tilted all the way back. Driver's side rear door needs to have its pin removed, which limits how far the door opens. Cabinet can be slid into vehicle through driver's side rear. It's crazy, but I've seen this done first hand!

X-Trail (Unspecified year) - Will fit any standard or wide body with the rear seats folded down.

Xterra (2005-2015+) - Will fit most pins.

== Oldsmobile ==

Cutlass Supreme (1995) - Was *just* able to handle the body of a 1978 Bally 'Lost World' accross the back seats (doors closed properly, but with very little free room); with the head removed and laid on its back in the trunk. Other GM W-Body cars of this era and even newer ones *may* be able to accomodate an equivalently sized game similarly.

== Pontiac ==

Aztek (2001-2005) - Will fit most machines.

Matrix (2003-2010) - Will fit machines with head removed (including folding heads); includes WPC, System 11, Bally SS, and Bally wide body (specifically Paragon); load body shooter first, then slide in head next to it; place moving blanket between them and a ratchet strap over top. Hatch opening is too rounded by about 2" to fit with folding heads attached.

Vibe (Unspecified year) - Will NOT fit a pinball, hatch is too rounded.

== Porsche ==

Cayenne (Unspecified year) - Will NOT fit a pinball, hatch is too rounded. It will fit an EM (GTB Rack-A-Ball).

== Renaut ==

Clio (Unspecified year) - Everyone of my pinballs have been transported in my Renault Clio! In the last trip... a Firepower, me, my girlfriend and her Australian shepherd.

== Saturn ==

Outlook (2007-2010) - Will fit all standard and wide body pinball machines with back seat folded down.

Vue (Unspecified year) - machines must be placed on their sides, but will fit.

== Scion ==

Scion Xb (2003-2006) - Will fit any pin.

Scion Xb (2008+) - Will fit any pin, system 3 will scrape the roof but will squeeze in

Scion XD (all years) - Standard body pin with head removed will fit.

== Subaru ==

Forester (2000+) - Back seats folded down - fits WPC, early 80's Bally, modern Stern, Williams Joust. Gottlieb System 3, late 80's Bally, Safecracker, Banzai Run has to be put in on their side.

Forester (2014-2015) - Back seats folded down - fits all early standard/widebody SS pins with the backbox removed. Fits pins with a folded height of 31" or less. Fits Williams System 11 & WPC standard/widebody, but may scrape the roof lining. Fits folding Gottlieb 80A games. Gottlieb System 80B & System 3 DMD games need to be on their side, or the backbox needs to be removed. Gottlieb ultra widebody games are a difficult fit--best way is lay the backbox down on the cabinet, but it will scrape the roof lining. Pin 2000 games will fit, but it's tight--the passenger seat needs to be pushed fully forward and the backbox must be removed and placed on its side.

GL Wagon (1979-1989) - All standard machines with removable backbox; back seat folded down.

Impreza hatchback (Unspecified year) - Gottlieb EMs (2 player) and Bally SS machines fit.

Outback (Unspecified year) - will NOT fit. Maybe able to get in mostly, but can't close hatch...not a good option for long trips.

Outback (2016) - will NOT fit a standard modern Stern machine. Will fit standard width early solid state machines that have removable (Non-hinged) head boxes. Tight fit around the hatch.

Outback Legacy (1994-1998) - will fit most pins. System 3 hang out the back about 6".

Outback Legacy (1998-2003) - will fit most pins with the child restraint anchor removed.

Outback Legacy (2003-2009) - should fit most pins.

== Tesla ==

Model X - Will fit with great difficulty across the back seats loaded in sideways.
[[File:pin_in_model_X.jpg|300px|thumb|none|Model X with pinball machine]]

Cybertruck - Will not fit any machine from any manufacturer with head attached and tonneau cover closed.[[File:cybertruck_pinball.jpg|300px|thumb|none|Cybertruck with pinball machine bulging out of its storage cubby]]

== Toyota ==

4Runner (2009+) - Will fit most modern machines. NIB will fit.

Corolla Wagon/hatchback (1992) - Will fit most modern machines.

FJ Cruiser (2007+) - Will fit most machines. NIB Stern will not allow hatch to close (about 6") - a bungee cord will help.

Highlander (2000-2007, 2013) - Will fit most modern machines.

Highlander (2018) - Will fit most modern machines. 2 early SS or EMs will fit between the wheel wells if you turn them on their sides, or put one in the front of the wheel wells. You can lay the heads on top of the bodies. There are 2 tiedowns near the 3rd row of seats.

Matrix (2003-2013) - Will fit machines with head removed (including folding heads); includes WPC, System 11, Bally SS, and Bally wide body (specifically Paragon); load body shooter first, then slide in head next to it; place moving blanket between them and a ratchet strap over top. The hatch opening is too rounded by about 2" to fit with folding heads attached.

Prius C (2012-2019) - If the backbox/head is removed, the back seats folded flat and the front seats moved up a Prius C will fit the body of a standard pinball machine with the rear hatch closed. It is recommended to put the taller head end of the machine in first so that it touches the front seats, this way it wont interfere with the sloped hatch and the front seats can be moved further back however it will fit in both directions. Should be able to hold a head removed wide body as there is about 38 1/2 inches of clear width in the hatch however that is untested. You maybe able to fit the backbox in the passenger seat with a pin in the back however it would be extremely tight, if its close just make another trip or bring another car and put it in the trunk. I was able to fit a standard dolly in the Prius C at the same time as the body of a pin but your results will differ based on your specific dolly.

Prius V (Unspecified year) - I was pleased to discover that the Prius V could handle a Black Hole and a Paragon. Different trips of course.

Prius 2010 Model 3 - Take the head off, rear seats down, cabinet with coin door towards rear. Front Passenger seat fully reclined, head spans over center console and onto the dash (wrapped in moving blanket) - propped up to keep head from kicking the car into neutral. - Not recommended - but it can be done!

RAV4 (Unspecified year) - Must remove rear seats.

RAV4 (2005-2015) - Fits most pins.

RAV4 (2007) - Easily handles modern games including space for an appliance dolly, after folding down the rear seats. Haven't tried NIB. Very flat entry and mostly flat floor (except for a little bump where the seats fold) so easy to load and unload, even by yourself.

RAV4 (2013) - Fist most pins, including Gottlieb System 3.

RAV4 (2019 - 2025, 5th generation - not plug-in) - Fits a WPC, but with some issues. Be certain to load with the folded down head towards the back. The seats do not lie flat which makes sliding the pin difficult and raises the front towards the roof - although a few loads will compress the seats flatter. Try taking off any rubber protection on the back of the seat to increase headroom and add a thin smooth sheet of wood (Luan or similar) to make sliding in and out easier. If the game has a gun for the shooter, it can touch or come close to the driver's seat. Connect ratchet straps to brackets that hold the seats locked - front and back to keep the pin stable. It is unlikely to fit a Gottlieb System 4 with the head connected.

RAV4 (5th generation - plug-in) - Plug-in models have less headroom making leaving the head on most games impossible.

RAV4 (2026 - 6th Generation) - No information available yet.

Sequoia (2008) - Fits pins no problem.

Sienna (2013) - will hold 2 pins with the middle seats removed. Both loaded from the back but the first pin is turned 90 degrees behind the front seats, second pin was loaded back box first. One pin will fit a 2004 with second row seats in place.

Tacoma Pre-Runner (Unspecified year) - fits great.

Venza (Unspecified year; possibly 2009 or 2010) - Back seat folded down. Tried to shoehorn a WMS Cyclone (System 11). Had to remove nuts from head side of hinge, and slide head forward approx. 3-4 inches on top of cabinet. Ground braid from cab to head had to be removed from stud in head. Very, very, very tight fit! Note: tallest measurement with head folded on Cyclone was 30". 

== Volkswagen ==

Atlas (2019-2023) - Will fit 1 machine without problems.

Golf TDi SportWagon (2015) - Will hold a machine; a bit too tight for a fold-down newer game though. Seats don't fold down flat, so there is a bit of a 'rise' on the folded seats. Have *not* tried the two '69' wedgies trick yet.

Jetta TDi SportWagon (2010-14) - Will hold a machine; a bit too tight for a fold-down newer game though. Seats fold down completely and lay flat. Can fit two wedgehead coffins on their sides in a '69' position. Then the two heads can barely fit on the passenger seat.

Passat Wagon (2005) - 30.5 inches of height. Will fit most machines, even DMD's. Dr Who & TZ fit no problem.

Sharan(Unspecified year) - Will fit 1 machine without problems.

Tiguan (2011) - Was able to fit a T2. It was fairly easy to get in but a bit tricky to remove.

Tiguan (2012) - Will NOT fit newer folded pins (about 1" too short), Early SS and EMs fit fine with the head removed, System 11 has also fit.

Toureg (Unspecified year) - Will hold machine, at least an early 70's version (like Bally Circus)

== Volvo ==

240DL Station Wagon (1984) - Almost any pin fits (except Hercules) with the head folded down.

Vehicles for Moving Pinball Machines

2026-01-01T15:19:29Z

The Hammer: /* Toyota */ Fixed typo. Added additional information about 5th generation. Deleted comment about RAV4 2022 which is a 5th generation RAV.

=Introduction=
Often on the rec.games.pinball newsgroup, there are discussions over which vehicles will or will not hold a pinball machine (Here's a link to the [http://groups.google.com/group/rec.games.pinball/search?hl=en&group=rec.games.pinball&q=will+a+pin+fit+in+a question as asked on RGP] and [https://pinside.com/pinball/forum/topic/vehicles-that-a-pinball-machine-fits-in a discussion on pinside]).

Word of caution: Gottlieb System 3 games (and some 80B games) with the head/backbox folded for transport are taller than any other manufacturer / platform. The folded height for Gottlieb System 3 games is about 34", and the width of the backbox is 27". The height of the cabinet when the backbox is removed is 28". However, Gottlieb's "street level" System 3 games are less tall when folded for transport, and are instead about the same height as other traditional folded games from other manufacturers. 

Below is a listing of vehicles, as well as specifics regarding said vehicles.

=Cabinet Sizes=

==Standard Cabinet Sizes==

{| class="wikitable sortable"
!Manufacturer
!System
!Game Style
!Folded Height
!Cabinet Body Dimensions
!Backbox Dimensions
!Notes
|-
|Gottlieb
|System 1
|Standard
|n/a
|H:21", L:52" (without shooter), 22-1/4"
|H:29-1/2", W:28-1/4", D:10-1/2" (bottom) to 12" (top)
|
|-
|Gottlieb
|System 80A/80B
|Standard
|26"
|H:19.5", L:49.5" (with shooter rod), W22"
|W:28.5"
|Only games with the thin backbox (Super Orbit, Royal Flush Deluxe, Amazon Hunt, Rack 'em Up, Ready Aim Fire, Jacks to Open, Alien Star, The Games, El Dorado, Touchdown, Ice Fever, Chicago Cubs Triple Play, Bounty Hunter, Tag-Team)
|-
|Gottlieb
|System 3, DMD
|Standard
|34"
|H:28", L:54-1/2" (with shooter rod), W:27"
|W:27"
|Folded height is taller than any other manufacturer. A few games have toppers.
|-
|Bally
|6803
|Standard
|33"
|H:?, L:53" (with shooter rod), 50-1/2" (w/o shooter rod) W:?"
|
|Motordome, Special Forces, Hardbody, etc. Dungeons & Dragons, Blackwater 100, and Escape from the Lost World are exceptions
|-
|Bally/Williams
|WPC
|Standard
|29-1/2"
|H:24", L:52" (without shooter), W:22-1/2"
|H:28-1/2", W:28-3/4", D:6-1/2" (bottom) to 9-3/4" (top)
|Some games come with a gun handle, which adds 6"-7" to the length of the cabinet.
|-
|Bally/Williams
|WPC
|SuperPin
|29-1/2"
|H:24", L:52" (without shooter), W:25"
|H:28-1/2", W:29", D:6-1/2" (bottom) to 9-3/4" (top)
|Some games come with a gun handle, which adds 6"-7" to the length of the cabinet.
|-
|}

==Cabinet Size Exceptions==

{| class="wikitable sortable"
!Manufacturer
!Game Title
!System
!Game Style
!Folded Dimensions
!Cabinet Dimensions
!Backbox Dimensions
!Notes
|-
|}

=Vehicles=

== Acura ==

MDX (2000-2006) - Will fit most games. STTNG fit.

MDX (2007-2013) - 2007+ lowered hatch height, TAF barely fit and left marks in ceiling. Will fit Stern, DE and Williams Widebody

RDX (Unspecified Year) - pins fit great, moved newer Sterns and older Bally's with no problems.

RDX(2014+) - Will not fit a pin

== Audi ==

A3 Hatchback (Unspecified year) - fits a pin with the backbox disconnected.

Q7 (Unspecified year) - about 1" too short

Q7 w/ third row seating (2013) - BARELY fits...very tight

== BMW ==

525 Wagon (1993) - Fits any older pin without folding head. Folding head units must be removed.

X3 first generation E83 (2003-2010) & second generation F25 (2010-2014) - Fits any standard pin when folded down (not in box)

X5 - Fits most standard sized modern pins. With Gottlieb DMD's you need to loosen the head and slide it down a little.

== Buick ==

Enclave (2008-Current) - Will fit all standard and wide body pinball machines with back seat folded down, some games like Gottlieb System 3 may need to be put on their sides.

Rendezvous (2001-2007) - Will fit all standard and wide body pinball machines with back seat folded down.

== Cadillac ==

SRX (2004-2009) - Will fit most standard and wide body pinball machines. The backbox needs to be removed on Gottlieb System 3 pins.

SRX (2010+) - Will not fit

== Chevrolet ==

Avalanche (Unspecified year) - Will fit at least two pins (and 5 people).

Chevette (1985) - fit a Bally Playboy. Back seat folded down - loaded body through hatch, legs next to it, head on passenger seat (have to use right hand to hold head and shift). FYI — yes I got the hatch closed!

City Express (Unspecified year) - Will fit at least one pin comfortably. City Express is rebadged Nissan NV200.

Blazer (1995-2005) - Will fit all standard and wide body pinball machines with back seat folded down.

Equinox (2005+) - Will fit all standard and wide body pinball machines with back seat folded down. System 3s will not fit.

HHR (Unspecified year) - Will NOT fit, can put in head first but will hit roof and stick out back so hatch can't close

Lumina (1995-2001) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

Impala (2006) - System 11 with the backbox removed, but it is a tight fit.

Sonic (Hatchback) (Unspecified year) - EM's will fit, not sure on modern machines.

Suburban (Chevy&GMC) (Unspecified year) - Will fit up to three machines providing one head can be removed(EM, Early SS, or lots of unplugging/unbolting).

Tahoe (Unspecified year) - Will fit all standard and wide body pinball machines with back seat folded down.

Tracker 4 Door (1999-2004) - with the rear seat cushions removed will haul all standard and widebody machines. It still leaves room for a passenger, too. Will also fit modern New In Box - but driver's seat will need to be forward quite a bit.

Trailblazer (2002-2009) - Will fit all standard and wide body pinball machines with back seat folded down. Note: rear seats do not fold down completely flat giving the cargo area a slanted surface - making it more difficult to load a machine (and you must be careful of the cabinet artwork).

Traverse (2009-2014) - Will fit all standard and wide body pinball machines with back seat folded down. Acadia (GMC) will fit Stern in box, Traverse must be unboxed due to hatch shape.

== Chrysler ==

PT Cruiser (Unspecified year) - Will fit with rear seats removed.

Concorde (1993-1997) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

LHS (1994-1997) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

New Yorker (1994-1996) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

Town & Country (Unspecified year) - Fits widebody pin easily with one back seat still up. Rest of the back seats need to be folded down. Head must be folded or removed. Can fit 2 machines easily, possibly 3.

== Dodge ==

Durango (2011+) - Fits any size pin with room to spare. Will fit two regular size pins if the back boxes are removed.

Grand Caravan (Unspecified year) - Fits widebody pin easily with one back seat still up. Rest of the back seats need to be folded down. Head must be folded or removed. Can fit 2 machines easily, possibly 3.

Intrepid (1993-1997) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

Journey (Unspecified year) - Will NOT fit.

Magnum (Unspecified year) - Fits Williams system 3-7 standard width machines with head removed and back seats folded down. Head must be put in flat, then tipped vertical at the gap where the back seats folded. Very tight fit for head box. Definitely will NOT fit WPC machines, or widebodies.

Sprinter Van (Unspecified year) - Fits all machines.

== Eagle ==

Vision (1993-1997) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

== Ford ==

Bronco (1966-1977) - All with tailgate down; backbox folded down or removed.

Bronco Sport (2021-2025+) - All with rear seats folded down; new stern with head folded fits perfectly.

Crown Victoria LTD 4dr (1982-1991) - All standard machines with removable backbox; main cabinet in trunk with trunk lid tied down; backbox on back seat.

Edge (Unspecified year) - Will hold a pin with head folded down.

Edge (2006-2014) - Will fit B/W and modern Stern with vertical space to spare

Edge (2015+) - Folded WPC, Capcom, and modern Stern are a tight fit. The backbox latch may need to be removed to avoid damaging the roof.

Escape (2000-2012) - Will hold a pin with head folded down. 2012 will fit a NIB.

Escape (2013-2016) - Fits Sterns, DE and Sega. Gottlieb System 3's are an inch too long.

Expedition (2007-2015+) - Fits most pins.

Explorer 4 door (1990+) - Will fit all standard and wide body pinball machines with back seat folded down. 2008 will fit NIB Stern.

F-100 (1972-73) - Full bed truck, can hold easily hold two games on legs (not recommended), or up to 6 games on end. 2-3 heads can be snugged onto the bench seat and room for driver.

Fiesta (2007) - Will not fit a folded machine. Appears to be able to fit most EMs and early solid state games with the backbox removed, but the front seats may need to be pushed forward.

Flex (2014, but likely applies to all years) - Will fit all WMS & Stern machines plus a dolly. Will fit games where the head detaches plus a dolly. Will not fit a GTB sys 3 upright without beheading due to cabinet height. Can fit GTB sys 3 laying down. Can fit a WMS game, a dolly, and a third person if you leave the second row passenger seat up. Will fit a boxed Stern, but the box will be crinkled. (i.e. it's tight.)

[[File:Flex with pin.jpg|200px|thumb|none|Ford Flex with pinball machine]] 

Focus wagon (Unspecified year) - Will hold WPC machine + dolly.

Freestar(Unspecified year) - Will hold at least two (one from back, one from side door (sideways)), possibly three if heads are removed or loosened.

Ranger (all years) Will fit.

Transit Cargo Van (2015+) - 8 Fit in a medium or high top Ford Transit cargo van (on their chocks). Just did it, nice ride too.
Loading is super easy with a scissor lift or pin dolly. Back the back of the game to the rear bumper or side door and just stand it up into the van. Walk it to its desired load location, drape it with a moving blanket if you didn't wrap the game prior to loading and ratchet strap it to the wall. If you put them all bottoms (power switch) facing the walls you still have use of rear view mirror. Plenty of room to put legs down the middle or between each game.

Transit Connect (Unspecified year) - Will fit a couple pins.

 

== GMC ==

Acadia (2009-2014) - Will fit all standard and wide body pinball machines with back seat folded down. Acadia will fit Stern in box, Chevy Traverse must be unboxed due to hatch shape.

Envoy (2002-2009) - Will fit all standard and wide body pinball machines with back seat folded down. Note: rear seats do not fold down completely flat giving the cargo area a slanted surface - making it more difficult to load a machine (and you must be careful of the cabinet artwork.

Jimmy (1995-2005) - Will fit all standard and wide body pinball machines with back seat folded down.

Suburban(Chevy&GMC)(Unspecified year) - Will fit up to three machines providing one head can be removed(EM, Early SS, or lots of unplugging/unbolting).

Terrain (2005+) - Will fit all standard and wide body pinball machines with back seat folded down.

GMC Yukon (Unspecified year) - Will fit all standard and wide body pinball machines with back seat folded down.

Yukon XL (Unspecified year) - Will fit up to three machines providing one head can be removed(EM, Early SS, or lots of unplugging/unbolting).

== Honda ==

CR-V (2002-2006, 2012+) - Can fit one pinball machine easily; fold down back of the seat only seat (do not fold it all the way forward) and using cardboard to slide game at angle into the car; coin door should be facing toward the front of the vehicle. 2014 will hold boxed Stern pinball.

Element (2003-2011) - Will hold any pin.

Fit (2001-2014) - Will hold most pins from 70s-current. Including widebody WPCs.

Fit (2013) - A folded Sega Godzilla did not fit, and needed to be turned on its side.

Fit (2015) - Will hold pin but cargo area slightly shorter than old body style.

S2000 (all years) - Will not fit.

Odyssey (1999-2004) - Can fit one pinball machine in the back with the middle seats installed. Can fit two if the middle seats are removed and the machine is slid in through the sliding doors. Front seats may have to be moved forward some to allow the second machine to be slid in.

Odyssey (2004+) - Two EMs with heads off fit in the back with the middle seats still in and heads behind the front seats (but it's tight). For pins with heads folded, only one fits.

Odyssey (2011-2015) - One game will fit in the rear cargo area with the middle seats installed. A new in box game will fit with the middle seats installed if the seatbacks are folded down.

If the handle on the pillar between the doors is removed a second game can be slid in through the sliding doors (with middle seats removed of course). Front seats may have to be moved forward some to allow the second machine to be slid in. The sliding doors do not open as wide as the 1999-2004 models, so you may have to angle the game to get the head into the van. Stern games fit easier through the sliding doors as the head is narrower than WPC and Data East games.

Odyssey (2018) - If you remove the middle row, you can fit 2 Sterns. One horizontal along the middle row, another will slide straight in from the back and it will also fit a dolly straight in.

Pilot (2009) - Can easily fit one pinball machine or possibly two; back two rows of seating need to be folded down; will also fit two standard width games if the heads are removable; has also been used to move one older game with the head removed and one game with the head still on (both standard width games: The Simpsons Pinball
Party and Eight Ball).

Pilot (2010-2015) - Can fit two standard sized machines with folding heads without removing the heads. One machine is loaded through the rear, then turned sideways over the folded down rear seats. Head remains attached and folded down - it will be a tight fit with the headliner (ie - touching it), but works nonetheless without damage. The other game can be placed in the rear with the front of the cabinet facing the side of the sideways facing game sitting on the folded rear seats. Recommend putting some sturdy thick padding between the games just in case. Games moved this way : Williams 1995 "No Fear!" and Sega 1999 "Harley Davidson".

== Hyundai ==
Elantra (2011-2016) - All standard machines with removable backbox; main cabinet on back seat; backbox in trunk.

Santa Fe (2001-2012) - Machines fit easily, can also fit NIB machines.

Tuson (2006) - Will fit one pin. Will also fit NIB Stern with pallet still strapped on (hatch still closes)

Veracruz (Unspecified year) - STTNG fit easily in, but the rear seats don't fold flat. Have to do some maneuvering to get it to slide the rest of the way.

Santa Fe Sport (2015) - We fit in a DE/Sega Maverick but it wasn't easy. It's definitely a 2-person job. Nothing can be under the pin, not even a cargo mat. Take off the back seat headrests, fold the seats down, and slide the back seats as far forward as they'll go. Slide the pin in front-end first, then one person needs to push the back seats down as hard as you can and lift the front of the pin while the other person slowly slides it in from the cargo door. It should just barely fit below the headliner in the cargo door. The angle of the floor above the folded back seats makes things tight, and you have to lift the pin because it can't slide due to the angled floor. Getting it out was much easier and can be done by one person. Or take the head of the pin off and everything would fit with no problem. Update -- a White Water fit with no problem

== Infiniti ==

QX4 (1997-2003) - will fit any one pin.

== Jeep ==
Cherokee: XJ (1997-2001) - Will fit most machines. Pinball 2000 is very tight.

Compass (2007) - Will NOT work. Machine sticks out the back by about 18 inches and hatch does not close. Maybe if emergency situation, but not ideal.

Grand Cherokee (1999-2004) - Can easily fit two wedgies, or one wedgie and one multi player EM game. Typically one wedgie head goes on the passenger seat. The larger of the two heads goes immediately behind the passenger seat. Two 2x4 platforms need to be constructed and used to raise the games above the wheel wells. This model series will also hold 1 DMD style game, with the head on. There is not a lot of vertical clearance, but enough. There is plenty of length and width, the choke point is with the height.

Grand Cherokee (2005-2010) - Not enough vertical clearance to fit a pin without moving the head.

Grand Cherokee (2011-2015) - Should fit most game models, but not much vertical clearance. Well I tried and was able to get a BSD in the back of a 2011 grand Cherokee. It was a loaner I got from a local dealer. It's a standard GC version, so I don't know if options change anything. It has about 30 1/4 inch vertical clearance carpet to opening bottom; giving about 1/2 inch clearance with the BSD head. Don't know about other games/manufacturers, but a Williams WPC does fit. Will not fit NIB Stern (about 1" interference with plastic hatch trim), unboxed fit but still tight. Will not fit Gottlieb System 3 - nothingnesses enough height clearance. Will fit Data East / Sega pins with a vertical clearance of about an inch. Some models come with a removable rubber mat which should be removed for the extra height clearance.

Liberty (2002-2007) - Will fit a pin easily

Trailhawk - Vertical clearance is 28-1/2" and will not fit a WPC/modern folded pin.

Wrangler 2 door models: CJ, YJ, TJ, JK (1986+) - Will NOT fit.

Wrangler Unlimited 4 door model(2007+) - With the rear seats down, holds a Guns N' Roses (with the gun handle), so should hold any pin with a longer-than normal plunger.

== Kia ==

Sorento (2011) - DMD games with the head folded down (i.e. Alvin G Pistol Poker) will '''not''' fit into this vehicle without removing the head. 

Sorento (Unspecified year) - The second generation System 80B cabinet (Raven to Victory) will '''not''' fit through the rear door's opening, when the game is folded. However, the head hinges can be unbolted, so the head is able to slid down the cabinet body descreasing the overall height. The single ground strap going from the body to the head will have to be removed, as will the 2-pin inline connection used for the 110v feeding the fluorescent lamp. The main harness which is snaked between the driver board and CPU board may have to be removed from some of the straps holding it in place. 

The game used to confirm this was a Hollywood Heat. Even though Rock has the same backbox as the other games mentioned, it may acually fit, because the cabinet body is not as tall.

Soul (Unspecified year) - With the rear seats down, the Soul can fit either a Gottlieb System 1 game or a Bally -17 game with the backbox removed.

Sportage 2nd Gen(2005-2010) - Most pins will fit, Gottlieb System 3 are too tight and must be on their sides.

Sportage 3rd Gen(2011+) - Will NOT fit.

Telluride Gen(2020+) - Will fit NIB Stern and most other pins.

== Land Rover ==
Range Rover - Non Sport Model (Unspecified year) - Will fit a pinball machine

Range Rover - Sport Model (Unspecified year) - Will NOT fit

== Lexus ==
RX 350 (2012) - Will fit WPC pinball machines

RX 330 (2005) - Will fit almost every make of pinball machine (with the sole exception of Data East)

== Mazda ==

CX-5 (2012-up) - Should fit any pin backbox folded, system 3 will be tight vertically

CX-7 (2010) - Tried to move a badcats and it did not fit. Needed about another 2 inches of clearance. So, pins with a backbox that folds down will not fit; but older em/ss where the head comes off should be fine. You also could unbolt the head of the ones that fold and bring it down the playfield a bit; and they might fit.

CX-9 (2013) - Will fit all modern, folding pins. Biggest I've personally tried is Fish Tales with the topper.

Mazda5 (2010) - Will fit most modern, folding pins.

Tribute (2002) - Will fit all modern, folding pins.

== Mitsubishi ==

Outlander (2009) - Has been used to move Williams Black Knight, Gottlieb 300, Williams Pin*Bot, Williams Flash, Gottlieb World Fair; will likely not hold a game with a non-standard plunger, such as a Terminator 2, Shadow, or Guns N' Roses.

== Mercedes ==

Benz ML-350 (2005) - Will fit most pins.

== Nissan ==

NV200 (2013-19) - Will fit at least one pin comfortably. Cargo area is 81" deep (with bulkhead partition installed) x 48" wide between wheel wells.

Pathfinder (Unspecified year) - Will fit any standard or wide body with the two back rows of seats folded down.

Rogue (2012) - Folded WPC will not fit. 29" from floor without mat to top of hatch. Must remove head.

Rogue Sport (2017) - Bally Arena fit snug when laid on its side, still had room length wise, height was snug.Had room for a dolly as well

[[File:Arena Pinball 2017 Nissan Rogue Sport.jpg|200px|thumb|none|Nissan Rouge Sport with Pinball Machine]] 

Rogue (2023) - WPC will fit (Fish Tales with fishing rod shooter). SPIKE 2 will fit.

Murano (2012) - Folded WPC will not fit. Bumps on ceiling for hatch hinge and seat belt shoulder strap.

Versa (Unspecified year) - Will fit a WPC game, if the head is removed. Body sits in passenger seat with seat tilted all the way back. Driver's side rear door needs to have its pin removed, which limits how far the door opens. Cabinet can be slid into vehicle through driver's side rear. It's crazy, but I've seen this done first hand!

X-Trail (Unspecified year) - Will fit any standard or wide body with the rear seats folded down.

Xterra (2005-2015+) - Will fit most pins.

== Oldsmobile ==

Cutlass Supreme (1995) - Was *just* able to handle the body of a 1978 Bally 'Lost World' accross the back seats (doors closed properly, but with very little free room); with the head removed and laid on its back in the trunk. Other GM W-Body cars of this era and even newer ones *may* be able to accomodate an equivalently sized game similarly.

== Pontiac ==

Aztek (2001-2005) - Will fit most machines.

Matrix (2003-2010) - Will fit machines with head removed (including folding heads); includes WPC, System 11, Bally SS, and Bally wide body (specifically Paragon); load body shooter first, then slide in head next to it; place moving blanket between them and a ratchet strap over top. Hatch opening is too rounded by about 2" to fit with folding heads attached.

Vibe (Unspecified year) - Will NOT fit a pinball, hatch is too rounded.

== Porsche ==

Cayenne (Unspecified year) - Will NOT fit a pinball, hatch is too rounded. It will fit an EM (GTB Rack-A-Ball).

== Renaut ==

Clio (Unspecified year) - Everyone of my pinballs have been transported in my Renault Clio! In the last trip... a Firepower, me, my girlfriend and her Australian shepherd.

== Saturn ==

Outlook (2007-2010) - Will fit all standard and wide body pinball machines with back seat folded down.

Vue (Unspecified year) - machines must be placed on their sides, but will fit.

== Scion ==

Scion Xb (2003-2006) - Will fit any pin.

Scion Xb (2008+) - Will fit any pin, system 3 will scrape the roof but will squeeze in

Scion XD (all years) - Standard body pin with head removed will fit.

== Subaru ==

Forester (2000+) - Back seats folded down - fits WPC, early 80's Bally, modern Stern, Williams Joust. Gottlieb System 3, late 80's Bally, Safecracker, Banzai Run has to be put in on their side.

Forester (2014-2015) - Back seats folded down - fits all early standard/widebody SS pins with the backbox removed. Fits pins with a folded height of 31" or less. Fits Williams System 11 & WPC standard/widebody, but may scrape the roof lining. Fits folding Gottlieb 80A games. Gottlieb System 80B & System 3 DMD games need to be on their side, or the backbox needs to be removed. Gottlieb ultra widebody games are a difficult fit--best way is lay the backbox down on the cabinet, but it will scrape the roof lining. Pin 2000 games will fit, but it's tight--the passenger seat needs to be pushed fully forward and the backbox must be removed and placed on its side.

GL Wagon (1979-1989) - All standard machines with removable backbox; back seat folded down.

Impreza hatchback (Unspecified year) - Gottlieb EMs (2 player) and Bally SS machines fit.

Outback (Unspecified year) - will NOT fit. Maybe able to get in mostly, but can't close hatch...not a good option for long trips.

Outback (2016) - will NOT fit a standard modern Stern machine. Will fit standard width early solid state machines that have removable (Non-hinged) head boxes. Tight fit around the hatch.

Outback Legacy (1994-1998) - will fit most pins. System 3 hang out the back about 6".

Outback Legacy (1998-2003) - will fit most pins with the child restraint anchor removed.

Outback Legacy (2003-2009) - should fit most pins.

== Tesla ==

Model X - Will fit with great difficulty across the back seats loaded in sideways.
[[File:pin_in_model_X.jpg|300px|thumb|none|Model X with pinball machine]]

Cybertruck - Will not fit any machine from any manufacturer with head attached and tonneau cover closed.[[File:cybertruck_pinball.jpg|300px|thumb|none|Cybertruck with pinball machine bulging out of its storage cubby]]

== Toyota ==

4Runner (2009+) - Will fit most modern machines. NIB will fit.

Corolla Wagon/hatchback (1992) - Will fit most modern machines.

FJ Cruiser (2007+) - Will fit most machines. NIB Stern will not allow hatch to close (about 6") - a bungee cord will help.

Highlander (2000-2007, 2013) - Will fit most modern machines.

Highlander (2018) - Will fit most modern machines. 2 early SS or EMs will fit between the wheel wells if you turn them on their sides, or put one in the front of the wheel wells. You can lay the heads on top of the bodies. There are 2 tiedowns near the 3rd row of seats.

Matrix (2003-2013) - Will fit machines with head removed (including folding heads); includes WPC, System 11, Bally SS, and Bally wide body (specifically Paragon); load body shooter first, then slide in head next to it; place moving blanket between them and a ratchet strap over top. The hatch opening is too rounded by about 2" to fit with folding heads attached.

Prius C (2012-2019) - If the backbox/head is removed, the back seats folded flat and the front seats moved up a Prius C will fit the body of a standard pinball machine with the rear hatch closed. It is recommended to put the taller head end of the machine in first so that it touches the front seats, this way it wont interfere with the sloped hatch and the front seats can be moved further back however it will fit in both directions. Should be able to hold a head removed wide body as there is about 38 1/2 inches of clear width in the hatch however that is untested. You maybe able to fit the backbox in the passenger seat with a pin in the back however it would be extremely tight, if its close just make another trip or bring another car and put it in the trunk. I was able to fit a standard dolly in the Prius C at the same time as the body of a pin but your results will differ based on your specific dolly.

Prius V (Unspecified year) - I was pleased to discover that the Prius V could handle a Black Hole and a Paragon. Different trips of course.

Prius 2010 Model 3 - Take the head off, rear seats down, cabinet with coin door towards rear. Front Passenger seat fully reclined, head spans over center console and onto the dash (wrapped in moving blanket) - propped up to keep head from kicking the car into neutral. - Not recommended - but it can be done!

RAV4 (Unspecified year) - Must remove rear seats.

RAV4 (2005-2015) - Fits most pins.

RAV4 (2007) - Easily handles modern games including space for an appliance dolly, after folding down the rear seats. Haven't tried NIB. Very flat entry and mostly flat floor (except for a little bump where the seats fold) so easy to load and unload, even by yourself.

RAV4 (2013) - Fist most pins, including Gottlieb System 3.

RAV4 (2019 - 2025, 5th generation - not plug-in) - Fits a WPC, but with some issues. Be certain to load with the folded down head towards the back. The seats do not lie flat which makes sliding the pin difficult and raises the front towards the roof - although a few loads will compress the seats flatter. Try taking off any rubber protection on the back of the seat to increase headroom and add a thin smooth sheet of wood (Luan or similar) to make sliding in and out easier. If the game has a gun for the shooter, it can touch or come close to the driver's seat. Connect ratchet straps to brackets that hold the seats locked - front and back to keep the pin stable. It is unlikely to fit a Gottlieb System 4 with the head connected.

RAV4 (5th generation - plug-in) Plug-in models have less headroom making leaving the head on most games impossible.

RAV4 (2026 - 6th Generation) - No information available yet.

Sequoia (2008) - Fits pins no problem.

Sienna (2013) - will hold 2 pins with the middle seats removed. Both loaded from the back but the first pin is turned 90 degrees behind the front seats, second pin was loaded back box first. One pin will fit a 2004 with second row seats in place.

Tacoma Pre-Runner (Unspecified year) - fits great.

Venza (Unspecified year; possibly 2009 or 2010) - Back seat folded down. Tried to shoehorn a WMS Cyclone (System 11). Had to remove nuts from head side of hinge, and slide head forward approx. 3-4 inches on top of cabinet. Ground braid from cab to head had to be removed from stud in head. Very, very, very tight fit! Note: tallest measurement with head folded on Cyclone was 30". 

== Volkswagen ==

Atlas (2019-2023) - Will fit 1 machine without problems.

Golf TDi SportWagon (2015) - Will hold a machine; a bit too tight for a fold-down newer game though. Seats don't fold down flat, so there is a bit of a 'rise' on the folded seats. Have *not* tried the two '69' wedgies trick yet.

Jetta TDi SportWagon (2010-14) - Will hold a machine; a bit too tight for a fold-down newer game though. Seats fold down completely and lay flat. Can fit two wedgehead coffins on their sides in a '69' position. Then the two heads can barely fit on the passenger seat.

Passat Wagon (2005) - 30.5 inches of height. Will fit most machines, even DMD's. Dr Who & TZ fit no problem.

Sharan(Unspecified year) - Will fit 1 machine without problems.

Tiguan (2011) - Was able to fit a T2. It was fairly easy to get in but a bit tricky to remove.

Tiguan (2012) - Will NOT fit newer folded pins (about 1" too short), Early SS and EMs fit fine with the head removed, System 11 has also fit.

Toureg (Unspecified year) - Will hold machine, at least an early 70's version (like Bally Circus)

== Volvo ==

240DL Station Wagon (1984) - Almost any pin fits (except Hercules) with the head folded down.

User talk:Chibler

2025-07-08T20:41:07Z

The Hammer: /* CPU vs. MPU */

'''Chris Hibler '''

Resident of West St. Louis County, Missouri 
Personal Pinball Site: https://chrishiblerpinball.com/ 
YouTube Channel: www.youtube.com/@ChrisHiblerPinball

YouTube data as of 7/6/2025
Joined Apr 30, 2016
2.68K subscribers
1,354 videos
481,545 views

I've been repairing pins since my first acquisition in 1991 (Gottlieb Centigrade 37). My collection of 60 or so games is split between Gottlieb EMs and a mix of solid state games. 

Oldest game: 1962 Gottlieb Rack-A-Ball 
Newest game: 2014 Ironman VE 

Chris, blanking signal is actually a periodic signal I know you're in the process of editing, but it is an important distinction. Obviously it's high most of the time, but it dips low at least once every display interrupt (to clear the displays).

If only it worked as desired to prevent coil lockout (*sigh*)

-scott

Playground:

Using a SIMTEK STK12C68-SF45 in various manufacturer's boards
Board modifications:

Sega or Stern -- the HSB pin number 26 needs to be removed. 
Data East -- remove HSB pin number 26, and make a link between +5V and B+. 
Williams -- some games use larger RAM circuits. To be able to use this NVRAM, add resistor 1.5k on R93, and remove O ohms resistor on W3. 
https://pinside.com/pinball/forum/topic/nvram-adapters-16-free-shipping-not-mine

== Gottlieb image caption edit ==

Why did you revert the edit to the caption on the sys80 page? Was it in place for a particular reason that I may have missed? --[[User:ForceFlow|ForceFlow]] ([[User talk:ForceFlow|talk]]) 17:42, 9 November 2016 (CST)

I rolled that back because either Palson or I put that in there to add a bit of levity. I like to insert an "easter egg" from time to time to make the document more readable. I was going to list the reason when I rolled it back but the darned roll back feature doesn't allow that. It just rolls the change back.

[Chris Hibler, 11/9/16, 6:29pm CST]

It wasn't me. Not my voice at all. That has Hibler written all over it. I RARELY add commentary.

--[[User:Jimpal|Jimpal]] ([[User talk:Jimpal|talk]]) 06:20, 10 November 2016 (CST)

I understand technical stuff can sometimes get dry and boring to read, but honestly, to me, it sounded like the writer was calling the reader stupid for not noticing the jumper wire in the photo. Since it wasn't written in a professional way, it seemed prudent to address it. --[[User:ForceFlow|ForceFlow]] ([[User talk:ForceFlow|talk]]) 13:33, 10 November 2016 (CST)

== CPU vs. MPU ==

Chris, I saw that you changed post on the System 11 reset circuit from CPU to MPU.

I have always been curious about the difference. In pinball, I had always referenced the MPU in the early SS pins. But by WPC89, I had referenced the board as a CPU.

In Williams Sys 11, is it a MPU?

In the EE world, not necessarily relevant to our world, MPU is used completely differently:

"The MPU monitors transactions between the CPU and the memory and raises the alarm (triggers a fault exception) when an access violation is detected. "

https://www.eejournal.com/article/what-the-faq-are-cpus-mpus-mcus-and-gpus/

I don't care what is used. I was just wondering what the pinball world does and why.

BTW, the other editing you did was a distinct improvement. Thanks. [[User:The Hammer|The Hammer]] ([[User talk:The Hammer|talk]])

---7/6/25--- 
Response:
That change was made for consistency.
Throughout the Wiki, and in general, the processor board is the MPU.
The MPU contains a CPU, be it 6800,68B09E or whatever.
That's the only reason.

It's my old computer science background that makes this seem like the right nomenclature.

Thanks for the comments. I try to not change the intent of the writing but to "streamline" it into the same "look and feel". My old friend Jim Palson was a great foil/sounding board for this too. It's simply tragic that he lost his life at such an early age due to cancer.

Thanks for the help with the Wiki. Besides me, there aren't many authors providing content. I appreciate everyone who lends a hand.

User talk:Chibler

2025-07-08T20:40:02Z

The Hammer: /* CPU vs. MPU */

'''Chris Hibler '''

Resident of West St. Louis County, Missouri 
Personal Pinball Site: https://chrishiblerpinball.com/ 
YouTube Channel: www.youtube.com/@ChrisHiblerPinball

YouTube data as of 7/6/2025
Joined Apr 30, 2016
2.68K subscribers
1,354 videos
481,545 views

I've been repairing pins since my first acquisition in 1991 (Gottlieb Centigrade 37). My collection of 60 or so games is split between Gottlieb EMs and a mix of solid state games. 

Oldest game: 1962 Gottlieb Rack-A-Ball 
Newest game: 2014 Ironman VE 

Chris, blanking signal is actually a periodic signal I know you're in the process of editing, but it is an important distinction. Obviously it's high most of the time, but it dips low at least once every display interrupt (to clear the displays).

If only it worked as desired to prevent coil lockout (*sigh*)

-scott

Playground:

Using a SIMTEK STK12C68-SF45 in various manufacturer's boards
Board modifications:

Sega or Stern -- the HSB pin number 26 needs to be removed. 
Data East -- remove HSB pin number 26, and make a link between +5V and B+. 
Williams -- some games use larger RAM circuits. To be able to use this NVRAM, add resistor 1.5k on R93, and remove O ohms resistor on W3. 
https://pinside.com/pinball/forum/topic/nvram-adapters-16-free-shipping-not-mine

== Gottlieb image caption edit ==

Why did you revert the edit to the caption on the sys80 page? Was it in place for a particular reason that I may have missed? --[[User:ForceFlow|ForceFlow]] ([[User talk:ForceFlow|talk]]) 17:42, 9 November 2016 (CST)

I rolled that back because either Palson or I put that in there to add a bit of levity. I like to insert an "easter egg" from time to time to make the document more readable. I was going to list the reason when I rolled it back but the darned roll back feature doesn't allow that. It just rolls the change back.

[Chris Hibler, 11/9/16, 6:29pm CST]

It wasn't me. Not my voice at all. That has Hibler written all over it. I RARELY add commentary.

--[[User:Jimpal|Jimpal]] ([[User talk:Jimpal|talk]]) 06:20, 10 November 2016 (CST)

I understand technical stuff can sometimes get dry and boring to read, but honestly, to me, it sounded like the writer was calling the reader stupid for not noticing the jumper wire in the photo. Since it wasn't written in a professional way, it seemed prudent to address it. --[[User:ForceFlow|ForceFlow]] ([[User talk:ForceFlow|talk]]) 13:33, 10 November 2016 (CST)

== CPU vs. MPU ==

Chris, I saw that you changed post on the System 11 reset circuit from CPU to MPU.

I have always been curious about the difference. In pinball, I had always referenced the MPU in the early SS pins. But by WPC89, I had referenced the board as a CPU.

In Williams Sys 11, is it a MPU?

In the EE world, not necessarily relevant to our world, MPU is used completely differently:

"The MPU monitors transactions between the CPU and the memory and raises the alarm (triggers a fault exception) when an access violation is detected. "

https://www.eejournal.com/article/what-the-faq-are-cpus-mpus-mcus-and-gpus/

I don't care what is used. I was just wondering what the pinball world does and why.

BTW, the other editing you did was a distinct improvement. Thanks. --

---7/6/25--- 
Response:
That change was made for consistency.
Throughout the Wiki, and in general, the processor board is the MPU.
The MPU contains a CPU, be it 6800,68B09E or whatever.
That's the only reason.

It's my old computer science background that makes this seem like the right nomenclature.

Thanks for the comments. I try to not change the intent of the writing but to "streamline" it into the same "look and feel". My old friend Jim Palson was a great foil/sounding board for this too. It's simply tragic that he lost his life at such an early age due to cancer.

Thanks for the help with the Wiki. Besides me, there aren't many authors providing content. I appreciate everyone who lends a hand.

User talk:Chibler

2025-07-08T20:39:28Z

The Hammer: /* CPU vs. MPU */

'''Chris Hibler '''

Resident of West St. Louis County, Missouri 
Personal Pinball Site: https://chrishiblerpinball.com/ 
YouTube Channel: www.youtube.com/@ChrisHiblerPinball

YouTube data as of 7/6/2025
Joined Apr 30, 2016
2.68K subscribers
1,354 videos
481,545 views

I've been repairing pins since my first acquisition in 1991 (Gottlieb Centigrade 37). My collection of 60 or so games is split between Gottlieb EMs and a mix of solid state games. 

Oldest game: 1962 Gottlieb Rack-A-Ball 
Newest game: 2014 Ironman VE 

Chris, blanking signal is actually a periodic signal I know you're in the process of editing, but it is an important distinction. Obviously it's high most of the time, but it dips low at least once every display interrupt (to clear the displays).

If only it worked as desired to prevent coil lockout (*sigh*)

-scott

Playground:

Using a SIMTEK STK12C68-SF45 in various manufacturer's boards
Board modifications:

Sega or Stern -- the HSB pin number 26 needs to be removed. 
Data East -- remove HSB pin number 26, and make a link between +5V and B+. 
Williams -- some games use larger RAM circuits. To be able to use this NVRAM, add resistor 1.5k on R93, and remove O ohms resistor on W3. 
https://pinside.com/pinball/forum/topic/nvram-adapters-16-free-shipping-not-mine

== Gottlieb image caption edit ==

Why did you revert the edit to the caption on the sys80 page? Was it in place for a particular reason that I may have missed? --[[User:ForceFlow|ForceFlow]] ([[User talk:ForceFlow|talk]]) 17:42, 9 November 2016 (CST)

I rolled that back because either Palson or I put that in there to add a bit of levity. I like to insert an "easter egg" from time to time to make the document more readable. I was going to list the reason when I rolled it back but the darned roll back feature doesn't allow that. It just rolls the change back.

[Chris Hibler, 11/9/16, 6:29pm CST]

It wasn't me. Not my voice at all. That has Hibler written all over it. I RARELY add commentary.

--[[User:Jimpal|Jimpal]] ([[User talk:Jimpal|talk]]) 06:20, 10 November 2016 (CST)

I understand technical stuff can sometimes get dry and boring to read, but honestly, to me, it sounded like the writer was calling the reader stupid for not noticing the jumper wire in the photo. Since it wasn't written in a professional way, it seemed prudent to address it. --[[User:ForceFlow|ForceFlow]] ([[User talk:ForceFlow|talk]]) 13:33, 10 November 2016 (CST)

== CPU vs. MPU ==

Chris, I saw that you changed post on the System 11 reset circuit from CPU to MPU.

I have always been curious about the difference. In pinball, I had always referenced the MPU in the early SS pins. But by WPC89, I had referenced the board as a CPU.

In Williams Sys 11, is it a MPU?

In the EE world, not necessarily relevant to our world, MPU is used completely differently:

"The MPU monitors transactions between the CPU and the memory and raises the alarm (triggers a fault exception) when an access violation is detected. "

https://www.eejournal.com/article/what-the-faq-are-cpus-mpus-mcus-and-gpus/

I don't care what is used. I was just wondering what the pinball world does and why.

BTW, the other editing you did was a distinct improvement. Thanks. ~~

---7/6/25--- 
Response:
That change was made for consistency.
Throughout the Wiki, and in general, the processor board is the MPU.
The MPU contains a CPU, be it 6800,68B09E or whatever.
That's the only reason.

It's my old computer science background that makes this seem like the right nomenclature.

Thanks for the comments. I try to not change the intent of the writing but to "streamline" it into the same "look and feel". My old friend Jim Palson was a great foil/sounding board for this too. It's simply tragic that he lost his life at such an early age due to cancer.

Thanks for the help with the Wiki. Besides me, there aren't many authors providing content. I appreciate everyone who lends a hand.

User talk:Chibler

2025-07-06T16:35:57Z

The Hammer: /* CPU vs. MPU */ new section

'''Chris Hibler '''

Resident of West St. Louis County, Missouri 
Personal Pinball Site: http://webpages.charter.net/chibler/Pinball/index.htm 

I've been repairing pins since my first acquisition in 1991 (Gottlieb Centigrade 37). My collection of 60 or so games is split between Gottlieb EMs and a mix of solid state games. 

Oldest game: 1962 Gottlieb Rack-A-Ball 
Newest game: 1995 Williams Attack from Mars 

Order placed for Jersey Jack Pinball Wizard of Oz, scheduled for March 2012 delivery (finally delivered September 2014)

Chris, blanking signal is actually a periodic signal I know you're in the process of editing, but it is an important distinction. Obviously it's high most of the time, but it dips low at least once every display interrupt (to clear the displays).

If only it worked as desired to prevent coil lockout (*sigh*)

-scott

Playground:

Using a SIMTEK STK12C68-SF45 in various manufacturer's boards
Board modifications:

Sega or Stern -- the HSB pin number 26 needs to be removed. 
Data East -- remove HSB pin number 26, and make a link between +5V and B+. 
Williams -- some games use larger RAM circuits. To be able to use this NVRAM, add resistor 1.5k on R93, and remove O ohms resistor on W3. 
https://pinside.com/pinball/forum/topic/nvram-adapters-16-free-shipping-not-mine

== Gottlieb image caption edit ==

Why did you revert the edit to the caption on the sys80 page? Was it in place for a particular reason that I may have missed? --[[User:ForceFlow|ForceFlow]] ([[User talk:ForceFlow|talk]]) 17:42, 9 November 2016 (CST)

I rolled that back because either Palson or I put that in there to add a bit of levity. I like to insert an "easter egg" from time to time to make the document more readable. I was going to list the reason when I rolled it back but the darned roll back feature doesn't allow that. It just rolls the change back.

[Chris Hibler, 11/9/16, 6:29pm CST]

It wasn't me. Not my voice at all. That has Hibler written all over it. I RARELY add commentary.

--[[User:Jimpal|Jimpal]] ([[User talk:Jimpal|talk]]) 06:20, 10 November 2016 (CST)

I understand technical stuff can sometimes get dry and boring to read, but honestly, to me, it sounded like the writer was calling the reader stupid for not noticing the jumper wire in the photo. Since it wasn't written in a professional way, it seemed prudent to address it. --[[User:ForceFlow|ForceFlow]] ([[User talk:ForceFlow|talk]]) 13:33, 10 November 2016 (CST)

== CPU vs. MPU ==

Chris, I saw that you changed post on the System 11 reset circuit from CPU to MPU.

I have always been curious about the difference. In pinball, I had always referenced the MPU in the early SS pins. But by WPC89, I had referenced the board as a CPU.

In Williams Sys 11, is it a MPU?

In the EE world, not necessarily relevant to our world, MPU is used completely differently:

"The MPU monitors transactions between the CPU and the memory and raises the alarm (triggers a fault exception) when an access violation is detected. "

https://www.eejournal.com/article/what-the-faq-are-cpus-mpus-mcus-and-gpus/

I don't care what is used. I was just wondering what the pinball world does and why.

BTW, the other editing you did was a distinct improvement. Thanks.

Williams System 9 - 11

2025-07-01T14:38:35Z

The Hammer: /* Blanking Signal Stuck Low or Pulsing */

Click to go back to the [[Williams_Repair_Guides | Williams solid state repair guides index]].

==Introduction==

[[File:Wms sys9 boardset.jpg‎|300px|thumb|left|Williams System 9 Board Set from Space Shuttle]]
[[File:System11NothingBackbox.jpg|thumb|right|300px|Williams System 11 (nothing) Board Set from High Speed]]
[[File:WMS Sys11 Boardset.JPG|thumb|left|300px|Williams System 11A Board Set from Pinbot]]
[[File:WMS Jokerz Boardset.JPG|thumb|right|300px|Williams System 11b Board Set from Jokerz! (Note that power supply is a prototype)]]
[[File:WMS Sy11B Boardset.JPG|300px|thumb|left|System 11b Board Set from Transporter the Rescue]]
[[File:WMS_Sys11C_Boardset.JPG|thumb|right|300px|System 11c Board Set from Rollergames]] 
The Williams system 7 boardset was replaced in 1984 with the system 9 boardset, and then again in 1985 with the system 11 boardset. Combining the driver board, sound board, and cpu directly onto one board eliminated several design deficiencies of the earlier 3-7 boardsets; mainly the 40 pin interconnector, and extra wiring harness inter-board connectors. Larger ROMs could be fitted directly onto the boards allowing for more complex rulesets and sounds.
 

The System 9 and System 11 board sets are not 100% compatible. With a fair amount of effort, a System 11 board could be made compatible with a System 9, but it is not worth the extended effort to change the jumpers. It's far easier to just modify the rom images so that they are plug and play when installed in a System 11 CPU. You can find them already on the ipdb. The primary differences between the System 9 and System 11 board sets are the sound system and rom space.
(add more info later)

As time went on, the System 11 board set underwent some changes too. The power supply, sound board, and CPU / driver board have minor changes. More apparent was the addition of circuit boards. Starting with the 11a board set, a more complex sound board was added (System 11 sound boards are strictly background sounds only). Later in the System 11 series, sound functions were partially (11B) or fully removed (11C) from the MPU, and eventually were solely handled by a dedicated sound board. Game-specific interconnect boards and auxiliary power driver boards were introduced in System 11B games. The interconnect boards acted as a pass-through for switch, lamp, flasher, and solenoid signal lines and circuits. It also allowed circuits with different voltages to share the same power source by using current limiting resistors to drop voltages to the appropriate levels. All general illumination fuses were moved to this board. The auxiliary power driver board has the AC relay, which finally centralized the location of it. Likewise, several fuses, beefier TIP36C transistors, and bridge rectifiers are centralized on the auxiliary power driver board.

 

==Games==
===System 9===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Other Boards
!Transformer
!Notes
|-

|Strike Zone|| 1984 || 1916 || unknown || || || This is a shuffle alley which uses some pinball boards
|-
|Star Light|| 06-1984 || 530 || no speech || || 5610-09563-00 || only a few were made with System 9 boards inside
|-
|Space Shuttle|| 12-1984 || 535 || C-10716 (Speech only) || || 5610-09563-00 and 5610-10355-00 ||
|-
|Sorcerer|| 03-1985 || 532 || C-10716 (Speech only) || || 5610-09563-00 and 5610-10355-00 ||
|-
|Comet|| 06-1985 || 540 || C-10716 (Speech only) || || 5610-09563-00 and 5610-10355-00 ||
|}

===System 11===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Other Boards
!Transformer
!Notes
|-
|Alley Cats|| 10-1985 || 1918 || Unknown || || || This is a shuffle alley which uses some pinball boards
|-
|[[High Speed]]|| 01-1986 || 541 || C-11030 (Background sound only) || || 5610-10897-00 ||
|-
|Grand Lizard|| 04-1986 || 523 || C-11030 (Background sound only) || || 5610-10897-00 ||
|-
|Road Kings|| 07-1986 || 542 || D-11197-542 (Background music only) || || 5610-10897-00 ||
|}

===System 11A===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Other Boards
!Transformer
!Notes
|-
|Pinbot|| 10-1986 || 549 || D-11297-549 (Background Speech & Sound) || || 5610-10897-00 ||
|-
|Tic Tac Strike|| 11-1986 || 1919 || Unknown || || || This is a shuffle alley which uses some pinball boards
|-
|Millionaire|| 01-1987 || 555 || [[Media:WMS Sys11 Sound D-11298-555.JPG | D-11298-555]] (Background Speech & Sound) || || 5610-10897-00 ||
|-
|F-14 Tomcat|| 03-1987 || 554 || D-11298-554 (Used on 1st 5,000 games - Background Speech & Sound) / D-11581-554 || || 5610-12136-00 ||
|-
|Fire!|| 08-1987 || 556 || D-11581-556 || || 5610-12136-00 ||
|-
|Fire! Champagne Edition|| 09-1987 || 556 || D-11581-556 || || ||
|}

===System 11B===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Power Supply
!Aux Power Driver
!Master Interconnect
!Other Boards
!Transformer
!Notes
|-
|Big Guns|| 10-1987 || 557 || D-11581-557 || D-8345-557 || D-11583-557 || C-11762 || Uses D-11814 Flash Lamp Resistor Board || 5610-12136-00 ||Uses special solenoid switches
|-
|[[Space Station]]|| 12-1987 || 552 || D-11581-552 || D-8345-557 || D-11813-552 || C-11762-552 || Uses D-11814-552 Flash Lamp Resistor Board || 5610-12136-00 ||Uses special solenoid switches
|-
|Gold Mine|| 01-1988 || 1920 || None || D-8345-1914 || None || None || || || This is a shuffle alley which uses some pinball boards
|-
|Cyclone|| 02-1988 || 564 ||[[Media:WMS Sys11 Sound D-11581-564.JPG | D-11581-564]] || D-8345-557 || D-11813-574 || C-11762-564|| Uses D-11814-564 Flash Lamp Resistor Board || 5610-12136-00 ||Does not use special solenoid switches
|-
|Banzai Run|| 05-1988 || 566 || D-11581-566 || D-8345-566 ||D-12247-566 || D-12112 || || 5610-12136-00 ||Uses special solenoid switches
|-
|[[Swords of Fury]]|| 06-1988 || 559 || D-11581-559 || D-8345-557 || D-12247-559 || D-12313-559 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|Taxi|| 08-1988 || 553 || D-11581-553 || D-12246-553 || D-12247-559 || D-12313-553 || || 5610-12136-00 ||Uses special solenoid switches
|-
|Top Dawg|| 11-1988 || 1921 || None || D-12246 || None || D-12313-1921 || || || This is a shuffle alley which uses some pinball boards
|-
|Jokerz!|| 12-1988 || 567 || D-12338-567 || D-12246 || D-12247-559|| D-12313-567 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|[[Earthshaker]]|| 02-1989 || 568 || [[Media:System 11 Sound Board.JPG | D-11581-568]] || D-12246-568 || D-12247-559 || D-12313-568|| || 5610-12136-00 ||Does not use special solenoid switches
|-
|[[Black Knight 2000]]|| 04-1989 || 563 || [[Media:WMS Sys11 Sound D-11581-585.JPG | D-11581-585]] || D-12246 || D-12247-563 || D-12313-563|| || 5610-12136-00 ||Uses special solenoid switches
|-
|Transporter the Rescue|| 04-1989 || 2008 || D-11581-2008 || D-12246 || D-12247-2008|| D-12313-2008 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|Police Force|| 08-1989 || 573 || D-11581-573 || D-12246 || D-12247-566 || D-12313-573|| || 5610-12136-00 ||Does not use special solenoid switches
|-
|Shuffle Inn|| 10-1989 || 1922 || None (assumed) || D-12246 (assumed) || None || D-12313-1922 (assumed)|| || || This is a shuffle alley which uses some pinball boards
|-
|Elvira and the Party Monsters|| 10-1989 || 2011 || D-11581-2011 || D-12246 || D-12247-2011|| D-12313-2011 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|Bad Cats|| 11-1989 || 575 || D-11581-575 || D-12246 || D-12247-566 || D-12313-575|| || 5610-12136-00 ||Does not use special solenoid switches
|-
|Mousin' Around!|| 12-1989 || 2009 || D-11581-2009 || D-12246 ||D-12247-2009 || D-12313-2209 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|[[Whirlwind]]|| 01-1990 || 574 || D-11581-574 || D-12246 || D-12247-574 ||D-12313-574 || Uses a C-13287 Sound Overlay Solenoid Board to control 5 extra devices || 5610-12136-00 ||Does not use special solenoid switches
|}

===System 11C===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Master Interconnect
!Other Boards
!Transformer
!Notes
|-
|The Bally Game Show|| 04-1990 || 2003 || D-11581-2003 w/ 512K ROMS|| D-12313-2003 || Uses a C-13286 Sound Overlay Lamp Board || 5610-12136-00 || Does not use special solenoid switches
|-
|Pool Sharks|| 06-1990 || 2014 || D-11581-2014 w/ 512K ROMS|| D-12313-2014 || || 5610-12136-00 || Does not use special solenoid switches
|-
|[[Rollergames]]|| 06-1990 || 576 || D-11581-576 w/ 512K ROMS|| D-12313-576 || || 5610-12136-00 || Does not use special solenoid switches
|-
|Diner|| 09-1990 || 571 || D-11581-571 w/ 512K ROMS|| D-12313-571 || || 5610-12136-00 || Does not use special solenoid switches
|-
|Radical!|| 09-1990 || 2015 || D-11581-2015 w/ 512K ROMS|| D-12313-2015 || || 5610-12136-00 || Does not use special solenoid switches
|-
|Dr. Dude|| 11-1990 || 2016 || D-11581-2016 w/ 512K ROMS|| D-12313-2016 || || 5610-12136-00 || Does not use special solenoid switches
|-
|[[Riverboat Gambler]]|| 11-1990 || 50007 || D-11581-50007 w/ 512K ROMS (assumed) || D-12313-50007|| || 5610-12136-00 || Does not use special solenoid switches
|-
|Bugs Bunny's Birthday Ball|| 01-1991 || 20009 || D-11581-20009 w/ 512K ROMS|| D-12313-20009 || || 5610-12136-00 || Does not use special solenoid switches
|}

Game date of release and model numbers provided by the Internet Pinball Database - http://www.ipdb.org

==Recommended Documentation==
===Manuals & Schematics===
Schematics for each game are essential in tracing down connections to lamps, switches, and solenoids. The owner's game manual is a handy resource to have for general game operation, game settings & diagnostics, switch & lamp matrices, fuse lists, circuit boards and parts, playfield assemblies, some basic schematics, and wiring diagrams.

Be aware that although rare, some factory documentation contains errors in schematics, wiring, switch/lamp matrices, and solenoid assignments.

====Documentation Errors====
* Error on the [[High_Speed#MPU_Schematics_Error_for_U21_.26_U22|MPU I/O signals for U21 / U22 of High Speed]].
* [[#Flipper_Circuit_Schematics_Error|Flipper Circuit Schematics Error]] in the manuals for High Speed, Grand Lizard, and Road Kings.

===Theory of Operation & Schematics===
Details for board and cabinet schematics System 9-11 games can be found in the game manual or parts catalogs. Some copies can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball] or on [http://www.ipdb.org/ IPDB].

{| class="wikitable"
|-
!Manufacturer
!Guide
!Version
!Cover
!Source
!Games
!Notes

|-
|Williams
|Pinball Troubleshooting & Reference Manual
|69-8955 (April 21, 1986)
|[[file:placeholder.jpg|thumb|left|140px]]
|[[media:Williams-pinball-troubleshooting-reference-manual_16-8955_sys9.pdf|PDF]]
|Comet, High Speed, Sorcerer, Space Shuttle, Star Light
|System 9 games. Also includes Strike Zone shuffle alley game.

|}

===Schematics===
* [[media:Audio_schem_11581.pdf|D-11581 Sound Board]]

===Parts Catalogs===
Parts catalogs can also be useful, which include part numbers (helpful for purchasing parts online), exploded views of assemblies (helpful to see how the assemblies are put together), and board layouts & parts lists, and diagrams for controlled lamp, solenoid, and rubber locations. Parts catalogs also had supplementary updates to add and replace pages as newer games were released after the initial release of the catalogs.

Online copies of Bally & Williams parts catalogs can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball].

{| class="wikitable"
|-
!Manufacturer
!Catalog
!Version
!Cover
!Source
!Games
!Notes

|-
|Williams
|Blue Parts Catalog (1986-1989)
|16-9064-B
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/rvsk/ Viewer] [[media:Williams-parts-catalog-blue-book_16-9064-B.pdf|PDF]]
|Banzai Run, Big Guns, Black Knight 2000, Comet, Cyclone, Earthshaker!, F-14 Tomcat, Fire!, Grand Lizard, High Speed, Jokerz!, Millionaire, Pin Bot, Police Force, Road Kings, Sorcerer, Space Shuttle, Space Station, Swords of Fury, Taxi
|

|-
|Williams
|Red Parts Catalog (1989-1992)
|16-9190-B
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/feme/ Viewer] [[media:Williams-parts-catalog-red-book_16-9190-B.pdf|PDF]]
|Bad Cats, Diner, Dracula, Fish Tales, Funhouse, The Getaway, Hurricane, The Machine, Riverboat Gambler, Rollergames, Slugfest, Terminator 2, Whirlwind, White Water
|

|-
|Bally/Midway
|Yellow Parts Catalog (1988-1992)
|16-9147-B
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/itjk/ Viewer] [[media:Bally-midway-parts-catalog-yellow-book_16-9147-B.pdf|PDF]]
|Addams Family, Atlantis, Black Rose, Bugs Bunny, Dr. Dude, Dr. Who, Elvira, Game Show, Gilligan's Island, Harley Davidson, Mousin' Around, Party Zone, Pool Sharks, Radical!, Transporter, Truck Stop
|

|}

===Service Bulletins===
Supplementary service bulletin books were released, which included service bulletins that detailed any problems or issues with games that were discovered after they were released.

{| class="wikitable"
|-
!Manufacturer
!Version
!Cover
!Source
!Games
!Notes

|-
|Williams
|Service Bulletin Book, 1989
|[[file:Williams-Service-Bulletin-Book-1989-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1989.pdf|PDF]]
|Cyclone, Bonzai Run, Taxi, Earthshaker, Truck Stop, Transporter
|

|-
|Williams
|Service Bulletin Book, 1990
|[[file:Williams-1990-service-bulletin-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1990.pdf|PDF]]
|Diner, Police Force, Pool Sharks, Rollergames
|

|-
|Williams
|Service Bulletin Book, 1991
|[[file:Williams-1991-service-bulletin-book-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1991.pdf|PDF]]
|Dr. Dude, Jokerz, Riverboat Gambler
|This book includes some WPC games

|}

==Technical Info==
System 9 eliminated a huge issue with the earlier system 3 through 7 boardsets, the 40 pin interconnect between the MPU and Driver boards. All circuitry previously separated into MPU, driver, and sound boards was combined into a single MPU board. Satellite boards were still used for displays, speech, and solenoid expansion.

Starting with '''Big Guns''', Williams introduced another weak link into their system, the interconnect board. Initial implementations were used to disperse the general illumination between the playfield and backbox. The connectors on interconnect boards were prone to overheating and failure just like prior implementations. At the same time, flash lamp resistor boards were being used. These were created to collocate all of the flashlamp current limiting resistors, and eliminate under playfield flashlamp resistor boards, which had proven themselves problematic in the high heat, high vibration environment under the playfield. Resistors often desoldered themselves and/or vibrated so much that the connection fractured. Flash lamp resistor boards were only used on three games: Big Guns, Space Station, and Cyclone. In addition to the interconnect and the flash lamp resistor board, the auxiliary power driver board made its appearance. The auxiliary power driver board housed all of the high current transistors (TIP36c), solenoid and flasher fuses (including discrete flipper fuses), the AC select relay, and the solenoid power bridge rectifiers. The auxiliary power driver board did go through some minor changes, but it was functionally equivalent through the last System 11C game.

Starting with Banzai Run, a more standardized interconnect board was created. This interconnect board merged the general illumination interconnect with the flasher driver board. Switch and lamp circuits passed directly through this board as a matter of manufacturing convenience. Later interconnect boards added 3 opto couplers to indicate when the flippers and AC relay were activated (the same circuitry as used in the flipper power section of the WPC-089 -1 Power/Driver board).

One of the largest advantages of the system 11 board set is its ability to switch one set of coil driver transistors between 2 sets of coils/flashers. This is accomplished via a relay on a separate board called the A/C select relay (the A/C select relay was eventually moved to the auxiliary power driver board starting with Big Guns). The theory is that coils that are less frequently activated will be on the A side of the relay, and that flashers will be on the C side of the relay. Most of the time during gameplay, the C side is active, enabling the flashers. If the driver transistor for the A/C select relay itself shorts, the relay defaults to the coil side, allowing the game to continue to operate in a reasonable fashion (usually the A side coils are the ball shooter lane, drop target resets, VUK - basically coils that don't need to be able to operate 100% of the time unlike a slingshot coil or pop bumper coil). Data East's board set was essentially a copy of the system 11 board set, but Data East programmed it the opposite way, so that the flasher side of the A/C select relay is active by default. Data East games, when the A/C relay doesn't operate, just sits there and flashes lamps instead of playing.

System 9 and early System 11 games do share a disadvantage with the earlier 3-7 board sets, they still utilize special solenoid circuitry. The pops and slings on system 9/11 games do not activate via a switch which is seen by the MPU's program which fires the coil. Instead, the switches directly fire their associated coils via logic gates on the main board. The main disadvantage with this system is that the solenoids fire continuously as long as their activation switch is closed. A locked on sling or pop will burn out components quickly. It is recommended to add a 1, 1.5, or 2 amp inline fuse to each coil on a directly fired system 11 game. Usually just the pops and slings are direct fired coils. However, other coils were designated to the special solenoids.

Later System 11 games did not use the direct fire solenoid switches. Switches on the switch matrix were used instead. To easily identify games which do not use direct fire solenoid switches, IJ18 on the MPU board will not have a harness connection attached to it. Likewise, the slingshots and pop bumpers will no longer have a set of scoring switches.

One way that System 9 games differ from the previous 3-7 board set is that the special solenoids are not controlled by the CPU at all. In other words, the special solenoids are not pulsed during solenoid test, as the physical board architecture does allow for this.

The software in system 9-11 games continued with the same machine architecture from system 6 and 7, except for the special solenoids as mentioned above. More ram became available, up to 2k, but no game used over 800 bytes. This is likely due to the lower cost of 6264 RAM than 6116 RAM as was used in early System 9-11 games more than any other reason. Additional diagnostics in the form of switch error checking appeared in system 11. Any switch not activated over 30 games (16 games for flipper switches) would cause an error to be called out at power on. The software was able to compensate for broken switches by designating another switch to perform the same function as the broken switch. 

===MPU Driver Boards===
[[File:WMSSystem9MPU.jpg |300px|thumb|left|System 9 MPU]]
[[File:System9MPUFactoryMod.jpg |300px|thumb|right|These high frequency filter capacitors were added at the factory, and are normal. Their purpose is the snub high frequency noise in the Advance and Auto Up/Down coin door button circuits.]] 
'''System 9 MPU'''
Williams used a single version of the System 9 MPU in all System 9 games. A few minor modifications to the board may have been made, but it's essentially the same board for the entire 3 game run of Space Shuttle, Sorcerer, and Comet. The picture at left shows an early board that featured two inductors (copper wound coils that "smooth" DC power) at L1 and L2, adjacent to connector 1J17. Later revisions of the board used "zero ohm" jumpers instead, presumably to reduce cost.
 

[[File:WilliamsSystem10MPUFront.jpg ‎|300px|thumb|left|Williams System 10 MPU component side. Image courtesy of Brian Johnson.]]
[[File:WilliamsSystem10MPUBack.jpg ‎|300px|thumb|right|Williams System 10 MPU solder side. Image courtesy of Brian Johnson.]] 
Williams released a single game using an MPU board designated '''System 10'''. The game "4-in-1" ([https://www.ipdb.org/search.pl?any=4-in-1&sortby=name&search=Search+Database&searchtype=quick IPDB link]) was released in 1985 and is more like Pachinko than pinball.

From the Internet Pinball Database:

"This game is known in Williams documentation as "4-IN-1" but that name never appears on the game itself. A total of 100 games were produced. Each came with four interchangeable playfield overlays for the themes of Baseball, Poker, Football, and Soccer. The operator could change the overlay and Instruction Card, re-option switches, and have a new game in the same cabinet."
 

'''System 11''' games used one of four different revisions of the System 11 MPU. The first version of the System 11 MPU was completely self-contained, able to make game sounds on the board. A simple background sound board was used to add some game sounds. Between the baseline revision of the System 11 MPU and the last revision of the MPU (System 11C) incrementally more of the sound processing and sound circuitry was removed from the board (not stuffed). None of the System 11 shuffle alley games use a separate sound board.

[[File:WilliamsSystem11CPU.jpg|300px|thumb|left|Early System 11 (nothing) MPU]]
[[File:System11NothingLater.jpg|300px|thumb|right|Later System 11 (nothing) MPU. Note extensive alkaline corrosion abatement, NVRAM install, and use of modern reset generator. Image courtesy of Chris Hibler]] 
'''System 11 (nothing) MPU''' 
This picture shows the early System 11 MPU. A later revision of this MPU, pictured at right, has an additional jumper W16 located between the 7 segment diagnostic display and the relay, and a 4.7K ohm resistor between the 7447 and the resistor DIP. The early PCB on the left has a trace routing error to the sound ribbon cable connector. If you use it with a later system 11A sound card you will get no sound because the sound card doesn't get reset properly. If you wonder why your High Speed doesn't beep when turning it on this one is also the culprit.
 

[[File:System11ZenerDiodeAddition.jpg|300px|thumb|left|6.2V Zener Diodes added to the back of the System 11 (nothing) MPU. These zeners were added to the layout of the PCB in subsequent revisions of the board (11A, etc).]]
[[File:WMSSystem11Zener1N5234.jpg|300px|thumb|right|6.2V Zener Diodes (ZR3-ZR8) incorporated into the board layout and stuffed at the factory on a later board revision. Note: in this image, ZR7 and ZR8 have been replaced]] 
The picture at left shows six 6.2V zener diodes added to the solder side of a System 11 (nothing) MPU. These zeners were left off the factory silkscreen of the board. Later revisions of the System 11 MPU added them to the component side of the board. Their purpose is to protect the special solenoid switch inputs. Either a ZPY6,2/ZD6,2/1N4735A (1 watt) or ZF5,2/1N5234B (1/2 watt) can be used. This mod is purely optional. In reality the diode doesn't help much if you short the switch input with the solenoid voltage. In this case the diode and the 7402 are usually damaged and need to be replaced.
 
Additionally, if the System 11 (nothing) MPU is used in a System 11A game or later, pins 6 and 7 of the adjacent connector (J18) must be tied to the ground plane at the edge of the board. These pins provide the ground for the special solenoids. Without the modification they do not work. Some early System 11A pins might not need the mod. If unsure just check if a cable is connected to pin 6 or 7 in your game.
 

[[File:CPUWilliamsSystem11A-PB.jpg|300px|thumb|left|A rare prototype System 11a MPU]]
[[File:System11aTransitionVersion.jpg|300px|thumb|right|Blanking, 5VDC, and Diagnostic LEDs factory installed in a "transition" vintage System 11a MPU. The prior version 7447 (U48) and resistor DIP (U47) has been replaced with a 7407, discrete resistors and LEDs.]]
[[File:System11TransitionTag.jpg|300px|thumb|left|A prototype System 11a MPU with original label]] 
'''System 11a ''Prototype'' MPU''' 
This MPU was only used in Pin Bot. It's actually a System 11 (nothing) MPU PCB layout, with the 7 segment LED display replaced at the factory with 3 LEDs as used in all later System 11 MPUs (11A/B/C). The latest trace revision of this board also has the ground mod (connect 1J18, pins 6 and 7 to board ground) allowing it to work in any 11A/B/C game without modification. According to a friend it was referred to by the name of 11a instead of 11A by distributors.
 

[[File:CPUWilliamsSystem11A.jpg|300px|thumb|left|A late production System 11A MPU.]] 
'''System 11A MPU''' 
The System 11A MPU can be used in all System 11 games. If used in one of the four first System 11 games (Alley Cats, High Speed, Grand Lizard, and Road Kings), connector 1J15 and possibly the amplifier section must be stuffed. System 11A, 11B, and 11C games don't use the amplifier section of the MPU board. Sound amplification is accomplished on the sound board. On early production system 11A boards, the amplifier section was fully stuffed, just like the original System 11 board. Later in the production of System 11A boards, the amplifier section was not stuffed, just like an 11B board. But unlike System 11B boards, the System 11A board still has the same switch section layout as the original System 11 MPU, making it easy to identify.

'''Note:''' the sound mixing section of the System 11A MPU is stuffed with different resistor and capacitor values than that of the System 11B MPU. This may cause some sound quality differences as has been noted with EarthShaker.
 

[[File:System 11 CPU Driver Board.JPG|300px|thumb|left|System 11B MPU. Note that a large portion of the sound circuitry, including the TDA2002 amp, was not stuffed in late System 11A boards or any System 11B MPU boards.]] 
'''System 11B MPU''' 
The System 11B MPU can be used in all System 11 games too. If used in one of the four first System 11 games (Alley Cats, High Speed, Grand Lizard, and Road Kings), connector 1J15 and all of the sound amplification components must be added to the board. System 11A, 11B, and 11C games don't use the amplifier section of the MPU board. Sound amplification is accomplished on the sound board.

'''Note:''' the sound mixing section of the System 11A MPU is stuffed with different resistor and capacitor values than that of the System 11B MPU. This may cause some sound quality differences as has been noted with EarthShaker.
 

[[File:CPUWilliamsSystem11C.jpg|300px|thumb|left|System 11C MPU. Note that none of the sound circuitry, including the 6802 processor and 6821 PIA, is stuffed in System 11C MPU boards. All sounds were generated by the sound board.]] 
'''System 11C MPU''' 
The System 11C MPU can be used only in System 11C games since none of the sound processing circuitry was stuffed. It can be used in games prior to 11C, if the sound section is populated. However, some of the components needed are rare and / or costly, and there are a fair amount to install. If there is no other choice but to use this board, it is possible.
 

[[File:RottenDogMPU9211.jpg|300px|thumb|left|The RottenDog "System 9211" Aftermarket MPU]]
[[File:RottenDogMPU004.jpg ‎|300px|thumb|right|The RottenDog "MPU004" Aftermarket MPU with sound section overlay]] 
'''RottenDog MPU9211 and MPU004 Aftermarket MPUs''' 
The RottenDog aftermarket MPU9211 (shown at left) was designed to support all Williams System 9 - 11 games. How well the board works across that great breadth of games is somewhat questionable.

The CVSD used on this board is a CMX639D4 produced by CML Microcircuits. It replaces the 55516 (or 55536) CVSD used at U3 on original System 9 - 11 MPU boards.

The RottenDog aftermarket MPU004 (shown at right) was an earlier design thought to support all Data East and System 11 games. Again, how well the board accomplishes this for Williams games is questionable. A significant source of confusion on this board (like all RottenDog boards with DIP switches) is that the DIP switches are labeled opposite of traditional labeling. That is, set all switches to OFF for Williams games, ON for Data East games.
 
[[File:RDWilliams9211LaterRev.jpg |300px|thumb|left|The RottenDog "System 9211" Aftermarket MPU, later revision]] 
A later revision of the RottenDog 9211 MPU included a second trim POT to adjust the balance between 1408 DAC sounds and 55536 CVSD sounds.
 
====Lamp Matrix====
[[File:WMS Sys9 Lamp Column.jpg|300px|left|thumb|Picture of the lamp column portion of the lamp matrix of a System 9 MPU board. Note that the TIP42 drive transistors were removed from this board.]] 
The lamp matrix is made up of two parts - the lamp columns (drives) and lamp rows (returns). In most cases, the lamp row consists of eight 2N5060 over-current shunt SCR's and eight TIP122 drive transistors, while the lamp column consists of eight 2N6427 predrive transistors (WMS sometimes used MPS-A14 instead) and eight TIP42 or TIP42C transistors. However, there are some instances, as shown in the pic to the left, where the predrive transistors for the lamp columns are 2N6548s. It is unknown why Williams chose to use these transistors on occasion.

The over-current shunt circuit on the lamp row (returns) works by sensing the voltage drop across the 0.4 ohm, 3 Watt resistor on emitter of the TIP122 driver transistor. If a short circuit is present in the lamp row, the short circuit current will result in a higher than normal voltage drop across the emitter resistor. This voltage will trigger the gate of the 2N5060 SCR, causing it to turn on and shunt the base drive to the TIP122 transistor. This will turn off the driver transistor and prevent damage due to excessive current. Note that an RC circuit consisting of a 0.1uF capacitor and 1K ohm resistor is present on the gate of the SCR. This prevents a false trigger of the over-current shunt circuit due to an initial peak current from cold lamp filaments.
 

====Switch Matrix====
=====System 9 Switch Matrix Explained=====
[[Image:System9SwitchMatrix.jpg|300px|thumb|left|The System 9 Switch Matrix circuitry, as found in the Sorcerer manual.]]
General Description

At regular intervals, say 1 every msec or so, the 6808 microprocessor scans the switch matrix. This is done by pulling one switch column to ground, then sensing the switch row return state. Each row on which ground is detected means that the switch at the intersection of the column grounded and the detected row ground, is closed.

Hardware Detail

The 6808 writes the column data to the address location occupied by the 6821 at U15 on the board. This causes the 6821 output registers (PB0 – PB7) to propagate the data to a 74LS244 octal buffer at U45. The 74LS244 mirrors that same data at it's output pins. The data pattern on these output pins will have all bits set to logic “1” except one bit, which will be set to logic zero, or electrical ground. The ground is applied to the base of a 2N3904 transistor (which had been held high by a 4.7K SIP pull-up resistor SR8) where the ground is applied to the switch column (called switch matrix drives on the schematic). 

Closed switches connected to that column will then cause the normally high (via yet another pull up resistor, SR16) gate at a 74LS08 quad NAND gate (U51 and U52) to be pulled to ground. This NAND gate enables the circuitry to detect a switch closure returned via either connector 1J9 or 1J10.

The 6808 then “reads” the row returns by reading from the address space occupied by the same 6821 at U15 used to pulse the column strobes earlier. This time it reads 6821 registers PA0 – PA7.

Again, the processor knows which column it drew to ground, and it knows which rows were caused to be pulled to ground via closed switches attached to the column. From this information, the closed switches can be identified. Genius. Bania: “I'm tellin' ya Jerry, this switch matrix stuff is gold Jerry, it's gold!”.

The switch diode isolates the switch in the matrix. Without this isolation diode, multiple simultaneous switch closures will cause false returns and confuse the processor. A switch diode that is open will always prevent a switch from registering, in the same way that a broken wire or failed open switch would.
 

====Jumper Settings and Locations for System 9 & 11 MPU Boards====

Below are charts of the jumpers on System 9 & 11 boards. Rather than listing the boards by their platform (System 11A/B/C), each chart is listed by the numbers stenciled on the circuit boards.
 

'''5764-10749-00 REV. C (System 9)'''

Typically installed jumpers are W2, W5, W6, W7, W9, & W12.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1 / W2|| Below U12 || Microprocessor Internal RAM Enable. W1 IN, W2 OUT when using 6802, reverse when using 6808 || U12 RAM can be removed with 6802 and W1 installed.
|-
|W3|| || ||
|-
|W4|| || ||
|-
|W5|| Left of U49 || Country jumper. Remove for German factory settings, add for US factory settings ||
|-
|W6|| Below U5 || Along with W7, used to send +12V to opto rows || Typically installed, but not used
|-
|W7|| Below U5 || Along with W6, used to send +12V to opto rows || Typically installed, but not used
|-
|W8|| Below connector IJ9 || Ties resistor network SR15 to +12v ||
|-
|W9|| Below connector IJ9 || Ties resistor network SR15 to +5v ||
|-
|W10|| Below U50 || Installed - sounds from CPU board can be played without speech board attached || Typically not installed, except Strike Zone
|-
|W11|| Below U37 || Used when U19 game ROM 2 is used ||
|-
|W12|| Below U36 || Used to increase U20 game ROM 1 size from 2764 to 27128 ||
|-
|}
 

'''5764-10881-00 REV. - (Typically System 11)'''

Typically installed jumpers are W1, W2, W4, W5, & W7.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1|| Below U15 CPU chip || Ties crystal to clock input (pin 39) of U15 CPU ||
|-
|W2 / W3|| To the right of U25 RAM chip || Used to increase the ROM size ||
|-
|W4|| Below U31 (to the right of U25) || Used to increase the ROM size ||
|-
|W5|| Below U39 & U38 (PIA chip) || Used to apply +5v to SR14 resistor network ||
|-
|W6|| Below U30 & U27 || Used to apply +12v to SR14 resistor network ||
|-
|W7|| Below U48 || Country jumper. Remove for German text and settings, add for English text and settings ||
|-
|DS1|| Left of U13 || || Marked as DS1 on board (lower of 2 jumpers) - leave out
|-
|DS1|| Left of U13 || || Marked as DS1 on board (upper of 2 jumpers) - leave out
|-
|DS2|| Left of U13 || || Marked as DS2 on board (lower of 2 jumpers) - keep installed
|-
|DS2|| Left of U13 || || Marked as DS2 on board (upper of 2 jumpers) - keep installed
|-
|}
 

'''5764-10881-00 REV. B (Typically System 11 - Referred to as Prototype System 11a in text above)'''

Typically installed jumpers are W1, W2, W4, W5, W7, W8, W11, W12, W13, W14, W16, W17 & W18.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1|| Below U15 CPU chip || Ties crystal to clock input (pin 39) of U15 CPU ||
|-
|W2 / W3|| To the right of U25 RAM chip || Used to increase the ROM size ||
|-
|W4|| Below U31 (to the right of U25) || Used to increase the ROM size ||
|-
|W5|| Below U39 & U38 (PIA chip) || Used to apply +5v to SR14 resistor network ||
|-
|W6|| Below U30 & U27 || Used to apply +12v to SR14 resistor network ||
|-
|W7|| Below diagnostic LEDs || Country jumper. Remove for German text and settings, add for English text and settings ||
|-
|W8 / W9|| Below U24 (sound CPU chip) || Used to choose what to use as /RST for U24 sound CPU ||
|-
|W10 / W11|| To the right of 3 radial caps in reset section|| Choice of +18v (W10) or +12v (W11) for sound amplifier ||
|-
|W12|| A resistor below U10 PIA || Pull down resistor for E1 (pin 1) and E2 (pin 19) of U11 & U13 address line buffer chips ||
|-
|W13|| A resistor below U16 data line buffer chip || Pull down resistor for /E (pin 19) of U16 data line buffer chip ||
|-
|W14 / W15|| Below U29 || 1ms IRQ signal (W14 in) or 2ms IRQ signal (W15 in) ||
|-
|W16|| Below U27 || Blanking signal to input "D" of U48 LED decoder chip || not present on first pcb revision
|-
|DS1|| Left of U13 || || Marked as DS1 on board (lower of 2 jumpers) - leave out
|-
|DS1|| Left of U13 || || Marked as DS1 on board (upper of 2 jumpers) - leave out
|-
|DS2|| Left of U13 || || Marked as DS2 on board (lower of 2 jumpers) - keep installed
|-
|DS2|| Left of U13 || || Marked as DS2 on board (upper of 2 jumpers) - keep installed
|-
|}

 

'''5764-12091-00 REV. - (Typically System 11A)'''

Typically installed jumpers are W1, W2, W4, W5, W7, W8, W11, W12, W13, W14, W16, W17 & W18.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1|| Below U15 CPU chip || Ties crystal to clock input (pin 39) of U15 CPU ||
|-
|W2 / W3|| To the right of U25 RAM chip || Used to increase the ROM size ||
|-
|W4|| Below U31 (to the right of U25) || Used to increase the ROM size ||
|-
|W5|| Below U39 & U38 (PIA chip) || Used to apply +5v to SR14 resistor network ||
|-
|W6|| Below U30 & U27 || Used to apply +12v to SR14 resistor network ||
|-
|W7|| Below diagnostic LEDs || Country jumper. Remove for German text and settings, add for English text and settings ||
|-
|W8 / W9|| Below U24 (sound CPU chip) || Used to choose what to use as /RST for U24 sound CPU ||
|-
|W10 / W11|| To the right of 3 radial caps in reset section|| Choice of +18v (W10) or +12v (W11) for sound amplifier ||
|-
|W12|| A resistor below U10 PIA || Pull down resistor for E1 (pin 1) and E2 (pin 19) of U11 & U13 address line buffer chips ||
|-
|W13|| A resistor below U16 data line buffer chip || Pull down resistor for /E (pin 19) of U16 data line buffer chip ||
|-
|W14 / W15|| Below U29 || 1ms IRQ signal (W14 in) or 2ms IRQ signal (W15 in) ||
|-
|W16|| Below U27 || Ties XTAL (pin 38) of U15 CPU chip to ground || Only cut when using Hitachi 6808 or 6802 MPU at U15
|-
|W17|| Below U23 || Ties XTAL (pin 38) of U24 sound CPU chip to ground || Only cut when using Hitachi 6808 or 6802 MPU at U24
|-
|DS1|| Left of U13 || || Marked as DS1 on board (lower of 2 jumpers) - leave out
|-
|DS1|| Left of U13 || || Marked as DS1 on board (upper of 2 jumpers) - leave out
|-
|DS2|| Left of U13 || || Marked as DS2 on board (lower of 2 jumpers) - keep installed
|-
|DS2|| Left of U13 || || Marked as DS2 on board (upper of 2 jumpers) - keep installed
|-
|}

 

'''5764-12206-00 REV. A (Typically System 11B & 11C)'''

Typically installed jumpers are W1, W2, W4, W5, W7, W8, W11, W14, W16, W17 & W19.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1|| Below U15 CPU chip || Ties crystal to clock input (pin 39) of U15 CPU ||
|-
|W2 / W3|| To the right of U25 RAM chip || Used to increase the ROM size ||
|-
|W4|| Below U31 (to the right of U25) || Used to increase the ROM size ||
|-
|W5 || Above U25 RAM chip || Used with 2K x 8 6116 RAM at U25 ||
|-
|W6 || Above U25 RAM chip || Used with 8K x 8 6264 RAM at U25 || only 2K will be used from the factory
|-
|W7|| Below diagnostic LEDs || Remove for German text, add for English text || This jumper is not used in games with 16 digit score displays. Instead, install the U26 and U27 EPROMs for country and game.
|-
|W8 / W9|| Below U24 (sound CPU chip) || Used to choose what to use as /RST for U24 sound CPU ||
|-
|W10 / W11|| To the right of 3 radial caps in reset section|| Choice of +18v (W10) or +12v (W11) for sound amplifier ||
|-
|W12|| A resistor below U10 PIA || Pull down resistor for E1 (pin 1) and E2 (pin 19) of U11 & U13 address line buffer chips ||
|-
|W13|| A resistor below U16 data line buffer chip || Pull down resistor for /E (pin 19) of U16 data line buffer chip ||
|-
|W14 / W15|| Below U29 || 1ms IRQ signal (W14 in) or 2ms IRQ signal (W15 in) ||
|-
|W16|| Below U27 || Ties XTAL (pin 38) of U15 CPU chip to ground || Only cut when using Hitachi 6808 or 6802 MPU at U15
|-
|W17|| To the left of U24|| Ties XTAL (pin 38) of U24 sound CPU chip to ground || Only cut when using Hitachi 6808 or 6802 MPU at U24
|-
|W18 || Below U23 || Used with 8K x 8 6264 RAM at U23 || only 2K will be used.
|-
|W19 || Below U23 || Used with 2K x 8 6116 RAM at U23 ||
|-
|DS1|| Left of U13 || || Marked as DS1 on board (lower of 2 jumpers) - leave out
|-
|DS1|| Left of U13 || || Marked as DS1 on board (upper of 2 jumpers) - leave out
|-
|DS2|| Left of U13 || || Marked as DS2 on board (lower of 2 jumpers) - keep installed up to 11B
|-
|DS2|| Left of U13 || || Marked as DS2 on board (upper of 2 jumpers) - keep installed up to 11B
|-
|}
 

====Combining the System 9 Sound ROM Images====
Pinside user, "Dumbass", has created replacement System 9 MPU boards. One of the new things that he implemented in the board design is a daughterboard that can be mounted to the main MPU, which handles the speech duties. Therefore, the speech board with its sometimes problematic ribbon cable no longer has to be used. However, the sound and speech chip code now has to be combined together on a 27256 PROM, which is used at position U49.

The DOS/Windows "copy" commands to accomplish this for the System 9 games, are shown below (space formatting added for clarity).
The file [https://www.pinwiki.com/wiki/index.php/File:Pad.zip pad.732] is a special file and is not part of the released ROM images. It is a 4K (4096 Bytes) binary file filled with 0xff. Create it using your favorite hex editor, or download the file here: [[File:Pad.zip]]. Below is how the code should be concatenated for it to work properly. It is very similar to what is done for the System 9 code to be modified for a System 11 MPU.

Space Shuttle 
Checksum = 0000h


copy /b pad.732     + spch_u5.732 + spch_u6.732 + spch_u4.732 + cpu_u49.128 = cpu_u49.256 



Sorcerer 
Checksum = E67Fh


copy /b spch_u7.732 + spch_u5.732 + spch_u6.732 + spch_u4.732 + cpu_u49.128 = cpu_u49.256 



Comet 
Checksum = F9CCh


copy /b spch_u7.732 + spch_u5.732 + spch_u6.732 + spch_u4.732 + cpu_u49.128 = cpu_u49.256 

 

====Converting the System 9 ROM Images to work in a System 11 MPU====
It is easy to create System 11 compatible ROM images from System 9 ROMs. 
The DOS/Windows "copy" commands to accomplish this for the System 9 games, are shown below (space formatting added for clarity).

The file [https://www.pinwiki.com/wiki/index.php/File:Pad.zip pad.732] is a special file and is not part of the released ROM images. It is a 4K (4096 Bytes) binary file filled with 0xff. Create it using your favorite hex editor, or download the file here: [[file:Pad.zip]].

The System 11 CPU works out of the box with a 27128 EPROM at location U27. You may choose to double the ROM image, creating a 27256 image so that its size is consistent with the other System 11 U27 ROMs.

Remove jumper W8 and install jumper W9 on the System 11 CPU to enable sound to work properly. System 11 controls the sound reset via software.
 

=====Space Shuttle=====

copy cpu_u49.128 cpu_u21.128 
copy /b pad.732     + spch_u5.732 + spch_u6.732 + spch_u4.732 cpu_u22.128 
copy /b cpu_u20.128 + cpu_u20.128 cpu_u27.256 <=== This command doubles the 128K image into a 256K image

 

=====Sorcerer=====

copy cpu_u49.128 cpu_u21.128 
copy /b cpu_u21.128 + cpu_u21.128 cpu_u21.256 
copy /b spch_u7.732 + spch_u5.732 + spch_u6.732 + spch_u4.732 cpu_u22.128 
copy /b cpu_u22.128 + cpu_u22.128 cpu_u22.256 
copy /b pad.732     + cpu_u19.732 + cpu_u20.764 cpu_u20.128 
copy /b cpu_u20.128 + cpu_u20.128 cpu_u27.256 
copy /b pad.732     + cpu_u19.l2.bin + cpu_u20.l2.bin cpu_u20.l2.128 
copy /b cpu_u20.l2.128 + cpu_u20.l2.128 cpu_u27.l2.256 <=== This command doubles the 128K image into a 256K image 

Sorcerer is the only System 9 pinball game using 2 ROMs which make things complicated for repair. You can use the cpu_u20.128 image in a system 9 CPU jumpered for Space Shuttle or Comet. If you install W12 and remove W11 the CPU will be jumpered for a 27128 EPROM.
 

=====Comet=====

copy cpu_u49.128 cpu_u21.128 
copy /b spch_u7.732 + spch_u5.732 + spch_u6.732 + spch_u4.732 cpu_u22.128 
copy /b cpu_u20.128 + cpu_u20.128 cpu_u27.256 /b <=== This command doubles the 128K image into a 256K image 

 

===Sound Boards===

[[File:WMS Sys9 Speech 2532.JPG|300px|thumb|left|System 9 Speech Board Using 2532 PROMs (from Space Shuttle)]]
[[File:WMS Sys9 Speech Board.JPG|300px|thumb|right|System 9 Speech Board Using 2732 PROMs (from Comet)]] 
The speech board used in the three System 9 games, Space Shuttle, Sorcerer and Comet is essentially the same as the speech board used in System 6/7 games. However the speech board was enhanced during the Space Shuttle run. Four jumpers were added to accomodate either 2532 or 2732 EPROMs. When burning EPROMs, make certain which style of ROM is used. 

[[File:WMS Sys9 Speech Early Later.JPG|300px|thumb|left|System 9 Speech Board - Left unit is from early Space Shuttle, right is from later Space Shuttle]] 
Only the early Space Shuttles use 2532 EPROMs from the factory. Later Shuttles, Sorcerer and Comet use 2732 EPROMs. The later speech board is backward compatible. If using such a board, either 2532s or 2732s can be used for the first two System 9 games (or System 6/7 games), provided that the jumpers are set for the appropriate EPROM. 

In addition to the speech board generating speech sounds, it mixes the sound and speech signals via the potentiometer on the speech board.
 

[[Image:WilliamsSystem11BackgroundSoundBoard.jpg|500px|thumb|left|Background Sound board as found in High Speed]]
[[File:WMS D-11197 Road Kings Sound.JPG|500px|thumb|right|D-11197 Background Sound board as found in Road Kings]]
[[Image:WilliamsD-11297BackGroundSoundBoard.jpg|500px|thumb|left|D-11297 Sound board as found in Pinbot, fully populated]]
[[File:WMS D-11298 Pinbot Sound.JPG|500px|thumb|right|D-11298 Sound board as found in Pinbot. This version only has U4 populated (U19 is not). Uncertain why U19 is needed. Note that the CVSD "lane" of the board is not stuffed.]]
 
[[Image:System_11_Sound_Board.JPG|500px|thumb|left|D-11581 Sound board, not completely populated]]
[[Image:D-11581-F14.jpg ‎|500px|thumb|right|D-11581 Sound board, completely populated]]
[[Image:System11CSoundBoard.jpg|500px|thumb|left|D-11581 Sound Board, Completely Populated, with W10/W11 Jumpers. W10/W11 enable use of 512K sound ROMs as found in all System 11C games like Game Show, Dr. Dude, Pool Sharks, Rollergames, Diner, Radical, and Bugs Bunny]]
 
[[File:WMS D-12238 Jokerz Sound.jpg|500px|thumb|left|D-12238 Sound Board - specific to Jokerz! only]]
[[File:JokerzSoundBoardPinOut.png|700px|thumb|right|D-12238 Sound Board - specific to Jokerz! only - Connector PinOut]]
 
[[File:D11581SchematicIcon.jpg|300px|thumb|left|Use hyperlink at right to open D-11581 sound board schematics]]
[[File:D11581PartsDelta.jpg ‎|300px|thumb|right|Parts missing from partially populated D-11581 sound boards]] 
'''Link to:''' [[media:Audio_schem_11581.pdf|Schematics for the D-11581 sound board]]. 
'''Note:''' The parts shown at right represent the delta from a partially populated D-11581 to a fully populated D-11581. *The value of R13 will vary between 4.9Kohms (or 4.99Kohms) and 10Kohms. If R14 and R15 are 10Kohms, then R13 should be 4.9Kohms (or 4.99Kohms). If R14 and R15 are 20Kohms, then R13 should be 10Kohms.
 

===Power Supply===
[[Image:WMSSystem11PSPreBigGuns.jpg|300px|thumb|left|Pre-Taxi Power/Regulator Board. This power supply has had the header pins replaced and the 5V filter cap at C10 replaced. Note that this board has the 20A fuse for the GI still installed. This indicates that it is an early System 7 board. The fuse and it's holder should be replaced by a wire in all System 9 and 11 games]]
[[File:WMS_PS_5765-09466-01_rev_B.JPG|300px|thumb|right|WMS Power Supply - Revision B (Pinbot) Note that the top fuse holder just below the large 15000uF capacitor is broken on the left side]] 

These power supplies use obsolete parts at Q1 (SDS-201) and Q3 (SDS-202). The PCB print was used from Black Knight through Swords of Fury, with slight modifications. Up until and including Fire!, Q1 and Q3 were the obsolete SDS-201 and SDS-202. Starting with some Fire!, the board uses an MJE15030 at Q1 and an MJE15031 at Q3.

Part numbers printed on an SDS-201 at Q1 may be "6557" or "9057S".
Part numbers printed on an SDS-202 at Q3 may be "MDS60" or "9058S"
 

[[File:EarlyWMSPowerSupplyTraceRoutingErrorCloseUpAnnotated.jpg|300px|thumb|left|A closeup of the corrected trace routing error on a Fire! power supply board.]]
[[File:System11PSSchematic.jpg|300px|thumb|right|WMS Power Supply (High Speed) Schematics.]] 
There was a trace routing error on the original Fire! power supply pcbs. WMS cut the trace and used a jumper to correct the error. This error was corrected in the PCB layout at the start of "Big Guns" game production.
 

[[File:WMS_PS_5765-09466-01_rev_E.JPG|300px|thumb|left|WMS Power Supply - Revision E (Cyclone)]] 
With Big Guns and games after, the solenoid and lamp power power sections were no longer stuffed because they were relocated to the Aux Power board. The GI relay is also missing on these boards because discrete GI relay boards were placed under the playfield and/or behind the backbox lamp insert. By doing this, specific GI strings could be turned on/off versus "all or none" of the general illumination. This later board has the fuses only for display and 5V power. In a pinch, the unstuffed parts could be installed.

Starting with Big Guns, 2 100mA (1/10A) SB fuses are installed just to the left of the power supply in the backbox. These fuses protect the +100V and -100V circuits against shorts. Not all games used 1/10A slo-blo fuses. Some games used 1/8ASB fuses instead. This may have been due to 1/8ASB fuses being more readily available. 

The schematics for this power supply also list part numbers MPSD52 and MPSD02. The equivalent part number for an MPSD52 is a 2N5401. The equivalent part number for an MPSD02 is a 2N5551.
 

[[Image:System 11 Regulator Board.JPG|300px|thumb|left|Taxi and After Power/Regulator Board]]
[[Image:WMSPSSchematic1503015031.jpg|300px|thumb|right|Schematics for Taxi and After Power/Regulator Board]] 
This power supply was used from Taxi thru the remainder of the System 11 game production.
Note that Taxi used an early revision of the board. The placement of some of the resistors and zener diodes in the HV section of that board is different from later boards.
 

===50V Flipper Power Supply Board===
[[File:Williams50VPowerSupply.jpg|300px|thumb|left|50VDC power supply as used in System 11 (nothing) and 11A games (C-9939).]] 
System 11 (nothing) and System 11A games all used the 50V power supply board as pictured at left. This simple board takes 48VAC from the transformer secondary and uses a 35A/400V bridge rectifier to produce about 50VDC. The voltage is smoothed somewhat by a 100uf electrolytic capacitor. The transformer secondary is protected from a short in the bridge rectifier by either a 4ASB or a 5ASB fuse. Be sure to consult the manual for your game for the proper fuse value. Never overfuse a circuit.
 

===Auxiliary Power Driver Board===
At least two different revisions of the Aux Power Board were used in System 11B/11C games, pictured below.
[[File:WMS Space Station Aux Power Driver D-11813-552.jpg|400px|thumb|left|Auxiliary Power Board from Space Station (D-11813-552)]]
[[File:System 11 Power.JPG|400px|thumb|center|Auxiliary Power Board from Earthshaker (D-12247-568)]]
 

===Interconnect Boards===
[[File:WMS Space Station Interconnect.jpg|300px|thumb|left|Backbox Interconnect Board from Space Station]]
[[Image:System 11 Lamp Board.JPG|300px|thumb|right|Backbox Interconnect Board from Earthshaker]]
The interconnect board was essentially designed for ease of manufacturing and assembly. When Williams ultimately settled on using the same unit in all games, (give or take some parts here or there), modularity was apparent too. There was no longer a need to build complex, custom wiring harnesses between the CPU / driver board, backbox insert, and playfield. The interconnect board remedied this issue. 

[[File:BanzaiRunInterconnect.jpg|300px|thumb|right|Backbox Interconnect Board from Banzai Run]]Although the first four System 11B games, which include Big Guns, Space Station, and Cyclone use some form of an interconnect board, it wasn't until Swords of Fury when the interconnect board was used as a standard for the remaining System 11 games. The interconnect for Banzai Run (shown on the right) is completely different from anything else used by any game.

The interconnect board used in Swords of Fury uses a different part number, D-12185-559, compared to later System 11 games that used part number D-12313-x (x denotes the game's model number). They are not interchangable. Swords of Fury and Taxi had lane change switches still mounted on the cabinet. With later games lane change switches were removed and two optocouplers at position U2 and U3 (connected to the switch returns) were added to the board. The circuit is essentially the same as was used in early WPC games and enabled elimination of problematic physical lane change switches from the game. Starting with Jokerz, the third coupler at position U1 is used by the game software to check if the A/C relay on the aux power board is working. U1 transmits information back to the MPU as switch 2 on the switch matrix, provided that the A/C has energized.

The early versions of the interconnect board were located on the left side of the backbox and positioned vertically. The more common interconnect boards were located in the backbox positioned horizontally, just below the CPU board. The later board passes the following circuits:
*lamp general illumination circuits
*flipper power and ground
*lamp columns and rows
*switch columns and rows
*flash lamp power

What differentiates the board from game to game are the resistor values used for the flash lamp power circuits. In some cases, some of the resistors are left unpopulated and / or a zero ohm jumper is installed.
 

===Master Display Driver Board===
====System 9 (C-8363)====
[[File:WMS Sys9 SS Sorc Master Display.JPG|300px|thumb|left|C-8363 Early System 9 Master Display Driver Board]] 
This is the same master display that is used on all System 6A and System 7 games and is used on most System 9 games.
 

====System 9 (D-10749)====
[[File:WMS-D-10749.jpg|300px|thumb|left|D-10749 Late System 9 Master Display Driver Board]]
 

This master display board was introduced during the System 9 run and is mostly found in some of the later Comets that were manufactured. The major difference between this master display board (D-10749) and the previous master display board (C-8363) is the D-10749 board replaced the card-edge connectors used on the C-8363 with pin-type connectors.

Any System 9 machine that is wired with card-edge connectors to use a C-8363 master display board can be converted to use a D-10749 master display board by re-wiring to use pin-type connectors.

The following table shows the mapping of the connectors & pins from a C-8363 to a D-10749 to aid in this conversion:

{| class="wikitable"
!D-10749 Connector-Pin
!Function
!C-8363 Connector-Pin
!Notes
|-
|J8-1
|Strobe 16
|J5-14
|
|-
|J8-2
|Strobe 15
|J5-16
|
|-
|J8-3
|Strobe 14
|J5-17
|
|-
|J8-4
|Strobe 13
|J5-13
|
|-
|J8-5
|Strobe 12
|J5-12
|
|-
|J8-6
|Strobe 11
|J5-15
|
|-
|J8-7
|KEY
|
|
|-
|J8-8
|Strobe 10
|J5-2
|
|-
|J8-9
|Strobe 9
|J5-4
|
|-
|J9-1
|Strobe 8
|J5-3
|
|-
|J9-2
|Strobe 7
|J5-11
|
|-
|J9-3
|Strobe 6
|J5-10
|
|-
|J9-4
|Strobe 5
|J5-9
|
|-
|J9-5
|Strobe 4
|J5-8
|
|-
|J9-6
|Strobe 3
|J5-7
|
|-
|J9-7
|Strobe 2
|J5-6
|
|-
|J9-8
|KEY
|
|
|-
|J9-9
|Strobe 1
|J5-5
|
|-
|J10-1
|D1
|J7-4
|
|-
|J10-2
|C1
|J7-2
|
|-
|J10-3
|B1
|J7-1
|
|-
|J10-4
|A1
|J7-5
|
|-
|J10-5
|D2
|J7-8
|
|-
|J10-6
|KEY
|
|
|-
|J10-7
|C2
|J7-7
|
|-
|J10-8
|B2
|J7-6
|
|-
|J10-9
|A2
|J7-9
|
|-
|J10-10
|Comma 1 & 2
|J5-18
|
|-
|J10-11
|Comma 3 & 4
|J5-1
|
|-
|J10-12
|Blanking
|J7-3
|
|-
|J11-1
|GROUND
|J6-5
|
|-
|J11-2
|KEY
|
|
|-
|J11-3
| -100 VDC
|J6-6
|
|-
|J11-4
| +100 VDC
|J6-2
|
|-
|J11-5
|N.C.
|J6-4
|
|-
|J11-6
| +5 VDC
|J6-3
|
|-
|
| -100 VDC
|J6-1
|N.C. on D-10749
|}

====System 11 (Discrete Displays High Speed to Pin Bot and Banzai Run)====
[[File:WMS-D-10877.jpg|300px|thumb|left|System 11 Master Display Driver Board]]
[[File:D-10877WithAlternate7180.jpg ‎|300px|thumb|right|System 11 Master Display Driver Board with UDN7180 "daughter cards". Image courtesy of Aaron Gross.]]
The image at right shows "daughter cards" that replace UDN7180 chips, which were beginning to be become expensive and harder to obtain during the production run. The daughter cards use discrete transistors, much the same way as one version of the older System 3-6 Master Display Panel did. U9, U12, U13, and U14, originally UDN7180s, have been replaced on this board.
 

====System 11A (Millionaire / Early F-14)====
[[File:WMS-D-11414-1.jpg|300px|thumb|left|System 11A Millionaire Display Driver Board]]
This PCB actually came out of an early F-14 where they were recycled. Millionaire had it fully populated with additional lamp covers. The mounting brackets for the later D-11610 display changed so if you get a replacement for your F-14 first check which one is used in your game.
 

====System 11A/B (F-14 to Swords of Fury)====
[[File:WMS-D-11610.jpg|300px|thumb|left|System 11A/B 4 7 Digit Segmented Displays Driver Board]]
 

====System 11B (Taxi and Police Force)====
[[File:WMS-D-12232-2.jpg|300px|thumb|left|System 11B Display Driver Board D-12232-2 for 2 16 digit segmented displays + one external connector for a 7 digit display]]
Taxi and Police Force uses a D-12232-2 master display with J4 ribbon connector stuffed. If it's missing from the game, any other dual 16 digit alphanumeric can be used to make it work with Taxi and Police Force. You would need to add U3 (6118), resistors R10, 11, 12, 13, 15, 16, 17, 18 (10K) and connector J4. Jumper W1 should be added to connect the two center segments g' and m' on the lower display to form one large center segment g'. Jumper W2 should be added to light the comma on the jackpot display. Remove resistors R54, 56, 57, 60, 62, 64, 65, 67. The removal is these resistors makes the lower display essential a numeric display.
 

====System 11B (all other WMS 11B/C games)====
[[File:D-12232.jpg|300px|thumb|left|System 11B/C Display Driver Board D-12232-1 for 2 16 digit displays]]
 

====System 11C (Riverboat Gamber)====
[[File:WMS-D-12232-3.jpg|300px|thumb|left|System 11C Display Driver Board D-12232-3 for 2 16 digit displays and 2 connectors for 7 digit jackpot displays]]
Riverboat Gambler uses a D-12232-3 master display with all ribbon connectors stuffed. If it's missing from the game, any other dual 16 digit alphanumeric can be used to make it work with Riverboat Gambler. You would need to add U3 and U4 (both a 6118), resistors R10, 11, 12, 13, 15, 16, 17, 18 (10K) and connectors J4 and J6. Jumper W1 should be added to connect the two center segments g' and m' on the lower display to form one large center segment g'. Jumper W2 should be added to light the comma on the jackpot display. Remove resistors R54, 56, 57, 60, 62, 64, 65, 67. The removal is these resistors makes the lower display essential a numeric display. This display can also be used in Police Force and Taxi.
 

====System 11B/C (all Bally 11B/C games)====
[[File:WMS-Bally-L16-Display.jpg|300px|thumb|left|WMS Bally left side 16 digit Master Display Driver Board]]
 
[[File:WMS-D-12502-1.jpg|300px|thumb|left|WMS Bally right side 16 digit Master Display Driver Board]]
 

===Other Boards===
====Sound Overlay Board (C-13287)====
[[File:WhirlWindSoundOverlayBoard.jpg|300px|thumb|left|Williams "C-13287 Sound Overlay Solenoid Board" as found in WhirlWind.]] 
This relatively simple board was used on Whirlwind only to accommodate 5 additional solenoids (flashers or motors). The board logically sits between the System 11 MPU and the sound board, intercepting data normally sent directly to the sound board, and acting on that data only when specific codes are commanded. The board also relays data not specifically intended for it, on to the sound board.
 

====High Current Driver Boards====
[[File:WMS C-12493 High Current Driver Board.JPG|300px|thumb|left|Williams C-12493 High Current Driver Board from Earthshaker]] 
The high current driver board was used on Earthshaker to drive the shaker motor. It was used on several other Bally/Williams WPC games while designated different part numbers.
 

====Space Station Opto Position Board (C-11872)====
[[File:SpaceStationOptoBoardC-11872.jpg|300px|thumb|left|Williams C-11872 Space Station Opto Positioner PC Board Assembly]] 
This board is unique to Space Station. The "blobs" at Q1 and Q2 (both 2N3906s) in the picture at left are clear silicone caulk used to dampen vibration on the board. 
 

====Flash Lamp Resistor Board (Remotely Located)====
[[File:WMS Flasher Board Pinbot.JPG|thumb|300px|left|Flash Lamp Resistor Board (from Pinbot)]] 
The earlier design of flash lamp resistor board was mounted under the playfield within in the vicinity of the flash lamp circuit(s) that were powered by it. Each board had a maximum of 4 power resistors (2 per flash lamp circuit). The higher resistance resistor is 330 ohm 7 watt, while the lower resistance resistor is 5 ohm 10 watt. The purpose of the larger value resistor is to keep the flash lamp powered with minimal voltage. This keeps the flash lamp filament "warm", which puts less of a strain on the flash lamp. In turn, it is supposed to extend the life of the flash lamp. The smaller value resistor is used as a current limiting resistor which allows the solenoid voltage to be supplied to power the flash lamp. By powering the flash lamps with solenoid voltage, it eliminates the need for an additional, dedicated secondary transformer winding.

Note: If LED flash lamps are installed instead of incandescent lamps, the 330 ohm warming resistor must be removed from the circuit. If it's not removed the lamp will remain on, albeit not at full intensity.
 

====Flash Lamp Resistor Board (Centrally Located)====

<center>
<gallery widths=250px heights=380px perrow=3 caption="Flash Lamp Resistor Boards">
File:WMS Big Guns Resistor Board.jpg|<center>D-11814-557(Big Guns)</center>
File:CycloneBigGunsFlashlampBoardD-11814-564.jpg|<center>D-11814-564 (Cyclone)</center>
File:WMS_Space_Station_Resistor_Board_D-11814-552.JPG|<center>D-11814-552(Space Station)</center>
</gallery>
</center>
 

The flash lamp resistor boards were used on early System 11B games prior to the use of the "standardized" interconnect board. The board is located in a very awkward location. It is screwed to the back of the lower cabinet. Big Guns, Space Station, and Cyclone all have this board in this location. 

The resistors on the board "eat current" (limit current) since the 13V #89 flash lamps are wired to coil voltage (about 38VDC). When implementing this board, Williams chose to change the wire colors as the circuit passes through the board. Combined with the generally poor Williams System 11 documentation, this makes it tough to track down problems with non-working flash lamps. On the plus side, the wire wound cement resistors on the board do not fail often, probably due to the location of the board (resistor boards located under the playfield have high resistor failure rates due to heat and vibration). However, they obviously can fail. If there is power at the flash lamp, but grounding the flash lamp transistor does not light the lamp, the associated drive transistor may have failed. 

The flash lamp resistor boards were abandoned after Space Station. Flash lamp circuits and resistors became integrated into the "standardized" interconnect board.
 

====A/C Relay====
[[File:WMS Sys1WMS Sys11 Early AC Relay.jpg|300px|thumb|left|A/C relay board (early design ie. F-14, Pinbot)]]
[[File:WMS Space Station Aux Power Driver D-11813-552.jpg|300px|thumb|right|A/C relay placed on aux power driver board starting with 11B games (later design)]] 
Starting with Road Kings, System 11 games make use of what is referred to as an A/C relay. The purpose of the A/C relay was to drive twice the amount of coils and flashers by using half the amount of drive transistors. This process is commonly referred to as "multiplexing". Typically, if the A/C relay was at rest, the "A side" solenoids would engage. When the A/C relay was powered, the "C side" flashers would engage. However, there were sometimes solenoids multiplexed with other solenoids. 

For example, High Speed, which does not use an A/C relay, uses 8 discrete drive transistors to drive solenoids / flashers 1-8. Pinbot, which does use an A/C relay, uses the same 8 discrete transistors to drive solenoids / flashers. However, a total of 16 solenoids and flashers (A side and C side) are driven. By employing the use of an A/C relay, the System 11 MPU / driver board could be used for many more years without a "drastic" redesign. 

Initially, the A/C relay was located on a small circuit board under the playfield for System 11/11A games. Likewise, this A/C relay board did not have Molex header connections. Wires were directly soldered to the circuit board. Once the Auxiliary Power Driver Board was introduced with the System 11B platform (starting with Big Guns), the A/C relay was moved to this board for all subsequent System 11B/11C games.

In the example of the A/C relay shown in the pic on the left, the only way to discern that the A/C relay is the highlighted relay board is due to the wire colors soldered to the board.
 

====Diode Board for Multiplexed Solenoids====
[[File:WMS Sys1WMS Sys11 Early Diode Board. As Found.jpg|300px|thumb|left|Diode board as found mounted to the bottom of the playfield (Pinbot)]]
[[File:WMS Sys1WMS Sys11 Early Diode Board.jpg|300px|thumb|right|Diode board from Pinbot]]
[[File:WMS Space Station Aux Power Driver D-11813-552.jpg|300px|thumb|left|Diodes from diode board moved to aux power driver board starting with 11B games]]

 

====Motor Control Board (D-12045)====
[[File:D-12045.jpg|300px|thumb|right|Williams "D-12045" as found in Cyclone, Jokerz!, Riverboat Gambler and Diner.]] 
This board is used in 4 Williams Games
* Cyclone ... for the random award wheel
* Jokerz! ... for draw poker (the wheel has various cards pictured on it),
* Riverboat Gambler ... for the backbox roulette wheel and
* Diner ... for the clock hands count time.

The board uses a single U-opto to detect the wheel at the "home" position. The MPU implements an "open loop control system" stepping the motor to the desired position while assuming that each step was successful. The game flags an issue with the PCB/motor assembly when the software thinks that the wheel should be at the home position but the opto beam hasn't been broken by the opto interrupter on the back of the wheel.
 

===Flipper Coils===
[[File:WMS Sys11 Flippers.JPG|thumb|left|300px|Serial wound flipper coils as seen on earlier (pre F-14 Tomcat) System 11 / 11A games (pic from Pinbot)]]
[[File:WMS Serial Flipper Schems.JPG|right|300px|thumb|Wiring schematic for serial wound flipper coils]] 
Early System 11 and 11A games used serial wound coils. These coils only have a single diode on them.
 

[[File:Placeholder.jpg|thumb|left|300px|Placeholder for Parallel wound flipper coils as seen on later (post F-14 Tomcat) System 11A/B/C games (pic from xxxx)]]
[[File:Parallel_Wound_Flippers.jpg|right|300px|thumb|Wiring schematic for parallel wound flipper coils]] 
Later games (starting with F-14 Tomcat) used parallel wound coils, which have 2 diodes on them.
 

System 11 games use different parallel wound flipper coils dependent on flipper placement and application. Below is a chart of the flipper coils used, their wrapper color, and strength.

{| class="wikitable"
!colspan="4" |System 11 Flipper Coils
|-
!Part #
!Color
!Strength
!Notes
|-
|FL-11753 || Yellow || Weakest ||
|-
|FL-11722 || Green || Weaker ||24-600 series wound similar strength
|-
|FL-11630 || Red || Standard ||23-600 series wound similar strength
|-
|FL-11629 || Blue || Strongest ||
|}
 

===Accessing Bookkeeping, Settings, and Diagnostic Modes===
[[File:System11CoinDoorButtons.jpg|300px|thumb|right|Example System 11 Coin Door Buttons. The Advance button is missing it's black cap, and yes...that is a bit of soft drink spooge on the bracket.]]
The coin door buttons for system 9 and 11 games are shown at right. The function of the three buttons is (from left to right in the picture)...
*Reset High Score to Date
*Auto Up/Manual Down
*Advance

Function of the Reset High Score to Date is self explanatory.

The Auto Up/Manual Down (AUMD) button is interpreted by the game software in multiple ways. Starting from attract mode, if the AUMD switch is up, pressing the advance button causes the game to enter audits and adjustments mode. If the AUMD switch is down, pressing the advance button causes the game to enter diagnostic mode. With the AUMD button in the up position during many of the diagnostic tests, the next step in the test will be automatically entered. For example, display test will display each digit on the display in turn. Coil test will advance through each coil. A particular step of the test may be paused on by pressing the AUMD button down.

The Advance switch moves the diagnostic, audit, or adjustment to the next step (or previous step if the AUMD button is down, except in diagnostic mode).

When in adjustments mode, the credit button is used to zero, turn off, or turn on features. 
Note: One of the adjustment settings (adjustment 69 on High Speed for example) can be used to clear all of the game audits.

At the end of all diagnostic tests, the game will enter audits next, and then adjustments. To exit diagnostics, audits, and / or adjustments, either advance until the last adjustment, or simply turn the machine off.
 

===Transformer Power Selection Connector===
<center>
<gallery widths=350px heights=400px perrow=2 caption="System 11 Power Selection Jumpers">
File:WMS Sys11 Transformer Power Selection.JPG|<center>Typical power selection connection for a System 11 transformer - 115VAC (from Space Station)</center>
File:System11European220VSelection.jpg|<center>European power selection connection for a System 11 transformer - 220VAC. 1 - Black, 4 - White, 3/6 - Orange. ''Image courtesy of Chuck Sanderson''</center>
</gallery>
</center>
 

==Problems and Solutions==
===Sporadic Problems in General - System 9===
[[File:WMS Sys9 Headers.JPG|300px|thumb|left|Cracked Header Joints and Headers cut too deeply by factory on System 9 MPU]] 
Just like the previous Williams platforms, the System 9 platform is prone to cracked solder joints on the header pins. Likewise, Williams' board manufacturers had some tendencies to cut the header pins too short on the solder side. By cutting the pins too short, the cuts partially go through the solder meniscus. Cutting through the solder meniscus makes a solder joint less reliable, and it may prematurely fail over time. 

By having cracked solder joints and / or cut solder meniscus, sporadic issues may occur. To resolve a cracked solder joint issue, the best approach is to completely remove the old solder, and add new solder to the joint. Due to dirt and contaminants, simply adding solder to the existing joint is not sufficient. If the header pins are cut too short, an attempt to remove the solder and new solder can be made. However, in some instances the only resolution is to replace the header pin connector. It is recommended to use a [http://www.greatplainselectronics.com/Category-79.asp high quality replacement header].
 

===Power Problems===

====Bridge Rectifier Fuses====
[[File:WMS_Sys11_Fuses_Added_Before_Lamp_Solenoid_Bridges.JPG|left|thumb|300px|Fuse holders with 8 amp slo-blo fuses added to one of the AC inputs to each of the bridge rectifiers. (Pinbot)]]
[[File:System11AdditionalFuses.jpg|right|thumb|400px|The updated schematic (from High Speed) showing placement of additional transformer secondary fusing for solenoid and controlled lamp bridge rectifiers.]] 
A design flaw carried over from the earlier systems was the lack of fuses between the transformer secondary and the bridge rectifiers used for solenoid and controlled lamp power. In theory, if either of these bridges short, the main power fuse in the game should blow. But that is not always the case. If the primary power fuse fails to blow, the wiring between the transformer secondary and the bridge becomes the fuse. The resulting melted wiring is not pretty!

For games before Big Guns, interrupt one of the AC input lines and install a fuse holder with an 8 amp fuse installed (Williams opted to use an 8A normal blo, while Data East chose to install 8A slo-blo fuses). For games after Big Guns, an 8A normal blo fuse is already present between the transformer secondary and the controlled lamp bridge. As for the solenoid bridge, the addition of the auxiliary power driver board added fusing to protect this circuit. The 25V and 50V solenoid bridges were added to this board. Both bridges are fused with 4A slo-blo fuses.

A nice solution for this problem in the Inkochnito Bridge Board.
Surf on over to http://www.inkochnito.nl. Click on the Bridge Board image for more information.
 

====Alternate to the 12 position wafer connection====
[[File:DE-WMS-System11PSCN1Alternative.jpg|300px|thumb|left|The severely burned wafer connector at Data East equivalent of J1 here has been replaced with parts currently available. Pins 5 and 8 are not populated as those connections are not used.]] 
The 12 position "wafer" connector (CN1 or J1 for Williams games), can be replaced with currently available parts, shown at left. The original "wafers" are difficult to find and pricey.
Part number for the alternate connector is Molex 03-09-2121 or 03-09-2122.
 

====Rottendog Power Supply Missing 5v Failure====
If an aftermarket Rottendog WDP011C power supply is missing 5v, and other common causes of a missing voltage have been ruled out, then it's likely that the 5v regulator at U191 has failed. An available replacement is the Texas Instruments PTR08060 5v regulator from [https://www.mouser.com/ProductDetail/Texas-Instruments/PTR08060WVD Mouser] or [https://www.digikey.com/en/products/detail/texas-instruments/PTR08060WVD/1698955 Digikey].

====Rottendog Power Supply - Big Guns & Cyclone GI Comes On, Game Doesn't Boot====
If using the now obsolete Rottendog WDP011A power supply for Williams Cyclone or Big Guns, the +12v jumper may have to be moved from the bottom jumper location to the top. If a Rottendog equipped Big Guns or Cyclone turns on the GI lights, but the game doesn't boot, (only the 5v light on the CPU is lit), this is most likely the reason.

===System 11 MPU Jumpers===
Normally, jumpers on the MPU board do not require modification. The default configuration works for all System 11 game ROMs. However, there are 5 exceptions as follows...

W7 - Language Select Jumper

W7 is used only in games up to Cyclone. Games with 16 digit alphanumeric displays do not use this jumper. If installed, the game automatically reverts to English after losing the content of the RAM. If a different language is preferred, the "adjustments" menu provides an option to change the default language. Only a few early System 11 game ROMs contained multiple languages. For these games, if W7 is removed, the game generally defaults to German text.

Later System 11 games used language specific ROMs at U26 and U27.

W16 and W17 - Hitachi CPU select
[[File:System11Hitachi6802.jpg|300px|thumb|right|A Hitachi processor, installed at U15, with W16 cut (lower right of pic)]]
The W16 jumper, on original System 11 boards, is in a different location and used for backwards compatibility with system 9 boards. There is no need to change it.

On System 11A and later boards:

*W16 is connected to pin 38 (XTAL) of the 6802/6808 at U15, the CPU responsible for most game operation.
*W17 is connected to pin 38 (XTAL) of the 6802/6808 at U24, the CPU for the sound subsystem.

These two jumpers are used to indicate the manufacturer of the 6802/6808 microprocessor since the clock circuit of Hitachi microprocessors is different from the clock circuit of other manufacturers.

If U15 is a Hitachi microprocessor, remove or cut W16.
If U24 is a Hitachi microprocessor, remove or cut W17.
Otherwise, W16 and W17 should remain installed.

A Hitachi microprocessor can be used in System 9 and System 11 (nothing) MPU boards by simply lifting pin 38 out of the socket. Cutting the pin is not recommended since there may be need for that IC in another board.

W5/W6 and W18/W19 - RAM Type Select ONLY FOR SYSTEM 11B AND 11C

System 11B and 11C MPU boards provide the ability to use either a 6116 or a 6264 RAM at locations U25 and U23 (sound subsystem).

For U25...
*install jumper W5, remove W6 to use a 6116.
*Remove jumper W5, install W6 to use a 6264.

For U23 (sound subsystem)...
*install jumper W19, remove W18 to use a 6116.
*Remove jumper W19, install W18 to use a 6264.

Note: Removing both W5 and W6 from a System ll (nothing) MPU or from a System 11A MPU prevents the switch matrix circuitry from working correctly. One instance of this being done resulted in all switches reporting closure, counting backwards from 64 to 1 while in switch level test. Reference [https://pinside.com/pinball/forum/topic/williams-system-11-switch-levels-all-active this] PinSide thread.
 

===MPU boot issues===
====Steps for Repairing a Dead MPU====
[[File:WMSClockandE.jpg ‎|300px|thumb|right|A scope trace of the 4Mhz crystal input at pin 39 of the microprocessor (blue), and "E", the external clock at pin 37 of the microprocessor (amber)]]
Following is an ordered, disciplined process for reanimating a dead MPU board.

#Inspect for Alkaline Corrosion. Abate all corrosion properly before continuing.
#Test for valid 5/12/-12VDC power to the board.
#Verify correct jumpers are installed (or not installed) for Hitachi 6802/8 processors. More info [[Williams_System_9_-_11#System_11_MPU_Jumpers|here]].
#Note and address any error messages displayed upon boot (if any).
#Validate the ROM images.
#Test socketed chips in a known working board or chip tester.
#Verify a proper (4Mhz) clock signal to the 6802/8 processor at pin 39.
#Verify a proper (1Mhz) external clock signal at pin 37 of the 6802/8.
#Verify the reset circuitry is providing a valid "low and then high" reset signal at pin 40 of the 6802/8. Note that replacing the original reset circuitry with a modern reset generator will lengthen the time until the signal transitions to high. This is normal, and helps with debugging as the signal can be seen much easier.
#Use a logic probe to test for activity on the IRQ (pin 4), Address and Data pins of the 6802/8.
#Use a logic probe to ensure that the following bus buffer chips are correctly mirroring the input signals to the output signals:
##System 9: U1, U2 and U3 (address, R/W, and external clock), and U23 (data)
##System 11: U11 and U13 (address, R/W, and external clock), and U16 (data)
#Install Leon's test ROM to ensure that each 6821 PIA is receiving the correct chip select and data to produce valid outputs at pins 2 through 17. More information regarding use of Leon's test ROM can be found [[Leon_Borre_WMS_System_9_Repair|here]] for System 9 and [[Leon_Borre_Williams_System_11_Repair|here]] for System 11.

====Normal Game Boot Behavior====
[[File:WMS Sys9 Boot Display.JPG|300px|thumb|left|The 7-Segment diagnostic display on a System 9 MPU]] 
Normal MPU boot behavior for System 9 is to show a "0" in the diagnostic display on the MPU. The "0" will light during boot up, and continue to stay lit, as long as the game is on. 

[[File:Diagnostic7Segment.jpg|300px|thumb|left|The 7-Segment diagnostic display on a System 11(nothing) MPU]] 
Normal MPU boot behavior for games with a 7-segment display on the MPU is to show a "0" in the display. The "0" does not go away. The "0" will continue to be displayed under normal boot conditions. 

[[File:DiagnosticLEDs.jpg|300px|thumb|left|+5 VDC, Diagnostics, and Blanking LEDs as found on a System 11A, 11B, and 11C MPUs]] 
Normal MPU boot behavior for games with 3 LEDs instead of the 7-segment display on the MPU is for the "+5 VDC" LED to light first and stay on, then a split second later, the blanking LED will light and stay on. At the same time that the blanking LED lights, the diagnostic LED will begin to blink at a fairly rapid pace with a 50% duty cycle (equal durations of the LED being on then off). The blanking LED will continue to remain on. 

[[File:LEDDiagnosticsIn7SegmentGame.jpg|300px|thumb|left|+5 VDC, Diagnostics, and Blanking LEDs driven by game software expecting a 7-segment display as in High Speed]] 
If a System 11 MPU with 3 LEDs is installed in a game whose original board contained the 7-segment LED diagnostic display first introduced with the System 7 board set, the status of the 3 LEDs won't help much. The game software is attempting to display a "0" (assuming your game boots correctly) on a 7-segment display. Since the board contains just the three LEDs, the MPU circuitry merely lights all three LEDs as shown in the picture at left.
 

====MPU Boot Error Codes====
MPUs used in System 9 and 11(nothing) games display a code on a 7-segment display if an error is detected during boot. MPUs used in System 11A, 11B, and 11C games use the Diagnostic LED to blink a "codes". 

=====System 9 Games=====

The following table lists the error codes displayed on the System 9 MPU 7-segment display. 

{| class="wikitable"
!Code
!Description
|-
|<center>0</center> ||  Normal game boot with no problems detected. The game should be in attract mode.
|-
|<center>1</center> ||  CPU board locked up. Possible cause is memory protect circuit and U18 CMOS RAM "stuck bits".  That is, an actual failure of the CMOS RAM chip or the 6808 processor's ability to communicate error free with the RAM.
|-
|<center>2</center> ||  U20 Game ROM 1 faulty
|-
|<center>3</center> ||  U20 Game ROM 1 faulty
|-
|<center>4</center> ||  U19 Game ROM 2 faulty
|-
|<center>5</center> ||  Blanking signal stuck, coin door closed, memory protect circuit faulty, or the U18 CMOS RAM faulty
|-
|<center>7</center> ||  System failure. Occasionally, the following components can contribute to this problem: U21 (4MhZ crystal), components in the IRQ circuit, broken leads or failed C9 (22uF) in the reset section, or loosely seated ICs on the CPU board. Note that boot code "7" is the hardware default and characteristic of the CPU "reset" signal not complying with the proper low-to-high spec at pin 40.
|-
|<center>Other or no indication</center> ||  U20 Game ROM 1 faulty
|}

If the game is locked up, there may be a bad power supply. The 5 volt logic supply is the first one to check. Then, check the 12 volt supply, which is used to reset the CPU chip. Test for both DC (correct voltages) and AC (too much ripple on the DC circuit).

=====System 11(nothing) Games=====
The following table lists the error codes displayed on the System 11(nothing) MPU 7-segment display. 

Note: These error codes assume that either High Speed, Grand Lizard, or Road Kings ROMs are installed since those were the only three games shipped with this version of the MPU board containing the 7-segment display. Later System 11 MPU boards replace the 7-segment display with 3 discrete LEDs that indicate 5V presence, diagnostics execution, and blanking status. While the System 11(nothing) MPU board works fine with other/later game ROMs, the 7-segment display with later game ROMs doesn't provide useful information other than some confidence that the software is running correctly. With later game ROMs installed and the MPU booting properly, the 7-segment display will appear to alternate rapidly between "0" and "7" (as fast as the "Diagnostics" LED would be flashing in a System 11A through 11C MPU board).

{| class="wikitable"
!Code
!Description
|-
|<center>0</center> ||  Normal game boot with no problems detected. The game should be in attract mode.
|-
|<center>1</center> ||  CPU board locked up. Possible cause is memory protect circuit and U25 CMOS RAM "stuck bits".  That is, an actual failure of the CMOS RAM chip or the 6802 processors ability to communicate error free with the RAM.
|-
|<center>2</center> ||  U27 Game ROM checksum failure
|-
|<center>3</center> ||  U26 Game ROM checksum failure
|-
|<center>4</center> ||  not used
|-
|<center>5</center> ||  Blanking signal "stuck", or the coin door is closed, or the memory protect circuit is faulty, or the CMOS RAM at U25 has failed.
|-
|<center>Other or no indication</center> ||  General system failure. Check the 5VDC power supply as well as the integrity of game ROM 2 at U26.
|}

A zero displayed during Memory Chip Test (using the CPU board switch SW2) indicates that the blanking circuit is NOT functioning properly. 

An eight displayed during memory chip test (using the CPU board switch SW2) indicates that the blanking circuit is functioning properly. 

=====System 11A, 11B, 11C games=====
The following table lists the number of blinks of the DIAGNOSTIC LED, the error message that might be displayed, and the explanation (Source: Williams System 11A game manual. with embellishment). 
[[File:YT.png]] A video demonstrating an MPU indicating a U10 failure (8 blinks) can be found [https://youtu.be/Rhho5nO3YLU here].

{| class="wikitable"
!Code
!Message
!Notes
|-
|<center>0</center> ||  no message ||  Normal game boot with no problems detected. The game should be in attract mode.
|-
|<center>1</center> ||  U25 RAM FAILURE  ||  The RAM at U25 could not be used properly. This means that the RAM failed a read/write test at power up.  The game will remain in the current state and no other tests are performed until the game is turned off, then back on.
|-
|<center>2</center> ||  MEM. PROT. FAILURE  ||  This message means that either:    a) the Coin Door may be shut,    b) the Memory Protect Switch may be stuck in the ON position,    c) the memory protect logic is protecting the memory, or    d) a U25 RAM failure is occurring.
|-
|<center>3</center> ||  U51 PIA FAILURE ||  The PIA at U51 has failed.
|-
|<center>4</center> ||  U38 PIA FAILURE ||  The PIA at U38 has failed.
|-
|<center>5</center> ||  U41 PIA FAILURE ||  The PIA at U41 has failed.
|-
|<center>6</center> ||  U42 PIA FAILURE ||  The PIA at U42 has failed.
|-
|<center>7</center> ||  U54 PIA FAILURE ||  The PIA at U54 has failed.
|-
|<center>8</center> ||  U10 PIA FAILURE ||  The PIA at U10 has failed.
|-
|<center>9</center> ||  IRQ FAILURE ||  The interrupt request line is not working normally. It may be missing, stuck, too fast, or too slow.
|-
|<center>10</center> ||  U27 ROM FAILURE ||  U27 failed checksum (test 11 is skipped).
|-
|<center>11</center> ||  U26 ROM FAILURE ||  U26 failed checksum.
|}

All of the above failures (except #9) may mean that the device has failed but it may also mean that the 6802 microprocessor is unable to communicate adequately or properly with the device. For example, if the CPU is attempting to checksum the game ROM at U27, but one of the 8 data lines leading to U27 has been severed, the wrong data will be received by the microprocessor and the checksum test will fail even though the ROM is perfectly fine.

An U25 RAM failure can occur without actual 6116 RAM failure. One of the most common reasons why U25 RAM failure occurs is lack of power to the RAM chip. If the D1, 1N5817, diode shorts open, logic power will no longer have a pathway to the U25 RAM. However, if the D2, 1N4148, blocking diode is fine, and the battery holder and batteries are fine, power will be retained by the U25 RAM. Although, the batteries will die prematurely if D1 has shorted. Another reason why U25 is no longer powered by the +5VDC logic power is due to a severed trace either caused by a blunt object or battery corrosion.

An interesting side effect to the U25 RAM failure blink code is that the blanking LED will blink 10 times after the single blink from the diagnostic LED.

===== U51, U27, and possibly other boot message causes =====
[[File:System11SocketWornOut.jpg|300px|thumb|left|This OEM System 11 MPU socket is tired, worn out, and no longer provided solid contact with the ROM chip legs.]] 
System 11 MPUs booting with error codes, blinks, or messages on the display may need new sockets for the game ROM(s). In the picture at left, it's easy to see light right through the socket holes (note the brown background vs the white background). The metal female connections have fatigued over time and are no longer providing a solid mechanical connection to the ROM chip legs. Removal and replacement with a quality dual wipe or machine pin socket is advised.

This situation can cause a wide variety of boot problems including complete failure to boot, "U27 ROM failure" message, "U51 failure" message, etc.

Of course, the root cause could be due to many other reasons. The fairly complicated chip select logic outlined on sheet 4 of the System 11 MPU schematics could be the cause. The best way to attack the problem is with a logic probe, ensuring that the various chip select gates are yielding the intended logic states.
 

=====Five "Knocks"=====
Sometimes when turning a system 11 game on, the knocker will fire 5 times, causing most folks to wonder, "what the hey"?. All that knocking is designed to call the operators attention to a potential switch issue. Like the "credit dot" in later Williams games, including System 11 games that support the dot character, these 5 knocks mean that the game hasn't detected the closure of a particular switch (or switches) in a certain number of games. A message will be displayed indicating which switch or switches to examine.

Usually, this is an indication of a failed switch. Most switches get closed during the normal course of game play, long before the game's software counts up to the limit of "games played without closing each switch" and issues this indication.

To address this issue, use the coin door diagnostic panel buttons to enter switch edge test. Manually close the switch. If a switch closure is indicated, either normal game play failed to close the switch (you're not a very good player), or the switch is dirty. Closing a switch with your finger is different than closing a switch with a ball. Your finger generally pushes more firmly on the switch contacts. Clean the switch by dragging an old business card or piece of paper between the switch contacts while pinching the switch blades together with your fingers.

Caution: do not attempt to adjust switches with anything metal while the game is turned on. You will eventually short coil or lamp power to the switch matrix, damaging the MPUs switch matrix circuitry.

If closing the switch manually doesn't register in switch edge test, see the "switch problems" section of this Wiki.

=====System 11 "Adjust Failure" and "Factory Setting"=====
[[File:AdjustFailureMessage.jpg|300px|thumb|left|The typical "Adjust Failure" message on a System 11 game, coin door closed.]] 
The "Adjust Failure" message seen in the picture at left occurs when the game software can't make sense of the information contained in the battery backed RAM at U25. This could be because the RAM has failed, but this is unlikely. The vastly more common reason is that battery backup power has been interrupted to the games battery backed RAM because either the batteries are not installed, dead, or dying. Hopefully, they haven't made a mess of the board by leaking alkaline. See below. "Adjust Failure" is displayed under these conditions when the coin door is closed. 

Note that on some games (not certain if all) which use two 16-digit alpha-numeric displays, the message displayed will actually read "AJSTMENT FAILURE".
 
[[File:FactorySettingMessage.jpg|300px|thumb|left|The typical "Factory Setting" message on a System 11 game, coin door open.]] 
If the coin door is open under these conditions, the message "Factory Setting" is displayed.
 

=====Testing for Battery Backup Power at the RAM =====
[[File:U25_Ram_Test.jpg|300px|thumb|right|System 11: Game off. Meter set to DC volts. Black lead on game ground. Red lead on RAM pin 24.]] 
Testing for power at the RAM chip is easy.

Note: The CMOS RAM chip is located at U18 for System 9 and U25 for System 11.

#Set DMM to DC volts (or on less than 20V if not using an auto-ranging meter)
#Game off
#Black lead on backbox ground
#Red lead on pin 24 of the RAM as shown at right

Three AA batteries normally provide 4.5VDC. If you are reading some voltage, but not quite 4.5VDC, the batteries need to be replaced...and don't forget to move them off of the MPU board while you are at it.

Other causes for low or no battery backup power to the RAM chip are:

#Failed diode at D3 for System 9 or D2 for System 11 - This blocking diode normally prevents the 5VDC source from "charging" the alkaline batteries. This diode is a 1N4148.
#Failed diode at D2 for System 9 or D1 for System 11 - This blocking diode normally prevents the 5VDC battery backup power from powering parts of the board other than the RAM chip. In this case, the batteries will deplete rapidly. This diode is a 1N5817.
 

==== Cross Connecting Black and White Backbox Connectors ====
[[File:WMSSystem7PharoahConnectors.jpg|300px|thumb|left|The infamous System 7/9 connectors that can be cross connected. Yikes!]] 
In one of the biggest mistakes in pinball manufacturing, Williams used two identical 24 pin .062 connectors to connect cabinet and backbox wiring. The connectors are identical with the exception that one is black and one is white. During manufacturing, the wrong color connector was sometimes used. Bottom line: do not simply mate black to black and white to white. Instead, ensure that the wire colors going into one side of the connector are the same as the wire colors coming out the other side. This is the only foolproof method of avoiding the catastrophe of cross connecting circuits, causing certain damage to the MPU board.

For System 9 MPUs cross-connected, the damage can include, but is certainly not limited to, U41, U9, the game ROMs, and one or more 6821s. 

For System 11 MPUs cross-connected, the damage can include, but is certainly not limited to, U11, U31, U34, U35, U36, U44, the game ROMs, and possibly the 6821s.

[[image:YT.png]] A YouTube video demonstrating the repair of a System 9 MPU that was damaged in this way can be found [https://youtu.be/uoYKRJFnm-I here].

[[image:PinSideLogo.png]] An excellent disciplined approach to repairing a System 11 MPU damaged in this way can be found on PinSide [https://pinside.com/pinball/forum/topic/i-fried-my-system-11-cpu-board-now-what#post-7564730 here].
 

==== Relocating the battery from the System 9 MPU board ====
[[File:Leaking_Battery.jpg|200px|thumb|right|Yikes! What a pity...]]
Relocating the 3 AA batteries used to retain settings across power cycles to a location far away from the MPU board is always a good idea. Leaky alkaline batteries are the #1 killer of pinball boards. Sometimes the battery terminals don't look corroded, but the metal rivet which contacts the battery are actually missing. 

If "04 00" in the credit/match display is seen when the game is turned on, the game is in audit mode versus attract mode. Below are several reasons why the game has defaulted to audit mode.
* The batteries have failed and need replacing.
* The battery voltage is not reaching the U18 (5517-2) RAM. Check pin 24 of U18 for approximately 4.3v with the power on and 3.9v with the power off. Lack of battery backup power could also be due to an open D3 (1N4148) blocking diode. This diode is used to keep the CPU's logic power from charging the batteries.
* Blocking diode D2 (1N5817) has shorted, and the batteries are trying to run the MPU board when the game is off.
* There are other problems, such as a faulty 5517-2 RAM.

Simply removing the batteries will not allow a game to boot directly into "attract mode" when switched on. It also will not retain the settings such as the number of balls per game, the free play setting (obtained by setting maximum credits to 0), or high scores. However, a System 9 game will boot, and is still playable with the lack of batteries. To complete the boot sequence into attract mode, open the coin door, switch the game off, and then quickly back on. The game should leave audit mode, and go into attract mode. Credits would need to be added from the coin door, and if necessary, settings would need to be changed before starting a game.

The best option is to remotely locate the battery holder somewhere below all the other boards. This ensures that even if the remotely located batteries leak, they won't leak onto (or even drip onto) components of the MPU board. Use good quality alkaline batteries, mark the date of replacement with a Sharpie, and replace the batteries annually.

Adding a connector between the battery pack and the MPU board is a good idea. You can easily remove the battery pack from the board. Plus, if the batteries are forgotten, and do leak, the MPU board will not have to be removed to add another battery pack. A 3 x AA battery holder is the typical recommended replacement. If only a 4 x AA battery holder is available, a jumper can be soldered in the first battery position. Likewise, a diode can be placed in this position instead. This will prevent the batteries from being charged and 'cooked' by the game if blocking diode D3 on the MPU board fails. Keep in mind that adding a secondary diode to this circuit will decrease the voltage passing to the RAM memory by .5 to .7 volts (the typical voltage drop across a diode) if D3 is still good. Install a 1n4001 or 1N4004 diode in the position closest to the last + terminal (where the Red Wire exits). The banded side of the diode must be pointing in the direction of current flow, which is towards the (+) terminal marking on the MPU board, and away from the battery pack. 

[[File:WMS Sys9 remote bat.JPG|300px|thumb|left|Williams System 9 MPU Board]] 
On the System 9 MPU, solder the battery cables: Ground (Black Wire) to the Bottom Left pad and Positive (Red Wire) to the Top Right. 

After adding a remote battery pack, and while the board is still out of the game, it is a good practice to measure the battery pack's voltage at the (+) and (-) pads of the MPU board. All battery packs are pretty cheaply made, and failures "out of the box" are somewhat common. Checking to make certain the battery pack is functioning before reinstalling the MPU board in the game will save you some headaches.
 

[[File:WMS Sys9 D2 D3.JPG|300px|thumb|left|D2 and D3 Diodes Highlighted on a Williams System 9 MPU Board]] 
Since the MPU board is already out, another good practice is to check the D3 blocking diode. An open blocking diode will not allow the battery pack voltage to pass through to the non-volatile memory, and the newly installed battery pack will be ineffective. Conversely, a shorted blocking diode will allow the board's +5vdc logic power bus to pass through to the battery pack. This in turn, will charge the batteries, while the game is turned on. Alkaline batteries do not like being charged. They will heat up, and fail prematurely, (rather quickly). In worse cases, the new batteries can even leak or explode if charged. Testing the D3 diode is quick and easy, and worth the trouble checking it out. When in doubt, replace the D3 diode with a 1N4148, or add a secondary 1N4004 to the battery pack. Once again, if a secondary diode is added, it will decrease the voltage passing to the 5517-2 RAM memory, if D3 is still good. 

==== Relocating the battery from the System 11 MPU board ====
[[File:RemoteBatteryHolderSystem11.jpg|300px|thumb|left|A remote battery holder installed on a System 11 MPU. The purple wire is positive.]]
 

==== Installing NVRAM instead of batteries ====
[[File:NVRAM DIP.JPG|300px|thumb|left|RAMTRON DIP NVRAM installed on a System 11B board (Cyclone)]]
[[File:NVRAM SMT Adapter.JPG|300px|thumb|right|SMT adapted NVRAM installed on a System 11B board (Transporter The Rescue)]] 
Like most other pinball mpu boards, the battery-backed RAM can be replaced with a non-volatile memory RAM (NVRAM). Replacement RAM that can replace existing 6116 or a 6264 SRAM will be needed. DIP versions are becoming scarce, but there are other solutions available that use surface mount equivalents on a small circuit board that plug into the RAM's socket. Unfortunately, U25 is soldered in on System 11 boards from the factory, and would need to be removed to replace with NVRAM.

If installing any version of 6264 NVRAM on an 11B or 11C board, jumper W5 (located just above U25) needs to be moved to jumper W6. This jumper has a completely different purpose on 11 and 11A boards. 6116 NVRAM will have to be used with 11 and 11A boards, or else modification with wire wrap will be necessary. If 6116 NVRAM is used on 11B or 11C boards, jumper W5 does not have to be chaged.

There are several vendors who sell surface mount NVRAM on an adapter board. The adapter in the picture shown on the right was purchased from [http://www.pinitech.com/products/cat_memory.php Pinitech].
 

It has been documented that some variants of DIP NVRAM may need to have diode D1 replaced with a jumper or jumped around the diode, in order for the game to boot successfully. D1, a 1n5817 diode, has a very low forward voltage drop (about 0.2 volts) vs. the normal 0.4-0.6 volts most other diodes have. If replacing U25 with the memory RAM, some memory RAM will not unlock and allow writes until the voltage is 4.8 volts or so. The 1n5817 D1 diode is just enough to prevent some memory RAMs from allowing writes. To solve this, solder a jumper wire around the D1 terminals, or remove D1 entirely and replace with a jumper. Surface mounted NVRAM on an adapter board is not susceptible to this problem.
 

====Installing a Memory Capacitor Instead of Batteries====
[[File:WMS Sys11B Mem Cap.jpg|300px|thumb|left|Memory Capacitor Added to a System 11B MPU Board. The circled areas show an added jumper for the cap's negative terminal to ground and a jumper added in place of the blocking diode.]]
[[File:System11SuperCapInstalled.jpg|300px|thumb|right|An alternate method of adding a SuperCap. This style cap has two leads on the bottom of the cap. The negative lead of the cap is connected to battery ground via the red jumper wire. The necessary jumper across D2 is circled.]]
Another alternative is to install a memory capacitor. In essence, a memory capacitor is similar to a rechargeable battery, although, the likelihood of a memory capacitor leaking is greatly reduced compared to a rechargeable battery. When the game is turned on, it is charging the capacitor. When the game is turned off (this is where the memory cap slightly differs than a rechargeable battery) the memory capacitor slowly loses its charge over time. Therefore, it is imperative that the game periodically be turned on to allow the capacitor to charge up to its full capacity again. If a game will not be turned on for long lengths of time, a memory capacitor may not be the best solution. 

When installing a memory cap, two things will have to be done. It will be necessary to add a jumper to tie the negative lead of the cap to ground or positive lead to the non-banded side of the blocking diode. The picture to the left shows a jumper added to tie the negative lead of the cap to ground on a System 11B MPU board. Installation on System 11, 11A, and 11C boards is similarly performed. Secondly, the 1N4148 blocking diode (D2) will have to be removed, and replaced by current limiting resistor. A value from 100 ohms to 270 ohms will work. Once the capacitor is installed, and the board installed back in the game, it is a good idea to leave the game on for 15-20 minutes to allow the game to initially charge the capacitor to full capacity. After that, turning the game on monthly for about 10 minutes to allow the cap to recharge is a good idea. 
Note: Both photos show a jumper installed in place of the blocking diode. It is recommended that a limiting resistor be installed instead. 

Note: It has been determined that memory capacitors are not the most effective way to retain memory on System 11 games, if the game will not be turned on for long lengths of time.
 

==== Repairing Alkaline Corrosion ====
[[File:System11MPUDelicateTraces.jpg|300px|thumb|left|Closeup of the delicate traces under the battery holder of a System 11 MPU. Luckily, these cleaned up nicely.]]
[[File:System11CorrosionCropped.jpg|300px|thumb|right|Closeup of traces under the battery holder. Corrosion (darkened spots) has invaded beneath the solder mask (green coating) and is beginning to eat away at the copper traces.]] 
As can be seen at left, the traces on System 11 MPUs are very small. Not much alkaline damage is required to eat completely through these delicate traces. Unfortunately, there are a great many of these traces under the battery holder, and in a very vulnerable position to alkaline damage.

Also, to the left of the battery holder is the reset section of the MPU. That section is, on balance, much easier to repair than the delicate traces under the battery holder and at the 6821 PIAs immediately under the battery holder.

The advice often dispensed to deal with alkaline corrosion is to scrub the affected area with an acid such as vinegar, rinse with water, and then rinse again with isopropyl alcohol. This might work for light surface alkaline corrosion.

Unfortunately, often the alkaline will eat into traces beneath the solder mask or beneath chips. This dictates desoldering affected chips to remove the corrosion and repair traces. The alkaline interacts chemically with the solder making it very difficult to heat. Desoldering from the (presumably undamaged) back side of the board is much easier. Scuffing the alkaline damaged solder with a wire brush to remove the surface layer of damage is also helpful.

Once all damaged components have been removed, sand the affected area carefully with your choice of fine grit sandpaper. 220 grit works well. The objective is to remove the corrosion completely without destroying additional traces. All corroded areas must be addressed.

Next, rebuild traces as necessary. Corrosion tends to sever traces where the trace meets the solder pad of a part. Strong magnification and bright lighting helps. Either tin or conformal coat the bare copper and then reinstall parts.

[[File:WMSSystem11AlkalineDamage-1-Annotated.jpg|300px|thumb|left|Another closeup of the delicate traces near the battery holder of a System 11 MPU. These traces are too far gone for a repair to be considered reliable.]]
[[File:ReplacingSRCPartsSystem11.jpg|300px|thumb|right|A 9 pin, 4.7K bussed resistor network replacing SRC5. Pin 1 is on the right]]
[[File:System11AlkalineCorrosion.jpg|300px|thumb|left|A closeup of alkaline damage that has crept under the solder mask (the darker traces). Eventually, this corrosion will eat completely through the trace, making the board unreliable.]]
[[File:TypicalSRC.jpg|300px|thumb|right|The OEM resistor/capacitor network.]]

At the top of the board are a few "SRC" parts. These are 10 pin resistor/capacitor SIPs. The OEM part connects each driver line to a 4.7Kohm pull-up resistor connected to 5VDC. This guarantees that the signal is held at logic high until the PIA grounds the signal. The OEM part also connects each driver line to a high frequency noise filter capacitor (470pf). These parts are no longer available. A completely acceptable substitute is a 9 pin bussed, 8 resistor network (4.7Kohms) at positions SRC1 - SRC5 and SRC7 - SRC9. This part provides the pull-up resistor. In practice, the high frequency filter capacitor does not impact the displays.

The part is installed as shown in the picture at right, with pin 1 of the part connected to the right side which is labeled pin 1 in the board silkscreen. A 10 pin (9 bussed resistors) part may be used ONLY if the left most pin is clipped and not connected to ground.

An image of the original OEM part is shown at right.

Another example of alkaline corrosion can be seen in the picture on the left. This damage can be cleaned up, retinned, and the board placed back in service.
 

====Blanking Signal Stuck Low or Pulsing====
The blanking signal is a failsafe interlock with critical game functions including the display, sounds, lamp matrix, and solenoids. It prevents operation of each of these game features to protect the game circuitry in the event of a system failure. For instance, if the MPU is not running, and the lamp matrix is stuck on at a particular row or column, those parts will heat up quickly, and at the very least damage that circuitry. Coils remaining locked on could cause even larger damage to the game.

Each of the game functions listed above require the blanking signal to be high (not pulsing but always high) to operate. As an example, the solenoid driver circuitry logically "ands" the blanking signal with solenoid commands using a 7408 AND gates (at U17, U18, U19 and U20 for System 11 or at U56, U57, U60, and U61 for System 9).

Lack of blanking, with the blanking LED never lighting, means that the game program is not running. It either never started running, locked up due to an invalid ROM image or a problem with the data, address, control, or chip select signals on the MPU, or detected a problem with the RAM memory. 

[[File:System11Blanking.jpg ‎|thumb|left|300px|C58, a timing element for the 555 timer. Image Courtesy of Chris Hibler.]] 
In rare cases, C58 can fail (C12 for System 9). C58 holds the input to the 555 timer high between pulses from the display circuitry. This causes the blanking signal to pulse. A pulsing blanking signal can manifest in missing digits on the display, some lamp columns not being turned on, and possibly other issues. C58 is a 1uf tantalum capacitor. If the blanking signal is pulsing, replace C58. 

[[File:WMSSystem11Blanking.jpg|thumb|right|300px|Williams System 11 CPU Blanking Circuit. Image Courtesy of Chris Hibler.]]

The blanking circuit explained

#A properly executing CPU will update the displays by sending data to the display 6821 PIA at U51 for System 11 (and U5 for System 9) at regular intervals (every 2.8 msec).
#This action causes PA2 at pin 4 of the 6821 to pulse high periodically. The DE schematics call this signal "TG". It is merely called "blanking" in WMS schematics.
#The signal is inverted by the 7404 at U36 (U41 for System 9), in at pin 13, out at pin 12 (in at pin 11 and out at pin 10 for System 9).
#The coupling capacitor at C57 (C15 for System 9) can be ignored. These ceramic caps rarely fail.
#The signal is applied to the base (pin 2) of a 2N4403 at Q50 (Q6 for System 9) and to pin 2 of the 555 timer at 1C.
#The 555 timer is configured as a "missing pulse detector" meaning that if it does not detect the pulse that originated upstream at the 6821 PIA at U51 for System 11 (and U5 for System 9), the output of the 555 timer at pin 3 (and 7) will go low, which invokes blanking and protection of the system circuitry.

For the longer, more detailed explanation, [http://arcarc.xmission.com/Pinball/Stern%20Service%20Bulletins/sb/sb75.pdf Stern service bulletin 75] provides the "Blanking Circuit Theory of Operation" for Data East MPUs which are identical to Williams MPUs with respect to the blanking circuit.

When operating properly, the pins of the 555 timer will behave as follows (pin number, logic signal)
#low
#pulsing at the same rate as the 6821 PIA at U51 for System 11 (U5 for System 9), pin 4
#high
#high
#pulsing very rapidly. i.e. "ticking"
#high
#high

If [https://www.pinwiki.com/wiki/index.php/Leon_Borre_Williams_System_11_Repair Leon's System 11 test ROM] runs correctly on an MPU, this guarantees that all data, address, and control signals are working correctly. If blanking doesn't go high with a game ROM installed, ensure that the ROM images are valid. This is by far the most probable once Leon's ROM runs correctly.
 

====Reset Circuit Troubleshooting - CPU Not Consistently Booting====

If the CPU boots some of the time, or boots via turning on / off / on, and the voltages are correct; check the reset circuit for battery leakage damage. If the circuit appears undamaged, check C30 (or C9 for System 9). This 22uF capacitor, in series with a 10 ohm resistor is a RC delay circuit.

Test the capacitor and, if defective, replace it. The 22uF value is not crucial. Using a higher value will just delay the booting of the CPU by an almost imperceptible amount. Values as high as 50uF have been used successfully.

====An Alternative to Rebuilding the Reset Circuit / Using a Reset Generator (System 9)====
[[File:System9ResetGenerator.jpg|thumb|left|300px|Reset section of a System 9 MPU board.]]
[[File:WMSSystem9ResetSection.jpg|thumb|right|300px|The image above shows the single jumper and the exact minimum parts required when using a reset generator on a System 9 MPU. The three electrolytic caps (all 100uf/25V), two inductors, and 5 ceramic caps (all .001uf labeled "102") are part of the 5, 12, and -12 volt power filtering circuitry. The D2, 1N5817 diode isn't needed if an NVRAM is used instead of a SuperCap or remote batteries. However, a jumper must be installed at D2 to power the NVRAM.]] 
The reset section of the System 9 MPU is almost identical to the System 11 reset section. As such, a modification similar to the mod outlined below can be performed on System 9 boards too.

#Remove resistors R6, R8, and R12. Really, all but R6 can simply be clipped off. One through hole at R6 will be used later.
#Remove transistor Q4
#Install a reset generator (MCP120-460GI/TO) where Q4 was removed. Orient the reset generator the same way that Q4 was oriented, matching the PCB silkscreen.
#Add a jumper from the upper leg of where R6 was removed (oriented as shown in the picture, upside-down from game installation) to the via that is about 1/4" southeast of the R6 connection.

That's it. Most of the rest of the reset circuit can be removed, but this provides no advantage since those parts are already "out of circuit" with this modification. After this modification is performed, the MPU board will no longer need the +12v to successfully boot. However, +12v is still necessary to power the sound amplifier on the board.

[[File:System9ResetMinimum.jpg|thumb|left|300px|Another image of the bare minimum part requirement when using a modern reset generator. The three electrolytic caps are all 100uf/25V. Note that the right most electrolytic cap is oriented backwards from the other two. The 5 ceramic caps are all .001uf and are labeled "102". These are sometimes called 1000pf ceramic caps.]] 
The MCP130 reset generator variant, with an internal 4.7K ohm resistor can be used too, but it isn't necessary. This is because the resistor at R170 provides an external 4.7K ohm pull up for the /RESET line.

Note that the reset generator has a longer reset delay than the OEM circuitry. At boot, the 7 segment LED will seem to show a "7" for a fraction of a second. It will turn to a "0" and remain "0" after that, assuming that the board is booting properly.
 

[[File:System9Inductor1.jpg|thumb|left|300px|Factory installed "zero ohm jumpers" where inductors are normally installed on a System 9 MPU board. Image courtesy of John Wart Jr.]]
[[File:System9Inductor2.jpg|thumb|right|300px|Factory installed "zero ohm jumper" where an inductor is normally installed on a System 9 MPU board. Image courtesy of John Wart Jr.]] 
Note that some System 9 MPUs shipped from the factory with zero ohm jumpers installed instead of inductors (see images left and right). When repairing alkaline corrosion, it's completely acceptable to replaced damaged inductors with jumpers.
 

====An Alternative to Rebuilding the Reset Circuit / Using a Reset Generator (All versions of System 11)====
[[File:WMS Sys11 Reset Section.JPG|thumb|left|300px|Reset section of a System 11A MPU board. Components to be removed are circled.]]
[[File:WMS Sys11 Reset Gen.JPG|thumb|right|300px|Reset section with reset generator and jumper installed.]] 

There is an alternative to the stock reset circuit on all versions of the System 11 MPU boards. A reset generator can be installed. Since the reset section of all versions of the System 11 MPU board is susceptible to battery damage, this is a very easy, and minimalistic way to rebuild the reset section. To do so, 4 components will need to be removed and a jumper installed. The following work will have to be done.

#Remove the Q39 transistor.
#Remove the following resistors - (from top to bottom as installed on the board) R58, R60 (these two are just below the Q39 transistor), and R69.
#Add reset generator MCP120-460GI/TO (also used on Data East MPUs) where Q39 was. Orient the reset generator in the same manner Q39 was oriented (pin 1 of reset generator will install in the bottom through hole). In other words, the "flat" side of the reset generator will face to the right.
#Add a jumper between the right pad of R58 and the right pad of R60 (both resistors have been removed).
 

This a very simple, and in some cases, cheaper alternative to repairing the existing reset circuit. After this modification is performed, the MPU board will no longer need the +12v to successfully boot. However, +12v is still necessary for the sound section of the MPU on most boards, except the 11B and 11C variants. Likewise, any of the other components in the reset circuit can be removed if desired. Please consult the System 11 MPU board BOM and schematics to determine exactly what components can be removed. The MCP120-460GI/TO reset generator can be purchased from Digikey or Mouser. The MCP130 variant with an internal 4.7K ohm resistor can be used, but it is not necessary. This is because resistor network SR19 pin 3 is an external 4.7K ohm resistor used to pull up the /RESET line.

Below is a prime example of where a reset generator is very handy. The amount of components replaced are reduced from 15-20 to 1. Note that because this was an 11B board (also true for 11C boards), there is no sound amplifier on the board. Hence, the +12v is not needed at all, and none of the parts related to the +12v were repopulated. If this were an 11(nothing) or an 11A board, the +12V inductor (can be replaced by a simple jumper), the W10/W11 jumper, and associated capacitors (C27, C28, and C29) would need to be populated.

<center>
<gallery widths=330px heights=210px perrow=3 caption="A Prime Candidate for Using a Reset Generator (11B MPU Board Shown)">
File:Sys11 Battery Rot.JPG|Battery alkali leeched into the reset section.
File:Sys11 Battery Rot WIP.JPG|Components removed, affected traces and pads cleaned and treated.
File:S11ResetSectionAnnotated.png|Components repopulated. The image above shows the single jumper and the exact minimum parts required when using a reset generator.
</gallery></center>

[[File:System11MinumunResetSection.jpg|thumb|right|300px|Another image showing the single jumper (string tied to it) and the exact minimum parts required when using a reset generator (System 11B/11C). System 11 (nothing) and System 11A must retain a few more parts.]] 
In the above gallery pics, note that some components in the reset area had to be reinstalled. These components are in the area of the reset section, but are not part of the reset circuitry. They are actually related to the game RAM, enabling CMOS power to reach the RAM and to control pin 18, the chip enable pin of the RAM. Without these parts, the MPU will not successfully boot. Instead, there will be a '''single blink code''' from the diagnostic LED indicating a U25 RAM error (a "1" will display on boards with the 7-segment display). If the game display is connected to the MPU board, a "U25 RAM ERROR" message will be displayed.
*D1 - 1N5817 diode
*Q40 - 2N3904 transistor (a 2N4401 was used in this case)
*R64 - 1 Kohm 1/4 watt resistor
*R65 - 10 Kohm 1/4 watt resistor
*R68 - 4.7 Kohm 1/4 watt resistor

And, once again, for a System 11 (nothing) or a System 11A MPU, both of which have onboard amplifiers in the upper left corner and require 12VDC power, be sure to retain or replace the following parts:
*L2 - 4.7uH inductor (or a simple jumper)
*C27 - .001uf/50V ceramic capacitor
*C28 - .001uf/50V ceramic capacitor
*C29 - 100uf/25V electrolytic capacitor
 

====Connecting a logic probe to the MPU Board====
[[File:WMS Sys9 Logic Probe.JPG|300px|thumb|left|Logic Probe connected to System 9 MPU Board]]
[[File:WMS Sys11 Logic Probe.JPG|300px|thumb|right|Logic Probe connected to System 11 (11A) MPU Board]] 

Of course, +5v and ground can always be acquired at any one of the bypass capacitors, which are located at most every chip, and simply labeled as "B".
 

==== Using a PC Power Supply For Bench Testing MPU Board====

[[File:WMS Sys9 comp PSU.JPG|300px|left|thumb|System 9 MPU connected to a PC power supply]]
[[File:WMS Sys11 comp PSU.JPG|300px|right|thumb|System 11 MPU connected to a PC power supply]] 
The 1J17 power connection is essentially the same for System 9 and all variants of the System 11 MPU boards. The ground connection can be attached to pins 1 through 3. The +5vdc connection can be connected to pins 4 through 6. -12vdc gets connected to pin 8 and +12vdc gets connected to pin 9.
 

===Game resets===
System 9/11 games are far more tolerant of low line conditions vs. the newer WPC games. Some things to check if the game is resetting are the usual culprits for this type of thing: connectors, filter capacitors, slam switches, bad chip sockets, etc. It is good preventative maintenance to replace the +5 volt filter capacitor on the power supply with a new one; most of these are 25+ years old and might be getting to the point of wearing out. Certainly replace them if you are getting resetting on your system 11 game. 

Most system 11 games give an indication that they've been slam tilted; if you're getting a "game reset" but you get a noise and/or a message on the displays beforehand, it is probably a slam switch issue vs. a true reset issue. Check all the slam switches in the game (usually the coin door is the main one, and also the ball roll tilt if present). 

===Solenoid problems===

====A/C solenoid/flasher problems====
[[File:System11AuxDriverBoard.jpg|400px|thumb|left|Williams System 11 Auxiliary Power/Driver Board, showing the A/C select relay, the clear "cube" at the top, center of the picture.]] 
The A/C select relay is a dual "make/break" (DPDT, double pole, double throw) relay that supplies power to either the "A-Side" or the "C-Side". It is located on the Auxiliary Power/Driver Board for games that use the board which was introduced with Big Guns and used on all subsequent games. For games prior to Big Guns, like F-14 Tomcat, the relay is probably located under the playfield. There are exceptions. High Speed and Grand Lizard do not use an A/C select relay. Road Kings uses one for a handful of solenoids, but this game did not follow the 1-8 solenoid convention which games after it adopted.

There are a couple ways that the A-Side / C-Side (A/C after this) relay circuit can fail. If the driving transistor (Q8 for Big Guns and later, Q7 for games prior to Big Guns, and located on the MPU board) shorts, the A/C select relay will be constantly energized, resulting in flashers firing when coils should have fired. If the driving transistor never switches the A/C select relay on, coils will fire when flashers should have fired.

Testing this behavior is easy. Use the diagnostic buttons to select solenoid test, and watch carefully to see what fires. The display will show the coil/flasher under test. The first 8 drive circuits tested will have an "A-Side" and a "C-Side". That is, circuits will fire in the following order: 1A, 1C, 2A, 2C, ... 8A, 8C. If the A/C select circuit is not working correctly, the same coil or flasher will fire twice in a row, once for the A side and once for the C side.

The A/C select relay is generally solenoid 12 in coil test. Placing the "Auto Advance" button in the up position, to repeatedly test solenoid 12, should allow you to hear the A/C relay clicking on and off.

If all of "one side" of the A/C select circuit is not working, the fuse supplying the voltage to that side may be blown. F2 (DC side of BR1) and F8 (AC side of BR1) fuse the 25V circuit. F4 (DC side of BR2) and F7 (AC side of BR2) fuse the 50V circuit. Another suspect is fractured solder joints on the A/C select relay. Reflowing these solder joints is simple. The A/C select relay is relatively heavy and it's weight puts stress on the solder connection at the printed circuit board.
 

[[File:System11A-CRelay-OKOnBothSides.jpg|300px|thumb|left|Williams System 11 Auxiliary Power/Driver Board A/C Select Relay showing normal, working switch contacts.]] 
It is rare for the A/C relay itself to fail. A possible source of trouble are the miniature contacts on the relay wipers. These are high power, high current, contacts that can be filed with a small point file to restore proper current carrying capacity. Under no circumstances should you ever use contact cleaner on these contacts, as this could cause a spark or fire to occur. Be careful to not mangle the contact wipers in an attempt to adjust them. Adjust with care. 99% of the time, these switch contacts need no maintenance at all.
 

[[File:System11A-CRelay-WeldedOnBothSides.jpg|300px|thumb|left|Williams System 11 Auxiliary Power/Driver Board A/C Select Relay showing "welded" switch contacts.]] 
Pictured at left is a disassembled A/C select relay with both the A Side and the C Side connected at the center contact pads. It's rare for one of these relays to "weld" itself to both sides. In this particular instance, the game would fire both the A-side coil and the C-side flasher at the same time.
 

Other failure points are the connectors and headers connecting the aux driver board to the main cpu/driver board. Fractured solder joints can affect the proper operation of the relay. It is good practice to replace, or at minimum, reflow the header pins, and to replace connector pins in their housings with new pins. System 11 games use .156 connectors in most locations.

And finally, the solder joints holding the A/C select relay to the board may fracture and cause loss of connectivity.

On a related note, if the flashers never illuminate during game or test, but the A/C relay physically engages, likewise the flasher lamps are good, and power is present at the lamps, suspect potential failure of the U1 (4N25) U1 optocoupler on the interconnect board. Starting with Jokerz, the U1 optocoupler on the D-12313 interconnect board was used to identify whether or not the A/C relay has engaged. Under normal operation, if the A/C relay has engaged, the voltage on the "C" side passes back to the optocoupler. In turn, there is a switch on the switch matrix, typically switch 2, which receives the signal from the U1 optocoupler. Note that U1 is on some previous games like Taxi, but it was not used.

====Special solenoid problems with RottenDog MPU board====
[[File:RottenDogMPUDIPSwitches.jpg‎|300px|thumb|left| RottenDog MPU with a red switch bank for selecting either Williams or Data East special solenoid implementation.]]
[[File:RDMPU004DIPSwitches.jpg ‎‎|300px|thumb|right| These DIP switches on this RottenDog are configured for a Williams game, even though they do not seem to match the PCB silkscreen.]] 
The RottenDog aftermarket MPU board can accommodate both Williams and Data East special solenoid implementations. This is accomplished with an 8 DIP switch bank, pictured at left. If set to the wrong game system, special solenoids will not operate properly in your game. Note: The DIP switch positions should be set the opposite of what you might think, based on the PCB silkscreen.
 

====Special solenoid problems====
[[File:SpecialSolenoidCircuit.jpg|500px|thumb|right|A typical special solenoid circuit]] 
Special solenoids on system 11 games are similar to the earlier variants used on all previous Williams' board sets. During gameplay/test modes the primary switches on the special solenoids (usually the pops and slings) are active, allowing actuation of those switches to fire the solenoids. This is done by grounding an input to a 7402 logic chip which in turn pre-drives a 2n4401 pre-driver transistor which drives a TIP122 Darlington transistor to fire the solenoid.

During solenoid test mode only, the secondary path to the 7402 is utilized instead to fire the solenoids. Since there are 2 paths to fire the solenoids, it is possible for a special solenoid to work in game/test mode, but fail the solenoid test due to a failed PIA or 7402 chip, and vice-versa.

'''Note:''' The System 9 circuit board architecture provides no physical way to control the special solenoids other than via the primary switch associated with the special solenoid device. Therefore, System 9 special solenoids are not activated during solenoid test.

If a special solenoid actuation switch locks on, the solenoid itself will lock on as well, (hopefully) blowing the associated fuse before blowing all or some of the TIP122/2N4401/7402 circuit. An inline fuse holder can be added to all special solenoids with a 1 amp fuse installed to help prevent this situation.

There is a 22uF capacitor and a 100 ohm resistor mounted across the special solenoid switches. The use of the capacitor and resistor creates what is called an [http://en.wikipedia.org/wiki/RC_circuit RC circuit]. The RC circuit is used to filter noise from the switch signal as well as to ensure a minimum pulse length for the solenoid activation. If using a polarized capacitor the positive terminal goes to the tie point with one end of the resistor attached. Should a special solenoid lock on, and the switch leaves are properly gapped, the issue may be a shorted switch capacitor or resistor.

Most system 11B games do not use the special solenoids in the same way. Special solenoid switches were added to the switch matrix instead, keeping all or some of the solenoid pulses under CPU control. It is easy to identify whether a game has CPU controlled special solenoids by inspecting the activation switches on the special solenoids. If there are both a primary and a secondary switch installed, the game operates via the direct-fire special solenoid setup. (Note that a secondary switch in the case of slingshots does not mean the normal 2nd switch all slings shots employ. Rather, it refers to a switch that only activates when the sling activates. It is installed near the pivot point of the sling arm underneath the playfield.) Also the secondary switches go to CPU connector J18. If nothing is connected to J18, then the special solenoids are CPU controlled. In games like BK2K only the kickers are CPU controlled while the pop bumpers still use the secondary switches. There was no rhyme or reason (no definitive start / stop point) which System 11B titles used special solenoid secondary switches, and which did not. Please refer to the game list [http://www.pinwiki.com/wiki/index.php?title=Williams_System_9_-_11#System_11B above] to determine which did / did not use the secondary switches.

[[File:WMSSystem11Zener1N5234.jpg|300px|thumb|left|6.2V Zener Diodes (ZR3-ZR8) that "protect" the board logic from shorts between the sense switches and coil power. Note: in this image, ZR7 and ZR8 have been replaced]] 
The usual cause of special solenoid circuit failure is a stuck switch that locks the associated solenoid on, causing the TIP-122 transistor to fail and the coil to get so hot that the winding insulation melts (causing a reduction of coil resistance, eventually approaching zero ohms). The zener diode (pictured, left) in the circuit may fail shorted as well. This will cause the associated coil to lock on even after repair of the other damaged circuitry since the zener is connected directly to ground. The shorted zener diode causes the 7402/2N4401/TIP122 circuit to react identically to a switch closure. Gack!

Note: If your game doesn't use the special solenoid switch inputs as in most System 11B games and all System 11C games (i.e. no connection at 1J18), then these zeners serve no purpose and may be clipped off.
 

====Unusual Solenoid Problems====
[[File:WhirlwindPinchedWire.jpg|300px|thumb|left|A pinched wire (white/brown) that causes a tough to find solenoid problem.]] 
The System 11 method of securing boards sometimes causes odd problems. The securing screws must be removed completely to remove a board vs the improved WPC method of sliding the board off the screw head via a "keyhole".

When securing the boards, it's important to ensure that wires aren't pinched behind the board. If a wire is pinched severely enough, the insulation will be displaced and the conductor will contact the backbox ground plain, which can cause a wide range of odd problems.

The wire in the picture shown at left happened to be the ground path for coil #1, the outhole kicker on Whirlwind. When the game was powered on, the coil would lock on until the blanking circuit became active. Pressing the diagnostic/audit coin door button would also result in the coil locking on. This was actually the A/C relay flipping to the coil side for diagnostics and providing power to the coils. The outhole coil had a path to ground via the pinched wire and would lock on. A game could be started and the coil appeared to work properly until any of the 1 through 8 coils were activated (when the A/C select relay would energize again). At that time, the outhole coil would fire at the same time as the other 1 through 8 coil.

This one was a real head scratcher!
 

===Flash Lamp Problems===
[[File:System11WarmingBoard.jpg|300px|thumb|left|System 11 (High Speed) warming board. Note that flashlamp power is no longer routed through this board. The orange wire connects to two flash lamps wired in series which are then connected directly to flashlamp power. The two black wires are ground. The gray-blue wire is the path to ground via a drive transistor.]]
System 9/11 flash lamps are driven by the same kind of circuitry that drives solenoids. Flashers are generally wired two in series (like old Christmas lights). If one lamp fails, the neither lamp will light. They are wired in series so that they split the DC voltage across two lamps, preventing them from burning out quickly.

To make the flashlamps "agile" (i.e. turn on rapidly) and to extend the life of the flashlamps, a "warming" circuit was employed which connects two series flashlamps to coil power via a 330 ohm 1 watt resistor. This causes the lamp filament to turn on very slightly, and to "warm up", ready for the power to find ground via a 1 ohm (5 ohm in System 11) resistor.

Over the years, these games have undergone "maintenance" to replace parts on the resistor board and have sometimes also been rewired, attaching the wires to different solder lugs on the flashlamp warming board.

Note: Warming boards are not shown in any of the System 11 documentation.

Note: If LED flash lamps are installed instead of incandescent lamps, the 330 ohm warming resistor must be removed from the circuit. If it's not removed the lamp will remain on, albeit not at full intensity.
 

===Lamp problems===
This may seem painfully obvious, but with any lamp problem, where all lamps in the same circuit are not lighting, first see if the associated fuse is blown.
 

====General Illumination Issues====
As a rule of thumb, general illumination (GI) lamp issues with System 9 or 11 games are dependent on the era of the game. The reason for this is GI circuits passed through different boards over the years. And, the majority of GI issues are typically due to the circuit board. Not so much the circuit board itself, but the junction between the header pin connections on the circuit board and the connector pins located in the female housings. 

It is extremely common for the header pins and / or the female connections related to the GI circuit to heat up, and in worse cases char or burn. When some of these games were in operation earning money, they could potentially be turned on for 8, 12, or more hours every day. If the connectors were compromised at some time in the game's life, the issues become compounded. 

The problem is a vicious cycle. If either side of the connector heats up, it creates more resistance. If it creates more resistance, it draws more current. If it draws more current, it heats up. This cycle continues until the connector blows the circuit's fuse (provided the proper fuse is installed and not by-passed), the connectors are so bad that the circuit no longer has continuity, or the connectors are replaced with new ones. It is recommended that both the male header pin connector be replaced and the associated pin connectors which connect to it. Replacing only one side of the connector is only asking for repeat problems down the road. Header pins rated for 7 amp are highly recommended as a replacement. If the 7A headers are used, the likelihood of the connector failing due to heat is greatly reduced. Likewise, the use of Molex Trifurcon connector pins are recommended. 

Another prevalent problem is the failure of the relay board or the relay board connectors. GI relay boards are typically found under the playfield and on the back of the lamp insert panel. The job of the relay board is to switch the GI lamps on/off for special lighting effects. Over many years of operation, the solder joints on the connector may fracture. Although it is more common for the male/female connectors to burn badly. Repinning these connectors, as is typical for GI connectors, is the prescribed fix. 

=====Games From Space Shuttle to Fire!=====
[[File:WMS Sys11 GI Circuits.JPG|300px|thumb|left|Typical System 9/11 Power Supply with GI Drivetrain Notated]] 
During this time period, general illumination entered the power supply [1 / 2], was parsed, and exited the power supply as 4 separate circuits [4]. Although there were 4 discrete GI circuits with 4 separate fuses [5], all 4 circuits were turned on/off via one relay [3] located on the power supply. 

Note that the factory connection on the power supply for System 9 games differs than what is shown in the picture. Connections [1 / 2] do not exist on System 9 games, and only two wires are used to input the general illumination instead of four.
 

=====Games From Big Guns to Swords of Fury=====
[[File:Cyclone Interconnect.JPG|300px|left|thumb|The interconnect board from a Cyclone mounted to the left side of the backbox]] 

With all the games mentioned in this particular section, there were some design growing pains. Williams was creating a preliminary interconnect board, however, it was very different from game to game at first. Therefore, GI issues may occur at the power supply connections, the interconnect board connections, and / or at one of the discrete GI relay boards used. Since single-sided circuit boards were used for the GI relay boards, cracked solder joints where the relay is soldered to the board is possible in addition to the header pins.

A shown at the pic on the left, the general illumination headers, connectors, and connector housings have been changed out due to fatigue / failure. This is a common failure point on games such as Big Guns, Space Station, and Cyclone.
 

=====Games From Taxi to Bugs Bunny's Birthday Ball=====
The games included during this era used a somewhat standardized interconnect board located below the CPU board. The GI circuits coming directly from the transformer enter the board on the right side at connector J6. The top 4 wires are yellow and the lower 4 wires are yellow with a white trace. In actuality, the GI wires are only 4 wires, instead of 8 wires. Once the upper 2 wires reach the board, each of them are daisy-chained through the insulation displacement connector (IDC). Equally, the bottom 2 wires are connected in the same fashion. This was presumedly done to reduce cost, and decrease the life expectancy of the connection as a whole. 

[[File:WMS Interconnect BK2K GI Marked.JPG|left|300px|thumb|Williams Interconnect Board with general illumination wire colors marked. Interconnect board is from a Black Knight 2000]]
The most typical header connections that fail on the interconnect board are J6 (the GI input and return) and J7 (the GI output and return lines to the backbox insert). The purpose of the picture to the left is to easily identify what GI circuits pass through what connections. This will aid in attempting to check the continuity of your rework, whether only replacing just one of the header connectors or both. 

Please note that the wiring color codes for J6 in the pic are not the incoming wire colors. The wiring codes in the pic are illustrated this way to determine where the GI circuits disperse throughout the board. The game's schematics in the manual include this information too.
 

Keep in mind that discrete GI relay boards were still used during this time period. Dependent on the game, there may be one to three discrete GI relay boards used. Again, since single-sided circuit boards were used for the GI relay boards, cracked solder joints where the relay is soldered to the board is possible in addition to the header pins.
 

======Repairing the General Illumination Input Connector / Wiring======
[[File:WMS_Sys11_Butterfly_GI.jpg|thumb|300px|left|General Illumination input connector with looped (butterfly) wiring]]
[[File:Sys11 Interconnect GI Connection.jpg|thumb|300px|right|One method for repairing the GI input connector]]
From the factory, only 4 wires total were connected to the GI power and return input connector, which is located on the right hand side of the interconnect board. With only 4 discrete connections per wire from the transformer, 8 wires are needed to connect to the interconnect board. The top 4 wires are yellow and the lower 4 wires are yellow with a white trace. To increase 2 wire connections to 4 wire connections, the wires connect to the IDC connector via one connector pin, pass through that connector pin, and loop back to another connector pin. In doing this, the life expectancy of the connector and the header pins on the interconnect board are reduced (too much current for these connections to maintain over their lifespan). The end result is typically burnt connector pins, housings, headers, and in some cases, the interconnect board too.

To resolve the burnt connection issue, the header pins on the interconnect board should be replaced with new ones. Preferably 7A higher current rated header pins. As for the harness side, the housing should be replaced too, and Molex Trifurcon crimp pins used within the housing. To compensate for the extra wires needed, each of the input wires will need a "Y" junction soldered in place. To do so, take a small piece of wire approximately 4" - 5" long. In the middle of the small piece of wire, carefully strip the insulation, leaving about 1/4" of exposed wire. Place a piece of heatshrink on the single incoming wire. Then, bend the small piece of wire at its center where the insulation is stripped, until both ends leads are nearly parallel with one another. Take the incoming wire, and solder it to the exposed wire in the center. The end result will look like a rudimentary "Y". Pull the heatshrink over the junction, and that's it. This needs to be done for the remaining 3 wires.

In addition to the wire modifications, you can also do a board modification. The J6 connector on the right side can be burned to a crisp. Often lifting pads under the printheader. To repair this you can add a jumper wire to the top 4 traces, connecting pin 1-2-3-4 together. This can also be done for the bottom 2 traces, connecting pin 6-8 together, but you are still missing pins 5 and 7 to be connected to 6 and 8. Turn the board over and solder a jumper over pins 5 thru 8. The same can be done for pins 1 thru 4. Now you have the best possible connection.
 
<center>
<gallery widths=300px>
file:Bally_interconnect_board_Dr_Dude_1.jpg|Dr Dude Interconnect Board with Modification
file:Bally_interconnect_board_Dr_Dude_2.jpg|Dr Dude Interconnect Board modification details (front)
file:Bally_interconnect_board_Dr_Dude_3.jpg|Dr Dude Interconnect Board modification details (back)
</gallery>
</center>
 

====Controlled Lamp Issues====
=====Lamp Columns or Rows from n to 8 Inoperative=====
[[Image:BrokenSIPResistorLampMatrixColumn.jpg ‎|300px|thumb|left|A broken SIP resistor, causing lamp matrix columns 5, 6, 7 and 8 to fail.]]
[[Image:BrokenSIPResistor.jpg ‎|300px|thumb|right|The same broken SIP resistor after removal.]] 
 

=====Lamp Sockets=====
Failed lamp sockets are not very common with System 9-11c games. If a specific lamp will not illuminate, spinning the lamp socket canister or solder tab can resolve the issue in some cases. One thing to keep in mind is that all controlled lamp sockets have a diode soldered to two of the lamp socket tabs. Due to this, the legs of the diode can get pressed against other leads on the lamp socket resulting in an electrical short. The end result may be a lamp which shines more brightly than other lamps in the same column or row, or a whole lamp column or row will illuminate dimly when they shouldn't be lit at all. The resolution is to inspect all associated lamps in the column or row, and look for solder tabs or diode legs touching where they should not be. 

=====Lamp Boards=====
Starting with Pinbot, Williams introduced lamp boards. Lamp boards were used in areas where lamp inserts were positioned too closely together, and it did not make logical sense (or it was not physically possible) to use individual lamp sockets. With subsequent games, lamp boards were used whenever lamp inserts were "nested" in groups. This trend was presumedly done to save on assembly and production costs. One benefit of lamp boards is that bulb replacemnt became easier in most cases. A simple turn of the twist lamp socket (WMS # 24-8767), and the 555 bulb could be removed. 

[[File:WMS Sys1WMS Sys11 Early Lamp Board.jpg|300px|thumb|left|Early direct solder lamp board as seen on Pinbot - the large color matrix below the top and right colored targets]] 
The first generations of lamp boards had the lamp column and row wires soldered directly to the board. On one hand, this is beneficial, because there is one less mechanical connection used in the lamp circuits. On the other hand, it makes it more difficult to remove the lamp boards completely from the game to clean and / or service. On the plus side, very little goes wrong with the direct wired lamp boards.
 

[[File:PCBMountLampDivot.jpg|300px|thumb|left|"Divots" in the connection pad of a "twist in" lamp.]] 
Two things that can fail are individual lamp circuit diodes or the solder pads can develop "divots", where the twist sockets make physical contact with the board. To overcome the divots, simply add a little solder, and carefully reflow the solder pads. Make certain not to apply too much heat...just enough to evenly flow the solder.
 

[[File:WPCPCBLampBoardHeaders.jpg|300px|thumb|left|The solder on these header pins has been reflowed nicely.]] 
With Fire!, Williams started using lamp boards with .156" header connections for the lamp column and row lines. This allowed for easy removal and service of the lamp boards. However, it introduced some new problems. Because the lamp boards used were single-sided, (this was presumably a cost analysis decision), the .156" header pins can develop cold solder joints and crack due to vibration. The problem can easily be rectified by removing the old solder from the header pins, and applying fresh, new solder. This style of lamp board is susceptible to the same issues (bad diodes and divots) as mentioned in the direct wired lamp boards section above.
 

===== Adjacent Columns or Rows Lighting Simultaneously =====
[[Image:WilliamsS11ShortedLampColumnDrives.jpg|300px|thumb|left|Column drive transistor tabs touching, shorted together. Here, lamp columns 3 and 4 would light at the same time.]] 
A problem seen fairly often is the tabs of either column drives or row returns touching, and therefore shorted and causing more than one column (in the picture at left) or row to light at the same time. If you have this issue, it's easy to quickly examine the column drive and row return transistors.
 

===== Lamp Matrix Row and Column Testing =====
The CPU logic for the lamp matrix can be tested by connecting a spare lamp using a jumper wire. The following sections show the separate procedures for testing the lamp matrix columns and rows. The example is on a Sys11A PinBot, but applies to all Sys11 CPU boards.
 

'''Testing the lamp matrix columns:'''

[[Image:lamp_matrix_test_sys11a_columns.jpg|600px|thumb|left|Jumper connection for testing lamp matrix columns.]]
 

Use the following procedure to test the TIP42 transistors that drive the lamp matrix columns. Note that a diode is not needed for these tests since it's function is to prevent interaction between the lamps in the matrix. In this test we are only connecting a single lamp at a time.

#Remove the backglass and open the insert to get access to CPU board connectors 1J6 (row) and 1J7 (column).
#Unplug connectors 1J6 and 1J7 (lower right corner of CPU board)
#Turn the game on and go to the "All Lamps" test in the Test/Diagnostic Menu. This is done by opening the coin door an pressing: MANUAL-DOWN, ADVANCE, AUTO-UP, ADVANCE x 2
#Clip one end of the test jumper to 1J6 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to 1J7 pin 1, the rightmost pin on the connector
#The test lamp should flash to indicate that the column driver is working.
#Repeat the test for the pins 2 through 9 on 1J7. There is no pin 5 as it is the key.

If a column doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test.

The following table shows the lamp number and driving transistor for each of the column pins.
{| class="wikitable"
!   Pin   
!Wire Colors
!Lamp number
!Transistor number
|-
|<center>1J7-1</center> || <center>Yel-Brn</center> || <center>1</center> || <center>Q66</center>
|-
|<center>1J7-2</center> || <center>Yel-Red</center> || <center>9</center> || <center>Q64</center>
|-
|<center>1J7-3</center> || <center>Yel-Orn</center> || <center>17</center> || <center>Q62</center>
|-
|<center>1J7-4</center> || <center>Yel-Blk</center> || <center>25</center> || <center>Q60</center>
|-
|<center>1J7-5</center> || <center>Key Pin</center> || <center> </center> || <center> </center>
|-
|<center>1J7-6</center> || <center>Yel-Brn</center> || <center>33</center> || <center>Q58</center>
|-
|<center>1J7-7</center> || <center>Yel-Blu</center> || <center>41</center> || <center>Q56</center>
|-
|<center>1J7-8</center> || <center>Yel-Vio</center> || <center>49</center> || <center>Q54</center>
|-
|<center>1J7-9</center> || <center>Yel-Gry</center> || <center>57</center> || <center>Q52</center>
|}

'''Testing the lamp matrix rows:'''
[[Image:lamp_matrix_test_sys11a_rows.jpg|600px|thumb|left|Jumper connection for testing lamp matrix rows.]]
 

Use the following procedure to test the TIP102/122 transistors that drive the lamp matrix rows.

#Remove the backglass and open the insert to get access to CPU board connectors 1J6 (row) and 1J7 (column).
#Unplug connectors 1J6 and 1J7 (lower right corner of CPU board)
#Turn the game on and go to the "All Lamps" test in the Test/Diagnostic Menu. This is done by opening the coin door an pressing: MANUAL-DOWN, ADVANCE, AUTO-UP, ADVANCE x 2
#Clip one end of the test jumper to 1J7 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to 1J6 pin 1, the rightmost pin on the connector
#The test lamp should flash to indicate that the column driver is working.
#Repeat the test for the pins 2 through 9 on 1J6. There is no pin 4 as it is the key.

If a row doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test. The following table shows the lamp number and driving transistor for each of the row pins.

{| class="wikitable"
!   Pin   
!Wire Colors
!Lamp number
!Transistor number
|-
|<center>1J6-1</center> || <center>Red-Brn</center> || <center>1</center> || <center>Q80</center>
|-
|<center>1J6-2</center> || <center>Red-Blk</center> || <center>2</center> || <center>Q81</center>
|-
|<center>1J6-3</center> || <center>Red-Orn</center> || <center>3</center> || <center>Q82</center>
|-
|<center>1J6-4</center> || <center>Key Pin</center> || <center> </center> || <center> </center>
|-
|<center>1J6-5</center> || <center>Red-Yel</center> || <center>4</center> || <center>Q83</center>
|-
|<center>1J6-6</center> || <center>Red-Grn</center> || <center>5</center> || <center>Q84</center>
|-
|<center>1J6-7</center> || <center>Red-Blu</center> || <center>6</center> || <center>Q85</center>
|-
|<center>1J6-8</center> || <center>Red-Vio</center> || <center>7</center> || <center>Q86</center>
|-
|<center>1J6-9</center> || <center>Red-Gry</center> || <center>8</center> || <center>Q87</center>
|}

=====Using MOSFETs in the Lamp Matrix Circuitry=====
Procedure by Marco Albus 
The original Williams (and Data East) lamp matrix circuitry dissipates a lot of heat through the 27 ohm current limiting resistors. Often, this part of the circuit board is badly heat damaged. Using modern MOSFETs (IRF9530, IRF9Z34N or FQP17P06), the heat (and power consumption) can be reduced substantially.

Once MOSFETs are substituted for the TIPs in the lamp driver circuit, it is possible to replace the 27 ohm resistors with simple jumpers or even leave the 27 ohm resistors in place if they are in good shape as the low resistance will have a negligible effect on the operation of the MOSFET. However, the problem with either of these is that the MOSFETs are driven by 18 VDC Source to Gate voltage which is dangerously close to the absolute maximum rating of the IRF9530 and IRF9Z34 of 20 VDC (this also holds true for Data East MPUs). The FQP17P06 has a higher Vgs rating (25VDC) than either the IRF9530 or IRF9Z34N - but you are still driving the part at over 70% of its absolute maximum. Typical uses for these MOSFETs drive them by about 10 VDC Source to Gate voltage (or -10V for P-Channel MOSFET's used here).

[[File:DEMOSFETSchematic.jpg|200px|left|thumb|Typical "Zero Ohm Jumper" implemenation (left), "Voltage Divider" implementation on right. Image courtesy of Marco Albus.]]
The schematics shown at left compare the widely used "Zero Ohm Jumper" implemenation with the "Voltage Divider" implementation that uses two 1K, 1/4 watt resistors to divide the source 18 VDC in half. Doing so drives the MOSFET with a 9 VDC Vgs. 

======MOSFETs Installed in a System 9 MPU Board======
[[File:WMS Sys9 Lamp Column FET Front.jpg|300px|left|thumb|1K resistors and IRF9Z34N FETs installed on the component side of the board.]]
[[File:WMS Sys9 Lamp Column FET Back.jpg|300px|right|thumb|1K resistors installed on the solder side of the board.]]
Parts Required 
*8 P-Channel MOSFETs (IRF9530, IRF9Z34N or FQP17P06)
*16 1K Ohm 1/4 Watt resistors

Procedure 
*Remove the TIP-42 transistors Q23-30
*Remove the 27 Ohm resistors R101, 103, 105, 107, 109, 111, 113, 115
*Remove the 2.2K ohm resistor network SR5
*In place of the 27 Ohm resistors, install 1K Ohm resistors
*In place of the TIP 42 transistors, install the P-Channel MOSFETs, oriented the same as the TIP-42s were oriented
*On the solder side of the board, install eight 1K Ohm resistors between the MOSFET gate and the 18VDC source.
 

======MOSFETs Installed in a System 11 MPU Board======
[[File:WMS Sys11 Lamp FETs Front.jpg|300px|left|thumb|1K resistors installed on the component side of the board.]]
[[File:WMS Sys11 Lamp FETs Back.jpg|300px|right|thumb|1K resistors installed on the solder side of the board.]]
Parts Required 
*8 P-Channel MOSFETs (IRF9530, IRF9Z34N or FQP17P06)
*16 1K Ohm 1/4 Watt resistors

Procedure 
*Remove the TIP-42 transistors Q52, 54, 56, 58, 60, 62, 64, 66
*Remove the 27 Ohm resistors R82-89
*Remove the 2.2K ohm resistor network SR16
*In place of the 27 Ohm resistors, install 1K Ohm resistors
*In place of the TIP 42 transistors, install the P-Channel MOSFETs, oriented the same as the TIP-42s were oriented
*On the solder side of the board, install eight 1K Ohm resistors between the MOSFET gate and the 18VDC source.
 

[[File:System11_mosfet.jpg|300px|left|thumb|A very clean alternate implementation with resistors on the component side. ''Image courtesy of PinSider DumbAss''.]] 
Shown at left is a very clean installation of all parts on the component side of the board. Note that the 1K resistors are situated such that the "body" of the resistor passes between the MOSFETs instead of the legs, thereby eliminating the possibility of a short.
 

===Switch problems===

====Diode and Switch Matrix Wiring Orientation on a Microswitch====
[[File:Submicro Switch Wiing.jpg|300px|left|thumb|Typical wiring for any Microswitch]]
First and foremost, all switches located in the switch matrix MUST have a diode. Secondly, the diode has to be installed in the correct orientation. If a diode is installed "backwards", the end result my be that all of the switches in that particular row get triggered or even stranger issues occur. Finally, the diode legs must not be connected to any of the other wires or terminals of the switch, or the switch will funk up the switch matrix.

Here is the correct orientation for the wiring and the diode on a microswitch. The white wire w/ trace and non-banded side of diode is connected to NC terminal. The banded side of diode is connected to common terminal. Finally, the green wire w/ trace is connected to NO terminal.

 

====Switch Columns or Rows from n to 8 Inoperative====
[[Image:BrokenSIPResistorSwitchMatrixColumn.jpg ‎|300px|thumb|left|A broken SIP resistor, causing switch matrix columns 5, 6, 7 and 8 to fail.]] 
 

====Switch Matrix Row and Column Testing====

The CPU logic for the switch matrix can be tested by simulating switch closures using a jumper wire on both System 9 and System 11 (all revision levels) MPUs.

[[Image:WMSSystem9SwitchMatrixTesting.jpg|300px|thumb|left|Testing the System 9 switch matrix, but jumpering from pins on 1J8 to pins on 1J10.]] 
As seen at left, testing the switch matrix rows and columns on a System 9 MPU is identical to testing on a System 11 MPU except for which connectors to use. The switch columns on the System 9 MPU at 1J8 are numbered right to left. The switch rows at 1J10 are numbered left to right. 1J9 is available (sometimes not stuffed) for opto switch processing, although this feature may never been used.

The System 9 switch matrix operates on 5VDC. The switch columns at 1J8 are "strobed" by being pulled to ground successively by the 6821 PIA. The switch columns are normally pulled high via a pull-up resistor. If the switch at the intersection of the column and row is closed, when the column is strobed, the row will be pulled low too. In this way, the processor knows which column it strobed, and which rows return that strobe.
 

The following sections show the separate procedures for testing the system 11 switch matrix columns and rows. The example is on a Sys11A PinBot, but applies to all Sys11 CPU boards.

'''Testing the switch matrix columns:'''

[[Image:Sys11_switch_matrix_test_col.jpg|600px|thumb|left|Jumper connection for testing switch matrix columns. This picture shows a diode which is not necessary for this test.]]
 

#Remove the backglass and open the insert to get access to CPU board connectors 1J8 (column) and 1J10 (row).
#Turn the game on and go to the "Switch Edges" test in the Test/Diagnostic Menu. This is done by opening the coin door an pressing: MANUAL-DOWN, ADVANCE, AUTO-UP, ADVANCE x 6
#Unplug connectors 1J8 and 1J10
#Clip one end of the test jumper to 1J10 pin 9, the leftmost pin on the connector
#Touch the other end of the jumper to 1J8 pin 1, the rightmost pin on the connector
#The display should report that switch 1 was actuated. The test may report the switch name, refer to the switch matrix table in the manual to correlate the name to the switch number.
#Move the jumper to 1J8 pin 2 and check the reported switch by comparing to row 1 in the switch matrix table
#Continue to test the rest of the pins on 1J8. There is no pin 6 as it is the key.

The following table shows the switch number that should be reported for each of the column pins.
{| class="wikitable"
!   Pin   
! Wire Colors 
! Switch number 
|-
|<center>1J8-1</center> || <center>Grn-Brn</center> || <center>1</center>
|-
|<center>1J8-2</center> || <center>Grn-Red</center> || <center>9</center>
|-
|<center>1J8-3</center> || <center>Grn-Orn</center> || <center>17</center>
|-
|<center>1J8-4</center> || <center>Grn-Yel</center> || <center>25</center>
|-
|<center>1J8-5</center> || <center>Grn-Blk</center> || <center>33</center>
|-
|<center>1J8-6</center> || <center>Key Pin</center> || <center></center>
|-
|<center>1J8-7</center> || <center>Grn-Blu</center> || <center>41</center>
|-
|<center>1J8-8</center> || <center>Grn-Vio</center> || <center>49</center>
|-
|<center>1J8-9</center> || <center>Grn-Gry</center> || <center>57</center>
|}

'''Testing the switch matrix rows:'''
[[Image:Sys11_switch_matrix_test_row.jpg|600px|thumb|left|Jumper connection for testing switch matrix rows. This picture shows a diode which is not necessary for this test.]]
 

#Remove the backglass and open the insert to get access to CPU board connectors 1J8 (column) and 1J10 (row).
#Turn the game on and go to the "Switch Edges" test in the Test/Diagnostic Menu. This is done by opening the coin door an pressing: MANUAL-DOWN, ADVANCE, AUTO-UP, ADVANCE x 6
#Unplug connectors 1J8 and 1J10
#Clip one end of the test jumper to 1J8 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to 1J10 pin 1, the rightmost pin on the connector
#The display should report that switch 1 was actuated
#Move the jumper to 1J10 pin 2 and check the reported switch by comparing to column 1 in the switch matrix table
#Continue to test the rest of the pins on 1J10. There is no pin 4 as it is the key.

The following table shows the switch number that should be reported for each of the row pins.

{| class="wikitable"
!   Pin   
!Wire Colors
!Switch number
|-
|<center>1J10-9</center> || <center>Wht-Brn</center> || <center>1</center>
|-
|<center>1J10-8</center> || <center>Wht-Red</center> || <center>2</center>
|-
|<center>1J10-7</center> || <center>Wht-Orn</center> || <center>3</center>
|-
|<center>1J10-6</center> || <center>Wht-Yel</center> || <center>4</center>
|-
|<center>1J10-5</center> || <center>Wht-Blk</center> || <center>5</center>
|-
|<center>1J10-4</center> || <center>Key Pin</center> || <center> </center>
|-
|<center>1J10-3</center> || <center>Wht-Blu</center> || <center>6</center>
|-
|<center>1J10-2</center> || <center>Wht-Vio</center> || <center>7</center>
|-
|<center>1J10-1</center> || <center>Wht-Gry</center> || <center>8</center>
|}

====Shorted or non-working switch column====

One or more failed switch columns can be caused by a failed column drive transistor (Q42 through Q49, all 2N4401s) or a failed 1K SIP resistor pack at SRC6.

The column drive transistor part was changed with the system 11B MPU. System 9 to 11A MPUs use 2N3904 transistors at location Q42 to Q49 with 1.5Kohm inline resistors (R71 through R78). These column drive transistors fail quite often as these MPUs age. These 2N3904 transistors can be replaced with 2N4401s.

When System 11B was introduced, the switch column drives were changed to 2N5550s with 470 ohm inline resistors. The more commonly found, and beefier 2N5551, is a good substitute for the 2N5550. Before replacing the transistor, be sure which kind the board uses. Some early system 11B MPUs were stuffed with 2N3904s despite the schematics indicating otherwise.

A broken SIP can also cause a switch column not to work. This usually happens with System 11 and 11A CPUs. With 11B WMS also changed the switch section layout and eliminated most of the SIPs. The likely candidates are SRC6 and SR11. In the case of SRC6, measure resistance between pin 1 and 2 to 9. If it's broken it's usually open after pin 3 or 4. This is a bussed 1K SIP with additional 470pfd capacitors connected to ground and practically NLA. Fortunately the caps are not needed because they are also mounted on the board so it can be replaced with a standard 9-8 1K SIP. Pin 10 which is the common ground for the caps is not used here. SR11 is a standard bussed 560 ohm 10-9 SIP. Here you measure resistance between pin 1 and pin 2 to 10. Be aware that two types of SIPs are used on the board: bussed and isolated. If you suspect a different SIP has failed check the schematics for the pin layout.

[[File:WMS-Brokensip.jpg|300px|thumb|left|A broken resistor SIP.]] 
Pictured at left is a broken resistor package similar to SRC6 but out of a System 11 master display. As can be seen, the part may look solid to the naked eye, but it's actually fractured.
 

====Ground Row Shorts====
[[File:WMSSystem11CrackedSR11.jpg|300px|thumb|left|Note the fracture in the SIP at SR11. The fracture became apparent only after desoldering the part.]] 
A possible cause for one or more ground row shorts (indicated by the game software on the score display during switch test) is a fractured resistor SIP at SR11 (a 560 ohm 10-pin bussed resistor network). SR11 is a pull-up resistor that is connected between each switch row return and 5VDC. If the return is not pulled up, that return will look like a low signal continuously, which the MPU interprets as a row ground short. Visual inspection of the SIP might or might not identify the cause of the problem. A better test is to remove the switch row return connector (J10) and probe each pin with a logic probe. The logic probe should indicate "high" for every pin.

Specific to the board pictured at left, a logic probe indicated that J10 pins 1, 2, and 3 were all high but the remaining pins had no signal at all. The fracture can easily be seen between pins 5 and 6 of the SIP (pin 4 isn't used) meaning that pins 6 through 10 were not connected to 5VDC and therefore not pulling the switch row return to logic high. Hence, the MPU declared a row ground short for rows 1 through 5. Note that the actual fracture can rarely be seen prior to attempted removal of the resistor network from the MPU board.
 

==== 4N25 Opto Couplers in the Switch Matrix====

[[File:4N25System11InterconnectBoard.jpg‎|300px|thumb|left|Three 4N25 Opto Couplers on a Williams System 11 Interconnect Board]]
System 11 games that include an Interconnect Board may use 4N25 Opto Couplers to detect power being applied to the flippers or to detect 28VDC being applied to the A/C relay (as in Rollergames). Pre-Fliptronic WPC games that use the -1 power/driver board also use 4N25 Opto Couplers.

These opto couplers are connected to the game switch matrix. Detecting these switches is most often used for lane change and for entering HSTD initials. If one of these functions no longer works, the 4N25 opto couplers should be considered suspect.
 

Fortunately, testing an opto coupler is simple using the diode test function provided by most DMMs. Set the DMM to diode test, compare results against those pictured below.

<center>
<gallery widths=300px heights=300px perrow=4 caption="Testing a 4N25 Opto Coupler">
File:4N25Internal.jpg|<center>The internal schematic of the 4N25. Pins 1 and 2 connect to an internal diode (LED). Pins 4 thru 6 connect to a PNP photo transistor.</center>
File:4N25Test3.jpg‎|<center>Testing the diode connected to pins 1 and 2</center>
File:4N25Test2.jpg‎|<center>Testing part of the photo transistor. Black on pin 5, red on pin 6</center>
File:4N25Test1.jpg‎|<center>Testing part of the photo transistor. Black on pin 4, red on pin 6</center>
</gallery>
</center>
 

====Opto Switches Not Registering with a Rottendog MPU / Driver Board Installed====
[[File:R-D_11C_Opto_Before.jpg|300px|thumb|left|Older Style Rottendog MPU Board]]
[[File:R-D_11C_Opto_After.jpg|300px|right|thumb|Modified Older Style Rottendog MPU Board]] 
If the opto switches are not registering at all in a game, and a Rottendog MPU board is being used, suspect that it is an older style board. This board can easily be upgraded though. U2 will have to be switched from a 74HCT240 to a 74HC240 chip, and RA5 will have to be changed from a 9-pin 4.7K ohm bussed SIP resistor network to a 9-pin 560 ohm bussed SIP resistor network.
 

===Display problems===
System 9/11 High Voltage Section Repair 
WARNING: This circuit uses high voltages. Don't continue, unless you are confident in your diagnostic abilities.
====High Voltage Issues With the Power Supply====
=====Check Voltages=====
If all displays are blank, your high voltage (HV) section may not be working.
On the Power Supply Board, use a DMM set to DC volts with the - lead grounded, probe the following connector
pins to determine if the HV section needs repair. If the display fuse, F1 is blowing,
you should remove the applicable display connector (with power off) before testing the voltages. Note that these are "loaded" voltages. If you are testing on the bench, or without displays connected, your measurements may vary.
 
If you have Power Supply D-11883 or D-12246: 
3J2 pin 1 = -100 volts DC 
3J2 pin 3 = +100 volts DC 
If you have Power Supply D-8345-xxx: 
3J5 pin 3 = -100 volts DC 
3J5 pin 4 = +100 volts DC 
If the test points are more than about 5 volts out of spec, then your HV section may
be malfunctioning (if you or a previous owner replaced Z2/Z4 with 1N4763A diodes to purposely reduce the display voltage, test readings in the 90's range would be normal). 

Check the table below for a solution.

=====Troubleshooting table=====
{| class="wikitable"
! '''Symptom'''
! '''Possible Cause'''
! '''Replacement'''
|-
| 0V ON BOTH +100/-100 lines
| Check F1
| 1/4 Amp SB
|-
| rowspan=5 | 0V on +100V line
| Open Diode D3
| 1N4004
|-
| Open Q2
| 2N5401
|-
| Shorted Zeners ZR1, ZR2
| 1N4730A and 1N4763A
|-
| Open Q1
| MJE340
|-
| Open R1
| 39k ohm, at least 1 watt
|-
| rowspan=5 | 0V on -100V line
| Open Diode D4
| 1N4004
|-
| Open Q4
| 2N5551
|-
| Shorted Zeners ZR3, ZR4
| 1N4730A and 1N4763A
|-
| Open Q3
| MJE350
|-
| Open R4
| 39k ohm, at least 1 watt
|-
| rowspan=4 | F1 1/4 Amp Fuse Blows
| Bad Capacitor at C1 and C3
| 100uF,150V
|-
| Shorted Display
| Display Glass*
|-
| Shorted UDN7180
| UDN7180*
|-
| Shorted UDN6118
| UDN6118*
|-
| +118V on +100V line
| Shorted Q1
| MJE340
|-
| -118V on -100V line
| Shorted Q2
| MJE350
|-
| colspan=3 | * ''located on display board''
|}

'''Displays Test With no Shorts'''
Once the displays are tested and shorts are eliminated, we can proceed with the HV section repair.

'''Replacing the components in the HV Section'''
Since there are not that many components, if you are having problems isolating the fault, a quick solution is to replace all the components in the HV section. If only one side (+ or -) is failing, it is possible to rebuild only the failing side. Check the parts section of the wiki to find suppliers, and get the replacement parts for one or both failing sides:

{| class="wikitable"
! '''Part'''
! '''+Side Part'''
! '''-Side Part'''
! '''+,-Location'''
|-
| Transistor
| MJE340 (or MJE15030)
| MJE350 (or MJE15031)
| Q1,Q3
|-
| Transistor
| 2N5401
| 2N5551
| Q2,Q4
|-
| Zener diode
| 1N4730A
| 1N4730A
| Z1,Z3
|-
| Zener diode
| 1N4763A**
| 1N4763A**
| Z2,Z4
|-
| Resistor
| 39k Ohm,1W
| 39k Ohm,1W
| R1,R4
|-
| Resistor
| 680 Ohm,1/4W
| 680 Ohm,1/4W
| R2,R5
|-
| Resistor
| 330k Ohm,1/2W
| 330k Ohm,1/2W
| R3,R6
|-
| Capacitor
| 0.1uF,250V metal polyester
| 0.1uF,250V metal polyester
| C2,C4
|-
| Capacitor
| 100uF,150V
| 100uF,150V
| C1,C3
|-
| colspan=4 | ** ''This is a 91V Zener to reduce the voltage to prolong display life''
|}

'''Remove and replace HV components'''

* Clip the old components from the board (make sure you have new ones first).
* Use one of the desoldering methods to remove solder from the holes.
* Stuff board with new components.
* Check for correct orientation on transistors, diodes and the large capacitor if you replace it.
* Leave a little space under components for air flow.
* Bend leads on components so they won't fall out when board is inverted for soldering.
* Double check that all the correct parts are in the correct places and properly oriented.
* Solder the parts to the board
* Clip excess off leads
[[File:System11PSPartIdentification.jpg|500px|thumb|left|A visual depiction of the parts in a System 11 high voltage section. Note that the legs of the MJE15030/MJE51031 are crossed as this power supply originally used OEM parts SDS-201 and SDS-202]]
 

=====Note on installation of MJE340/MJE350 replacement transistors=====
The MJE340/MJE350 is the heat-sinked transistor. On most Williams boards, this transistor pin configuration is not the same as the original part. It will need to be installed vertically with heat sink attached to the transistor only. The transistor will sit at about a 45 degree angle so the legs can be lined up to fit in the correct holes.

Check your board and insure correct orientation before soldering in place. Late versions of the System 11 series boards were designed to use the pin configuration of the MJE340/MJE350 transistors.

Do not mount vertically if the power supply is designed to use the pin configurations of the newer transistors!

[[Image:MJEInstall.png]]

=====Note on installation of MJE15030/MJE15031 replacement transistors=====
[[File:WMSSys11MJELegsCrossed.jpg|300px|left|thumb|High Voltage section with MJE15031 installed. Note the crossed legs on the left transistor.]]
[[File:WMS Sys11 PS Alt HV Transistor Pads.JPG|right|thumb|300px|Power supply with pads for both styles of HV transistors]]
The MJE15030/MJE15031 are rated for higher power and can be used instead of the MJE340/MJE350 (the MJE340/MJE350 are well within design specifications and are suitable replacements at 1/3 the cost of the MJE15030/MJE15031).

The MJE15030/MJE15031 pin configuration has the Base and Emitter reversed as compared to the MJE340/MJE350. In the image at left, the left transistor (MJE15031) shows one method of crossing the legs safely. The transistor's two left legs are shifted right on position. The third leg is then jumpered to the boards left through hole position. If you prefer not to cross legs, this transistor can also be mounted vertically, but this transistor would be facing the opposite direction as compared to the MJE340/MJE350 pictured above. 

There are some power supplies which have pads for both the SDS-201/SDS-202 or the MJE15030/MJE15031 style of transistors. In the pic to the right, the MJE15030/MJE15031 transistors are installed from the factory, but there are solder pads just below for installation of the SDS-201/SDS-202 transistors. If installing ME15030/MJE15031, the upper pads are used, and no leg crossing is required.
 

Ready to test 
To test the rebuilt power supply, return to the "Check Voltages" section of this guide. 
 
'''Other Resources''' 
The System 9-11 HV section of the PSU is very similar in design to the earlier System 3-7. So it will be worth reading through the [[Williams_System_3_-_7#Power_Supply_Issues|Sys 3-7 PSU Problems]] section entitled '''+/-100v Display HV Section of PSU''', for more detail. It also provides links to source complete HV rebuild kits which will normally cost under $10 shipped.

====Display Panel Problems====
=====Segment Identification=====
[[File:SegmentLetters.jpg|300px|left|thumb|Alphanumeric and Numeric Segment Identification.]]
 

=====Display Will Not Light=====
[[File:PlasmaBallTest.jpg|300px|left|thumb|Testing a high voltage plasma display with an inexpensive plasma ball]] 
If power to the display is correct, and the display was moved to a known working display panel position (if possible), it is possible that the display has outgassed. A plasma ball can be used to determine if a display glass is outgassed. 
[[File:YT.png]] A Youtube video demonstrating the use of an inexpensive plasma ball for this purpose can be found [https://youtube.com/shorts/GGftl3S_OWg?si=T5Cdzyovtar6_Han here]. 

=====Segments Light "In Sympathy" With Other Segments=====
[[File:ShortedSegments.jpg|300px|left|thumb|In this image, segment "b" and segment "k" light simultaneously, even though only one segment should be lit. The last two characters illustrate the issue clearly. Image courtesy of PinSider Pinball50.]] 
Internal shorts within a display glass can cause segments to light "in sympathy" with other segments. That is, segment "b" and segment "k", for example, will both light, when only one of the segments should be lit. Segment "b" will light whenever segment "k" is lit and segment "k" will light whenever segment "b" is lit. This is caused by an internal short within the glass. The short can be confirmed by removing the leads of the associated segments from the PCB and measuring resistance between them. The resistance should be infinite, or open.

In this case, there is no way to repair the glass and it should be replaced.
 

=====Commas stuck on (Players 1&2 or 3&4)=====
System 9: Check IC36 on the MPU (6821 PIA)

Pin 16 = Players 1 & 2
Pin 17 = Players 3 & 4

With the game in attract mode, check these pins with a logic probe. They should go low each time the displays turn off. if they stay high, the PIA is likely bad and will need to be replaced.

=====Display Fuse F1 Blows=====
Testing the UDN Chips 
If the display fuse is blowing, you should check the display board for shorts before connecting
a new or rebuilt power supply to the display board, as a shorted display or chip can damage a good power
supply. Remove the display board from the system. The display characters are driven by the two types
of UDN chips, the UDN7180 & UDN6118 (or UDN6184). Locate these chips (there are several)
on the board and test them with your DMM set to diode check. Clip your + (RED)
lead to the ground trace of the board. Probe the UDN chips as shown in the diagram.
If any shorts are read in the tested pins, the display should not be connected to the power
supply until the shorts are corrected.
[[Image:UDNReading.png|left]]
 

 Shorts Are Found in UDN Chip Test 
If a short reading is found in the tested pins (don't test the pins labeled 'dont care'), the UDN
chip should carefully be desoldered and removed from the board. Take care to preserve this chip,
as they are nearly impossible to find and expensive to replace. Now install an IC socket in its place.
Repeat the test with no chip installed. If the short is gone, then the UDN chip needs to be replaced.
If the short remains, then the display glass needs to be replaced.

=====Replacing Display Glass=====
[[File:WMS 7Digit glass change1.JPG|300px|left|thumb|Replacement glass installed with glass nipple in proper location]]
[[File:WMS 7Digit glass change2.JPG|300px|right|thumb|Replacement glass installed after circuit board was drilled to allow for glass nipple in different location]]
All plasma displays have a finite life expectancy. Display glass replacements were and are offered in several configurations. The differences in these configurations are mainly the placement or lack of a display "nipple" on the back of the glass. The glass nipple is what can pose as somewhat of a problem, when replacing a display glass. Williams did place a rather large hole in the display circuit board. However, the placement of the glass nipple has changed. To overcome this issue, a hole can carefully be drilled through the circuit board to allow for the glass nipple. When drilling, drill successive holes, starting with a small drill bit first, rather than drilling one large hole. This will reduce the chances of the circuit board "splintering". 

At one time, [http://www.pinballpcb.com/Displays.html pinballpcb.com] did offer replacement displays and / or just the replacement display circuit boards. Neither of these products are available anymore.

[[File:WMS 7Digit Repair.JPG|300px|left|thumb|Replacement glass installed]] 
Original display glass was secured to its circuit board with double-sided, high tack, foam tape. If this cannot be acquired, a simple method to secure an existing or new display glass is to use silicone caulk or RTV caulk. However, in following this method, the glass must be supported on the board until the caulk cures. Wrapping the glass with rubber bands is a great way to do this. Once the caulk is cured, just cut off the rubber bands.
 

====Logic States of Display Output Signals for a Working MPU Board====
These logic states were recorded from a System 11A board. This board was running Swords of Fury code in display test mode manually paused with all characters / digits on "8". This is for games with a 4 x 7 display board.

L=LOW, H=HIGH, P=PULSE

{| class="wikitable"
!IJ3 (pin)
!Logic State
|-
| 1 || L
|-
| 2 || P
|-
| 3 || P
|-
| 4 || P
|-
| 5 || P
|-
| 6 || None (Key)
|-
| 7 || P
|-
| 8 || P
|-
| 9 || P
|-
| 10 || L
|-
| 11 || L
|-
| 12 || H
|}

{| class="wikitable"
!IJ2 (pin)
!Logic State
|-
| 1 || P
|-
| 2 || P
|-
| 3 || P
|-
| 4 || P
|-
| 5 || P
|-
| 6 || P
|-
| 7 || None (Key)
|-
| 8 || P
|-
| 9 || P
|}

{| class="wikitable"
!IJ1 (pin)
!Logic State
|-
| 1 || P
|-
| 2 || P
|-
| 3 || P
|-
| 4 || P
|-
| 5 || P
|-
| 6 || P
|-
| 7 || P
|-
| 8 || None (Key)
|-
| 9 || P
|}

{| class="wikitable"
!IJ22 (pin)
!Logic State
!IJ22 (pin)
!Logic State
|-
| 2 || L || 1 || L
|-
| 4 || L || 3 || L
|-
| 6 || L || 5 || L
|-
| 8 || L || 7 || L
|-
| 10 || L || 9 || L
|-
| 12 || L || 11 || L
|-
| 14 || L || 13 || P
|-
| 16 || L || 15 || L
|-
| 18 || L || 17 || L
|-
| 20 || P || 19 || P
|-
| 22 || P || 21 || P
|-
| 24 || P || 23 || P
|-
| 26 || P || 25 || L
|-
|}
 

===Sound problems===
====System 9 Sound Problems====

=====Jumper Settings for a newer System 9 Speech Board=====
[[File:WMS Sys9 Speech Board jumpers.JPG|300px|left|thumb|Jumpers Circled on a Comet System 9 Speech Board]] 
As mentioned above, the System 9 speech board is essentially the same as the System 6/7 speech board. However, the newer speech board has jumpers added to increase the flexibility of EPROMs used. Either 2532 or 2732 EPROMs can be used. If using 2532 EPROMs, install jumpers W2 and W4, and remove jumpers W1 and W3. If using 2732 EPROMs, install jumpers W1 and W3, and remove jumpers W2 and W4.
 

=====Missing Sound or Speech Calls=====
To start a sound test, simply press the SW2 momentary switch at the bottom of the CPU board located between connections 1J16 and 1J17. Once SW2 is pressed, the CPU will cycle through all of the sound / speech calls continuously. Each System 9 game has a chart located in the manual, which lists the speech and sound calls made during test. The benefit of the chart in the manual is that it lists the ROM where a particular call originates. If a particular sound / speech call is not heard, the associated ROM listed for that call may be bad. 

Another result of speech calls missing is possibly a bad U2 or U3 on the speech board. Both of these chips are 1458 op-amps.
 

=====Isolating the CPU Sound from the Speech Board=====
Some of the sound / speech calls originate from the CPU board, while the remaining calls originate from the speech board. If after running a game through sound test by pressing SW2, and some sounds are missing or very low in volume, a good idea is to isolate the CPU board from the speech board. All of the sounds originated on the CPU board, leave the board via the 40 pin ribbon cable, and go to the speech board for mixing. Once mixed, all of the sounds and speech are then returned to the CPU board, amplified, and sent out to the speakers.

Much like the System 6/7 sound and speech boards, the sound can be isolated from the speech board for testing purposes. The System 6/7 Type 2 sound board uses a jumper at position W1. When jumper W1 is installed, the sound board can be diagnosed without the speech board installed. The equivalent with the System 9 CPU board is jumper W10. This jumper is typically not connected. However, when it is connected, the sounds originating from the CPU board can be heard.

If the sound is being tested and the speech board is '''not''' connected, audio volume will be very low. W10 must be installed to hear full volume.

Locate jumper W10 on the CPU board. W10 is located to the right of SW2 on the board. There should be two very small wires clipped on either side of W10, as if W10 was installed and removed. Connect an alligator test lead across the short leads of W10. If the short leads are not present, a short light gauge wire or wire wrap can be tack soldered to the solder pads of W10, or use a jumper wire to connect the lower legs of C32 and R76 which are just right of W10 (see pic, below). With a jumper installed at W10, some sounds should be heard when SW2 is pressed. Sound test, via the coin door diagnostic button is likely to provide sounds for all but sound 7, which is a voice call. If no sounds are heard, further troubleshooting must be performed.

<center>
<gallery widths=350px heights=350px perrow=3 caption="Adding W10 to a System 9 CPU Board">
File:WMS Sys9 W10 Jumper.JPG|<center>Locating jumper W10</center>
File:WMS Sys9 W10 Jumped.JPG|<center>Temporarily jumpering W10</center>
File:System9JumperTemporary.jpg|<center>Alternate for jumper W10</center>
</gallery>
</center>
 

====System 11 Sound Problems====
System 11 games are known to "hum" a bit. The "hum" is caused by electromagnetic interference from the lamp matrix insinuating itself on the sound circuit. To minimize the interference, ensure all boards are screwed tightly to the backbox ground plain, with all screws installed. This improves grounding and will help minimize "hum". 

Another cause of hum could be an inconsistent +5DC volts from the power supply. An indicator of this being the cause of hum would be the game occasionally resetting as well. Replacing caps C8 and C10 on the power supply may correct this issue. 

Depending on the version of System 11 board, an 11C board or anything else (nothing, 11A, and 11B), sounds and music are handled with different specifics. With the first 3 generations of MPU boards, the sounds originate from the MPU board and the background music originates from the sound board. With the 11C board, both sounds and music are on the sound board, as the MPU no longer has a sound section populated on it. 

=====Volume POT value=====
Some System 11 games shipped with a 5K linear volume POT. Others shipped with a 10K linear volume POT. Both POT values work fine and either can be used to replace a failed volume POT.

Some System 11 games shipped with a 50 ohm resistor soldered to the volume POT. It is thought that this resistor was included so that the volume could never be turned to zero. For route games, at least some sound was thought to increase game earning potential. This resistor can be removed or jumpered around to enable turning the sound volume completely off.

=====Boot Up Diagnostic Tones for the D-11297, D-11298, and D-11581 Sound Boards=====
The D-11297, D-11298, and the D-11581 sound boards all provide diagnostic tones ("bongs") at power on. A single "bong" means that the sound board is operating properly.

Lack of a bong indicates a problem with the sound board or it's connections. The possible causes for failure are numerous, including a failed amplifier, missing or incorrect connector placement, missing or noisy (AC ripple) power for a required voltage (-12VDC), failed speakers or the connection to the speakers, etc.

If the sound board is healthy enough to perform it's own self-diagnosis, it will attempt to indicate the problem by playing a specific number of bongs, as shown in the tables below.

D-11297 & D-11298 Sound Boards
{| class="wikitable"
!"Bong" Count
!Description
|-
|<center>1</center> ||  Normal sound board boot with no problems detected.
|-
|<center>2</center> ||  U3 RAM Problem
|-
|<center>3</center> ||  U4 Sound ROM Problem
|-
|<center>4</center> ||  U19 Sound ROM Problem

|}

D-11581 Sound Board
{| class="wikitable"
!"Bong" Count
!Description
|-
|<center>1</center> ||  Normal sound board boot with no problems detected.
|-
|<center>2</center> ||  U5 RAM Problem
|-
|<center>3</center> ||  U4 Sound ROM Problem
|-
|<center>4</center> ||  U19 Sound ROM Problem
|-
|<center>5</center> ||  U20 Sound ROM Problem
|} 

=====Sound Diagnostics Via the MPU Board for Games Prior to 11C=====

Pressing the upper switch of the two switches on the side of the MPU board will test both the CVSD and DAC on the MPU board. The first sound is typically sound ROM (on the MPU) specific, and it is a test of the CVSD chip. The second sound is described as a "twing", and it is a test for the DAC. If no sounds are heard, refer to the potential issues listed above in the previous section. If one "ring" is heard, it denotes that the U23 RAM chip has failed. Two or four rings denotes that there is a problem associated with U21 ROM. Three or five rings denotes that there is a problem associated with U22 ROM.

 

=====Connecting the Speaker and Volume Connections for a System 11 MPU Board on the Bench=====
[[FILE:WMS Sys11 Speaker Volume Connection.JPG|300px|left|thumb|Speaker and Non-adjustable Volume Control Connected on a System 11 MPU Board]] 
To test the sound on a System 11 MPU on the bench, a speaker and volume control must be connected to connectors 1J15 and 1J16 respectively.

The speaker should connect to pins 2 and 3 of 1J15.

In the adjacent pic, a 470Kohm resistor was used in lieu of a volume pot. Other resistor values can be used, but 470Kohm allows the sound to be set to a comfortable audible level. Alligator clips can be used, but if the intentions are to test sound boards in the future, a resistor can be crimped into a .156" housing as shown. This resistor/connector set up can be used on all Williams sound boards from System 3 through System 11.

If using alligator clip leads to power the board, use special care as to not send +12v down the -12v line (the pins are adjacent to one another). Sending +12v down the -12v bus will most definitely destroy the 1408 DAC chip (if populated).
 

=====Sound Is Very Faint Even at Maximum Volume =====
[[Image:55536-CVSD.jpg|300px|thumb|right|Two hard to find 55536 CVSD ICs.]] 
While most techs would suspect either a TL082 or a TL084 amplifier (on a pre-DCS sound board) or a 1458 amplifier (on a System 11 MPU) as the cause of this issue, the 55516/55532/55536/55564 CVSD (Continuously Variable Slope Delta-Modulator) can also cause this issue.

Isolation to the CVSD is pretty simple.

*Place the game into sound test.
*Use an oscilloscope to probe pins 9 and 12. A scope must be used since the signals are too subtle for a logic probe to detect.
*Pin 9 is a clock signal.
*Pin 12 is a data signal.

When the game is making sounds that use the CVSD, both pin 9 and pin 12 should show "off nominal" signals. If the CVSD is working correctly, the output at pin 3 should be showing signal also. If it is not, then the CVSD has failed.
 

=====Some Sounds Lower Volume Than Others =====
[[Image:System11DACChannel.jpg|300px|thumb|left|The sound section of a System 11 MPU and the 2N3904 amplifying transistor.]] 
Another sound anomaly manifests as some sounds being more faint than others is a failure in the 1408 DAC sound lane channel. In High Speed, for example, "Sound Test" exercises both the 1408 and 55536 sound lanes. Sounds 1, 3, and 5 are all made via the 1408 DAC lane. If those sounds are faint, the issue could be the 10uf capacitor (C8), the 2N3904 transistor (Q1) that is used as a pre-amplifier, the 3.3K resistor (R7), or the 1408 DAC. Eliminating the easy possibilities first, replace the 10uf capacitor. If that doesn't fix the issue, replace the 2N3904. The 2N3904 may "diode test" as failed, but not always. If the issue still remains, replace R7. Lastly, replace the 1408 DAC (U2). An equivalent part that may be used is the DAC0808.

A video, showing the problem and resolution can be viewed [https://www.youtube.com/watch?v=G7fk3PtwvtE here].
 

[[FILE:WMS_Sys11_1408_flipped_lid.jpg|300px|thumb|left|The 1408 in the sound section of a System 11 MPU lost its top!]] 
In another instance, Pin*Bot, all of the sounds were faint, except the last two in test. This ended up being a bad 1408 DAC. The last two sounds were unaffected, because the 55516 CVSD chip handled them. With a visual inspection, the 1408 in the pic could not be determined it was bad, until it was in the midst of being desoldered from the circuit board.

 

===== Voice callouts are much softer than music/sound or missing completely =====
The sound mixing section on the System 11A and 11B MPU boards were populated with different resistor and capacitor value parts. If an 11A MPU is installed into an 11B game (F-14 into an Earthshaker for instance), it is possible that the voice callouts will be noticeably softer than the other music/sound. The following table details the difference between the two sound mixing sections ''(Thanks to Pinsider "Mneubey")''.

[[Image:System11_11n_sound.jpg|500px|thumb|left|System 11 (nothing) sound section. ''Image courtesy of PinSider "DumbAss"'']] 
  Resistors

    R21 is 12K in 11B, 15K in 11A 
    R22 is 22K in 11B, 27K in 11A 
    R19 is 56K in 11B, 27K in 11A 
    R16 is 180K in 11B, 56K in 11A 
    R17 is 270K in 11B, 220K in 11A 
    R15 is 180K in 11B, 43K in 11A 
    R20 is 12K in 11B, 27K in 11A 

  Capacitors

    C10 is 470pf in 11B, 1800pf in 11A 
    C11 is 100pf in 11B, 180pf in 11A 
    C12 is 470pf in 11B, 1200pf in 11A 
    C13 is 4700pf in 11B, 4700pf in 11A 

[[Image:System11_11b_sound.jpg|500px|thumb|left|System 11B sound section. ''Image courtesy of PinSider "DumbAss"'']]
 

===== Sound Board D-11581 Mixer Section Resistor Values =====
[[Image:D11581ResistorValues.jpg|500px|thumb|left|"Mixer" section resistor values across D-11581 sound board games. ''Data courtesy of PinSider "DumbAss"'']] 
The sound mixing section on the System 11A through 11C sound boards were populated with different resistor values. The table shown at left details the differences between the sound mixing sections for each game.

Note that the value of R13 will change also. It should be 4.99K for "Fire!" through "Police Force", and 10K for all other games.
 

=====Missing Some Music or Garbled Music with a D-11581 Sound Board and 5 Bongs=====
A sound board booting with 5 bongs indicates a failure of the U20 ROM. While U20 could, in fact, have failed, 5 bongs could also mean that the software can't access U20. In one such case where 5 bongs were heard, during music test, tests 4 and 6 would play music but the music was garbled and/or incorrect. The root cause was W10/W11 jumper settings on the sound board that didn't match the ROM size. W10/W11 should be set to the left for 27256 ROMs; to the right for 27512 ROMs.
 

=====Modifying a pre-System 11C Sound Board to use 27512 ROMs (D-11581)=====

[[Image:System11BSoundBoardW2W3.jpg‎|300px|thumb|left|D-11581 sound board jumpers W2 and W3. Note that W3 is "always IN". The solder mask over the W3 jumper trace has been removed for clarity. Normally the trace is covered by a dashed white silkscreen line.]]
[[Image:System11BSoundBoardW2W3Modified.jpg‎|300px|thumb|right|D-11581 sound board jumpers W2 and W3. W3 has been cut to enable use of 27512 ROMs.]]

Some revisions of the D-11581 sound board will not accept 27512 sound ROMs without modification. By the time that revision C was manufactured, jumpers W10 and W11 were added above U20 to enable use of larger ROMs. Prior to that, jumpers W2 and W3 were implemented, but were of little use since both jumpers tied A15 (pin 1) of each EPROM to +5VDC. Making the modification pictured at right, then installing jumper W2, enables the use of 27512 ROMs.
 

=====Jokerz specific sound issue=====
A special case of interference is present on the Jokerz game, which uses a unique stereo sound board. A deficiency in its design prevents all of the noise from being eliminated from the board. Details can be found in the original Williams service bulletin here: [http://www.ipdb.org/files/1308/Williams_1988_Jokerz_William_Service_Tip_For_Audio_Hum.pdf Jokerz service bulletin at IPDB.org]

=====Whirlwind Doesn't play Sound 7 During Test=====
This particularly annoying issue appears to have no impact during gameplay. The only manifestation is that "Sound Test", sound 7 doesn't play. The normal sound is an explosion.

This issue is caused by old game ROM versions at U26 and U27. Revision PA1 doesn't send the command to the sound subsystem to play sound 7, even though sound 7 is displayed on the alphanumeric display. Updating U26/U27 to "LA3" as can be found at www.ipdb.org will correct this issue.

[[file:YT.png]] Correct Whirlwind sounds are demonstrated in a YouTube video found [https://www.youtube.com/watch?v=fy_GXp3Bfzg here].
 

=====Sound Board Theory of Operation (D-11581)=====

[[Image:System11CSoundBoard.jpg|500px|thumb|right|D-11581 Sound Board, Completely Populated and including jumpers W10 and W11]] 

Major components of the D-11581 sound board are:

*68B09E externally clocked CPU, which is also used in all WPC MPU and pre-DCS sound boards
*68B21 Peripheral Interface Adapter, capable of running at 2Mhz
*Up to 3 ROMs. All boards can accommodate 27256 ROMs. Some later boards can be jumpered to accommodate 27512 ROMs.
*6116 RAM (2K bytes). Some later boards can be jumpered to accommodate a 6264 RAM (8K bytes)
*YM2151 sound synthesizer paired with the YM3012 DAC (outputs channel 1 and channel 2)
*55516 CVSD (continuously variable slope delta) audio encoder, which provides a 3rd audio channel
*1408 DAC (digital to analog converter), which provides a 4th audio channel
*Various 74XX ICs that perform address decoding and chip selection logic
*1458 pre-amplifiers and TDA2002 amplifiers

The D-11581 sound board shares a lot of board design and architecture of the pre-DCS sound board that was introduced with WPC games.

Power

Power requirements for the board are supplied via connector J3. The typical sound board power levels are required, 5VDC, 12VDC, -12VDC, and Ground. Three 100uf capacitors reduce noise on the power busses along with several small ceramic caps which filter high frequency noise.

Reset

The on board 68B09E is reset via the external reset signal provided by the MPU board, via connection J4, pin 18. If attempting to operate the board without the MPU board connected, the processor must be manually reset via momentarily grounding pin 37 of the 68B09E.

Clocking

The clocking signal for the board originates at the 8Mhz crystal oscillator. U16, a 74LS74 Dual D-Type FlipFlop divides the clock signal yielding both the "E" and "Q"clock signal. E and Q are phase shifted by one half clock cycle.

Chip Select Logic

Chip select is accomplished via the normal "memory mapped I/O" method, using U14 (74LS139) and U15 (74LS138).
*Chip select for all three ROMs (U4, U19, U20) is implemented by U14.
*Chip select for the RAM (U5), YM2151 (U3), and the 6821 (U12) is implemented by U15.

How sounds are produced

Sound select signals are provided via J4, a dual row .100 connector of 20 pins. These sound selects are held "normally high" via a 4.7K/470pf 10-pin bussed SIP pull-up resistor/capacitor (SR1) tied to 5VDC. These SIP resistor/capacitor parts are no longer available. A bussed 4.7K 9-pin resistor network can be used as a replacement. The capacitor feature of the original part filtered high frequency noise from the communication lines. In practice, noise doesn't impact the interface significantly enough to be of concern.

The MPU board will pull the appropriate sound select signals to ground via the 6821 PIA at Uxx. When the appropriate signals are pulled to ground, the PIA is programmed to interrupt the 68B09E processor via the FIRQ and NMI signals. The 68B09E then reads the sound select signals presented at the 6821s input port (PB0 through PB7) via the processor data bus (D0 through D7).

The processor then employs the 4 sound channels available to it, along with encoded sound files contained in the ROM images, to create the intended sounds.

====Where Do The Sounds Come From?====

The following sections can be used to ensure that all sounds are played by the Williams combined MPU and Sound Board System.

=====System 9 Games (alphabetical)=====
{| class="wikitable"
! style="text-align:left;" | Game
! style="text-align:left;" | Audio Demo Link
|-
| Comet|| [[file:YT.png]] [https://youtu.be/-2m7vKCeg2A Audio]
|-
| Sorcerer || [[file:YT.png]] [https://youtu.be/pXacwGqv5C4 Audio]
|-
| Space Shuttle                     || [[file:YT.png]] [https://youtu.be/B-gsuEw1jgU Audio]
|}

=====System 11 Games (alphabetical)=====
{| class="wikitable"
! style="text-align:left;" | Game
! style="text-align:left;" | Audio Demo Link
|-
| Bad Cats || [[file:YT.png]] [https://youtu.be/-JJKPvMBplg Audio]
|-
| Bally Game Show || [[file:YT.png]] [https://youtu.be/vwA4FST62ug Audio]
|-
| Banzai Run || [[file:YT.png]] [https://youtu.be/6D87Z2iUsv0?si=x8BKbDsxHFI_yodb Audio]
|-
| Big Guns || [[file:YT.png]] [https://youtu.be/dVuZsHhdzwE?si=myMFNRyghT2aJs7u Audio]
|-
| Black Knight 2000 || [[file:YT.png]] [https://youtu.be/uyJlxc2ewtY Audio]
|-
| Cyclone || [[file:YT.png]] [https://youtu.be/pEdSxFu1Zio Audio]
|-
| Diner || [[file:YT.png]] [https://youtu.be/rwCLpG5jU2I Audio]
|-
| Earthshaker || [[file:YT.png]] [https://www.youtube.com/watch?v=eH0FVvbBQUQ Audio]
|-
| Elvira & the Party Monsters || [[file:YT.png]] [https://youtu.be/OS_SRCNaMwg?si=6Wop4YLK2wa6Mco4 Audio]
|-
| F-14 Tomcat || [[file:YT.png]] [https://youtu.be/rG26I-oDK6E Audio]
|-
| Fire! || [[file:YT.png]] [https://youtu.be/dXKRw1GqUcQ Audio]
|-
| High Speed || [[file:YT.png]] [https://youtu.be/yAmJzD9EAZA Audio]
|-
| Jokerz || [[file:YT.png]] [https://youtu.be/E5QrfiZYVVY?si=3ttDBR_PHdbjnFMY Audio]
|-
| PinBot || [[file:YT.png]] [https://youtu.be/CoVvhwggLfU Audio]
|-
| Police Force || [[file:YT.png]] [https://youtu.be/Em63v0-zJKk?si=gt3qD2jLsqJFdwlW Audio]
|-
| Pool Sharks || [[file:YT.png]] [https://youtu.be/gceZEgLMaDQ Audio]
|-
| Riverboat Gambler || [[file:YT.png]] [https://youtu.be/6SBGT7_P62g?si=kAmVE1EUglQTyn8T Audio]
|-
| Rollergames || [[file:YT.png]] [https://youtu.be/tN-Ns9eh8Pg Audio]
|-
| Space Station || [[file:YT.png]] [https://youtu.be/9XERXpVGCsY?si=jSNjikeN1nM6GeQy Audio]
|-
| Swords of Fury || [[file:YT.png]] [https://youtu.be/u6baQrse5LI?si=3Y85cpAXqDF5_Qis Audio]
|-
| Taxi || [[file:YT.png]] [https://youtu.be/P7DIs5djK-E Audio]
|-
| Whirlwind|| [[file:YT.png]] [https://www.youtube.com/watch?v=fy_GXp3Bfzg Audio]
|}
 

===Flipper problems===

==== Flipper Circuit Schematics Error ====
[[File:WMS Serial Flipper Schems.JPG|left|300px|thumb|Correct wiring schematic for serial wound flipper coils]]
[[File:WMS Serial Flipper Schems Incorrect.JPG|right|300px|thumb|Incorrect wiring schematic for serial wound flipper coils]] 
Early System 11 and 11A games used serial wound coils. These coils only have a single diode on them. Some of the early System 11 manuals show incorrect wiring for the EOS switch. One of the EOS switch wires should be soldered to the center lug of the coil. However, the other wire should be soldered to the lug with the non-banded side (anode) of the diode, not the lug with the banded side (cathode) of the diode. Manuals which have this misinformation are High Speed, Grand Lizard, and Road Kings. Millionaire and Pinbot appear to be fine.
 

==== Flipper Electrical Problems ====

System 11 (nothing) and System 11A games derive 50VDC flipper power from the "50V Flipper Power Board".
System 11B and 11C games derive 50VDC flipper power from the "Aux Power Supply" board that was introduced with these games.

System 9 and 11 flipper circuitry is identical to all prior Williams System 3-7 games. The design had not changed from even the old electro-mechanical flipper implementation when the End of Stroke switch was introduced.

Yes, Williams used serial wound coils from High Speed to Millionaire and then converted to parallel wound coils beginning with F-14 TomCat and throughout the rest of the System 11 run and into the WPC run. But the basic operation of System 9/11 coils remained "EM-like" whether serial or parallel wound.

There are only three switches that can affect the electrical operation of a System 11 flipper, including strength.

#Switches inside the Flipper Enable relay (K1), located on the MPU board.
#The cabinet flipper button switches.
#An End-of-Stroke (EOS) switch associated with each flipper coil and integrated into the flipper mechanism assembly.

====Series Wound Flipper Coil Operation====
When the flipper enable relay (K1) switches close, a path to ground is provided for the flipper coil. The EOS switch is closed, creating a short across the low power windngs, that removes resistance of the low power windings from the circuit. Only the smaller number of high power windings are "in circuit" with the EOS switch closed.

When the flipper cabinet switch is closed by pressing the flipper button, this is the final switch in the path to ground for the waiting power at the low resistance high power windings of the coil. The coil plunger is pulled into the coil and the flipper "flips". Near the end of the flipper's mechanical stroke, a pawl (a tab that sticks up) on the flipper crank mechanism will open the EOS switch, removing the short across the low power windings, and placing them in series along with the high power windings. Together, the total resistance of the coil becomes the sum of both the low power and the high power windings. With more windings, the coil will have higher resistance and hence, lower power. The combined high resistance windings act like a "hold" or "coin door lockout" relay coil, able to withstand being energized for extended periods of time. Without the mechanization of the EOS switch, the high power windings would overheat quickly and damage the coil. For this reason, EOS switch adjustment, and a clean EOS switch, are critical.

====Parallel Wound Flipper Coil Operation====
[[File:ParallelWoundFlipperDiagram.jpg|left|400px|thumb|Parallel Wound Flipper Coil Operation. Diagram courtesy of Chris Hibler.]]
When the flipper enable relay (K1) switches close, a path to ground is provided for the low power windings of the flipper coil. And, since the EOS switch is closed, the high power windings also have a path to ground.

When the flipper cabinet switch is closed by pressing the flipper button, this is the final switch in the path to ground for the waiting power at both of the coil parallel windings. Since electrical current "takes the path of least resistance" the lower resistance high power winding takes most of the current and the flipper "flips". Near the end of the flipper's mechanical stroke, a pawl (a tab that sticks up) on the flipper crank mechanism will open the EOS switch, breaking the path to ground for the high power windings. The high resistance low power windings remain in circuit, and provide "hold" power to the flipper coil. The high resistance low power windings act like a "hold" or "coin door lockout" relay coil, able to withstand being energized for extended periods of time. Without the mechanization of the EOS switch, the high power windings would overheat quickly and damage the coil. For this reason, EOS switch adjustment, and a clean EOS switch, are critical.
 

==== Flipper Mechanical Problems ====

*Return springs
*Fractured nylon bushing
*Insufficient gap between nylon bushing and crank
*Heat damaged coil
*Damaged coil sleeve
*Damaged coil stop
*Flipper shaft slipping within crank
*Others?

===Pop bumper problems===

==Repair Logs and Game Specific Problems and Fixes==
Did you do a repair? Log it here as a possible solution for others.

===System 11 Display Single AlphaNumeric Character Won't Light===
[[File:Sys11B Bridged Header.jpg|300px|left|thumb|A solder bridge on the "digit strobe" connector.]] 
In the category of "things that will make you crazy", the solder bridge pictured at left shorted pins 8 and 9 on the connector that carries the digit strobes to a System 11 display. This prevented one of the digits on the display from ever lighting. It's always a good idea to examine prior work closely. Assuming the prior tech knew what they were doing is not always valid. 

===Using a System 6/7 Speech Board in a Comet===
[[File:WMS Sys9 CPU with 2732 Speech.JPG|300px|left|thumb|A Modified System 6/7 Speech Board Functioning with a System 9 CPU]] 
Should the need arise, a System 6/7 speech board can be [http://www.pinwiki.com/wiki/index.php?title=Williams_System_3_-_7#Modifying_the_System_6.2F7_Speech_Board_to_Use_2732_EPROMs modified to use 2732 EPROMs] for a Comet.
 

===Using a Data East MPU Board in a System 11 Game===
Whaaaat?!?! Yes, a Data East MPU can be used in a Williams or Bally System 11 game. However, this is limited to System 11C games only, and only a DE 520-5003-03 (Version 3) MPU can be used. The reason for this limitation is because games previous to 11C have some or all of the sound section circuitry on the MPU board populated, the 11C does not. Likewise, DE boards do not have any sound section circuitry located on them by design. The board swap is not a simple drop in replacement though. Some minor modifications have to be performed for the DE board to function properly in an 11C game.

The first hurdle is to properly power the DE board. Connection 1J17 is where power originates on the 11C board. The complimentary connection on a DE board is CN17. The problem is that these connections are keyed differently between the two boards. 1J17 has a key at pin 7, while the key on CN17 is at pin 8. The safest way to make a connection to CN17 with the 11C game harness is to remove pin 7 on the DE board. This will have no ill effect, if the DE board is to be placed back into a DE game. The worst case scenario if pin 7 is removed and the board placed back into a DE game is that the CN17 connector housing could be installed off by one pin, thus shorting the +5v to ground, and blowing the logic voltage fuse. 

[[File:DE MPU Jumpers for 11C.JPG|300px|thumb|left|Correct jumper setting on DE MPU for 11C game ROMs]]
[[File:DE MPU Special Solenoid Wire Swap for 11C.JPG|300px|thumb|right|Addition harness and Z-connector installed to correct special solenoid drive outputs]]
Next, the game ROM jumpers have to be set correctly. Since all 11C games use dual ROMs, jumper setting J4 must be in on the DE MPU, while J5 is out. Install the 11C game ROMS in the following positions. U27 (ROM 1) is to be inserted into the 5C socket, while U26 (ROM 2) is installed into the 5B socket. Notch on the chip / socket is facing to the right. There is an alternative method. The code for the dual ROMs can be burned into a [http://www.pinwiki.com/wiki/index.php?title=Data_East/Sega#Burning_Dual_ROMs_into_a_Single_5C_ROM single 27512 EPROM.]

Finally, there is a problem with how DE boards poll the special solenoid drivers differently than 11C boards. Two of the drivers are correct (solenoids 17 and 21), while the four others are mismatched. To overcome this problem, either a harness can be created (DE board to 11C harness) with a Z-connector installed between 1J19 and the game harness, or the 7-pin housing (the 9-pin housing at 1J19 is split with a 2-pin housing and a 7-pin housing) at 1J19 can be repinned. The benefit of building a harness and adding a Z-connector is that it is easily reversible, if an 11C board is to be placed back into the game at a future time. 

The following wires will have to be connected to 1J19 / CN19 on the DE board for the game to function as intended.

{| class="wikitable"
!Pin Connection
!Stock Wiring
!Swapped Wiring
!Notes
|-
|1 || ORG-VIO || ORG-VIO || No change. This is for the flipper enable.
|-
|2 || ORG-GRY || ORG-GRY || No change. This is for the flipper enable.
|-
|3 || BLU-ORG || BLU-YEL ||
|-
|4 || BLU-RED || BLU-ORG ||
|-
|5 || Key || None ||
|-
|6 || BLU-YEL || BLU-BLK ||
|-
|7 || BLU-BRN || BLU-BRN || No change.
|-
|8 || BLU-GRN || BLU-GRN || No change.
|-
|9 || BLU-BLK || BLU-RED ||
|-
|}
 

=== Ball Will Not Kick Over to Shooter Lane at Game Start (Pinbot) ===
Trough and shooter lane switches test alright in switch test. Ball feeder coil from trough to shooter lane tests fine in solenoid test. If the motor for the visor is disconnected, and the visor does not cycle at the start of the game, the ball will not kick to the shooter lane. This may be an issue if one or both of the visor switches are not recognized too. Not certain what code revision this particular game was running.

=== Ball Will Not Kick Over to Shooter Lane and Drop Target Will Not Reset (Cyclone) ===
[[File:Cyclone UnderPF Fuse 1A 5A.jpg|300px|thumb|left|Fuse under the playfield of a Cyclone, which powers solenoids 1A and 5A]] 
Both the outhole solenoid (1a) and drop target reset solenoid (5a) are the only multiplexed 24v coils in Cyclone. The power wires for these coils are brown. For some reason, Williams decided it would be a good idea to put a fuse under the playfield for these coils (which is not included in the documentation). The fuse/fuseholder is located just to the right of the spook house subway.
 

===Special Solenoids Are Not Pulsed During Solenoid Test on System 9 Games===
The System 9 circuit board architecture provides no physical way to control the special solenoids other than via the enabling switch associated with the special solenoid device.

===CPU energizes a coil 5 times===
'''Police Force''' - After the pinball is switched on the ramp diverter coil engages 5 times. After the game start the diverter coil engages 5 times again. Diverter mechanism doesn't hold in position. So after the coil is energized the mechanism falls back and so the switch is closed again. Then the software tries another 4 times to resolve the problem. 

'''Resolution:''' Clean the diverter mechanism and in particular the plastic. Lubricate the plastic lanes!

===Elvira and the Party Monsters drop target reset coil blows the lamp matrix===
The drop target reset coil should be mounted with the solder tabs down. If mounted with the solder tabs up, (toward the playfield) the solder tabs can contact the J-A-M lamp sockets. This blows the lamp matrix ICs on the MPU board by sending coil voltage through the lamp matrix.

Williams System 9 - 11

2025-06-30T15:36:30Z

The Hammer: /* An Alternative to Rebuilding the Reset Circuit / Using a Reset Generator (All versions of System 11) */ updating part ordering information.

Click to go back to the [[Williams_Repair_Guides | Williams solid state repair guides index]].

==Introduction==

[[File:Wms sys9 boardset.jpg‎|300px|thumb|left|Williams System 9 Board Set from Space Shuttle]]
[[File:System11NothingBackbox.jpg|thumb|right|300px|Williams System 11 (nothing) Board Set from High Speed]]
[[File:WMS Sys11 Boardset.JPG|thumb|left|300px|Williams System 11A Board Set from Pinbot]]
[[File:WMS Jokerz Boardset.JPG|thumb|right|300px|Williams System 11b Board Set from Jokerz! (Note that power supply is a prototype)]]
[[File:WMS Sy11B Boardset.JPG|300px|thumb|left|System 11b Board Set from Transporter the Rescue]]
[[File:WMS_Sys11C_Boardset.JPG|thumb|right|300px|System 11c Board Set from Rollergames]] 
The Williams system 7 boardset was replaced in 1984 with the system 9 boardset, and then again in 1985 with the system 11 boardset. Combining the driver board, sound board, and cpu directly onto one board eliminated several design deficiencies of the earlier 3-7 boardsets; mainly the 40 pin interconnector, and extra wiring harness inter-board connectors. Larger ROMs could be fitted directly onto the boards allowing for more complex rulesets and sounds.
 

The System 9 and System 11 board sets are not 100% compatible. With a fair amount of effort, a System 11 board could be made compatible with a System 9, but it is not worth the extended effort to change the jumpers. It's far easier to just modify the rom images so that they are plug and play when installed in a System 11 CPU. You can find them already on the ipdb. The primary differences between the System 9 and System 11 board sets are the sound system and rom space.
(add more info later)

As time went on, the System 11 board set underwent some changes too. The power supply, sound board, and CPU / driver board have minor changes. More apparent was the addition of circuit boards. Starting with the 11a board set, a more complex sound board was added (System 11 sound boards are strictly background sounds only). Later in the System 11 series, sound functions were partially (11B) or fully removed (11C) from the MPU, and eventually were solely handled by a dedicated sound board. Game-specific interconnect boards and auxiliary power driver boards were introduced in System 11B games. The interconnect boards acted as a pass-through for switch, lamp, flasher, and solenoid signal lines and circuits. It also allowed circuits with different voltages to share the same power source by using current limiting resistors to drop voltages to the appropriate levels. All general illumination fuses were moved to this board. The auxiliary power driver board has the AC relay, which finally centralized the location of it. Likewise, several fuses, beefier TIP36C transistors, and bridge rectifiers are centralized on the auxiliary power driver board.

 

==Games==
===System 9===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Other Boards
!Transformer
!Notes
|-

|Strike Zone|| 1984 || 1916 || unknown || || || This is a shuffle alley which uses some pinball boards
|-
|Star Light|| 06-1984 || 530 || no speech || || 5610-09563-00 || only a few were made with System 9 boards inside
|-
|Space Shuttle|| 12-1984 || 535 || C-10716 (Speech only) || || 5610-09563-00 and 5610-10355-00 ||
|-
|Sorcerer|| 03-1985 || 532 || C-10716 (Speech only) || || 5610-09563-00 and 5610-10355-00 ||
|-
|Comet|| 06-1985 || 540 || C-10716 (Speech only) || || 5610-09563-00 and 5610-10355-00 ||
|}

===System 11===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Other Boards
!Transformer
!Notes
|-
|Alley Cats|| 10-1985 || 1918 || Unknown || || || This is a shuffle alley which uses some pinball boards
|-
|[[High Speed]]|| 01-1986 || 541 || C-11030 (Background sound only) || || 5610-10897-00 ||
|-
|Grand Lizard|| 04-1986 || 523 || C-11030 (Background sound only) || || 5610-10897-00 ||
|-
|Road Kings|| 07-1986 || 542 || D-11197-542 (Background music only) || || 5610-10897-00 ||
|}

===System 11A===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Other Boards
!Transformer
!Notes
|-
|Pinbot|| 10-1986 || 549 || D-11297-549 (Background Speech & Sound) || || 5610-10897-00 ||
|-
|Tic Tac Strike|| 11-1986 || 1919 || Unknown || || || This is a shuffle alley which uses some pinball boards
|-
|Millionaire|| 01-1987 || 555 || [[Media:WMS Sys11 Sound D-11298-555.JPG | D-11298-555]] (Background Speech & Sound) || || 5610-10897-00 ||
|-
|F-14 Tomcat|| 03-1987 || 554 || D-11298-554 (Used on 1st 5,000 games - Background Speech & Sound) / D-11581-554 || || 5610-12136-00 ||
|-
|Fire!|| 08-1987 || 556 || D-11581-556 || || 5610-12136-00 ||
|-
|Fire! Champagne Edition|| 09-1987 || 556 || D-11581-556 || || ||
|}

===System 11B===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Power Supply
!Aux Power Driver
!Master Interconnect
!Other Boards
!Transformer
!Notes
|-
|Big Guns|| 10-1987 || 557 || D-11581-557 || D-8345-557 || D-11583-557 || C-11762 || Uses D-11814 Flash Lamp Resistor Board || 5610-12136-00 ||Uses special solenoid switches
|-
|[[Space Station]]|| 12-1987 || 552 || D-11581-552 || D-8345-557 || D-11813-552 || C-11762-552 || Uses D-11814-552 Flash Lamp Resistor Board || 5610-12136-00 ||Uses special solenoid switches
|-
|Gold Mine|| 01-1988 || 1920 || None || D-8345-1914 || None || None || || || This is a shuffle alley which uses some pinball boards
|-
|Cyclone|| 02-1988 || 564 ||[[Media:WMS Sys11 Sound D-11581-564.JPG | D-11581-564]] || D-8345-557 || D-11813-574 || C-11762-564|| Uses D-11814-564 Flash Lamp Resistor Board || 5610-12136-00 ||Does not use special solenoid switches
|-
|Banzai Run|| 05-1988 || 566 || D-11581-566 || D-8345-566 ||D-12247-566 || D-12112 || || 5610-12136-00 ||Uses special solenoid switches
|-
|[[Swords of Fury]]|| 06-1988 || 559 || D-11581-559 || D-8345-557 || D-12247-559 || D-12313-559 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|Taxi|| 08-1988 || 553 || D-11581-553 || D-12246-553 || D-12247-559 || D-12313-553 || || 5610-12136-00 ||Uses special solenoid switches
|-
|Top Dawg|| 11-1988 || 1921 || None || D-12246 || None || D-12313-1921 || || || This is a shuffle alley which uses some pinball boards
|-
|Jokerz!|| 12-1988 || 567 || D-12338-567 || D-12246 || D-12247-559|| D-12313-567 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|[[Earthshaker]]|| 02-1989 || 568 || [[Media:System 11 Sound Board.JPG | D-11581-568]] || D-12246-568 || D-12247-559 || D-12313-568|| || 5610-12136-00 ||Does not use special solenoid switches
|-
|[[Black Knight 2000]]|| 04-1989 || 563 || [[Media:WMS Sys11 Sound D-11581-585.JPG | D-11581-585]] || D-12246 || D-12247-563 || D-12313-563|| || 5610-12136-00 ||Uses special solenoid switches
|-
|Transporter the Rescue|| 04-1989 || 2008 || D-11581-2008 || D-12246 || D-12247-2008|| D-12313-2008 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|Police Force|| 08-1989 || 573 || D-11581-573 || D-12246 || D-12247-566 || D-12313-573|| || 5610-12136-00 ||Does not use special solenoid switches
|-
|Shuffle Inn|| 10-1989 || 1922 || None (assumed) || D-12246 (assumed) || None || D-12313-1922 (assumed)|| || || This is a shuffle alley which uses some pinball boards
|-
|Elvira and the Party Monsters|| 10-1989 || 2011 || D-11581-2011 || D-12246 || D-12247-2011|| D-12313-2011 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|Bad Cats|| 11-1989 || 575 || D-11581-575 || D-12246 || D-12247-566 || D-12313-575|| || 5610-12136-00 ||Does not use special solenoid switches
|-
|Mousin' Around!|| 12-1989 || 2009 || D-11581-2009 || D-12246 ||D-12247-2009 || D-12313-2209 || || 5610-12136-00 ||Does not use special solenoid switches
|-
|[[Whirlwind]]|| 01-1990 || 574 || D-11581-574 || D-12246 || D-12247-574 ||D-12313-574 || Uses a C-13287 Sound Overlay Solenoid Board to control 5 extra devices || 5610-12136-00 ||Does not use special solenoid switches
|}

===System 11C===

{| class="wikitable"
!Title
!Date of Release
!Model #
!Sound
!Master Interconnect
!Other Boards
!Transformer
!Notes
|-
|The Bally Game Show|| 04-1990 || 2003 || D-11581-2003 w/ 512K ROMS|| D-12313-2003 || Uses a C-13286 Sound Overlay Lamp Board || 5610-12136-00 || Does not use special solenoid switches
|-
|Pool Sharks|| 06-1990 || 2014 || D-11581-2014 w/ 512K ROMS|| D-12313-2014 || || 5610-12136-00 || Does not use special solenoid switches
|-
|[[Rollergames]]|| 06-1990 || 576 || D-11581-576 w/ 512K ROMS|| D-12313-576 || || 5610-12136-00 || Does not use special solenoid switches
|-
|Diner|| 09-1990 || 571 || D-11581-571 w/ 512K ROMS|| D-12313-571 || || 5610-12136-00 || Does not use special solenoid switches
|-
|Radical!|| 09-1990 || 2015 || D-11581-2015 w/ 512K ROMS|| D-12313-2015 || || 5610-12136-00 || Does not use special solenoid switches
|-
|Dr. Dude|| 11-1990 || 2016 || D-11581-2016 w/ 512K ROMS|| D-12313-2016 || || 5610-12136-00 || Does not use special solenoid switches
|-
|[[Riverboat Gambler]]|| 11-1990 || 50007 || D-11581-50007 w/ 512K ROMS (assumed) || D-12313-50007|| || 5610-12136-00 || Does not use special solenoid switches
|-
|Bugs Bunny's Birthday Ball|| 01-1991 || 20009 || D-11581-20009 w/ 512K ROMS|| D-12313-20009 || || 5610-12136-00 || Does not use special solenoid switches
|}

Game date of release and model numbers provided by the Internet Pinball Database - http://www.ipdb.org

==Recommended Documentation==
===Manuals & Schematics===
Schematics for each game are essential in tracing down connections to lamps, switches, and solenoids. The owner's game manual is a handy resource to have for general game operation, game settings & diagnostics, switch & lamp matrices, fuse lists, circuit boards and parts, playfield assemblies, some basic schematics, and wiring diagrams.

Be aware that although rare, some factory documentation contains errors in schematics, wiring, switch/lamp matrices, and solenoid assignments.

====Documentation Errors====
* Error on the [[High_Speed#MPU_Schematics_Error_for_U21_.26_U22|MPU I/O signals for U21 / U22 of High Speed]].
* [[#Flipper_Circuit_Schematics_Error|Flipper Circuit Schematics Error]] in the manuals for High Speed, Grand Lizard, and Road Kings.

===Theory of Operation & Schematics===
Details for board and cabinet schematics System 9-11 games can be found in the game manual or parts catalogs. Some copies can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball] or on [http://www.ipdb.org/ IPDB].

{| class="wikitable"
|-
!Manufacturer
!Guide
!Version
!Cover
!Source
!Games
!Notes

|-
|Williams
|Pinball Troubleshooting & Reference Manual
|69-8955 (April 21, 1986)
|[[file:placeholder.jpg|thumb|left|140px]]
|[[media:Williams-pinball-troubleshooting-reference-manual_16-8955_sys9.pdf|PDF]]
|Comet, High Speed, Sorcerer, Space Shuttle, Star Light
|System 9 games. Also includes Strike Zone shuffle alley game.

|}

===Schematics===
* [[media:Audio_schem_11581.pdf|D-11581 Sound Board]]

===Parts Catalogs===
Parts catalogs can also be useful, which include part numbers (helpful for purchasing parts online), exploded views of assemblies (helpful to see how the assemblies are put together), and board layouts & parts lists, and diagrams for controlled lamp, solenoid, and rubber locations. Parts catalogs also had supplementary updates to add and replace pages as newer games were released after the initial release of the catalogs.

Online copies of Bally & Williams parts catalogs can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball].

{| class="wikitable"
|-
!Manufacturer
!Catalog
!Version
!Cover
!Source
!Games
!Notes

|-
|Williams
|Blue Parts Catalog (1986-1989)
|16-9064-B
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/rvsk/ Viewer] [[media:Williams-parts-catalog-blue-book_16-9064-B.pdf|PDF]]
|Banzai Run, Big Guns, Black Knight 2000, Comet, Cyclone, Earthshaker!, F-14 Tomcat, Fire!, Grand Lizard, High Speed, Jokerz!, Millionaire, Pin Bot, Police Force, Road Kings, Sorcerer, Space Shuttle, Space Station, Swords of Fury, Taxi
|

|-
|Williams
|Red Parts Catalog (1989-1992)
|16-9190-B
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/feme/ Viewer] [[media:Williams-parts-catalog-red-book_16-9190-B.pdf|PDF]]
|Bad Cats, Diner, Dracula, Fish Tales, Funhouse, The Getaway, Hurricane, The Machine, Riverboat Gambler, Rollergames, Slugfest, Terminator 2, Whirlwind, White Water
|

|-
|Bally/Midway
|Yellow Parts Catalog (1988-1992)
|16-9147-B
|[[file:placeholder.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/itjk/ Viewer] [[media:Bally-midway-parts-catalog-yellow-book_16-9147-B.pdf|PDF]]
|Addams Family, Atlantis, Black Rose, Bugs Bunny, Dr. Dude, Dr. Who, Elvira, Game Show, Gilligan's Island, Harley Davidson, Mousin' Around, Party Zone, Pool Sharks, Radical!, Transporter, Truck Stop
|

|}

===Service Bulletins===
Supplementary service bulletin books were released, which included service bulletins that detailed any problems or issues with games that were discovered after they were released.

{| class="wikitable"
|-
!Manufacturer
!Version
!Cover
!Source
!Games
!Notes

|-
|Williams
|Service Bulletin Book, 1989
|[[file:Williams-Service-Bulletin-Book-1989-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1989.pdf|PDF]]
|Cyclone, Bonzai Run, Taxi, Earthshaker, Truck Stop, Transporter
|

|-
|Williams
|Service Bulletin Book, 1990
|[[file:Williams-1990-service-bulletin-cover.jpg|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1990.pdf|PDF]]
|Diner, Police Force, Pool Sharks, Rollergames
|

|-
|Williams
|Service Bulletin Book, 1991
|[[file:Williams-1991-service-bulletin-book-cover.png|thumb|left|140px]]
|[[media:Williams-service-bulletin-book-1991.pdf|PDF]]
|Dr. Dude, Jokerz, Riverboat Gambler
|This book includes some WPC games

|}

==Technical Info==
System 9 eliminated a huge issue with the earlier system 3 through 7 boardsets, the 40 pin interconnect between the MPU and Driver boards. All circuitry previously separated into MPU, driver, and sound boards was combined into a single MPU board. Satellite boards were still used for displays, speech, and solenoid expansion.

Starting with '''Big Guns''', Williams introduced another weak link into their system, the interconnect board. Initial implementations were used to disperse the general illumination between the playfield and backbox. The connectors on interconnect boards were prone to overheating and failure just like prior implementations. At the same time, flash lamp resistor boards were being used. These were created to collocate all of the flashlamp current limiting resistors, and eliminate under playfield flashlamp resistor boards, which had proven themselves problematic in the high heat, high vibration environment under the playfield. Resistors often desoldered themselves and/or vibrated so much that the connection fractured. Flash lamp resistor boards were only used on three games: Big Guns, Space Station, and Cyclone. In addition to the interconnect and the flash lamp resistor board, the auxiliary power driver board made its appearance. The auxiliary power driver board housed all of the high current transistors (TIP36c), solenoid and flasher fuses (including discrete flipper fuses), the AC select relay, and the solenoid power bridge rectifiers. The auxiliary power driver board did go through some minor changes, but it was functionally equivalent through the last System 11C game.

Starting with Banzai Run, a more standardized interconnect board was created. This interconnect board merged the general illumination interconnect with the flasher driver board. Switch and lamp circuits passed directly through this board as a matter of manufacturing convenience. Later interconnect boards added 3 opto couplers to indicate when the flippers and AC relay were activated (the same circuitry as used in the flipper power section of the WPC-089 -1 Power/Driver board).

One of the largest advantages of the system 11 board set is its ability to switch one set of coil driver transistors between 2 sets of coils/flashers. This is accomplished via a relay on a separate board called the A/C select relay (the A/C select relay was eventually moved to the auxiliary power driver board starting with Big Guns). The theory is that coils that are less frequently activated will be on the A side of the relay, and that flashers will be on the C side of the relay. Most of the time during gameplay, the C side is active, enabling the flashers. If the driver transistor for the A/C select relay itself shorts, the relay defaults to the coil side, allowing the game to continue to operate in a reasonable fashion (usually the A side coils are the ball shooter lane, drop target resets, VUK - basically coils that don't need to be able to operate 100% of the time unlike a slingshot coil or pop bumper coil). Data East's board set was essentially a copy of the system 11 board set, but Data East programmed it the opposite way, so that the flasher side of the A/C select relay is active by default. Data East games, when the A/C relay doesn't operate, just sits there and flashes lamps instead of playing.

System 9 and early System 11 games do share a disadvantage with the earlier 3-7 board sets, they still utilize special solenoid circuitry. The pops and slings on system 9/11 games do not activate via a switch which is seen by the MPU's program which fires the coil. Instead, the switches directly fire their associated coils via logic gates on the main board. The main disadvantage with this system is that the solenoids fire continuously as long as their activation switch is closed. A locked on sling or pop will burn out components quickly. It is recommended to add a 1, 1.5, or 2 amp inline fuse to each coil on a directly fired system 11 game. Usually just the pops and slings are direct fired coils. However, other coils were designated to the special solenoids.

Later System 11 games did not use the direct fire solenoid switches. Switches on the switch matrix were used instead. To easily identify games which do not use direct fire solenoid switches, IJ18 on the MPU board will not have a harness connection attached to it. Likewise, the slingshots and pop bumpers will no longer have a set of scoring switches.

One way that System 9 games differ from the previous 3-7 board set is that the special solenoids are not controlled by the CPU at all. In other words, the special solenoids are not pulsed during solenoid test, as the physical board architecture does allow for this.

The software in system 9-11 games continued with the same machine architecture from system 6 and 7, except for the special solenoids as mentioned above. More ram became available, up to 2k, but no game used over 800 bytes. This is likely due to the lower cost of 6264 RAM than 6116 RAM as was used in early System 9-11 games more than any other reason. Additional diagnostics in the form of switch error checking appeared in system 11. Any switch not activated over 30 games (16 games for flipper switches) would cause an error to be called out at power on. The software was able to compensate for broken switches by designating another switch to perform the same function as the broken switch. 

===MPU Driver Boards===
[[File:WMSSystem9MPU.jpg |300px|thumb|left|System 9 MPU]]
[[File:System9MPUFactoryMod.jpg |300px|thumb|right|These high frequency filter capacitors were added at the factory, and are normal. Their purpose is the snub high frequency noise in the Advance and Auto Up/Down coin door button circuits.]] 
'''System 9 MPU'''
Williams used a single version of the System 9 MPU in all System 9 games. A few minor modifications to the board may have been made, but it's essentially the same board for the entire 3 game run of Space Shuttle, Sorcerer, and Comet. The picture at left shows an early board that featured two inductors (copper wound coils that "smooth" DC power) at L1 and L2, adjacent to connector 1J17. Later revisions of the board used "zero ohm" jumpers instead, presumably to reduce cost.
 

[[File:WilliamsSystem10MPUFront.jpg ‎|300px|thumb|left|Williams System 10 MPU component side. Image courtesy of Brian Johnson.]]
[[File:WilliamsSystem10MPUBack.jpg ‎|300px|thumb|right|Williams System 10 MPU solder side. Image courtesy of Brian Johnson.]] 
Williams released a single game using an MPU board designated '''System 10'''. The game "4-in-1" ([https://www.ipdb.org/search.pl?any=4-in-1&sortby=name&search=Search+Database&searchtype=quick IPDB link]) was released in 1985 and is more like Pachinko than pinball.

From the Internet Pinball Database:

"This game is known in Williams documentation as "4-IN-1" but that name never appears on the game itself. A total of 100 games were produced. Each came with four interchangeable playfield overlays for the themes of Baseball, Poker, Football, and Soccer. The operator could change the overlay and Instruction Card, re-option switches, and have a new game in the same cabinet."
 

'''System 11''' games used one of four different revisions of the System 11 MPU. The first version of the System 11 MPU was completely self-contained, able to make game sounds on the board. A simple background sound board was used to add some game sounds. Between the baseline revision of the System 11 MPU and the last revision of the MPU (System 11C) incrementally more of the sound processing and sound circuitry was removed from the board (not stuffed). None of the System 11 shuffle alley games use a separate sound board.

[[File:WilliamsSystem11CPU.jpg|300px|thumb|left|Early System 11 (nothing) MPU]]
[[File:System11NothingLater.jpg|300px|thumb|right|Later System 11 (nothing) MPU. Note extensive alkaline corrosion abatement, NVRAM install, and use of modern reset generator. Image courtesy of Chris Hibler]] 
'''System 11 (nothing) MPU''' 
This picture shows the early System 11 MPU. A later revision of this MPU, pictured at right, has an additional jumper W16 located between the 7 segment diagnostic display and the relay, and a 4.7K ohm resistor between the 7447 and the resistor DIP. The early PCB on the left has a trace routing error to the sound ribbon cable connector. If you use it with a later system 11A sound card you will get no sound because the sound card doesn't get reset properly. If you wonder why your High Speed doesn't beep when turning it on this one is also the culprit.
 

[[File:System11ZenerDiodeAddition.jpg|300px|thumb|left|6.2V Zener Diodes added to the back of the System 11 (nothing) MPU. These zeners were added to the layout of the PCB in subsequent revisions of the board (11A, etc).]]
[[File:WMSSystem11Zener1N5234.jpg|300px|thumb|right|6.2V Zener Diodes (ZR3-ZR8) incorporated into the board layout and stuffed at the factory on a later board revision. Note: in this image, ZR7 and ZR8 have been replaced]] 
The picture at left shows six 6.2V zener diodes added to the solder side of a System 11 (nothing) MPU. These zeners were left off the factory silkscreen of the board. Later revisions of the System 11 MPU added them to the component side of the board. Their purpose is to protect the special solenoid switch inputs. Either a ZPY6,2/ZD6,2/1N4735A (1 watt) or ZF5,2/1N5234B (1/2 watt) can be used. This mod is purely optional. In reality the diode doesn't help much if you short the switch input with the solenoid voltage. In this case the diode and the 7402 are usually damaged and need to be replaced.
 
Additionally, if the System 11 (nothing) MPU is used in a System 11A game or later, pins 6 and 7 of the adjacent connector (J18) must be tied to the ground plane at the edge of the board. These pins provide the ground for the special solenoids. Without the modification they do not work. Some early System 11A pins might not need the mod. If unsure just check if a cable is connected to pin 6 or 7 in your game.
 

[[File:CPUWilliamsSystem11A-PB.jpg|300px|thumb|left|A rare prototype System 11a MPU]]
[[File:System11aTransitionVersion.jpg|300px|thumb|right|Blanking, 5VDC, and Diagnostic LEDs factory installed in a "transition" vintage System 11a MPU. The prior version 7447 (U48) and resistor DIP (U47) has been replaced with a 7407, discrete resistors and LEDs.]]
[[File:System11TransitionTag.jpg|300px|thumb|left|A prototype System 11a MPU with original label]] 
'''System 11a ''Prototype'' MPU''' 
This MPU was only used in Pin Bot. It's actually a System 11 (nothing) MPU PCB layout, with the 7 segment LED display replaced at the factory with 3 LEDs as used in all later System 11 MPUs (11A/B/C). The latest trace revision of this board also has the ground mod (connect 1J18, pins 6 and 7 to board ground) allowing it to work in any 11A/B/C game without modification. According to a friend it was referred to by the name of 11a instead of 11A by distributors.
 

[[File:CPUWilliamsSystem11A.jpg|300px|thumb|left|A late production System 11A MPU.]] 
'''System 11A MPU''' 
The System 11A MPU can be used in all System 11 games. If used in one of the four first System 11 games (Alley Cats, High Speed, Grand Lizard, and Road Kings), connector 1J15 and possibly the amplifier section must be stuffed. System 11A, 11B, and 11C games don't use the amplifier section of the MPU board. Sound amplification is accomplished on the sound board. On early production system 11A boards, the amplifier section was fully stuffed, just like the original System 11 board. Later in the production of System 11A boards, the amplifier section was not stuffed, just like an 11B board. But unlike System 11B boards, the System 11A board still has the same switch section layout as the original System 11 MPU, making it easy to identify.

'''Note:''' the sound mixing section of the System 11A MPU is stuffed with different resistor and capacitor values than that of the System 11B MPU. This may cause some sound quality differences as has been noted with EarthShaker.
 

[[File:System 11 CPU Driver Board.JPG|300px|thumb|left|System 11B MPU. Note that a large portion of the sound circuitry, including the TDA2002 amp, was not stuffed in late System 11A boards or any System 11B MPU boards.]] 
'''System 11B MPU''' 
The System 11B MPU can be used in all System 11 games too. If used in one of the four first System 11 games (Alley Cats, High Speed, Grand Lizard, and Road Kings), connector 1J15 and all of the sound amplification components must be added to the board. System 11A, 11B, and 11C games don't use the amplifier section of the MPU board. Sound amplification is accomplished on the sound board.

'''Note:''' the sound mixing section of the System 11A MPU is stuffed with different resistor and capacitor values than that of the System 11B MPU. This may cause some sound quality differences as has been noted with EarthShaker.
 

[[File:CPUWilliamsSystem11C.jpg|300px|thumb|left|System 11C MPU. Note that none of the sound circuitry, including the 6802 processor and 6821 PIA, is stuffed in System 11C MPU boards. All sounds were generated by the sound board.]] 
'''System 11C MPU''' 
The System 11C MPU can be used only in System 11C games since none of the sound processing circuitry was stuffed. It can be used in games prior to 11C, if the sound section is populated. However, some of the components needed are rare and / or costly, and there are a fair amount to install. If there is no other choice but to use this board, it is possible.
 

[[File:RottenDogMPU9211.jpg|300px|thumb|left|The RottenDog "System 9211" Aftermarket MPU]]
[[File:RottenDogMPU004.jpg ‎|300px|thumb|right|The RottenDog "MPU004" Aftermarket MPU with sound section overlay]] 
'''RottenDog MPU9211 and MPU004 Aftermarket MPUs''' 
The RottenDog aftermarket MPU9211 (shown at left) was designed to support all Williams System 9 - 11 games. How well the board works across that great breadth of games is somewhat questionable.

The CVSD used on this board is a CMX639D4 produced by CML Microcircuits. It replaces the 55516 (or 55536) CVSD used at U3 on original System 9 - 11 MPU boards.

The RottenDog aftermarket MPU004 (shown at right) was an earlier design thought to support all Data East and System 11 games. Again, how well the board accomplishes this for Williams games is questionable. A significant source of confusion on this board (like all RottenDog boards with DIP switches) is that the DIP switches are labeled opposite of traditional labeling. That is, set all switches to OFF for Williams games, ON for Data East games.
 
[[File:RDWilliams9211LaterRev.jpg |300px|thumb|left|The RottenDog "System 9211" Aftermarket MPU, later revision]] 
A later revision of the RottenDog 9211 MPU included a second trim POT to adjust the balance between 1408 DAC sounds and 55536 CVSD sounds.
 
====Lamp Matrix====
[[File:WMS Sys9 Lamp Column.jpg|300px|left|thumb|Picture of the lamp column portion of the lamp matrix of a System 9 MPU board. Note that the TIP42 drive transistors were removed from this board.]] 
The lamp matrix is made up of two parts - the lamp columns (drives) and lamp rows (returns). In most cases, the lamp row consists of eight 2N5060 over-current shunt SCR's and eight TIP122 drive transistors, while the lamp column consists of eight 2N6427 predrive transistors (WMS sometimes used MPS-A14 instead) and eight TIP42 or TIP42C transistors. However, there are some instances, as shown in the pic to the left, where the predrive transistors for the lamp columns are 2N6548s. It is unknown why Williams chose to use these transistors on occasion.

The over-current shunt circuit on the lamp row (returns) works by sensing the voltage drop across the 0.4 ohm, 3 Watt resistor on emitter of the TIP122 driver transistor. If a short circuit is present in the lamp row, the short circuit current will result in a higher than normal voltage drop across the emitter resistor. This voltage will trigger the gate of the 2N5060 SCR, causing it to turn on and shunt the base drive to the TIP122 transistor. This will turn off the driver transistor and prevent damage due to excessive current. Note that an RC circuit consisting of a 0.1uF capacitor and 1K ohm resistor is present on the gate of the SCR. This prevents a false trigger of the over-current shunt circuit due to an initial peak current from cold lamp filaments.
 

====Switch Matrix====
=====System 9 Switch Matrix Explained=====
[[Image:System9SwitchMatrix.jpg|300px|thumb|left|The System 9 Switch Matrix circuitry, as found in the Sorcerer manual.]]
General Description

At regular intervals, say 1 every msec or so, the 6808 microprocessor scans the switch matrix. This is done by pulling one switch column to ground, then sensing the switch row return state. Each row on which ground is detected means that the switch at the intersection of the column grounded and the detected row ground, is closed.

Hardware Detail

The 6808 writes the column data to the address location occupied by the 6821 at U15 on the board. This causes the 6821 output registers (PB0 – PB7) to propagate the data to a 74LS244 octal buffer at U45. The 74LS244 mirrors that same data at it's output pins. The data pattern on these output pins will have all bits set to logic “1” except one bit, which will be set to logic zero, or electrical ground. The ground is applied to the base of a 2N3904 transistor (which had been held high by a 4.7K SIP pull-up resistor SR8) where the ground is applied to the switch column (called switch matrix drives on the schematic). 

Closed switches connected to that column will then cause the normally high (via yet another pull up resistor, SR16) gate at a 74LS08 quad NAND gate (U51 and U52) to be pulled to ground. This NAND gate enables the circuitry to detect a switch closure returned via either connector 1J9 or 1J10.

The 6808 then “reads” the row returns by reading from the address space occupied by the same 6821 at U15 used to pulse the column strobes earlier. This time it reads 6821 registers PA0 – PA7.

Again, the processor knows which column it drew to ground, and it knows which rows were caused to be pulled to ground via closed switches attached to the column. From this information, the closed switches can be identified. Genius. Bania: “I'm tellin' ya Jerry, this switch matrix stuff is gold Jerry, it's gold!”.

The switch diode isolates the switch in the matrix. Without this isolation diode, multiple simultaneous switch closures will cause false returns and confuse the processor. A switch diode that is open will always prevent a switch from registering, in the same way that a broken wire or failed open switch would.
 

====Jumper Settings and Locations for System 9 & 11 MPU Boards====

Below are charts of the jumpers on System 9 & 11 boards. Rather than listing the boards by their platform (System 11A/B/C), each chart is listed by the numbers stenciled on the circuit boards.
 

'''5764-10749-00 REV. C (System 9)'''

Typically installed jumpers are W2, W5, W6, W7, W9, & W12.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1 / W2|| Below U12 || Microprocessor Internal RAM Enable. W1 IN, W2 OUT when using 6802, reverse when using 6808 || U12 RAM can be removed with 6802 and W1 installed.
|-
|W3|| || ||
|-
|W4|| || ||
|-
|W5|| Left of U49 || Country jumper. Remove for German factory settings, add for US factory settings ||
|-
|W6|| Below U5 || Along with W7, used to send +12V to opto rows || Typically installed, but not used
|-
|W7|| Below U5 || Along with W6, used to send +12V to opto rows || Typically installed, but not used
|-
|W8|| Below connector IJ9 || Ties resistor network SR15 to +12v ||
|-
|W9|| Below connector IJ9 || Ties resistor network SR15 to +5v ||
|-
|W10|| Below U50 || Installed - sounds from CPU board can be played without speech board attached || Typically not installed, except Strike Zone
|-
|W11|| Below U37 || Used when U19 game ROM 2 is used ||
|-
|W12|| Below U36 || Used to increase U20 game ROM 1 size from 2764 to 27128 ||
|-
|}
 

'''5764-10881-00 REV. - (Typically System 11)'''

Typically installed jumpers are W1, W2, W4, W5, & W7.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1|| Below U15 CPU chip || Ties crystal to clock input (pin 39) of U15 CPU ||
|-
|W2 / W3|| To the right of U25 RAM chip || Used to increase the ROM size ||
|-
|W4|| Below U31 (to the right of U25) || Used to increase the ROM size ||
|-
|W5|| Below U39 & U38 (PIA chip) || Used to apply +5v to SR14 resistor network ||
|-
|W6|| Below U30 & U27 || Used to apply +12v to SR14 resistor network ||
|-
|W7|| Below U48 || Country jumper. Remove for German text and settings, add for English text and settings ||
|-
|DS1|| Left of U13 || || Marked as DS1 on board (lower of 2 jumpers) - leave out
|-
|DS1|| Left of U13 || || Marked as DS1 on board (upper of 2 jumpers) - leave out
|-
|DS2|| Left of U13 || || Marked as DS2 on board (lower of 2 jumpers) - keep installed
|-
|DS2|| Left of U13 || || Marked as DS2 on board (upper of 2 jumpers) - keep installed
|-
|}
 

'''5764-10881-00 REV. B (Typically System 11 - Referred to as Prototype System 11a in text above)'''

Typically installed jumpers are W1, W2, W4, W5, W7, W8, W11, W12, W13, W14, W16, W17 & W18.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1|| Below U15 CPU chip || Ties crystal to clock input (pin 39) of U15 CPU ||
|-
|W2 / W3|| To the right of U25 RAM chip || Used to increase the ROM size ||
|-
|W4|| Below U31 (to the right of U25) || Used to increase the ROM size ||
|-
|W5|| Below U39 & U38 (PIA chip) || Used to apply +5v to SR14 resistor network ||
|-
|W6|| Below U30 & U27 || Used to apply +12v to SR14 resistor network ||
|-
|W7|| Below diagnostic LEDs || Country jumper. Remove for German text and settings, add for English text and settings ||
|-
|W8 / W9|| Below U24 (sound CPU chip) || Used to choose what to use as /RST for U24 sound CPU ||
|-
|W10 / W11|| To the right of 3 radial caps in reset section|| Choice of +18v (W10) or +12v (W11) for sound amplifier ||
|-
|W12|| A resistor below U10 PIA || Pull down resistor for E1 (pin 1) and E2 (pin 19) of U11 & U13 address line buffer chips ||
|-
|W13|| A resistor below U16 data line buffer chip || Pull down resistor for /E (pin 19) of U16 data line buffer chip ||
|-
|W14 / W15|| Below U29 || 1ms IRQ signal (W14 in) or 2ms IRQ signal (W15 in) ||
|-
|W16|| Below U27 || Blanking signal to input "D" of U48 LED decoder chip || not present on first pcb revision
|-
|DS1|| Left of U13 || || Marked as DS1 on board (lower of 2 jumpers) - leave out
|-
|DS1|| Left of U13 || || Marked as DS1 on board (upper of 2 jumpers) - leave out
|-
|DS2|| Left of U13 || || Marked as DS2 on board (lower of 2 jumpers) - keep installed
|-
|DS2|| Left of U13 || || Marked as DS2 on board (upper of 2 jumpers) - keep installed
|-
|}

 

'''5764-12091-00 REV. - (Typically System 11A)'''

Typically installed jumpers are W1, W2, W4, W5, W7, W8, W11, W12, W13, W14, W16, W17 & W18.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1|| Below U15 CPU chip || Ties crystal to clock input (pin 39) of U15 CPU ||
|-
|W2 / W3|| To the right of U25 RAM chip || Used to increase the ROM size ||
|-
|W4|| Below U31 (to the right of U25) || Used to increase the ROM size ||
|-
|W5|| Below U39 & U38 (PIA chip) || Used to apply +5v to SR14 resistor network ||
|-
|W6|| Below U30 & U27 || Used to apply +12v to SR14 resistor network ||
|-
|W7|| Below diagnostic LEDs || Country jumper. Remove for German text and settings, add for English text and settings ||
|-
|W8 / W9|| Below U24 (sound CPU chip) || Used to choose what to use as /RST for U24 sound CPU ||
|-
|W10 / W11|| To the right of 3 radial caps in reset section|| Choice of +18v (W10) or +12v (W11) for sound amplifier ||
|-
|W12|| A resistor below U10 PIA || Pull down resistor for E1 (pin 1) and E2 (pin 19) of U11 & U13 address line buffer chips ||
|-
|W13|| A resistor below U16 data line buffer chip || Pull down resistor for /E (pin 19) of U16 data line buffer chip ||
|-
|W14 / W15|| Below U29 || 1ms IRQ signal (W14 in) or 2ms IRQ signal (W15 in) ||
|-
|W16|| Below U27 || Ties XTAL (pin 38) of U15 CPU chip to ground || Only cut when using Hitachi 6808 or 6802 MPU at U15
|-
|W17|| Below U23 || Ties XTAL (pin 38) of U24 sound CPU chip to ground || Only cut when using Hitachi 6808 or 6802 MPU at U24
|-
|DS1|| Left of U13 || || Marked as DS1 on board (lower of 2 jumpers) - leave out
|-
|DS1|| Left of U13 || || Marked as DS1 on board (upper of 2 jumpers) - leave out
|-
|DS2|| Left of U13 || || Marked as DS2 on board (lower of 2 jumpers) - keep installed
|-
|DS2|| Left of U13 || || Marked as DS2 on board (upper of 2 jumpers) - keep installed
|-
|}

 

'''5764-12206-00 REV. A (Typically System 11B & 11C)'''

Typically installed jumpers are W1, W2, W4, W5, W7, W8, W11, W14, W16, W17 & W19.

{| class="wikitable"
!Jumper
!Location
!Purpose
!Notes
|-

|W1|| Below U15 CPU chip || Ties crystal to clock input (pin 39) of U15 CPU ||
|-
|W2 / W3|| To the right of U25 RAM chip || Used to increase the ROM size ||
|-
|W4|| Below U31 (to the right of U25) || Used to increase the ROM size ||
|-
|W5 || Above U25 RAM chip || Used with 2K x 8 6116 RAM at U25 ||
|-
|W6 || Above U25 RAM chip || Used with 8K x 8 6264 RAM at U25 || only 2K will be used from the factory
|-
|W7|| Below diagnostic LEDs || Remove for German text, add for English text || This jumper is not used in games with 16 digit score displays. Instead, install the U26 and U27 EPROMs for country and game.
|-
|W8 / W9|| Below U24 (sound CPU chip) || Used to choose what to use as /RST for U24 sound CPU ||
|-
|W10 / W11|| To the right of 3 radial caps in reset section|| Choice of +18v (W10) or +12v (W11) for sound amplifier ||
|-
|W12|| A resistor below U10 PIA || Pull down resistor for E1 (pin 1) and E2 (pin 19) of U11 & U13 address line buffer chips ||
|-
|W13|| A resistor below U16 data line buffer chip || Pull down resistor for /E (pin 19) of U16 data line buffer chip ||
|-
|W14 / W15|| Below U29 || 1ms IRQ signal (W14 in) or 2ms IRQ signal (W15 in) ||
|-
|W16|| Below U27 || Ties XTAL (pin 38) of U15 CPU chip to ground || Only cut when using Hitachi 6808 or 6802 MPU at U15
|-
|W17|| To the left of U24|| Ties XTAL (pin 38) of U24 sound CPU chip to ground || Only cut when using Hitachi 6808 or 6802 MPU at U24
|-
|W18 || Below U23 || Used with 8K x 8 6264 RAM at U23 || only 2K will be used.
|-
|W19 || Below U23 || Used with 2K x 8 6116 RAM at U23 ||
|-
|DS1|| Left of U13 || || Marked as DS1 on board (lower of 2 jumpers) - leave out
|-
|DS1|| Left of U13 || || Marked as DS1 on board (upper of 2 jumpers) - leave out
|-
|DS2|| Left of U13 || || Marked as DS2 on board (lower of 2 jumpers) - keep installed up to 11B
|-
|DS2|| Left of U13 || || Marked as DS2 on board (upper of 2 jumpers) - keep installed up to 11B
|-
|}
 

====Combining the System 9 Sound ROM Images====
Pinside user, "Dumbass", has created replacement System 9 MPU boards. One of the new things that he implemented in the board design is a daughterboard that can be mounted to the main MPU, which handles the speech duties. Therefore, the speech board with its sometimes problematic ribbon cable no longer has to be used. However, the sound and speech chip code now has to be combined together on a 27256 PROM, which is used at position U49.

The DOS/Windows "copy" commands to accomplish this for the System 9 games, are shown below (space formatting added for clarity).
The file [https://www.pinwiki.com/wiki/index.php/File:Pad.zip pad.732] is a special file and is not part of the released ROM images. It is a 4K (4096 Bytes) binary file filled with 0xff. Create it using your favorite hex editor, or download the file here: [[File:Pad.zip]]. Below is how the code should be concatenated for it to work properly. It is very similar to what is done for the System 9 code to be modified for a System 11 MPU.

Space Shuttle 
Checksum = 0000h


copy /b pad.732     + spch_u5.732 + spch_u6.732 + spch_u4.732 + cpu_u49.128 = cpu_u49.256 



Sorcerer 
Checksum = E67Fh


copy /b spch_u7.732 + spch_u5.732 + spch_u6.732 + spch_u4.732 + cpu_u49.128 = cpu_u49.256 



Comet 
Checksum = F9CCh


copy /b spch_u7.732 + spch_u5.732 + spch_u6.732 + spch_u4.732 + cpu_u49.128 = cpu_u49.256 

 

====Converting the System 9 ROM Images to work in a System 11 MPU====
It is easy to create System 11 compatible ROM images from System 9 ROMs. 
The DOS/Windows "copy" commands to accomplish this for the System 9 games, are shown below (space formatting added for clarity).

The file [https://www.pinwiki.com/wiki/index.php/File:Pad.zip pad.732] is a special file and is not part of the released ROM images. It is a 4K (4096 Bytes) binary file filled with 0xff. Create it using your favorite hex editor, or download the file here: [[file:Pad.zip]].

The System 11 CPU works out of the box with a 27128 EPROM at location U27. You may choose to double the ROM image, creating a 27256 image so that its size is consistent with the other System 11 U27 ROMs.

Remove jumper W8 and install jumper W9 on the System 11 CPU to enable sound to work properly. System 11 controls the sound reset via software.
 

=====Space Shuttle=====

copy cpu_u49.128 cpu_u21.128 
copy /b pad.732     + spch_u5.732 + spch_u6.732 + spch_u4.732 cpu_u22.128 
copy /b cpu_u20.128 + cpu_u20.128 cpu_u27.256 <=== This command doubles the 128K image into a 256K image

 

=====Sorcerer=====

copy cpu_u49.128 cpu_u21.128 
copy /b cpu_u21.128 + cpu_u21.128 cpu_u21.256 
copy /b spch_u7.732 + spch_u5.732 + spch_u6.732 + spch_u4.732 cpu_u22.128 
copy /b cpu_u22.128 + cpu_u22.128 cpu_u22.256 
copy /b pad.732     + cpu_u19.732 + cpu_u20.764 cpu_u20.128 
copy /b cpu_u20.128 + cpu_u20.128 cpu_u27.256 
copy /b pad.732     + cpu_u19.l2.bin + cpu_u20.l2.bin cpu_u20.l2.128 
copy /b cpu_u20.l2.128 + cpu_u20.l2.128 cpu_u27.l2.256 <=== This command doubles the 128K image into a 256K image 

Sorcerer is the only System 9 pinball game using 2 ROMs which make things complicated for repair. You can use the cpu_u20.128 image in a system 9 CPU jumpered for Space Shuttle or Comet. If you install W12 and remove W11 the CPU will be jumpered for a 27128 EPROM.
 

=====Comet=====

copy cpu_u49.128 cpu_u21.128 
copy /b spch_u7.732 + spch_u5.732 + spch_u6.732 + spch_u4.732 cpu_u22.128 
copy /b cpu_u20.128 + cpu_u20.128 cpu_u27.256 /b <=== This command doubles the 128K image into a 256K image 

 

===Sound Boards===

[[File:WMS Sys9 Speech 2532.JPG|300px|thumb|left|System 9 Speech Board Using 2532 PROMs (from Space Shuttle)]]
[[File:WMS Sys9 Speech Board.JPG|300px|thumb|right|System 9 Speech Board Using 2732 PROMs (from Comet)]] 
The speech board used in the three System 9 games, Space Shuttle, Sorcerer and Comet is essentially the same as the speech board used in System 6/7 games. However the speech board was enhanced during the Space Shuttle run. Four jumpers were added to accomodate either 2532 or 2732 EPROMs. When burning EPROMs, make certain which style of ROM is used. 

[[File:WMS Sys9 Speech Early Later.JPG|300px|thumb|left|System 9 Speech Board - Left unit is from early Space Shuttle, right is from later Space Shuttle]] 
Only the early Space Shuttles use 2532 EPROMs from the factory. Later Shuttles, Sorcerer and Comet use 2732 EPROMs. The later speech board is backward compatible. If using such a board, either 2532s or 2732s can be used for the first two System 9 games (or System 6/7 games), provided that the jumpers are set for the appropriate EPROM. 

In addition to the speech board generating speech sounds, it mixes the sound and speech signals via the potentiometer on the speech board.
 

[[Image:WilliamsSystem11BackgroundSoundBoard.jpg|500px|thumb|left|Background Sound board as found in High Speed]]
[[File:WMS D-11197 Road Kings Sound.JPG|500px|thumb|right|D-11197 Background Sound board as found in Road Kings]]
[[Image:WilliamsD-11297BackGroundSoundBoard.jpg|500px|thumb|left|D-11297 Sound board as found in Pinbot, fully populated]]
[[File:WMS D-11298 Pinbot Sound.JPG|500px|thumb|right|D-11298 Sound board as found in Pinbot. This version only has U4 populated (U19 is not). Uncertain why U19 is needed. Note that the CVSD "lane" of the board is not stuffed.]]
 
[[Image:System_11_Sound_Board.JPG|500px|thumb|left|D-11581 Sound board, not completely populated]]
[[Image:D-11581-F14.jpg ‎|500px|thumb|right|D-11581 Sound board, completely populated]]
[[Image:System11CSoundBoard.jpg|500px|thumb|left|D-11581 Sound Board, Completely Populated, with W10/W11 Jumpers. W10/W11 enable use of 512K sound ROMs as found in all System 11C games like Game Show, Dr. Dude, Pool Sharks, Rollergames, Diner, Radical, and Bugs Bunny]]
 
[[File:WMS D-12238 Jokerz Sound.jpg|500px|thumb|left|D-12238 Sound Board - specific to Jokerz! only]]
[[File:JokerzSoundBoardPinOut.png|700px|thumb|right|D-12238 Sound Board - specific to Jokerz! only - Connector PinOut]]
 
[[File:D11581SchematicIcon.jpg|300px|thumb|left|Use hyperlink at right to open D-11581 sound board schematics]]
[[File:D11581PartsDelta.jpg ‎|300px|thumb|right|Parts missing from partially populated D-11581 sound boards]] 
'''Link to:''' [[media:Audio_schem_11581.pdf|Schematics for the D-11581 sound board]]. 
'''Note:''' The parts shown at right represent the delta from a partially populated D-11581 to a fully populated D-11581. *The value of R13 will vary between 4.9Kohms (or 4.99Kohms) and 10Kohms. If R14 and R15 are 10Kohms, then R13 should be 4.9Kohms (or 4.99Kohms). If R14 and R15 are 20Kohms, then R13 should be 10Kohms.
 

===Power Supply===
[[Image:WMSSystem11PSPreBigGuns.jpg|300px|thumb|left|Pre-Taxi Power/Regulator Board. This power supply has had the header pins replaced and the 5V filter cap at C10 replaced. Note that this board has the 20A fuse for the GI still installed. This indicates that it is an early System 7 board. The fuse and it's holder should be replaced by a wire in all System 9 and 11 games]]
[[File:WMS_PS_5765-09466-01_rev_B.JPG|300px|thumb|right|WMS Power Supply - Revision B (Pinbot) Note that the top fuse holder just below the large 15000uF capacitor is broken on the left side]] 

These power supplies use obsolete parts at Q1 (SDS-201) and Q3 (SDS-202). The PCB print was used from Black Knight through Swords of Fury, with slight modifications. Up until and including Fire!, Q1 and Q3 were the obsolete SDS-201 and SDS-202. Starting with some Fire!, the board uses an MJE15030 at Q1 and an MJE15031 at Q3.

Part numbers printed on an SDS-201 at Q1 may be "6557" or "9057S".
Part numbers printed on an SDS-202 at Q3 may be "MDS60" or "9058S"
 

[[File:EarlyWMSPowerSupplyTraceRoutingErrorCloseUpAnnotated.jpg|300px|thumb|left|A closeup of the corrected trace routing error on a Fire! power supply board.]]
[[File:System11PSSchematic.jpg|300px|thumb|right|WMS Power Supply (High Speed) Schematics.]] 
There was a trace routing error on the original Fire! power supply pcbs. WMS cut the trace and used a jumper to correct the error. This error was corrected in the PCB layout at the start of "Big Guns" game production.
 

[[File:WMS_PS_5765-09466-01_rev_E.JPG|300px|thumb|left|WMS Power Supply - Revision E (Cyclone)]] 
With Big Guns and games after, the solenoid and lamp power power sections were no longer stuffed because they were relocated to the Aux Power board. The GI relay is also missing on these boards because discrete GI relay boards were placed under the playfield and/or behind the backbox lamp insert. By doing this, specific GI strings could be turned on/off versus "all or none" of the general illumination. This later board has the fuses only for display and 5V power. In a pinch, the unstuffed parts could be installed.

Starting with Big Guns, 2 100mA (1/10A) SB fuses are installed just to the left of the power supply in the backbox. These fuses protect the +100V and -100V circuits against shorts. Not all games used 1/10A slo-blo fuses. Some games used 1/8ASB fuses instead. This may have been due to 1/8ASB fuses being more readily available. 

The schematics for this power supply also list part numbers MPSD52 and MPSD02. The equivalent part number for an MPSD52 is a 2N5401. The equivalent part number for an MPSD02 is a 2N5551.
 

[[Image:System 11 Regulator Board.JPG|300px|thumb|left|Taxi and After Power/Regulator Board]]
[[Image:WMSPSSchematic1503015031.jpg|300px|thumb|right|Schematics for Taxi and After Power/Regulator Board]] 
This power supply was used from Taxi thru the remainder of the System 11 game production.
Note that Taxi used an early revision of the board. The placement of some of the resistors and zener diodes in the HV section of that board is different from later boards.
 

===50V Flipper Power Supply Board===
[[File:Williams50VPowerSupply.jpg|300px|thumb|left|50VDC power supply as used in System 11 (nothing) and 11A games (C-9939).]] 
System 11 (nothing) and System 11A games all used the 50V power supply board as pictured at left. This simple board takes 48VAC from the transformer secondary and uses a 35A/400V bridge rectifier to produce about 50VDC. The voltage is smoothed somewhat by a 100uf electrolytic capacitor. The transformer secondary is protected from a short in the bridge rectifier by either a 4ASB or a 5ASB fuse. Be sure to consult the manual for your game for the proper fuse value. Never overfuse a circuit.
 

===Auxiliary Power Driver Board===
At least two different revisions of the Aux Power Board were used in System 11B/11C games, pictured below.
[[File:WMS Space Station Aux Power Driver D-11813-552.jpg|400px|thumb|left|Auxiliary Power Board from Space Station (D-11813-552)]]
[[File:System 11 Power.JPG|400px|thumb|center|Auxiliary Power Board from Earthshaker (D-12247-568)]]
 

===Interconnect Boards===
[[File:WMS Space Station Interconnect.jpg|300px|thumb|left|Backbox Interconnect Board from Space Station]]
[[Image:System 11 Lamp Board.JPG|300px|thumb|right|Backbox Interconnect Board from Earthshaker]]
The interconnect board was essentially designed for ease of manufacturing and assembly. When Williams ultimately settled on using the same unit in all games, (give or take some parts here or there), modularity was apparent too. There was no longer a need to build complex, custom wiring harnesses between the CPU / driver board, backbox insert, and playfield. The interconnect board remedied this issue. 

[[File:BanzaiRunInterconnect.jpg|300px|thumb|right|Backbox Interconnect Board from Banzai Run]]Although the first four System 11B games, which include Big Guns, Space Station, and Cyclone use some form of an interconnect board, it wasn't until Swords of Fury when the interconnect board was used as a standard for the remaining System 11 games. The interconnect for Banzai Run (shown on the right) is completely different from anything else used by any game.

The interconnect board used in Swords of Fury uses a different part number, D-12185-559, compared to later System 11 games that used part number D-12313-x (x denotes the game's model number). They are not interchangable. Swords of Fury and Taxi had lane change switches still mounted on the cabinet. With later games lane change switches were removed and two optocouplers at position U2 and U3 (connected to the switch returns) were added to the board. The circuit is essentially the same as was used in early WPC games and enabled elimination of problematic physical lane change switches from the game. Starting with Jokerz, the third coupler at position U1 is used by the game software to check if the A/C relay on the aux power board is working. U1 transmits information back to the MPU as switch 2 on the switch matrix, provided that the A/C has energized.

The early versions of the interconnect board were located on the left side of the backbox and positioned vertically. The more common interconnect boards were located in the backbox positioned horizontally, just below the CPU board. The later board passes the following circuits:
*lamp general illumination circuits
*flipper power and ground
*lamp columns and rows
*switch columns and rows
*flash lamp power

What differentiates the board from game to game are the resistor values used for the flash lamp power circuits. In some cases, some of the resistors are left unpopulated and / or a zero ohm jumper is installed.
 

===Master Display Driver Board===
====System 9 (C-8363)====
[[File:WMS Sys9 SS Sorc Master Display.JPG|300px|thumb|left|C-8363 Early System 9 Master Display Driver Board]] 
This is the same master display that is used on all System 6A and System 7 games and is used on most System 9 games.
 

====System 9 (D-10749)====
[[File:WMS-D-10749.jpg|300px|thumb|left|D-10749 Late System 9 Master Display Driver Board]]
 

This master display board was introduced during the System 9 run and is mostly found in some of the later Comets that were manufactured. The major difference between this master display board (D-10749) and the previous master display board (C-8363) is the D-10749 board replaced the card-edge connectors used on the C-8363 with pin-type connectors.

Any System 9 machine that is wired with card-edge connectors to use a C-8363 master display board can be converted to use a D-10749 master display board by re-wiring to use pin-type connectors.

The following table shows the mapping of the connectors & pins from a C-8363 to a D-10749 to aid in this conversion:

{| class="wikitable"
!D-10749 Connector-Pin
!Function
!C-8363 Connector-Pin
!Notes
|-
|J8-1
|Strobe 16
|J5-14
|
|-
|J8-2
|Strobe 15
|J5-16
|
|-
|J8-3
|Strobe 14
|J5-17
|
|-
|J8-4
|Strobe 13
|J5-13
|
|-
|J8-5
|Strobe 12
|J5-12
|
|-
|J8-6
|Strobe 11
|J5-15
|
|-
|J8-7
|KEY
|
|
|-
|J8-8
|Strobe 10
|J5-2
|
|-
|J8-9
|Strobe 9
|J5-4
|
|-
|J9-1
|Strobe 8
|J5-3
|
|-
|J9-2
|Strobe 7
|J5-11
|
|-
|J9-3
|Strobe 6
|J5-10
|
|-
|J9-4
|Strobe 5
|J5-9
|
|-
|J9-5
|Strobe 4
|J5-8
|
|-
|J9-6
|Strobe 3
|J5-7
|
|-
|J9-7
|Strobe 2
|J5-6
|
|-
|J9-8
|KEY
|
|
|-
|J9-9
|Strobe 1
|J5-5
|
|-
|J10-1
|D1
|J7-4
|
|-
|J10-2
|C1
|J7-2
|
|-
|J10-3
|B1
|J7-1
|
|-
|J10-4
|A1
|J7-5
|
|-
|J10-5
|D2
|J7-8
|
|-
|J10-6
|KEY
|
|
|-
|J10-7
|C2
|J7-7
|
|-
|J10-8
|B2
|J7-6
|
|-
|J10-9
|A2
|J7-9
|
|-
|J10-10
|Comma 1 & 2
|J5-18
|
|-
|J10-11
|Comma 3 & 4
|J5-1
|
|-
|J10-12
|Blanking
|J7-3
|
|-
|J11-1
|GROUND
|J6-5
|
|-
|J11-2
|KEY
|
|
|-
|J11-3
| -100 VDC
|J6-6
|
|-
|J11-4
| +100 VDC
|J6-2
|
|-
|J11-5
|N.C.
|J6-4
|
|-
|J11-6
| +5 VDC
|J6-3
|
|-
|
| -100 VDC
|J6-1
|N.C. on D-10749
|}

====System 11 (Discrete Displays High Speed to Pin Bot and Banzai Run)====
[[File:WMS-D-10877.jpg|300px|thumb|left|System 11 Master Display Driver Board]]
[[File:D-10877WithAlternate7180.jpg ‎|300px|thumb|right|System 11 Master Display Driver Board with UDN7180 "daughter cards". Image courtesy of Aaron Gross.]]
The image at right shows "daughter cards" that replace UDN7180 chips, which were beginning to be become expensive and harder to obtain during the production run. The daughter cards use discrete transistors, much the same way as one version of the older System 3-6 Master Display Panel did. U9, U12, U13, and U14, originally UDN7180s, have been replaced on this board.
 

====System 11A (Millionaire / Early F-14)====
[[File:WMS-D-11414-1.jpg|300px|thumb|left|System 11A Millionaire Display Driver Board]]
This PCB actually came out of an early F-14 where they were recycled. Millionaire had it fully populated with additional lamp covers. The mounting brackets for the later D-11610 display changed so if you get a replacement for your F-14 first check which one is used in your game.
 

====System 11A/B (F-14 to Swords of Fury)====
[[File:WMS-D-11610.jpg|300px|thumb|left|System 11A/B 4 7 Digit Segmented Displays Driver Board]]
 

====System 11B (Taxi and Police Force)====
[[File:WMS-D-12232-2.jpg|300px|thumb|left|System 11B Display Driver Board D-12232-2 for 2 16 digit segmented displays + one external connector for a 7 digit display]]
Taxi and Police Force uses a D-12232-2 master display with J4 ribbon connector stuffed. If it's missing from the game, any other dual 16 digit alphanumeric can be used to make it work with Taxi and Police Force. You would need to add U3 (6118), resistors R10, 11, 12, 13, 15, 16, 17, 18 (10K) and connector J4. Jumper W1 should be added to connect the two center segments g' and m' on the lower display to form one large center segment g'. Jumper W2 should be added to light the comma on the jackpot display. Remove resistors R54, 56, 57, 60, 62, 64, 65, 67. The removal is these resistors makes the lower display essential a numeric display.
 

====System 11B (all other WMS 11B/C games)====
[[File:D-12232.jpg|300px|thumb|left|System 11B/C Display Driver Board D-12232-1 for 2 16 digit displays]]
 

====System 11C (Riverboat Gamber)====
[[File:WMS-D-12232-3.jpg|300px|thumb|left|System 11C Display Driver Board D-12232-3 for 2 16 digit displays and 2 connectors for 7 digit jackpot displays]]
Riverboat Gambler uses a D-12232-3 master display with all ribbon connectors stuffed. If it's missing from the game, any other dual 16 digit alphanumeric can be used to make it work with Riverboat Gambler. You would need to add U3 and U4 (both a 6118), resistors R10, 11, 12, 13, 15, 16, 17, 18 (10K) and connectors J4 and J6. Jumper W1 should be added to connect the two center segments g' and m' on the lower display to form one large center segment g'. Jumper W2 should be added to light the comma on the jackpot display. Remove resistors R54, 56, 57, 60, 62, 64, 65, 67. The removal is these resistors makes the lower display essential a numeric display. This display can also be used in Police Force and Taxi.
 

====System 11B/C (all Bally 11B/C games)====
[[File:WMS-Bally-L16-Display.jpg|300px|thumb|left|WMS Bally left side 16 digit Master Display Driver Board]]
 
[[File:WMS-D-12502-1.jpg|300px|thumb|left|WMS Bally right side 16 digit Master Display Driver Board]]
 

===Other Boards===
====Sound Overlay Board (C-13287)====
[[File:WhirlWindSoundOverlayBoard.jpg|300px|thumb|left|Williams "C-13287 Sound Overlay Solenoid Board" as found in WhirlWind.]] 
This relatively simple board was used on Whirlwind only to accommodate 5 additional solenoids (flashers or motors). The board logically sits between the System 11 MPU and the sound board, intercepting data normally sent directly to the sound board, and acting on that data only when specific codes are commanded. The board also relays data not specifically intended for it, on to the sound board.
 

====High Current Driver Boards====
[[File:WMS C-12493 High Current Driver Board.JPG|300px|thumb|left|Williams C-12493 High Current Driver Board from Earthshaker]] 
The high current driver board was used on Earthshaker to drive the shaker motor. It was used on several other Bally/Williams WPC games while designated different part numbers.
 

====Space Station Opto Position Board (C-11872)====
[[File:SpaceStationOptoBoardC-11872.jpg|300px|thumb|left|Williams C-11872 Space Station Opto Positioner PC Board Assembly]] 
This board is unique to Space Station. The "blobs" at Q1 and Q2 (both 2N3906s) in the picture at left are clear silicone caulk used to dampen vibration on the board. 
 

====Flash Lamp Resistor Board (Remotely Located)====
[[File:WMS Flasher Board Pinbot.JPG|thumb|300px|left|Flash Lamp Resistor Board (from Pinbot)]] 
The earlier design of flash lamp resistor board was mounted under the playfield within in the vicinity of the flash lamp circuit(s) that were powered by it. Each board had a maximum of 4 power resistors (2 per flash lamp circuit). The higher resistance resistor is 330 ohm 7 watt, while the lower resistance resistor is 5 ohm 10 watt. The purpose of the larger value resistor is to keep the flash lamp powered with minimal voltage. This keeps the flash lamp filament "warm", which puts less of a strain on the flash lamp. In turn, it is supposed to extend the life of the flash lamp. The smaller value resistor is used as a current limiting resistor which allows the solenoid voltage to be supplied to power the flash lamp. By powering the flash lamps with solenoid voltage, it eliminates the need for an additional, dedicated secondary transformer winding.

Note: If LED flash lamps are installed instead of incandescent lamps, the 330 ohm warming resistor must be removed from the circuit. If it's not removed the lamp will remain on, albeit not at full intensity.
 

====Flash Lamp Resistor Board (Centrally Located)====

<center>
<gallery widths=250px heights=380px perrow=3 caption="Flash Lamp Resistor Boards">
File:WMS Big Guns Resistor Board.jpg|<center>D-11814-557(Big Guns)</center>
File:CycloneBigGunsFlashlampBoardD-11814-564.jpg|<center>D-11814-564 (Cyclone)</center>
File:WMS_Space_Station_Resistor_Board_D-11814-552.JPG|<center>D-11814-552(Space Station)</center>
</gallery>
</center>
 

The flash lamp resistor boards were used on early System 11B games prior to the use of the "standardized" interconnect board. The board is located in a very awkward location. It is screwed to the back of the lower cabinet. Big Guns, Space Station, and Cyclone all have this board in this location. 

The resistors on the board "eat current" (limit current) since the 13V #89 flash lamps are wired to coil voltage (about 38VDC). When implementing this board, Williams chose to change the wire colors as the circuit passes through the board. Combined with the generally poor Williams System 11 documentation, this makes it tough to track down problems with non-working flash lamps. On the plus side, the wire wound cement resistors on the board do not fail often, probably due to the location of the board (resistor boards located under the playfield have high resistor failure rates due to heat and vibration). However, they obviously can fail. If there is power at the flash lamp, but grounding the flash lamp transistor does not light the lamp, the associated drive transistor may have failed. 

The flash lamp resistor boards were abandoned after Space Station. Flash lamp circuits and resistors became integrated into the "standardized" interconnect board.
 

====A/C Relay====
[[File:WMS Sys1WMS Sys11 Early AC Relay.jpg|300px|thumb|left|A/C relay board (early design ie. F-14, Pinbot)]]
[[File:WMS Space Station Aux Power Driver D-11813-552.jpg|300px|thumb|right|A/C relay placed on aux power driver board starting with 11B games (later design)]] 
Starting with Road Kings, System 11 games make use of what is referred to as an A/C relay. The purpose of the A/C relay was to drive twice the amount of coils and flashers by using half the amount of drive transistors. This process is commonly referred to as "multiplexing". Typically, if the A/C relay was at rest, the "A side" solenoids would engage. When the A/C relay was powered, the "C side" flashers would engage. However, there were sometimes solenoids multiplexed with other solenoids. 

For example, High Speed, which does not use an A/C relay, uses 8 discrete drive transistors to drive solenoids / flashers 1-8. Pinbot, which does use an A/C relay, uses the same 8 discrete transistors to drive solenoids / flashers. However, a total of 16 solenoids and flashers (A side and C side) are driven. By employing the use of an A/C relay, the System 11 MPU / driver board could be used for many more years without a "drastic" redesign. 

Initially, the A/C relay was located on a small circuit board under the playfield for System 11/11A games. Likewise, this A/C relay board did not have Molex header connections. Wires were directly soldered to the circuit board. Once the Auxiliary Power Driver Board was introduced with the System 11B platform (starting with Big Guns), the A/C relay was moved to this board for all subsequent System 11B/11C games.

In the example of the A/C relay shown in the pic on the left, the only way to discern that the A/C relay is the highlighted relay board is due to the wire colors soldered to the board.
 

====Diode Board for Multiplexed Solenoids====
[[File:WMS Sys1WMS Sys11 Early Diode Board. As Found.jpg|300px|thumb|left|Diode board as found mounted to the bottom of the playfield (Pinbot)]]
[[File:WMS Sys1WMS Sys11 Early Diode Board.jpg|300px|thumb|right|Diode board from Pinbot]]
[[File:WMS Space Station Aux Power Driver D-11813-552.jpg|300px|thumb|left|Diodes from diode board moved to aux power driver board starting with 11B games]]

 

====Motor Control Board (D-12045)====
[[File:D-12045.jpg|300px|thumb|right|Williams "D-12045" as found in Cyclone, Jokerz!, Riverboat Gambler and Diner.]] 
This board is used in 4 Williams Games
* Cyclone ... for the random award wheel
* Jokerz! ... for draw poker (the wheel has various cards pictured on it),
* Riverboat Gambler ... for the backbox roulette wheel and
* Diner ... for the clock hands count time.

The board uses a single U-opto to detect the wheel at the "home" position. The MPU implements an "open loop control system" stepping the motor to the desired position while assuming that each step was successful. The game flags an issue with the PCB/motor assembly when the software thinks that the wheel should be at the home position but the opto beam hasn't been broken by the opto interrupter on the back of the wheel.
 

===Flipper Coils===
[[File:WMS Sys11 Flippers.JPG|thumb|left|300px|Serial wound flipper coils as seen on earlier (pre F-14 Tomcat) System 11 / 11A games (pic from Pinbot)]]
[[File:WMS Serial Flipper Schems.JPG|right|300px|thumb|Wiring schematic for serial wound flipper coils]] 
Early System 11 and 11A games used serial wound coils. These coils only have a single diode on them.
 

[[File:Placeholder.jpg|thumb|left|300px|Placeholder for Parallel wound flipper coils as seen on later (post F-14 Tomcat) System 11A/B/C games (pic from xxxx)]]
[[File:Parallel_Wound_Flippers.jpg|right|300px|thumb|Wiring schematic for parallel wound flipper coils]] 
Later games (starting with F-14 Tomcat) used parallel wound coils, which have 2 diodes on them.
 

System 11 games use different parallel wound flipper coils dependent on flipper placement and application. Below is a chart of the flipper coils used, their wrapper color, and strength.

{| class="wikitable"
!colspan="4" |System 11 Flipper Coils
|-
!Part #
!Color
!Strength
!Notes
|-
|FL-11753 || Yellow || Weakest ||
|-
|FL-11722 || Green || Weaker ||24-600 series wound similar strength
|-
|FL-11630 || Red || Standard ||23-600 series wound similar strength
|-
|FL-11629 || Blue || Strongest ||
|}
 

===Accessing Bookkeeping, Settings, and Diagnostic Modes===
[[File:System11CoinDoorButtons.jpg|300px|thumb|right|Example System 11 Coin Door Buttons. The Advance button is missing it's black cap, and yes...that is a bit of soft drink spooge on the bracket.]]
The coin door buttons for system 9 and 11 games are shown at right. The function of the three buttons is (from left to right in the picture)...
*Reset High Score to Date
*Auto Up/Manual Down
*Advance

Function of the Reset High Score to Date is self explanatory.

The Auto Up/Manual Down (AUMD) button is interpreted by the game software in multiple ways. Starting from attract mode, if the AUMD switch is up, pressing the advance button causes the game to enter audits and adjustments mode. If the AUMD switch is down, pressing the advance button causes the game to enter diagnostic mode. With the AUMD button in the up position during many of the diagnostic tests, the next step in the test will be automatically entered. For example, display test will display each digit on the display in turn. Coil test will advance through each coil. A particular step of the test may be paused on by pressing the AUMD button down.

The Advance switch moves the diagnostic, audit, or adjustment to the next step (or previous step if the AUMD button is down, except in diagnostic mode).

When in adjustments mode, the credit button is used to zero, turn off, or turn on features. 
Note: One of the adjustment settings (adjustment 69 on High Speed for example) can be used to clear all of the game audits.

At the end of all diagnostic tests, the game will enter audits next, and then adjustments. To exit diagnostics, audits, and / or adjustments, either advance until the last adjustment, or simply turn the machine off.
 

===Transformer Power Selection Connector===
<center>
<gallery widths=350px heights=400px perrow=2 caption="System 11 Power Selection Jumpers">
File:WMS Sys11 Transformer Power Selection.JPG|<center>Typical power selection connection for a System 11 transformer - 115VAC (from Space Station)</center>
File:System11European220VSelection.jpg|<center>European power selection connection for a System 11 transformer - 220VAC. 1 - Black, 4 - White, 3/6 - Orange. ''Image courtesy of Chuck Sanderson''</center>
</gallery>
</center>
 

==Problems and Solutions==
===Sporadic Problems in General - System 9===
[[File:WMS Sys9 Headers.JPG|300px|thumb|left|Cracked Header Joints and Headers cut too deeply by factory on System 9 MPU]] 
Just like the previous Williams platforms, the System 9 platform is prone to cracked solder joints on the header pins. Likewise, Williams' board manufacturers had some tendencies to cut the header pins too short on the solder side. By cutting the pins too short, the cuts partially go through the solder meniscus. Cutting through the solder meniscus makes a solder joint less reliable, and it may prematurely fail over time. 

By having cracked solder joints and / or cut solder meniscus, sporadic issues may occur. To resolve a cracked solder joint issue, the best approach is to completely remove the old solder, and add new solder to the joint. Due to dirt and contaminants, simply adding solder to the existing joint is not sufficient. If the header pins are cut too short, an attempt to remove the solder and new solder can be made. However, in some instances the only resolution is to replace the header pin connector. It is recommended to use a [http://www.greatplainselectronics.com/Category-79.asp high quality replacement header].
 

===Power Problems===

====Bridge Rectifier Fuses====
[[File:WMS_Sys11_Fuses_Added_Before_Lamp_Solenoid_Bridges.JPG|left|thumb|300px|Fuse holders with 8 amp slo-blo fuses added to one of the AC inputs to each of the bridge rectifiers. (Pinbot)]]
[[File:System11AdditionalFuses.jpg|right|thumb|400px|The updated schematic (from High Speed) showing placement of additional transformer secondary fusing for solenoid and controlled lamp bridge rectifiers.]] 
A design flaw carried over from the earlier systems was the lack of fuses between the transformer secondary and the bridge rectifiers used for solenoid and controlled lamp power. In theory, if either of these bridges short, the main power fuse in the game should blow. But that is not always the case. If the primary power fuse fails to blow, the wiring between the transformer secondary and the bridge becomes the fuse. The resulting melted wiring is not pretty!

For games before Big Guns, interrupt one of the AC input lines and install a fuse holder with an 8 amp fuse installed (Williams opted to use an 8A normal blo, while Data East chose to install 8A slo-blo fuses). For games after Big Guns, an 8A normal blo fuse is already present between the transformer secondary and the controlled lamp bridge. As for the solenoid bridge, the addition of the auxiliary power driver board added fusing to protect this circuit. The 25V and 50V solenoid bridges were added to this board. Both bridges are fused with 4A slo-blo fuses.

A nice solution for this problem in the Inkochnito Bridge Board.
Surf on over to http://www.inkochnito.nl. Click on the Bridge Board image for more information.
 

====Alternate to the 12 position wafer connection====
[[File:DE-WMS-System11PSCN1Alternative.jpg|300px|thumb|left|The severely burned wafer connector at Data East equivalent of J1 here has been replaced with parts currently available. Pins 5 and 8 are not populated as those connections are not used.]] 
The 12 position "wafer" connector (CN1 or J1 for Williams games), can be replaced with currently available parts, shown at left. The original "wafers" are difficult to find and pricey.
Part number for the alternate connector is Molex 03-09-2121 or 03-09-2122.
 

====Rottendog Power Supply Missing 5v Failure====
If an aftermarket Rottendog WDP011C power supply is missing 5v, and other common causes of a missing voltage have been ruled out, then it's likely that the 5v regulator at U191 has failed. An available replacement is the Texas Instruments PTR08060 5v regulator from [https://www.mouser.com/ProductDetail/Texas-Instruments/PTR08060WVD Mouser] or [https://www.digikey.com/en/products/detail/texas-instruments/PTR08060WVD/1698955 Digikey].

====Rottendog Power Supply - Big Guns & Cyclone GI Comes On, Game Doesn't Boot====
If using the now obsolete Rottendog WDP011A power supply for Williams Cyclone or Big Guns, the +12v jumper may have to be moved from the bottom jumper location to the top. If a Rottendog equipped Big Guns or Cyclone turns on the GI lights, but the game doesn't boot, (only the 5v light on the CPU is lit), this is most likely the reason.

===System 11 MPU Jumpers===
Normally, jumpers on the MPU board do not require modification. The default configuration works for all System 11 game ROMs. However, there are 5 exceptions as follows...

W7 - Language Select Jumper

W7 is used only in games up to Cyclone. Games with 16 digit alphanumeric displays do not use this jumper. If installed, the game automatically reverts to English after losing the content of the RAM. If a different language is preferred, the "adjustments" menu provides an option to change the default language. Only a few early System 11 game ROMs contained multiple languages. For these games, if W7 is removed, the game generally defaults to German text.

Later System 11 games used language specific ROMs at U26 and U27.

W16 and W17 - Hitachi CPU select
[[File:System11Hitachi6802.jpg|300px|thumb|right|A Hitachi processor, installed at U15, with W16 cut (lower right of pic)]]
The W16 jumper, on original System 11 boards, is in a different location and used for backwards compatibility with system 9 boards. There is no need to change it.

On System 11A and later boards:

*W16 is connected to pin 38 (XTAL) of the 6802/6808 at U15, the CPU responsible for most game operation.
*W17 is connected to pin 38 (XTAL) of the 6802/6808 at U24, the CPU for the sound subsystem.

These two jumpers are used to indicate the manufacturer of the 6802/6808 microprocessor since the clock circuit of Hitachi microprocessors is different from the clock circuit of other manufacturers.

If U15 is a Hitachi microprocessor, remove or cut W16.
If U24 is a Hitachi microprocessor, remove or cut W17.
Otherwise, W16 and W17 should remain installed.

A Hitachi microprocessor can be used in System 9 and System 11 (nothing) MPU boards by simply lifting pin 38 out of the socket. Cutting the pin is not recommended since there may be need for that IC in another board.

W5/W6 and W18/W19 - RAM Type Select ONLY FOR SYSTEM 11B AND 11C

System 11B and 11C MPU boards provide the ability to use either a 6116 or a 6264 RAM at locations U25 and U23 (sound subsystem).

For U25...
*install jumper W5, remove W6 to use a 6116.
*Remove jumper W5, install W6 to use a 6264.

For U23 (sound subsystem)...
*install jumper W19, remove W18 to use a 6116.
*Remove jumper W19, install W18 to use a 6264.

Note: Removing both W5 and W6 from a System ll (nothing) MPU or from a System 11A MPU prevents the switch matrix circuitry from working correctly. One instance of this being done resulted in all switches reporting closure, counting backwards from 64 to 1 while in switch level test. Reference [https://pinside.com/pinball/forum/topic/williams-system-11-switch-levels-all-active this] PinSide thread.
 

===MPU boot issues===
====Steps for Repairing a Dead MPU====
[[File:WMSClockandE.jpg ‎|300px|thumb|right|A scope trace of the 4Mhz crystal input at pin 39 of the microprocessor (blue), and "E", the external clock at pin 37 of the microprocessor (amber)]]
Following is an ordered, disciplined process for reanimating a dead MPU board.

#Inspect for Alkaline Corrosion. Abate all corrosion properly before continuing.
#Test for valid 5/12/-12VDC power to the board.
#Verify correct jumpers are installed (or not installed) for Hitachi 6802/8 processors. More info [[Williams_System_9_-_11#System_11_MPU_Jumpers|here]].
#Note and address any error messages displayed upon boot (if any).
#Validate the ROM images.
#Test socketed chips in a known working board or chip tester.
#Verify a proper (4Mhz) clock signal to the 6802/8 processor at pin 39.
#Verify a proper (1Mhz) external clock signal at pin 37 of the 6802/8.
#Verify the reset circuitry is providing a valid "low and then high" reset signal at pin 40 of the 6802/8. Note that replacing the original reset circuitry with a modern reset generator will lengthen the time until the signal transitions to high. This is normal, and helps with debugging as the signal can be seen much easier.
#Use a logic probe to test for activity on the IRQ (pin 4), Address and Data pins of the 6802/8.
#Use a logic probe to ensure that the following bus buffer chips are correctly mirroring the input signals to the output signals:
##System 9: U1, U2 and U3 (address, R/W, and external clock), and U23 (data)
##System 11: U11 and U13 (address, R/W, and external clock), and U16 (data)
#Install Leon's test ROM to ensure that each 6821 PIA is receiving the correct chip select and data to produce valid outputs at pins 2 through 17. More information regarding use of Leon's test ROM can be found [[Leon_Borre_WMS_System_9_Repair|here]] for System 9 and [[Leon_Borre_Williams_System_11_Repair|here]] for System 11.

====Normal Game Boot Behavior====
[[File:WMS Sys9 Boot Display.JPG|300px|thumb|left|The 7-Segment diagnostic display on a System 9 MPU]] 
Normal MPU boot behavior for System 9 is to show a "0" in the diagnostic display on the MPU. The "0" will light during boot up, and continue to stay lit, as long as the game is on. 

[[File:Diagnostic7Segment.jpg|300px|thumb|left|The 7-Segment diagnostic display on a System 11(nothing) MPU]] 
Normal MPU boot behavior for games with a 7-segment display on the MPU is to show a "0" in the display. The "0" does not go away. The "0" will continue to be displayed under normal boot conditions. 

[[File:DiagnosticLEDs.jpg|300px|thumb|left|+5 VDC, Diagnostics, and Blanking LEDs as found on a System 11A, 11B, and 11C MPUs]] 
Normal MPU boot behavior for games with 3 LEDs instead of the 7-segment display on the MPU is for the "+5 VDC" LED to light first and stay on, then a split second later, the blanking LED will light and stay on. At the same time that the blanking LED lights, the diagnostic LED will begin to blink at a fairly rapid pace with a 50% duty cycle (equal durations of the LED being on then off). The blanking LED will continue to remain on. 

[[File:LEDDiagnosticsIn7SegmentGame.jpg|300px|thumb|left|+5 VDC, Diagnostics, and Blanking LEDs driven by game software expecting a 7-segment display as in High Speed]] 
If a System 11 MPU with 3 LEDs is installed in a game whose original board contained the 7-segment LED diagnostic display first introduced with the System 7 board set, the status of the 3 LEDs won't help much. The game software is attempting to display a "0" (assuming your game boots correctly) on a 7-segment display. Since the board contains just the three LEDs, the MPU circuitry merely lights all three LEDs as shown in the picture at left.
 

====MPU Boot Error Codes====
MPUs used in System 9 and 11(nothing) games display a code on a 7-segment display if an error is detected during boot. MPUs used in System 11A, 11B, and 11C games use the Diagnostic LED to blink a "codes". 

=====System 9 Games=====

The following table lists the error codes displayed on the System 9 MPU 7-segment display. 

{| class="wikitable"
!Code
!Description
|-
|<center>0</center> ||  Normal game boot with no problems detected. The game should be in attract mode.
|-
|<center>1</center> ||  CPU board locked up. Possible cause is memory protect circuit and U18 CMOS RAM "stuck bits".  That is, an actual failure of the CMOS RAM chip or the 6808 processor's ability to communicate error free with the RAM.
|-
|<center>2</center> ||  U20 Game ROM 1 faulty
|-
|<center>3</center> ||  U20 Game ROM 1 faulty
|-
|<center>4</center> ||  U19 Game ROM 2 faulty
|-
|<center>5</center> ||  Blanking signal stuck, coin door closed, memory protect circuit faulty, or the U18 CMOS RAM faulty
|-
|<center>7</center> ||  System failure. Occasionally, the following components can contribute to this problem: U21 (4MhZ crystal), components in the IRQ circuit, broken leads or failed C9 (22uF) in the reset section, or loosely seated ICs on the CPU board. Note that boot code "7" is the hardware default and characteristic of the CPU "reset" signal not complying with the proper low-to-high spec at pin 40.
|-
|<center>Other or no indication</center> ||  U20 Game ROM 1 faulty
|}

If the game is locked up, there may be a bad power supply. The 5 volt logic supply is the first one to check. Then, check the 12 volt supply, which is used to reset the CPU chip. Test for both DC (correct voltages) and AC (too much ripple on the DC circuit).

=====System 11(nothing) Games=====
The following table lists the error codes displayed on the System 11(nothing) MPU 7-segment display. 

Note: These error codes assume that either High Speed, Grand Lizard, or Road Kings ROMs are installed since those were the only three games shipped with this version of the MPU board containing the 7-segment display. Later System 11 MPU boards replace the 7-segment display with 3 discrete LEDs that indicate 5V presence, diagnostics execution, and blanking status. While the System 11(nothing) MPU board works fine with other/later game ROMs, the 7-segment display with later game ROMs doesn't provide useful information other than some confidence that the software is running correctly. With later game ROMs installed and the MPU booting properly, the 7-segment display will appear to alternate rapidly between "0" and "7" (as fast as the "Diagnostics" LED would be flashing in a System 11A through 11C MPU board).

{| class="wikitable"
!Code
!Description
|-
|<center>0</center> ||  Normal game boot with no problems detected. The game should be in attract mode.
|-
|<center>1</center> ||  CPU board locked up. Possible cause is memory protect circuit and U25 CMOS RAM "stuck bits".  That is, an actual failure of the CMOS RAM chip or the 6802 processors ability to communicate error free with the RAM.
|-
|<center>2</center> ||  U27 Game ROM checksum failure
|-
|<center>3</center> ||  U26 Game ROM checksum failure
|-
|<center>4</center> ||  not used
|-
|<center>5</center> ||  Blanking signal "stuck", or the coin door is closed, or the memory protect circuit is faulty, or the CMOS RAM at U25 has failed.
|-
|<center>Other or no indication</center> ||  General system failure. Check the 5VDC power supply as well as the integrity of game ROM 2 at U26.
|}

A zero displayed during Memory Chip Test (using the CPU board switch SW2) indicates that the blanking circuit is NOT functioning properly. 

An eight displayed during memory chip test (using the CPU board switch SW2) indicates that the blanking circuit is functioning properly. 

=====System 11A, 11B, 11C games=====
The following table lists the number of blinks of the DIAGNOSTIC LED, the error message that might be displayed, and the explanation (Source: Williams System 11A game manual. with embellishment). 
[[File:YT.png]] A video demonstrating an MPU indicating a U10 failure (8 blinks) can be found [https://youtu.be/Rhho5nO3YLU here].

{| class="wikitable"
!Code
!Message
!Notes
|-
|<center>0</center> ||  no message ||  Normal game boot with no problems detected. The game should be in attract mode.
|-
|<center>1</center> ||  U25 RAM FAILURE  ||  The RAM at U25 could not be used properly. This means that the RAM failed a read/write test at power up.  The game will remain in the current state and no other tests are performed until the game is turned off, then back on.
|-
|<center>2</center> ||  MEM. PROT. FAILURE  ||  This message means that either:    a) the Coin Door may be shut,    b) the Memory Protect Switch may be stuck in the ON position,    c) the memory protect logic is protecting the memory, or    d) a U25 RAM failure is occurring.
|-
|<center>3</center> ||  U51 PIA FAILURE ||  The PIA at U51 has failed.
|-
|<center>4</center> ||  U38 PIA FAILURE ||  The PIA at U38 has failed.
|-
|<center>5</center> ||  U41 PIA FAILURE ||  The PIA at U41 has failed.
|-
|<center>6</center> ||  U42 PIA FAILURE ||  The PIA at U42 has failed.
|-
|<center>7</center> ||  U54 PIA FAILURE ||  The PIA at U54 has failed.
|-
|<center>8</center> ||  U10 PIA FAILURE ||  The PIA at U10 has failed.
|-
|<center>9</center> ||  IRQ FAILURE ||  The interrupt request line is not working normally. It may be missing, stuck, too fast, or too slow.
|-
|<center>10</center> ||  U27 ROM FAILURE ||  U27 failed checksum (test 11 is skipped).
|-
|<center>11</center> ||  U26 ROM FAILURE ||  U26 failed checksum.
|}

All of the above failures (except #9) may mean that the device has failed but it may also mean that the 6802 microprocessor is unable to communicate adequately or properly with the device. For example, if the CPU is attempting to checksum the game ROM at U27, but one of the 8 data lines leading to U27 has been severed, the wrong data will be received by the microprocessor and the checksum test will fail even though the ROM is perfectly fine.

An U25 RAM failure can occur without actual 6116 RAM failure. One of the most common reasons why U25 RAM failure occurs is lack of power to the RAM chip. If the D1, 1N5817, diode shorts open, logic power will no longer have a pathway to the U25 RAM. However, if the D2, 1N4148, blocking diode is fine, and the battery holder and batteries are fine, power will be retained by the U25 RAM. Although, the batteries will die prematurely if D1 has shorted. Another reason why U25 is no longer powered by the +5VDC logic power is due to a severed trace either caused by a blunt object or battery corrosion.

An interesting side effect to the U25 RAM failure blink code is that the blanking LED will blink 10 times after the single blink from the diagnostic LED.

===== U51, U27, and possibly other boot message causes =====
[[File:System11SocketWornOut.jpg|300px|thumb|left|This OEM System 11 MPU socket is tired, worn out, and no longer provided solid contact with the ROM chip legs.]] 
System 11 MPUs booting with error codes, blinks, or messages on the display may need new sockets for the game ROM(s). In the picture at left, it's easy to see light right through the socket holes (note the brown background vs the white background). The metal female connections have fatigued over time and are no longer providing a solid mechanical connection to the ROM chip legs. Removal and replacement with a quality dual wipe or machine pin socket is advised.

This situation can cause a wide variety of boot problems including complete failure to boot, "U27 ROM failure" message, "U51 failure" message, etc.

Of course, the root cause could be due to many other reasons. The fairly complicated chip select logic outlined on sheet 4 of the System 11 MPU schematics could be the cause. The best way to attack the problem is with a logic probe, ensuring that the various chip select gates are yielding the intended logic states.
 

=====Five "Knocks"=====
Sometimes when turning a system 11 game on, the knocker will fire 5 times, causing most folks to wonder, "what the hey"?. All that knocking is designed to call the operators attention to a potential switch issue. Like the "credit dot" in later Williams games, including System 11 games that support the dot character, these 5 knocks mean that the game hasn't detected the closure of a particular switch (or switches) in a certain number of games. A message will be displayed indicating which switch or switches to examine.

Usually, this is an indication of a failed switch. Most switches get closed during the normal course of game play, long before the game's software counts up to the limit of "games played without closing each switch" and issues this indication.

To address this issue, use the coin door diagnostic panel buttons to enter switch edge test. Manually close the switch. If a switch closure is indicated, either normal game play failed to close the switch (you're not a very good player), or the switch is dirty. Closing a switch with your finger is different than closing a switch with a ball. Your finger generally pushes more firmly on the switch contacts. Clean the switch by dragging an old business card or piece of paper between the switch contacts while pinching the switch blades together with your fingers.

Caution: do not attempt to adjust switches with anything metal while the game is turned on. You will eventually short coil or lamp power to the switch matrix, damaging the MPUs switch matrix circuitry.

If closing the switch manually doesn't register in switch edge test, see the "switch problems" section of this Wiki.

=====System 11 "Adjust Failure" and "Factory Setting"=====
[[File:AdjustFailureMessage.jpg|300px|thumb|left|The typical "Adjust Failure" message on a System 11 game, coin door closed.]] 
The "Adjust Failure" message seen in the picture at left occurs when the game software can't make sense of the information contained in the battery backed RAM at U25. This could be because the RAM has failed, but this is unlikely. The vastly more common reason is that battery backup power has been interrupted to the games battery backed RAM because either the batteries are not installed, dead, or dying. Hopefully, they haven't made a mess of the board by leaking alkaline. See below. "Adjust Failure" is displayed under these conditions when the coin door is closed. 

Note that on some games (not certain if all) which use two 16-digit alpha-numeric displays, the message displayed will actually read "AJSTMENT FAILURE".
 
[[File:FactorySettingMessage.jpg|300px|thumb|left|The typical "Factory Setting" message on a System 11 game, coin door open.]] 
If the coin door is open under these conditions, the message "Factory Setting" is displayed.
 

=====Testing for Battery Backup Power at the RAM =====
[[File:U25_Ram_Test.jpg|300px|thumb|right|System 11: Game off. Meter set to DC volts. Black lead on game ground. Red lead on RAM pin 24.]] 
Testing for power at the RAM chip is easy.

Note: The CMOS RAM chip is located at U18 for System 9 and U25 for System 11.

#Set DMM to DC volts (or on less than 20V if not using an auto-ranging meter)
#Game off
#Black lead on backbox ground
#Red lead on pin 24 of the RAM as shown at right

Three AA batteries normally provide 4.5VDC. If you are reading some voltage, but not quite 4.5VDC, the batteries need to be replaced...and don't forget to move them off of the MPU board while you are at it.

Other causes for low or no battery backup power to the RAM chip are:

#Failed diode at D3 for System 9 or D2 for System 11 - This blocking diode normally prevents the 5VDC source from "charging" the alkaline batteries. This diode is a 1N4148.
#Failed diode at D2 for System 9 or D1 for System 11 - This blocking diode normally prevents the 5VDC battery backup power from powering parts of the board other than the RAM chip. In this case, the batteries will deplete rapidly. This diode is a 1N5817.
 

==== Cross Connecting Black and White Backbox Connectors ====
[[File:WMSSystem7PharoahConnectors.jpg|300px|thumb|left|The infamous System 7/9 connectors that can be cross connected. Yikes!]] 
In one of the biggest mistakes in pinball manufacturing, Williams used two identical 24 pin .062 connectors to connect cabinet and backbox wiring. The connectors are identical with the exception that one is black and one is white. During manufacturing, the wrong color connector was sometimes used. Bottom line: do not simply mate black to black and white to white. Instead, ensure that the wire colors going into one side of the connector are the same as the wire colors coming out the other side. This is the only foolproof method of avoiding the catastrophe of cross connecting circuits, causing certain damage to the MPU board.

For System 9 MPUs cross-connected, the damage can include, but is certainly not limited to, U41, U9, the game ROMs, and one or more 6821s. 

For System 11 MPUs cross-connected, the damage can include, but is certainly not limited to, U11, U31, U34, U35, U36, U44, the game ROMs, and possibly the 6821s.

[[image:YT.png]] A YouTube video demonstrating the repair of a System 9 MPU that was damaged in this way can be found [https://youtu.be/uoYKRJFnm-I here].

[[image:PinSideLogo.png]] An excellent disciplined approach to repairing a System 11 MPU damaged in this way can be found on PinSide [https://pinside.com/pinball/forum/topic/i-fried-my-system-11-cpu-board-now-what#post-7564730 here].
 

==== Relocating the battery from the System 9 MPU board ====
[[File:Leaking_Battery.jpg|200px|thumb|right|Yikes! What a pity...]]
Relocating the 3 AA batteries used to retain settings across power cycles to a location far away from the MPU board is always a good idea. Leaky alkaline batteries are the #1 killer of pinball boards. Sometimes the battery terminals don't look corroded, but the metal rivet which contacts the battery are actually missing. 

If "04 00" in the credit/match display is seen when the game is turned on, the game is in audit mode versus attract mode. Below are several reasons why the game has defaulted to audit mode.
* The batteries have failed and need replacing.
* The battery voltage is not reaching the U18 (5517-2) RAM. Check pin 24 of U18 for approximately 4.3v with the power on and 3.9v with the power off. Lack of battery backup power could also be due to an open D3 (1N4148) blocking diode. This diode is used to keep the CPU's logic power from charging the batteries.
* Blocking diode D2 (1N5817) has shorted, and the batteries are trying to run the MPU board when the game is off.
* There are other problems, such as a faulty 5517-2 RAM.

Simply removing the batteries will not allow a game to boot directly into "attract mode" when switched on. It also will not retain the settings such as the number of balls per game, the free play setting (obtained by setting maximum credits to 0), or high scores. However, a System 9 game will boot, and is still playable with the lack of batteries. To complete the boot sequence into attract mode, open the coin door, switch the game off, and then quickly back on. The game should leave audit mode, and go into attract mode. Credits would need to be added from the coin door, and if necessary, settings would need to be changed before starting a game.

The best option is to remotely locate the battery holder somewhere below all the other boards. This ensures that even if the remotely located batteries leak, they won't leak onto (or even drip onto) components of the MPU board. Use good quality alkaline batteries, mark the date of replacement with a Sharpie, and replace the batteries annually.

Adding a connector between the battery pack and the MPU board is a good idea. You can easily remove the battery pack from the board. Plus, if the batteries are forgotten, and do leak, the MPU board will not have to be removed to add another battery pack. A 3 x AA battery holder is the typical recommended replacement. If only a 4 x AA battery holder is available, a jumper can be soldered in the first battery position. Likewise, a diode can be placed in this position instead. This will prevent the batteries from being charged and 'cooked' by the game if blocking diode D3 on the MPU board fails. Keep in mind that adding a secondary diode to this circuit will decrease the voltage passing to the RAM memory by .5 to .7 volts (the typical voltage drop across a diode) if D3 is still good. Install a 1n4001 or 1N4004 diode in the position closest to the last + terminal (where the Red Wire exits). The banded side of the diode must be pointing in the direction of current flow, which is towards the (+) terminal marking on the MPU board, and away from the battery pack. 

[[File:WMS Sys9 remote bat.JPG|300px|thumb|left|Williams System 9 MPU Board]] 
On the System 9 MPU, solder the battery cables: Ground (Black Wire) to the Bottom Left pad and Positive (Red Wire) to the Top Right. 

After adding a remote battery pack, and while the board is still out of the game, it is a good practice to measure the battery pack's voltage at the (+) and (-) pads of the MPU board. All battery packs are pretty cheaply made, and failures "out of the box" are somewhat common. Checking to make certain the battery pack is functioning before reinstalling the MPU board in the game will save you some headaches.
 

[[File:WMS Sys9 D2 D3.JPG|300px|thumb|left|D2 and D3 Diodes Highlighted on a Williams System 9 MPU Board]] 
Since the MPU board is already out, another good practice is to check the D3 blocking diode. An open blocking diode will not allow the battery pack voltage to pass through to the non-volatile memory, and the newly installed battery pack will be ineffective. Conversely, a shorted blocking diode will allow the board's +5vdc logic power bus to pass through to the battery pack. This in turn, will charge the batteries, while the game is turned on. Alkaline batteries do not like being charged. They will heat up, and fail prematurely, (rather quickly). In worse cases, the new batteries can even leak or explode if charged. Testing the D3 diode is quick and easy, and worth the trouble checking it out. When in doubt, replace the D3 diode with a 1N4148, or add a secondary 1N4004 to the battery pack. Once again, if a secondary diode is added, it will decrease the voltage passing to the 5517-2 RAM memory, if D3 is still good. 

==== Relocating the battery from the System 11 MPU board ====
[[File:RemoteBatteryHolderSystem11.jpg|300px|thumb|left|A remote battery holder installed on a System 11 MPU. The purple wire is positive.]]
 

==== Installing NVRAM instead of batteries ====
[[File:NVRAM DIP.JPG|300px|thumb|left|RAMTRON DIP NVRAM installed on a System 11B board (Cyclone)]]
[[File:NVRAM SMT Adapter.JPG|300px|thumb|right|SMT adapted NVRAM installed on a System 11B board (Transporter The Rescue)]] 
Like most other pinball mpu boards, the battery-backed RAM can be replaced with a non-volatile memory RAM (NVRAM). Replacement RAM that can replace existing 6116 or a 6264 SRAM will be needed. DIP versions are becoming scarce, but there are other solutions available that use surface mount equivalents on a small circuit board that plug into the RAM's socket. Unfortunately, U25 is soldered in on System 11 boards from the factory, and would need to be removed to replace with NVRAM.

If installing any version of 6264 NVRAM on an 11B or 11C board, jumper W5 (located just above U25) needs to be moved to jumper W6. This jumper has a completely different purpose on 11 and 11A boards. 6116 NVRAM will have to be used with 11 and 11A boards, or else modification with wire wrap will be necessary. If 6116 NVRAM is used on 11B or 11C boards, jumper W5 does not have to be chaged.

There are several vendors who sell surface mount NVRAM on an adapter board. The adapter in the picture shown on the right was purchased from [http://www.pinitech.com/products/cat_memory.php Pinitech].
 

It has been documented that some variants of DIP NVRAM may need to have diode D1 replaced with a jumper or jumped around the diode, in order for the game to boot successfully. D1, a 1n5817 diode, has a very low forward voltage drop (about 0.2 volts) vs. the normal 0.4-0.6 volts most other diodes have. If replacing U25 with the memory RAM, some memory RAM will not unlock and allow writes until the voltage is 4.8 volts or so. The 1n5817 D1 diode is just enough to prevent some memory RAMs from allowing writes. To solve this, solder a jumper wire around the D1 terminals, or remove D1 entirely and replace with a jumper. Surface mounted NVRAM on an adapter board is not susceptible to this problem.
 

====Installing a Memory Capacitor Instead of Batteries====
[[File:WMS Sys11B Mem Cap.jpg|300px|thumb|left|Memory Capacitor Added to a System 11B MPU Board. The circled areas show an added jumper for the cap's negative terminal to ground and a jumper added in place of the blocking diode.]]
[[File:System11SuperCapInstalled.jpg|300px|thumb|right|An alternate method of adding a SuperCap. This style cap has two leads on the bottom of the cap. The negative lead of the cap is connected to battery ground via the red jumper wire. The necessary jumper across D2 is circled.]]
Another alternative is to install a memory capacitor. In essence, a memory capacitor is similar to a rechargeable battery, although, the likelihood of a memory capacitor leaking is greatly reduced compared to a rechargeable battery. When the game is turned on, it is charging the capacitor. When the game is turned off (this is where the memory cap slightly differs than a rechargeable battery) the memory capacitor slowly loses its charge over time. Therefore, it is imperative that the game periodically be turned on to allow the capacitor to charge up to its full capacity again. If a game will not be turned on for long lengths of time, a memory capacitor may not be the best solution. 

When installing a memory cap, two things will have to be done. It will be necessary to add a jumper to tie the negative lead of the cap to ground or positive lead to the non-banded side of the blocking diode. The picture to the left shows a jumper added to tie the negative lead of the cap to ground on a System 11B MPU board. Installation on System 11, 11A, and 11C boards is similarly performed. Secondly, the 1N4148 blocking diode (D2) will have to be removed, and replaced by current limiting resistor. A value from 100 ohms to 270 ohms will work. Once the capacitor is installed, and the board installed back in the game, it is a good idea to leave the game on for 15-20 minutes to allow the game to initially charge the capacitor to full capacity. After that, turning the game on monthly for about 10 minutes to allow the cap to recharge is a good idea. 
Note: Both photos show a jumper installed in place of the blocking diode. It is recommended that a limiting resistor be installed instead. 

Note: It has been determined that memory capacitors are not the most effective way to retain memory on System 11 games, if the game will not be turned on for long lengths of time.
 

==== Repairing Alkaline Corrosion ====
[[File:System11MPUDelicateTraces.jpg|300px|thumb|left|Closeup of the delicate traces under the battery holder of a System 11 MPU. Luckily, these cleaned up nicely.]]
[[File:System11CorrosionCropped.jpg|300px|thumb|right|Closeup of traces under the battery holder. Corrosion (darkened spots) has invaded beneath the solder mask (green coating) and is beginning to eat away at the copper traces.]] 
As can be seen at left, the traces on System 11 MPUs are very small. Not much alkaline damage is required to eat completely through these delicate traces. Unfortunately, there are a great many of these traces under the battery holder, and in a very vulnerable position to alkaline damage.

Also, to the left of the battery holder is the reset section of the MPU. That section is, on balance, much easier to repair than the delicate traces under the battery holder and at the 6821 PIAs immediately under the battery holder.

The advice often dispensed to deal with alkaline corrosion is to scrub the affected area with an acid such as vinegar, rinse with water, and then rinse again with isopropyl alcohol. This might work for light surface alkaline corrosion.

Unfortunately, often the alkaline will eat into traces beneath the solder mask or beneath chips. This dictates desoldering affected chips to remove the corrosion and repair traces. The alkaline interacts chemically with the solder making it very difficult to heat. Desoldering from the (presumably undamaged) back side of the board is much easier. Scuffing the alkaline damaged solder with a wire brush to remove the surface layer of damage is also helpful.

Once all damaged components have been removed, sand the affected area carefully with your choice of fine grit sandpaper. 220 grit works well. The objective is to remove the corrosion completely without destroying additional traces. All corroded areas must be addressed.

Next, rebuild traces as necessary. Corrosion tends to sever traces where the trace meets the solder pad of a part. Strong magnification and bright lighting helps. Either tin or conformal coat the bare copper and then reinstall parts.

[[File:WMSSystem11AlkalineDamage-1-Annotated.jpg|300px|thumb|left|Another closeup of the delicate traces near the battery holder of a System 11 MPU. These traces are too far gone for a repair to be considered reliable.]]
[[File:ReplacingSRCPartsSystem11.jpg|300px|thumb|right|A 9 pin, 4.7K bussed resistor network replacing SRC5. Pin 1 is on the right]]
[[File:System11AlkalineCorrosion.jpg|300px|thumb|left|A closeup of alkaline damage that has crept under the solder mask (the darker traces). Eventually, this corrosion will eat completely through the trace, making the board unreliable.]]
[[File:TypicalSRC.jpg|300px|thumb|right|The OEM resistor/capacitor network.]]

At the top of the board are a few "SRC" parts. These are 10 pin resistor/capacitor SIPs. The OEM part connects each driver line to a 4.7Kohm pull-up resistor connected to 5VDC. This guarantees that the signal is held at logic high until the PIA grounds the signal. The OEM part also connects each driver line to a high frequency noise filter capacitor (470pf). These parts are no longer available. A completely acceptable substitute is a 9 pin bussed, 8 resistor network (4.7Kohms) at positions SRC1 - SRC5 and SRC7 - SRC9. This part provides the pull-up resistor. In practice, the high frequency filter capacitor does not impact the displays.

The part is installed as shown in the picture at right, with pin 1 of the part connected to the right side which is labeled pin 1 in the board silkscreen. A 10 pin (9 bussed resistors) part may be used ONLY if the left most pin is clipped and not connected to ground.

An image of the original OEM part is shown at right.

Another example of alkaline corrosion can be seen in the picture on the left. This damage can be cleaned up, retinned, and the board placed back in service.
 

====Blanking Signal Stuck Low or Pulsing====
The blanking signal is a failsafe interlock with critical game functions including the display, sounds, lamp matrix, and solenoids. It prevents operation of each of these game features to protect the game circuitry in the event of a system failure. For instance, if the MPU is not running, and the lamp matrix is stuck on at a particular row or column, those parts will heat up quickly, and at the very least damage that circuitry. Coils remaining locked on could cause even larger damage to the game.

Each of the game functions listed above require the blanking signal to be high (not pulsing but always high) to operate. As an example, the solenoid driver circuitry logically "ands" the blanking signal with solenoid commands using a 7408 AND gates (at U17, U18, U19 and U20 for System 11 or at U56, U57, U60, and U61 for System 9).

Lack of blanking, with the blanking LED never lighting, means that the game program is not running. It either never started running, locked up due to an invalid ROM image or a problem with the data, address, control, or chip select signals on the MPU, or detected a problem with the RAM memory. 

[[File:System11Blanking.jpg ‎|thumb|left|300px|C58, a timing element for the 555 timer. Image Courtesy of Chris Hibler.]] 
In rare cases, C58 can fail (C12 for System 9). C58 holds the input to the 555 timer high between pulses from the display circuitry. This causes the blanking signal to pulse. A pulsing blanking signal can manifest in missing digits on the display, some lamp columns not being turned on, and possibly other issues. C58 is a 1uf tantalum capacitor. If the blanking signal is pulsing, replace C58. 

[[File:WMSSystem11Blanking.jpg|thumb|right|300px|Williams System 11 CPU Blanking Circuit. Image Courtesy of Chris Hibler.]]

The blanking circuit explained

#A properly executing CPU will update the displays by sending data to the display 6821 PIA at U51 for System 11 (and U5 for System 9) at regular intervals (every 2.8 msec).
#This action causes PA2 at pin 4 of the 6821 to pulse high periodically. The DE schematics call this signal "TG". It is merely called "blanking" in WMS schematics.
#The signal is inverted by the 7404 at U36 (U41 for System 9), in at pin 13, out at pin 12 (in at pin 11 and out at pin 10 for System 9).
#The coupling capacitor at C57 (C15 for System 9) can be ignored. These ceramic caps rarely fail.
#The signal is applied to the base (pin 2) of a 2N4403 at Q50 (Q6 for System 9) and to pin 2 of the 555 timer at 1C.
#The 555 timer is configured as a "missing pulse detector" meaning that if it does not detect the pulse that originated upstream at the 6821 PIA at U51 for System 11 (and U5 for System 9), the output of the 555 timer at pin 3 (and 7) will go low, which invokes blanking and protection of the system circuitry.

For the longer, more detailed explanation, [http://arcarc.xmission.com/Pinball/Stern%20Service%20Bulletins/sb/sb75.pdf Stern service bulletin 75] provides the "Blanking Circuit Theory of Operation" for Data East MPUs which are identical to Williams MPUs with respect to the blanking circuit.

When operating properly, the pins of the 555 timer will behave as follows (pin number, logic signal)
#low
#pulsing at the same rate as the 6821 PIA at U51 for System 11 (U5 for System 9), pin 4
#high
#high
#pulsing very rapidly. i.e. "ticking"
#high
#high

If [https://www.pinwiki.com/wiki/index.php/Leon_Borre_Williams_System_11_Repair Leon's System 11 test ROM] runs correctly on an MPU, this guarantees that all data, address, and control signals are working correctly. If blanking doesn't go high with a game ROM installed, ensure that the ROM images are valid. This is by far the most probable once Leon's ROM runs correctly.
 

====An Alternative to Rebuilding the Reset Circuit / Using a Reset Generator (System 9)====
[[File:System9ResetGenerator.jpg|thumb|left|300px|Reset section of a System 9 MPU board.]]
[[File:WMSSystem9ResetSection.jpg|thumb|right|300px|The image above shows the single jumper and the exact minimum parts required when using a reset generator on a System 9 MPU. The three electrolytic caps (all 100uf/25V), two inductors, and 5 ceramic caps (all .001uf labeled "102") are part of the 5, 12, and -12 volt power filtering circuitry. The D2, 1N5817 diode isn't needed if an NVRAM is used instead of a SuperCap or remote batteries. However, a jumper must be installed at D2 to power the NVRAM.]] 
The reset section of the System 9 MPU is almost identical to the System 11 reset section. As such, a modification similar to the mod outlined below can be performed on System 9 boards too.

#Remove resistors R6, R8, and R12. Really, all but R6 can simply be clipped off. One through hole at R6 will be used later.
#Remove transistor Q4
#Install a reset generator (MCP120-460GI/TO) where Q4 was removed. Orient the reset generator the same way that Q4 was oriented, matching the PCB silkscreen.
#Add a jumper from the upper leg of where R6 was removed (oriented as shown in the picture, upside-down from game installation) to the via that is about 1/4" southeast of the R6 connection.

That's it. Most of the rest of the reset circuit can be removed, but this provides no advantage since those parts are already "out of circuit" with this modification. After this modification is performed, the MPU board will no longer need the +12v to successfully boot. However, +12v is still necessary to power the sound amplifier on the board.

[[File:System9ResetMinimum.jpg|thumb|left|300px|Another image of the bare minimum part requirement when using a modern reset generator. The three electrolytic caps are all 100uf/25V. Note that the right most electrolytic cap is oriented backwards from the other two. The 5 ceramic caps are all .001uf and are labeled "102". These are sometimes called 1000pf ceramic caps.]] 
The MCP130 reset generator variant, with an internal 4.7K ohm resistor can be used too, but it isn't necessary. This is because the resistor at R170 provides an external 4.7K ohm pull up for the /RESET line.

Note that the reset generator has a longer reset delay than the OEM circuitry. At boot, the 7 segment LED will seem to show a "7" for a fraction of a second. It will turn to a "0" and remain "0" after that, assuming that the board is booting properly.
 

[[File:System9Inductor1.jpg|thumb|left|300px|Factory installed "zero ohm jumpers" where inductors are normally installed on a System 9 MPU board. Image courtesy of John Wart Jr.]]
[[File:System9Inductor2.jpg|thumb|right|300px|Factory installed "zero ohm jumper" where an inductor is normally installed on a System 9 MPU board. Image courtesy of John Wart Jr.]] 
Note that some System 9 MPUs shipped from the factory with zero ohm jumpers installed instead of inductors (see images left and right). When repairing alkaline corrosion, it's completely acceptable to replaced damaged inductors with jumpers.
 

====An Alternative to Rebuilding the Reset Circuit / Using a Reset Generator (All versions of System 11)====
[[File:WMS Sys11 Reset Section.JPG|thumb|left|300px|Reset section of a System 11A MPU board. Components to be removed are circled.]]
[[File:WMS Sys11 Reset Gen.JPG|thumb|right|300px|Reset section with reset generator and jumper installed.]] 

There is an alternative to the stock reset circuit on all versions of the System 11 MPU boards. A reset generator can be installed. Since the reset section of all versions of the System 11 MPU board is susceptible to battery damage, this is a very easy, and minimalistic way to rebuild the reset section. To do so, 4 components will need to be removed and a jumper installed. The following work will have to be done.

#Remove the Q39 transistor.
#Remove the following resistors - (from top to bottom as installed on the board) R58, R60 (these two are just below the Q39 transistor), and R69.
#Add reset generator MCP120-460GI/TO (also used on Data East MPUs) where Q39 was. Orient the reset generator in the same manner Q39 was oriented (pin 1 of reset generator will install in the bottom through hole). In other words, the "flat" side of the reset generator will face to the right.
#Add a jumper between the right pad of R58 and the right pad of R60 (both resistors have been removed).
 

This a very simple, and in some cases, cheaper alternative to repairing the existing reset circuit. After this modification is performed, the MPU board will no longer need the +12v to successfully boot. However, +12v is still necessary for the sound section of the MPU on most boards, except the 11B and 11C variants. Likewise, any of the other components in the reset circuit can be removed if desired. Please consult the System 11 MPU board BOM and schematics to determine exactly what components can be removed. The MCP120-460GI/TO reset generator can be purchased from Digikey or Mouser. The MCP130 variant with an internal 4.7K ohm resistor can be used, but it is not necessary. This is because resistor network SR19 pin 3 is an external 4.7K ohm resistor used to pull up the /RESET line.

Below is a prime example of where a reset generator is very handy. The amount of components replaced are reduced from 15-20 to 1. Note that because this was an 11B board (also true for 11C boards), there is no sound amplifier on the board. Hence, the +12v is not needed at all, and none of the parts related to the +12v were repopulated. If this were an 11(nothing) or an 11A board, the +12V inductor (can be replaced by a simple jumper), the W10/W11 jumper, and associated capacitors (C27, C28, and C29) would need to be populated.

<center>
<gallery widths=330px heights=210px perrow=3 caption="A Prime Candidate for Using a Reset Generator (11B MPU Board Shown)">
File:Sys11 Battery Rot.JPG|Battery alkali leeched into the reset section.
File:Sys11 Battery Rot WIP.JPG|Components removed, affected traces and pads cleaned and treated.
File:S11ResetSectionAnnotated.png|Components repopulated. The image above shows the single jumper and the exact minimum parts required when using a reset generator.
</gallery></center>

[[File:System11MinumunResetSection.jpg|thumb|right|300px|Another image showing the single jumper (string tied to it) and the exact minimum parts required when using a reset generator (System 11B/11C). System 11 (nothing) and System 11A must retain a few more parts.]] 
In the above gallery pics, note that some components in the reset area had to be reinstalled. These components are in the area of the reset section, but are not part of the reset circuitry. They are actually related to the game RAM, enabling CMOS power to reach the RAM and to control pin 18, the chip enable pin of the RAM. Without these parts, the MPU will not successfully boot. Instead, there will be a '''single blink code''' from the diagnostic LED indicating a U25 RAM error (a "1" will display on boards with the 7-segment display). If the game display is connected to the MPU board, a "U25 RAM ERROR" message will be displayed.
*D1 - 1N5817 diode
*Q40 - 2N3904 transistor (a 2N4401 was used in this case)
*R64 - 1 Kohm 1/4 watt resistor
*R65 - 10 Kohm 1/4 watt resistor
*R68 - 4.7 Kohm 1/4 watt resistor

And, once again, for a System 11 (nothing) or a System 11A MPU, both of which have onboard amplifiers in the upper left corner and require 12VDC power, be sure to retain or replace the following parts:
*L2 - 4.7uH inductor (or a simple jumper)
*C27 - .001uf/50V ceramic capacitor
*C28 - .001uf/50V ceramic capacitor
*C29 - 100uf/25V electrolytic capacitor
 

====Connecting a logic probe to the MPU Board====
[[File:WMS Sys9 Logic Probe.JPG|300px|thumb|left|Logic Probe connected to System 9 MPU Board]]
[[File:WMS Sys11 Logic Probe.JPG|300px|thumb|right|Logic Probe connected to System 11 (11A) MPU Board]] 

Of course, +5v and ground can always be acquired at any one of the bypass capacitors, which are located at most every chip, and simply labeled as "B".
 

==== Using a PC Power Supply For Bench Testing MPU Board====

[[File:WMS Sys9 comp PSU.JPG|300px|left|thumb|System 9 MPU connected to a PC power supply]]
[[File:WMS Sys11 comp PSU.JPG|300px|right|thumb|System 11 MPU connected to a PC power supply]] 
The 1J17 power connection is essentially the same for System 9 and all variants of the System 11 MPU boards. The ground connection can be attached to pins 1 through 3. The +5vdc connection can be connected to pins 4 through 6. -12vdc gets connected to pin 8 and +12vdc gets connected to pin 9.
 

===Game resets===
System 9/11 games are far more tolerant of low line conditions vs. the newer WPC games. Some things to check if the game is resetting are the usual culprits for this type of thing: connectors, filter capacitors, slam switches, bad chip sockets, etc. It is good preventative maintenance to replace the +5 volt filter capacitor on the power supply with a new one; most of these are 25+ years old and might be getting to the point of wearing out. Certainly replace them if you are getting resetting on your system 11 game. 

Most system 11 games give an indication that they've been slam tilted; if you're getting a "game reset" but you get a noise and/or a message on the displays beforehand, it is probably a slam switch issue vs. a true reset issue. Check all the slam switches in the game (usually the coin door is the main one, and also the ball roll tilt if present). 

===Solenoid problems===

====A/C solenoid/flasher problems====
[[File:System11AuxDriverBoard.jpg|400px|thumb|left|Williams System 11 Auxiliary Power/Driver Board, showing the A/C select relay, the clear "cube" at the top, center of the picture.]] 
The A/C select relay is a dual "make/break" (DPDT, double pole, double throw) relay that supplies power to either the "A-Side" or the "C-Side". It is located on the Auxiliary Power/Driver Board for games that use the board which was introduced with Big Guns and used on all subsequent games. For games prior to Big Guns, like F-14 Tomcat, the relay is probably located under the playfield. There are exceptions. High Speed and Grand Lizard do not use an A/C select relay. Road Kings uses one for a handful of solenoids, but this game did not follow the 1-8 solenoid convention which games after it adopted.

There are a couple ways that the A-Side / C-Side (A/C after this) relay circuit can fail. If the driving transistor (Q8 for Big Guns and later, Q7 for games prior to Big Guns, and located on the MPU board) shorts, the A/C select relay will be constantly energized, resulting in flashers firing when coils should have fired. If the driving transistor never switches the A/C select relay on, coils will fire when flashers should have fired.

Testing this behavior is easy. Use the diagnostic buttons to select solenoid test, and watch carefully to see what fires. The display will show the coil/flasher under test. The first 8 drive circuits tested will have an "A-Side" and a "C-Side". That is, circuits will fire in the following order: 1A, 1C, 2A, 2C, ... 8A, 8C. If the A/C select circuit is not working correctly, the same coil or flasher will fire twice in a row, once for the A side and once for the C side.

The A/C select relay is generally solenoid 12 in coil test. Placing the "Auto Advance" button in the up position, to repeatedly test solenoid 12, should allow you to hear the A/C relay clicking on and off.

If all of "one side" of the A/C select circuit is not working, the fuse supplying the voltage to that side may be blown. F2 (DC side of BR1) and F8 (AC side of BR1) fuse the 25V circuit. F4 (DC side of BR2) and F7 (AC side of BR2) fuse the 50V circuit. Another suspect is fractured solder joints on the A/C select relay. Reflowing these solder joints is simple. The A/C select relay is relatively heavy and it's weight puts stress on the solder connection at the printed circuit board.
 

[[File:System11A-CRelay-OKOnBothSides.jpg|300px|thumb|left|Williams System 11 Auxiliary Power/Driver Board A/C Select Relay showing normal, working switch contacts.]] 
It is rare for the A/C relay itself to fail. A possible source of trouble are the miniature contacts on the relay wipers. These are high power, high current, contacts that can be filed with a small point file to restore proper current carrying capacity. Under no circumstances should you ever use contact cleaner on these contacts, as this could cause a spark or fire to occur. Be careful to not mangle the contact wipers in an attempt to adjust them. Adjust with care. 99% of the time, these switch contacts need no maintenance at all.
 

[[File:System11A-CRelay-WeldedOnBothSides.jpg|300px|thumb|left|Williams System 11 Auxiliary Power/Driver Board A/C Select Relay showing "welded" switch contacts.]] 
Pictured at left is a disassembled A/C select relay with both the A Side and the C Side connected at the center contact pads. It's rare for one of these relays to "weld" itself to both sides. In this particular instance, the game would fire both the A-side coil and the C-side flasher at the same time.
 

Other failure points are the connectors and headers connecting the aux driver board to the main cpu/driver board. Fractured solder joints can affect the proper operation of the relay. It is good practice to replace, or at minimum, reflow the header pins, and to replace connector pins in their housings with new pins. System 11 games use .156 connectors in most locations.

And finally, the solder joints holding the A/C select relay to the board may fracture and cause loss of connectivity.

On a related note, if the flashers never illuminate during game or test, but the A/C relay physically engages, likewise the flasher lamps are good, and power is present at the lamps, suspect potential failure of the U1 (4N25) U1 optocoupler on the interconnect board. Starting with Jokerz, the U1 optocoupler on the D-12313 interconnect board was used to identify whether or not the A/C relay has engaged. Under normal operation, if the A/C relay has engaged, the voltage on the "C" side passes back to the optocoupler. In turn, there is a switch on the switch matrix, typically switch 2, which receives the signal from the U1 optocoupler. Note that U1 is on some previous games like Taxi, but it was not used.

====Special solenoid problems with RottenDog MPU board====
[[File:RottenDogMPUDIPSwitches.jpg‎|300px|thumb|left| RottenDog MPU with a red switch bank for selecting either Williams or Data East special solenoid implementation.]]
[[File:RDMPU004DIPSwitches.jpg ‎‎|300px|thumb|right| These DIP switches on this RottenDog are configured for a Williams game, even though they do not seem to match the PCB silkscreen.]] 
The RottenDog aftermarket MPU board can accommodate both Williams and Data East special solenoid implementations. This is accomplished with an 8 DIP switch bank, pictured at left. If set to the wrong game system, special solenoids will not operate properly in your game. Note: The DIP switch positions should be set the opposite of what you might think, based on the PCB silkscreen.
 

====Special solenoid problems====
[[File:SpecialSolenoidCircuit.jpg|500px|thumb|right|A typical special solenoid circuit]] 
Special solenoids on system 11 games are similar to the earlier variants used on all previous Williams' board sets. During gameplay/test modes the primary switches on the special solenoids (usually the pops and slings) are active, allowing actuation of those switches to fire the solenoids. This is done by grounding an input to a 7402 logic chip which in turn pre-drives a 2n4401 pre-driver transistor which drives a TIP122 Darlington transistor to fire the solenoid.

During solenoid test mode only, the secondary path to the 7402 is utilized instead to fire the solenoids. Since there are 2 paths to fire the solenoids, it is possible for a special solenoid to work in game/test mode, but fail the solenoid test due to a failed PIA or 7402 chip, and vice-versa.

'''Note:''' The System 9 circuit board architecture provides no physical way to control the special solenoids other than via the primary switch associated with the special solenoid device. Therefore, System 9 special solenoids are not activated during solenoid test.

If a special solenoid actuation switch locks on, the solenoid itself will lock on as well, (hopefully) blowing the associated fuse before blowing all or some of the TIP122/2N4401/7402 circuit. An inline fuse holder can be added to all special solenoids with a 1 amp fuse installed to help prevent this situation.

There is a 22uF capacitor and a 100 ohm resistor mounted across the special solenoid switches. The use of the capacitor and resistor creates what is called an [http://en.wikipedia.org/wiki/RC_circuit RC circuit]. The RC circuit is used to filter noise from the switch signal as well as to ensure a minimum pulse length for the solenoid activation. If using a polarized capacitor the positive terminal goes to the tie point with one end of the resistor attached. Should a special solenoid lock on, and the switch leaves are properly gapped, the issue may be a shorted switch capacitor or resistor.

Most system 11B games do not use the special solenoids in the same way. Special solenoid switches were added to the switch matrix instead, keeping all or some of the solenoid pulses under CPU control. It is easy to identify whether a game has CPU controlled special solenoids by inspecting the activation switches on the special solenoids. If there are both a primary and a secondary switch installed, the game operates via the direct-fire special solenoid setup. (Note that a secondary switch in the case of slingshots does not mean the normal 2nd switch all slings shots employ. Rather, it refers to a switch that only activates when the sling activates. It is installed near the pivot point of the sling arm underneath the playfield.) Also the secondary switches go to CPU connector J18. If nothing is connected to J18, then the special solenoids are CPU controlled. In games like BK2K only the kickers are CPU controlled while the pop bumpers still use the secondary switches. There was no rhyme or reason (no definitive start / stop point) which System 11B titles used special solenoid secondary switches, and which did not. Please refer to the game list [http://www.pinwiki.com/wiki/index.php?title=Williams_System_9_-_11#System_11B above] to determine which did / did not use the secondary switches.

[[File:WMSSystem11Zener1N5234.jpg|300px|thumb|left|6.2V Zener Diodes (ZR3-ZR8) that "protect" the board logic from shorts between the sense switches and coil power. Note: in this image, ZR7 and ZR8 have been replaced]] 
The usual cause of special solenoid circuit failure is a stuck switch that locks the associated solenoid on, causing the TIP-122 transistor to fail and the coil to get so hot that the winding insulation melts (causing a reduction of coil resistance, eventually approaching zero ohms). The zener diode (pictured, left) in the circuit may fail shorted as well. This will cause the associated coil to lock on even after repair of the other damaged circuitry since the zener is connected directly to ground. The shorted zener diode causes the 7402/2N4401/TIP122 circuit to react identically to a switch closure. Gack!

Note: If your game doesn't use the special solenoid switch inputs as in most System 11B games and all System 11C games (i.e. no connection at 1J18), then these zeners serve no purpose and may be clipped off.
 

====Unusual Solenoid Problems====
[[File:WhirlwindPinchedWire.jpg|300px|thumb|left|A pinched wire (white/brown) that causes a tough to find solenoid problem.]] 
The System 11 method of securing boards sometimes causes odd problems. The securing screws must be removed completely to remove a board vs the improved WPC method of sliding the board off the screw head via a "keyhole".

When securing the boards, it's important to ensure that wires aren't pinched behind the board. If a wire is pinched severely enough, the insulation will be displaced and the conductor will contact the backbox ground plain, which can cause a wide range of odd problems.

The wire in the picture shown at left happened to be the ground path for coil #1, the outhole kicker on Whirlwind. When the game was powered on, the coil would lock on until the blanking circuit became active. Pressing the diagnostic/audit coin door button would also result in the coil locking on. This was actually the A/C relay flipping to the coil side for diagnostics and providing power to the coils. The outhole coil had a path to ground via the pinched wire and would lock on. A game could be started and the coil appeared to work properly until any of the 1 through 8 coils were activated (when the A/C select relay would energize again). At that time, the outhole coil would fire at the same time as the other 1 through 8 coil.

This one was a real head scratcher!
 

===Flash Lamp Problems===
[[File:System11WarmingBoard.jpg|300px|thumb|left|System 11 (High Speed) warming board. Note that flashlamp power is no longer routed through this board. The orange wire connects to two flash lamps wired in series which are then connected directly to flashlamp power. The two black wires are ground. The gray-blue wire is the path to ground via a drive transistor.]]
System 9/11 flash lamps are driven by the same kind of circuitry that drives solenoids. Flashers are generally wired two in series (like old Christmas lights). If one lamp fails, the neither lamp will light. They are wired in series so that they split the DC voltage across two lamps, preventing them from burning out quickly.

To make the flashlamps "agile" (i.e. turn on rapidly) and to extend the life of the flashlamps, a "warming" circuit was employed which connects two series flashlamps to coil power via a 330 ohm 1 watt resistor. This causes the lamp filament to turn on very slightly, and to "warm up", ready for the power to find ground via a 1 ohm (5 ohm in System 11) resistor.

Over the years, these games have undergone "maintenance" to replace parts on the resistor board and have sometimes also been rewired, attaching the wires to different solder lugs on the flashlamp warming board.

Note: Warming boards are not shown in any of the System 11 documentation.

Note: If LED flash lamps are installed instead of incandescent lamps, the 330 ohm warming resistor must be removed from the circuit. If it's not removed the lamp will remain on, albeit not at full intensity.
 

===Lamp problems===
This may seem painfully obvious, but with any lamp problem, where all lamps in the same circuit are not lighting, first see if the associated fuse is blown.
 

====General Illumination Issues====
As a rule of thumb, general illumination (GI) lamp issues with System 9 or 11 games are dependent on the era of the game. The reason for this is GI circuits passed through different boards over the years. And, the majority of GI issues are typically due to the circuit board. Not so much the circuit board itself, but the junction between the header pin connections on the circuit board and the connector pins located in the female housings. 

It is extremely common for the header pins and / or the female connections related to the GI circuit to heat up, and in worse cases char or burn. When some of these games were in operation earning money, they could potentially be turned on for 8, 12, or more hours every day. If the connectors were compromised at some time in the game's life, the issues become compounded. 

The problem is a vicious cycle. If either side of the connector heats up, it creates more resistance. If it creates more resistance, it draws more current. If it draws more current, it heats up. This cycle continues until the connector blows the circuit's fuse (provided the proper fuse is installed and not by-passed), the connectors are so bad that the circuit no longer has continuity, or the connectors are replaced with new ones. It is recommended that both the male header pin connector be replaced and the associated pin connectors which connect to it. Replacing only one side of the connector is only asking for repeat problems down the road. Header pins rated for 7 amp are highly recommended as a replacement. If the 7A headers are used, the likelihood of the connector failing due to heat is greatly reduced. Likewise, the use of Molex Trifurcon connector pins are recommended. 

Another prevalent problem is the failure of the relay board or the relay board connectors. GI relay boards are typically found under the playfield and on the back of the lamp insert panel. The job of the relay board is to switch the GI lamps on/off for special lighting effects. Over many years of operation, the solder joints on the connector may fracture. Although it is more common for the male/female connectors to burn badly. Repinning these connectors, as is typical for GI connectors, is the prescribed fix. 

=====Games From Space Shuttle to Fire!=====
[[File:WMS Sys11 GI Circuits.JPG|300px|thumb|left|Typical System 9/11 Power Supply with GI Drivetrain Notated]] 
During this time period, general illumination entered the power supply [1 / 2], was parsed, and exited the power supply as 4 separate circuits [4]. Although there were 4 discrete GI circuits with 4 separate fuses [5], all 4 circuits were turned on/off via one relay [3] located on the power supply. 

Note that the factory connection on the power supply for System 9 games differs than what is shown in the picture. Connections [1 / 2] do not exist on System 9 games, and only two wires are used to input the general illumination instead of four.
 

=====Games From Big Guns to Swords of Fury=====
[[File:Cyclone Interconnect.JPG|300px|left|thumb|The interconnect board from a Cyclone mounted to the left side of the backbox]] 

With all the games mentioned in this particular section, there were some design growing pains. Williams was creating a preliminary interconnect board, however, it was very different from game to game at first. Therefore, GI issues may occur at the power supply connections, the interconnect board connections, and / or at one of the discrete GI relay boards used. Since single-sided circuit boards were used for the GI relay boards, cracked solder joints where the relay is soldered to the board is possible in addition to the header pins.

A shown at the pic on the left, the general illumination headers, connectors, and connector housings have been changed out due to fatigue / failure. This is a common failure point on games such as Big Guns, Space Station, and Cyclone.
 

=====Games From Taxi to Bugs Bunny's Birthday Ball=====
The games included during this era used a somewhat standardized interconnect board located below the CPU board. The GI circuits coming directly from the transformer enter the board on the right side at connector J6. The top 4 wires are yellow and the lower 4 wires are yellow with a white trace. In actuality, the GI wires are only 4 wires, instead of 8 wires. Once the upper 2 wires reach the board, each of them are daisy-chained through the insulation displacement connector (IDC). Equally, the bottom 2 wires are connected in the same fashion. This was presumedly done to reduce cost, and decrease the life expectancy of the connection as a whole. 

[[File:WMS Interconnect BK2K GI Marked.JPG|left|300px|thumb|Williams Interconnect Board with general illumination wire colors marked. Interconnect board is from a Black Knight 2000]]
The most typical header connections that fail on the interconnect board are J6 (the GI input and return) and J7 (the GI output and return lines to the backbox insert). The purpose of the picture to the left is to easily identify what GI circuits pass through what connections. This will aid in attempting to check the continuity of your rework, whether only replacing just one of the header connectors or both. 

Please note that the wiring color codes for J6 in the pic are not the incoming wire colors. The wiring codes in the pic are illustrated this way to determine where the GI circuits disperse throughout the board. The game's schematics in the manual include this information too.
 

Keep in mind that discrete GI relay boards were still used during this time period. Dependent on the game, there may be one to three discrete GI relay boards used. Again, since single-sided circuit boards were used for the GI relay boards, cracked solder joints where the relay is soldered to the board is possible in addition to the header pins.
 

======Repairing the General Illumination Input Connector / Wiring======
[[File:WMS_Sys11_Butterfly_GI.jpg|thumb|300px|left|General Illumination input connector with looped (butterfly) wiring]]
[[File:Sys11 Interconnect GI Connection.jpg|thumb|300px|right|One method for repairing the GI input connector]]
From the factory, only 4 wires total were connected to the GI power and return input connector, which is located on the right hand side of the interconnect board. With only 4 discrete connections per wire from the transformer, 8 wires are needed to connect to the interconnect board. The top 4 wires are yellow and the lower 4 wires are yellow with a white trace. To increase 2 wire connections to 4 wire connections, the wires connect to the IDC connector via one connector pin, pass through that connector pin, and loop back to another connector pin. In doing this, the life expectancy of the connector and the header pins on the interconnect board are reduced (too much current for these connections to maintain over their lifespan). The end result is typically burnt connector pins, housings, headers, and in some cases, the interconnect board too.

To resolve the burnt connection issue, the header pins on the interconnect board should be replaced with new ones. Preferably 7A higher current rated header pins. As for the harness side, the housing should be replaced too, and Molex Trifurcon crimp pins used within the housing. To compensate for the extra wires needed, each of the input wires will need a "Y" junction soldered in place. To do so, take a small piece of wire approximately 4" - 5" long. In the middle of the small piece of wire, carefully strip the insulation, leaving about 1/4" of exposed wire. Place a piece of heatshrink on the single incoming wire. Then, bend the small piece of wire at its center where the insulation is stripped, until both ends leads are nearly parallel with one another. Take the incoming wire, and solder it to the exposed wire in the center. The end result will look like a rudimentary "Y". Pull the heatshrink over the junction, and that's it. This needs to be done for the remaining 3 wires.

In addition to the wire modifications, you can also do a board modification. The J6 connector on the right side can be burned to a crisp. Often lifting pads under the printheader. To repair this you can add a jumper wire to the top 4 traces, connecting pin 1-2-3-4 together. This can also be done for the bottom 2 traces, connecting pin 6-8 together, but you are still missing pins 5 and 7 to be connected to 6 and 8. Turn the board over and solder a jumper over pins 5 thru 8. The same can be done for pins 1 thru 4. Now you have the best possible connection.
 
<center>
<gallery widths=300px>
file:Bally_interconnect_board_Dr_Dude_1.jpg|Dr Dude Interconnect Board with Modification
file:Bally_interconnect_board_Dr_Dude_2.jpg|Dr Dude Interconnect Board modification details (front)
file:Bally_interconnect_board_Dr_Dude_3.jpg|Dr Dude Interconnect Board modification details (back)
</gallery>
</center>
 

====Controlled Lamp Issues====
=====Lamp Columns or Rows from n to 8 Inoperative=====
[[Image:BrokenSIPResistorLampMatrixColumn.jpg ‎|300px|thumb|left|A broken SIP resistor, causing lamp matrix columns 5, 6, 7 and 8 to fail.]]
[[Image:BrokenSIPResistor.jpg ‎|300px|thumb|right|The same broken SIP resistor after removal.]] 
 

=====Lamp Sockets=====
Failed lamp sockets are not very common with System 9-11c games. If a specific lamp will not illuminate, spinning the lamp socket canister or solder tab can resolve the issue in some cases. One thing to keep in mind is that all controlled lamp sockets have a diode soldered to two of the lamp socket tabs. Due to this, the legs of the diode can get pressed against other leads on the lamp socket resulting in an electrical short. The end result may be a lamp which shines more brightly than other lamps in the same column or row, or a whole lamp column or row will illuminate dimly when they shouldn't be lit at all. The resolution is to inspect all associated lamps in the column or row, and look for solder tabs or diode legs touching where they should not be. 

=====Lamp Boards=====
Starting with Pinbot, Williams introduced lamp boards. Lamp boards were used in areas where lamp inserts were positioned too closely together, and it did not make logical sense (or it was not physically possible) to use individual lamp sockets. With subsequent games, lamp boards were used whenever lamp inserts were "nested" in groups. This trend was presumedly done to save on assembly and production costs. One benefit of lamp boards is that bulb replacemnt became easier in most cases. A simple turn of the twist lamp socket (WMS # 24-8767), and the 555 bulb could be removed. 

[[File:WMS Sys1WMS Sys11 Early Lamp Board.jpg|300px|thumb|left|Early direct solder lamp board as seen on Pinbot - the large color matrix below the top and right colored targets]] 
The first generations of lamp boards had the lamp column and row wires soldered directly to the board. On one hand, this is beneficial, because there is one less mechanical connection used in the lamp circuits. On the other hand, it makes it more difficult to remove the lamp boards completely from the game to clean and / or service. On the plus side, very little goes wrong with the direct wired lamp boards.
 

[[File:PCBMountLampDivot.jpg|300px|thumb|left|"Divots" in the connection pad of a "twist in" lamp.]] 
Two things that can fail are individual lamp circuit diodes or the solder pads can develop "divots", where the twist sockets make physical contact with the board. To overcome the divots, simply add a little solder, and carefully reflow the solder pads. Make certain not to apply too much heat...just enough to evenly flow the solder.
 

[[File:WPCPCBLampBoardHeaders.jpg|300px|thumb|left|The solder on these header pins has been reflowed nicely.]] 
With Fire!, Williams started using lamp boards with .156" header connections for the lamp column and row lines. This allowed for easy removal and service of the lamp boards. However, it introduced some new problems. Because the lamp boards used were single-sided, (this was presumably a cost analysis decision), the .156" header pins can develop cold solder joints and crack due to vibration. The problem can easily be rectified by removing the old solder from the header pins, and applying fresh, new solder. This style of lamp board is susceptible to the same issues (bad diodes and divots) as mentioned in the direct wired lamp boards section above.
 

===== Adjacent Columns or Rows Lighting Simultaneously =====
[[Image:WilliamsS11ShortedLampColumnDrives.jpg|300px|thumb|left|Column drive transistor tabs touching, shorted together. Here, lamp columns 3 and 4 would light at the same time.]] 
A problem seen fairly often is the tabs of either column drives or row returns touching, and therefore shorted and causing more than one column (in the picture at left) or row to light at the same time. If you have this issue, it's easy to quickly examine the column drive and row return transistors.
 

===== Lamp Matrix Row and Column Testing =====
The CPU logic for the lamp matrix can be tested by connecting a spare lamp using a jumper wire. The following sections show the separate procedures for testing the lamp matrix columns and rows. The example is on a Sys11A PinBot, but applies to all Sys11 CPU boards.
 

'''Testing the lamp matrix columns:'''

[[Image:lamp_matrix_test_sys11a_columns.jpg|600px|thumb|left|Jumper connection for testing lamp matrix columns.]]
 

Use the following procedure to test the TIP42 transistors that drive the lamp matrix columns. Note that a diode is not needed for these tests since it's function is to prevent interaction between the lamps in the matrix. In this test we are only connecting a single lamp at a time.

#Remove the backglass and open the insert to get access to CPU board connectors 1J6 (row) and 1J7 (column).
#Unplug connectors 1J6 and 1J7 (lower right corner of CPU board)
#Turn the game on and go to the "All Lamps" test in the Test/Diagnostic Menu. This is done by opening the coin door an pressing: MANUAL-DOWN, ADVANCE, AUTO-UP, ADVANCE x 2
#Clip one end of the test jumper to 1J6 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to 1J7 pin 1, the rightmost pin on the connector
#The test lamp should flash to indicate that the column driver is working.
#Repeat the test for the pins 2 through 9 on 1J7. There is no pin 5 as it is the key.

If a column doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test.

The following table shows the lamp number and driving transistor for each of the column pins.
{| class="wikitable"
!   Pin   
!Wire Colors
!Lamp number
!Transistor number
|-
|<center>1J7-1</center> || <center>Yel-Brn</center> || <center>1</center> || <center>Q66</center>
|-
|<center>1J7-2</center> || <center>Yel-Red</center> || <center>9</center> || <center>Q64</center>
|-
|<center>1J7-3</center> || <center>Yel-Orn</center> || <center>17</center> || <center>Q62</center>
|-
|<center>1J7-4</center> || <center>Yel-Blk</center> || <center>25</center> || <center>Q60</center>
|-
|<center>1J7-5</center> || <center>Key Pin</center> || <center> </center> || <center> </center>
|-
|<center>1J7-6</center> || <center>Yel-Brn</center> || <center>33</center> || <center>Q58</center>
|-
|<center>1J7-7</center> || <center>Yel-Blu</center> || <center>41</center> || <center>Q56</center>
|-
|<center>1J7-8</center> || <center>Yel-Vio</center> || <center>49</center> || <center>Q54</center>
|-
|<center>1J7-9</center> || <center>Yel-Gry</center> || <center>57</center> || <center>Q52</center>
|}

'''Testing the lamp matrix rows:'''
[[Image:lamp_matrix_test_sys11a_rows.jpg|600px|thumb|left|Jumper connection for testing lamp matrix rows.]]
 

Use the following procedure to test the TIP102/122 transistors that drive the lamp matrix rows.

#Remove the backglass and open the insert to get access to CPU board connectors 1J6 (row) and 1J7 (column).
#Unplug connectors 1J6 and 1J7 (lower right corner of CPU board)
#Turn the game on and go to the "All Lamps" test in the Test/Diagnostic Menu. This is done by opening the coin door an pressing: MANUAL-DOWN, ADVANCE, AUTO-UP, ADVANCE x 2
#Clip one end of the test jumper to 1J7 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to 1J6 pin 1, the rightmost pin on the connector
#The test lamp should flash to indicate that the column driver is working.
#Repeat the test for the pins 2 through 9 on 1J6. There is no pin 4 as it is the key.

If a row doesn't light or is stuck on, reference the lamp matrix table in the manual to identify the transistor to test. The following table shows the lamp number and driving transistor for each of the row pins.

{| class="wikitable"
!   Pin   
!Wire Colors
!Lamp number
!Transistor number
|-
|<center>1J6-1</center> || <center>Red-Brn</center> || <center>1</center> || <center>Q80</center>
|-
|<center>1J6-2</center> || <center>Red-Blk</center> || <center>2</center> || <center>Q81</center>
|-
|<center>1J6-3</center> || <center>Red-Orn</center> || <center>3</center> || <center>Q82</center>
|-
|<center>1J6-4</center> || <center>Key Pin</center> || <center> </center> || <center> </center>
|-
|<center>1J6-5</center> || <center>Red-Yel</center> || <center>4</center> || <center>Q83</center>
|-
|<center>1J6-6</center> || <center>Red-Grn</center> || <center>5</center> || <center>Q84</center>
|-
|<center>1J6-7</center> || <center>Red-Blu</center> || <center>6</center> || <center>Q85</center>
|-
|<center>1J6-8</center> || <center>Red-Vio</center> || <center>7</center> || <center>Q86</center>
|-
|<center>1J6-9</center> || <center>Red-Gry</center> || <center>8</center> || <center>Q87</center>
|}

=====Using MOSFETs in the Lamp Matrix Circuitry=====
Procedure by Marco Albus 
The original Williams (and Data East) lamp matrix circuitry dissipates a lot of heat through the 27 ohm current limiting resistors. Often, this part of the circuit board is badly heat damaged. Using modern MOSFETs (IRF9530, IRF9Z34N or FQP17P06), the heat (and power consumption) can be reduced substantially.

Once MOSFETs are substituted for the TIPs in the lamp driver circuit, it is possible to replace the 27 ohm resistors with simple jumpers or even leave the 27 ohm resistors in place if they are in good shape as the low resistance will have a negligible effect on the operation of the MOSFET. However, the problem with either of these is that the MOSFETs are driven by 18 VDC Source to Gate voltage which is dangerously close to the absolute maximum rating of the IRF9530 and IRF9Z34 of 20 VDC (this also holds true for Data East MPUs). The FQP17P06 has a higher Vgs rating (25VDC) than either the IRF9530 or IRF9Z34N - but you are still driving the part at over 70% of its absolute maximum. Typical uses for these MOSFETs drive them by about 10 VDC Source to Gate voltage (or -10V for P-Channel MOSFET's used here).

[[File:DEMOSFETSchematic.jpg|200px|left|thumb|Typical "Zero Ohm Jumper" implemenation (left), "Voltage Divider" implementation on right. Image courtesy of Marco Albus.]]
The schematics shown at left compare the widely used "Zero Ohm Jumper" implemenation with the "Voltage Divider" implementation that uses two 1K, 1/4 watt resistors to divide the source 18 VDC in half. Doing so drives the MOSFET with a 9 VDC Vgs. 

======MOSFETs Installed in a System 9 MPU Board======
[[File:WMS Sys9 Lamp Column FET Front.jpg|300px|left|thumb|1K resistors and IRF9Z34N FETs installed on the component side of the board.]]
[[File:WMS Sys9 Lamp Column FET Back.jpg|300px|right|thumb|1K resistors installed on the solder side of the board.]]
Parts Required 
*8 P-Channel MOSFETs (IRF9530, IRF9Z34N or FQP17P06)
*16 1K Ohm 1/4 Watt resistors

Procedure 
*Remove the TIP-42 transistors Q23-30
*Remove the 27 Ohm resistors R101, 103, 105, 107, 109, 111, 113, 115
*Remove the 2.2K ohm resistor network SR5
*In place of the 27 Ohm resistors, install 1K Ohm resistors
*In place of the TIP 42 transistors, install the P-Channel MOSFETs, oriented the same as the TIP-42s were oriented
*On the solder side of the board, install eight 1K Ohm resistors between the MOSFET gate and the 18VDC source.
 

======MOSFETs Installed in a System 11 MPU Board======
[[File:WMS Sys11 Lamp FETs Front.jpg|300px|left|thumb|1K resistors installed on the component side of the board.]]
[[File:WMS Sys11 Lamp FETs Back.jpg|300px|right|thumb|1K resistors installed on the solder side of the board.]]
Parts Required 
*8 P-Channel MOSFETs (IRF9530, IRF9Z34N or FQP17P06)
*16 1K Ohm 1/4 Watt resistors

Procedure 
*Remove the TIP-42 transistors Q52, 54, 56, 58, 60, 62, 64, 66
*Remove the 27 Ohm resistors R82-89
*Remove the 2.2K ohm resistor network SR16
*In place of the 27 Ohm resistors, install 1K Ohm resistors
*In place of the TIP 42 transistors, install the P-Channel MOSFETs, oriented the same as the TIP-42s were oriented
*On the solder side of the board, install eight 1K Ohm resistors between the MOSFET gate and the 18VDC source.
 

[[File:System11_mosfet.jpg|300px|left|thumb|A very clean alternate implementation with resistors on the component side. ''Image courtesy of PinSider DumbAss''.]] 
Shown at left is a very clean installation of all parts on the component side of the board. Note that the 1K resistors are situated such that the "body" of the resistor passes between the MOSFETs instead of the legs, thereby eliminating the possibility of a short.
 

===Switch problems===

====Diode and Switch Matrix Wiring Orientation on a Microswitch====
[[File:Submicro Switch Wiing.jpg|300px|left|thumb|Typical wiring for any Microswitch]]
First and foremost, all switches located in the switch matrix MUST have a diode. Secondly, the diode has to be installed in the correct orientation. If a diode is installed "backwards", the end result my be that all of the switches in that particular row get triggered or even stranger issues occur. Finally, the diode legs must not be connected to any of the other wires or terminals of the switch, or the switch will funk up the switch matrix.

Here is the correct orientation for the wiring and the diode on a microswitch. The white wire w/ trace and non-banded side of diode is connected to NC terminal. The banded side of diode is connected to common terminal. Finally, the green wire w/ trace is connected to NO terminal.

 

====Switch Columns or Rows from n to 8 Inoperative====
[[Image:BrokenSIPResistorSwitchMatrixColumn.jpg ‎|300px|thumb|left|A broken SIP resistor, causing switch matrix columns 5, 6, 7 and 8 to fail.]] 
 

====Switch Matrix Row and Column Testing====

The CPU logic for the switch matrix can be tested by simulating switch closures using a jumper wire on both System 9 and System 11 (all revision levels) MPUs.

[[Image:WMSSystem9SwitchMatrixTesting.jpg|300px|thumb|left|Testing the System 9 switch matrix, but jumpering from pins on 1J8 to pins on 1J10.]] 
As seen at left, testing the switch matrix rows and columns on a System 9 MPU is identical to testing on a System 11 MPU except for which connectors to use. The switch columns on the System 9 MPU at 1J8 are numbered right to left. The switch rows at 1J10 are numbered left to right. 1J9 is available (sometimes not stuffed) for opto switch processing, although this feature may never been used.

The System 9 switch matrix operates on 5VDC. The switch columns at 1J8 are "strobed" by being pulled to ground successively by the 6821 PIA. The switch columns are normally pulled high via a pull-up resistor. If the switch at the intersection of the column and row is closed, when the column is strobed, the row will be pulled low too. In this way, the processor knows which column it strobed, and which rows return that strobe.
 

The following sections show the separate procedures for testing the system 11 switch matrix columns and rows. The example is on a Sys11A PinBot, but applies to all Sys11 CPU boards.

'''Testing the switch matrix columns:'''

[[Image:Sys11_switch_matrix_test_col.jpg|600px|thumb|left|Jumper connection for testing switch matrix columns. This picture shows a diode which is not necessary for this test.]]
 

#Remove the backglass and open the insert to get access to CPU board connectors 1J8 (column) and 1J10 (row).
#Turn the game on and go to the "Switch Edges" test in the Test/Diagnostic Menu. This is done by opening the coin door an pressing: MANUAL-DOWN, ADVANCE, AUTO-UP, ADVANCE x 6
#Unplug connectors 1J8 and 1J10
#Clip one end of the test jumper to 1J10 pin 9, the leftmost pin on the connector
#Touch the other end of the jumper to 1J8 pin 1, the rightmost pin on the connector
#The display should report that switch 1 was actuated. The test may report the switch name, refer to the switch matrix table in the manual to correlate the name to the switch number.
#Move the jumper to 1J8 pin 2 and check the reported switch by comparing to row 1 in the switch matrix table
#Continue to test the rest of the pins on 1J8. There is no pin 6 as it is the key.

The following table shows the switch number that should be reported for each of the column pins.
{| class="wikitable"
!   Pin   
! Wire Colors 
! Switch number 
|-
|<center>1J8-1</center> || <center>Grn-Brn</center> || <center>1</center>
|-
|<center>1J8-2</center> || <center>Grn-Red</center> || <center>9</center>
|-
|<center>1J8-3</center> || <center>Grn-Orn</center> || <center>17</center>
|-
|<center>1J8-4</center> || <center>Grn-Yel</center> || <center>25</center>
|-
|<center>1J8-5</center> || <center>Grn-Blk</center> || <center>33</center>
|-
|<center>1J8-6</center> || <center>Key Pin</center> || <center></center>
|-
|<center>1J8-7</center> || <center>Grn-Blu</center> || <center>41</center>
|-
|<center>1J8-8</center> || <center>Grn-Vio</center> || <center>49</center>
|-
|<center>1J8-9</center> || <center>Grn-Gry</center> || <center>57</center>
|}

'''Testing the switch matrix rows:'''
[[Image:Sys11_switch_matrix_test_row.jpg|600px|thumb|left|Jumper connection for testing switch matrix rows. This picture shows a diode which is not necessary for this test.]]
 

#Remove the backglass and open the insert to get access to CPU board connectors 1J8 (column) and 1J10 (row).
#Turn the game on and go to the "Switch Edges" test in the Test/Diagnostic Menu. This is done by opening the coin door an pressing: MANUAL-DOWN, ADVANCE, AUTO-UP, ADVANCE x 6
#Unplug connectors 1J8 and 1J10
#Clip one end of the test jumper to 1J8 pin 1, the rightmost pin on the connector
#Touch the other end of the jumper to 1J10 pin 1, the rightmost pin on the connector
#The display should report that switch 1 was actuated
#Move the jumper to 1J10 pin 2 and check the reported switch by comparing to column 1 in the switch matrix table
#Continue to test the rest of the pins on 1J10. There is no pin 4 as it is the key.

The following table shows the switch number that should be reported for each of the row pins.

{| class="wikitable"
!   Pin   
!Wire Colors
!Switch number
|-
|<center>1J10-9</center> || <center>Wht-Brn</center> || <center>1</center>
|-
|<center>1J10-8</center> || <center>Wht-Red</center> || <center>2</center>
|-
|<center>1J10-7</center> || <center>Wht-Orn</center> || <center>3</center>
|-
|<center>1J10-6</center> || <center>Wht-Yel</center> || <center>4</center>
|-
|<center>1J10-5</center> || <center>Wht-Blk</center> || <center>5</center>
|-
|<center>1J10-4</center> || <center>Key Pin</center> || <center> </center>
|-
|<center>1J10-3</center> || <center>Wht-Blu</center> || <center>6</center>
|-
|<center>1J10-2</center> || <center>Wht-Vio</center> || <center>7</center>
|-
|<center>1J10-1</center> || <center>Wht-Gry</center> || <center>8</center>
|}

====Shorted or non-working switch column====

One or more failed switch columns can be caused by a failed column drive transistor (Q42 through Q49, all 2N4401s) or a failed 1K SIP resistor pack at SRC6.

The column drive transistor part was changed with the system 11B MPU. System 9 to 11A MPUs use 2N3904 transistors at location Q42 to Q49 with 1.5Kohm inline resistors (R71 through R78). These column drive transistors fail quite often as these MPUs age. These 2N3904 transistors can be replaced with 2N4401s.

When System 11B was introduced, the switch column drives were changed to 2N5550s with 470 ohm inline resistors. The more commonly found, and beefier 2N5551, is a good substitute for the 2N5550. Before replacing the transistor, be sure which kind the board uses. Some early system 11B MPUs were stuffed with 2N3904s despite the schematics indicating otherwise.

A broken SIP can also cause a switch column not to work. This usually happens with System 11 and 11A CPUs. With 11B WMS also changed the switch section layout and eliminated most of the SIPs. The likely candidates are SRC6 and SR11. In the case of SRC6, measure resistance between pin 1 and 2 to 9. If it's broken it's usually open after pin 3 or 4. This is a bussed 1K SIP with additional 470pfd capacitors connected to ground and practically NLA. Fortunately the caps are not needed because they are also mounted on the board so it can be replaced with a standard 9-8 1K SIP. Pin 10 which is the common ground for the caps is not used here. SR11 is a standard bussed 560 ohm 10-9 SIP. Here you measure resistance between pin 1 and pin 2 to 10. Be aware that two types of SIPs are used on the board: bussed and isolated. If you suspect a different SIP has failed check the schematics for the pin layout.

[[File:WMS-Brokensip.jpg|300px|thumb|left|A broken resistor SIP.]] 
Pictured at left is a broken resistor package similar to SRC6 but out of a System 11 master display. As can be seen, the part may look solid to the naked eye, but it's actually fractured.
 

====Ground Row Shorts====
[[File:WMSSystem11CrackedSR11.jpg|300px|thumb|left|Note the fracture in the SIP at SR11. The fracture became apparent only after desoldering the part.]] 
A possible cause for one or more ground row shorts (indicated by the game software on the score display during switch test) is a fractured resistor SIP at SR11 (a 560 ohm 10-pin bussed resistor network). SR11 is a pull-up resistor that is connected between each switch row return and 5VDC. If the return is not pulled up, that return will look like a low signal continuously, which the MPU interprets as a row ground short. Visual inspection of the SIP might or might not identify the cause of the problem. A better test is to remove the switch row return connector (J10) and probe each pin with a logic probe. The logic probe should indicate "high" for every pin.

Specific to the board pictured at left, a logic probe indicated that J10 pins 1, 2, and 3 were all high but the remaining pins had no signal at all. The fracture can easily be seen between pins 5 and 6 of the SIP (pin 4 isn't used) meaning that pins 6 through 10 were not connected to 5VDC and therefore not pulling the switch row return to logic high. Hence, the MPU declared a row ground short for rows 1 through 5. Note that the actual fracture can rarely be seen prior to attempted removal of the resistor network from the MPU board.
 

==== 4N25 Opto Couplers in the Switch Matrix====

[[File:4N25System11InterconnectBoard.jpg‎|300px|thumb|left|Three 4N25 Opto Couplers on a Williams System 11 Interconnect Board]]
System 11 games that include an Interconnect Board may use 4N25 Opto Couplers to detect power being applied to the flippers or to detect 28VDC being applied to the A/C relay (as in Rollergames). Pre-Fliptronic WPC games that use the -1 power/driver board also use 4N25 Opto Couplers.

These opto couplers are connected to the game switch matrix. Detecting these switches is most often used for lane change and for entering HSTD initials. If one of these functions no longer works, the 4N25 opto couplers should be considered suspect.
 

Fortunately, testing an opto coupler is simple using the diode test function provided by most DMMs. Set the DMM to diode test, compare results against those pictured below.

<center>
<gallery widths=300px heights=300px perrow=4 caption="Testing a 4N25 Opto Coupler">
File:4N25Internal.jpg|<center>The internal schematic of the 4N25. Pins 1 and 2 connect to an internal diode (LED). Pins 4 thru 6 connect to a PNP photo transistor.</center>
File:4N25Test3.jpg‎|<center>Testing the diode connected to pins 1 and 2</center>
File:4N25Test2.jpg‎|<center>Testing part of the photo transistor. Black on pin 5, red on pin 6</center>
File:4N25Test1.jpg‎|<center>Testing part of the photo transistor. Black on pin 4, red on pin 6</center>
</gallery>
</center>
 

====Opto Switches Not Registering with a Rottendog MPU / Driver Board Installed====
[[File:R-D_11C_Opto_Before.jpg|300px|thumb|left|Older Style Rottendog MPU Board]]
[[File:R-D_11C_Opto_After.jpg|300px|right|thumb|Modified Older Style Rottendog MPU Board]] 
If the opto switches are not registering at all in a game, and a Rottendog MPU board is being used, suspect that it is an older style board. This board can easily be upgraded though. U2 will have to be switched from a 74HCT240 to a 74HC240 chip, and RA5 will have to be changed from a 9-pin 4.7K ohm bussed SIP resistor network to a 9-pin 560 ohm bussed SIP resistor network.
 

===Display problems===
System 9/11 High Voltage Section Repair 
WARNING: This circuit uses high voltages. Don't continue, unless you are confident in your diagnostic abilities.
====High Voltage Issues With the Power Supply====
=====Check Voltages=====
If all displays are blank, your high voltage (HV) section may not be working.
On the Power Supply Board, use a DMM set to DC volts with the - lead grounded, probe the following connector
pins to determine if the HV section needs repair. If the display fuse, F1 is blowing,
you should remove the applicable display connector (with power off) before testing the voltages. Note that these are "loaded" voltages. If you are testing on the bench, or without displays connected, your measurements may vary.
 
If you have Power Supply D-11883 or D-12246: 
3J2 pin 1 = -100 volts DC 
3J2 pin 3 = +100 volts DC 
If you have Power Supply D-8345-xxx: 
3J5 pin 3 = -100 volts DC 
3J5 pin 4 = +100 volts DC 
If the test points are more than about 5 volts out of spec, then your HV section may
be malfunctioning (if you or a previous owner replaced Z2/Z4 with 1N4763A diodes to purposely reduce the display voltage, test readings in the 90's range would be normal). 

Check the table below for a solution.

=====Troubleshooting table=====
{| class="wikitable"
! '''Symptom'''
! '''Possible Cause'''
! '''Replacement'''
|-
| 0V ON BOTH +100/-100 lines
| Check F1
| 1/4 Amp SB
|-
| rowspan=5 | 0V on +100V line
| Open Diode D3
| 1N4004
|-
| Open Q2
| 2N5401
|-
| Shorted Zeners ZR1, ZR2
| 1N4730A and 1N4763A
|-
| Open Q1
| MJE340
|-
| Open R1
| 39k ohm, at least 1 watt
|-
| rowspan=5 | 0V on -100V line
| Open Diode D4
| 1N4004
|-
| Open Q4
| 2N5551
|-
| Shorted Zeners ZR3, ZR4
| 1N4730A and 1N4763A
|-
| Open Q3
| MJE350
|-
| Open R4
| 39k ohm, at least 1 watt
|-
| rowspan=4 | F1 1/4 Amp Fuse Blows
| Bad Capacitor at C1 and C3
| 100uF,150V
|-
| Shorted Display
| Display Glass*
|-
| Shorted UDN7180
| UDN7180*
|-
| Shorted UDN6118
| UDN6118*
|-
| +118V on +100V line
| Shorted Q1
| MJE340
|-
| -118V on -100V line
| Shorted Q2
| MJE350
|-
| colspan=3 | * ''located on display board''
|}

'''Displays Test With no Shorts'''
Once the displays are tested and shorts are eliminated, we can proceed with the HV section repair.

'''Replacing the components in the HV Section'''
Since there are not that many components, if you are having problems isolating the fault, a quick solution is to replace all the components in the HV section. If only one side (+ or -) is failing, it is possible to rebuild only the failing side. Check the parts section of the wiki to find suppliers, and get the replacement parts for one or both failing sides:

{| class="wikitable"
! '''Part'''
! '''+Side Part'''
! '''-Side Part'''
! '''+,-Location'''
|-
| Transistor
| MJE340 (or MJE15030)
| MJE350 (or MJE15031)
| Q1,Q3
|-
| Transistor
| 2N5401
| 2N5551
| Q2,Q4
|-
| Zener diode
| 1N4730A
| 1N4730A
| Z1,Z3
|-
| Zener diode
| 1N4763A**
| 1N4763A**
| Z2,Z4
|-
| Resistor
| 39k Ohm,1W
| 39k Ohm,1W
| R1,R4
|-
| Resistor
| 680 Ohm,1/4W
| 680 Ohm,1/4W
| R2,R5
|-
| Resistor
| 330k Ohm,1/2W
| 330k Ohm,1/2W
| R3,R6
|-
| Capacitor
| 0.1uF,250V metal polyester
| 0.1uF,250V metal polyester
| C2,C4
|-
| Capacitor
| 100uF,150V
| 100uF,150V
| C1,C3
|-
| colspan=4 | ** ''This is a 91V Zener to reduce the voltage to prolong display life''
|}

'''Remove and replace HV components'''

* Clip the old components from the board (make sure you have new ones first).
* Use one of the desoldering methods to remove solder from the holes.
* Stuff board with new components.
* Check for correct orientation on transistors, diodes and the large capacitor if you replace it.
* Leave a little space under components for air flow.
* Bend leads on components so they won't fall out when board is inverted for soldering.
* Double check that all the correct parts are in the correct places and properly oriented.
* Solder the parts to the board
* Clip excess off leads
[[File:System11PSPartIdentification.jpg|500px|thumb|left|A visual depiction of the parts in a System 11 high voltage section. Note that the legs of the MJE15030/MJE51031 are crossed as this power supply originally used OEM parts SDS-201 and SDS-202]]
 

=====Note on installation of MJE340/MJE350 replacement transistors=====
The MJE340/MJE350 is the heat-sinked transistor. On most Williams boards, this transistor pin configuration is not the same as the original part. It will need to be installed vertically with heat sink attached to the transistor only. The transistor will sit at about a 45 degree angle so the legs can be lined up to fit in the correct holes.

Check your board and insure correct orientation before soldering in place. Late versions of the System 11 series boards were designed to use the pin configuration of the MJE340/MJE350 transistors.

Do not mount vertically if the power supply is designed to use the pin configurations of the newer transistors!

[[Image:MJEInstall.png]]

=====Note on installation of MJE15030/MJE15031 replacement transistors=====
[[File:WMSSys11MJELegsCrossed.jpg|300px|left|thumb|High Voltage section with MJE15031 installed. Note the crossed legs on the left transistor.]]
[[File:WMS Sys11 PS Alt HV Transistor Pads.JPG|right|thumb|300px|Power supply with pads for both styles of HV transistors]]
The MJE15030/MJE15031 are rated for higher power and can be used instead of the MJE340/MJE350 (the MJE340/MJE350 are well within design specifications and are suitable replacements at 1/3 the cost of the MJE15030/MJE15031).

The MJE15030/MJE15031 pin configuration has the Base and Emitter reversed as compared to the MJE340/MJE350. In the image at left, the left transistor (MJE15031) shows one method of crossing the legs safely. The transistor's two left legs are shifted right on position. The third leg is then jumpered to the boards left through hole position. If you prefer not to cross legs, this transistor can also be mounted vertically, but this transistor would be facing the opposite direction as compared to the MJE340/MJE350 pictured above. 

There are some power supplies which have pads for both the SDS-201/SDS-202 or the MJE15030/MJE15031 style of transistors. In the pic to the right, the MJE15030/MJE15031 transistors are installed from the factory, but there are solder pads just below for installation of the SDS-201/SDS-202 transistors. If installing ME15030/MJE15031, the upper pads are used, and no leg crossing is required.
 

Ready to test 
To test the rebuilt power supply, return to the "Check Voltages" section of this guide. 
 
'''Other Resources''' 
The System 9-11 HV section of the PSU is very similar in design to the earlier System 3-7. So it will be worth reading through the [[Williams_System_3_-_7#Power_Supply_Issues|Sys 3-7 PSU Problems]] section entitled '''+/-100v Display HV Section of PSU''', for more detail. It also provides links to source complete HV rebuild kits which will normally cost under $10 shipped.

====Display Panel Problems====
=====Segment Identification=====
[[File:SegmentLetters.jpg|300px|left|thumb|Alphanumeric and Numeric Segment Identification.]]
 

=====Display Will Not Light=====
[[File:PlasmaBallTest.jpg|300px|left|thumb|Testing a high voltage plasma display with an inexpensive plasma ball]] 
If power to the display is correct, and the display was moved to a known working display panel position (if possible), it is possible that the display has outgassed. A plasma ball can be used to determine if a display glass is outgassed. 
[[File:YT.png]] A Youtube video demonstrating the use of an inexpensive plasma ball for this purpose can be found [https://youtube.com/shorts/GGftl3S_OWg?si=T5Cdzyovtar6_Han here]. 

=====Segments Light "In Sympathy" With Other Segments=====
[[File:ShortedSegments.jpg|300px|left|thumb|In this image, segment "b" and segment "k" light simultaneously, even though only one segment should be lit. The last two characters illustrate the issue clearly. Image courtesy of PinSider Pinball50.]] 
Internal shorts within a display glass can cause segments to light "in sympathy" with other segments. That is, segment "b" and segment "k", for example, will both light, when only one of the segments should be lit. Segment "b" will light whenever segment "k" is lit and segment "k" will light whenever segment "b" is lit. This is caused by an internal short within the glass. The short can be confirmed by removing the leads of the associated segments from the PCB and measuring resistance between them. The resistance should be infinite, or open.

In this case, there is no way to repair the glass and it should be replaced.
 

=====Commas stuck on (Players 1&2 or 3&4)=====
System 9: Check IC36 on the MPU (6821 PIA)

Pin 16 = Players 1 & 2
Pin 17 = Players 3 & 4

With the game in attract mode, check these pins with a logic probe. They should go low each time the displays turn off. if they stay high, the PIA is likely bad and will need to be replaced.

=====Display Fuse F1 Blows=====
Testing the UDN Chips 
If the display fuse is blowing, you should check the display board for shorts before connecting
a new or rebuilt power supply to the display board, as a shorted display or chip can damage a good power
supply. Remove the display board from the system. The display characters are driven by the two types
of UDN chips, the UDN7180 & UDN6118 (or UDN6184). Locate these chips (there are several)
on the board and test them with your DMM set to diode check. Clip your + (RED)
lead to the ground trace of the board. Probe the UDN chips as shown in the diagram.
If any shorts are read in the tested pins, the display should not be connected to the power
supply until the shorts are corrected.
[[Image:UDNReading.png|left]]
 

 Shorts Are Found in UDN Chip Test 
If a short reading is found in the tested pins (don't test the pins labeled 'dont care'), the UDN
chip should carefully be desoldered and removed from the board. Take care to preserve this chip,
as they are nearly impossible to find and expensive to replace. Now install an IC socket in its place.
Repeat the test with no chip installed. If the short is gone, then the UDN chip needs to be replaced.
If the short remains, then the display glass needs to be replaced.

=====Replacing Display Glass=====
[[File:WMS 7Digit glass change1.JPG|300px|left|thumb|Replacement glass installed with glass nipple in proper location]]
[[File:WMS 7Digit glass change2.JPG|300px|right|thumb|Replacement glass installed after circuit board was drilled to allow for glass nipple in different location]]
All plasma displays have a finite life expectancy. Display glass replacements were and are offered in several configurations. The differences in these configurations are mainly the placement or lack of a display "nipple" on the back of the glass. The glass nipple is what can pose as somewhat of a problem, when replacing a display glass. Williams did place a rather large hole in the display circuit board. However, the placement of the glass nipple has changed. To overcome this issue, a hole can carefully be drilled through the circuit board to allow for the glass nipple. When drilling, drill successive holes, starting with a small drill bit first, rather than drilling one large hole. This will reduce the chances of the circuit board "splintering". 

At one time, [http://www.pinballpcb.com/Displays.html pinballpcb.com] did offer replacement displays and / or just the replacement display circuit boards. Neither of these products are available anymore.

[[File:WMS 7Digit Repair.JPG|300px|left|thumb|Replacement glass installed]] 
Original display glass was secured to its circuit board with double-sided, high tack, foam tape. If this cannot be acquired, a simple method to secure an existing or new display glass is to use silicone caulk or RTV caulk. However, in following this method, the glass must be supported on the board until the caulk cures. Wrapping the glass with rubber bands is a great way to do this. Once the caulk is cured, just cut off the rubber bands.
 

====Logic States of Display Output Signals for a Working MPU Board====
These logic states were recorded from a System 11A board. This board was running Swords of Fury code in display test mode manually paused with all characters / digits on "8". This is for games with a 4 x 7 display board.

L=LOW, H=HIGH, P=PULSE

{| class="wikitable"
!IJ3 (pin)
!Logic State
|-
| 1 || L
|-
| 2 || P
|-
| 3 || P
|-
| 4 || P
|-
| 5 || P
|-
| 6 || None (Key)
|-
| 7 || P
|-
| 8 || P
|-
| 9 || P
|-
| 10 || L
|-
| 11 || L
|-
| 12 || H
|}

{| class="wikitable"
!IJ2 (pin)
!Logic State
|-
| 1 || P
|-
| 2 || P
|-
| 3 || P
|-
| 4 || P
|-
| 5 || P
|-
| 6 || P
|-
| 7 || None (Key)
|-
| 8 || P
|-
| 9 || P
|}

{| class="wikitable"
!IJ1 (pin)
!Logic State
|-
| 1 || P
|-
| 2 || P
|-
| 3 || P
|-
| 4 || P
|-
| 5 || P
|-
| 6 || P
|-
| 7 || P
|-
| 8 || None (Key)
|-
| 9 || P
|}

{| class="wikitable"
!IJ22 (pin)
!Logic State
!IJ22 (pin)
!Logic State
|-
| 2 || L || 1 || L
|-
| 4 || L || 3 || L
|-
| 6 || L || 5 || L
|-
| 8 || L || 7 || L
|-
| 10 || L || 9 || L
|-
| 12 || L || 11 || L
|-
| 14 || L || 13 || P
|-
| 16 || L || 15 || L
|-
| 18 || L || 17 || L
|-
| 20 || P || 19 || P
|-
| 22 || P || 21 || P
|-
| 24 || P || 23 || P
|-
| 26 || P || 25 || L
|-
|}
 

===Sound problems===
====System 9 Sound Problems====

=====Jumper Settings for a newer System 9 Speech Board=====
[[File:WMS Sys9 Speech Board jumpers.JPG|300px|left|thumb|Jumpers Circled on a Comet System 9 Speech Board]] 
As mentioned above, the System 9 speech board is essentially the same as the System 6/7 speech board. However, the newer speech board has jumpers added to increase the flexibility of EPROMs used. Either 2532 or 2732 EPROMs can be used. If using 2532 EPROMs, install jumpers W2 and W4, and remove jumpers W1 and W3. If using 2732 EPROMs, install jumpers W1 and W3, and remove jumpers W2 and W4.
 

=====Missing Sound or Speech Calls=====
To start a sound test, simply press the SW2 momentary switch at the bottom of the CPU board located between connections 1J16 and 1J17. Once SW2 is pressed, the CPU will cycle through all of the sound / speech calls continuously. Each System 9 game has a chart located in the manual, which lists the speech and sound calls made during test. The benefit of the chart in the manual is that it lists the ROM where a particular call originates. If a particular sound / speech call is not heard, the associated ROM listed for that call may be bad. 

Another result of speech calls missing is possibly a bad U2 or U3 on the speech board. Both of these chips are 1458 op-amps.
 

=====Isolating the CPU Sound from the Speech Board=====
Some of the sound / speech calls originate from the CPU board, while the remaining calls originate from the speech board. If after running a game through sound test by pressing SW2, and some sounds are missing or very low in volume, a good idea is to isolate the CPU board from the speech board. All of the sounds originated on the CPU board, leave the board via the 40 pin ribbon cable, and go to the speech board for mixing. Once mixed, all of the sounds and speech are then returned to the CPU board, amplified, and sent out to the speakers.

Much like the System 6/7 sound and speech boards, the sound can be isolated from the speech board for testing purposes. The System 6/7 Type 2 sound board uses a jumper at position W1. When jumper W1 is installed, the sound board can be diagnosed without the speech board installed. The equivalent with the System 9 CPU board is jumper W10. This jumper is typically not connected. However, when it is connected, the sounds originating from the CPU board can be heard.

If the sound is being tested and the speech board is '''not''' connected, audio volume will be very low. W10 must be installed to hear full volume.

Locate jumper W10 on the CPU board. W10 is located to the right of SW2 on the board. There should be two very small wires clipped on either side of W10, as if W10 was installed and removed. Connect an alligator test lead across the short leads of W10. If the short leads are not present, a short light gauge wire or wire wrap can be tack soldered to the solder pads of W10, or use a jumper wire to connect the lower legs of C32 and R76 which are just right of W10 (see pic, below). With a jumper installed at W10, some sounds should be heard when SW2 is pressed. Sound test, via the coin door diagnostic button is likely to provide sounds for all but sound 7, which is a voice call. If no sounds are heard, further troubleshooting must be performed.

<center>
<gallery widths=350px heights=350px perrow=3 caption="Adding W10 to a System 9 CPU Board">
File:WMS Sys9 W10 Jumper.JPG|<center>Locating jumper W10</center>
File:WMS Sys9 W10 Jumped.JPG|<center>Temporarily jumpering W10</center>
File:System9JumperTemporary.jpg|<center>Alternate for jumper W10</center>
</gallery>
</center>
 

====System 11 Sound Problems====
System 11 games are known to "hum" a bit. The "hum" is caused by electromagnetic interference from the lamp matrix insinuating itself on the sound circuit. To minimize the interference, ensure all boards are screwed tightly to the backbox ground plain, with all screws installed. This improves grounding and will help minimize "hum". 

Another cause of hum could be an inconsistent +5DC volts from the power supply. An indicator of this being the cause of hum would be the game occasionally resetting as well. Replacing caps C8 and C10 on the power supply may correct this issue. 

Depending on the version of System 11 board, an 11C board or anything else (nothing, 11A, and 11B), sounds and music are handled with different specifics. With the first 3 generations of MPU boards, the sounds originate from the MPU board and the background music originates from the sound board. With the 11C board, both sounds and music are on the sound board, as the MPU no longer has a sound section populated on it. 

=====Volume POT value=====
Some System 11 games shipped with a 5K linear volume POT. Others shipped with a 10K linear volume POT. Both POT values work fine and either can be used to replace a failed volume POT.

Some System 11 games shipped with a 50 ohm resistor soldered to the volume POT. It is thought that this resistor was included so that the volume could never be turned to zero. For route games, at least some sound was thought to increase game earning potential. This resistor can be removed or jumpered around to enable turning the sound volume completely off.

=====Boot Up Diagnostic Tones for the D-11297, D-11298, and D-11581 Sound Boards=====
The D-11297, D-11298, and the D-11581 sound boards all provide diagnostic tones ("bongs") at power on. A single "bong" means that the sound board is operating properly.

Lack of a bong indicates a problem with the sound board or it's connections. The possible causes for failure are numerous, including a failed amplifier, missing or incorrect connector placement, missing or noisy (AC ripple) power for a required voltage (-12VDC), failed speakers or the connection to the speakers, etc.

If the sound board is healthy enough to perform it's own self-diagnosis, it will attempt to indicate the problem by playing a specific number of bongs, as shown in the tables below.

D-11297 & D-11298 Sound Boards
{| class="wikitable"
!"Bong" Count
!Description
|-
|<center>1</center> ||  Normal sound board boot with no problems detected.
|-
|<center>2</center> ||  U3 RAM Problem
|-
|<center>3</center> ||  U4 Sound ROM Problem
|-
|<center>4</center> ||  U19 Sound ROM Problem

|}

D-11581 Sound Board
{| class="wikitable"
!"Bong" Count
!Description
|-
|<center>1</center> ||  Normal sound board boot with no problems detected.
|-
|<center>2</center> ||  U5 RAM Problem
|-
|<center>3</center> ||  U4 Sound ROM Problem
|-
|<center>4</center> ||  U19 Sound ROM Problem
|-
|<center>5</center> ||  U20 Sound ROM Problem
|} 

=====Sound Diagnostics Via the MPU Board for Games Prior to 11C=====

Pressing the upper switch of the two switches on the side of the MPU board will test both the CVSD and DAC on the MPU board. The first sound is typically sound ROM (on the MPU) specific, and it is a test of the CVSD chip. The second sound is described as a "twing", and it is a test for the DAC. If no sounds are heard, refer to the potential issues listed above in the previous section. If one "ring" is heard, it denotes that the U23 RAM chip has failed. Two or four rings denotes that there is a problem associated with U21 ROM. Three or five rings denotes that there is a problem associated with U22 ROM.

 

=====Connecting the Speaker and Volume Connections for a System 11 MPU Board on the Bench=====
[[FILE:WMS Sys11 Speaker Volume Connection.JPG|300px|left|thumb|Speaker and Non-adjustable Volume Control Connected on a System 11 MPU Board]] 
To test the sound on a System 11 MPU on the bench, a speaker and volume control must be connected to connectors 1J15 and 1J16 respectively.

The speaker should connect to pins 2 and 3 of 1J15.

In the adjacent pic, a 470Kohm resistor was used in lieu of a volume pot. Other resistor values can be used, but 470Kohm allows the sound to be set to a comfortable audible level. Alligator clips can be used, but if the intentions are to test sound boards in the future, a resistor can be crimped into a .156" housing as shown. This resistor/connector set up can be used on all Williams sound boards from System 3 through System 11.

If using alligator clip leads to power the board, use special care as to not send +12v down the -12v line (the pins are adjacent to one another). Sending +12v down the -12v bus will most definitely destroy the 1408 DAC chip (if populated).
 

=====Sound Is Very Faint Even at Maximum Volume =====
[[Image:55536-CVSD.jpg|300px|thumb|right|Two hard to find 55536 CVSD ICs.]] 
While most techs would suspect either a TL082 or a TL084 amplifier (on a pre-DCS sound board) or a 1458 amplifier (on a System 11 MPU) as the cause of this issue, the 55516/55532/55536/55564 CVSD (Continuously Variable Slope Delta-Modulator) can also cause this issue.

Isolation to the CVSD is pretty simple.

*Place the game into sound test.
*Use an oscilloscope to probe pins 9 and 12. A scope must be used since the signals are too subtle for a logic probe to detect.
*Pin 9 is a clock signal.
*Pin 12 is a data signal.

When the game is making sounds that use the CVSD, both pin 9 and pin 12 should show "off nominal" signals. If the CVSD is working correctly, the output at pin 3 should be showing signal also. If it is not, then the CVSD has failed.
 

=====Some Sounds Lower Volume Than Others =====
[[Image:System11DACChannel.jpg|300px|thumb|left|The sound section of a System 11 MPU and the 2N3904 amplifying transistor.]] 
Another sound anomaly manifests as some sounds being more faint than others is a failure in the 1408 DAC sound lane channel. In High Speed, for example, "Sound Test" exercises both the 1408 and 55536 sound lanes. Sounds 1, 3, and 5 are all made via the 1408 DAC lane. If those sounds are faint, the issue could be the 10uf capacitor (C8), the 2N3904 transistor (Q1) that is used as a pre-amplifier, the 3.3K resistor (R7), or the 1408 DAC. Eliminating the easy possibilities first, replace the 10uf capacitor. If that doesn't fix the issue, replace the 2N3904. The 2N3904 may "diode test" as failed, but not always. If the issue still remains, replace R7. Lastly, replace the 1408 DAC (U2). An equivalent part that may be used is the DAC0808.

A video, showing the problem and resolution can be viewed [https://www.youtube.com/watch?v=G7fk3PtwvtE here].
 

[[FILE:WMS_Sys11_1408_flipped_lid.jpg|300px|thumb|left|The 1408 in the sound section of a System 11 MPU lost its top!]] 
In another instance, Pin*Bot, all of the sounds were faint, except the last two in test. This ended up being a bad 1408 DAC. The last two sounds were unaffected, because the 55516 CVSD chip handled them. With a visual inspection, the 1408 in the pic could not be determined it was bad, until it was in the midst of being desoldered from the circuit board.

 

===== Voice callouts are much softer than music/sound or missing completely =====
The sound mixing section on the System 11A and 11B MPU boards were populated with different resistor and capacitor value parts. If an 11A MPU is installed into an 11B game (F-14 into an Earthshaker for instance), it is possible that the voice callouts will be noticeably softer than the other music/sound. The following table details the difference between the two sound mixing sections ''(Thanks to Pinsider "Mneubey")''.

[[Image:System11_11n_sound.jpg|500px|thumb|left|System 11 (nothing) sound section. ''Image courtesy of PinSider "DumbAss"'']] 
  Resistors

    R21 is 12K in 11B, 15K in 11A 
    R22 is 22K in 11B, 27K in 11A 
    R19 is 56K in 11B, 27K in 11A 
    R16 is 180K in 11B, 56K in 11A 
    R17 is 270K in 11B, 220K in 11A 
    R15 is 180K in 11B, 43K in 11A 
    R20 is 12K in 11B, 27K in 11A 

  Capacitors

    C10 is 470pf in 11B, 1800pf in 11A 
    C11 is 100pf in 11B, 180pf in 11A 
    C12 is 470pf in 11B, 1200pf in 11A 
    C13 is 4700pf in 11B, 4700pf in 11A 

[[Image:System11_11b_sound.jpg|500px|thumb|left|System 11B sound section. ''Image courtesy of PinSider "DumbAss"'']]
 

===== Sound Board D-11581 Mixer Section Resistor Values =====
[[Image:D11581ResistorValues.jpg|500px|thumb|left|"Mixer" section resistor values across D-11581 sound board games. ''Data courtesy of PinSider "DumbAss"'']] 
The sound mixing section on the System 11A through 11C sound boards were populated with different resistor values. The table shown at left details the differences between the sound mixing sections for each game.

Note that the value of R13 will change also. It should be 4.99K for "Fire!" through "Police Force", and 10K for all other games.
 

=====Missing Some Music or Garbled Music with a D-11581 Sound Board and 5 Bongs=====
A sound board booting with 5 bongs indicates a failure of the U20 ROM. While U20 could, in fact, have failed, 5 bongs could also mean that the software can't access U20. In one such case where 5 bongs were heard, during music test, tests 4 and 6 would play music but the music was garbled and/or incorrect. The root cause was W10/W11 jumper settings on the sound board that didn't match the ROM size. W10/W11 should be set to the left for 27256 ROMs; to the right for 27512 ROMs.
 

=====Modifying a pre-System 11C Sound Board to use 27512 ROMs (D-11581)=====

[[Image:System11BSoundBoardW2W3.jpg‎|300px|thumb|left|D-11581 sound board jumpers W2 and W3. Note that W3 is "always IN". The solder mask over the W3 jumper trace has been removed for clarity. Normally the trace is covered by a dashed white silkscreen line.]]
[[Image:System11BSoundBoardW2W3Modified.jpg‎|300px|thumb|right|D-11581 sound board jumpers W2 and W3. W3 has been cut to enable use of 27512 ROMs.]]

Some revisions of the D-11581 sound board will not accept 27512 sound ROMs without modification. By the time that revision C was manufactured, jumpers W10 and W11 were added above U20 to enable use of larger ROMs. Prior to that, jumpers W2 and W3 were implemented, but were of little use since both jumpers tied A15 (pin 1) of each EPROM to +5VDC. Making the modification pictured at right, then installing jumper W2, enables the use of 27512 ROMs.
 

=====Jokerz specific sound issue=====
A special case of interference is present on the Jokerz game, which uses a unique stereo sound board. A deficiency in its design prevents all of the noise from being eliminated from the board. Details can be found in the original Williams service bulletin here: [http://www.ipdb.org/files/1308/Williams_1988_Jokerz_William_Service_Tip_For_Audio_Hum.pdf Jokerz service bulletin at IPDB.org]

=====Whirlwind Doesn't play Sound 7 During Test=====
This particularly annoying issue appears to have no impact during gameplay. The only manifestation is that "Sound Test", sound 7 doesn't play. The normal sound is an explosion.

This issue is caused by old game ROM versions at U26 and U27. Revision PA1 doesn't send the command to the sound subsystem to play sound 7, even though sound 7 is displayed on the alphanumeric display. Updating U26/U27 to "LA3" as can be found at www.ipdb.org will correct this issue.

[[file:YT.png]] Correct Whirlwind sounds are demonstrated in a YouTube video found [https://www.youtube.com/watch?v=fy_GXp3Bfzg here].
 

=====Sound Board Theory of Operation (D-11581)=====

[[Image:System11CSoundBoard.jpg|500px|thumb|right|D-11581 Sound Board, Completely Populated and including jumpers W10 and W11]] 

Major components of the D-11581 sound board are:

*68B09E externally clocked CPU, which is also used in all WPC MPU and pre-DCS sound boards
*68B21 Peripheral Interface Adapter, capable of running at 2Mhz
*Up to 3 ROMs. All boards can accommodate 27256 ROMs. Some later boards can be jumpered to accommodate 27512 ROMs.
*6116 RAM (2K bytes). Some later boards can be jumpered to accommodate a 6264 RAM (8K bytes)
*YM2151 sound synthesizer paired with the YM3012 DAC (outputs channel 1 and channel 2)
*55516 CVSD (continuously variable slope delta) audio encoder, which provides a 3rd audio channel
*1408 DAC (digital to analog converter), which provides a 4th audio channel
*Various 74XX ICs that perform address decoding and chip selection logic
*1458 pre-amplifiers and TDA2002 amplifiers

The D-11581 sound board shares a lot of board design and architecture of the pre-DCS sound board that was introduced with WPC games.

Power

Power requirements for the board are supplied via connector J3. The typical sound board power levels are required, 5VDC, 12VDC, -12VDC, and Ground. Three 100uf capacitors reduce noise on the power busses along with several small ceramic caps which filter high frequency noise.

Reset

The on board 68B09E is reset via the external reset signal provided by the MPU board, via connection J4, pin 18. If attempting to operate the board without the MPU board connected, the processor must be manually reset via momentarily grounding pin 37 of the 68B09E.

Clocking

The clocking signal for the board originates at the 8Mhz crystal oscillator. U16, a 74LS74 Dual D-Type FlipFlop divides the clock signal yielding both the "E" and "Q"clock signal. E and Q are phase shifted by one half clock cycle.

Chip Select Logic

Chip select is accomplished via the normal "memory mapped I/O" method, using U14 (74LS139) and U15 (74LS138).
*Chip select for all three ROMs (U4, U19, U20) is implemented by U14.
*Chip select for the RAM (U5), YM2151 (U3), and the 6821 (U12) is implemented by U15.

How sounds are produced

Sound select signals are provided via J4, a dual row .100 connector of 20 pins. These sound selects are held "normally high" via a 4.7K/470pf 10-pin bussed SIP pull-up resistor/capacitor (SR1) tied to 5VDC. These SIP resistor/capacitor parts are no longer available. A bussed 4.7K 9-pin resistor network can be used as a replacement. The capacitor feature of the original part filtered high frequency noise from the communication lines. In practice, noise doesn't impact the interface significantly enough to be of concern.

The MPU board will pull the appropriate sound select signals to ground via the 6821 PIA at Uxx. When the appropriate signals are pulled to ground, the PIA is programmed to interrupt the 68B09E processor via the FIRQ and NMI signals. The 68B09E then reads the sound select signals presented at the 6821s input port (PB0 through PB7) via the processor data bus (D0 through D7).

The processor then employs the 4 sound channels available to it, along with encoded sound files contained in the ROM images, to create the intended sounds.

====Where Do The Sounds Come From?====

The following sections can be used to ensure that all sounds are played by the Williams combined MPU and Sound Board System.

=====System 9 Games (alphabetical)=====
{| class="wikitable"
! style="text-align:left;" | Game
! style="text-align:left;" | Audio Demo Link
|-
| Comet|| [[file:YT.png]] [https://youtu.be/-2m7vKCeg2A Audio]
|-
| Sorcerer || [[file:YT.png]] [https://youtu.be/pXacwGqv5C4 Audio]
|-
| Space Shuttle                     || [[file:YT.png]] [https://youtu.be/B-gsuEw1jgU Audio]
|}

=====System 11 Games (alphabetical)=====
{| class="wikitable"
! style="text-align:left;" | Game
! style="text-align:left;" | Audio Demo Link
|-
| Bad Cats || [[file:YT.png]] [https://youtu.be/-JJKPvMBplg Audio]
|-
| Bally Game Show || [[file:YT.png]] [https://youtu.be/vwA4FST62ug Audio]
|-
| Banzai Run || [[file:YT.png]] [https://youtu.be/6D87Z2iUsv0?si=x8BKbDsxHFI_yodb Audio]
|-
| Big Guns || [[file:YT.png]] [https://youtu.be/dVuZsHhdzwE?si=myMFNRyghT2aJs7u Audio]
|-
| Black Knight 2000 || [[file:YT.png]] [https://youtu.be/uyJlxc2ewtY Audio]
|-
| Cyclone || [[file:YT.png]] [https://youtu.be/pEdSxFu1Zio Audio]
|-
| Diner || [[file:YT.png]] [https://youtu.be/rwCLpG5jU2I Audio]
|-
| Earthshaker || [[file:YT.png]] [https://www.youtube.com/watch?v=eH0FVvbBQUQ Audio]
|-
| Elvira & the Party Monsters || [[file:YT.png]] [https://youtu.be/OS_SRCNaMwg?si=6Wop4YLK2wa6Mco4 Audio]
|-
| F-14 Tomcat || [[file:YT.png]] [https://youtu.be/rG26I-oDK6E Audio]
|-
| Fire! || [[file:YT.png]] [https://youtu.be/dXKRw1GqUcQ Audio]
|-
| High Speed || [[file:YT.png]] [https://youtu.be/yAmJzD9EAZA Audio]
|-
| Jokerz || [[file:YT.png]] [https://youtu.be/E5QrfiZYVVY?si=3ttDBR_PHdbjnFMY Audio]
|-
| PinBot || [[file:YT.png]] [https://youtu.be/CoVvhwggLfU Audio]
|-
| Police Force || [[file:YT.png]] [https://youtu.be/Em63v0-zJKk?si=gt3qD2jLsqJFdwlW Audio]
|-
| Pool Sharks || [[file:YT.png]] [https://youtu.be/gceZEgLMaDQ Audio]
|-
| Riverboat Gambler || [[file:YT.png]] [https://youtu.be/6SBGT7_P62g?si=kAmVE1EUglQTyn8T Audio]
|-
| Rollergames || [[file:YT.png]] [https://youtu.be/tN-Ns9eh8Pg Audio]
|-
| Space Station || [[file:YT.png]] [https://youtu.be/9XERXpVGCsY?si=jSNjikeN1nM6GeQy Audio]
|-
| Swords of Fury || [[file:YT.png]] [https://youtu.be/u6baQrse5LI?si=3Y85cpAXqDF5_Qis Audio]
|-
| Taxi || [[file:YT.png]] [https://youtu.be/P7DIs5djK-E Audio]
|-
| Whirlwind|| [[file:YT.png]] [https://www.youtube.com/watch?v=fy_GXp3Bfzg Audio]
|}
 

===Flipper problems===

==== Flipper Circuit Schematics Error ====
[[File:WMS Serial Flipper Schems.JPG|left|300px|thumb|Correct wiring schematic for serial wound flipper coils]]
[[File:WMS Serial Flipper Schems Incorrect.JPG|right|300px|thumb|Incorrect wiring schematic for serial wound flipper coils]] 
Early System 11 and 11A games used serial wound coils. These coils only have a single diode on them. Some of the early System 11 manuals show incorrect wiring for the EOS switch. One of the EOS switch wires should be soldered to the center lug of the coil. However, the other wire should be soldered to the lug with the non-banded side (anode) of the diode, not the lug with the banded side (cathode) of the diode. Manuals which have this misinformation are High Speed, Grand Lizard, and Road Kings. Millionaire and Pinbot appear to be fine.
 

==== Flipper Electrical Problems ====

System 11 (nothing) and System 11A games derive 50VDC flipper power from the "50V Flipper Power Board".
System 11B and 11C games derive 50VDC flipper power from the "Aux Power Supply" board that was introduced with these games.

System 9 and 11 flipper circuitry is identical to all prior Williams System 3-7 games. The design had not changed from even the old electro-mechanical flipper implementation when the End of Stroke switch was introduced.

Yes, Williams used serial wound coils from High Speed to Millionaire and then converted to parallel wound coils beginning with F-14 TomCat and throughout the rest of the System 11 run and into the WPC run. But the basic operation of System 9/11 coils remained "EM-like" whether serial or parallel wound.

There are only three switches that can affect the electrical operation of a System 11 flipper, including strength.

#Switches inside the Flipper Enable relay (K1), located on the MPU board.
#The cabinet flipper button switches.
#An End-of-Stroke (EOS) switch associated with each flipper coil and integrated into the flipper mechanism assembly.

====Series Wound Flipper Coil Operation====
When the flipper enable relay (K1) switches close, a path to ground is provided for the flipper coil. The EOS switch is closed, creating a short across the low power windngs, that removes resistance of the low power windings from the circuit. Only the smaller number of high power windings are "in circuit" with the EOS switch closed.

When the flipper cabinet switch is closed by pressing the flipper button, this is the final switch in the path to ground for the waiting power at the low resistance high power windings of the coil. The coil plunger is pulled into the coil and the flipper "flips". Near the end of the flipper's mechanical stroke, a pawl (a tab that sticks up) on the flipper crank mechanism will open the EOS switch, removing the short across the low power windings, and placing them in series along with the high power windings. Together, the total resistance of the coil becomes the sum of both the low power and the high power windings. With more windings, the coil will have higher resistance and hence, lower power. The combined high resistance windings act like a "hold" or "coin door lockout" relay coil, able to withstand being energized for extended periods of time. Without the mechanization of the EOS switch, the high power windings would overheat quickly and damage the coil. For this reason, EOS switch adjustment, and a clean EOS switch, are critical.

====Parallel Wound Flipper Coil Operation====
[[File:ParallelWoundFlipperDiagram.jpg|left|400px|thumb|Parallel Wound Flipper Coil Operation. Diagram courtesy of Chris Hibler.]]
When the flipper enable relay (K1) switches close, a path to ground is provided for the low power windings of the flipper coil. And, since the EOS switch is closed, the high power windings also have a path to ground.

When the flipper cabinet switch is closed by pressing the flipper button, this is the final switch in the path to ground for the waiting power at both of the coil parallel windings. Since electrical current "takes the path of least resistance" the lower resistance high power winding takes most of the current and the flipper "flips". Near the end of the flipper's mechanical stroke, a pawl (a tab that sticks up) on the flipper crank mechanism will open the EOS switch, breaking the path to ground for the high power windings. The high resistance low power windings remain in circuit, and provide "hold" power to the flipper coil. The high resistance low power windings act like a "hold" or "coin door lockout" relay coil, able to withstand being energized for extended periods of time. Without the mechanization of the EOS switch, the high power windings would overheat quickly and damage the coil. For this reason, EOS switch adjustment, and a clean EOS switch, are critical.
 

==== Flipper Mechanical Problems ====

*Return springs
*Fractured nylon bushing
*Insufficient gap between nylon bushing and crank
*Heat damaged coil
*Damaged coil sleeve
*Damaged coil stop
*Flipper shaft slipping within crank
*Others?

===Pop bumper problems===

==Repair Logs and Game Specific Problems and Fixes==
Did you do a repair? Log it here as a possible solution for others.

===System 11 Display Single AlphaNumeric Character Won't Light===
[[File:Sys11B Bridged Header.jpg|300px|left|thumb|A solder bridge on the "digit strobe" connector.]] 
In the category of "things that will make you crazy", the solder bridge pictured at left shorted pins 8 and 9 on the connector that carries the digit strobes to a System 11 display. This prevented one of the digits on the display from ever lighting. It's always a good idea to examine prior work closely. Assuming the prior tech knew what they were doing is not always valid. 

===Using a System 6/7 Speech Board in a Comet===
[[File:WMS Sys9 CPU with 2732 Speech.JPG|300px|left|thumb|A Modified System 6/7 Speech Board Functioning with a System 9 CPU]] 
Should the need arise, a System 6/7 speech board can be [http://www.pinwiki.com/wiki/index.php?title=Williams_System_3_-_7#Modifying_the_System_6.2F7_Speech_Board_to_Use_2732_EPROMs modified to use 2732 EPROMs] for a Comet.
 

===Using a Data East MPU Board in a System 11 Game===
Whaaaat?!?! Yes, a Data East MPU can be used in a Williams or Bally System 11 game. However, this is limited to System 11C games only, and only a DE 520-5003-03 (Version 3) MPU can be used. The reason for this limitation is because games previous to 11C have some or all of the sound section circuitry on the MPU board populated, the 11C does not. Likewise, DE boards do not have any sound section circuitry located on them by design. The board swap is not a simple drop in replacement though. Some minor modifications have to be performed for the DE board to function properly in an 11C game.

The first hurdle is to properly power the DE board. Connection 1J17 is where power originates on the 11C board. The complimentary connection on a DE board is CN17. The problem is that these connections are keyed differently between the two boards. 1J17 has a key at pin 7, while the key on CN17 is at pin 8. The safest way to make a connection to CN17 with the 11C game harness is to remove pin 7 on the DE board. This will have no ill effect, if the DE board is to be placed back into a DE game. The worst case scenario if pin 7 is removed and the board placed back into a DE game is that the CN17 connector housing could be installed off by one pin, thus shorting the +5v to ground, and blowing the logic voltage fuse. 

[[File:DE MPU Jumpers for 11C.JPG|300px|thumb|left|Correct jumper setting on DE MPU for 11C game ROMs]]
[[File:DE MPU Special Solenoid Wire Swap for 11C.JPG|300px|thumb|right|Addition harness and Z-connector installed to correct special solenoid drive outputs]]
Next, the game ROM jumpers have to be set correctly. Since all 11C games use dual ROMs, jumper setting J4 must be in on the DE MPU, while J5 is out. Install the 11C game ROMS in the following positions. U27 (ROM 1) is to be inserted into the 5C socket, while U26 (ROM 2) is installed into the 5B socket. Notch on the chip / socket is facing to the right. There is an alternative method. The code for the dual ROMs can be burned into a [http://www.pinwiki.com/wiki/index.php?title=Data_East/Sega#Burning_Dual_ROMs_into_a_Single_5C_ROM single 27512 EPROM.]

Finally, there is a problem with how DE boards poll the special solenoid drivers differently than 11C boards. Two of the drivers are correct (solenoids 17 and 21), while the four others are mismatched. To overcome this problem, either a harness can be created (DE board to 11C harness) with a Z-connector installed between 1J19 and the game harness, or the 7-pin housing (the 9-pin housing at 1J19 is split with a 2-pin housing and a 7-pin housing) at 1J19 can be repinned. The benefit of building a harness and adding a Z-connector is that it is easily reversible, if an 11C board is to be placed back into the game at a future time. 

The following wires will have to be connected to 1J19 / CN19 on the DE board for the game to function as intended.

{| class="wikitable"
!Pin Connection
!Stock Wiring
!Swapped Wiring
!Notes
|-
|1 || ORG-VIO || ORG-VIO || No change. This is for the flipper enable.
|-
|2 || ORG-GRY || ORG-GRY || No change. This is for the flipper enable.
|-
|3 || BLU-ORG || BLU-YEL ||
|-
|4 || BLU-RED || BLU-ORG ||
|-
|5 || Key || None ||
|-
|6 || BLU-YEL || BLU-BLK ||
|-
|7 || BLU-BRN || BLU-BRN || No change.
|-
|8 || BLU-GRN || BLU-GRN || No change.
|-
|9 || BLU-BLK || BLU-RED ||
|-
|}
 

=== Ball Will Not Kick Over to Shooter Lane at Game Start (Pinbot) ===
Trough and shooter lane switches test alright in switch test. Ball feeder coil from trough to shooter lane tests fine in solenoid test. If the motor for the visor is disconnected, and the visor does not cycle at the start of the game, the ball will not kick to the shooter lane. This may be an issue if one or both of the visor switches are not recognized too. Not certain what code revision this particular game was running.

=== Ball Will Not Kick Over to Shooter Lane and Drop Target Will Not Reset (Cyclone) ===
[[File:Cyclone UnderPF Fuse 1A 5A.jpg|300px|thumb|left|Fuse under the playfield of a Cyclone, which powers solenoids 1A and 5A]] 
Both the outhole solenoid (1a) and drop target reset solenoid (5a) are the only multiplexed 24v coils in Cyclone. The power wires for these coils are brown. For some reason, Williams decided it would be a good idea to put a fuse under the playfield for these coils (which is not included in the documentation). The fuse/fuseholder is located just to the right of the spook house subway.
 

===Special Solenoids Are Not Pulsed During Solenoid Test on System 9 Games===
The System 9 circuit board architecture provides no physical way to control the special solenoids other than via the enabling switch associated with the special solenoid device.

===CPU energizes a coil 5 times===
'''Police Force''' - After the pinball is switched on the ramp diverter coil engages 5 times. After the game start the diverter coil engages 5 times again. Diverter mechanism doesn't hold in position. So after the coil is energized the mechanism falls back and so the switch is closed again. Then the software tries another 4 times to resolve the problem. 

'''Resolution:''' Clean the diverter mechanism and in particular the plastic. Lubricate the plastic lanes!

===Elvira and the Party Monsters drop target reset coil blows the lamp matrix===
The drop target reset coil should be mounted with the solder tabs down. If mounted with the solder tabs up, (toward the playfield) the solder tabs can contact the J-A-M lamp sockets. This blows the lamp matrix ICs on the MPU board by sending coil voltage through the lamp matrix.

Bally/Stern

2025-04-07T18:53:45Z

The Hammer: /* SB-100 Sound Board */ Included link to the Wayback Machine since the techdose.com information seems to be gone.

Click to go back to the [[Bally/Stern_Electronics_Repair_Guides | Bally/Stern solid state repair guides index]].

==Introduction==
[[File:Bally-17_boardset.jpg|200px|thumb|left|Bally -17 Board Set]]
[[File:-35 boardset centaur.jpg|200px|thumb|right|Bally -35 Board Set]] 
Bally first started to experiment with solid state in the mid 70s with a couple conversions of EM games, Flicker and Bow & Arrow. Flicker's control system was designed by Jeff Frederiksen of Dave Nutting Associates, a Bally think-tank. This board utilized the Intel 4004 microprocessor. One prototype was built and was re-discovered in 1998. The Bow & Arrow system of which 17 were eventually built more closely resembles what actually ended up in the production games starting with Freedom. This boardset was designed by a Bally engineer named Doug MacDonald. There are at least two revisions of the prototype run's software in existence. 

For an interesting read, the patent Bally filed for their first "computerized pinball machine" can be viewed [http://www.google.com/patents/US4198051 here].
 

[[File:SternMPU-100.jpg|200px|thumb|left|Stern M-100 Board Set]]
[[File:Stern m-200 boardset.jpg|200px|thumb|right|Stern M-200 Board Set]] 
The early circuit boards were fabricated by a company called Universal Research Laboratories (URL). URL was purchased by Gary Stern as part of his strategy in acquiring the assets of the defunct Chicago Coin; it is this connection that enabled Stern to use essentially the same hardware for their solid state games as Bally. The software is remarkably similar as well, although Bally was more apt to use a "set" of operating system roms (the U6 chip) for several games, whereas Stern opted to custom-compile their roms for each game, or at most, pairs of games. 

[[File:GB8.jpg|200px|thumb|left|Bally Goldball special driver/voltage board]] 
Some later -35 Bally games used a combination of the solenoid driver board and the lamp driver board.
 

The core system consists of:
* A transformer to produce various AC voltages from line voltage
* A rectifier board to convert those AC voltages to DC and provide fuse protection
* A solenoid driver/voltage regulator board to regulate/filter the DC voltages and provide switching for solenoids
* A lamp driver board to switch up to 60 lamps on/off
 

Optional components added to the system at later dates include:
* Various sound boards, providing various type of sounds from simple tones, to background sound, to complex speech and sounds
* Auxiliary lamp driver boards, to provide control for more than 60 lamps
* Solenoid expander boards to allow more than 15 controllable momentary solenoids to be connected
 

==Games==
A list of solid state games by system and manufacturer (including those that aren't necessarily pinball). Source: http://www.ipdb.org
===Bally===
{|class="wikitable"
! scope="col" style="width:15%;" | Game Title
! scope="col" style="width:10%;" | MPU
! scope="col" style="width:10%;" | Power Supply
! scope="col" style="width:15%;" | Lamp driver
! scope="col" style="width:10%;" | Sound
! scope="col" style="width:30%;" | Additional Boards
! scope="col" style="width:10%;" | Transformer
|-
|[[Freedom]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125 [[#as2877freedom|see note]]
|-
|[[Night Rider]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Black Jack]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Evel Knievel]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Eight Ball]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Power Play]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Mata Hari]] || AS-2518-17 || AS-2518-18 || AS-2518-23 || Chimes || || E-122-125
|-
|[[Strikes & Spares]] || AS-2518-17 || AS-2518-18 || AS-2518-23 || Chimes || || E-122-125
|-
|[[Bally Lost World|Lost World]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| || E-122-125
|-
|[[The Six Million Dollar Man]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| || E-122-125
|-
|[[Bally Playboy|Playboy]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| || E-122-125
|-
|[[Voltan]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| A few games were outfitted with an AS-2518-51 sound board for testing || E-122-125
|-
|[[Supersonic]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| || E-122-125
|-
|[[Bally Star Trek|Star Trek]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-50|| || E-122-125
|-
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Additional Boards
! scope="col" | Transformer
|-
|[[Bally Kiss|Kiss]] || AS-2518-35 || AS-2518-49 || AS-2518-23 || AS-2518-50|| Auxiliary Lamp Driver AS-2518-43 || E-122-131
|-
|[[Paragon]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-50|| || E-122-125
|-
|[[Harlem Globetrotters]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-50|| || E-122-125
|-
|[[Dolly Parton]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-50|| || E-122-125
|-
|[[Future Spa]] || AS-2518-35 || AS-2518-49 || AS-2518-23 || AS-2518-51|| Auxiliary Lamp Driver AS-2518-43 || E-122-131
|-
|[[Space Invaders]] || AS-2518-35 || AS-2518-49 || AS-2518-23 || AS-2518-51|| Auxiliary Lamp Driver AS-2518-52 || E-122-131
|-
|[[Nitro Groundshaker]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Silverball Mania]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Bally Rolling Stones|Rolling Stones]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Mystic]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Hotdoggin]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Viking]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Skateball]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Frontier]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Xenon]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-56 (Sounds Plus) || Auxiliary Lamp Driver AS-2518-52, Vocalizer module AS-2518-57 || E-122-142
|-
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Additional Boards
! scope="col" | Transformer
|-
|[[Flash Gordon]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61 (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, early games used the Sounds Plus (AS-2518-56) board and Vocalizer module (AS-2518-57) instead of the S&T board || E-122-142
|-
|[[Eight Ball Deluxe]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 || E-122-142
|-
|[[Embryon]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52 || E-122-142
|-
|[[Fireball II]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Auxiliary Driver - SCR Lamp Flasher AS-2518-67, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Centaur]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Say It Again AS-2518-81 (Reverb), Auxiliary Lamp Driver AS-2518-43, Solenoid Expander AS-2518-66, Auxiliary Driver - SCR Lamp Flasher AS-2518-67, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Elektra]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Fathom]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 || E-122-142
|-
|[[Medusa]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 || E-122-142
|-
|[[Vector]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66, Auxiliary Driver - GI Flasher AS-2518-68, Auxiliary Driver - Triac Lamp Flasher AS-2518-82 || E-122-142
|-
|[[Rapid Fire]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Ball Delivery Sensor & Motor Board AS-2518-102 || E-122-142
|-
|[[Mr. & Mrs. Pacman]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-161
|-
|[[Speakeasy]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-51 || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 || E-122-142
|-
|[[Spectrum]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Uses a second AS-2518-23 for lamps (2 total in game), Auxiliary Driver - SCR Lamp Flasher AS-2518-67, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Baby Pac-Man]] || AS-2518-133 || AS-2518-132 || AS-2518-107 (combo lamp and solenoid driver) || n/a || Vidiot AS-2518-121 || AS-3071-12
|-
|[[Eight Ball Deluxe Limited Edition]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61 (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 ||
|-
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Additional Boards
! scope="col" | Transformer
|-
|[[BMX]] || AS-2518-35|| AS-2518-54 || AS-2518-23 || AS-2518-51 || Solenoid Expander AS-2518-66 || E-122-161
|-
|[[Grand Slam]] || AS-2518-133 || AS-2518-151 || AS-2518-147 (combo lamp driver/solenoid driver/regulator) || AS-2518-51 || || ?
|-
|[[Centaur II]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Say It Again AS-2518-81 (Reverb), Auxiliary Lamp Driver AS-2518-43, Solenoid Expander AS-2518-66, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Goldball]] || AS-2518-133 || AS-2518-151 || AS-2518-147 (combo lamp and solenoid driver) || AS-2518-51 || Auxiliary Driver - GI Flasher AS-2518-68 || E-122-170
|-
|[[Eight Ball Deluxe Classic]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61 (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52 || ?
|-
|[[Granny and the Gators]] || AS-2518-133 || AS-2518-132 || AS-2518-107 (combo lamp and solenoid driver) || M-051-00114-B045 (Cheap Squeak) || Vidiot Deluxe A062-91600-D000 || AS-3071-12
|-
|[[X's & O's]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43 || E-122-142
|-
|[[Kings of Steel]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43 || E-122-142
|-
|[[Black Pyramid]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43 || E-122-142
|-
|[[Spy Hunter]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Fireball Classic]] || AS-2518-35 [[#fbmpu|†]] || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Solenoid Expander AS-2518-66 || AA40-0037-0000
|-
|[[Cybernaut]] || AS-2518-35 [[#cympu|‡]] || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43 || ?
|}
<div id="as2877freedom"></div>*Note: Part of the AS-2877 POWER TRANSFORMER MODULE which has the AS-2518-18 Rectifier Board Assembly mounted directly onto the transformer using a bracket. Later games had the AS-2877-1 POWER TRANSFORMER MODULE which had a large metal plate onto which both the transformer and AS-2518-18 Rectifier Board Assembly were mounted. See [http://www.ipdb.org/showpic.pl?id=4500&picno=40867 Inside Backbox] photo on the Internet Pinball Database page of Freedom for an example of AS-2877. See also [http://www.planetarypinball.com/reference/partsmanuals/BLY_Parts_1979/index.html#/4/ Page 4 of the Bally 1979 Parts Catalog].
 
<div id="fbmpu"></div>† Note: Fireball Classic was sometimes fitted with a 6802 MPU board (an upgrade from the -35 board)
 
<div id="cympu"></div>‡ Note: Cybernaut was sometimes fitted with a 6802 MPU board (an upgrade from the -35 board), or a 6803 MPU board.

===Stern===
{|class="wikitable"
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Transformer
! scope="col" | Notes
|-
|[[Pinball]]|| M-100 || TA-100 || LDU-100 || Chimes || 16B-3 ||
|-
|[[Stingray]]|| M-100 || TA-100 || LDU-100 || Chimes || 16B-3 ||
|-
|[[Stars]]|| M-100 || TA-100 || LDU-100 || Chimes || 16B-3 ||
|-
|[[Memory Lane]]|| M-100 || TA-100 || LDU-100 || Chimes || 16B-3 ||
|-
|[[Lectronamo]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Wild Fyre]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Nugent]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Dracula]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Trident]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Hot Hand]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Magic]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Cosmic Princess]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Transformer
! scope="col" | Notes
|-
|[[Meteor]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Galaxy]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses relay to turn on / off general illumination
|-
|[[Ali]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses relay to turn on / off general illumination
|-
|[[Big Game]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || First Stern 7 digit game, widebody
|-
|[[Seawitch]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Cheetah]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || First stern game using plastic pop bumper rod and ring, widebody
|-
|[[Quicksilver ]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Stargazer]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Nine Ball]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Iron Maiden]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Widebody. Uses IM-100 flash lamp board.
|-
|[[Viper]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Widebody
|-
|[[Dragonfist]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Cue]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Flight 2000]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, widebody
|-
|[[Freefall]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, widebody
|-
|[[Lightning]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, uses interface board for bonus display in playfield
|-
|[[Split Second]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, widebody
|-
|[[Catacomb]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100
|-
|[[Orbitor 1]] || M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, widebody
|}

==Technical Info==
===The Bally / Stern Board Set===
The Bally/Stern boardsets always consist of a rectifier board, a solenoid driver/power regulator board, a lamp driver board, and an mpu board. These boards utilize the Motorola 6800 series of microprocessors, 2 peripheral interface adapter chips (6821 PIAs), a switch matrix, multiplexed gas plasma displays, and direct driving of lamps and solenoids (no matrix). Lamps are switched on near the zero crossing 120 times a second to prevent premature lamp filament burnout. 

Additional boards present in games may include various flavors of sound boards, as well as additional lamp driver boards (both main and auxiliary), solenoid expander boards, specialized boards such as an echo (say-it-again) board, and speech boards. 

The software utilized in these games is very similar to one another, consisting of an "operating system" and a "game rom"; Bally utilized a masked rom for their OS over several games, enabling many roms to be ordered at one time for lower manufacturing cost. Stern custom compiled their operating system for each game, although some games have the same exact rom codes, differing switches in each of those affected games perform different functions although the rulesets are the same/very similar to one another. 

Starting with the Stern Mpu-200 series of games (Meteor, 1979), Stern utilized a state machine architecture, where the core operating system handles the various housekeeping functions (displays, switch reading, memory management, lamps/solenoid driving, etc.) and the state layer handles things like game rules and timing of lamp and sound effects. This enabled the programmers to concentrate on defining their rulesets and lamp effects instead of tweaking timing within the assembly code itself. The state machine is multi-threaded and is able to execute up to 16 threads at one time. 

Bally games continued to use a real-time setup, where all functions are coded in 6800 assembly language, necessitating lots of additions to the operating system over the years to enable more sophisticated light and sound effects/choreography. Contemporaries of Bally (Gottlieb, Stern, and Williams) all switched to the state machine architecture at some point in their solid state eras. The coding speed advantage of the state machine enabled more rapid development of software, a distinct advantage when production runs started to become shorter and shorter. 

===Recommended Documentation===
====Manuals & Schematics====
Schematics for each game are essential in tracing down connections to lamps, switches, and solenoids. The owner's manual is a handy resource to have for dip switch settings as well as audit information.

The early -17 Bally games as well as the early stern mpu-100 games have both an owner's manual and a separate schematic package available. If buying documentation on ebay or the like, be sure to check with the seller to see what is included. Most documentation is also available via ipdb.org although the quality of some of the scans make it difficult to extract the needed information. Be aware that although rare, some factory documentation contains errors in schematics as well as game descriptions and settings.

=====Documentation Errors/Addendums=====
======Schematic Errors with Stern MPU-200 MPU======
<center>
<gallery widths=200px heights=200px perrow=3 caption="MPU-200 Schematic Errors">
File:MPU-200 Upper Schem.jpg|<center>Modified schematics showing the TP3 and R16 errors</center>
File:MPU-200 Lower Schem.jpg|<center>Modified schematics showing the actual path of U17 pin 10</center>
File:Stern MPU-200 U17 Jumper.jpg|<center>Factory jumper installed on a Stern MPU-200 board. This ties U17 pin 10 to U15 pin 3 and pin 25 of both U10 and U11.</center>
</gallery>
</center>
There are two TP1s noted on the schematics. The upper TP1 (noted as 21.5vdc pulsating) should be TP3.

There are two R18 resistors noted in the "zero crossing detector" cited at the top left of the page. The lower resistor should be R16 and the upper resistor should be R18.

U18 pin 6 '''SHOULD NOT''' connect to U17 pin 10, nor should U19 pin 13 as drawn in the schematics.

U17 pin 10 should go to U15 pin 3, U10 and U11 pin 25, U7 pins 10 and 13, and to E37 and E38, which are tied together without a jumper.

The signal going to U17 pin 10 is VUA 02', not VUA as the schematics state.

It has been noted in online forums that some MPU-200s have the trace cut between U18 pin 6 and U17 pin 10, and a jumper installed from U17 pin 10 to a via located to the right of U17. This ties U17 pin 10 to U10 pin 25, as it should be. A picture of the factory jumper installed is above, however, the cut trace could not be found in this instance.
 

======Stern Transformer Schematics======
* On the 16B-6 transformer schematics, the transformer voltage for lugs 2/4/6 is omitted. It should be noted as 49VAC, like in the schematics for the earlier 16B-3 transformer.
[[File:Stern-16b-6_schematic-error.jpg|thumb|left|250px|Stern 16B-6 transformer schematics omission]] 

======Game Manual Errors/Updates======
* [https://www.ipdb.org/files/249/Stern_1980_Big_Game_Corrections_to_Game_Manual_March_1980.pdf Stern Big Game: Manual Corrections]

====Introduction to Pinball====
Bally produced a series of "Introduction to Flipper Games" guides that included the basics of pinball machines.
{| class="wikitable"
|-
!Guide
!Cover
!Source
!Notes

|-
|Introduction to Bally Flipper Games, Revised June 1981
|[[file:Introduction-to-bally-flipper-games_revised-june-1981-cover.jpg|thumb|left|140px]]
|
|

|-
|Introduction to Bally Midway Flipper Games, Revised July 1983
|[[file:Introduction-to-bally-flipper-games_revised-july-1983-cover.jpg|thumb|left|140px]]
|[[media:Introduction-to-bally-flipper-games_revised-july-1983.pdf|PDF]]
|

|}

====Theory of Operation & Repair Guides====
Less important but still handy are the Bally Theory of Operation manual and the Repair Manuals.

The repair manuals are written with the use of test boards called AID1 and AID2 in mind (essentially a specialized logic probe), but can still have some helpful troubleshooting steps outlined. The latest revision of a repair manual normally supersedes all other previous repair manual revisions.

{| class="wikitable"
|-
!Guide
!Cover
!Source
!Notes

|-
|Bally Electronic Pinball Games Theory of Operation FO 601-2
|[[file:Bally-theory-fo601-2-cover.jpg|thumb|left|140px]]
|[[media:Bally-theory-of-operation-FO-601-2.pdf|PDF]]
|Supersedes Theory of Operation guides FO 601 and 601-1.

|-
|Bally Electronic Pinball Games Repair Procedures FO 560-3
|[[file:bally-repair-fo560-3-cover.jpg|thumb|left|140px]]
|[[media:Bally-repair-procedures-FO-560-3.pdf|PDF]]
|Supersedes repair guides FO 511, FO 512, FO 513, [[media:Bally-repair-procedures-FO-560.pdf|FO 560]], [[media:Bally-Repair-Procedures-FO-560-1.pdf|FO 560-1]], and 560-2.

|-
|Theory of Operation - Stern's Microprocessor Controlled Solid State Games (1979)
|[[file:Stern-theory-of-operation-book-1979-cover.jpg|thumb|left|140px]]
|[[media:Theory_Of_Operation_Stern's_Microprocessor_Controlled_Solid_State_Games_(Stern_MPU-100).pdf|PDF]]
|Applicable to Stern MPU-100 games from 1977-1979: Pinball, Stingray, Stars, Memory Lane, Lectronamo, Wild Fyre, Nugent, Dracula, Trident, Hot Hand, Magic.
|}

=====Individual Guides=====
* [[media:Bally-vidiot-deluxe-theory-of-operation.pdf‎|Vidiot Deluxe Theory of Operation]]

====Parts Catalogs====
Parts catalogs can also be useful, which include part numbers (helpful for purchasing parts online), exploded views of assemblies (helpful to see how the assemblies are put together), and board layouts & parts lists, and diagrams for controlled lamp, solenoid, and rubber locations. Online copies of Bally parts catalogs can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball].

{| class="wikitable"
|-
!Manufacturer
!Catalog
!Cover
!Source
!Games
!Notes

|-
|Bally
|1979 Parts Catalog
|[[file:bally-1979-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/gseb/ Viewer] [[media:Bally-Parts-Catalog-1979-fixed.pdf|PDF]]
|Freedom, Night Rider, Black Jack, Mata Hari, Evil Knievel, Eight Ball, Lost World, Power Play, Strikes & Spares, Six Million Dollar Man
|

|-
|Bally
|1979-1 Parts Catalog
|[[file:bally-1979-1-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/wjsc/ Viewer] [[media:Bally-Parts-Catalog-1979-1.pdf|PDF]]
|Playboy, Supersonic, Star Trek, Kiss, Paragon
|

|-
|Bally
|1980 Parts Catalog
|[[file:bally-1980-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/afmm/ Viewer] [[media:Bally-Parts-Catalog-1980.pdf|PDF]]
|Harlem Globetrotters, Dolly Parton, Future Spa, Nitro Groundshaker, Silverball Mania, Rolling Stones, Space Invaders
|

|-
|Bally
|1980-1 Parts Catalog
|[[file:bally-1980-1-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/tzut/ Viewer] [[media:Bally-Parts-Catalog-1980-1.pdf|PDF]]
|Mystic, Hotdoggin', Viking, Skateball, Frontier, Xenon, Flash Gordon
|

|-
|Bally
|1981 Parts Catalog
|[[file:bally-1981-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/wurt/ Viewer] [[media:Bally-Parts-Catalog-1981.pdf|PDF]]
|Eight Ball Deluxe, Fireball II, Embryon, Fathom, Medusa, Centaur
|Note: Even though the parts catalog states otherwise, Fathom does use the sound board EE jumpers

|-
|Bally
|1982 Parts Catalog
|[[file:bally-1982-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/fimq/ Viewer] [[media:Bally-Parts-Catalog-1982.pdf|PDF]]
|Elektra, Vector, Rapid Fire, Mr. & Mrs. Pac Man, Spectrum, Speakeasy, BMX
|Note: Even though the parts catalog states otherwise, Fathom does use the sound board EE jumpers

|-
|Stern
|General Parts Book
|[[file:Stern-general-parts-book-cover.jpg|thumb|left|140px]]
|
|
|

|-
|Stern
|Parts Catalog (1979)
|[[file:stern-70s-parts-catalog-cover.jpg|thumb|left|140px]]
|[[media:Stern-parts-catalog-1979.pdf|PDF]]
|Pinball, Stingray, Stars, Memory Lane, Lectronamo, Wild Fyre, Nugent, Dracula, Trident, Hot Hand
|Service bulletins, diagnostic information, playfield parts, circuit board layouts & parts lists. Does not contain any playfield layout diagrams.

|-
|Stern
|1981 Parts Catalog
|[[file:Stern-1981-parts-catalog-cover.jpg|thumb|left|140px]]
|[[Media:Stern-parts-catalog-1981.pdf|PDF]]
|Pinball, Stingray, Stars, Memory Lane, Lectronamo, Wild Fyre, Nugent, Dracula, Trident, Hot Hand, Meteor, Galaxy, Magic, Cheetah, Quicksilver, Ali, Big Game, Seawitch, Star Gazer, Flight 2000, Nine Ball, Freefall, Lightning
|Includes playfield parts, but no board information or schematics. Includes information, parts lists, and diagrams for Stern video games.

|}

Note: Baby Pacman and Granny & The Gators do not specifically appear in the pinball parts catalogs, but many of the same parts are used on the playfield. The game specific manuals and the Vidiot and Vidiot Deluxe theory of operation manuals for each game will need to be referred in most cases for information about each game.

====Service Bulletins====
Service bulletins detailed any problems or issues with games that were discovered after they were released.

'''Service Bulletin Books'''
{| class="wikitable"
|-
!Manufacturer
!Version
!Cover
!Source
!Games
!Notes

|-
|Bally
|Service Bulletins, August 1978
|[[file:Bally-service-bulletin-book-1978-cover.png|thumb|left|140px]]
|[[media:Bally-service-bulletin-book-1978.pdf|PDF]]
|Black Jack, Eight Ball, Evel Knievel, KISS, Lost World, Mata Hari, Night Rider, Paragon, Playboy, Power Play, Six Million Dollar Man, Skateball, Star Trek, Strikes and Spares, Supersonic, Voltan
|

|-
|Bally
|Service Bulletin Book, 1987
|[[file:Bally-service-bulletin-book-1987-cover.png|thumb|left|140px]]
|[[media:Bally-service-bulletin-book-1987.pdf|PDF]]
|Kings of Steel, Spy Hunter, Fireball Classic, Cybernaut
|Also contains some early Bally 6803 games
|}

'''Individual Service Bulletins'''

Note: Stern Electronics service bulletins 1 through 16 can be found in the [[media:Stern-parts-catalog-1979.pdf|1979 Stern Parts Catalog]].

{| class="wikitable sortable"
|-
!Manufacturer
!Service Bulletin
!Date
!Game(s)
!Summary
!Notes
|-
|Stern
|[[media:Stern_service-bulletin_15.pdf|15]]
|1979
|All Games (General)
|Solid State Digit Display Repair Procedures
|
|-
|Stern
|[[media:Stern_service-bulletin-23.pdf|23]]
|1980-12-02
|Flight 2000
|Flight 2000 breaking flipper return plastic
|Fix: Insert metal bar under return plastic
|-
|}

===The Wiring Color Code===
The Bally color coding system is a carry over from the EM era. Either one color or a two color code is used for every wire. The first number is the wire's insulation color, while the second number is the trace color, if one is used. The traces on the wire can either be dashes or stripes. Either type of marking has the same coding designation. An example of a wire with the code 15, would be a red wire with a white trace. A black wire with no trace would be code 80. If a wire color is used more than once, a "-" and the "nth" time the color is used is added as a suffix to the color code. An example of this is a red wire with white traces used a second time. The code for the wire would be 15-1. 

Conversely, Stern never adopted a color coding system. Instead, the wire color was marked accordingly in the associated documentation, (ie. a white wire with a blue trace is referred to as W-BLU, red with yellow is R-Y, black is just B, etc.). 

Below is the Bally color chart. 

{| class="wikitable" style="margin: 1em auto 1em auto;"
!
!1
!2
!3
!4
!5
!6
!7
!8
!9
!0
!Jumper
|-
| Color
|| <center>  Red  </center>
|| <center>  Blue  </center>
|| <center>  Yellow  </center>
|| <center>  Green  </center>
|| <center>  White  </center>
|| <center>  Brown  </center>
|| <center>  Orange  </center>
|| <center>  Black  </center>
|| <center>  Gray  </center>
|| <center>  No Trace  </center>
|| <center>  Jumper  </center>
|}

===Connector Designations===
All Bally / Stern machines have a common naming convention for all of the connectors in the game. A specific connection uses two parts - a prefix and a suffix. The prefix is the board number, and the suffix is the connection on the board. When referencing a specific connector pin within a housing, a dash follows the connection number. For example, the connector pin for the coin door self test switch signal on the CPU board is A4J3-1. A single connection, in this case the key on a display, for the player 2 display would be 2A1-14. The same connection on a player 3 display would be 3A1-14. 

The following boards are assigned the same numbers throughout Bally / Stern games.
*Lamp Driver Board - A5
*MPU Board - A4
*Solenoid Driver Board - A3
*Transformer Module / Rectifier Board - A2
*Displays - A1
 

===Switch Matrix===
[[File:Bally Stern switch matrix.png|thumb|left|200px|Bally / Stern 5 x 8 Switch Matrix]] 

The Bally / Stern switch matrix is a 5 x 8 matrix consisting of a maximum of 40 switches. There are a total of 5 switch strobes (columns), (starting with 0, ending with 4), and 8 switch returns (rows), (starting with 0, ending with 7). The numbering convention for the switches is to start at 01, increase by 1 in the same strobe, and continue consecutively to 40. To isolate the switches, a 1N4004 diode, or in some cases a 1N4148 diode, is placed across the switch itself. Not every switch in the matrix is used on every Bally / Stern game. 

Although rare, Bally did add a 6th strobe (strobe 5) for some games, such as Centaur, Fathom, Medusa and Spectrum.
 

Connections for the switch matrix originate from the two connectors located on the right side of the CPU board. Connector A4J3 is used for all the switches on the coin door, the ball roll tilt, and the pendulum tilt. While connector A4J2 is for all of the switches on the playfield. 

{| class="wikitable"
!
!Strobe 0 
(A4J2-1 / A4J3-2) 
!Strobe 1 
(A4J2-2 / A4J3-3) 
!Strobe 2 
(A4J2-3) 
!Strobe 3 
(A4J2-4) 
!Strobe 4 
(A4J2-5)
!Strobe 5 (When Used) 
(A4J4-5)
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 0 (A4J2-8 / A4J3-9) 
| style="vertical-align: top; text-align: center;" | 01 
| style="vertical-align: top; text-align: center;" | 09 
| style="vertical-align: top; text-align: center;" | 17 
| style="vertical-align: top; text-align: center;" | 25 
| style="vertical-align: top; text-align: center;" | 33 
| style="vertical-align: top; text-align: center;" | 41 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 1 (A4J2-9 / A4J3-10) 
| style="vertical-align: top; text-align: center;" | 02 
| style="vertical-align: top; text-align: center;" | 10 
| style="vertical-align: top; text-align: center;" | 18 
| style="vertical-align: top; text-align: center;" | 26 
| style="vertical-align: top; text-align: center;" | 34 
| style="vertical-align: top; text-align: center;" | 42 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 2 (A4J2-10 / A4J3-11) 
| style="vertical-align: top; text-align: center;" | 03 
| style="vertical-align: top; text-align: center;" | 11 
| style="vertical-align: top; text-align: center;" | 19 
| style="vertical-align: top; text-align: center;" | 27 
| style="vertical-align: top; text-align: center;" | 35 
| style="vertical-align: top; text-align: center;" | 43 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 3 (A4J2-11 / A4J3-12)
| style="vertical-align: top; text-align: center;" | 04 
| style="vertical-align: top; text-align: center;" | 12 
| style="vertical-align: top; text-align: center;" | 20 
| style="vertical-align: top; text-align: center;" | 28 
| style="vertical-align: top; text-align: center;" | 36 
| style="vertical-align: top; text-align: center;" | 44 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 4 (A4J2-12 / A4J3-13) 
| style="vertical-align: top; text-align: center;" | 05 
| style="vertical-align: top; text-align: center;" | 13 
| style="vertical-align: top; text-align: center;" | 21 
| style="vertical-align: top; text-align: center;" | 29 
| style="vertical-align: top; text-align: center;" | 37 
| style="vertical-align: top; text-align: center;" | 45 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 5 (A4J2-13 / A4J3-14) 
| style="vertical-align: top; text-align: center;" | 06 
| style="vertical-align: top; text-align: center;" | 14 
| style="vertical-align: top; text-align: center;" | 22 
| style="vertical-align: top; text-align: center;" | 30 
| style="vertical-align: top; text-align: center;" | 38 
| style="vertical-align: top; text-align: center;" | 46 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 6 (A4J2-14 / A4J3-15) 
| style="vertical-align: top; text-align: center;" | 07 
| style="vertical-align: top; text-align: center;" | 15 
| style="vertical-align: top; text-align: center;" | 23 
| style="vertical-align: top; text-align: center;" | 31 
| style="vertical-align: top; text-align: center;" | 39 
| style="vertical-align: top; text-align: center;" | 47 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 7 (A4J2-15 / A4J3-16) 
| style="vertical-align: top; text-align: center;" | 08 
| style="vertical-align: top; text-align: center;" | 16 
| style="vertical-align: top; text-align: center;" | 24 
| style="vertical-align: top; text-align: center;" | 32 
| style="vertical-align: top; text-align: center;" | 40 
| style="vertical-align: top; text-align: center;" | 48 
|}

It is worth mentioning that the self test switch, which is located on the inside of the coin door and used to enter tests, audits, and bookkeeping, is not part of the switch matrix. A single signal is sent to the self test switch from the U10 PIA on the CPU board via connection A4J3-1, and returned to ground via a connection A3J2-7 on the solenoid driver board. 

Also, the switch commonly referred to as "switch 33" on a Bally or Stern CPU board, and used to reset audits and bookkeeping, is not part of the switch matrix either. This switch receives a signal from the 6800 CPU chip, and when closed, sends the signal to ground. Starting with the first MPU-200 Stern game, Meteor, Stern added a second switch to the inside of the coin door to serve the purpose of remotely resetting audits and bookkeeping. The signal for this secondary switch is tied to the input line of switch 33, and leaves the CPU board via connection A4J3-5. Its return line is sent to ground via a daisy-chained lead to the self test switch.
 

===Bally and Stern MPU Boards===
<gallery widths=300px heights=300px>
File:Bally -17 MPU.JPG|Bally AS-2518-17 MPU Board
File:Bally -35 MPU.JPG|Bally AS-2518-35 MPU Board
File:Bally-6802-mpu-board.jpg|Bally 6802 MPU Board (A080-91638-D000). Note alkaline corrosion abatement and addition of "SuperCap" to retain CMOS memory
</gallery>
<gallery widths=300px heights=300px>
File:Mpu100-01.jpg|Stern M-100 MPU Board
File:Mpu200-01.jpg|Stern M-200 MPU Board
</gallery>
All Bally and Stern MPU boards are built around the Motorola 6800 series CPU chip and 6820 or 6821 peripheral interface adapters (PIAs).

In most cases, if a Bally MPU board has taken a bad hit from alkali damage, the bottom right corner of the board typically takes a hit. Unfortunately, the bottom right corner of the board is also the location where the board number is stenciled onto the masking. If the masking has delaminated, it will take the stenciled board number information with it. At this point, it would be difficult to determine what board it actually is.

[[File:Bally -17 Quick ID.JPG|left|300px|thumb|32 pins at J5 of a -17 MPU]]
[[File:Bally -35 Quick ID.JPG|right|300px|thumb|33 pins at J5 of a -35 MPU]]

However, there is a quick and easy way to determine whether the board is either a -17 or -35. Simply look at the J5 header pin connection located at the top center of the board. If there are only 32 pins (including one empty key) at the connection, the board is a -17. If there are 33 pins (including one empty key) at this connection, the board is a -35.

The Bally 6802 MPU board was only found in two games (Fireball Classic and Cybernaut) and in small quantities before the introduction of [[Bally_6803|6803 games]]. Some specifics of the 6802 board [http://www.pinball4you.ch/okaegi/pro_6802.html can be found here].
 

====Bally -35/Stern MPU-200 Parts Bill of Materials and Part Placement Chart====
[[File:CorrosionArea.jpg|300px|thumb|left|Bally -35/Stern MPU-200 Parts Bill of Materials|link=https://www.pinwiki.com/wiki/images/5/54/BallySternMPUPartsBOMandLocator.pdf]] 
Clicking on the thumbnail at left will open a .pdf file detailing the part location and complete bill of materials for Bally -35 and Stern MPU-200 MPU boards. The original parts "skeleton layout" and BOM was done by Ed at [http://www.greatplainselectronics.com Great Plains Electronics].
 

===Transformers===
{|class="wikitable"
! scope="col" | Manufacturer
! scope="col" | Part Number
! scope="col" | Power Transformer Module
! scope="col" | Rectifier Board Assembly
! scope="col" | Winding 1
! scope="col" | Winding 2
! scope="col" | Winding 3
! scope="col" | Winding 4
! scope="col" | Winding 5
|-
|Bally || E-122-125 || AS-2877, AS2877-1 || AS-2518-18 || 49VAC || 173VAC || 7.3VAC || 7.8VAC || 12VAC
|-
|Bally || E-122-131 || AS-2877-3 || AS-2518-49 || 49VAC || 173VAC || 7.3VAC || 9.2VAC || 12VAC
|-
|Bally || E-122-141 / AS-3071-2 || AS-2877-6 || AS-2518-54 || 49VAC || 170VAC || 6.5VAC || 8.2VAC || 14.2VAC
|-
|Bally || E-122-142 / AS-3071-2 || AS-2877-6 || AS-2518-54 || 49VAC || 170VAC || 6.5VAC || 9.4VAC || 14.2VAC
|-
|Bally || E-122-170 / AS-3071-15 ‡ || AS-2877-13 ‡ || AS-2518-151 ‡ || 49VAC || 170VAC || 8.5VAC || 20V CT † || 14.2VAC
|-
|Bally || AS-3071-12 § || AS-2877-11 § || AS-2518-132 § || || || || ||
|}

{|class="wikitable"
! scope="col" | Manufacturer
! scope="col" | Part Number
! scope="col" | Rectifier Board Assembly
! scope="col" | Lugs 2/4/6
! scope="col" | Lugs 8/10
! scope="col" | Lugs 13/14
! scope="col" | Lugs 15/16
! scope="col" | Lugs 17/18
|-
|-
|Stern|| 16B-3 || TA-100 || 49VAC || 173VAC || 7.8VAC || 12VAC || 7.3VAC
|-
|Stern|| 16B-6 || TA-100 || 49VAC || 173VAC || 7.8VAC || 12VAC || 7.3VAC

|}
† Center Tapped 
‡ Goldball and Grand Slam only. 
§ Baby Pacman and Granny & The Gators only

===Rectifier Boards===
====AS-2518-18 Schematic====
[[File:ClassicBallySternRectifierBoardSchematic.jpg|400px|left|thumb|Bally AS-2518-18 Rectifier Board Schematics]] 
Click on the image at left to show the schematic for the AS-2518-18 Rectifier Board (square board).
 
====Models====
The rectifier board is the first part of the power train in any Bally or Stern machine. In addition to rectifying four discrete AC voltages to DC, the rectifier board consists of the bulk of fuses for the game, including the main fuse. After all associated voltages are fused, the power is dispersed to the backbox, playfield, and lower cabinet.

There are two revisions of the AS-2518-54 rectifier board. The first revision has 5 fuses. Revision "B" has an additional fuse. On revision B, two fuses are used for the general illumination instead of just one fuse. One fuse is for the GI on the playfield, and the second fuse for the GI in the backbox. The AS-2518-132 rectifier board (used only in [[Baby Pac-Man]] and Granny & The Gators) is based on the AS-2518-54 revision B board.

The AS-2518-132 rectifier board is only used in Bally's two hybrid games--[[Baby Pac-Man]] and Granny & The Gators. The AS-2518-132 board backwards compatible with the AS-2518-54 board. However, in order to use a standard AS-2518-54 board in a hybrid game, the rectifier diodes at CR5, CR6, CR7, and CR8 need to be upgraded from the stock 3 Amp diodes to 6 Amp diodes.

<gallery widths=250px>
File:Bally AS-2518-18 Rec Brd.JPG|Bally AS-2518-18 Rectifier Board
File:Bally_-49_rectifier_board.jpg|Bally AS-2518-49 rectifier board
File:Bally AS-2518-54 Front.JPG|Bally AS-2518-54 Rectifier Board
File:Bally AS-2518-54 revision B.JPG|Bally AS-2518-54 Revision B Rectifier Board. Two fuses are used for the general illumination instead of one (the GI for the playfield and the GI for the backbox)
File:Bally_AS-2518-132.jpg|Bally AS-2518-132 Rectifier Board. Only used in Baby Pacman and Granny & The Gators.
File:Bally AS-2518-151 Rec Board.JPG|Bally AS-2518-151 Rectifier Board
</gallery>
 

<gallery widths=250px>
File:Stern TA-100 Rec Brd.JPG|Early Stern TA-100 Rectifier Board
File:Stern TA-100 Newer.JPG|Later Stern TA-100 Rectifier Board
File:Stern TA-100 Rec Brd Blank.JPG|Later Stern TA-100 Rectifier Board (blank)
</gallery>
 

====How To Hook Up a Bally AS-2518-18 Rectifier Board====
Often folks buy a new or used rectifier board and then when they get it, they realize that they have to hook it back up to the old wiring harness. If this is you, and you forgot to take notes or pictures before you removed your old board, then here you go. The photo below shows an original [http://stevekulpa.net/pinrepair/as-2518-18a.jpg AS-2518-18] rectifier board connected to a factory wiring harness. As far as I know, the wire colors are the same for ALL AS-2518-18 applications. 

[[File:As-2518-18-wiring.jpg|350px|left|thumb|Bally AS-2518-18 Rectifier Board (Solder Side)]]

{| class="wikitable" style="margin: 1em auto 1em auto;"
!Board Connection
!Wire Color / Gauge
!Transformer Lug
!Circuit
|-
|E1 || Red 18 AWG || 5 || Primary AC Hot
|-
|E2 || Yellow 18 AWG || 1 || Primary Neutral
|-
|E3 || Red 20 AWG || 2 || Solenoid Bus Hot
|-
|E4 || White/Red 20 AWG || 6 || Solenoid Bus Neutral
|-
|E5 || Green 20 AWG || 8 || Display High Voltage Hot
|-
|E6 || White/Green 20 AWG || 10 || Display High Voltage Neutral
|-
|E7 || Blue 18 AWG (2 wires) || 17 || GI Bus Hot
|-
|E8 || Black 18 AWG (2 wires) || 18 || GI Bus Neutral
|-
|E9 || Orange 18 AWG || 13 || Controlled Lamp Bus Hot
|-
|E10 || Green 18 AWG || 14 || Controlled Lamp Bus Neutral
|-
|E11 || White 20 AWG || 15 || 12V Input for 5-Volt Regulator Hot
|-
|E12 || White/Black 20 AWG || 16 || 12V Input for 5-Volt Regulator Neutral
|}
 
AWG = American Wire Gauge (18 = fat, 20 = skinny) 

"E" solder pads are labeled on the top side of the circuit board
 

====How To Hook Up a Stern TA-100 Rectifier Board====
[[File:Stern-ta100-16b-6.png|300px|left|thumb|Stern TA-100 Rectifier Wire Color connections]] 
As mentioned above when you replace or remove and reattach your rectifier board you need to know how to hook it back up. I have done this with a lot of Stern pins and made myself a chart for quick and easy reference when re-attaching the rectifier to the transformer. I figured it may be useful to others as well.
 

====How To Properly Mount a Bally AS-2518-54 Rectifier Board====
[[File:Bally-54mount01.jpg|200px|left|thumb|Bally AS-2518-54 Rectifier Board]]
[[File:Bally AS-2518-54 Back.JPG|200px|right|thumb|Bally AS-2518-54 Rectifier Board (back)]] 

The Bally AS-2518-54 rectifier board normally mounts on a large metal plate found in the bottom of the pinball machine’s cabinet. It uses the metal plate as a heat sink for the two large bridge rectifiers on the underside of the board, so mounting it properly is important. Carefully following the steps illustrated below will ensure the board is correctly mounted for long term reliability.
 

<center>
<gallery widths=300px heights=200px perrow=3 caption="Mounting a Bally -54 rectifier board">
File:Bally-54mount02.jpg|<center>Locate the two mounting holes for the bridge rectifiers, circled in red, and the seven mounting holes for the circuit board, circled in yellow.</center>
File:Bally-54mount03.jpg|<center>Practice laying the board in the proper position once, so you’re sure you know where it goes. You want the two holes that go through the bridge rectifiers to line up with the holes in the plate. Also make sure the mounting screws around the edge of the board are lining up with their holes too.</center>
File:Bally-54mount04.jpg|<center>Prep the surface of the mounting plate by cleaning the area, where the two bridges will mount, with some alcohol or acetone.</center>
File:Bally-54mount05.jpg|<center>Make a circle of heat sink grease around each bridge mounting screw hole approximately the diameter of a dime. Heatsink grease is available from most all the popular vendors.</center>
File:Bally-54mount06.jpg|<center>Carefully place the rectifier board in back on the mounting board. You want to get the board positioned as best as you can without moving it around a lot or you will smear the heat sink grease all over the place. What I like to do is peek through one of the two mount holes on the board and locate the corresponding screw hole on the plate. Then as you peek through this hole, guide the board into place while keeping the screw hole in sight.</center>
File:Bally-54mount07.jpg|<center>Double check your work, being careful not to move the board around too much. To avoid smearing the heat sink grease, it’s best if you can place it directly into the proper position the first time, without having to scoot it around afterwards.</center>
File:Bally-54mount08.jpg|<center>Next, start the two mounting screws that go through the bridge rectifiers, but do not tighten them all the way.</center>
File:Bally-54mount10.jpg|<center>Now locate and install the remaining seven mounting screws along the perimeter of the board, but don’t tighten them all the way yet. Since all the screws are a little loose, you have a little bit of board movement available to help locate the mounting screw holes on the plate.</center>
File:Bally-54mount11.jpg|<center>Once all the perimeter screws are in place, tighten the two bridge rectifier screws. You want them nice and tight so it spreads the heat sink grease into a nice, evenly spread thin layer. Just be careful that you don’t strip the threads out of the mounting holes. Then tighten up the perimeter screws after that. All done!</center>
File:Bally-54mount12.jpg|<center>One word of warning: The mounting screws protrude way past the bottom of the board, so be careful where you place this assembly. The screws may scratch your workspace (a nice table, countertop, etc.).</center>
</gallery>
</center>
 
====Pinout for Rectifier Board Connectors J1, J2, J3====
[[File:BallySternRectifierBoards.jpg | thumb | left| 300px| Diagram originally authored by PinSider Quench. Used by permission.]]
[[File:RectifierBoardsStern.jpg | thumb | right| 300px| Diagram originally authored by PinSider Quench. Used by permission.]] 
A frequently asked question when working on Bally and Stern rectifier boards is, "can someone post a picture of their wiring"?

These diagrams provide the wire colors and locations for Bally (left) and Stern (right) rectifier boards.

The original diagrams, plus an addendum regarding Bally Kiss, Space Invaders, and Future Spa (which used the AS-2518-49 rectifier board) can be found in the PinSide thread [https://pinside.com/pinball/forum/topic/bally-rectifier-board-j3-pinout-paragon here].

Note: Wire gauge is also indicated in each diagram. Thicker wires (for GI for example) are drawn thicker.
 

===Bally and Stern Solenoid Driver Board===
[[File:As-2518-16.jpg|200px|thumb|left|Bally AS-2518-16 Solenoid Driver/Regulator]]
[[File:As-2518-22.jpg|200px|thumb|right|Bally AS-2518-22 Solenoid Driver/Regulator]]
[[File:Stern-sdu100a.jpg|200px|thumb|left|Stern SDU-100 Solenoid Driver/Regulator]]
[[File:Stern-sdu100b.jpg|200px|thumb|right|Another style of the Stern SDU-100 Solenoid Driver/Regulator (Revision B)]]

First of all, everything mentioned in the following sections specifically reference the Bally AS-2518-22 solenoid driver board, found in most Bally pins from 1977 through 1985. Since the Bally AS-2518-16 and Stern SDU-100 boards are very similar, and all are identical as far as the operation of the solenoid driver circuits, the information is applicable to these boards as well. The main differences between Bally and Stern solenoid driver boards used from the factory are the physical layout of parts, and whether or not the board is single-sided or double-sided. Since the physically connector locations are the same, Bally and Stern solenoid driver boards are similar enough to be interchangeable. 

Secondly, if all this is Greek and you have no idea how decoder ICs work, or what a transistor is, take a look at the [http://www.pinwiki.com/wiki/index.php?title=Bally/Stern#How_Bally_Coils_are_Driven_for_Dummies How Bally Coils are Driven for Dummies] section to learn the basics of how things work. 

Third, the solenoid driver board actually has three functions.
#Drive the solenoid and relay coils of a pinball machine.
#Regulate the logic voltage which provides a nice and steady +5VDC to the other boards for their various logic circuits.
#Regulate the high voltage (+190 VDC) for the display driver boards

The regulated voltage will not be discussed here, only the solenoid drive section. 

Finally, don't forget that the Solenoid Driver board contains the high voltage circuitry for the displays. There is 190 volts DC here and if you're not careful, you'll get knocked on your butt. '''A shock from 190 volts DC will hurt.''' If you don't know what you're doing, stay away from it and have a professional fix it instead. In addition to high voltages, there are static sensitive parts on these boards. While working on boards, be sure to properly ground yourself before touching the board, and always work in a static-free workspace.
 

====Stern Driver Board Revisions====
There are several versions of the Stern SDU-100 driver board. Revision A is the most radically different than all the other versions, since it has a blue solder mask and hand-drawn traces. This revision can have either "Rev 1" or "Rev 2" printed on the board below the "SDU-100" label.

Revision B is marked as "B432" in the lower right hand corner. There is a lot of extra masking and labels on this board that are not seen on any other revisions.

Revision C is is marked as "Revision C" in the center of the board. A fuse was added for the high voltage section for the displays. However, this fuse was proven to be largely useless, and did not blow if there was a short in the high voltage section's regulation transistors.

The final revisions of the board lacked a fuse, but included a shutdown transistor in the high voltage section intended to cut the high voltage power if there is a short in this section (however, this is not always successful depending on where the short is). The later revisions went up to revision D, and possibly E or F, but this is currently unconfirmed.

<gallery widths=250px>
file:Stern-sdu100a.jpg|SDU-100 Revision A (Rev 1 and Rev 2)
file:Stern-sdu100b.jpg|SDU-100 Revision B (B432)
file:stern-sdu-100-rev-c-front.jpg|SDU-100 Revision C
file:placeholder.jpg|SDU-100 Revision D/E/F?
</gallery> 

====How Bally Coils are Driven for Dummies====
[[File:Ballycoil1.jpg|200px|right|thumb|Typical Bally Coil (Mata Hari)]] 
There are three main characteristics regarding the coils and coil connections in Bally games.
*Two large gauge yellow wires going to one lug (mostly two wires as the wire is "daisy chained" from coil to coil).
*One small gauge wire going to the other lug.
*A diode soldered across the two lugs, with the "banded" end of the diode facing the yellow wires (power).

The majority of information in this section is applicable to Stern games too. Bally and Stern solenoid driver boards are similar enough in overall design for them to interchange between games / manufacturers. The only other primary difference between Bally and Stern is the wire color of the solenoid bus line in most cases.
 

One lug on every coil is connected via a parallel circuit by the fatter wires. This type of connection is also commonly referred to as a daisy-chained circuit. These fat wires supply each coil with positive 43 volts DC (+43VDC), so each coil is connected to the +43VDC bus. Most have two fat wires, but some may only have one. Flipper coils have these wires too, but they are connected a little differently, and are discussed elsewhere. For now, just assume regular solenoids are being discussed here. 

Each coil has a small skinny wire on the other lug. This wire goes to the control circuits on the solenoid driver board. In order to energize the coil, there must be a path to ground for the +43VDC. In its at rest state, the coil does not have a path to ground. When the small skinny wire gets connected to ground, the path is complete and current will flow. This current flow turns the coil into an electro-magnet, which then pulls the plunger into the coil. When the wire is disconnected from ground, current flow stops, the electro-magnet is turned off, and the plunger returns to it's normal position with help from either a spring or gravity. 

Finally, there is a diode on each coil. When the current is quickly turned off on an energized coil, the magnetic field around the coil collapses quickly. This action causes the coil to generate a huge voltage spike. The job of the diode is to prevent the majority of this spike from reaching the solenoid driver circuity. If the diode is bad (shorted) or installed backwards, the drive transistor will be destroyed the very first time the coil is energized, then released. The process is similar to the ignition system used in older cars. When the points open, the 12 volts is removed from the car's coil quickly, which causes another coil to generate a huge voltage spike to the spark plug.
 

[[File:Ac-dc43.jpg|200px|left|thumb|Comparison of Electrical Sine Waves]] 
The computer program that runs the machine also tries to limit this spike by turning off the coil near the zero crossing of the AC line. This helps because the DC that drives the coils is rectified, but not filtered, so it's not smooth DC, but "humpy", as shown in the adjacent picture. 

By energizing the coils just after the zero crossing, the in-rush of current caused by a coil is limited. By turning the coils off just after the zero crossing, the voltage spike caused by the collapsing field is also kept to a minimum.
 

[[File:Bsoledraw1.jpg|200px|left|thumb|Depiction of Multiple Coils in a Bally Game with Manual Switches Inserted and tied to Ground]] 
So, in the simplest form, the solenoid driver circuits in a Bally game look like what is shown in the accompanying pic. Look at it as a bunch of coils all connected to the +43VDC bus, and the other lugs going to switches which are connected to ground. If a switch were to close, it would connect the circuit from +43VDC to ground, and the coil would energize as long as the switch is closed.
 

[[File:Bsoledraw2.jpg|200px|left|thumb|One Switch Closed and Energizing the Coil]] 
See how the circuit is complete due to the switch being closed, and the coil is energized. When the switch is opened again, the coil turns off, and is returned to the same state as the previous picture. If the diode were not there, there would be a big arc across the switch contacts upon the moment they opened up.
 

[[File:Bsoledraw3.jpg|200px|left|thumb|Depiction of Multiple Coils in a Bally Game with Transistors Shown]]
Now, take this one step further, and replace the manual switches with transistors. Transistors are normally used as amplifiers, but you can also use them as switches too. There are 3 leads on a transistor, the base, the emitter, and the collector. For NPN transistors like the ones on the Bally solenoid driver, the emitter and collector can be used like a switch. With no current supplied to the base, there is no current flow between the collector and emitter - the transistor switch is open, or OFF. If current is supplied to the base, the current will then flow between the collector and emitter, so now the switch is closed, or ON. 

Without getting into too much detail - what happens is a current is applied to the base which is high enough to 'saturate' the transistor. This means the collector-to-emitter current will be amplified as high as it can, and the transistor will then conduct a large amount of current from COLLECTOR to EMITTER, in relation to the current flow from the BASE to the EMITTER. This is how it acts like a switch. The base goes high to turn it on, and low to turn it off. Since the collector is connected to the wire that goes to the coil (the small single wire), and the emitter is connected to ground, turning the transistor has the effect of connecting the collector to ground. This completes the circuit to the coil and it turns on (fires).
 

A coil can be tested by momentarily grounding the tab on the coil's drive transistor. For the TIP-102 or similar transistors used in the Bally solenoid driver, the metal tab is connected to the collector. Knowing this, and what was just discussed, grounding the tab is the same as grounding the collector, which will complete the circuit to ground and fire the coil. However, this test only tests the wiring from the solenoid driver to the coil. It '''DOES NOT''' test the transistor itself or any circuitry before the transistor. 

The transistor and "control signal" in the simplified drawing above can be replaced with the actual circuit. More details regarding this circuit are found in the following section.
 

====Overview====
Two circuit boards will be discussed: the MPU board (AS-2517-17 or -35) and the Solenoid Driver board (AS-2518-22 or -16). The solenoid driver gets signals from the MPU board. These signals tell the solenoid driver which solenoid to fire. Up to 15 momentary and 4 continuous solenoids can be controlled by the solenoid driver. The flipper solenoids are enabled or disabled from the solenoid driver too, but are not controlled like the other solenoids.
 

====How the Solenoid Driver Works====
The solenoid driver is responsible for energizing the solenoid coils of the pinball machine. Four signals from the U11 PIA integrated circuit on the MPU board travel out from the J4 to the J4 connector on the Solenoid Driver board. These four signals tell the Solenoid Driver which solenoid to fire. This is accomplished by using a decoder chip that takes the binary pattern of the four signals (16 different patterns) and decodes (or demultiplexes) them into one of sixteen different outputs. The four signals are applied to the decoder then the decoder is strobed. Normally, all sixteen of the decoder output lines are held high (+5vdc). When strobed, the decoder lowers one of it's sixteen output lines, depending on the pattern of the four input signals. Detailed info about the 74LS154 decoder chip is availalbe [http://www.datasheetcatalog.org/datasheets/134/231586_DS.pdf here]. 

[[File:B_solenoid1.jpg|200px|thumb|left|Typical Solenoid Driver Circuit]]
With no input supplied (strobe is high), the output lines of the decoder are high (+5 vdc). This puts a voltage at the base of Q1 (this transistor is one of seven in the CA3081 transistor array chip). This turns Q1 "on" and the voltage supplied to it's collector via resistor R1 passes through the transistor to ground. At this point, little or no voltage is present at the base of Q2, and Q2 is "off". With Q2 off, the 40vdc at the coil has no place to go, and the coil remains deenergized. 

When the MPU board supplies the proper input signals (A-B-C-D) to the decoder, and the decoder is strobed (signal drops to low), the proper output signal will go low, which turns Q1 "off" (notice one of the two strobe lines goes to ground, so it's always low). This allows the +5vdc at Q1's collector to flow through the diode instead of Q1 on it's way to ground via resistor R3. This also puts a voltage at the base of Q2 and turns this transistor "on". When Q2 turns on, the 40vdc at the solenoid now has a path to ground through Q2 and current flows through the coil, thereby energizing it. Then the strobe to the decoder is released, the decoder output goes high again, Q1 turns on, Q2 turns off, and everything is back to normal.
 

Diode D1, resistor R3 and capacitor C1 work to slow the speed at which Q2 and the solenoid are able to turn off. This is important to prevent the "inductive kick" voltage that builds up when you try to turn off a solenoid quickly. A solenoid coil can build up hundreds of volts if it is switched off too quickly. For example, the spark in the spark plug of a car is generated from this inductive kick when the ignition coil is turned off quickly. In this case, D1 allows Q2 and the solenoid to turn ON quickly (which is OK) because the current that used to be flowing through Q1 can now flow forward through D1 and turn on Q2 quickly. However, when the decoder output goes back to high and Q1 turns back on, D1 prevents the charge from the base of Q2 from being sucked down Q1. The charge on C1 must drain off (slowly) through R3 and the base of Q2. This takes awhile and slows the turn-off of Q2 and the solenoid COIL, thus reducing the kick. Also, as the solenoid turns off and the voltage on the collector of Q2 starts to rise, this voltage is "fed back" by C1 to the base of Q2 and tends to keep Q2 on a little longer, slowing the turn-off of the solenoid even more. The OTHER diode (D2, across the solenoid) works to absorb the solenoid's turn-off kick by conducting when the voltage on the collector of Q2 is greater than about 40 volts.
 

====Pinout for Solenoid Driver Board Connector J3====
[[File:BallySolenoidDriverJ3ViaQuench.png | thumb | left| 300px| Diagram originally authored by PinSider Quench. Used by permission.]] 
A frequently asked question when working on Bally solenoid driver boards is, "can someone post a picture of their wiring"?

This diagram provides the wire colors and locations for Bally solenoid driver boards, connector J3 (25 pins, .100).
 

===Lamp Driver Board===
Bally and Stern controlled lamps are driven discretely via SCRs located on the lamp driver board. Because of this, neither manufacturer utilizes a lamp matrix. Any variation of the lamp driver boards are capable of controlling a maximum of 60 discrete lamp circuits. Typically the 2N5060 SCRs can only control one lamp, while the MCR106 / SCR106 / C106 SCRs can control up to two lamps. 

The first generation of both the Stern and Bally lamp driver boards has 4050 hex buffer chips installed between the 4514s and the MCR106 SCRs. It is unknown why both companies chose to remove these chips from later designs. 

<center>
<gallery widths=300px heights=300px perrow=3 caption="Bally Lamp Driver Boards">
File:Bally AS-2518-14 LDB.JPG|<center>AS-2518-14, Rev. 2</center>
File:Bally AS-2518-23 LDB.JPG|<center>AS-2518-23</center>
File:Bally AS-2518-23 LDB rev 1.jpg|<center>AS-2518-23, Rev. 1</center>
File:Bally AS-2518-23 LDB A000.jpg|<center>AS-2518-23, A000</center>
File:AS-2518-23PinsOnly.jpg|<center>AS-2518-23, A000, no header pin carriers</center>
File:AS-2518-23PinsOnlyPinsRemoved.jpg|<center>AS-2518-23, A000, with pins removed for replacement</center>
File:AS-2518-23PinsOnlyPinsReplaced.jpg|<center>AS-2518-23, A000, "pins only", replaced</center>
</gallery>
</center>
 
<center>
<gallery widths=300px heights=300px perrow=3 caption="Stern Lamp Driver Boards">
File:Stern LDA 1st Ver.JPG|<center>LDA-100</center>
File:Stern LDA-100 2nd Ver.JPG|<center>LDA-100 Rev. B</center>
File:Stern LDA-100 RevC.JPG|<center>LDA-100 Rev. C</center>
</gallery>
</center>
 
====Lamp Driver Board Connector / SCR Mapping====

{| class="wikitable sortable"
! SCR !! Connector !! Wire Color Code !! Wire Color !! SCR Type
|-
| Q10 || J1-15 || 13 || Red-Yel || MCR-106
|-
| Q22 || J1-10 || 32 || Yel-Blu || MCR-106
|-
| Q37 || J3-23 || 98 || Gry-Blk || 2N5060
|-
| Q60 || J3-03 || 81 || Blk-Red || 2N5060
|-
| Q11 || J1-16 || 12 || Red-Blu || 2N5060
|-
| Q26 || J1-07 || 34 || Yel-Grn || 2N5060
|-
| Q32 || J3-27 || 40 || Grn || 2N5060
|-
| Q54 || J3-11 || 20 || Blu || MCR-106
|-
| Q49 || J3-17 || 27 || Blu-Orn || MCR-106
|-
| Q06 || J2-14 || 12 || Red-Blu || 2N5060
|-
| Q19 || J2-15 || 32 || Yel-Blu || 2N5060
|-
| Q31 || J2-02 || 20 || Blu || 2N5060
|-
| Q45 || J2-01 || 60 || Brn || 2N5060
|-
| Q16 || J2-22 || 62 || Brn-Blu || MCR-106
|-
| Q14 || J1-18 || 58 || Wht-Blk || 2N5060
|-
| Q29 || J1-01 || 41 || Grn-Red || 2N5060
|-
| Q36 || J3-26 || 38 || Yel-Blk || 2N5060
|-
| Q57 || J3-01 || 10 || Red || 2N5060
|-
| Q12 || J1-19 || 60 || Brn || 2N5060
|-
| Q27 || J1-09 || 52 || Wht-Blu || 2N5060
|-
| Q38 || J3-25 || 36 || Yel-Brn || 2N5060
|-
| Q50 || J3-12 || 21 || Blu-Red || 2N5060
|-
| Q13 || J1-17 || 57 || Wht-Orn || 2N5060
|-
| Q28 || J1-08 || 51 || Wht-Red || 2N5060
|-
| Q44 || J3-19 || 67 || Brn-Orn || 2N5060
|-
| Q53 || J3-14 || 84 || Blk-Grn || 2N5060
|-
| Q39 || J3-24 || 72 || Orn-Blu || 2N5060
|-
| Q21 || J1-12 || 61 || Brn-Red || 2N5060
|-
| Q05 || J2-16 || 34 || Yel-Grn || 2N5060
|-
| Q18 || J2-20 || 35 || Yel-Wht || 2N5060
|-
| Q30 || J2-06 || 85 || Blk-Wht || 2N5060
|-
| Q43 || J2-07 || 91 || Gry-Red || 2N5060
|-
| Q52 || J3-13 || 13 || Red-Yel || 2N5060
|-
| Q51 || J3-15 || 53 || Wht-Yel || 2N5060
|-
| Q33 || J2-11 || 95 || Gry-Wht || MCR-106
|-
| Q15 || J2-23 || 97 || Gry-Orn || MCR-106
|-
| Q23 || J2-08 || 93 || Gry-Yel || MCR-106
|-
| Q58 || J3-02 || 95 || Gry-Wht || 2N5060
|-
| Q20 || J1-13 || 96 || Gry-Brn || 2N5060
|-
| Q03 || J2-21 || 47 || Grn-Orn || MCR-106
|-
| Q40 || J3-22 || 23 || Blu-Yel || MCR-106
|-
| Q46 || J3-18 || 56 || Wht-Brn || 2N5060
|-
| Q41 || J3-20 || 64 || Brn-Grn || MCR-106
|-
| Q17 || J1-11 || 65 || Brn-Wht || MCR-106
|-
| Q56 || J3-10 || 91 || Gry-Red || MCR-106
|-
| Q42 || J3-21 || 30 || Yel || MCR-106
|-
| Q47 || J2-10 || 98 || Gry-Blk || MCR-106
|-
| Q09 || J1-14 || 54 || Wht-Grn || MCR-106
|-
| Q34 || J1-02 || 43 || Grn-Yel || MCR-106
|-
| Q08 || J1-23 || 56 || Wht-Brn || MCR-106
|-
| Q01 || J1-24 || 50 || Wht || MCR-106
|-
| Q02 || J1-25 || 90 || Gry || MCR-106
|-
| Q07 || J1-27 || 53 || Wht-Yel || 2N5060
|-
| Q04 || J1-28 || 78 || Orn-Blk || 2N5060
|-
| Q35 || J1-03 || 45 || Grn-Wht || MCR-106
|-
| Q24 || J1-05 || 48 || Grn-Blk || MCR-106
|-
| Q25 || J1-06 || 25 || Blu-Wht || 2N5060
|-
| Q48 || J3-16 || 25 || Blu-Wht || MCR-106
|-
| Q59 || J3-04 || 14 || Red-Grn || 2N5060
|-
| Q55 || J3-09 || 15 || Red-Wht || MCR-106
|-
| Q23 || J1-04 || 35 || Yel-Wht || MCR-106
|-
| Key || J1-20 || -- || ---- || Key
|-
| N/U || J1-21 || -- || ---- || N/U
|-
| N/U || J1-22 || -- || ---- || N/U
|-
| Q53 || J2-03 || 84 || Blk-Grn || 2N5060
|-
| Q39 || J2-04 || 72 || Org-Blu || 2N5060
|-
| Q52 || J2-05 || -- || ---- || 2N5060
|-
| Q21 || J2-12 || 61 || Brn-Red || 2N5060
|-
| Q07 || J2-13 || 53 || Wht-Yel || 2N5060
|-
| N/U || J2-17 || -- || ---- || N/U
|-
| Key || J2-18 || -- || ---- || Key
|-
| N/U || J2-19 || -- || ---- || N/U
|-
| N/U || J3-05 || -- || ---- || N/U
|-
| N/U || J3-06 || -- || ---- || N/U
|-
| N/U || J3-07 || -- || ---- || N/U
|-
| Key || J3-08 || -- || ---- || Key
|-
| N/U || J3-28 || -- || ---- || N/U
|-
| Q40 || J2-09 || -- || ---- || MCR-106
|-
| Q03 || J1-26 || 91 || Gry-Red || MCR-106
|}
 

===Combination Solenoid / Lamp Driver Board===
Two different solenoid driver boards were used in some later games. Both of these solenoid driver boards are a combination solenoid driver board, lamp driver board, and where the +5v regulation. The difference between the two in essence is one has a high voltage section for displays, while the other does not.

====AS-2518-107 Combination Solenoid / Lamp Driver Board====
[[File:AS-2518-107.jpg|300px|left|thumb|Bally AS-2518-107 Combination Solenoid/Lamp Driver Board. This board integrates 5V regulation, along with lamp and coil drivers--all onto a single board.]] 
The AS-2518-107 board was used only in two games: Baby Pac-Man and Granny and the Gators. The reason for its development is that both games are hybrid pinball / video games with smaller playing areas. Therefore, neither game needed all of the overhead that a standard pinball had, and there were less solenoids (10). Likewise, the lack of a high voltage section on this board is because these games use video monitors and did not have plasma displays. It appears that there is a lesser amount of lamp drivers (30) also, however, that total is deceiving. The difference between this board and the previous lamp driver boards is that previous boards had one SCR per lamp drive. This board controls two lamps (multiplexed) per lamp drive. And the lamp drives do not control two lamps simultaneously at any given time. This gives the board a total of 60 controlled lamps.
 

====AS-2518-147 Combination Solenoid / Lamp Driver Board====
[[File:AS-2518-147_rev-b.jpg|300px|left|thumb|Bally AS-2518-147 Combination Solenoid/Lamp Driver Board. This board integrates 5V and display voltage regulation, along with lamp and coil drivers--all onto a single board. The photo is of Revision B of this board.]] 

The AS-2518-147 board was used only in two games: Gold Ball and Grand Slam. The reason for its development is assumed to be twofold. First, Bally was looking to cut costs, and this board would have done the job. Secondly, the board may have been used as a test transition between the now very old -35 boardset architecture and the next boardset (6803). The AS-2581-147 had a total of 11 solenoid drives. Likewise, there were what appeared to be less lamp drives (30). But, like the AS-2518-107 board, this board multiplexed the lamps. Again, two lamps can be controlled per lamp drive, but none of the lamp drives control two lamps simultaneously at any given time.
 

===Vidiot Board===
[[File:BLY_Vidiot.JPG|200px|thumb|left|Bally AS-2518-121 Vidiot Board (Note that some chips have been pulled from their sockets on this board)]]
[[file:bally-vidiot-deluxe-board.jpg|200px|thumb|right|Bally Vidiot Deluxe Board (Note that this board has been refurbished)]]
Bally created two Hybrid video/pinball games, [[Granny and the Gators]] and [[Baby Pac-Man]], which included a video game monitor and a pinball playfield. The Vidiot board is a special circuit board used to operate the video game portion and sounds of the hybrid games. However, each game used a slightly different Vidiot board. Baby Pacman used a "Vidiot Board", while Granny and the Gators used a "Vidot Deluxe Board". The two boards are not interchangeable.
 

===Miscellaneous Boards===
====Solenoid Expander Board (AS-2518-66)====
[[file:Solenoid_Expander.jpg|thumb|left|alt=alternative text|Bally Solenoid Expander board- Arrow indicates necessary bulb]] 
The Solenoid Expander board was used in several Bally games. Its purpose is to enable a particular coil or to multiplex several coils. It is typically driven by a lamp SCR on the lamp driver board versus a solenoid transistor on the solenoid driver board. However, at least Centaur and Centaur II are exceptions. Both games drive the solenoid expander board via the Q11 transistor on the solenoid driver board. 

There is a 555 bulb near (or sometimes not so near) that lights when the solenoid expander is activated. This bulb is essential for proper operation of the expander as the main opto isolator chip (MOC3011) on the expander board needs a load to work. Neither Centaur nor Centaur II use this bulb.
 

====Auxiliary Driver - GI Flasher (AS-2518-68)====
[[FILE:BallyA-2518-68.jpg|thumb|left|Placeholder for Bally Auxiliary Driver Board]] 
The auxiliary driver board is used on some Bally games to drive a triac, which in turn switches some of the general illumination on and off for effect. It is typically driven by a lamp SCR on the lamp driver board. The driven triac is typically located on a bracket which is attached to the rectifier board mounting plate in the bottom of the cabinet. 

Much like the solenoid expander board, there is a 555 bulb near the auxiliary driver board that lights when the auxiliary driver board is activated. This bulb is essential for proper operation of the auxiliary driver, as the opto isolator chip (MOC3011) on the board needs a load to work.
 

====Bally Strobe Board====
The Bally strobe board was used on Flash Gordon. A small transformer in the cabinet bottom provides the voltage required for this board. That power is fused by an "in-line" fuse at the small transformer.

There isn't much to go wrong with this board as it's comprised of a few diodes and resistors. Other than replacing the actual strobe lamp and the "trigger" transformer, parts are easy to find. Some folks have been successful using a strobe lamp acquired from Radio Shack. A source for the trigger transformer is unknown.

The trigger transformer should measure about 32 ohms between the pins marked 1 and 2, and about .2 ohms between the pins marked 3 and 4.

If your strobe is producing a very weak strobe, or not working at all, test the two 22uf/250V electrolytic capacitors. Simply replacing out of spec capacitors may bring the strobe back to life.

Another area for concern, as with all single sided PCBs is the header pins. Replacing these pins or simply reflowing the solder on them is a good idea as they are subject to cracked solder joints.

If working properly, the strobe will fire 4 times at game power up. It also strobes along with the controlled lamps during "all lamp" test. It obviously will strobe during game play too.
 

<center>
<gallery widths=200px heights=200px perrow=4 caption="Flash Gordon Strobe Board Components">
File:FlashGordonStrobeBoardFront.jpg|<center>Bally Strobe Lamp Board as found on Flash Gordon (front), with new 22uf capacitors.</center>
File:FlashGordonStrobeBoardRear.jpg|<center>Bally Strobe Lamp Board as found on Flash Gordon (rear).</center>
File:FlashGordonStrobe.jpg|<center>The "HAL-9000 like eye" strobe lamp as seen from the front of the lamp insert panel.</center>
File:FlashGordonSmallTransformer.jpg|<center>Small transformer and in-line fuse in cabinet bottom.</center>
</gallery>
</center>
 

====Stern IM-100 Flash Lamp Board ====

As part of Iron Maiden (1982) Stern utilized a prominent flasher lamp on the backbox lamp board, controlled by a unique aux lamp driver board part number IM-100.

However, Stern did not document the use of this strobe lamp as part of the game manual or schematics.

===Displays===
Here are some different types of Bally displays
<center>
<gallery widths=300px heights=200px perrow=3 caption="Bally 6 and 7 digit displays">
File:B-disp6-21.jpg|<center>AS-2518-21 6-Digit Display</center>
File:B-disp6-15.jpg|<center>AS-2518-15 6-Digit Display</center>
File:B-disp7-58.jpg|<center>AS-2518-58 7-Digit Display</center>
</gallery>
</center>
 

Here are some different Stern displays. Note that the DA-300 circuit board is deeper than any of the other display types.
<center>
<gallery widths=300px heights=200px perrow=3 caption="Stern 4, 6, and 7 digit displays">
File:Stern4display.JPG|<center>4-Digit Display</center>
File:Stern DA-100 6 Digit Display Dbl Sided.JPG|<center>DA-100 6-Digit Display (Double-Sided)</center>
File:Stern DA-100 6 Digit Display RevB.JPG|<center>DA-100 (Rev B) 6-Digit Display (Single-Sided)</center>
File:Stern DA-100 6 Digit Display Sng Sided.JPG|<center>DA-100 6-Digit Display (Single-Sided)</center>
File:B-disps2.jpg|<center>Different DA-100 6-Digit Display (Single-Sided)</center>
File:placeholder.jpg|<center>DA-300 (Rev A) 7-Digit Display</center>
File:Stern-display-da300-revb.jpg|<center>DA-300 (Rev B) 7-Digit Display</center>
File:S-disp7-300.jpg|<center>DA-300 (Rev C) 7-Digit Display</center>
</gallery>
</center>
 

====Bally 6-Digit Displays====
[[File:B-disp6.jpg|200px|left|thumb|A healthy Bally 6-Digit Display]] 
The following information is focused on the AS-2518-21 display. Since the AS-2518-15 display is interchangeable with the "-21" display, everything mentioned here will apply to both displays. 7-digit displays behave the same too, so this information will be helpful for those too. The only real difference is an additional digit enable signal, and some more electronics on the board to drive the 7th digit. 

If you could care less displays work, but are looking for information on how to repair them, then jump to the [http://pinwiki.com/wiki/index.php?title=Bally/Stern#Repairing_Bally.2FStern_Displays Repairing Bally Displays] article below. We'll also show you some ideas on how to keep your displays working properly.
 

[[File:B-disp15.jpg|200px|left|thumb|Example of a Bally AS-2518-15 6-digit display]]
[[File:B-disp21.jpg|200px|right|thumb|Example of a Bally AS-2518-21 6-digit display]] 
The two displays are a little different in the way the components are laid out. Regardless of the differences in appearance, they both perform the same function and are interchangeable with each other. The original display (at least the one mentioned in the Power Play Owner's Manual) is the "-21". The two shown here were upgraded with 1/2 watt 100K ohm resistors. A modification that should be done on all displays.
 

[[File:B-disps1.jpg|200px|left|thumb|Example of a Stern 6-digit display]]
[[File:B-disps2.jpg|200px|right|thumb|Example of a Stern 6-digit display]] 
Likewise, there are different versions of Stern 6-digit displays. These displays are interchangeable with all Bally and Stern games.
 

=====How the displays work=====
The way the display circuitry works is really quite interesting. Although the human eye can not detect it, at any given moment, each display is only showing one digit at a time. The program that runs on the machine's computer is changing the digits so fast that it is not visible. If you were to film the displays and play the film back in slow motion, you'd see all the displays showing the same digit, and it cycles through all six, from left to right. It just cycles so fast that your brain thinks the whole display is lit all the time. 

Each display has six digits, and upon closer inspection, each digit consists of seven segments. This is important stuff to know in order to understand how these displays work, and most important, how to fix them cheaply! 

There are 4 main "parts" of a display assembly:
*The glass display itself
*The display driver consisting of the input decoder
*The six digit driver circuits
*The seven segment driver circuits

There is one digit driver circuit for each of the six digits, and one segment driver circuit for each segment of a digit. How the actual glass display does what it does in order to light various digits and segments is beyond the scope of this tutorial. The decoder takes a number from 0 - 9 as input and determines which segments need to be energized in order to represent this number. The digit drivers are responsible for applying the proper voltages to the proper pins of the display to tell it which digit to light. The segment drivers are responsible for applying the proper voltage to the proper pins of the display to tell it which segments of the digit to light. It is the MPU's job to supply the proper signals to the display driver to make it do all this stuff. 

The decoder is a small integrated circuit (MC14543LE) called a "BCD To Seven Segment Decoder". This decoder happens to be a "latching" decoder, which means it latches onto its inputs and keeps them, even if they are no longer applied, until the decoder is told to release them (blanked). The decoder also has an input called a strobe. When strobed, the decoder will read it's four inputs and latch on to them. A strobe signal is usually a quick off/on/off pulse. There is also an input for the blanking signal. 

[[File:Dispchart.jpg|300px|left|thumb|Labeled Segments and Truth Table]] 
BCD stands for Binary Coded Decimal and is a fancy term for storing a number from 0 - 9 in a half byte of storage (four bits). Using BDC encoding, each byte of memory can store two digits. The input of the decoder is a BCD number from 0 - 9, and the output of the decoder is seven signals. These seven signals are either on or off, and relate to the seven segments of a digit. Each of the seven output signals go to a MPS-A42 transistor, which is part of a circuit called a segment driver. This transistor acts like a switch to turn the segments on or off. The outputs of the seven segment drivers go to the seven segment pins of the display glass. This is how the computer tells the display driver which segments to light. The MPU has a four-signal data path that goes to all five displays (or seven for Six Million Dollar Man). These four signals provide the 4-bit input into the decoder, and remember, all four signals go to ALL of the displays. Please see the diagram of how the segments are labeled, and a truth table showing the 15 possible inputs and outputs to the decoder. For those of you that don't know about binary arithmetic, you can get 15 possible combinations of on/off with 4 digits. (e.g., "0000", "0001", "0010", ..., "0111", "1111"). This is also how you count in binary, or base-2. Remember that the display driver is only interested in 10 of the 15 possible combinations, the ones that represent the numbers 0 - 9, or "0000" - "1001". Any other input combinations will result in unpredictable outputs from the decoder, so we label these as "don't cares", since we know they will never happen under normal circumstances.
 

The digit driver circuit consists of an MPS-A42 transistor and a 2N5401 transistor connected in a circuit that acts as a switch. Normally with no input signal applied, the switch is off, keeping the high voltage supplied by the HV Regulator away from the display. There are 6 digit signals provided by the MPU, one for each digit. The MPU will enable one signal at a time, telling the display driver which digit to operate. This signal will then turn on the "switch" for the digit, allowing the high voltage a connection to the proper pins of the glass display to energize the desired digit. These signals from the MPU are simply 6 wires and the MPU will activate one of them at a time. Like the segment signals, the six digit signals go to all of the displays in a daisy chain fashion. 

Before explaining how the computer makes all this work, let's summarize:
A display driver has four inputs from the MPU. The first is a collection of six signals used to tell the display driver which digit to energize (six digits in the display, six digit signals). Only one of these signals are on at a time. The second input is a collection of four signals that tell the display driver which number to display, in the form of segments. These four signals provide a binary pattern that is interpreted as a binary number from 0 to 9. The third input is a strobe signal, which tells the decoder to read it's inputs, and the fourth signal is a blanking signal, which tells the decoder to turn off all it's outputs. Also, but not mentioned above, are various voltages from the power supply and high-voltage regulator. Each display driver is supplied with +5VDC from the 5-volt regulator on the solenoid driver board. This is used to drive the logic circuits of the decoder. There is also +190VDC<nowiki>*</nowiki> applied to the display driver from the high-voltage regulator on the solenoid board. Finally there is a connection to ground, which brings all the voltages to the proper reference point. 

<nowiki>*</nowiki>For brand new displays, this voltage should be at +190VDC in order to "burn in" the display. Once a display has become used, this voltage may be backed down to +170VDC, which will work just fine and will help prolong the life of the display.
 

=====How The Computer Controls The Display=====
The next thing to understand is how the computer in the pinball machine operates the displays. For this section, referenced MPU board will be the AS-2518-17 module, but all this also holds true for the "-35" MPU module as well. And again, the Bally AS-2518-21 and AS-2518-15 Display Drivers will be referenced. The Stern style display drivers operate the same, and the six digit Stern drivers are 100% swappable with the Bally displays. There are a few minor differences between the seven digit varieties of displays preventing a direct swap without modifications. 

[[File:B-dispdiag.jpg|300px|left|thumb|Display Signals from MPU Board Illustrated]]
 
As mentioned above, there are four sets of signal lines that go from the MPU module to the display driver modules. The first set is the BCD data set which carry the display segment BCD data to all the displays on 4 wires. They leave the MPU module (A4) at connector J1, pins 25-28 and visit every display driver module at connector J1 and pins 16-19 (D4 - D0). The next set of signals is the digit enable signals. These 6 wires carry signals to all the display driver modules with information telling it which digit to light. The third set of signals are 5 latch strobe signals. There is one separate signal for each display driver, and it is the signal that tells the driver's decoder to read the decoder inputs, and output the proper segment signals. The final signal is a single single that goes to all the display drivers called Display Blanking. The signal tells the display driver's decoder to turn off all segment outputs, thereby blanking out the display, or turning all segments off.
 
[[File:BallySternDisplayInterruptCircuit.jpg|300px|right|thumb|Bally and Stern Display Interrupt Circuitry. The 555 timer is configured as a pulse generator.]] 
Once the machine has been turned on and has booted up, the processor on the MPU module is continuously running a program that is stored in the module's ROM chip(s). This program is responsible for controlling the game by reading all the switches, lighting all the lamps, activating all the solenoids, and controlling the displays. The program keeps a lot of information in RAM and uses this information to keep track of scores, switches, etc. An interrupt is a term for a section of computer program that interrupts the "main" program in order to execute a smaller program, sometimes referred to as a "service routine". We won't get into just how this actually happens, just be aware that the main program of a computer may be interrupted at any given time. And to make things even more complicated, interrupts themselves can be interrupted by higher priority interrupt service routines. There may be several different interrupts that occur in a pinball's computer program, but the one we want to study is the one that controls the displays. Keep in mind what was mentioned above, that at any given instant, only one digit is lit on any display. This is called multiplexing. 

320 times a second, or once every 3-1/4 milliseconds (thousands of a second), the CPU is interrupted to service the displays. In memory, the CPU keeps track of all the information it needs to operate all the displays. This information includes a counter used to indicate which display digit is active, the BCD data for all the displays, etc. Here's what the display service routine actually does: 

*'''Determine which digit was updated last time''' - The MPU looks at the digit counter and adds 1 to this value. If the new value is 7, it is changes to 1, then the new value is stored back into memory. Let's assume the new value is 4, so we're going to update the 4th digit.

*'''Blank out all the displays''' - The CPU raises the signal on the Blanking Line which causes all displays to go blank (the blanking signal tells all the decoders to turn off their segment outputs).

*'''Fetch the BCD data from memory''' - The BCD data for the first display, 4th digit is fetched from memory. 

*'''Send the BCD data to the display driver''' - This BCD data is placed on the BCD data bus and display #1 is strobed. This will cause the display's decoder to latch onto the input signals (store them for future use).

*'''Do it again''' - The previous two steps are repeated for the second, third, fourth, and fifth display.

*'''Enable the digit''' - The MPU then enables the 4th digit and disables the other 5 digits by raising and lowering signals on the Digit Enable lines.

*'''Finally, turn the digit on''' - The MPU lowers the signal on the Blanking Line, which causes the all of the decoders to output their proper segment signals and the 4th digit on each display is displayed.

*'''All done!''' - The interrupt service routine then exits and control returns to the main program

As you can see, the display interrupt service routine only handled 1 digit for all displays. Every time it is invoked, it will process the "next" digit, resetting the counter back to 1 when necessary. The process of updating 1 digit for all displays takes about 500 microseconds, or 1/2 of a millisecond, to complete. Pretty cool, eh? 

So, lets do some math. It takes 1/2 millisecond to update one digit, and since there are 6 digits, it takes 3 milliseconds to display all six digits. Since the interrupt runs 320 times a second, and it takes 6 interrupts to update the entire display, dividing 320 by 6 means that the displays are completely updated just over 54 times every second. That's fast enough to fool your eyes and brain into thinking the display is completely lit all the time. Also, since the interrupt routine takes about 1/2 millisecond to run, and it runs 320 times every second, that means about 160 milliseconds of every second of time is spent updating the displays, which is about 16 percent of the time.
 

===Bally Auxiliary Lamp Driver Boards===
[[File:Bally AS-2518-43 Aux Lamp.JPG|left|thumb|200px|Bally AS-2518-43 Aux. Lamp Driver Board]]
[[File:BLY aux lamp3.JPG|right|thumb|175px|Midway A084-91614-A000 Aux. Lamp Driver Board - same as AS-2518-43)]]

To increase the total of controlled lamps used in a particular game, Bally implemented auxiliary lamp driver boards. These aux. lamp driver boards were either used for effect (chaser or infinity lamps used between backglasses in games such as Xenon or Space Invaders), additional controlled insert lamps, or both (top rollover insert lamps and Queen's Chamber chaser lamps used on Centaur). 

There are essentially only two different boards used in games. The first is an AS-2518-43. This is the smaller footprint board, which has only one output connection. It is capable of driving 12 discrete circuits or a total of 24 lamps (12 sets of 2 lamps).
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
|-
! colspan=21 align='center' | Outputs for AS-2518-43 Aux. Lamp Driver Board
|-
!J2 Header
!1
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!19
!20
|-
| Output
|| <center>Q1</center>
|| <center>Q2</center>
|| <center>Q3</center>
|| <center>KEY</center>
|| <center>Q4</center>
|| <center>Q5</center>
|| <center>Q6</center>
|| <center>GND</center>
|| <center>GND</center>
|| <center>--</center>
|| <center>Q7</center>
|| <center>Q8</center>
|| <center>--</center>
|| <center>--</center>
|| <center>--</center>
|| <center>--</center>
|| <center>Q9</center>
|| <center>Q12</center>
|| <center>Q11</center>
|| <center>Q10</center>
|}

 
[[File:BLY aux lamp2.JPG|left|thumb|300px|Bally AS-2518-52 Aux. Lamp Driver Board]] 
The second board is the AS-2518-52. This board is narrower, yet longer in construction. It is capable of driving 28 discrete circuits or a total of 56 lamps (28 sets of 2 lamps). Either aux. lamp driver board receives the same inputs from the CPU board. Likewise, these signals are identical to the signals sent to the primary lamp driver board. The only differing signal between the primary lamp driver board and either aux. lamp driver board is the lamp strobe. The primary lamp driver board receives lamp strobe 1, while the aux. lamp driver boards receive lamp strobe 2.
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
|-
! colspan=21 align='center' | Outputs for AS-2518-52 Aux. Lamp Driver Board
|-
!J2 Header
!1
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!--
!--
|-
| Output
|| <center>--</center>
|| <center>--</center>
|| <center>KEY</center>
|| <center>Q2</center>
|| <center>Q7</center>
|| <center>Q6</center>
|| <center>Q1</center>
|| <center>Q3</center>
|| <center>Q5</center>
|| <center>Q4</center>
|| <center>Q9</center>
|| <center>Q14</center>
|| <center>Q13</center>
|| <center>Q8</center>
|| <center>Q10</center>
|| <center>--</center>
|| <center>Q12</center>
|| <center>Q11</center>
|| <center>--</center>
|| <center>--</center>
|-
!J3 Header
!1
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!19
!20
|-
| Output
|| <center>--</center>
|| <center>KEY</center>
|| <center>Q16</center>
|| <center>Q21</center>
|| <center>GND</center>
|| <center>GND</center>
|| <center>Q20</center>
|| <center>Q15</center>
|| <center>Q17</center>
|| <center>Q19</center>
|| <center>Q18</center>
|| <center>Q23</center>
|| <center>Q28</center>
|| <center>Q27</center>
|| <center>Q22</center>
|| <center>Q24</center>
|| <center>Q26</center>
|| <center>Q25</center>
|| <center>GND</center>
|| <center>GND</center>
|}
 

[[file:placeholder.jpg|thumb|left|200px|Grand Products 0200-700 auxiliary lamp driver board]]A third auxiliary lamp driver board was produced, but not by Bally. It was specific to the [http://www.ipdb.org/machine.cgi?id=403 301/Bulls Eye conversion kit] produced by Grand Products, Inc. It can sometimes be misidentified as a standard Bally AS-2518-52 aux lamp board because of its similar footprint and layout. However, it does not have any silkscreened text on the top of the board, the .156" pins are keyed differently, and it has an additional row of .100" header pins.
 

===Bally Sound Boards===
====Bally AS-2518-32 Sound Board====

[[File:As-2518-32.jpg| 180px | left |thumb | Bally AS-2518-32 Sound Board with 2 pots]]
[[File:Bally -32 Sound 3-Pot.jpg| 180px | right |thumb | Bally AS-2518-32 Sound Board with 3rd pot at R35]]
 

-32 Sound Board ROMs & Jumper Settings 
{| class="wikitable"
!Game
!U3 ROM
!Jumper Settings
|-
| Lost World ||  E729-18  ||  B 
|-
| Six Million Dollar Man||  E729-18  ||  B 
|-
| Playboy ||  E729-18  ||  B 
|-
| Voltan Escapes Cosmic Doom || ? || ?
|-
| Supersonic ||  E729-18  ||  B 
|}
Source: Bally / Midway 1982 parts catalog.
 

====Bally AS-2518-50 Sound Board====
[[File:As-2518-50.jpg| 180px | left |thumb | Bally AS-2518-50 Sound Board]]
 

-50 Sound Board ROM & Jumper Settings 
{| class="wikitable"
!Game
!U3 ROM
!Jumper Settings
|-
| Star Trek ||  E729-18  ||  B, D 
|-
| Kiss ||  E729-18  ||  B, D 
|-
| Paragon ||  E729-51  ||  B, C 
|-
| Harlem Globetrotters ||  E729-51  ||  B, C 
|-
| Dolly Parton ||  E729-51  ||  B, C 
|}
Source: Bally / Midway 1982 parts catalog.
 

====Bally AS-2518-51 Sound Board====
[[File:As-2518-51.jpg| 180px | left |thumb | Bally AS-2518-51 Sound Board]]

The AS-2518-51 sound board improved over earlier sound boards that only made tones and introduced the ability to produce sound effects.

This sound board has a single sound ROM labeled u4.

There is a single self-test push-button on the board, which has the ability to produce a tone or a series of sounds. However, not all game sound ROMs have the self-test feature available. Some ROMs will make the board beep only once, some ROMs will repeat a test sound, and other ROMs do not respond to the self-test button at all. To complete a successful self-test, a sound ROM with a self-test feature must be used. Note that when a sound ROM without a self-test feature is installed and results in an unresponsive self-test, this does not necessarily indicate a problem with the sound board or sound ROM. 

-51 Sound Board ROMs & Jumper Settings 
Jumper A is used when U3 is a 6802 and U10 (6810) is not installed. 
Jumper B is used when U3 is a 6808 and U10 (6810) is installed. 
Jumper C is used when U4 is 2K in size (9316B or 2716). 
Jumper D is used when U4 is 4K in size (2532 or 4732).

{| class="wikitable"
!Game
!U4 ROM
!ROM Size
!Jumper Settings
!Self-Test
|-
| Nitro Groundshaker || E776-14, E776-15 || 2K || B, C || No
|-
| Future Spa || E781-2, E781-5 (or sub with E781-13) || 2K || B, C || No
|-
| Silverball Mania || E786-8, E786-11 || 2K || B, C || Yes
|-
| Space Invaders || E792-2, E792-7 || 2K || B, C || No
|-
| Rolling Stones || E796-11, E796-19 || 2K || B, C || Yes
|-
| Mystic || E798-2, E798-5 || 2K || B, C || Yes
|-
| Viking || E802-2, E802-7 || 2K || B, C || Yes
|-
| Hot Doggin || E809-2, E809-7 || 2K || B, C || Yes
|-
| Frontier || E819-2, E819-9 || 2K || B, C || Yes
|-
| Skateball || E823-2, E823-14 || 2K || B, C || Yes
|-
| Speakeasy || E877-1 || 2K || B, C || ?
|-
| BMX || E888-02 || 4K || B, D || ?
|-
| Grand Slam || E895-? || 4K || B, D || Yes
|-
| Gold Ball || E896-? || 4K || B, D || Yes
|-

|}
Source for Jumper Information: Bally / Midway 1982 parts catalog.
 

====Sounds Plus Sound Board (AS-2518-56)====
[[File:BallySoundsPlus.jpg|200px|left|thumb| Bally AS-2518-56 Sounds Plus Board]] 
The Sounds Plus board was only used in Xenon and very early Flash Gordons. The Sounds Plus board has a daughter card called the Vocalizer that contains the roms and circuitry needed to generate speech.
 

====Vocalizer Speech Board (AS-2518-57)====
[[File:Bally Vocalizer.JPG|200px|left|thumb|Bally AS-2518-57 Vocalizer Board]]
[[File:BallyVocalizerAndSoundsPlus.jpg|300px|Right|thumb|Bally AS-2518-57 Vocalizer and Sounds Plus Boards Insitu]] 
The Vocalizer board was only used in Xenon and very early Flash Gordons. It is a complimentary board to the AS-2518-56 Sounds Plus board, and contains the numerous roms needed for an extensive speech vocabulary. 
 

====Squawk & Talk Sound Board (AS-2518-61)====
The Squawk & Talk (S&T) sound board was the first to offer sound and speech in one board to Bally games. It is probably the most intuitive sound board Bally offered too. Similar to the Bally MPU boards, the S&T uses an LED flashing system during board initialization. There are at least 4 variations of the board: -61, -61a, -61b and -61d. 

Some variations of this board have a J3 header connection located at the top upper left edge of the board. This connection was never implemented. Likewise, some boards are populated with a 2 x 20 pin .100" header connection located on the left edge of the board. This connection is marked on the schematics for the use of a vocalizer, which was never implemented. 

All of the different variations of this board should work on all games. The exceptions are Centaur and Centaur II. These two games must use the -61b board. The reason for this are the extra input/output connections at J2 (bottom right of board) needed for connection to the Say It Again board and the "FF" jumper which routes analog audio to the SIA board (or not). A standard -61 or -61a has a total of 6 header pins at J2, while the -61b has a total of 10 header pins. 

<center>
<gallery widths=300px heights=200px perrow=2 caption="4 Revisions of the AS-2518-61 Squawk and Talk Sound Board">
File:S&T AS-2518-61.JPG|<center>AS-2518-61 Squawk & Talk Sound Board</center>
File:As-2518-61a.jpg|<center>AS-2518-61a Squawk & Talk Sound Board</center>
File:SquawkAndTalk-61BRevision.jpg|<center>AS-2518-61b Squawk & Talk Sound Board. Note expanded connector at J2 (lower right).</center>
File:AS-2518-61D.jpg|<center>AS-2518-61d Squawk & Talk Sound Board installed in VECTOR.</center>
</gallery>
</center>
 

 

Squawk & Talk Jumper Settings 
[[File:SquawkAndTalkJumperAndTestPointLocations.jpg|200px|left|thumb|Bally Squawk & Talk Jumper Locations. Note that the -61B revision of the board contains a jumper FF located within the stack of resistors below the AD558. Neither the -61 or the -61a revision has this jumper.]] 

The first table below is a list of the Squawk & Talk jumper settings by game as specified in the 1982 Bally / Midway parts catalog. These jumpers reflect the original ROM configuration when the game was released. If you've changed your sound ROMs to 2716s or from 2532s to 2732s, see the second table below. 

*If using a 6808 CPU chip with a 6810 chip, install L, remove K
*If using a 6802 CPU chip, install K, remove L. The 6810 can be removed if using a 6802, but doesn't impede proper operation if left in place
*The 5 EE jumpers must be installed when the AY-3-8912 chip is not present.
*The -61B revision of the board has an FF jumper, located in the stack of resistors below the AD558. This jumper should be OUT when a "Say it again" board is used (ala Centaur). This jumper should be IN when a "Say it again" board is not used or connected. The jumper "short cuts" the path used when a SIA board is connected. If the jumper is OUT and a SIA board is not connected, then there is no path for the analog sound to reach final amplification by the TDA2002 at U8. 

{| class="wikitable"
!Game
!Original Jumper settings as shipped with factory configured ROMs
|-
| Flash Gordon ||  C, D, E, G, Q, S, U, W, Y, AA, H, DD, N, and L or K 
|-
| Eight Ball Deluxe ||  C, D, E, G, Q, S, U, X, Y, AA, H, DD, N, and L or K 
|-
| Fireball II ||  C, D, E, G, Q, S, U, X, Y, AA, H, DD, N, and L or K 
|-
| Embryon ||  C, D, E, G, Q, S, U, X, Y, AA, H, DD, N, EE, and L or K 
|-
| Fathom ||  C, D, E, G, Q, S, U, W, Y, AA, H, DD, N, EE*, and L or K 
|-
| Medusa ||  C, E, G, Q, S, U, W, Y, BB, D, H, DD, N, EE, and L or K 
|-
| Elektra ||  C, E, G, Q, S, U, W, Y, BB, D, H, DD, N, and L or K 
|-
| Centaur ||  C, E, G, Q, S, U, W, Y, BB, D, H, DD, N, EE, FF (if no SIA board), and L or K 
|-
| Rapid Fire ||  C, E, G, Q, S, U, W, Y, AA, H, EE, CC, M 
|-
| Mr. & Mrs. Pac-Man ||  C, D, E, G, Q, S, W, Y, U, AA, H, DD, N, and L or K 
|-
| Spectrum ||  C, D, E, G, Q, S, U, W, Y, BB, H, DD, N, EE, and L or K 
|-
| Vector ||  C, D, E, G, Q, S, U, W, Y, AA, H, DD, N, and L or K 
|}
Source: Bally / Midway 1982 parts catalog. 
''*''Note: Even though the parts catalog states otherwise, Fathom does use the EE jumpers. 
 

Squawk and Talk board jumper settings for various sized ROMs at U2 through U5
{| class="wikitable"
!ROM Size/Location
!     ALL    
!    U2    
!    U3    
!    U4    
!    U5    
|-
|  2716 or 9316 || <center>C, E</center> || <center>D, P</center> || <center>Q, T</center> || <center>U, X</center> || <center>Y, BB</center>
|-
|  2532 or 9332 || <center>C, E</center> || <center>D, G</center> || <center>Q, S</center> || <center>U, W</center> || <center>Y, AA</center>
|-
|  2732 || <center>C, E</center> || <center>F, P</center> || <center>R, T</center> || <center>V, X</center> || <center>Z, BB</center>
|}
 

====Say It Again Board====
[[File:SIA.jpg| 180px | left |thumb | Bally AS-2518-81 Say It Again Sound Board. ''Image courtesy of PinSider Victor Nash.'']]
The "Say It Again" sound board adds reverb to a Squawk & Talk sound and speech board. This board was only used on Centaur and Centaur II.
 

'''Board Theory of Operations'''

The Say It Again board is connected to the audio from Squawk and Talk board.

Jumper FF needs to be cut on the Bally Squawk & Talk board.

Sound from the Bally Squawk & Talk board exits from J2-9 via a shielded wire which is grounded at J2-10. It returns from the Say It Again board via J2-7 via another shielded wire which is grounded at J2-8.

The input on the Say It Again Board is via J2-6 with the shield grounded at J2-5. It is then processed through three op amp stages of a LM3900 at U1, then through a dual channel audio delay SAD4096 at U2.

The dual outputs are combined into one and pass through two more op amps LM3900 U3. The U4 4066 acts as an on / off switch. This board is turned 'off' by grounding J1-3.

There are two adjustments on the Say It Again board: Bias and Regen. The Bias adjustment minimizes distortion. The Regen or Regeneration adjustment sets the number of times the echo will repeat.

A detailed procedure for adjusting the Bias is in the Centaur and Centaur II manuals.

====Cheap Squeak Sound Board====
[[File:Bally Cheap Squeak.JPG|200px|left|thumb|Bally Cheap Squeak Sound Board A080-91603-XXXX or Midway P/N M-051-00114-XXXX]]
The Cheap Squeak was designed as a lesser expensive sound board. It only utilizes a 6803 microprocessor, which allows it to function without 6821 PIAs and external ram memory. This sound board is only capable of simple tones and sounds and no speech. 

The following -35 games use the Cheap Squeak:
*Black Pyramid
*Cybernaut
*Fireball Classic
*Kings Of Steel
*Spy Hunter
*X's & O's
 
Granny and the Gators, a -133 game also uses the Cheap Squeak. Lady Luck, a 6803 based game, also uses this sound board. 

At power up, the Cheap Squeak's LED will flicker briefly, then flash, flash again, then turn on and stay on. Once the LED stays on, it seems to turn itself off for certain sounds, and then turn back on. Likewise, it appears to idle with the LED on, when no sounds are playing. The LED May turn on and off when sounds are playing or idle, but this is not always the case. With some games (Kings of Steel, X's and O's, and Black Pyramid), after the sound board successfully boots, the LED remains on. 

There are differing results when pressing the self test button depending on the sound ROMs. For example, pressing the self test with Black Pyramid ROMs results in a differing tone played every time. While pressing self test with Kings of Steel or X's and O's ROMs, causes the sound board to play the same sound each time. 

'''Board Theory of Operations''' 
The 6803 (U1) microprocessor multiplexes A0-A7 with D0-D7, calling those signals AD0-AD7. The processor fetches information from the sound ROMs (both code to execute and sound clips) by placing address information on AD0-AD7 and strobing the processor's AS (address strobe) signal to the 74LS373 (U2), thereby latching the lower 8 bits of the address bus in the LS373. A8-A15 are used along with jumpers JW1 through JW12, to implement a memory mapped I/O scheme to address the 2 sound ROMs which can be 2532s, 2732s, or 2764s. A14 and A15 control the 74LS10 (a triple 3-input nand gate) to assert device selects to the ROMs. 

Note that the processor does not use the traditional R/W signal as it never "writes" to memory. Besides placing instruction address and data on the address and data busses, the processor reads sound selects via P20-P24 and writes sound data to the DAC via P10-P17. Think of these lines as PA1-PA7 of a 6821 or 6532. 

The 6803 is initialized by the MPU at power up into 6803 mode N. Once initialized and running, the sound ROM code running in the 6803 accepts sound signal commands and merely reads pre-formatted sound "clips" from the sound ROMs and then writes the data to the ZN429 (U6) digital-to-analog converter (DAC) 8 bits at a time. The DAC converts the digital data to an analog level which is presented to the amplifiers for output to the speaker(s). 

The board creates 5VDC on board by regulating 12VDC down to 5VDC. Unregulated 12VDC enters the board at J1-10. It is filtered by C8, C9, and C10. The inductor at L1 smooths the voltage somewhat. D6 (VR332, equivalent to a 1N5402), D7, and D8 drop the voltage by .5 - .7 volts (normal voltage drop across a diode). The 7805 at U9 further regulates the voltage down to 5VDC which can be measured at TP2 (TP3 is ground). 

This 5VDC is used to power the TTL logic ICs. The ZN429 DAC also uses this 5VDC as a voltage reference. To prevent the sound volume from fluctuating over the range of operating temperatures, the reference voltage is held constant by a "voltage divider biasing circuit" comprised of resistors at R22, R23, and R24, and a 2N5305 NPN transistor at Q7. This reference voltage is presented at pin 5 of the DAC. 

'''Test Points''' 
*TP1 should measure about 11VDC.
*TP2 is 5VDC.
*TP3 is ground.
*TP4 is the clock signal, provided externally by the 6803 for the purpose of synchronizing address and data read cycles.
*TP5 is the reset signal, which is also present on pin 6 of the 6803. 

Cheap Squeak ROMs & Jumper Settings 
[[File:CheapSqueak.jpg|180px|left|thumb|Bally Cheap Squeak Sound Board with Jumpers Highlighted]]

{|class="wikitable"
! scope="col" |  General EPROM Configuration 
! scope="col" |  Jumpers Connected 
|-
|  U3 & U4 using 2532s
|  J6, J9, J12
|-
|  U3 & U4 using 2732s
|  J7, J10, J11
|-
|  U3 ONLY using 2764 (works only for Cybernaut and X's & O's) 
|  J2, J4, J7, J11, J10*
|}

*Note: If J10 is already installed, leaving it in should cause no ill effects when only using a single 2764.
 
Sound ROM Configuration and Behavior by Game
{|class="wikitable"
! scope="col" |  Game 
! scope="col" |  EPROM Configuration Tested 
! scope="col" |  Jumpers Connected 
! scope="col" |  LED Boot Behavior 
! scope="col" |  SW1 Tune 
! scope="col" |  Boot Tune 
|-
|  Granny and the Gators 
|    
|    
|    
|    
|    
|-
|  Cybernaut 
|  U3 - 2764, U4 - nu 
|  J2, J4, J7, J11 
|  Flicker, Blink, Blink, On 
|  Space Ship Landing 
|  Ding followed by Decaying Buzz 
|-
|  X's & O's 
|  U3 - 2764, U4 - nu 
|  J2, J4, J7, J11 
|  Flicker, Blink, Blink, On 
|  Single Chime that decays 
|  Single Chime that decays 
|-
|  Spy Hunter 
|  U3 - 2732, U4 - 2732 
|  J7, J10, J11 
|  Flicker, Blink, Blink, On 
|  Cartoon Electrical Short Circuit 
|  Chime followed by Rising Laser 
|-
|  Lady Luck 
|    
|    
|  Flicker, Blink, Blink, On 
|  Explosion 
|   
|-
|  Black Pyramid 
|  U3 - 2732, U4 - 2732 
|  J7, J10, J11 
|  Flicker, Blink, Blink, On 
|  Random Pitched Chime 
|  Ding followed by Decaying Buzz 
|-
|  Kings of Steel 
|  U3 - 2732, U4 - 2732 
|  J7, J10, J11 
|  Flicker, Blink, Blink, On 
|  Bell 
|  Chime followed by Rising Laser 
|-
|  Fireball Classic 
|  U3 - 2732, U4 - 2732 
|  J7, J10, J11 
|  Flicker, Blink, Blink, On (assumed - please verify) 
|  Bell 
|  Chime followed by Rising Laser 
|}

After pressing the test switch (SW1), a sound is played, and then the board reboots itself. 
Note: Combining 2732 images into a single 2764 does not work for Black Pyramid, Fireball Classic, Kings Of Steel, or Spy Hunter.

====Bally Sound Board Pinouts====
NC = not connected, and verified. 
Not all N/U have been verified as NC. Some may actually be NC.
{| class="wikitable"
!Pin Connection
!AS-2518-32
!AS-2518-50
!AS-2518-51
!AS-2518-56 Sounds Plus
!AS-2518-61 Squawk & Talk
!AS-2518-61A Squawk & Talk
!AS-2518-61B Squawk & Talk
!A080-91603-C000 Cheap Squeak
!A080-91864-C000 Sounds Deluxe

|-
|J1-1
|Sol. Address A
|Sol. Address A
|Sol. Address A
|Sol. Address A
|Sound Select
|Sound Select
|Sound Select
|Sound Select
|Sound Select

|-
|J1-2
|Sol. Address B
|Sol. Address B
|Sol. Address B
|Sol. Address B
|Sound Select
|Sound Select
|Sound Select
|Sound Select
|Sound Select

|-
|J1-3
|Sol. Address C
|Sol. Address C
|Sol. Address C
|Sol. Address C
|Sound Select
|Sound Select
|Sound Select
|Sound Select
|Sound Select

|-
|J1-4
|Sol. Address D
|Sol. Address D
|Sol. Address D
|Sol. Address D
|Sound Select
|Sound Select
|Sound Select
|Sound Select
|Sound Select

|-
|J1-5
| +5VDC
| +5VDC
| +5VDC
| +5VDC
|N/U
|NC
|N/U
|N/U
|N/U

|-
|J1-6
|Ground
|Ground
|Ground
|Ground
|Ground
|Ground
|Ground
|Logic Ground
|Logic Ground

|-
|J1-7
|NC
|N/U
|N/U
|N/U
|Gen. Ill. Bus (6VAC)
|Gen. Ill. Bus (6VAC)
|Gen. Ill. Bus (6VAC)
|N/U
|Wired in game, but N/U in schematics, need info

|-
|J1-8
|Sol. Bank Select
|Sol. Bank Select
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt

|-
|J1-9
| +43V
| +43V
|N/U
|N/U
|N/U
|NC
|N/U
|N/U
|N/U

|-
|J1-10
|NC
|N/U
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated

|-
|J1-11
|Key
|Key
|Key
|Key
|Key
|Key
|Key
|Key
|Key

|-
|J1-12
|Sol. Address E
|Sol. Address E
|Sol. Address E
|Sol. Address E
|Sound Select
|Sound Select
|Sound Select
|N/U
|N/U

|-
|J1-13
|N/U
|N/U
|N/U (Spare Address Line)
|N/U (Spare Address Line)
|N/U
|NC
|N/U
|Earth Ground
|Earth Ground in schematics, not wired in game

|-
|J1-14
|Ground
|Ground
|Ground
|N/U (Ground)
|Ground
|Ground
|Ground
|Logic Ground
|Logic Ground in schematics, not wired in game

|-
|J1-15
| +43V Return (Sol. Ground)
| +43V Return (Sol. Ground)
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return

|-
|J1-16
|n/a
|n/a
|n/a
|n/a
|n/a
| +12V Unregulated Return
| +12V Unregulated Return
|n/a
|n/a

|-
|J1-17
|n/a
|n/a
|n/a
|n/a
|n/a
| +12V Unregulated
| +12V Unregulated
|n/a
|n/a

|-
|J1-18
|n/a
|n/a
|n/a
|n/a
|n/a
|N/U
|N/U
|n/a
|n/a

|-
!Pin Connection
!AS-2518-32
!AS-2518-50
!AS-2518-51
!AS-2518-56 Sounds Plus
!AS-2518-61 Squawk & Talk
!AS-2518-61A Squawk & Talk
!AS-2518-61B Squawk & Talk
!A080-91603-C000 Cheap Squeak
!A080-91864-C000 Sounds Deluxe

|-
|J2-1
|Speaker +
|Speaker +
|Speaker -
|Speaker -
|Speaker -
|Speaker -
|Speaker -
|Speaker -
|Speaker -

|-
|J2-2
|Speaker -
|Speaker -
|Speaker +
|Speaker +
|Speaker +
|Speaker +
|Speaker +
|Speaker +
|Speaker +

|-
|J2-3
|n/a
|n/a
|n/a
|n/a
|Key
|Key
|Key
|n/a
|n/a

|-
|J2-4
|n/a
|n/a
|n/a
|n/a
|Remote Volume Return
|Remote Volume Return
|Remote Volume Return
|n/a
|n/a

|-
|J2-5
|n/a
|n/a
|n/a
|n/a
|Speech Volume
|Speech Volume
|Speech Volume
|n/a
|n/a

|-
|J2-6
|n/a
|n/a
|n/a
|n/a
|Sound Volume
|Sound Volume
|Sound Volume
|n/a
|n/a

|-
|J2-7
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Reverb Audio In
|n/a
|n/a

|-
|J2-8
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Shield Ground
|n/a
|n/a

|-
|J2-9
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Audio Out
|n/a
|n/a

|-
|J2-10
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Shield Ground
|n/a
|n/a

|-
!Pin Connection
!AS-2518-32
!AS-2518-50
!AS-2518-51
!AS-2518-56 Sounds Plus
!AS-2518-61 Squawk & Talk
!AS-2518-61A Squawk & Talk
!AS-2518-61B Squawk & Talk
!A080-91603-C000 Cheap Squeak
!A080-91864-C000 Sounds Deluxe

|-
|J3-1
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Ground
|n/a
|n/a

|-
|J3-2
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Data
|n/a
|n/a

|-
|J3-3
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Clock
|n/a
|n/a

|-
|J3-4
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
| +5VDC
|n/a
|n/a

|-
|J3-5
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Key
|n/a
|n/a

|-
|J3-6
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|PB3
|n/a
|n/a

|-
|J3-7
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|PB2
|n/a
|n/a
|}

===Stern Sound Boards===
====Stern SB-100 Sound Board====
[[File:YT.png]] A demonstration of the sounds made by a fully populated SB-100 driven by "Nugent" ROMs can be found [https://youtu.be/iul4a1cGXO8 here].
[[File:Stern SB-100 Sound1.JPG|left|thumb|300px|Stern SB-100 Sound Board - 1st Generation]]
[[File:SternSB-100Schematics.jpg|right|thumb|300px|Stern SB-100 Sound Board - 1st Generation - Schematics]] 
The first generation SB-100 sound board was used on the earliest Stern games with electronic sound. These boards were fully populated, because in addition to electronic sounds, there was a (simulated) chimes option (typically dipswitch setting 23 on M-100 MPU boards). Although they will have higher pitched sounds, the first generation boards are compatible with all Stern games using the M-100 MPU board and electronic sounds. With some [[Bally/Stern#Adjusting_the_Sound_Quality_on_a_Stern_SB-100_board|modifications]], this board can be made to sound like the lower pitched 3rd generation board.
 

[[File:Stern_SB-100_Sound2.JPG|left|thumb|300px|Stern SB-100 Sound Board - 2nd Generation (less populated)]] 
The second generation SB-100 sound board was used on Stern games with electronic sound and no chime sound option (typically dipswitch setting 23 on M-100 MPU boards). Due to the lack of the optional chime sounds option, this board is less populated. Although they will have higher pitched sounds, the second generation boards are compatible with all Stern games using the M-100 MPU board and electronic sounds, which did not use the chime option. With some [[Bally/Stern#Adjusting_the_Sound_Quality_on_a_Stern_SB-100_board|modifications]], this board can be made to sound like the lower pitched third generation board.
 

[[File:Stern SB-100 C-1 Ver 3.JPG|left|thumb|300px|Stern SB-100 Sound Board - 3rd Generation (C-1 - less populated)]]
[[File:SternSB100C1.jpg|right|thumb|300px|Another image of the Stern SB-100 Sound Board - 3rd Generation (C-1 - less populated)]] 
The third generation SB-100 sound board was used on some of the last Stern M-100 games with electronic sound and no chime sound option. Like the second generation board, due to the lack of the optional chime sounds, this board is less populated. The difference with this board and the second generation board is that the component markings and through holes have been removed where components are no longer used. Although they will have lower pitched sounds, the third generation boards are compatible with all Stern games using the M-100 MPU board, which did not use the chime option. This board also shipped in the "standard" green PCB variety. This board is easily identified by the large "C-1" notation. Some test points are located in different positions compared to the first two generations, and TP8 has been deleted.
 

<center>
<gallery widths=300px heights=300px perrow=3 caption="Differences Found Between Different Versions of SB-100 Sound Board">
File:Stern SB-100 Full Pop Reset Line 74107 Front No Pullup.jpg|<center>Front side of 1st gen board in vicinity of 74107</center>
File:Stern SB-100 Full Pop Reset Line 74107 Front Pullup.jpg|<center>Modification found on /RESET line of 1st gen board</center>
File:Stern SB-100 Full Pop Reset Line 74107 Back.jpg|<center>Back side of 1st gen board in vicinity of incoming /RESET line and 74107</center>
File:Stern SB-100 Less Pop Reset Front.jpg|<center>Front side of 2nd gen board in vicinity of 74107. Note the addition of a 47Kohm resistor and 3.3uF 6v tantalum capacitor</center>
File:Stern SB-100 Less Pop Reset Line 74107 Back.jpg|<center>Back side Modification found on /RESET line of 2nd gen board. Unless J1 pin 25 is removed from the board, this will tie the /RESET line to the +5v.</center>
File:Stern SB-100 Early J1 Header Pin25.jpg|<center>Back side of 2nd gen board in vicinity of incoming /RESET line (J1 pin 25)</center>
File:Stern SB-100 C-1 Reset Line 74107 Front.jpg|<center>Front side of 3rd gen (C-1) board in vicinity of 74107. Note that service bulletin 11 has been implemented into the design of the board by this time. R93 (47Kohm 1/4W resistor) and C56 (3.3uF 6v tantalum cap) are not in the earlier boards original design, and are possibly not notated on the schematics.</center>
File:Stern SB-100 C-1 Reset Line 74107 Back.jpg|<center>Back side of 3rd gen board in vicinity of where incoming /RESET line used to be. +5V trace is directly tied to the top of R93.</center>
File:Stern SB-100 C-1 J1 Header Pin25.jpg|<center>Back side of 3rd gen board in vicinity of incoming /RESET line (J1 pin 25). The /RESET line is no longer used on the board.</center>
</gallery>
</center>

====Stern SB-300 Sound Board====
[[File:Stern_SB-300_Sound.JPG|left|thumb|180px|Stern SB-300 Sound Board]]
The Stern SB-300 sound board was used in all games which used the M-200 MPU board. The SB-300 is interfaced to the MPU board via the 34 pin J5 connector located at the top of the board.

Note that the sound board only uses pins 1-32 on its J1 connection. Some ribbon cables used were 2 - 16 pin connections, while others were 2 - 17 pin connections, or a combination of the two.

Make certain that pin 34 of the sound board is not connected to the MPU. Pin 34 on J1 of the sound board and pin 34 on J5 of the MPU board is the /IRQ signal. This signal is never used by the sound board. However, if it is connected to the MPU board from the sound board, it can sometimes cause the MPU to lock up or hang. Either bend pin 34 of J1 on the sound board away from the connector (if it is even connected), or snip the pin off completely.
 

=====Stern VSU-100 Speech Board=====
[[File:Stern_VSU-100.JPG|left|thumb|180px|Stern VSU-100 Speech Board]]
[[File:Stern Speech and Sound.JPG|right|thumb|180px|The Stern sound board and speech boards shown installed in a game]] 
The Stern VSU-100 speech board was used as a complimentary board to the SB-300 sound board. In other words, Stern never designed a sound board which was capable of both sound and speech. The speech synthesis is based on the S14001A speech chip. They are pricey, but still available.
 

===Speakers===
All Bally -35 and -133 games use a speaker, Bally -17 games do not. In some cases, games use more than one speaker. The early games use a very small, xxx ohm, low wattage speaker in the bottom of the cabinet.

[[File:Hot Hand Speaker.jpg|thumb|left|200px|Typical M-100 speaker from a Hot Hand. Note that the volume control is missing from this unit.]]
[[File:Seawitch Speaker.jpg|thumb|right|200px|Typical M-200 speaker from a Seawitch]] 
With the exception of the first four Stern M-100 games, which shipped with a 4-bar chime box, all others use a speaker. And most of them have the speaker mounted on a board, aimed at the coin door. The speaker is a 6-1/2", low wattage speaker, but has an odd impedance of 6.4 ohms.

The Stern M-200 games use a single speaker in the lower cabinet. It is a 6-1/2", 8 ohm, low wattage (some are marked 8W) speaker.
 

===Stern MAA-100 ROM Board===
For the first Stern solid state game, Pinball, a ROM board was initially used. It was also used in Stingray, as Stingray has the same ROM set as Pinball.

This board was mounted to the backbox and a harness connected the board to the MPU board at the top connector J5.

<gallery heights=250 widths=250>
File:Stern Pinball ROM Board.JPG|Stern MAA-100 ROM Board
file:Stern-maa-100-board.jpg|Stern MAA-100 ROM Board installed
file:Stern-stingray-backbox-maa-100-board.jpg|Stern MAA-100 ROM Board installed in Stingray
</gallery> 

===Jumper/ROM Info===
Jumpers are small zero ohm resistors or pieces of bare or insulated wire used to connect various points of an MPU board together to allow the board to utilize varying sizes and types of ROM/EPROM chips. Many of the logic gate chips on the MPU boards are used to steer address signals to the proper pins on the various U1-U6 chip sockets. If you have changed the jumpers and you cannot make the board boot with known good working roms, it is possible you have an addressing problem caused by one of the logic gate support chips. Always double check your jumper work by following the trace or schematic to the next point after the jumper; i.e. do not just measure continuity across the jumper. Go to the next point where the jumper connects and test between those points.

Be careful soldering to the pads, as they can be fragile. It is best to remove all the solder from the pad and insert the jumper fully into the via rather than just solder to the top. Soldering the jumper top and bottom will help with any cracked vias. Solder the jumpers to the top of the board where the jumper silk screening is printed rather than the back so that you can easily spot what type of rom chips the board is jumpered for.

All software for Bally/Stern boards can be reformatted into a 2x2732 configuration. It helps to understand how the original software is formatted to understand how to combine and pad the software to get different formats. Any board jumpered to take 2x2732 has its address ranges of U2 as $1000-$17FF (lower half) $5000-$57FF (upper half). The U6 ranges are $1800-$1FFF (lower half) and $5800-$5FFF (upper half).

If the game was originally 4x2716, U1=$1000-$17FF, U2=$5000-$57FF, U5=$1800-$1FFF, and U6=$5800-$5FFF. Thus, to combine this setup to work on a 2x2732 configuration, you would combine U1+U2 into U2.732 and U5+U6 into U6.732 using either your burner software, or the DOS command '''copy /b u1.716 + u2.716 u2.732'''.

If you need to use 2716 eproms but don't have any, you can use a 2732 eprom in its place by duplicating the data. Either use the DOS command '''copy /b rom.716 + rom.716 rom.732''' or load the data twice into your burner; depending on its software, you might change the buffer address by $800 (so the duplicate data loads after the first segment) or it might ask if you want to append the data to the existing buffer.

==== Bally AS-2518-35 or AS-2518-133 Jumper Info====
The following is a list or various ROM and EPROM combinations that can be used with the Bally -35 or -133 board and the associated jumpers and jumper cuts. The letter "E" has been eliminated on every jumper number after the first to save space. '''9332''' ROMS are the "Black" masked ROMS originally supplied by the factory and can be replaced with 2532 EPROMS without any modification to the original board, provided that board has not been altered.

{| class="wikitable"
|-
! U1 ROM
! U2 ROM
! U6 ROM
! MPU Jumpers in Numeric Order
! Jumper CUTS
|-
| '''9316'''
| '''9316'''
| '''9316'''
| '''E1-4,2-6,7-8,9-11,12-36,13-15,16a-19,31-32,33-34'''
|
|-
| '''2716'''
| '''74S474'''
| '''74S474'''
| '''E1-3,2-6,9-11,12-36,13-15,16a-18,31-32,33-35'''
|
|-
|
| '''2532 or 9332'''
| '''2532 or 9332'''
| '''E4-12, 7-8, 10-11, 13a-14, 16a-34, 29-33, 31-32'''
| '''E13-15'''
|-
|
| '''2532 or 9332'''
| '''2732'''
| '''E4-12,7-8,10-11,13a-14,16a-29,31-32,33-35'''
| '''E13-15'''
|-
|
| '''9316'''
| '''9316'''
| '''E2-6,7-8,9-11,12-36,13-15,16a-19,31-32,33-34'''
|-
| '''9316'''
| '''9316'''
| '''2716'''
| '''E1-4,2-6,7-8,9-11,12-36,13a-19,16a-18,31-32,33-35'''
| '''E13-15'''
|-
|
| '''2716'''
| '''9316'''
| '''E1-5,2-4,7-8,10-12,11-29,13a-14,16a-19,31-32,33-34'''
| '''E13-15'''
|-
|
| '''2716'''
| '''2716'''
| '''E1-5,2-4,7-8,10-12,11-29,13a-14,16a-18,31-32,33-35'''
| '''E13-15'''
|-
| '''2716'''
| '''2716'''
| '''2716'''
| '''E1-5,2-4,7-8,10-12,11-25,13a-14,16a-18,31-32,33-35'''
| '''E13-15'''
|-
| '''2716'''
| '''2716'''
| '''9316'''
| '''E1-5,2-4,7-8,10-12,11-25,13a-14,16a-19,31-32,33-34'''
| '''E13-15'''
|-
| '''2716'''
| '''2716'''
| '''2532 or 9332'''
| '''E1-5,2-4,7-8,10-12,11-25,13a-14,16a-34,29-33,31-32'''
| '''E13-15'''
|-
|
| '''2732'''
| '''2716'''
| '''E4-13a, 7-8, 10-11, 12-GND, 16a-18, 31-32, 33-35'''
| '''E13-15'''
|-
|
| '''2732'''
| '''2732'''
| '''E4-13a, 7-8, 10-11, 12-GND, 16a-29, 31-32, 33-35'''
| '''E13-15'''
|-
! '''U1 ROM'''
! '''U2 ROM'''
! '''U6 ROM'''
! '''MPU Jumpers in Numeric Order'''
! '''Jumper CUTS'''
|}

The -133 board was used in 3 games: Baby Pacman, Granny and the Gators, and Grand Slam. If you want to use a -133 board in a game that uses another board, you must change CR52 (a 1n4148 diode near J4) to a 2k resistor. If you want to use a -35 board in a game that requires a -133, change resistor R113 to a 1n4148 diode, banded end farthest away from J4. IMPORTANT: Before plugging the board in, measure the voltage at the MPU J4-15. If it is 6.3 VAC, this game requires a -133. If it is 43 VDC, the game requires the -35 configuration.

==== Bally AS-2518-17 and Stern MPU-100 Jumper Info====
The following is a list of various ROM and EPROM combinations that can be used with the Bally -17 or STERN MPU-100 board and the associated jumpers and jumper cuts. The letter "E" has been eliminated on every jumper number after the first to save space. '''9316'' ROMS are the "Black" masked ROMS originally supplied by the factory. The "-DASH" between numbers means to jump one point to the other, e.g. E 1-2 means jump E1 to E2. Some jumps are very close to each other, others are much farther away. Some cuts in the traces must also be made on the solder or component side of the MPU board, so read the NOTES section below carefully.

{| class="wikitable"
|-
! U1 ROM
! U2 ROM
! U6 ROM
! MPU Jumpers in Numeric Order
! Jumper CUTS
|-
|
| '''9316'''
| '''9316'''
| '''E1-2, 3-4, 6-7, 8-10'''
| '''Usual Factory Setting'''
|-
|
| '''2716'''
| '''9316'''
| '''E1-2, 3-4, 6-7, 8-10'''
| '''Cut & Jumper See Note A'''
|-
|
| '''2716'''
| '''2716'''
| '''E1-2, 3-4, 6-7, 8-10'''
| '''Cut & Jumper See Note B'''
|-
|
| '''2732'''
| '''NONE'''
| '''E6-7, 8-10'''
| '''Cut & Jumper See Note C'''
|-
|
| '''2732'''
| '''2732'''
| '''E1-2, 3-5, 6-7, 8-10'''
| '''Cut & Jumper See Note D'''
|-
| '''74S474'''
| '''74S474'''
| '''2716 or 9316'''
| '''1-2, 3-4, 8-9 Factory Setting for Freedom or Night Rider ONLY'''
|
|-
| '''2716'''
|
| '''2716'''
| ''' See Note E'''
| '''Freedom/Night Rider ONLY'''
|-
! '''U1 ROM'''
! '''U2 ROM'''
! '''U6 ROM'''
! '''MPU Jumpers in Numeric Order'''
! '''Jumper CUTS'''
|}

=====Notes to above Cut and Jumper Section=====
If a jumper combination is '''NOT''' listed in the chart above, this jumper must be cut or removed! Double check your work and verify that someone else has not modified the board before you begin the process. '''Incorrect''' jumper combinations will prevent the MPU from booting, showing a locked on MPU LED. This is a very common fault.

'''Note A, 2716 in U2, 9316 in U6''' 
In addition to the jumpers listed above, you must also make the following cuts and jumps to use this configuration.

#On the component side of the -17 or MPU-100 board, cut the trace that runs from U2 pin 18 to U3 pin 18. Do this where the trace passes between sockets U2 and U3.
#On the solder side of the -17 board, run a jumper from U2 pin 18, to U17 pin 11. 
#On the solder side of the -17 board, cut the trace going to U2 pin 21. 
#On the solder side of the -17 board, run a jumper from U2 pin 21 to U2 pin 24. 

'''Note B, 2716 in U2, 2716 in U6''' 
In addition to the jumpers listed above, you must also make the following cuts and jumps to use this configuration.

Make sure jumpers E1-2, E3-4, E6-7, and E8-10 are in place.
Note: Trace cuts were completed using a "ball" cutter in a Dremel. The "cut" is marked with a black marker.

'''Reference the left picture.'''

#On the solder side of the -17 board, cut the trace leading to U18 pin 4.
#On the solder side of the -17 board, connect U18 pin 5 to the trace you cut leading to U18 pin 4. It's easiest to run the wire from U18 pin 5 to the via ("trace thru dot") that connects to this trace. 

'''Reference the center picture.'''
<ol start="3">
<li>
On the solder side of the board, cut the trace leading to U2 pin 21.
</li>

<li>
On the solder side of the board, jumper from U2 pin 21 to U2 pin 24.
</li>
</ol>

'''Reference the right picture.'''
<ol start="5">
<li>
On the solder side of the board, cut the trace leading to U6 pin 21.
</li>

<li>
On the solder side of the board, jumper from U6 pin 21 to U6 pin 24.
</li>
</ol>

<center>
<gallery widths=300px heights=300px perrow=3 caption="Note B Cuts and Jumpers">
File:U18Jumper.jpg|<center>Solder Side Trace Reroute at U18 and "through hole" to U2, pin 18</center>
File:U2Jumper.jpg|<center>U2 Cut and Jumper from pin 21 to pin 24</center>
File:U6Jumper.jpg|<center>U6 Cut and Jumper from pin 21 to pin 24</center>
</gallery>
</center>

'''Note C, Single 2732 at U2''' for the early 1977 to 1979 games. 
This modification combines the two original 9316 ROMs at U2 and U6 into a single 2732 EPROM at location U2. This configuration works for the following Bally games. This modification should also work for early Stern games with two original 9316 ROMs at U2 and U6.

*Black Jack
*Bobby Orr Power Play
*Eight Ball
*Evel Knievel
*Mata Hari
*Night Rider

To combine the original 9316 (or 2716) U2 and U6 ROM images into a single 2732 U2 image, use this DOS command:

:COPY /B U2ROM.716 + U6ROM.716 U2COMBO.732

Make sure to use the "/b" switch when copying, as shown above. The command combines the two files into a single binary file.

Add the following cuts and jumpers to the -17 MPU to use this configuration.

'''Reference the left picture.'''

#Verify that jumper E6-E7 is in place. E8-E10 can remain in place or can be removed (i.e. "don't care") as it is only useful when U3 and/or U4 ROMs are used. Remove '''any''' jumpers at E1, E2, E3, E4, or E5. That is, remove all jumpers except E6-E7.

'''Reference the center picture.'''

<ol start="2">
<li>
On the solder side of the -17 board, find U18 pin 4. Cut the trace close to pin 4 as shown below. In the picture below, a blue/black dot marks the cut made with a Dremel "ball cutter" bit.
</li>

<li>
Scrape the solder mask from the trace leading to pin 4.
</li>

<li>
Tack solder one end of a short length of wire (or resistor lead) to the bare trace. Solder the other end to U18 pin 5. This connects U18 pin 5 to U2 pin 18. You may choose an alternate method. Just be sure to connect the trace from the "trace through hole dot" to U18 pin 5.
</li>
</ol>

'''Reference the right picture.'''

<ol start="5">
<li>
On the component side of the board, locate U2 pin 13 (top right hand corner of U2). Slightly higher and to the right is a via "trace through hole" with a trace running straight down. Cut this trace to separate the via from the trace. In the picture below, the blue/black dot marks the location to cut.
</li>

<li>
On the component side, jumper from the via noted in step 5 to pad E4 (red wire in picture below). This connects jumper pad E4 to U2 pin 21.
</li>

<li>
On the component side, notice the large '''GROUND''' trace that runs down the board just to the right of the ROM sockets. To the right of the U2 ROM socket, scrape the solder mask from this large ground trace and add a jumper wire from this trace to pad E3 (orange wire/white tracer in picture below. Note that in this instance, U3 was also removed and the ground pad of U3 is used as a jumper point). This connects U2 pin 20 to ground.
</li>

<li>
Use your multimeter to verify that continuity exists between jumpered points.
</li>
</ol>

<center>
<gallery widths=300px heights=300px perrow=3 caption="Note C Cuts and Jumpers">
File:-17MPUFrontAnnotated.jpg|<center>Component Side Jumper Locations</center>
File:-17BackSideJumperAnnotated.jpg|<center>Solder Side Trace Reroute at U18 and "through hole" to U2, pin 18</center>
File:-17FrontSideJumpers.jpg|<center>Component Side Cut (black dot) and Jumper Detail</center>
</gallery>
</center>

'''Note D, 2732 in both U2 & U6''' 
This is a popular modification to the -17 & MPU-100 board as it maximizes the ROM space available and can accommodate almost every game from this period.

In addition to the jumpers listed above,make the following cuts and jumps to use this configuration.
Make sure jumpers E1-2, E3-5, E6-7, and E8-10 are in place, & NO others are connected. It is a good idea to continuity check each of the necessary jumpers, '''BEFORE''' beginning work.

#On the solder side of the -17 or MPU-100 board, cut the trace that runs to U2 pin 21. 
#On the component side of the board, cut the trace that runs to U2 pin 18. Best place to do this is where the trace passes between sockets U2 and U3. Use a mulitmeter continuity setting to figure out the trace to cut, and mark it with a Sharpie to avoid confusion and cutting of the wrong trace. 
#On the solder side, jump a wire from U2 pin 18 to U2 pin 12. 
#On the solder side, jump a wire from U2 pin 21 to U9 (6800CPU) pin 24. 
#On the solder side of the board, cut the trace that runs to U6 pin 21. 
#On the component side of the board, cut the trace that runs to U6 pin 18. A good place to do this is where the trace passes between sockets U6 and U5. Use your DMM's continuity setting to figure out the trace to cut. 
#On the solder side, add a jumper from U6 pin 18 to U6 pin 12.
#On the solder side, jump a wire from U6 pin 21 to U2 pin 21 (this connects both U2 and U6 pins 21 to U9 pin 24). 
#On the solder side, cut the trace that runs to U17 pin 2. 
#On the solder side, cut the trace that runs to U18 pin 4. 
#On the solder side, add a jumper from U17 pin 2 to U18 pin 4.

<center>
<gallery widths=300px heights=300px perrow=2 caption="Note D Cuts and Jumpers">
File:Bally -17 2732 Convert Front.JPG|<center>Component side cut locations</center>
File:Bally -17 2732 Convert Back.JPG|<center>Solder side cuts and added jumpers</center>
</gallery>
</center>

'''Note E Bally Freedom and Night Rider ONLY''' 
These notes are for the Bally Freedom and Night Rider ROMs

These two games used an unique set of ROMs at U1 and U2. These are 74S474 or 7461
(512 byte) ROMs at U1 and U2, and a 9316 or 2716 (2K byte) at U6. According to Williams tech, they state that a U1 2716 EPROM and a U6 2716 EPROM can be used for these two games.If using a -17 or M-100 MPU with a U1 2716 EPROM and U6 2716 EPROM, there are some cuts and jumps required:

#Cut the trace from U1 pin 18 to U2 pin 18. 
#Cut the trace from U1 pin 21 to pad E7. 
#On the solder side, add a jumper from U1 pin 21 to U1 pin 24. 
#On the solder side, add a jumper from U1 pin 18 to U17 pin 11. 
#On the solder side, add a jumper from U1 pin 22 to U2 pin 22. 

==== Stern MPU-200 Jumper Info====
The following is a list or various ROM and EPROM combinations that can be used with the Stern MPU-200 board and the associated jumpers and jumper cuts. '''9316''' ROMS are the "Black" masked ROMS originally supplied by the factory, used on the first few MPU-200 games. Stern switched almost exclusively to a 4x2716 configuration sometime around Seawitch through the end of their run and various boards have been spotted in the wild that seem factory with 2x2732 configuration. Galaxy has been spotted with an oddball 3x9316 + 1x2716 configuration.

{| class="wikitable"
|-
!  U1 ROM 
!  U2 ROM 
!  U5 ROM 
!  U6 ROM 
!  MPU Jumpers in Numeric Order
!  Jumper CUTS 
|-
| ''' (empty)'''
| ''' 2716'''
| ''' (empty)'''
| ''' 2716'''
| ''' 2-3, 5-7, 13-14, 16-18, 23-25, 32-33, 34-35'''
| ''' All others'''
|-
| ''' 9316'''
| ''' 9316'''
| ''' 9316'''
| ''' 9316'''
| ''' 1-5, 2-6, 8-9, 12-13, 16-18, 19-20, 22-25, 26-28, 29-31, 32-33, 34-35'''
| ''' All others'''
|-
| ''' 9316'''
| ''' 2716'''
| ''' 9316'''
| ''' 9316'''
| ''' 2-3, 5-7, 8-9, 12-13, 16-18, 19-20, 22-25, 26-28, 29-31, 32-33, 34-35 '''
| ''' All others'''
|-
| ''' 9316'''
| ''' 9316'''
| ''' 9316'''
| ''' 2716'''
| ''' 1-5, 2-6, 8-9, 13-14, 16-18, 19-20, 23-25, 26-28, 29-31, 32-33'''
| ''' All others'''
|-
| ''' 2716'''
| ''' 2716'''
| ''' 2716'''
| ''' 2716'''
| ''' 2-3, 5-7, 9-10, 13-14, 16-18, 19-21, 23-25, 27-28, 29-30, 32-33, 34-35 '''
| ''' All others'''
|-
| ''' (empty)'''
| ''' 2732'''
| ''' (empty)'''
| ''' 2732'''
| ''' 1-2, 4-5, 13-15, 16-18, 24-25, 32-33, 34-35'''
| ''' All others'''
|-
! ''' U1 ROM'''
! ''' U2 ROM'''
! ''' U5 ROM'''
! ''' U6 ROM'''
! ''' MPU Jumpers in Numeric Order'''
! ''' Jumper CUTS '''
|}

To combine the 9316 or 2716 ROM images into the proper format 2732 images, use the following MSDOS commands.
*copy /b U1ROM.716 + U2ROM.716 U2Combined.732
*copy /b U5ROM.716 + U6ROM.716 U6Combined.732

Note that jumpers 32-33 and 34-35 control the clock speed of the MPU-200. To use an MPU-200 in a game that normally uses a Bally -17/-35 or a Stern MPU-100 board, you should remove these jumpers as they will cause the software to run faster. This isn't really a problem, but timings of sound events might be affected as well as other unforeseen consequences. If using a MPU-200 board in a Bally -17 or -35 or a Stern MPU-100 game, you should remove the 5101 RAM at U13, as it will not be accessed directly. (Some of the software depends on the values being read with the lower nibble high (1111 or $F) - they will load the byte expecting $1f for instance and if you leave U13 in, it will return either random values or more likely $10). If the chip or socket at U13 is bad, it can be ignored. This however is a waste of resources, as the MPU-200 board is hard to find and cannot be substituted by a -17 or -35 board [http://warpzonearcade.com/?p=415 without some modifications]. 

Additionally, if all 32 dip switches are turned off upon boot with an MPU-200, it will flash seven times and jump into self-test mode. This will toggle alternatively every solenoid, flashing controlled lamps, and test each digit on the score displays. At least one DIP switch must be on to avoid this. This is not a function of the board itself, just the software used. For example, if you put earlier stern software (previous to Meteor) or any Bally software in an MPU-200, it will not enter self-test with all dips off.

* To down-grade the MPU-200 to the older MPU-100, remove jumpers 32-33 and 34-35 (used on all Stern MPU-200 EPROM configurations), and remove the 5101 RAM chip from U13.

* The MPU-200, when jumpered for four 2716 EPROMS (U1,U2,U5,U6), will run Bally games using three 2716 (U1,U2,U6) ERPOMs.

* On a MPU-200 configured for four 2716 EPROMs (U1,U2,U5,U6), to run Bally games using two 2716 (U2,U6) EPROMs, change the MPU-200's jumpers E13-14 to E13-15, and E5-7 to E1-5.
 

====Using a single 2732 at U2 in a -35 MPU for Bally games originally released with a -17 MPU====

Bally games released with a -17 MPU can use a single 2732 at position U2 of a -35 MPU.

This includes the following games:
*Black Jack
*Bobby Orr Power Play
*Bow and Arrow
*Eight Ball
*Evel Knievel
*Freedom
*Mata Hari
*Night Rider

Install the following jumpers. 

E12-Gnd ...connects U2 /CE ~ Pin 18 to Gnd 
E11-E15 and E35-E16A ...connects U2 /OE ~ Pin 20 to /VUA-O2-A12 
E13-E9 ...connects U2 A11 ~ Pin 21 to A11 
E7-E8 ...connects U2 A9 ~ Pin 22 to A9 

Remove any jumper at E13A above U1. 
Other jumpers should be irrelevant. 

The original 2716 ROM images can be be combined using the DOS command:
copy /b U2.716+U6.716 CombinedU2.732

====Bally -35 2764 EPROM Conversion====

These instructions will convert a Bally -35 MPU to use a single 2764 EPROM. Colors in the table will match the wire colors in the example photos.
 

<table border="1" cellspacing="0" cellpadding="1" width="680">
<tr>
<th colspan="3" bgcolor="C0C0C0">Bally -35 MPU - 2764 EPROM Conversion Instructions</th>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>1.</td>
<td>Remove any PROMs or EPROMs from U1, U2, U3, U4, U5 and U6.</td>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>2.</td>
<td>
Bend out pins 1, 2, 27, and 28 on a 28 pin EPROM socket so we can solder wires to the pins and install it in socket U2 on the MPU. Pin 26 of the EPROM is not connected. I usually remove this pin from the socket but you can just bend it out and not connect anything to it.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>3.</td>
<td>
Ensure that there are no jumpers connected to E4, E13, E13a, E11, E9, E12, and E35.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>4.</td>
<td>
Connect jumpers E7 and E8. This connects EPROM A9 to CPU A9.
</td>
</tr>
<tr>
<td align=center width=20>5.</td>
<td width="5" bgcolor="red"></td>
<td>
Connect EPROM socket pins 1, 27 and 28 to +5V. I chose to use pin 24 of U3 as the source for +5V. This wire is RED in my examples.
</td>
</tr>
<tr>
<td align=center width=20>6.</td>
<td width="5" bgcolor="E89DB1"></td>
<td>
Connect EPROM pin 2 (A12) to jumper location E4 (A14). This wire is pink in my examples.
</td>
</tr>
<tr>
<td align=center width=20>7.</td>
<td width="5" bgcolor="black"></td>
<td>
Connect jumper location E12 to ground. I use the large ground trace closest to E12. That will connect EPROM CE to ground. This wire is BLACK in my examples.
</td>
</tr>
<tr>
<td align=center width=20>8.</td>
<td width="5" bgcolor="green"></td>
<td>
Connect jumper positions E9 and E13A. That will connect EPROM A11 to CPU A11. This wire is green in my examples. 
NOTE: There is an error on the Bally schematic which shows jumper position E13 connected in common with E13A. This is an error and E13A will need to be used for this step.
</td>
</tr>
<tr>
<td align=center width=20>9.</td>
<td width="5" bgcolor="yellow"></td>
<td>
Connect jumper position E11 to the side of resistor R14 closest to the EPROM socket. That will connect EPROM OE to the output of the gate at U17A. That is an enable that combines CPU A12, VMA and phase 2 of the clock creating an enable that we can use for our EPROM. We could also use jumper location E35 but R14 is closer and makes for a cleaner installation, in my opinion. This wire is yellow in my examples.
</td>
</tr>
</table>
 
<gallery widths=200px heights=100px perrow=3 caption="Bally -35 2764 EPROM Conversion">
File:PinWiki dash 35 2764 conversion 1.jpg
File:PinWiki dash 35 2764 conversion 2.jpg
File:PinWiki dash 35 2764 conversion 3.jpg
File:PinWiki dash 35 2764 conversion 4.jpg
File:PinWiki dash 35 2764 conversion 5.jpg
</gallery>

====Bally -17 And Stern MPU-100 2764 EPROM Conversion====
These instructions will convert a Bally -17 or Stern MPU-100 MPU to use a single 2764 EPROM. Colors in the table will match the wire colors in the example photos.

<table border="1" cellspacing="0" cellpadding="1" width="680">
<tr>
<th colspan="3" bgcolor="C0C0C0">Bally -17 And Stern MPU-100 - 2764 EPROM Conversion Instructions</th>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>1.</td>
<td>Remove any PROMs or EPROMs from U1, U2, U3, U4, U5 and U6.</td>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>2.</td>
<td>
Bend out pins 1, 2, 20, 23, 27, and 28 on a 28 pin EPROM socket so we can solder wires to the pins and install it in socket U2 on the MPU. Pin 26 of the EPROM is not connected. I usually remove this pin from the socket but you can just bend it out and not connect anything to it.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>3.</td>
<td>
Ensure that there are no jumpers connected to E3, E4, and E8.
</td>
</tr>
<tr>
<td align=center width=20>4.</td>
<td width="5" bgcolor="red"></td>
<td>
Connect EPROM socket pins 1, 27 and 28 to +5V. I chose to use pin 24 of U3 as the source for +5V. This wire is RED in my examples.
</td>
</tr>
<tr>
<td align=center width=20>5.</td>
<td width="5" bgcolor="E89DB1"></td>
<td>
Next we need to connect EPROM A12 (pin 2) to CPU A14 (pin 24 of U9). The problem is that there are no jumper locations on the -17 and MPU-100 that are connected to A14 so we have to connect directly to pin 24 of the Motorola 6800 (U9). One option is to run the wire over the top of the board to the back (solder side) but I wanted to make my conversions look as clean as possible so I use pin 20 of U3 as a through hole to get to the other side of the board. So we connect pin 2 of the EPROM to pin 20 of U3 on the components side of the board then connect pin 20 of U3 to pin 24 of U9 on the solder side of the board. This makes for a clean looking conversion on the components side of the MPU. If you're going to use this method you need to ensure that there are no jumpers connected to E8. This wire is pink in my examples.
</td>
</tr>
<tr>
<td align=center width=20>6.</td>
<td width="5" bgcolor="black"></td>
<td>
Connect EPROM pin 20 (CE) to ground. I like to use the large ground trace closest to the EPROM socket. This wire is black in my examples.
</td>
</tr>
<tr>
<td align=center width=20>7.</td>
<td width="5" bgcolor="yellow"></td>
<td>
Connect jumper E3 to the side of resistor R14 closest to the EPROM socket. That will connect EPROM OE to the output of the gate at U17A. That is an enable that combines CPU A12, VMA and phase 2 of the clock creating an enable that we can use for our EPROM.
</td>
</tr>
<tr>
<td align=center width=20>8.</td>
<td width="5" bgcolor="green"></td>
<td>
Connect EPROM pin 23 to jumper location E4. That will connect EPROM A11 to CPU A11. This wire is green in my examples.
</td>
</tr>
</table>

 
<gallery widths=200px heights=100px perrow=3 caption="Bally -17 and Stern MPU-100 2764 EPROM Conversion">
File:PinWiki dash 17 2764 conversion 1.jpg
File:PinWiki dash 17 2764 conversion 2.jpg
File:PinWiki dash 17 2764 conversion 3.jpg
File:PinWiki dash 17 2764 conversion 4.jpg
File:PinWiki dash 17 2764 conversion 5.jpg
File:PinWiki dash 17 2764 conversion 6.jpg
</gallery>

====Stern MPU-200 2764 EPROM Conversion====

These instructions will convert a Stern MPU-200 to use a single 2764 EPROM. Colors in the table will match the wire colors in the example photos.

NOTE: You may need to first convert your board to use [[#Stern_MPU-200_Jumper_Info|two 2732 EPROM]]s before applying this conversion. If you leave the board configured for another rom setup; you may note the board will not flash the diag LED.

<table border="1" cellspacing="0" cellpadding="1" width="680">
<tr>
<th colspan="3" bgcolor="C0C0C0">Stern MPU-200 - 2764 EPROM Conversion Instructions</th>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>1.</td>
<td>Remove any PROMs or EPROMs from U1, U2, U3, U4, U5 and U6.</td>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>2.</td>
<td>
Bend out pins 1, 27, and 28 on a 28 pin EPROM socket so we can solder wires to the pins and install it in socket '''U2''' on the MPU. Pin 26 of the EPROM is not connected. I usually remove this pin from the socket but you can just bend it out and not connect anything to it.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>3.</td>
<td>
Ensure that there are no jumpers connected to E2, E4, E5, E6, E10, E17, and E18.
</td>
</tr>
<tr>
<td align=center width=20>4.</td>
<td width="5" bgcolor="red"></td>
<td>
Connect EPROM socket pins 1, 27 and 28 to +5V. I chose to use pin 24 of U3 as the source for +5V. This wire is RED in my examples.
</td>
</tr>
<tr>
<td align=center width=20>5.</td>
<td width="5" bgcolor="E89DB1"></td>
<td>
Connect EPROM pin 2 to jumper location E10. This wire is pink in my examples.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>6.</td>
<td>
Connect jumper location E5 to E4.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>7.</td>
<td>
Connect jumper location E17 to E18.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>8.</td>
<td>
Connect jumper location E2 to E6
</td>
</tr>
</table>

 
<gallery widths=200px heights=100px perrow=3 caption="Stern MPU-200 2764 EPROM Conversion">
File:PinWiki MPU 200 2764 conversion 1.jpg
File:PinWiki MPU 200 2764 conversion 2.jpg
File:PinWiki MPU 200 2764 conversion 3.jpg
</gallery>

====Bally/Stern ROM Memory Map====

ROM images based on 2732 EPROMs are available on the net for all Bally and Stern machines so I'll give an example of the ROM memory map using these as the example. This is important to consider when doing single EPROM conversions because you will need to create a custom ROM image from original game code.

<table width=600 border=1 cellspacing="0" cellpadding="1">
<tr><th> ROM image</th><th> Memory Location (Hex)</th><th> Memory Location (Decimal)</th></tr>
<tr><td>U2 First half:</td><td>$1000-$17FF</td><td>(Decimal: 4096-6143)</td></tr>
<tr><td>U2 Second half:</td><td>$5000-$57FF</td><td>(Decimal: 20480-22527)</td></tr>
<tr><td>U6 First half:</td><td>$1800-$1FFF</td><td>(Decimal: 6144-8191)</td></tr>
<tr><td>U6 Second half:</td><td>$5800-$5FFF</td><td>(Decimal: 22528-24575)</td></tr>
</table>

====Creating A 2764 ROM Image From 2732/2532 ROM files====

This is one way to create a 2764 EPROM image.

<table border=1 border=1 cellspacing="0" cellpadding="1">
<tr><td>

<table width=700 border=0>
<tr>
<td width=5% valign=top>1.</td>
<td>Download the game code. Most should be available from [http://www.ipdb.org/ ipdb.org].</td>
</tr>

<tr>
<td valign=top>2.</td>
<td>Download Oliver's Vector home ROM files [http://www.pinball4you.ch/okaegi/p-vec2v05.zip here]. The archive will contain fsp.exe which we will use below to split the ROM images in half.</td>
</tr>

<tr>
<td valign=top>3.</td>
<td>Open a command (DOS) prompt and navigate to the directory where you unzipped the Vector home ROM file downloaded above. You will also want to have your 2732 game code images in this directory. What we are going to do is split the ROM images in half creating 4 new files. Here is the command syntax:

fsp U2_2732_image.bin U2_split
fsp U6_2732_image.bin U6_split

Where U2_2732_image.bin and U6_2732_image.bin are the names of the U2 and U6 ROM images and U2_split and U6_split are the prefixes for the output files.

We should now have files named U2_split-0, U2_split-1, U6_split-0 and U6_split-1.
</td>
</tr>

<tr>
<td valign=top>4.</td>
<td>Now we can issue this command to create our image:

copy /b U2_split-0 + U6_split-0 + U2_split-1 + U6_split-1 2764_ROM_Image.bin

The command above must be entered as one string.

This will create a file called 2764_ROM_Image.bin. Burn that to your EPROM and you're ready to go!
</td>
</tr>

</table>

</td></tr></table>

===Attract Mode Test Points===

====Rectifier Board Test Point Values====
{|class="wikitable"
|+ Bally
! scope="col" | Model
! scope="col" | TP1 (LAMPS)
! scope="col" | TP2 (DISPLAYS)
! scope="col" | TP3 (LOGIC)
! scope="col" | TP4 (GI)
! scope="col" | TP5 (COILS)
|-
|AS-2518-18 || +5.4 +/-.8VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC || 7.3 +/-.9VAC || +43 +/-5.4VDC
|-
|AS-2518-49 || +5.4 +/-.8VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC || 7.3 +/-.9VAC || +43 +/-5.4VDC
|-
|AS-2518-54 || +5.4 +/-.8VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC || 7.3 +/-.9VAC || +43 +/-5.4VDC
|-
|AS-2518-132 || || || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

{|class="wikitable"
|+ Stern
! scope="col" | Model
! scope="col" | TP1 (LAMPS)
! scope="col" | TP2 (DISPLAYS)
! scope="col" | TP3 (LOGIC)
! scope="col" | TP4 (GI)
! scope="col" | TP5 (COILS)
|-
|TA-100 || +5.4VDC || +230VDC || +11.9VDC || 7.3VAC || +43VDC
|}

====MPU Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
|-
|AS-2518-17 || +5 +/-.25VDC || +11.9 +/- 1.40VDC || +21.5 +/- 2.7VDC || GND || +5 +/-.25VDC
|-
|AS-2518-35 || +5 +/-.25VDC || +11.9 +/- 1.40VDC || +21.5 +/- 2.7VDC || GND || +5 +/-.25VDC
|-
|AS-2518-133 || +5 +/-.25VDC || +11.9 +/- 1.40VDC || || GND || +5 +/-.25VDC
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

====Lamp Driver Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
|-
|AS-2518-14 || Lamp Driver || +5 +/-.25VDC || GND || || ||
|-
|AS-2518-23 || Lamp Driver || +5 +/-.25VDC || GND || || ||
|-
|AS-2518-43 || Aux Lamp Driver || +5 +/-.25VDC || GND || || ||
|-
|AS-2518-52 || Aux Lamp Driver || +5 +/-.25VDC || GND || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

====Solenoid Driver/Regulator Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
|-
|AS-2518-16 || Solenoid Driver || +5 +/-.25VDC || +190 +/-5VDC || +5 +/-.25VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC
|-
|AS-2518-22 || Solenoid Driver || +5 +/-.25VDC || +190 +/-5VDC || +5 +/-.25VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC
|-
|AS-2518-107 || Combo Lamp/Solenoid Driver || || || || ||
|-
|AS-2518-147 || Combo Lamp/Solenoid Driver || || || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

====Sound Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
! scope="col" | TP6
! scope="col" | TP7
! scope="col" | TP8
! scope="col" | TP9
! scope="col" | TP10
! scope="col" | TP11
! scope="col" | TP12
! scope="col" | TP13
|-
|AS-2518-32 || Sound || +5 +/-.25VDC || GND || +12.5 +/-1.3VDC || +43 +/-5.4VDC || SOL RET || N/A || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-50 || Sound || +5 +/-.25VDC || GND || +12.5 +/-1.3VDC || +43 +/-5.4VDC || SOL RET || N/A || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-51 || Sound || +11.9 +/- 2.5VDC || +5 +/-.25VDC || GND || 0VDC (No Sound), 2.5+/-.2VDC (Sound) || +2.5 +/-.2VDC || 0VAC (No Sound), .35 +/-.1VAC (Sound) || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-56 || Sound || +11.9 +/- 2.5VDC || +5 +/-.25VDC || GND || 0VDC (No Sound), 2.5VDC (Sound) || +2.5 +/-.2VDC || 0VAC (No Sound), .35 +/-.1VAC (Sound) || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-57 || Vocalizer || GND || +5 +/-.25VDC || Analog Output || Digital Input || Speech Clock || N/A || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-61 || Sound || GND || +5 +/-.25VDC || +11.5VDC || -5VDC || Speech Volume Control Voltage || Sound Volume Control Voltage || AY-3-8912 Output || E || TMS5200 Output || VMA || TMS5200 Clock || Reset ||
|-
|AS-2518-81 || Reverb || GND || || || Audio In || || || || || || || +11.9VDC || +12VDC || +4VDC to +8VDC
|-
|M-051-00114-B045 || Sound || || || || || || || || || || || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3 

{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
! scope="col" | TP6
! scope="col" | TP7
! scope="col" | TP8
! scope="col" | TP9
|-
|SB-100 || Sound || +5VDC || Frequency adjustment for R6 pot || Frequency adjustment for R2 pot || GND || Frequency adjustment for R13 pot || Vdd || +11.6VDC || +6.2VDC || +10VDC
|-
|SB-300 || Sound || Analog GND || +12VDC || +10VDC || +5VDC || Clock input for U18 || GND || N/A || N/A || N/A
|}

====Display Module Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
|-
|AS-2518-15 || Display Module || +5 +/-.25VDC || +190 +/-5VDC || GND
|-
|AS-2518-21 || Display Module || +5 +/-.25VDC || +190 +/-5VDC || GND
|-
|AS-2518-58 || Display Module || +5 +/-.25VDC || +190 +/-5VDC || GND
|-
|AS-2518-121 || Vidiot || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

===Fuse Values===
{|class="wikitable"
|+ Bally
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | F1
! scope="col" | F2
! scope="col" | F3
! scope="col" | F4
! scope="col" | F5
! scope="col" | F6
! scope="col" | F7
|-
|AS-2518-18 || Power Supply || 10A, 32V 3AG || 3/4A, 250V 3AG || 4A, 32V 3AG || 5A, 32V 3AG || 20A, 32V 3AG || 3A, 32V 3AG SB || N/A
|-
|AS-2518-22 || Solenoid Driver || 3/16A, 250V 8AG (can be modified to accept 3AG) || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-49 || Power Supply || 20A, 32V 3AG || 3/4A, 250V 3AG || 4A, 32V 3AG || 5A, 32V 3AG || 20A, 32V 3AG || N/A || N/A
|-
|AS-2518-54 || Power Supply || 20A, 32V 3AG || 3/4A, 250V 3AG || 4A, 32V 3AG || 5A, 32V 3AG || 20A, 32V 3AG || N/A || N/A
|-
|AS-2518-107 || Combo Lamp/Solenoid Driver || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-132 || Power Supply || || || || || || ||
|-
|AS-2518-147&dagger; || HV Lamp/Solenoid Combo || 3/16A, 250V 8AG (can be modified to accept 3AG) || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-151&dagger; || Power Supply || 6A, 250V 3AG || 5A, 250V 3AG || 3/4A, 250V 3AG || 8A, 32V 3AG || 8A, 32V 3AG || 8A, 32V 3AG || 8A, 32V 3AG
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3 except &dagger;Source: [http://ipdb.org/files/1024/Bally_1983_Gold_Ball_Manual.pdf Bally Midway GOLD BALL Manual]

Unless noted as slow blow (SB), all fuses are fast blow.

{|class="wikitable"
|+ Stern
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | F1
! scope="col" | F2
! scope="col" | F3
! scope="col" | F4
! scope="col" | F5
! scope="col" | F6
! scope="col" | F7
|-
|TA-100 || Power Supply || 10A, 32V 3AG || 3/4A, 250V 3AG, SB || 4A, 32V 3AG || 5A or 7A or 7.5A †, 250V 3AG, SB || 20A, 32V 3AG || 3A, 250V 3AG, SB || N/A
|-
|}
Unless noted as slow blow (SB), all fuses are fast blow.

† Games that use a 16B-6 transformer & MPU-200 may take a 5A, 7A, or 7.5A fuse at F4, as specified on each individual game's schematics.

{|class="wikitable"
|+ Stern TA-100 F4 Fuse Values
! scope="col" | Game
! scope="col" | F4 Fuse Value
|-
| Ali || 5A
|-
| Big Game || 7.5A
|-
| Catacomb || 7A
|-
| Cheetah || 7A
|-
| Cue || ?
|-
| Dragonfist || 7A
|-
| Flight 2000 || 7A
|-
| Freefall || 7A
|-
| Galaxy || 5A
|-
| Lightning || 7A
|-
| Meteor || 5A
|-
| Nine Ball || 7A
|-
| Orbitor 1 || 7A
|-
| Quicksilver || 7A
|-
| Seawitch || 7A
|-
| Split Second || 7A
|-
| Star Gazer || 7A
|-
| Viper || 7A
|-
|}

 

Various Bally and Stern games have under playfield fuses as well. A common symptom of a blown playfield fuse is flippers operational, but no other on playfield solenoids work. This is because the flippers draw too much current for the under playfield fuse (which is usually 1 or 2 amp), so they are connected before the fuse is in the circuit. The main solenoid fuse on the rectifier board is used to protect against a shorted flipper coil instead.

Sometimes a large under playfield mechanism will be fused separately. Gottlieb did this often, but it is rarer in Bally/Stern games. Examples of the games with auxiliary fuses under the playfield are Silverball Mania and Eight Ball Deluxe. If you have a solenoid not working it doesn't hurt to check and see if it has a fuse, or if someone decided to add one in the past. The under playfield solenoid fuse is a very small value, as for the most part Bally/Stern games are only able to fire one solenoid at a time. This is a limitation of the hardware design, as the 4-to-16 decoder chip on the solenoid driver board can only decode one of 15 signals to fire an associated solenoid.

Some games do utilize the remaining 4 continuous drivers for a momentary coil. (One example is the ball walker area in Flight 2000 - the 2 kickers are activated by the continuous solenoids, for a momentary period). You should identify which under playfield solenoids if any are used as such in your game and add a fuse to the activation (single, thinner wire) side of the coil to prevent a software glitch from locking on that coil. Simply splice it inline with the single wire and use a 1 amp fast blow fuse to protect the driver circuit and coil in the case of a lockup. It would only be necessary to add the fuse for large loaded coils - relay or high resistance coils like on a flag gate or pop-up post coil relay do not place such a great load on the driving transistor that it is in any danger of burning out.

Weak playfield solenoids can be caused by a weak connection on the under playfield fuse holder. Remove the fuse and check for proper tension on the fuse clips for any tarnishing. It is best to just replace suspect fuse holders with new vs. attempting to clean the originals.
 

===Proprietary Numbers on Chips===
Some Bally IC chips are marked with proprietary Bally part numbers, and no other markings are present. Below is a list of some of the most common chips found on Bally boards, and the more commonly referred to chip.
*620-28 - 6800 CPU chip
*620-29 - 6820 PIA chip
*620-30 - 6810 RAM chip
*620-37 - 14514 / 4514 CMOS 4-Bit Latch / 4-to-16 Line Decoder chip
*620-38 - 14534 / 4543 CMOS BCD-to-Seven-Segment Latch / Decoder / Driver chip
*620-39 - 74L154 4 to 16 decoder chip (can sub with 74HCT154)
*620-125 - 6808 CPU chip
 

===Flippers===
====Identification of Different Flipper Assemblies====
<center>
<gallery widths=225px heights=300px perrow=4 caption="Bally & Stern Flipper Assemblies">
File:BallyStarTrekFlipper.jpg|<center>Early Bally Flipper mechanism from a 1978 Star Trek</center>
File:BallyMedusaFlipper.jpg|<center>Later Bally Flipper mechanism from a 1981 Medusa. Commonly referred to as "linear flippers". Note-Double EOS switch for Upper Zipper Flipper</center>
File:SternDraculaFlipper.jpg|<center>Early Stern Flipper mechanism (Generation 1) from a 1979 Dracula. Note-Double EOS switch for Upper Flipper</center>
File:SternSeawitchFlipper.jpg|<center>Later Stern Flipper mechanism (Generation 2) from a 1981 Star Gazer</center>
</gallery>
</center>
 

===Accessing Bookkeeping and Diagnostic Modes===
<center>
<gallery widths=200px heights=200px perrow=3 caption="Bally and Stern Coin Door Test Buttons">
File:Bally-coin-door-switches.jpg|<center>Bally -17 and -35 Coin Door Test Button (L:Early -17, R:Late -35)</center>
File:Stern-coin-door-switches.jpg|<center>Stern -100 Coin Door Test Button (L:Early, R:Late)</center>
File:Stern M-200 Coin Door.JPG|<center>Stern -200 Coin Door Buttons</center>
</gallery>
</center>
 

 

The game must be working properly for the test button to function at all. The test button is not within the game switch matrix. It merely grounds pin 1 of MPU connector J3, (note that the ground wire for this switch connects to the solenoid driver board at pin J2-7, not the MPU board as one would expect). The switch itself is surprisingly resilient to beer/soda. Most failures of continuity to the MPU circuitry are due to either the connector pin in the female housing, or due to fractured solder joints on the male header.

With the exception of Stern -200 based games, pressing the test button the '''first''' time will enter the lamp test. All cpu controlled lamps will flash on and off including backbox lamps. This test will put the greatest load on the rectifier bridge as well as the connectors, enabling you to see "weak" connections.

Pressing the button for the '''first''' time with a Stern -200 based game will start a "burn in" test (lamps, displays, and solenoids will all be tested at the same time).

The '''second''' press of the test button will bring you into display test. Digits from 0-9 will appear on all displays in sequence, enabling inspection of the display elements. This test will not assist in some problems that can occur in displays concerning digit decoding, nor problems where one display ghosts its information onto another, as all displays are displaying the same information. Some games will "walk" an eight across the displays in a sequence enabling issues with decoders to be determined.

The '''third''' press of the test button will start a solenoid test. For Bally games, only the solenoids installed in that particular game will be tested, with their corresponding number showing on the displays. Most Stern games will test all solenoid driver circuits regardless of if they are utilized in that game or not. For this reason, it is desirable to test a solenoid board with Stern software to be able to test all components of the solenoid drive circuit (especially if you are fixing a board foreign to your game). After all solenoids are tested, Stern games will test the sound board during solenoid test, while Bally games will not.

With Bally -17 games and all Stern games, the '''fourth''' press of the test button will start a switch test. The lowest numbered stuck or closed switch will show in the displays. If there are no stuck switches a zero will show in the match display. NOTE: Multiple closed switches will NOT display anything other than the lowest numbered switch. This can be an issue with various switch matrix diode problems, as the switch displayed as closed may not be the switch with a problem. There is a special test rom available that will show ALL closed switches in a sequence similar to how Williams' machines did so. The special test ROM can be downloaded [https://www.pinwiki.com/wiki/images/0/05/Sco_testrom8.zip here].

With Bally -35 games, the '''fourth''' press of the test button will initiate a sound test. The same sound will be played repeatedly until the test is exited.

The '''fifth''' press of the test button will start switch test with Bally -35 games, and start the audits/settings with all other games. Regardless, subsequent presses will get you into audit/adjustment mode; you will see an 01 in the match display when you are at the first adjustment.

==First Things First (WIP)==
As exciting as it may be to acquire a pinball machine, there are several things which should be done before turning one on, or even plugging it in for that matter. It may have been plugged in where it was purchased, but there may be some hidden issues looming inside the game. Following this systematic approach should be very beneficial.

===Keep Game Unplugged Until Further Notice===
When fixing a game of unknown origin, it is best to initially keep it unplugged. There are several things which should be inspected on game, and these things require the game to be unplugged. While it's unplugged, make certain that the 3-prong is present on the line cord, and is actually connected to the earth ground of the game. Likewise, if the 3-prong plug was ever changed in its life, it's a good idea to remove the cover of the plug, and inspect how the wires are connected to the terminal screws of the replacement plug.

After looking over the line cord plug, inspect the line cord. Make certain that there are no nicks or cuts in the cord, deeming it unsafe. [http://www.pbresource.com/tools.html#Parts Pinball Resource] carries an inexpensive, flat, 3-conductor, 14ft. line cord. Next, move to the inside of the cabinet. Make certain that the line cord is securely soldered to the terminals on the line filter. Equally, make certain the ground of the line cord is fastened to the earth ground of the cabinet.

===Check All of the Fuses===
It is highly recommended to check all of the fuses in the game. This includes the fuses on the rectifier board. However, on some games, there are fuses also located under the playfield (for solenoids), on the cabinet wall (for chime coils), behind the display panel (for displays on early Stern games), and / or on the solenoid driver board (for the displays). As mentioned, not all games have fuses in these locations, but be on the look out for them. The best way to make certain that all of the correct fuses go in the correct places is to first remove all of the fuses. Once they are removed, use an ohmmeter or DMM, and check continuity across all of the fuses. Once the fuse have been checked, start placing them back into their proper locations. By removing all of the fuses, the user is forced to put the correct values in the correct locations. Fuses can be kept in the game, but if checking continuity, one side of the fuse must be removed from the fuse holder to attain an accurate reading.

===Inspect the Circuit Boards===
*Burnt / scorched portions of board
*Battery rot on MPU
*Battery rot on lamp driver board and other boards
*Bulging caps on SDB

===Inspect / Test the Circuit Board Components===
*Quick test on the solenoid transistors

===Inspect the Circuit Board Connections===

*Wires soldered directly to rec. board.
*Connectors destroyed due to battery rot

===Check the Solenoids===
*Physically move plungers in coils
*Check solenoid resistance
*Don't forget hidden coils, such as knocker, chimes, and coin lockout
*Check EOS switches on flippers

===Inspect Harness Wiring===
*Make sure screw is secured for ground braid between head and cabinet
*Make sure cabinet ground braid is connected to ground (gets ripped / torn)
*Look for cuts on coin door wiring
*Look for unsoldered / cut wires "floating around"
*Look for burns / scorching

===Plug It In and Turn It On===
*Plug in minimal amount of boards
*Start w/ input to rec. board
*Plug in 20 pin head harness to rec. board next
*Plug in upper right of SDB next
*Plug in lower left of MPU next
*Plug in upper left of LDB next
*Plug in all others on LDB next
*Plug in upper left of MPU next
*Plug in lower right and all others on SDB
*Listen for locked on coils
*Plug in upper right and lower right of MPU

 

==Problems and Solutions==
===Connectors===
Vibration, heat, poor storing conditions, and in some cases alkali damage all take their toll on the connectors used in a pinball machine. Both the male header pins and crimp connectors within plastic housings, (in rare instances, IDC connectors too), are susceptible to the aforementioned conditions. Likewise, some previous person may have performed work on the game which got the job done, but was not necessarily the proper or most desirable way to do it. 

Since the backbone to a properly and reliably functioning game is the connectors, spend some time inspecting all of the connectors in the game, before turning it on for the first time. If any connectors appear to be suspect, repair or replace the connector involved. The best practice is to replace both the male headers and the crimp connectors, if a specific area has seen some sort of damage from heat, oxidation, or alkali damage. In most every case, the plastic or nylon connector housings can be reused, if the crimp connectors are carefully removed.
 

====The Importance of Keying Plugs====
[[File:Stern J3 Rec Two 10s.JPG|200px|left|thumb|Connector as found on a Stern Rectifier Board J3 Connector]]
[[File:Stern J1 Rec Board Keyless.JPG|200px|left|thumb|Connector as found on a Stern Rectifier Board J1 Connector]]
[[File:Stern J3 Rec Replaced.JPG|200px|right|thumb|Connector repinned, keying plug installed, and proper housing for Stern Rectifier Board J3 Connector]]
In addition to connectors, keying plugs play a large role in a game. Every .100" and .156" header connection has one pin removed. The purpose of this practice is to differentiate between connectors with minimal effort. The compliment housing will have a keying plug installed in the position where the header pin is absent. This was done originally at the factory. However, if a connector was replaced or repinned, a person who previously worked on the machine may not have installed a new keying plug. 

Two examples of connectors without keying plugs can be seen in the pics on the left. This game had its wiring harness removed, so the connectors were not placed in their proper positions, and had to be reinstalled. The problem with the first pic is these two .156" 10-pin housings were being used in lieu of the proper, single .156" 20-pin housing at the J3 connection of the rectifier board. The potential to incorrectly plug these two connectors onto the J3 header is extremely high. Because neither housing had a key installed, plus two housings were used instead of one, there are at least four different ways that this connector could be connected. Incorrectly plugging the connector onto the header may have caused extreme unnecessary damage to several of the circuit boards. 

In the lower pic to the left, the connector which goes onto J1 of the rectifier boards was missing a key too. In addition to possibly being plugged in upside down, this connector just as easily could have been plugged in one pin off. If the connector was installed incorrectly, the results would not have been good. 

Considering the overall cost of a keying plug (around $0.25) it is well worth the small cost and effort it takes to install one. It can potentially save the user from unnecessary and costly repairs to the game. If you simply do not have a keying plug and can't remove the old one from the connector, you can use a square toothpick or a Qtip shaft cut down slightly to make one. It is a hack but it's better than destroying good boards and components.
 

====So, Just What is this Green Slime?====
[[File:YouveBeenGreased.jpg|200px|left|thumb|Typical Blue-Green Slime, sometimes found on Bally/Stern header pins.]] 
Sometimes, a blue-green slime seems to be "bleeding" from a header pin connector. This is most likely the insulation coating breaking down into a slime. The best course of action, for long term reliability, is to repin both the male and female sides of the connector, getting rid of the slime as you go.
 

===Powering up the first time===
Thanks to Bally's decision to modularize their system, there is a technique you can use to save yourself some headaches when you first power up a machine. This method connects one section/board at a time and allows you to test each board thoroughly before moving onto the next so you can isolate any issues to one board. This method concentrates on the -18, -49, and all stern games rectifier boards. The -54 rectifier board on later Bally games would employ a slightly different technique.

Disconnect all connectors from the mpu, lamp, sound (if present) and solenoid driver boards. Disconnect J1 and J3 from the rectifier board. Leave J2 connected. Check all the fuses for proper values on the rectifier board. Power on the game, watching to see if any fuses blow. Use a meter and test each test point on the rectifier board to ensure proper voltage is present (remember some of the voltages are AC). Get the rectifier board working 100%.

Turn the game off and reconnect J3 to the solenoid driver board. Connect J3 to the rectifier board as well. Power on the game and repeat the voltage tests on all the test points on the rectifier and solenoid driver board. Investigate any suspect voltages and correct any faults found. Keep in mind that the displays use both the high voltage and +5 voltage so it might be a good idea to remove the displays from the circuit, also.

RottenDog Solenoid Driver/Voltage Regulator

[[File:RottenDogTL783.jpg|300px|left|thumb|A RottenDog high voltage regulator, a TL783.]] 
The RottenDog solenoid driver board uses a TL783 voltage regulator to create display High voltage which should be about 185VDC. This voltage regulator isn’t designed to work as it has been implemented on this board. If the TL783 fails, and they do quite often with this implementation, the full 240VDC will be sent to your displays. This will cause the displays to develop “zits” and fail prematurely. 

Once the solenoid driver board tests ok, connect J4 to the mpu board. Do not reconnect any other connectors to any other boards at this point. Power on the game; if all is well, you will see the mpu board start its LED flash sequence. This is where the majority of repairs will take place; there's no point in hooking other boards up until you have a solid rectifier, solenoid driver/power regulator, mpu board combination working.

After/if the mpu board is booting, add the rest of the connectors back in. When you add the playfield's connectors back in and power up, listen for any solenoids locking on at power-up. Repair the solenoid circuits before proceeding if any do lock on.

At each step in the chain, be sure to inspect and repair any and all connectors in the circuits. Often the connectors get tarnished and do not conduct well enough for reliable game operation. Do not try to clean or sand any suspect connectors - this is a temporary fix at best and only delays the inevitable task of replacement.

Using this method for powering up the game for the first time ensures that any issues you encounter will be isolated to the last piece you added in. Diagnosing and repairing one board at a time is much simpler than multiples.

===Rectifier Board Issues===

====-18, Stern Rectifier boards====
The rectifier board takes the AC voltage from the transformer and uses bridge rectification to convert those voltages to DC. No filtering is done on the rectifier board (that's the solenoid driver/power supply board's job). Depending on the generation of board, there are varying amounts of discrete diodes or bridge rectifiers that produce the DC voltages needed. Additionally, all of the circuits have a fuse for protection in the event of a short on this board.

Putting a meter on the test points across the top of the board will tell you if you're missing any voltages. Refer to the schematics or the charts above to determine the proper voltages at each test point, and remember that some of the voltage outputs are AC volts. If there are any missing voltages investigate further to determine the cause. The main issues with the rectifier board are cracked header pins, bad bridges, poor fuse clips, and poor connections on through hole vias.

If you do nothing else to your power supply, replace the header pins and the connectors that connect to them. The pins are usually burnt beyond usage as are the connector pins. (Often, operators chopped the harness connectors off and soldered the wires directly to the pins as a "fix".) You can get 10 amp header pins from various suppliers that are more robust than the original 7 amp versions. Often just this change alone will fix many lamp "wavering" problems you see on games with lots of feature lamps.

When you replace the header pins consider prying up the plastic insulator piece slightly that keeps the pins in place so you can solder to the top and bottom of each pin. This technique will cure any problems with vias you have and obviate the need for jumper wires that accomplish the same thing. After soldering you can push the insulator piece back down.

Many times the fuse clips are weak or aren't making good contact with the fuses. If you inspect the fuse clips and they are tarnished at all, replace them. Any fuse rated at 4 amps or more use a high current fuse clip to eliminate issues in the future with that circuit. Lower value fuses can use lower current clips with no problem. Solder the fuse clips bottom and top where appropriate for maximal mechanical strength and conductivity.

It's a good idea to replace the discrete diode bridge for the high voltage score display with 1N4007 diodes mounted slightly off the board (about 1/4") so that air can circulate all around them. Solder the leads top and bottom where appropriate. The power resistors should be replaced also with a slight air gap below them to help with cooling. It is possible to approximately double the size of the power resistors (25 ohm to 47 ohm, 600 ohm to 1.3k ohm) to help with the heat dissipated [http://groups.google.com/group/rec.games.pinball/browse_frm/thread/4f40e7f54348acd6/b428979e9f2597c3?lnk=gst&q=bally+rectifier+resistor+gpe#b428979e9f2597c3 Resistor/temperature discussion] although the final test results were not posted.

If you need to replace any bridges, the original style VJ248 bridge can be replaced on the -18 board with a wire lead 25 or 35 amp bridge rectifier. The notch in the bridge is the positive + output; diagonally opposite this lead is the DC negative -. The other 2 leads are the AC inputs and are interchangeable. You have to bend the leads slightly to get them to fit in the smaller VJ248 solder pads. Mark the top of the board with the positive, negative, and AC leads so you don't solder the bridge off by mistake.

If you decide to use the original style bridge, make sure it's not thicker than the other bridges in any other position. The 3 bridges must lie flat against the heat sink slug for proper cooling. The best way to install a replacement VJ248 of the same thickness is to put the bridge in place, then bolt the slug back onto all 3 bridges. Solder the replacement bridge in place. Reinstall the slug with heat sink compound (available at computer supply stores or Radio Shack) smeared in a single thin layer on each bridge surface, and the slug surfaces. Use the least amount possible to get a good even layer; more is not better.

After replacing any parts, test your work with only the J2 cabinet connector installed. Never over fuse a circuit unless the manual for the game specifies; for instance, games with more than 2 flippers often recommend a larger fuse for the solenoid circuit to handle the additional load multiple flipper coils place on the fuse.

====Bally -54 Rectifier board====
[[File:Bally Rectifier board -54 component side,jpg.jpg|300px|left|thumb|Bally -54 Rectifier Board (Component Side)]]
[[File:Bally Rectifier board -54 solder side.jpg|300px|right|thumb|Bally -54 Rectifier Board (Solder Side)]] 

The weak link of this generation of rectifier board are the CR1-CR4 diodes (originally 1n4004, replace with 1n4007 - not so much for the added power capacity, but for the increased heat dissipation) and CR5-CR8 (6 amp at least 50v diodes). The original bridges are much hardier on this generation of rectifier board. If you do need to replace a bridge, the best way is to install it and bolt it onto the bottom mounting plate, then solder it into place. The bottom mounting plate acts as a heat sink for the bridges. 

BR1 is for the feature lamps on the game, BR2 is for the solenoids. The bridge formed by CR5-CR8 forms the +5 vdc, and the one formed by CR1-CR4 supplies the high voltage for the displays. Mount the discrete diodes slightly off the board for better cooling. While not a large problem on this board, inspect the fuse clips as well to ensure they are not tarnished.
 

===The Single Largest Culprit in MPU death===
[[File:Batery_damaged_bally_-17.jpg|300px|left|thumb|Typical Alkaline Damage to a Bally MPU board]] 
By far the largest reason the MPU board stops working is because of alkaline corrosion from the on-board rechargeable batteries. The original battery used on the board is a 3.6 volt nickel cadmium rechargeable battery; over time, this type of battery leaks corrosion into the traces surrounding it, affecting the 5101 memory, the reset circuit, the 6810 memory, the LED area, and all the traces around it. One of the worst boards had corrosion stretching throughout the entire ground plane of the board.
 

====Get rid of that battery now!====
[[File:nicad_elim_options.jpg|left|300px|thumb|Some Options to Eliminate the Ni-Cad Battery on the board]] 
If a battery is on the board, it is recommended to remove it immediately. There are several different ways to replace the battery; in order of preference: 5101 ram eliminator, memory capacitor, nothing, lithium battery, remote mounted AA battery pack, exact replacement. The different options with pros and cons are listed below.
 

5101 Ram Eliminator
:A 5101 ram eliminator doesn't eliminate the ram per se; it replaces it with a more modern ram that is either flash ram or has an internal battery built into it.
:Advantages: eliminating a static sensitive obsolete part, eliminating any type of battery that could leak, high reliability, very long retention time (10-99 years)
:Disadvantages: relatively high cost, need to remove the 5101 (if not socketed) and replace or add a socket, stressing relatively frail mpu board traces, flash ram type can wear out (although unlikely)

Memory Capacitor
:A small capacitor (5.5 volt 1.5 farad works well) is added to the board in place of the original battery. The charging circuit for the rechargeable battery works just fine in maintaining enough of a voltage to enable the capacitor to act in place of the battery. Experience with memory capacitors is somewhat unpredictable. In some games, a charge lasts only a couple months; in other games, it has been seen to last at least a couple years.
:Advantages: relatively low cost, easy installation, no risk of battery leakage, high reliability
:Disadvantages: large initial charge time, some 5101s draw too much current, must turn machine on every couple of months to top off capacitor

Nothing
:Removing the battery and cleaning the board up, you do have the option to replace the battery with nothing. If you don't care about audits, settings, or high scores, this is a valid option. Some software might not like having random garbage in its memory range, though. If you have a Stern MPU-200 based game, do not leave the battery out as the random garbage will cause problems with Stern's software. However, there have been free play romsets developed for this era game that zero out the memory on every bootup, ensuring no garbage gets into the audits causing game errors. Note that not all free play roms have this option, since there is no battery, there's no way for the game to save high scores, options, etc.
:Advantages: No risk of leakage, ever
:Disadvantages: No high scores save, no audits, garbage in ram can cause issues with some software, unless a specific romset is installed with this usage in mind.

Lithium Battery
:Replacing the original nickel cadmium battery with a lithium battery is possible; however it is imperative that you add a blocking diode to prevent the battery from being charged.
:Advantages: Very long life (10 years on average), cheap, can be mounted far from boards so any leakage would not leak onto boards
:Disadvantages: Must use blocking diode, can leak (unlikely), any leakage difficult to clean up

Remote Mounted AA Battery Pack
:A popular and inexpensive option is to replace the original battery with a small AA pack, with a blocking diode. Like the lithium replacement option, it is essential to have a blocking diode (usually incorporated into the pack) so the mpu doesn't try and charge the AA batteries. If you get lithium AA batteries you can get very long life. This type of battery pack needs to be checked periodically to ensure no leakage is occurring.
:Advantages: Low cost, can be moved far from boards so if batteries so leak they do not leak directly onto boards
:Disadvantages: Periodic maintenance (replacing/checking), can leak

Exact Replacement
:You can replace the NiCad with a NiCad. Not recommended as all of the original pitfalls of the original battery are still present, but it will work. Many people use cordless phone batteries to do this; just make sure the voltage and amp hour rating are similar to the original battery. (3.6 volt 150 milliamp hours)
:Advantages: Low cost, can also be mounted far from boards so any leakage does not leak directly onto boards
:Disadvantages: Can leak, needs periodic maintenance (checking for corrosion)

Note that all of the replacement options that include batteries are subject to the same conditions causing leakage as the original battery was. It is strongly recommended that if you decide to use a solution that uses a battery as its power source to remotely mount the battery so that any future leakage does not drip onto the boards. The bottom of the head is a good choice as is the sidewall in cases where there are no boards mounted there. Corrosion can and does travel through the wiring used to relocate the batteries however, so periodic inspection of the batteries and board are necessary to ensure that no further corrosion is occurring.

====Installation of Various Battery Eliminators====
=====AA Battery pack=====
[[file:Battery-Holder-and-Diode.jpg|thumb|left|300px|4 AA cell battery holder & diode]] 
One inexpensive option is to replace the Ni-Cad rechargeable battery pack with a 4 AA battery pack plus diode using ordinary alkaline batteries. You must install a blocking diode (1N5817 or 1N4004 work fine) to prevent the game from trying to charge the battery and causing damage. Install the diode in the 1st bay with the banded side soldered to the "+" or RED terminal and the non-banded end to the "-" BLACK negative spring. Having a battery backup will save high scores & credits, and some sound settings. The holder can be mounted in a convenient spot in the backbox, and leads soldered to the MPU and a Molex .062 2 terminal pin and socket connected to the battery holder for easy servicing of the MPU. Mouser P/N 12BH348-GR for the 4 AA pack.
 

=====Lithium Battery with Holder=====
[[File:Stern M-200 Lith Bat.JPG|thumb|left|300px|Lithium Battery with Holder Installed on Stern M-200 Board]] 
Adding a 3v lithium button battery is an option. It is recommended to install a lithium battery holder. Adding a holder is beneficial for two reasons. First, heating a lithium battery is dangerous. There is potential for explosion, if the battery is overheated. Secondly, adding a holder makes future replacement of the battery much easier. 

If adding a lithium battery, a blocking diode must be installed to keep the MPU from charging the battery. Although it cannot be seen in the pic to the left, a blocking diode is installed on the component side under the battery holder. The M-200 has 4 through holes located just above the bottom ground trace. These through holes are used to install an alternate block style Ni-Cad battery. The bottom left through hole is for the battery's positive terminal. The upper left through hole is used only to support the battery (the pad does not go to any of the board's circuitry). 

In this example, the banded side of the diode is soldered to the lower left through hole. The non-banded side is soldered to the upper left through hole. Additionally, the positive lead of the lithium battery holder is placed in the same upper left through hole. The negative terminal of the battery holder is soldered into the center larger through hole located along the large ground trace (bottom perimeter of board). 

Once the battery holder is installed, install the battery. A CR2032 lithium battery was used in this case. Once the battery is installed, use a voltmeter to make certain that the battery voltage is getting to the 5101 RAM chips. Place the black lead of the voltmeter on any of the ground traces, and the red lead on pin 22 of U8 and U13. A reading of ~3vdc should be seen.
 

=====Memory Capacitor=====
[[File:Cap_install.jpg|300px|thumb|left|Prepping an MPU Board for Memory Cap Installation]]
[[File:Bally -17 Mem Cap.JPG|300px|thumb|right|Alternate method for installing a memory cap. Negative lead is tack soldered to perimeter ground plane. -17 board shown in pic.]] 
Remove original battery, neutralize and clean any corrosion left behind/inspect parts in area, replace as needed. Drill a small hole to the left of the original batteries' negative terminal. Install the capacitor with the negative lead in the leftmost hole of the negative terminal, soldering it into place. Solder a lead to the positive terminal of the capacitor and bend the leg over to help hold it in place. Solder the other end of the lead to either the positive hole from the original battery, or to the bottom lead of R12. Double check your work in reference to the negative lead of the capacitor. Turn the machine on an let the capacitor charge for around 1/2 - 1 hour. Once the cap is charged, turning the machine on for about 1/2 hour a month will keep it topped up.
 

=====Original style battery or cordless phone battery=====
:Remove original battery, neutralize and clean any corrosion left behind/inspect parts in area, replace as needed. Solder new battery in, or better yet, attach fly leads to battery and remote mount. Installing leads long enough for the battery to rest inside the cabinet versus the backbox is optimal. Sealing the battery inside a Ziploc bag is another good idea. Turn machine on for large initial charge to battery. Note that NiCad batteries will leak, just like the original batteries that were used on the MPU. Lithium batteries will be less prone to leaking.
 

====Repairing Alkaline Damage ====
Should a leaky battery damage your MPU, the first decision to make is this: is the board worth repairing? The extent of the alkaline damage combined with your PCB repair skills, the value you place on your time, and the quality of the result you want to obtain may drive you to replace the board entirely with either an OEM board or one of several aftermarket replacements. Alkaline cleanup, component sourcing and replacement, and socketing troublesome old IC sockets can take 3 to 8 hours.

Should you decide to repair the board, component kits to replace everything in the "corrosion zone" are available from several sources for about $10.

Note: Most alkaline damage repair kits do not include the L1 and L2 inductors which are often damaged. Since these inductors are so small in value, simply replace them with a jumper.

Once you've decided to proceed, to neutralize alkaline, you need an acid. The most common way to accomplish this is to wash the affected area of the board with a mild vinegar solution (50% vinegar to 50% water). Use a toothbrush to scrub the board's affected area and outside the affected area, front and back. After scrubbing, rinse the board with water, then use isopropyl alcohol (the highest percentage you can get - 99% or 91%) in a wave action down the board to displace the water. Let the board air dry, or use a hair dryer without heat to speed the drying process.

After the board is dry, replace any components that were affected by the corrosion damage. The parts will be harder to remove and solder as the combination of corrosion and cleaning makes the solder difficult to heat. Adding new solder before desoldering will help in this process, as will boosting your temperature controlled soldering station up by about 50 degrees. Be careful as the pads are very fragile at this point and can lift easily.

Alternate methods of cleaning the affected areas include bead blasting, and sanding. If the damage is very slight, sanding might work best but you remove all the conformal coating when you do so (that's the green masking material applied to the traces on the board). You have to either replace this coating, or use an alternate material to protect the bare traces from oxidation. Clear nail polish has been used to do this, but isn't a great substitute. You can also tin the affected traces with new solder which will protect the copper. It is also possible to purchase conformal coating but it is toxic and messy to work with. **** Note when sanding your MPU you should wear a mask. The board has glass fibers that are bad for the lungs.

Bead blasting is a technique that uses small glass beads on a sand-blaster type setup to blast away the corrosion. Again, the conformal coating is removed and should be replaced. Some critics of the bead blasting technique indicate that the corrosion actually gets embedded in the board by this method; however, it is an accepted repair practice in electronics repair. Most people do not have the equipment needed to do this.

Regardless of the method used, any bare copper traces should be at minimum tinned with solder. Often after removing the components, you will need to sand the remaining pad to get a good soldering surface. A small fiberglass sanding pen is ideal for this purpose (available at auto parts stores). It allows precise sanding on small surfaces. Sand right before you solder as copper starts to oxidize immediately. Use a can of compressed air to blow any fiberglass particles out of your work area and be careful using the fiberglass pen as the fibers will become embedded in your skin causing irritation. Wear eye protection as well as you really do not want these particles flying into your eyes!

Use a meter to test your work, following point by point as you replace components to ensure you have a clean circuit path. Add jumpers as needed, and solder replaced components top and bottom to ensure good via continuity. Use a high quality socket when you replace the 5101 ram and be very careful around this area, as it is right next to the battery zone and is usually heavily damaged. All of the traces in this area are part of the address and data bus for all the roms, pias, and cpu, so any shorts or damage here will affect the rest of the board.

Finally, remember also that the alkaline will travel both down and up from the original position of the battery. Inspect the lamp driver board (right below the MPU) to ensure it hasn't become corroded also. If the corrosion was really bad, inspect the J4 connector on the MPU too. Corrosion will travel into the wires in this connector. If this has happened, you must cut the wires back far enough so the corrosion is not seen; otherwise it will leach back into your board and continue to spread through the wiring harness. Hopefully, the harness will still have enough slack to make it to the J4 connector. If not, you can extend the wires neatly by soldering and heat-shrinking new wires onto the harness. Having a parts machine to pull this type of wiring from enables you to match closely the wire markings so prevent confusion in the future.

Another thing about the J4 connector is that on most boards the two ground pins only connect from the top of the board. If battery corrosion made it to that connector it is a good idea to add a jumper on the solder side of the board from J4 Pin 18 and 19 to ground that runs along the outside of the board.

<center>
<gallery widths=300px heights=200px perrow=2 caption="Bally/Stern MPU Alkaline Damage Abatement">
File:BallyMPUAlkalineCleanedUpFront.jpg|<center>The front side of a Stern MPU-200 with alkaline damage removed.</center>
File:BallyMPUAlkalineCleanedUpBack.jpg|<center>The back side of a Stern MPU-200 with alkaline damage removed.</center>
File:BallyMPUAlkalineCleanedUpCorner.jpg|<center>An MPU-200, "corrosion zone" cleaned up.</center>
File:Corrosion_Cleaned_MPU.JPG|<center>A Bally -17 MPU, "corrosion zone" cleaned up.</center>
</gallery>
</center>

===== Alkaline Corrosion Area Parts List=====
[[File:CorrosionArea.jpg|200px|thumb|left|Bally/Stern Corrosion Area Parts List|link=https://www.pinwiki.com/wiki/images/f/f5/-17and-35MPUComponentListForPinWiki.pdf]] 
Clicking on the thumbnail at left will open a .pdf file detailing parts used in the alkaline corrosion zone for Bally and Stern MPUs. The original parts "skeleton layout" was done by Ed at [http://www.greatplainselectronics.com Great Plains Electronics].
 

==== Using the Dallas/Maxim DS1811 Reset Generator on Bally and Stern MPUs ====
Like the [[Gottlieb_System_80#Using_a_Reset_Generator_for_the_CPU_Reset_Section| technique]] employed to repair alkaline damage on Gottlieb System 80 MPUs, the Dallis/Maxim DS1811 reset generator may be used on Bally and Stern MPUs also. The DS1811-10 has a typical trip point of 4.35VDC. You may also use the Microchip Technology equivalent, part number [http://www.greatplainselectronics.com/proddetail.asp?prod=MCP130-460DI%2FTO MCP130-460DI/TO], available from Great Plains Electronics.

Unlike Gottlieb System 80 MPUs, using the DS1811 on Bally and Stern boards doesn't save you much work. It replaces only 10 easily sourced components. And since you've done the hard work of cleaning up the alkaline damage already, using the DS1811 isn't really worth the trouble. But, if you'd like to use the DS1811, the procedure is described below.

After you've cleaned up the alkaline damage, replace all components except these 10:
*VR1
*R1, R2, and R3
*R112
*R138, R139, and R140
*Q1 and Q5

With the board oriented as it would be in the game (J5 at top), install a jumper from the top through-hole of where R139 was, to the bottom through-hole of where R138 was.

There are several ways to form the legs of the DS1811 for a Bally or Stern MPU. However, with the flat side of the DS1811 facing left (i.e. at J4), the legs of the DS1811 should be placed in the prior location of Q5 such that:

*Pin 3 of reset generator (top pin) is where the upper, right lead of where Q5 was
*Pin 2 of reset generator (middle pin) is where the lower, right lead of Q5 was
*Pin 1 of reset generator (bottom pin) is where the left lead of Q5 was

Add a 1K, 1/4W resistor from pin 1 of the reset generator to +5VDC. This signal can be picked up conveniently at the banded end of CR5 (a 1N4148 diode).

<center>
<gallery widths=300px heights=200px perrow=2 caption="Using the Dallas/Maxim 1811 Reset Generator">
File:MPU200DallasReset.jpg|An MPU-200 MPU with alkaline damage abated, and reset components replaced with the DS1811 reset generator.
File:MPU200DallasResetAnnotated.jpg|The same image, but with the single jumper indicated (yellow dot), where to install the DS1811 flat side facing left, and the added 1K resistor.
File:Placeholder.jpg|Illustrated picture of components to remove, keep, and jumpers to add.
File:MPU200DallasResetCloseup.jpg|Closeup of the DS1811 equivalent installed.
</gallery>
</center>
 
One could also use The MCP100-460-DI/TO although there are a some variations from the DS-1811.

The following need to be removed (or not replaced)
*VR1
*R1, R2, and R3
*R112
*R138, and R140
*Q1 and Q5
The difference here is that R139 is left intact.

Jumper R2 & R3.

Add a 1N4148 diode. Anode to anode of CR7, cathode (banded end) to "left" hole of R140. The CR7 anode hole is large enough to accommodate both diode leads without trouble.

The MCP100 is added in the Q1 (not Q2) location.

With the flat side of the part facing and the leads pointing down, the leads are from left to right, RESET, V (+5v), and Ground.

*V (+5v) the middle lead, is soldered in the "top" hole, close to the now occupied hole of R140
*RESET in the left most hole
*Ground in the bottom most hole (which clearly goes to ground)

This solution is slightly less messy because it does not require the "floating" 1K resistor.

===MPU boot issues===
Non-booting Bally/Stern MPU boards fall into a couple different categories. If the board's LED is good and turns off at bootup, you're part of the way there. Refer to the flash sequence section to figure out where your issue lies to narrow down the problem area. 

You must have a good set of roms in a game as well as a known good working 6800 cpu chip. Suspect any sockets that have a brown color or closed frame - often the spring tension on these sockets is poor necessitating replacement. Be very careful soldering on the mpu boards as the traces and pads are very fragile. 

A "cheat sheet" comprised of the signals and pinouts for the primary chips and all of the header connections used with a Bally -35 MPU board is available [[Media:Bally_MPU_Board.pdf | here]]. The PDF is specifically for a -35 board, however, Bally -17 and Stern M100 boards are similar. The obvious differences are the ROM jumper settings and connection J5 (J5 on a -35 board has one more pin).

====LED locked on====
Remove all ICs except for U6, U9, U11, and U2 if it is a Stern. Leon's test rom is recommended for tricky MPUs. This allows you to leave out U11 and check most address and data lines.

Short pins 40 and 39 momentarily on the cpu chip; after doing so, see if the LED goes off. If it does, concentrate your efforts on repairing the reset circuit as it's not holding the reset low on powerup for the minimum required 50 milliseconds. If it doesn't, it's best to pull the board from the machine and put it on the bench, using the benchtop power supply details to keep working on the board outside the machine.

Ensure that Q2 and the LED itself are working properly (i.e. the board may be booting but the LED provides no indication). Pin 39 of the 6821 PIA at U11 drives the LED. Probing pin 39 and finding it pulsing indicates that the MPU is booting (or at least partially booting) and that R28 (8.2K), R29 (470), Q2 (2n3904), or the LED itself has failed.

An easy quick test for the reset section is putting your DMM on pin 40 of the cpu. It should read 5v, and in most cases if it does the reset is good. Attach a logic probe to the output of Q5 - on power on, you should see this circuit start low and then go high approximately 50 milliseconds later. If it goes high immediately, at a minimum replace Q5, then Q1. Make sure the 2 watt resistor is not leaning on Q5. The heat can kill the transistor.

Next put the probe on U9 pin 3, 36, and 37 to see if you get pulsing - these are all clock signals and you should see pulsing on all 3 pins. If you have an oscilloscope you can visually see the signals, or even on a multimeter, the voltage will show between 2.5-2.9 volts. If you see zero volts or 5 volts, your clock signal is bad. The CPU could be dragging down the clock. Remove U9 and see if the clock signal is now good. When clock signal is bad suspect U15 or U16. Also check C15 and C14. U15 is failed most often.

Check U9 Pin 2. This is the HALT line. You should see 5v, if not replace U9

Check U9 Pin 5. This is the VMA line. It is a pulsing signal and reads about 2.8v with a DMM. If incorrect first try a new U9. Next check U14D, U15C, U19B. U15 is the most likely IC to have failed.

Still locked on? After double checking all your jumper changes, roms, and rams in another board if possible, time to start suspecting other issues such as bad sockets, traces, or addressing chips. Bad sockets are quite common.

====Reset Circuit====
The purpose of the reset circuit is to ensure the +5 vdc is stable before allowing the system to start. At startup, the reset signal is held low via pull-down resistor R139 until the +12 vdc line rises above the zener diode VR1's value (8.2 or 9.1 volts depending on your board). At this time, the input voltage threshold for the +5 regulator on the solenoid driver board has been met with some headroom. Q1 starts conducting, turning on Q5, which provides the actual reset signal. All of this happens in approximately 50 milliseconds. 

Most of the reset circuit is in the corrosion zone (lower left corner of the mpu board) and consists of most of the components commonly included in "repair kits". If the reset circuit is not working, the LED will not turn off. If Q1 or Q5 fails, conducting all the time, the cpu chip will never come out of reset. 

The reset circuit continuously monitors the +12 volt line; if it falls below VR1's threshold voltage, the game will reset. If a Bally/Stern game is resetting, concentrate on why the +12 volts is dropping below 8.2/9.1 volts. (VR1 sets the threshold at which the reset signal turns on, and also when it would turn off in a rebooting scenario.) 

Note that Q1 and Q5 actually form a switching power regulator for the reset signal only. The normal +5 supplied to the rest of the board is derived entirely from the solenoid driver board's regulator. The reset signal regulated power is used to charge the battery, provide the reset signal, and to power the 5101 chip(s) on the board. Normal +5 vdc is blocked from entering the reset circuit by the 1N4148 diode CR7. Diode CR5 (1N4148) blocks the battery voltage from powering the entire board via CR7. 

====Bally / Stern MPU Board LED Never Lights or is Locked On====
If the LED never lights, either the +12v (TP2, J4 pin 12) is missing or the LED is bad. By default, the LED is ON until the software tells U11 to turn it OFF. 

If the LED lights solid, there's some digging to do. First off, if the board has any corrosion damage at all, it needs to be cleaned and neutralized before attempting any repairs. While shot-gunning components might fix the board, it won't be 100% reliable if the corrosion isn't addressed. 

Make sure you are getting a solid power path from the rectifier board through the solenoid driver / power regulator board to the MPU board. A locked on LED can be caused by a poor connection anywhere in this chain. Sometimes reseating connector J4 on the MPU board (lower left) will 'clean' a connector well enough to make a better connection. While this may be a short term fix, be aware that any connector, which seems to work better after being reseated, really should be repinned and have its header pins replaced. 

Next, put your DMM or a logic probe on pin 40 of the 6800 cpu chip (U9). Power on the board. You should see the voltage remain low / at zero, and then approx 1/10 of a second later, rise to about +5 vdc (high). This is the reset signal, which originates from the components in the lower left corner of the board, and is sent throughout the board to U9, U10, and U11. What the reset section (called the 'valid power detector') does is not allow the MPU to boot until the +12 volts are stable over the value of ZR1 (a zener diode, usually either 8.2 or 9.1 volts). This delay ensures that the +5 voltage is stable enough to run the MPU board reliably (the +5 volts is derived from the +12 volts on the solenoid driver / power regulator board). 

The 6800 CPU chip will not 'unlock' and start program execution until it sees a transition from a low (0 volts) to high (~5 volts) signal. This is the purpose of the power on reset delay. The reset delay and signal must be present at all three of the reset inputs at U9 (pin 40), U10 (pin 34), and U11 (pin 34). If the signal starts out immediately at a high level, the MPU will not start to boot until the transition takes place. If you have a locked on MPU, you can take a screwdriver or your meter probe and short pins 39 and 40 together for a brief moment on U9. If the game starts to boot after doing this, it's a safe assumption that the reset circuit is to blame. Shorting the pins together simulates what the reset circuit does. 

If you need to rebuild the reset circuit, full kits are available from specialty suppliers such as Great Plains Electronics or Big Daddy Enterprises. The kits include all replacement components in the corrosion zone. Bare bones component replacements are Q1 (2n3904 or 2n4401) and Q5 (2n4403 or 2n3906), but it is a good idea to go ahead and replace all the parts that come in the kit. Replace components one at a time to ensure that you do not mix any up. Note there are some components that are polarized in their installation, which include VR1, CR5, Q1, and Q5. Look carefully at the board to see if there are traces on the top and bottom of a component. The continuity at a through hole can be compromised due to alkaline corrosion. Therefore, it is recommended to solder these components from the top and bottom of the board to ensure that a good connection is maintained. 

The following is the list of parts for the reset section that should be replaced. Parts listed with more than one type are equivalent and can be substituted freely. It is also possible that the inductors L1 and L2 need to be replaced as well, however this is very rare. If there is heavy corrosion on them they should be replaced. 

'''Transistors:'''

Q1 - 2N3904/2N4401 (lower left area)

Q2 - 2N3904/2N4401 (near LED)

Q5 - 2N3906/2N4403 (lower left area) 

'''Diodes:'''

VR1 - zener 1N9598/1N4738A

CR44 - 1N4004 rectifier diode

CR5, CR7 - 1N4148 switching diode

CR8 - LED 

'''Capacitors:'''

C1, C2 - 820pF ceramic capacitor

C3 - 0.01uF ceramic capacitor

C5 - 4.7uF tantalum capacitor

C13, C80 - 0.01uF ceramic capacitor 

'''Resistors:''' (1/4 w unless noted)

R1, R3, R24, R28 - 8.2k

R2 - 120k

R11 - 82 ohm/2 watt

R12 - 270 ohm

R16 - 2k

R16 - 2.2k (stern mpu-200 only)

R17 - 150k

R29 - 470 ohm

R107 - 3.3k

R112 - 1k

R134 - 4.7k

R140 - 20k 

If your reset circuit is operating as designed, yet the LED is still locked on, next step is to pull all the chips from the board except for U9, U11, and U6 (leave all chips U1-U6 installed on Stern MPU boards. Only U6 is required on Bally boards to perform the initial LED turn off). It helps to have a known working U6 from a Bally game to use as a test chip for this purpose. Be aware that you need to know/have the board jumpered for the correct type of chip you're inserting. 

See if the board starts and turns off the LED with just the chips above installed - if it does, add these chips back in this order to see which might be bad: U10 PIA, U1-U5 program chips, U7 6810 ram, U8 5101 ram. Often a bad ram/rom can cause the entire system to lock up. Bad chip sockets can be a factor as well; the early Bally -17 boards have a closed type brown socket that's especially prone to failure. 

Double check the jumpers to ensure they match the ROM chips you have available, and change the ROM chips to known working ones for testing. A final thing to check if the machine won't boot is the clock circuit. It is fairly robust, and far more common that the reset circuit itself or chip sockets are the issue. To check the clock circuit you need a logic probe or oscilloscope. A multimeter might show the average voltage on a clock circuit, or it might just show meaningless constantly changing numbers. The clock signal is pin 3 on the CPU chip, and the shifted clock signal goes to pins 36 and 37. The frequency is about 500 kilohertz for Bally -17, -35 and Stern MPU-100 boards, and approximately 850 kilohertz for the Stern MPU-200 board. 

If the clock signal is missing, pull U9 first to make sure the CPU chip isn't damaged, and test it again. 

It can be frustrating to track down a locked on LED problem, but breaking the problem up and testing each section individually helps. Just remember that if the LED turns on and then off, most of the battle is won. The board has booted far enough that the software was able to start and turn off the LED. Proceed onto the LED flash testing to determine what needs to be fixed beyond that. 

====Bally / Stern MPU Board LED Flash Sequence====

Upon start up, Bally and Stern boards have an LED that flashes. The LED is used to convey the results of specific tests conducted on various parts of the system. This section explains what is being tested and how, according to information from the Bally "FO-561-2 Theory of Operation rev. 5-1982" manual, and the Stern manual "Theory of Operation, Stern's Microprocessor Controlled Solid-State Games".

When power is first applied to the MPU board, the LED by default is ON. The very first set of valid instructions in every Bally / Stern game is to turn the LED off. This is more of a flicker than a flash, so is not counted as a flash in the 7 flash sequence.

=====Quick summary=====

Flicker: MPU reset good, program booted. 
1st Flash: ROM Checksums OK 
2nd Flash: U7 6810 ram OK 
3rd Flash: U8 5101 ram OK (U8 & U13 on mpu-200) 
4th Flash: U10 PIA OK (see details for caveats) 
5th Flash: U11 PIA OK (see details for caveats) 
6th Flash: U12 555 Display interrupt timer OK 
7th Flash: Zero crossing interrupt detector OK (solenoid voltage present) 

=====LED flicker=====
The LED flicker tells you the CPU chip was able to start a valid program stored in the EPROMs, and that the reset circuit itself is good. 

=====First flash=====
After the program is running, it performs a checksum of all programmed chips U1-U6. Most Bally games' programming is split between an operating system chip U6 and game ROM chip(s) at U1/U2. Stern games were programmed a little looser: operating system and game code are freely interspersed. 

Bally checksums are calculated by summing each byte, and discarding any carries. Most games check their code in $0400 blocks, so it would be possible to determine down to the chip which chip failed this checksum. (A 2716/9316 chip has hex $0800 space available in it - 2732 sized images are $1000 in size. The smallest chip used was a 474 PROM which has $0200 bytes available) However, to do so would require a way to read the X register from the 6800 CPU chip at the time of checksum failure. So if you do not get the first flash, it is best to replace the U6 chip first, then move onto the other chips - U5, U2, and U1 (if present). 

Stern checksums are calculated similarly, but not in chunks. The entire program space is summed and must equal $00 for the first flash to occur. 

Regardless of whether the manufacturer is Bally or Stern, after the checksum is passed, the first flash occurs. 

=====Second flash=====
Next, the program tests the 6810 RAM chip at U7, by writing the data $00 to each memory location contained in the RAM ($00-$7F). It then reads back each location to ensure that $00 is returned. It increments the data to $01 and repeats this test. This continues until the data read back is $FF (256), which is the maximum value of any one byte stored in the RAM. It then increments the memory location being tested, and repeats the $00-$FF data storage test. If any of the tested locations return an unexpected result, the program stops, and alerts you to a problem with U7 (since you got the first ROM checksum flash, but not the 2nd U7 OK flash). 

=====Third flash=====
Now, the program tests the non-volatile 5101 RAM chip at U8 (U8 AND U13 on Stern MPU-200 boards). The 5101(s) store(s) bookkeeping data, game parameters, high scores, replay levels, etc. The program tests this RAM ($200-$2FF) by reading the original nibble / byte (see sidebar), and saves it in a temporary location. Then, it stores a test pattern in the location similar to the U7 test. After the byte successfully passes the test, the original data is returned to the location, and the program loops onto the next byte. 

LEARN MORE: How does a 128 byte 5101 RAM occupy 256 memory locations? 

If you look at a pinout of the 5101 memory, you will notice it is a 128 byte device. Yet, it is addressed by the MPU via 256 memory locations ($200-$2FF). This is because the 5101 is actually a 256 nibble device - a nibble is a half-byte (4 bits). So data stored to a 5101 in a pinball machine actually only stores half of the data byte being sent to it. Which half it stores is dependent on the board design. Bally and Stern use the upper nibble for storage, and Williams used the lower nibble. Stern MPU-200 boards have an additional 5101 at U13. This stores the lower nibble in conjunction with U8 storing the upper nibble of a byte saved to $200-$2FF. This allows MPU-200 games to store more data, and avoid doing some fancy processing by getting the data in and out of the non-volatile ram area. 

For example, here's some pseudo-machine code for what happens:
*LOAD #$24 (the data you want to store is 24)
*STORE $231 (you want to store the data 24 at memory location $231)
*READ $231 (you want to read back the data you just stored)
The data returned is not #$24 as expected, but rather #$2F. The lower nibble was never stored, because the 5101 memory does not store data as bytes but rather as nibbles. To store #$24 properly would require splitting the byte into its nibbles '2' and '4'. The 2 would be stored in one memory location, while the 4 would be shifted, and stored in another memory location. 

Showing the byte as binary might be helpful to visualize what's involved. The hex #$24 in binary is %00100100. Split into nibbles is %0010 (the 2) and %0100 (the 4). The upper nibble is the one the 5101 is able to store directly, but the position in the byte of the lower nibble prevents it from being stored. A shift operation is performed 4 times on the byte to reposition the lower nibble as the upper nibble, which enables it to be stored to the 5101. Each shift moves the binary pattern to the left one bit - here's the full sequence:
*Start=%00100100
*Shift left=%0100100x
*Shift left=%100100xx
*Shift left=%00100xxx
*Shift left=%0100xxxx

This gives the #$4 in the high nibble. All byte data has to be split this way to be saved, and recombined upon reading from boards (Bally -17 and -35, Stern MPU-100) with a single 5101 RAM chip. You can see why Stern added the second 5101 RAM to their boards. It makes programming much easier! 

=====Continuity Chart for U8 5101 RAM in a Bally AS2518-17, -35 or Stern MPU-100 Board=====

{| class="wikitable"
|-
! IC & Pin#
! Data Address
! Continuity Points

|-
| U8 pin 1
| (A3)
| U7 pin 20, U6 pin 5, U9 pin 12
|-
| U8 pin 2
| (A2)
| U7 pin 21, U6 pin 6, U9 pin 11
|-
| U8 pin 3
| (A1)
| U7 pin 22, U6 pin 7, U9 pin 10, U11 pin 35
|-
| U8 pin 4
| (A0)
| U7 pin 23, U6 pin 8, U9 pin 9, U11 pin 36
|-
| U8 pin 5
| (A5)
| U7 pin 18, U6 pin 3, U9 pin 14
|-
| U8 pin 6
| (A6)
| U7 pin 17, U6 pin 2, U9 pin 15
|-
| U8 pin 7
| (A7)
| U7 pin 15, U6 pin 1, U9 pin 16, U11 pin 24
|-
| U8 pin 8
|
| GROUND
|-
| U8 pins 9&10
| (D10&D00)
| U7 pin 6, U6 pin 14, U9 pin 29, U11 pin 29 (* pins 9 & 10 siamesed together)
|-
| U8 pins 11&12
| (D11&D01)
| U7 pin 7, U6 pin 15, U9 pin 28, U11 pin 28 (* pins 11 & 12 siamesed together)
|-
| U8 pins 13&14
| (D12& D02)
| U7 pin 8, U6 pin 16, U9 pin 27, U11 pin 27 (*pins 13 &14 siamesed together)
|-
| U8 pins 15&16
| (D13&D03)
| U7 pin 9, U6 pin 17, U9 pin 26, U11 pin 26 (* pins 15&16 siamesed together)
|-
| U8 pin 17
| (CE2)
| Q5 Right Upper leg, U9 pin 40, U11 pin 34
|-
| U8 pin 18
| (OD)
| U18 pin 6
|-
| U8 pin 19
| (CE1)
| U17 pin 8
|-
| U8 pin 20
| (R/W)
| U7 pin 16, U9 pin 34, U11 pin 21, U18 pin 7
|-
| U8 pin 21
| (A4)
| U7 pin 19, U6 pin 4, U11 pin 22
|-
| U8 pin 22
| (Vcc)
| C13 Left Leg, R12 upper Leg, CR5 Lower Leg
|}
 

=====U8 & U13 5101 RAM Continuity Chart for Stern MPU-200 Only =====

{| class="wikitable sortable"
! Data Address
! U8 Pins
! U13 Pins
! Other Continuity Points
|-
|A0 || 4 || 4 || U9-9
|-
|A1 || 3 || 3 || U9-10
|-
|A2 || 2 || 2 || U9-11
|-
|A3 || 1 || 1 || U9-12
|-
|A4 || 21 || 21 || U9-13
|-
|A5 || 5 || 5 || U9-14
|-
|A6 || 6 || 6 || U9-15
|-
|A7 || 7 || 7 || U9-16
|-
|D0 || NC || 9-10 || U9-33
|-
|D1 || NC || 11-12 || U9-32
|-
|D2 || NC || 13-14 || U9-31
|-
|D3 || NC || 15-16 || U9-30
|-
|D4 || 9-10 || NC || U9-29
|-
|D5 || 11-12 || NC || U9-28
|-
|D6 || 13-14 || NC || U9-27
|-
|D7 || 15-16 || NC || U9-26
|-
|GND || 8 || 8 || U9-1
|-
|VCC (+5V) || 22 || 22 || U9-8
|-
|CS1 || 19 || 19 || U17-8
|-
|CS2 || 17 || 17 || U9-40
|-
|OD || 18 || 18 || U14-9
|-
|RW || 20 || 20 || U9-34
|}
 

Note: The U8 5101 RAM Continuity Chart below is under review for correctness. Hibler reviewing it now...
{| class="wikitable sortable"
|-
! IC & Pin#
! Signal
! Continuity Points
|-
|  U8 pin 01
|  (A3)
|  U13 pin 1, U7 pin 20, U6 pin 5, U9 pin 12
|-
|  U8 pin 02
|  (A2)
|  U13 pin 2, U7 pin 21, U6 pin 6, U9 pin 11
|-
|  U8 pin 03
|  (A1)
|  U13 pin 3, U7 pin 22, U6 pin 7, U9 pin 10, U11 pin 35
|-
|  U8 pin 04
|  (A0)
|  U13 pin 4, U7 pin 23, U6 pin 8, U9 pin 9, U11 pin 36
|-
|  U8 pin 05
|  (A5)
|  U13 pin 5, U7 pin 18, U6 pin 3, U9 pin 14
|-
|  U8 pin 06
|  (A6)
|  U13 pin 6, U7 pin 17, U6 pin 2, U9 pin 15
|-
|  U8 pin 07
|  (A7)
|  U13 pin 7, U7 pin 15, U6 pin 1, U9 pin 16, U11 pin 24
|-
|  U8 pin 08
|  GROUND
|  U13 pin 8
|-
|  U8 pin 09
|  (DI0 & DO0; D4)
|  U13 pins 9 & 10, U7 pin 6, U6 pin 14, U9 pin 29, U11 pin 29 (*pins 9 & 10, shorted together)
|-
|  U8 pin 10
|  (DI0 & DO0; D4)
|  U13 pins 9 & 10, U7 pin 6, U6 pin 14, U9 pin 29, U11 pin 29 (*pins 9 & 10, shorted together)
|-
|  U8 pin 11
|  (D11 & DO1; D5)
|  U13 pins 11&12, U7 pin 7, U6 pin 15, U9 pin 28, U11 pin 28 (*pins 11 & 12 shorted together)
|-
|  U8 pin 12
|  (D11 & DO1; D5)  
|  U13 pins 11&12, U7 pin 7, U6 pin 15, U9 pin 28, U11 pin 28 (*pins 11 & 12 shorted together)
|-
|  U8 pin 13
|  (DI2 & DO2; D6)
|  U13 pins 13 & 14, U7 pin 8, U6 pin 16, U9 pin 27, U11 pin 27 (*pins 13 & 14 shorted together)
|-
|  U8 pin 14
|  (DI2 & DO2; D6)
|  U13 pins 13 & 14, U7 pin 8, U6 pin 16, U9 pin 27, U11 pin 27 (*pins 13 & 14 shorted together)  
|-
|  U8 pin 15
|  (DI3 & DO3; D7)
|  U7 pin 9, U6 pin 17, U9 pin 26, U11 pin 26 (*pins 15 & 16 shorted together)
|-
|  U8 pin 16
|  (DI3 & DO3; D7)
|  U7 pin 9, U6 pin 17, U9 pin 26, U11 pin 26 (*pins 15 & 16 shorted together)
|-
|  U8 pin 17
|  (CE2)
|  U13 pin 17, Q5 Right Upper leg, U9 pin 40, U11 pin 34
|-
|  U8 pin 18
|  (OD)
|  U13 pin 18, U14 pin 9
|-
|  U8 pin 19
|  (CE1)
|  U13 pin 19, U17 pin 8,
|-
|  U8 pin 20
|  (R/W)
|  U13 pin 20, U7 pin 16, U9 pin 34, U11 pin 21, U14 pin 10
|-
|  U8 pin 21
|  (A4)
|  U13 pin 21, U7 pin 19, U6 pin 4, U11 pin 22
|-
|  U8 pin 22
|  (Vcc)
|  U13 pin 22, C13 Left Leg, R12 upper Leg, CR5 Lower Leg
|}

 
Note: The U13 5101 RAM Continuity Chart below is under review for correctness. Hibler reviewing it now...
{| class="wikitable sortable"
|-
! IC & Pin#
! Signal
! Continuity Points
|-
|  U13 pin 08
|  GROUND
|  U8 pin 8
|-
|  U13 pin 09
|  (DI0 & DO0; D0)
|
|-
|  U13 pin 10
|  (DI0 & DO0; D0)
|
|-
|  U13 pin 11
|  (DI1 & DO1; D1)
|  U7 pin 3, U6 pin 10, U9 pin 32, U11 pin 32  
|-
|  U13 pin 12
|  (DI1 & DO1; D1)  
|  U7 pin 3, U6 pin 10, U9 pin 32, U11 pin 32
|-
|  U13 pin 13
|  (DI2 & DO2)  
|  U7 pin 4, U6 pin 11, U9 pin 31, U11 pin 31
|-
|  U13 pin 14
|  (DI2 & DO2)
|  U7 pin 4, U6 pin 11, U9 pin 31, U11 pin 31
|-
|  U13 pin 15
|  (DI3 & DO3)
|  U7 pin 5, U6 pin 13, U9 pin 30, U11 pin 30 (*pins 15 & 16 shorted together)
|-
|  U13 pin 16
|  (DI3 & DO3)
|  U7 pin 5, U6 pin 13, U9 pin 30, U11 pin 30 (*pins 15 & 16 shorted together)  
|}
 

=====Issues with 5101 RAM chips=====

The socket at U8 (and U13 for Stern MPU-200) is very close to the corrosion effects of the alkali of a leaking battery. This is often the cause of boards not showing a 3rd flash. There are traces on the component and solder side of the board, and the socket can hide corrosion to these traces. In turn, the corrosion can affect the 5101 chip's contact with the socket pins. Be careful when replacing corroded or SCANBE sockets at U8, U13, U11, etc. Bally/Stern boards run a number of exposed traces on the top-side of the board in between socket pins. It is extremely easy to splash a miniscule amount of solder, accidentally bridging a socket pin to an adjacent in-between signal line. Use of a logic probe (ground lead at TP4 and 5V at TP5) and sampling all of the signals after a socket replacement will make it very easy to verify your work and locate crossed up (typically scratchy/floating) signals! This can save you minutes or hours of troubleshooting. 

Unless the board is unusually clean, a rebuild of a non-working board should include replacing the socket at U8 (and U13, for MPU-200). The chip is an oddball configuration with 22 pins which makes machine pin sockets hard to find. Use 2 strips of machine sockets, so that you can solder both above and below the board. Inspect the traces closely on the top; it is best to avoid soldering on the top of a board unless you have to as it makes it extremely difficult to desolder the sockets in the future. Take extreme care not to make a solder bridge of the traces on the component side, as it is easy to do. Performing a continuity test to adjacent socket legs after soldering is a good practice. Also, note that some of the pins are shorted together. (see above) 

Failure to achieve the third flash can also be attributed to the following: If the U8 and U13 (MPU-200) show correct continuity as charted above, and the 5101 RAM is known to be good, the problem could lie with the U19 (4011) chip. On Stern MPU-200, replace U14 (4572) instead. Finally, although rare, the 6800 CPU at U9 could be bad. 

The speed of the 5101 RAM chip can make a difference in the functioning of an otherwise good MPU board. If a slow chip is put into a good MPU, strange behavior such as inconsistent boot ups, incorrect score display behavior, among other things can result from the RAM not being able to keep up with the demand from the CPU. Below is a list of 5101 RAM chips and their speed. A lower number means a faster chip. A Stern MPU-200 board needs 2 chips of at least 450ns, while the Bally AS 2518-17 or -35 and the Stern MPU-100 can work correctly with a slower chip of 650ns. The stern mpu-200 board should have matching speeds for the 2 RAM chips, as they are selected and accessed simultaneously. A faster chip is fine for a replacement, but there will not be a performance enhancement. It is usually best that the speeds of the RAM chips match (eg, 450ns and 450ns, not 450ns and 150ns), or there could be strange side effects, such as strange sound behavior and audits not saving correctly to RAM. 

*PCD5101P (Philips manu) 150ns
*5101-1 450ns
*5101L-1 450ns
*5101L-2 450ns
*5101-2 450ns
*5101 650ns
*5101L 650ns
*5101-3 650ns
*5101L-3 650ns
*5101-8 800ns (too slow for any board)

The 5101 RAM chip is especially sensitive to static discharge that will damage it, so take extra precaution in handling.

The memory RAM replacement chip sold by Tom Callahan at pin-logic.com (now offline) uses a 6116 and special adapter, and makes a good replacement. Pin-logic also sells the static ram chips that do not require batteries for backup; although he advertises that these do not work in the Stern MPU-200 board, 2 of them did work on a test board. Another source for varying types of 5101 and 6116 replacements is a blog site [http://warpzonearcade.com/?p=392 WarpZoneArcade]. There is information how to roll-your-own 5101 replacement adapters. Or, visit its accompanying site, [http://pinforge.com PinForge] for pre-made RAM adapters. A source for [http://www.pinitech.com/products/stern_mpu200_ram.php MPU-200 pre-built adapters is Pinitech]. Here is a list of [[MPU_Battery_Replacement_Options#Products|additional sources for NVRAM adapters]]. 

If you opt to go for a (recommended) NVRAM solution, a highly recommended modification (after discarding the battery!) is to power the NVRAM directly from the +5V line and remove the 12V line circuitry. This can be easily accomplished by cutting out R11. And then cut out CR5 and CR7 and replace these two with jumper wires (or 0 ohm resistors).

=====Fourth and Fifth flashes=====
Next, the program tests each of the 2 6820/6821 peripheral interface adapters (PIAs) at U10 and U11, starting with U10. The PIAs are set to a known state, then data is stored and read back from them to verify their registers are functioning properly. It is important to note that it is not possible for the PIA to be 100% tested with this test, as external data would have to be fed in to do so. However, the test will at least test the internal registers. It would be possible for a PIA to pass the self-test, but still not work properly with external inputs. 

Assuming the PIAs pass, the fourth (U10) and fifth (U11) LED flashes occur. The LED itself is connected to the U11 PIA. So if the LED is locked on, U11 might be bad. It's worth letting a locked on LED board 'sit' for a minute or so to see if the game boots all the way up without flashing each test step. This is an example of how a PIA can pass self test but still be bad. The LED control pin has no feedback as to if the LED is in fact flashing. 

Because the PIA tests all possible values in all possible registers, anything connected to the registers will be activated very briefly as well. This manifests itself most obviously via the flipper relay which on most games will click during the U11 PIA test. Holding the flipper buttons in will usually result in a flip or half-flip during this test. This could be helpful if purchasing a machine/repairing one in a noisy environment and you want to see how involved you might getting before removing the backglass to visually see the LED diagnostic flashing. 

=====Sixth flash=====
The sixth flash waits for an external input on U11 pin 40 from the display interrupt generator circuit, which occurs 320 times a second. If you're missing the sixth flash, there may be a problem with either the U12 circuit, '''OR''' the input pin on the PIA. A logic probe, oscilloscope, or a multimeter on pin 40 can help you determine which is at fault. A logic probe will pulse if the display circuit is operating; the scope will show you the signal's waveform; and the multimeter should settle on a voltage somewhat between 0-5 volts. 

One definite reason for lack of a sixth flash is a poor connection on the ground side of C16, the film capacitor. If there isn't a sixth flash, but all other tests and measurements are good, it's a safe bet that U11 is bad and needs to be replaced. 

Note that the sixth flash does '''NOT''' check for the proper '''frequency''' of operation of the display generation circuitry. As long as there is a pulsing signal (technically, ONE state change), the test is marked good and the program allowed to continue. 

=====Seventh flash=====

Note: Before troubleshooting further, if testing on the bench with only +5 and +12V applied, a 7th flash will not happen even if the MPU is fully functional. The 7th flash requires the +43V solenoid voltage.

For bench testing, it is possible to "trick" The MPU into completing the 7th flash without applying the solenoid voltage by temporarily jumpering the top of R17 and the top of R23.

The 7th and final flash waits for an external input on U10 pin 18 from the zero crossing detector circuit, which occurs 120 times a second (as the AC waveform passes or "crosses" 0 volts). Diagnosis of issues with the 7th flash are similar to the 6th flash. The input to pin 18 can be measured to determine if the signal is present or not. A signal present, but no flash could mean a bad U10 PIA. Again, a missing signal usually points to missing solenoid voltage. The source of the zero crossing signal is derived from the solenoid voltage delivered from the rectifier board. Equally, if a signal is present, there may be an issue with the zero crossing detection circuit itself.

Note again that the seventh flash does '''NOT''' check for the proper '''frequency''' from the zero crossing detector. It simply checks for a pulsing signal, and only checks for '''ONE''' transition.

After the 7th flash, the program does some background setup: reads dip switches, enables the displays, attract modes, switch scanning etc. in a 'game over' mode, waiting for player input. The LED will sometimes be dimly glowing or even pulse as this happens, which is not a cause for alarm. The LED circuit around Q2 can be rebuilt if this is concerning, but it is harmless.

One interesting anomaly is that the 7th flash will not occur, if there is a bad 1N4004 diode (CR3) used on -32 / -50 sound boards. On these two sound boards, the +12VDC used on the boards is derived from the +43VDC solenoid voltage, and isolated by CR3.
 

[[File:R113_and_R16_on_bally_-35.jpg|300px|left|thumb|Bally MPU with burned R113 and R16]] 
If there is +43VDC solenoid voltage present, but no 7th flash, check R113 and R16 on the MPU. These two resistors take the 43v and form a voltage divider. If these resistors burn they can stop the 7th flash from happening. Test point 3 should show approximately 21.5 pulsating DC if the resistors are ok.
 

If there is still no 7th flash and there is 21.5 VDC on TP3, check CB1 which is on U10 pia pin 18. It is the logic side of the zero crossing and should be pulsing. If it is stuck low or stuck high replace u14.
 

====Chip Sockets====
Reliable socket connections are a requirement for any printed circuit card to work as designed. Old sockets, as discussed below, should be replaced. Use extreme care in desoldering the old sockets, the traces and pads on Bally Mpu-17 boards are easily lifted. It is possible to lift other boards' traces and pads as well, especially if any battery corrosion is in the area.

The chip sockets on old Bally and Stern boards (also most any board of this era) are long past their reliable lifetimes. They may work, but they may also cause intermittent connections that will have you chasing your tail tracking down odd problems with your game. Like the 40-pin interconnect used in Williams System 3-7 games, these sockets should always be replaced. On Bally/Stern MPUs, these include U2, U6 (more game ROMs if you don't combine the ROM images), U7 RAM, U8 5101 RAM (and U13 5101 RAM if a Stern MPU-200), U9 CPU, U10 and U11 6820/6821 Peripheral Interface Adapters. 

Perhaps the most maligned socket brand, and rightfully so, is the Scanbe brand. In the picture below, you can see why. These 30+ year old sockets passed the point of reliability many years ago. Included in the Scanbe socket picture below are two pins pulled from a Scanbe socket. The pins were designed to grip the SIDES of the IC legs, unlike the design of modern sockets that grip the front and back faces of the IC leg. Get rid of them now.

<center>
<gallery widths=400px heights=400px perrow=2 caption="Poor quality and old sockets found on many early pinball machine circuit boards">
File:Bally MPU Sockets Orange.JPG|<center>It's hard to believe that these "brown" sockets ever worked.</center>
File:Bally MPU Sockets Augat.JPG|<center>The spring strength of the pins in these AUGAT sockets eroded over time.</center>
File:ScanbeSocket.jpg|<center>Closeup of the infamous "Scanbe" brand socket. "Scanbe" is molded into the top of the socket face.</center>
File:SternCraptasticSocket.jpg|<center>This style of Molex socket is particularly troublesome. Like Scanbe sockets, they don't work well after many years and the legs are so large that they are almost as hard to remove as a "WPC Snap Cap" without damaging the delicate through holes found on Stern MPU-100 MPUs</center>
</gallery>
</center>
 
<center>
<gallery widths=300px heights=300px perrow=3 caption="One Method of Socket Removal (works for at least ScanBe and Augat sockets)">
File:PryScanBeSocketOff.jpg|<center>Prying off an OEM Augat socket. Be careful to not crush/damage traces as you pry.</center>
File:HeatAndRemoveEachPin.jpg|<center>Heat and remove each pin individually.</center>
File:CleanThroughHoles.jpg|<center>Clean up the through holes with your favorite solder sucker. Here, a Hakko 808 is being used.</center>
</gallery>
</center>
 

====ROMs/ICs====
this is a stub

The Motorola part number equivalencies that appear on the top of U9, U10, and U11 are...
*SC44216P = 6800 microprocessor
*SC44067P = 6820 PIA

====Clock Signal====
replacement 9602 board: http://www.homepin.com/9602.html

replace with a 6802: http://pinballeon.com/6802/e6802.htm

===How to make a Benchtop power supply for the MPU board===
[[file:power_Supply_Connector.jpg|300px|left|thumb|ATX Power Supply connector modification]]
[[file:power_Supply_hookupR.jpg|300px|thumb|right|Bench Top Power Supply hooked up to MPU board]]
Being able to test the MPU board on the bench is a great advantage in trouble shooting. A benchtop power supply is quite easy and inexpensive to put together. All that is required is a computer supply and some mods to the connectors. An ATX or old AT computer power supply will supply the + 5 vdc and +12 VDC that is needed to run the first 6 flashes. The 7th and final flash requires +43 vdc and cannot be supplied by the ATX power supply, but the MPU can be "fooled" into thinking it is present. 
An ordinary ATX computer can be had used or new for under $20. Exact wattage is unimportant. In order to be able to switch the power on and off, the 20 pin connector on a ATX supply must be modded. This is not necessary on an older AT supply. Because modern motherboards use a soft power on/off, the green pwr-ON at pin 14 must be tied to the black COM ground at pin 13 or 15 thru 17. This can be done easily done with a short length of wire and a .062 pin attached to each end and shoved into the 20 pin connector at pin 14 and 15. Or, simply cut the wires free from the connector and solder them together.<bt>

Take one of the molex 4 pin connectors which have 1 RED wire (+5 vdc), 1 YELLOW (+12 vdc) and 2 BLACK ground wires. Attach an alligator clip to the RED, YELLOW and one BLACK lead. A good tip is to use the color coded rubber boots to protect from accidental shorts and keep it easier to identify the leads at a glance. If you should accidentally short the +12 volts to +5 via you will kill all the ICs on the board! 

To use the power supply, with the power OFF, clip the black lead to TP 4 at the top right of the board. Clip the RED +5 vdc lead to TP 5 at the bottom right, near the battery. Finally clip the YELLOW +12 vdc to TP 2 on the bottom left of the board. Make certain that this connector is not on or shorted to TP3 which is nearby. This error would damage the board, so double check this before turning on the power. Connect the power supply to 120vdc outlet and flip the switch to boot. 

Upon power up, the brief flicker should be seen, then 6 (not 7) more flashes for a good board. The 7th flash cannot be achieved without +43vdc present. On some occasions, the LED will lock on and not go into the flash sequence. This COULD BE because the MPU is sensitive to the exact voltage supplied and will not boot with a computer supply. If the board successfully boots in the game, this could be the cause. This condition is rare, but possible. Also, if the LED locks on immediately, try doing a manual reset by briefly shorting together pins 39 and 40 of the U9 CPU with a small screwdriver. This forces the pin 40 to go low and begin the boot process. It is also possible to short the junction of resistors R1 and R3, on the right side of R1, to board GROUND with a jumper clip to accomplish the same effect.
 

===Solenoid Driver Board Issues===
====Failed LM323K or Mission 5VDC====
While the LM323K (or 7805) is a reliable voltage regulator, periodically, they do fail. 
:::A discussion on replacing the LM323K can be found [https://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Driver_Board_LM323K_5V_Regulator here].

====Testing and Replacing Transistors====
[[File:Transistor_Replacement.jpg|300px|left|thumb|Before and After of Replaced Drive Transistor, Diode, and Resistor]] 
To test a transistor set the DMM to diode test mode. With the game turned off, place the black lead on the metal tab of the transistor. Probe the two outer legs of the transistor with the red lead. The DMM should read between .4v and .6v (some DMM will show 4xx - 6xx). The center leg should be a dead short to the metal tab. If either outer leg reads anything outside of the .4v to .6v range, the transistor more than likely needs to be replaced. Use a TIP-102 as the replacement transistor. 

If a transistor needs to be replaced it is usually a good idea to check / replace the 1n4004 diode and 330 ohm resistor associated with that transistor as these will often burn / short. Also check the diode on the associated coil, it is likely to be shorted as well.
 

The transistor output can also be tested by using the diagnostic LED on the MPU board. An alligator test lead and a component lead clipping or finishing nail are needed.
#With the power off, attach one end of the alligator test lead to TP6 located on the MPU board. TP6 is located in the vicinity of of the diagnostic LED.
#Next, attached the other end of the test lead to the component lead clipping or finishing nail.
#Turn the game on, and place it into solenoid test or just allow it to remain in attract mode.
#Carefully place the lead with the finishing nail into one of the many solenoid outputs on the solenoid driver board (J1, J2, or J5).

If the LED lights briefly as the solenoid test cycles, the transistor and header connection on the solenoid driver output is good.

If the LED does not light, suspect the following...
*a failed transistor,
*a cracked header joint,
*a discontinuity between the transistor and the header pin,
*the associated diode on SDB has failed,
*the 3081 transistor array on the SDB,
*the 74154 4 to 16 decoder on the SDB, or
*failed connections on J4 of MPU and / or J4 of the SDB, or bad daisy-chain connection at J1 of the sound board (if a sound board is used)

If the LED remains on, this means that the transistor is shorted. The exceptions are the diagnostic button return connection (ground) located at J2 pin 7, and the coin lockout coil ground at J2 pin 8. The coin lockout is a high resistance coil, and can remain on without destroying its associated drive transistor. 

The above test using the MPU diagnostic LED can be performed with the J1, J2, or J5 connectors connected or disconnected. '''WARNING: DO NOT place the lead on the J3 or J4 connectors on the solenoid driver board.'''
 

====Replacing a failed Solenoid Transistor====
If a coil has locked on, or any SE9302 (TIP-102) transistor has failed the diode test with your multimeter, replace the following components on the Solenoid Driver board as a set. In addition, also test the playfield coil disconnected from the game wires, with the ohm setting. The coil should have a value higher than 3 ohms up to around 15 ohms. Lower than 3 ohms is a dead short and will heat up and burn up components if the fuse does not blow. The coil diodes should also be replaced if the coil has locked on. Since the diode must be disconnected from the lugs to test it, it just makes sense to clip it off, replace the diodes, and not bother to test them. 1N4004 diodes or better, (1N4005,6 or 7) should be used. You cannot test the diode in place. The diode band (cathode) goes to the power lug of the coil, usually a double wire connection, because the coils are daisy chained. If it is a single wire, look at another nearby coil and note the color of the double wire. 

Replace any suspect SE9302 with a TIP-102 transistor. They are used in many pinball machines, so having a small supply of them is highly recommended. The TIP-102 is a more robust transistor and can handle more current. On the SDB replace the associated diode, and resistor for any driver transistor you replace. Check the associated pin for signs of burning and replace the header pins and connector pins if they have turned brown or look corroded. If a diode and/or resistor has actually burnt, check for continuity and make sure the circuit board traces have not also burnt up. This is a common problem when someone has over-fused the game. 

====Solenoid Transistor Mapping====
[[File:TransistorMappingThumb.jpg|300px|thumb|left|Bally Solenoid Transistor Mapping|link=Transistor Mapping for Bally Games]]
[[File:Stern_TransistorMappingThumb.jpg|300px|thumb|right|Stern Solenoid Transistor Mapping|link=Solenoid Transistor Mapping for Classic Stern Games]] 
To view a chart of what specific transistor controls a specific coil on a particular Bally game (transistor mapping), click the image at left. 
To view a chart of what specific transistor controls a specific coil on a particular classic Stern game (transistor mapping), click the image on the right.
 

==== Solenoid Driver Board Transistor, Resistor, Diode & associated Connector Chart====
{| class="wikitable"
|-
! TIP 102
! 1N4004 Diode
! 330 ohm Resistor
! SDB Connector
|-
| Q1
| CR1
| R9
| J1-pin 2, J2-pin 9
|-
| Q2
| CR2
| R6
| J1-3, J2-4
|-
| Q3
| CR3
| R16
| J2-5, J3-4
|-
| Q4
| CR4
| R18
| J1-5
|-
| Q5
| CR5
| R10
| J2-10
|-
| Q6
| CR6
| R12
| J2-11
|-
| Q7
| CR7
| R14
| J2-12
|-
| Q8
| CR8
| R20
| J5-10
|-
| Q9
| CR9
| R26
| J5-9
|-
| Q10
| CR10
| R28
| J5-15
|-
| Q11
| CR11
| R32
| J5-14
|-
| Q12
| CR12
| R30
| J5-13
|-
| Q13
| CR13
| R22
| J5-12
|-
| Q14
| CR14
| R24
| J5-11
|-
| Q15
| CR15
| R39
| Flipper Relay
|-
| Q16
| CR16
| R34
| J2-6, J3-7, J5-8
|-
| Q17
| CR17
| R42
| J5-7
|-
| Q18
| CR18
| R45
| J2-15, J3-9, J5-3
|-
| Q19
| CR19
| R47
| J2-8
|-
| '''TIP 102'''
| '''1N4004 diode'''
| '''330 ohm Resistor'''
| '''SDB Connector'''
|}

====Solenoid Driver Upgrades====
[[File:BallySternSDBupgrades.jpg|300px|left|thumb|Visual of Solenoid Driver Upgrades. Note that TP1 and TP3 are tied together.]]
There are several upgrades which can be performed to reduce stress on connectors. 

The two 5v test points on the SDB can be tied together. On the solder side of the driver board jump TP1 and TP3 together. Be careful to apply this to the correct test points. This eliminates a possible failure point on J3 pins 13 and 25. Note that TP1 is for the raw +5vdc coming directly from the regulator. TP3 is for the voltage that feeds all the +5vdc circuits in the driver section. If there's a problem in the driver section, it can be isolated by removing this jumper, and removing pin 13 or 25 from J3.
 

Next the C23 capacitor needs a common ground with the rest of the SDB. Jump the negative side of C23 to a convenient ground trace. On most boards there is a ground trace in the vicinity of the C23 negative lead. Other boards might require a longer jumper. Scrape the solder mask off the trace to get a good solder surface to solder the jumper. If replacing the C23 capacitor, (a good idea, they can be 30+ years old at this point), it may be possible to leave the negative lead "long" on the new capacitor. Then, bend the leg down to the ground trace, and solder it in both the mounting hole and the trace. 

The C26 capacitor needs a ground upgrade similar C23 mentioned above. Tie the negative side of C26 to the ground trace located at the perimeter of the board. This connects both C23's and C26's negative side to a common ground on the SDB. The goal of these modifications is to provide redundant grounds with the least resistance possible.

On the Stern SDU-100 and the older Bally AS-2518-16 boards there is a "gap" between pin J3-22 and J3-23. Both are ground connections. Use some additional solder and connect the two, bridge the "gap". Now all grounds (J3-18 thru J3-24) are tied together.
 

====How to Rebuild the Bally/Stern Solenoid Driver Board====
The Solenoid Driver board is critical to the operation of the electronics of the game. The Solenoid Driver Board (SDB) comes in several types for Bally and Stern, and are completely interchangeable for any game of the 6800 MPU type. The SDB supplies the game with the voltages for the MPU, coils and high voltage for the displays. Recommendations are given below for replacing components to ensure proper operation and reliability. In all cases, do the ground modifications as shown in another part of this Wiki.

'''Minimum Recommendation for a Working board'''

:At a minimum, replace both large capacitors on a working or non-working board, especially if they look original. Original caps are often metallic blue or metallic silver, and are at least 30 years old and due to fail, owing to the electrolytic chemicals in the capacitor drying up. The capacitor at C23 has a factory value of 11,000uf and 20 volts, but these values are not easily found these days. An electrolytic capacitor of between 11,000uf and 16,000uf and 25 volts or greater can be safely substituted. A screw terminal capacitor makes for a easy installation, but a snap cap with leads can be used as well. Recent prices for screw terminal caps have increased greatly so this may be a factor in your decision.

:The high voltage capacitor at C26 has an original spec of 160uf and 350 volts and is an axial electrolytic capacitor. Once again, this part is difficult to encounter with these exact specs, but an axial or radial cap from 150uf to 180uf and at least 350 volts can substitute. 400v or 450v caps can be had in a radial format and size that will fit. With a radial cap you will have to make leads that bend back to the negative (-) solder pad.

'''Preferred recommendation for a working board'''

[[File:BallyAndSternFracturedSolderJoints.jpg|300px|right|thumb|Clearly fractured .156 header pins on a Bally single sided driver board]]
:Besides the above, replace ALL the .100 and .156 molex header pins and the connector terminals in the nylon housings with Molex TRIFURCON Phosphor Bronze tin plated crimp terminals (Molex Part# 08-52-0113 for 18-20 gauge Wire, and 08-52-0125 for 22-26 gauge) for the .156 connectors, and Molex .100 tin plated Phosphor Bronze crimp terminals, (Molex Part#08-52-0123). Do NOT skimp on this step and just do one or the other. The receptacles can be re-used if not burnt. If replacing the receptacles, the locking or non- locking ramp type are fine. Often, the connector at J5 does not cover the last few pins. I don’t like this personally, although no harm can be done if the key is in place.

:Check every resistor that is usually covered by the plastic shield between the two big heat sinks for correct value and no sign of burn. Replace any that are suspect. Use the diode function on your multimeter to check the zener diode at VR1 and the 1N4004 diode. The zener diode can be difficult to source. See below for recommendation. 

'''Gold Standard for Working or NON-WORKING board'''

:It doesn’t make too much sense trying to trace down the exact problem and replacing only the bad components on a NON-WORKING board. Better to replace every possible bad component and start fresh. To ensure long life and proper operation of a working board, in ADDITION TO THE ABOVE, it is recommended that the components below are replaced regardless. Below is a list of components that effect the HV and +5 volt logic circuits on the SDB. Replace them all! * The Stern Revision J board is rather different, & a component list for that board follows. It can be identified by the extensive silk screening of each component and its function as seen in the 4th photo above, and by the HUGE 2 Watt and (2) large 1 Watt resistors. It is most often found on late date Stern games like Flight 2000 or Viper, etc.

'''Component replacement list for Bally AS2518-16 or -22 and Stern SDU100 SDBs, except * revision J'''

'''Resistors'''
*R51 22k ohm 1/2Watt
*R52 390 ohm 1/4 Watt
*R54 8.2k ohm 1/4 Watt
*R55 1.2k ohm 1/4 Watt
*R56 82k ohm 1/2 Watt
*R35 100k ohm 1 Watt

'''Diodes'''
*CR21 1N4004 400PIV 1 amp or better (1N4007, etc.)
*VR1 Zener diode 1N5275A 140 volts, 1/2 Watt. Can Sub 1N5275B or NTE 5099A

'''Transistors'''
*Q21 2N3584 250volts, 2 amp, TO-66 NPN
*Q22&23 2N3440 250 volts 1 amp TO-39 NPN
*Q20 LM323K (original 78H05KC or LAS1405)

'''Capacitors'''
*C27&28 .01 uf 400 vdc metal polyester capacitor

*RT1 25k ohm potentiometer (2 types) a 15mm black one, Piher Part# PT15LH06-253A2020 or a 6mm blue one BournsPart#3306P-1-253

'''Stern SDU100 revision J'''

*R35 100k ohm 1 Watt
*R51 33k ohm 2 Watt
*R52 390 ohm 1/4 W
*R53 2.4k ohm 1/4 W
*R54 8.2k ohm 1/4 W
*R55 1.2k ohm 1/4 W
*R56 82k ohm 1/2 Watt
*R73 3.3 ohm 1/4 W
*R74 470 ohm 1/4 W
*R75 100k ohm 1 Watt
*CR22 1N4004 or better
*Q24 2N3904 Transistor

Other diodes, transistors and capacitors as above for AS2518-18

====Modify the Display Fuse holder====
[[file:Fuse_adaptor.jpg|left|300px|thumb|alt=alternative text|Fuse adapter for the SDB allowing use of a common fuse]] 
Some versions of the solenoid driver board have a small fuse present for the displays. This fuse is a difficult to find, expensive, type 8AG 3/16 amp fast blow fuse. It would be best when rebuilding the SDB to replace the fuse holder with new clips and convert it to a more commonly available 3AG type. The original value of 3/16 amp can be substituted with a more common 1/4 amp fast blow fuse without worry of over fusing the circuit, due to inherent variations of tolerance by the manufacturer. 

Perform the following to replace the existing 8AG fuse holder:
*Bend up or clip off the upper solder lead of the clip
*Move the TOP fuse holder up one hole
*Solder a 20 ga. wire from the base of the clip back down to the lower hole. 

Be careful not to solder the clips with the inner "ears" facing in the wrong direction, or the work will have to be redone. It may be helpful to put an old 3AG fuse in the clips to aid in spacing, and assure that the "ears" are positioned correctly. The fuse will also hold the clips in place while soldering. See the photo above. Of course, an inline fuse holder can also be used instead, but looks less professional.
 

===Solenoid problems===
Before proceeding to diagnose solenoid or problems, see this section: [[General#How_coils_are_driven| How coils are turned on]]. 

One very common issue with solenoids not functioning on the playfield is a blown fuse under the playfield. This fuse, typically a 1 amp slo-blo, powers all of the solenoids on the playfield, except the flippers. The symptom of a blown playfield fuse is when the flippers, knocker, coin lockout relay, and chimes (if the game uses chimes) function in solenoid test, but no other solenoids will enable.
 

====Game starts, ejects ball, but no other playfield coils or flippers work====
On early Stern games, if the symptoms include all these:
* There are no blown fuses
* The game boots
* The driver board relay engages
* The coin door relay engages
* When a game is started it ejects a ball into the shooter lane
* No other playfield coils work
* The flippers don't work

Be sure to check the backglass for the tilt lamp to make sure the game isn't in tilt. If it's on (or if the lamp isn't working) check the slam tilt switches and ball tilt switch. It's possible that the ball on the ball tilt assembly got stuck at the rear of the assembly.

====Solenoid Expander Board and Diodes at the Coils====
[[File:BallyEightBallDeluxeSaucerCoilDualDiodes.jpg|300px|thumb|left|Bally Eight Ball Deluxe Limited Edition Saucer Coil showing dual diode connections at the coil lugs.]]
[[File:EightBallDeluxeDualDiodeSchematic.jpg|300px|thumb|right|Bally Eight Ball Deluxe Limited Edition Schematic snippet showing dual diode connections and 6 coils multiplexed by the solenoid expander board relay.]] 
The solenoid expander board allowed additional coils to be installed in games beyond what was originally supported on the driver board. The relay essentially worked as an A/B switch for two banks of coils. Each return line could then control two different coils, depending on which way the relay was switched.
 

===Lamp problems===

====Lamp Sockets====
Most lamp problems stem from the sockets themselves. The recommended best practice for problem sockets is to replace them. If you want to try and get them working reliably, here are some things you can try. 

First off, clean the inside of the socket. There are nice dremel tool tips to help, but even a screw driver can scratch off some crud from inside a socket. Sometimes a light squeeze on the socket with pliers can make the bulb stay in nice and snug and be less likely to move and stop lighting. 

[[File:Fixing_Lamps.jpg|300px|left|thumb|Repairing Single Lamp Sockets]]
The bare wire running under the playfield for controlled lamp power carries 5-6 vdc and is usually soldered onto the sockets mounting bracket. The mounting bracket then connects to the outside of the socket. After 30 years or so the connection from the mounting bracket to the lamp socket's outside can break. To remedy this there are two things you can try. You can solder the barrel of the lamp socket directly to the base of the socket (so it can no longer swivel). This can be kind of tricky without a higher power soldering iron - if you use paste flux it is easier. Radio Shack also sells a solder called "Crystal Clear" flux which works well. To do this well, you need to either sand or file (the file works best and saves your fingers) the area to be soldered on the base and the barrel. The other option is to run a small jumper wire that connects the bare wire directly to the outside of the socket, thus eliminating the poorer connection between the mounting bracket and barrel. 

Another less common issue is the connection between the lamp socket's solder lug (insulated wire to the driver board connects here), and the back tip of the socket (what moves out/in and is spring loaded to hold bulb in place). What you can do here is to move the insulated wire off of the lamp socket's solder lug and solder it directly to the back of the socket tip. This eliminates any potential connection issues with the solder lug/tab and the back pin. 

Before soldering onto a socket, either the barrel or the spring terminal, it must be sanded or filed clean or the solder will not stick. Paste flux or the crystal clear flux solder recommended above will help. If you have a temperature controlled soldering station crank it up above what you would normally use for boardwork to about 800 degrees.
 

[[File:Lamp_Mounting_Brackets.jpg|300px|left|thumb|Repairing Multiple Lamp Sockets Tied Together]] 
Another issue is the multiple lamp mounting boards/brackets like those used in Stern Big Game, Meteor, and others. The lamp sockets are riveted to these mounting boards and are not replaceable. These mounting boards suffer from a bad connection to the bare controlled lamp wire running under the playfield. You can either solder each lamp barrel to the base plate or run a daisy chain wire from barrel to barrel to help fix issues with the sockets. Again, lamp sockets need to be sanded (200 grit works well) or filed before solder will stick.
 

==== General Illumination (GI) Problems ====

[[File:BallyBurnedGIHeader.jpg|left|thumb|300px|The primary cause for General Illumination problems...burned connectors.]] 
One of the main reasons for lack of GI in Bally/Stern games is burned connectors on the rectifier board. If your game's GI connector looks like the one pictured at left, it's time to replace it. Generally, it's good policy to replace both the male header pins and the pins within the female plug.

The female plug can be reused if not too toasty. Using a small flat blade screwdriver, drive the blade through the slot where the pin's "tang" locks it into place. This will release the tang and smash the old pin. Only moderate hand pressure is needed to accomplish this. Once the tang has been released, the wire and pin should pull from the female housing easily. Crimp a new TriFurcon pin on to improve connectivity. Be sure that the "key pin" is installed on the female plug in the right location.
 

==== Controlled Lamp Problems ====

=====Lamp Driver Board SCR / Connection Chart=====
{|class="wikitable"
! scope="col" | SCR
! scope="col" | MC14514
! scope="col" | Connection
! scope="col" | SCR
! scope="col" | MC14514
! scope="col" | Connection
! scope="col" | SCR
! scope="col" | MC14514
! scope="col" | Connection
! scope="col" | SCR
! scope="col" | MC14514
! scope="col" | Connection

|-
| Q1 || U1 || J1-24 || Q16 || U1 || J2-22 || Q31 || U3 || J2-2 || Q46 || U4 || J3-18
|-
| Q2 || U1 || J1-25 || Q17 || U2 || J1-11 || Q32 || U3 || J3-27 || Q47 || U4 || J2-10
|-
| Q3 || U1 || J1-26, J2-21 || Q18 || U2 || J2-20 || Q33 || U3 || J2-11 || Q48 || U3 || J3-16
|-
| Q4 || U1 || J1-28 || Q19 || U2 || J2-15 || Q34 || U2 || J1-2 || Q49 || U3 || J3-17
|-
| Q5 || U1 || J2-16 || Q20 || U3 || J1-13 || Q35 || U2 || J1-3 || Q50 || U4 || J3-12
|-
| Q6 || U1 || J2-14 || Q21 || U2 || J1-12, J2-12 || Q36 || U3 || J3-26 || Q51 || U4 || J3-15
|-
| Q7 || U1 || J1-27, J2-13 || Q22 || U2 || J1-10 || Q37 || U3 || J2-23 || Q52 || U4 || J2-5, J3-13
|-
| Q8 || U1 || J1-23 || Q23 || U2 || J1-4, J2-8 || Q38 || U3 || J3-25 || Q53 || U4 || J2-3, J3-14
|-
| Q9 || U1 || J1-14 || Q24 || U2 || J1-5 || Q39 || U3 || J2-4, J3-24 || Q54 || U4 || J3-11
|-
| Q10 || U1 || J1-15 || Q25 || U2 || J1-6 || Q40 || U3 || J2-9, J3-22 || Q55 || U4 || J3-9
|-
| Q11 || U1 || J1-16 || Q26 || U2 || J1-7 || Q41 || U3 || J3-20 || Q56 || U4 || J3-10
|-
| Q12 || U1 || J1-19 || Q27 || U2 || J1-9 || Q42 || U3 || J3-21 || Q57 || U4 || J3-1
|-
| Q13 || U1 || J1-17 || Q28 || U2 || J1-8 || Q43 || U3 || J2-7 || Q58 || U4 || J3-2
|-
| Q14 || U1 || J1-18 || Q29 || U2 || J1-1 || Q44 || U3 || J3-19 || Q59 || U4 || J3-4
|-
| Q15 || U1 || J2-23 || Q30 || U3 || J2-6 || Q45 || U4 || J2-1 || Q60 || U4 || J3-3
|}
 

===== Failed Lamp SCRs =====
[[File:Mcr106_subbed_for_2n5060.jpg|300px|left|thumb|Using an MCR-106 in place of a 2N5060]]
Lamp locked on 
The usual cause for a lamp that is stuck on is a failed SCR. Bally/Stern employed two different SCR parts to control lamps. The MCR-106 is able to drive two lamps at the same time. The smaller 2N5060 will drive one lamp only. These SCRs fail from sinking too much current, from old blackened bulbs (which draw more current) or from being shorted to something under the playfield carrying high voltage (solenoids). If you accidentally short several lamps together, this can cause the SCR to fail also. 

If you are in a bind it is possible to use an MCR-106 in place of a 2N5060, with one caveat. Two legs of the MCR-106 SCR need to be reversed. As you are looking at the board the top and middle leg of the MCR-106 need to be reversed.
 
'''<nowiki>**Note:</nowiki>''' a 2N5060 '''CANNOT''' be used instead of an MCR106 which drives more than one lamp.
 

Lamp never lights 
A lamp that never lights might be caused by a failed SCR or the connection from the lamp driver board to the lamp socket. Use your meter's continuity test to "buzz" the path from the SCR to the lamp itself. Lack of continuity means that either the lamp driver board male header/female housing connector or the wire from the female housing to the lamp socket is severed. 

Some lamp boards feature buffer and (4514) decoder chips. A failed buffer or decoder chip can prevent a lamp from lighting. If you have multiple lamps out, and you have tested the wiring for each, look back to the chips to see if the lamps in question share a chip in common. Refer to the game's schematics. If so, and the SCRs have tested good, the chip may have failed. A logic probe is the best tool for this diagnosis.

[[File:LampDriverBoardCrackedHeaderPins.jpg|left|thumb|300px|A Bally Lamp Driver board with clearly cracked header pins. Cracked headers like these cause the lamp to be intermittent or to not light at all.]] 
The .100 headers on lamp driver boards are subject to a lot of stress. This is mostly because the backbox cabling has typically been liberated from the "tie downs" that were installed at the factory. The constant pull of gravity, vibration, etc, generally causes the top or lower several header pin solder joints to crack. You can attempt to "reflow" the solder on these joints, but they don't take solder well. The absolute best course of action is to replace the header pins since in addition to cracked solder joints, the header pins themselves lose their plating, another source negative impact on reliability. 

[[File:Bally LDB MCR106.JPG|left|thumb|300px|Bally Lamp Driver board using MCR-106 SCRs]]
[[File:Stern LDB MCR106.JPG|right|thumb|300px|Stern Lamp Driver board using MCR-106 SCRs]] 
Pay close attention to the orientation of an MCR-106 when replacing one. Bally and Stern lamp driver board MCR-106s are installed facing opposite directions. T106 SCRs in a TO-202 package (the style with an extended metal tab) are easily oriented per the board silkscreen.
[[File:MCR-106OrientationBallySternLampDriverBoard.jpg|left|thumb|300px|A Bally/Stern lamp driver board, showing proper orientation of smaller MCR-106 SCRs. Note the position of the metal part of the component relative to the silkscreen.]]
 

===== Testing Lamp Driver SCRs =====
Testing a 2N5060 (also 2N5061, etc)
[[File:2N5060Test.jpg|300px|thumb|left|Testing a 2N5060]]
*Set the DMM to diode check
*Place the red lead on the center leg (the "G" leg)
*Place the black lead on the lower left lead (the "C" leg)
*A measurement between .5 and .8 should be displayed.
*Place the black lead on the center leg (the "G" leg)
*Place the red lead on the lower left lead (the "C" leg)
*A measurement between 1.4 and 1.6 should be displayed.
*Readings outside of these ranges (generally dead shorts, sometimes opens) indicate the part has failed.
 

Testing an MCR-106
[[File:MCR-106Test.jpg|300px|thumb|left|Testing an MCR-106]]
*Set the DMM to diode check
*Place the red lead on the left leg (the "G" leg)
*Place the black lead on the right lead (the "C" leg)
*A measurement between .5 and .8 should be displayed.
*Place the black lead on the left leg (the "G" leg)
*Place the red lead on the right lead (the "C" leg)
*A measurement between 1.4 and 1.6 should be displayed.
*Readings outside of these ranges (generally dead shorts, sometimes opens) indicate the part has failed.
 

===== No Controlled Lamps Working =====
If all of the controlled lamps are not working properly in the backbox, on the playfield, or both, this could be due to several reasons. Bad / marginal connectors, either on the rectifier board itself (male header pins) or the female housing that connects to it. A bad lamp bridge rectifier or blown controlled lamp fuse on the rectifier board could cause this too. The easiest way to determine if the controlled lamps are receiving the proper voltage on the playfield or backbox is to probe the bare controlled lamp bus wire (make certain to probe the controlled lamp bus and not the general illumination bus) on either or both areas with the red lead of a DMM. Then, connect the black lead of the DMM to a known, solid ground. Voltage should read approximately in the 6-8vdc range. 

Additionally, if the +5vdc is missing on the lamp driver board, no lamps will light. Only one incoming pin (pin 3) on the J4 connection (upper left connection on board) of the lamp driver board carries the +5vdc. Check for the presence of +5vdc at TP1 of the lamp driver board. 

Finally, the lack of a solid ground on the lamp driver board will also cause all lamps not to light. Most all of the different variations of the lamp driver board have the grounds secured via the screws which fasten the board to the backbox. However, the second generation of the Bally lamp driver board, the AS-2518-23, does not have these extra ground points. Since all of the lamp driver boards are interchangeable, there is the potential to have any one of the boards in the backbox. Pins 1, 2, and 11 of the J4 connection (upper left connection on board) carry the incoming grounds for the lamp driver board. The grounds originate from pins 3, 4, and 14 at connector J3 of the rectifier board.
 

===== Dim controlled lamps =====
The biggest cause of dim controlled lamps is a weak connection via the power chain's connectors. The original lamp driver bridge rectifier is slightly undersized on the rectifier board at 8 amps; either changing to #47 bulbs can alleviate some of the load placed on this bridge, or it can be upgraded to a larger capacity (25 amp or higher). Changing the header pins on the rectifier board to a 10 amp capable pin plus changing the connector pins to Trifurcon connectors will help the power chain. Application of a dielectric to prevent oxidation can help prevent new pins from prematurely wearing out, but do not apply any chemical to old, tarnished pins. 

The fuse clips on the rectifier board can get tarnished, too. Replacement with high current phosphor-bronze clips will help dimming issues. The less resistance in the power chain the better and brighter your lamps will be.

Another thing that can cause dim controlled lamps is a partially failed BR1 on the power transformer module assembly. Measure the voltage at TP1 on the power supply board--if the voltage is found to be about 2.5-2.8vdc, also measure it for AC voltage. If it reads 2.5vac on the test point, replace BR1. What happens is one of the diodes in the bridge fails open and causing an AC bias to be on the DC voltage pushing the voltage down when the AC wave goes opposite to the DC voltage.
 

===== Lamp Driver Board Attacked by Battery Corrosion =====
[[File:Lamp_board_battery_corrosion.jpg|300px|left|thumb|Lamp Board Attacked by Alkaline Corrosion]] 
[[File:Bally AS-2518-23 Bat Damage.JPG|300px|right|thumb|Lamp Board Traces Attacked by a Leaky MPU battery]]
Corrosion can drip down from the battery on the MPU board to the lamp board. Corrosion that has seeped into the SCR's can cause them to act erratic, (such as not fully turning on, or not fully turning off the controlled lamp) not switching the lamp on (even if the lamp is replaced), or a lamp being "stuck" on. If this erratic behavior is happening, inspect the lamps SCR for green/black corrosion on the legs and metal backs. Replace any components with signs of corrosion on them, even if they seem to operate normally--they will eventually fail.

Although it is not nearly as common, a leaky battery can destroy the traces on the solder side of the lamp driver board. If everything else has been checked regarding some lamps not functioning, remove the lamp driver board from the game, turn the board over, and inspect the board traces. Primarily the top horizontal traces are the most susceptible to alkali damage. Since alkali damage is very unpredictable, any of the other areas of the board may be damaged.
 

=====Testing Lamp Outputs=====
The group who designed the Bally boardset was a crafty bunch! Did you know that there is already a built in set up to test a lamp driver output? The diagnostic LED on the MPU board can double as a lamp output tester. What is needed is an alligator test lead and a component lead clipping or finishing nail. With the power off, attach one end of the alligator test lead to TP6 located on the MPU board. TP6 is located in the vicinity of of the diagnostic LED. Next, attached the other end of the test lead to the component lead clipping or finishing nail. Turn the game on, and place it into lamp test mode. Carefully place the lead with the finishing nail into one of the many lamp outputs on the lamp driver board (J1, J2, or J3). If the LED lights, the SCR and / or the header connection on the lamp driver output is good. If the LED does not light, suspect either a bad SCR, a cracked header joint, or a discontinuity between the SCR and the header pin. Pretty neat, huh?
 

===== Lamp-to-SCR (Silicon Controlled Rectifier) Mapping for Classic Stern Games =====

Click [[Lamp Transistor Mapping for Classic Stern Games|here]] to access a table showing the mapping from the Lamp Driver Board (LDB) SCRs to individual feature lamps for some classic Stern games.

 

=====Controlled Lamp Fuse Blows Instantly (With LED Adapter Add-on Boards)=====
If the fuse for the controlled lamps blows almost instantly at power up, and there are LED adapter add-on boards installed on the lamp board connectors, it's possible that there is an issue on one or more of the add-on boards. Remove each add-on board individually to isolate which one might be causing the problem. Check for solder splashes or solder bridges on the suspected board(s). Also, if the add-on boards have SIP resistor arrays/networks, it's possible one or more of these components may have failed.

===AS-2518-147 Combo Solenoid/Lamp Driver Board===
The AS-2518-147 is a combination Solenoid, Lamp, and Voltage regulator board. It is much like a AS-2518-16 or a AS-2518-22 board but includes some lamp driver circuitry.

====AS-2518-147 ground updates / bullet proofing====
The following are several ground updates to aid in reducing current stress on the connectors of the -147 combo board. Applying these ground mods should aid in reducing browned charred connectors and provide redundant grounds with the least resistance possible. 
[[File:AS-2518-147_gnd_bulletProofing-1.jpg|thumb|left|300px|AS-2518-147 overall ground-mod plan]]
 
<ol>
<li>The two 5v test points can be tied together. On the solder side of the driver board jump TP1 and J3-25 together. This eliminates a possible failure point on J3 pins 13 and 25. J3-25 is for the voltage that feeds all the +5vdc circuits in the driver section. If there's a problem in the driver section, it can be isolated by removing this jumper, and removing pin 13 or 25 from J3.
[[File:AS-2518-147_gnd_bulletProofing.jpg|thumb|left|300px|AS-2518-147 ground mods - Step 1 & 2]]</li> 
<li>The C4 and C5 capacitors need a common ground with the rest of the SDB. Jump the negative side of C4 to the above C5 negative trace and continue to the main ground trace on the edge of the board. Scrape the solder mask off the trace to get a good solder surface to solder the jumper.</li>
 
<li>Add a jumper from the large lampdriver ground trace to the main ground trace on the edge of the board. 
[[File:AS-2518-147_gnd_bulletProofing-3.jpg|thumb|left|300px|AS-2518-147 Step#3]]</li>
 
<li>Add a jumper from the solenoid driver section ground trace to the main ground trace. 
[[File:AS-2518-147_gnd_bulletProofing-4.jpg|thumb|left|300px|AS-2518-147 Step#4]]</li>
</ol>
 

===Switch problems===
[[File:Bally Stern switch matrix.png|thumb|left|300px|Bally / Stern 5 x 8 Switch Matrix]] 

Bally/Stern games use a switch matrix arranged as a 5x8 matrix for a total capability of 40 switches. Some games (Medusa, Spectrum, and others) have a sixth column of switches making a total of 48 switches in a 6x8 matrix. This guide will concentrate on the "normal" 5x8 matrix but the information applies also to the 6x8 matrix; the sixth column signal wire is merely in a different location, and for switch matrix troubleshooting purposes the information is interchangeable. 

Columns 0 and 1 are shared by the playfield and cabinet switches. Any problems with switches in these columns can be further diagnosed by disconnecting the J2 connector (playfield) or J3 connector (cabinet) to isolate the playfield, cabinet, or both from switch tests. Switch test on Bally/Stern machines is entered by pressing the self-test button on the coin door 4 or 5 times, depending on the game. The stock software in each game only shows the lowest switch number that's closed; multiple closures or an entire row/column closed will still only show the lowest switch number. (There is a special test rom available that will walk through all the closed switches one at a time).
 

Start a switch diagnostic test by removing all balls from a game and placing all drop targets into an upright position. Enter switch test and you should have a zero flashing on the match display, signifying no closed switches. Use the chart from the manual in your game if you see a closed switch to investigate why it's showing closed. 

Probable reasons for a stuck switch are:

* points or blades adjusted too closely/touching
* switch diode touching lamps/other wiring
* solder splashes/conductive debris on a switch
* shorted switch capacitor, if used 

Here is where disconnecting the playfield will help. If you disconnect the switch connector for the playfield from the MPU board (J2) and the stuck switch stays, you know the problem is not on the playfield. If the switch is in column 0 or 1, you might have a problem with the switch matrix going to the cabinet. It is common for switches on the coin door to become mangled, either being stuck closed or shorted to the coin door in some way. You can disconnect the coin door separately while in switch test to see if the switch faults clear. 

If you disconnect both J2 and J3 isolating all switches in the game from the MPU board, you should always see the flashing 0 indicating no switches closed in switch test. If you do not, there is a board fault that should be investigated and corrected. All of the signals for pulsing and reading the switch matrix originate and terminate at the U10 6821 PIA chip. As a quick test for this chip, you can swap it with the U11 PIA to see if the problem's symptoms change. If they do or the switch matrix starts to work correctly, you have a probably failed PIA chip and should replace it. Be aware that the U11 PIA chip controls the solenoids in the game, so if the U10 chip is bad in any way, you might have locked on solenoids causing more damage if your fuse doesn't blow. Before swapping the PIA chips, remove the solenoid driver board's .156 connectors to the solenoids to prevent damage. You could also just remove the J4 connector that feeds the solenoid driver board's input signals. (Lower right connector on the SDB). 

Sometimes due to wiring error a switch diode is reversed in the switch matrix, either from previous repair work, or even from the factory. When this happens, you will see the wrong switch closing. Test for this by entering switch test and activating each switch one at a time referencing the switch chart in the manual, ensuring that each switch reports the correct switch number. This means that each drop bank will need to be reset by hand after each drop target test. If the game in question has a spinner, test the spinner with the playfield down and then place a piece of paper between its switch points so testing other switches with the playfield up doesn't show a false positive on the spinner from movement. 

Momentary contact switches will sometimes have a switch capacitor installed. The purpose of this capacitor is to ensure the MPU board "sees" very quick hits to a tilt, pop bumper, sling, or standup target. Switch capacitors should not be installed on rollover, saucer, spinner, outhole, or trough switches. There are a few games that do have capacitors installed on these switches. You can cut these off safely and not worry about replacing them. 

A symptom of a failed (shorted) switch capacitor will be a stuck switch showing in the switch test, and no scoring/scoring once/multiple repeated scoring in gameplay. As a test, you can cut one leg of the capacitor off a suspect switch and see if the problem goes away. If it does, the capacitor was probably bad and you can replace it. (A 0.047 mfd 16 volt or higher non-polarized ceramic disc replacement works well.) 

Quick hits to switches that do not have capacitors installed can have a capacitor installed to improve performance, or if you have a pop or sling that activates when hit but does not score. You can add the 0.047 mfd capacitor to these switches on the two lugs that do not have the diode installed; one end of the capacitor goes to the blade lug that has one end of the diode but not the matrix wiring, and the other end of the capacitor goes to the switch lug that only has the matrix wires without the diode. If you do add a capacitor to a sling or pop bumper, be aware that it is possible for radio frequency interference from a coil's collapsing magnetic field to be picked up by the capacitor, causing the switch to activate. This is most common with flipper coils - holding a flipper up and releasing generates a short pulse of radio frequency static. 

It is good preventative maintenance on machines that have switch capacitors to methodically replace each and every one with a new one. Adding a switch capacitor to pops and slings is a good idea also as you can run a slightly larger switch gap on the activation switches, which helps to prevent switch bounce and repeat, unwanted, activations.
 

=====Leaf Switch Theory,Operation and Adjustment=====

Leaf switches in pinball games come in 4 formats: Normally Open (N.O.), Normally Closed (N.C.), Break-Make, & Make-Make, the last 2 of which are really combinations of a N.O. and/or a N.C. switch. Regardless of their function, all switches are in fact, a N.O. or N.C. type.

Leaf switches in electronic games are of 2 compositions,at least 2 bronze blades each holding a gold flashed contact or a Tungsten contact. Since gold is a very high conductor of electricity, it is used on most switches, with the exception of the flipper cabinet and End of Stroke (EOS) contacts, which are tungsten. Gold will not tarnish or turn black, but sometimes gets dirty from solenoid dust, and this may effect its conductivity. Tungsten flipper contacts must be redressed with an ignition-type flat file as used in automotive repair, as the contacts are too hard to be smoothed by sandpaper or flex file abrasive. Gold flashed contacts must NEVER be cleaned with a file or sandpaper. A business card, or thin cardboard, is all that is necessary to clean electronic gold flashed contacts. If they seems to have a foreign substance on them, a Q-Tip with a degreaser like Mean Green, or alcohol can be used and then wiped off. Contact cleaner must NOT be sprayed liberally on the switch, but can be applied with a swab.

=====Normally Open (N.O.) Switch=====
[[file:SwitchNormallyOpen.jpg|thumb|left|Normally Open Switch in resting state]][[file:GenericSchematicSwitchDiagram.jpg|thumb|right|Schematic rendering of N.O. & N.C. switches]]
This is a leaf switch that has 2 contacts that complete a circuit when pushed closed by some mechanical device. The switch re-opens when the device moves away from the moveable contact, and the springiness of the blade opens the circuit. 

=====Normally Closed (N.C.)Switch=====
[[file:SwitchNormallyClosedLabelled.jpg|thumb|left|Normally Closed (N.C.) switch in resting state with optional nylon spacer]]
This type of switch opens a circuit when a mechanical device pushes against the blade. 

=====Break-Make switch=====
[[file:SwitchMakeBreakLabelled.jpg|thumb|left|Break-Make switch in resting state]]
This switch is really a composite of a N.O. and a N.C. switch with just three blades instead of four. The movable center blade has contacts on BOTH sides. Proper adjustment insures that when a device moves the center blade towards the open contact, the CLOSED switch OPENS BEFORE the center contact touches the open switch’s contact. When the pressure is released, the center blade returns to its N.C. side and re-makes contact. This type of switch is often used on relays. A Make-Break switch is really the same, just upside-down, or in reverse, of the order of actions of a Break-Make switch. Special care should be taken with a Make-Break switch that the three blades are not at any time shorted together. This can happen often when the blade stiffener is maladjusted, and contacts the other blade of the pair. Note that this type of switch is rarely seen in Bally/Stern solid state machines. 

=====Make-Make switch=====
[[file:SwitchMakeMakeLabelled.jpg|thumb|left|Make-Make switch in resting state]]
A make-make switch is a composite switch consisting of two N.O. switches using only 3 blades. When mechanical pressure is applied to the blade, the switch “makes” or closes the circuit, and continues to move until a second switch contact is closed, tying all 3 blades together. 

=====Adjusting Switch Gaps=====
Proper switch clearance gaps are crucial for correct operation of any pinball game. Very many problems in games come down to a problem with incorrect operation of a switch. The switch blades are made up of phosphor bronze, which has high conductivity, resilience to form and excellent soldering characteristics, but has the drawback of being brittle compared to copper. Switch blades therefore, are commonly broken by the game, or careless actions by the repair person. A switch adjusting tool, purchased or homemade, is a necessity. Pliers or screwdrivers might be used in special circumstances, or in extremis, but are not best practice.

Switches in games are designed to have a degree of over-travel, which creates a wiping motion that helps clean the switch. The contacts must meet, stay together and slide across the face of the contact slightly, to be perfectly adjusted. They also must be gapped wide enough that they do not bounce, causing multiple switch closures. This problem is seen often in electronic games, when the rapid nature of the switch closures cause machine-gunning of the slingshots .

Before adjusting switches, make certain the screws holding the switch stacks are down tightly. Bakelite spacers in the switch stacks, due to excessive moisture, have occasionally shrunk by drying out, causing poor adjustment. After tightening a switch stack, be sure to recheck the gap of each switch.

To adjust a leaf switch, first make sure the switch stack of bakelite or plastic spacers and blades are tightly packed against each other by giving the 2 screws a twist of your screwdriver. As long as there is no screw movement with reasonable pressure, you can procede. Some switches have a regular nut on the backside instead of a speednut, which will require holding it as you turn.

Using your switch adjusting tool, put twisting pressure on the moveable switch blade as close to the switch stack as possible, and include the blade stiffener(if present) in the adjuster slot. Try to use as little force and change of gap as possible, and incrementally reach your gap goal. Using too much force and a back and forth gap readjustment, tends to bend and weaken the switch blade, and can make a deformed switch blade difficult to set for correct operation. This is often seen in games that have been “hacked”, and sometimes the only way to remedy the situation is to replace the entire switch, or disassemble it entirely. Cycle and recycle the mechanical device that activates the switch and observe the switch for proper gap, wiping action and release.

=====Recommended Gap Specifications=====
Kicking rubber, or slingshot switches usually have a generous gap, at least 1/16", due to the rubber ring pushing back against the switch, and a bit of trial and error will be necessary to find the ideal gap setting. Pop bumper switches and scoring “dead” bumper switches, should have a gap of 1/64" for the actuating switch under the spoon, and a 1/32" gap for the score switch when open. Flipper cabinet switch have a generous gap which can be adjusted to suit the owner of the machine to provide a good "feel". All other types of switches will probably function well with a 1/32" gap, and this would be a starting point, modifying the gap on a case by case basis.

=====The Importance of Diodes and Capacitors on Switches=====
[[file:DiodeOrientation.jpg|300px|thumb|left|Orientation of Diodes]]
[[file:Ceramic_Capacitor.jpg|300px|thumb|right| A ceramic capacitor of the type used on switch. '''NOTE:''' The number is NOT the correct value for switches. Use 0.047 mfd for replacement]] 
On all Bally and Stern solid-state (SS) pinball games, there '''MUST''' be a diode connected to each pair of switch blades. The diode’s purpose is to isolate the switch from the other switches in the switch matrix. A shorted or reversed diode will cause the MPU to read the strobe signal on the wrong return line, causing a switch read error. 

Bally (and Stern) used a matrix of 5 columns (strobes, designated 0-4) and 8 rows (returns, designated 0-7) allowing for 40 switches. Some Bally games have a sixth column allowing for 48 total switches. The sixth column games re-use a signal pin from the earlier games that was the sound board address "E" pin. Stern uses this same pin for the 7th digit enable on their displays, and never used it for their sound boards. No Stern game has a sixth column of switches. 

Bally and Stern both state 1N4004s as original, but 1N4148 diodes can be used, and in some cases, were used from the factory.
 

=====Switch Capacitor Purpose and Failure=====
[[file:BallySternSwitchClosureCapacitor.jpg|300px|thumb|left|A typical standup target with an OEM switch capacitor. The capacitor is the green disk. The other component is the isolation diode.]]
[[file:BallySwitchCapacitor.jpg|300px|thumb|right|Schematic showing capacitor connections relative to switch and switch isolation diode. Image from Bally Silverball Mania.]]
 
Capacitors are used on switches that may open and close very rapidly, to lengthen the switch pulse that the MPU can read. Not all switches will have capacitors. Standup targets, pop bumpers, slings, and tilt mechanisms are switches that benefit from a capacitor. All switches that need a quick reaction can have switch capacitors added to them (such as rollover buttons). These are ceramic non-polarized capacitors with a value of .047 or .050 uf and 16 volts or greater. A commonly available cap is the .047 uf/50 volt through Mouser P/N 140-50U5-473M-RC.

The factory-installed caps are often damaged by the high wattage industrial soldering irons used in manufacturing of the games, or they succumb to the vibration over time and no longer serve their purpose of lengthening the switch closures so that the MPU can read them. Often times, a technician will clip the cap off to diagnose a stuck switch problem and not bother to replace it. The switch will still operate in this fashion for the most part, but might not always detect rapid or brief switch closures. For more sensitive play, the capacitor should be replaced. A failing cap can also make a switch bounce, and cause machine-gunning of a slingshot or pop bumper.

Sometimes the operation of the flippers or other solenoids will cause a phantom switch close on a pop bumper or slingshot. This is due to the way the software reads the fast react switches on those mechanisms. The RF produced by the flipper coil's collapsing EMF field is picked up by the switch capacitor, causing the pop or sling to fire. In most cases, no score is added; the mechanism just operates. Keeping the leads short on the switch capacitors might reduce their tendency to pick up this stray RF in the machine.
 

=====Proper Location of Wiring, Diodes, & Capacitors=====
Color coded wiring of the playfield switches will vary by game model and manufacturer, but the following should hold true for any Bally or Stern game made from at least 1977 to 1985 . Switches may have two or three lugs, depending on function. If the switch has 3 lugs, one of them is a '''DEAD LUG''', which is electrically isolated from the other switch blades and ground. It may be that the dead lug is off to the side, or positioned the same as the other lug, and it may be difficult to visually verify which is the dead lug. The Dead Lug does not have a blade. The purpose of the dead lug is to have a isolated soldering point for the '''COLUMN''' wire(s) and the '''NON-banded''' (anode) end of the diode.
[[file:BallySwitchwithDiode.jpg|300px|thumb|left|Switch capacitor is wired as shown, some switches will not have one.]]
[[file:SternSwitchwithDiodeCapac.jpg|300px|thumb|right|A stand up target with capacitor & diode]] 
A 3 lug switch will have the following connections.

* A switch capacitor (if required) between the 2 switch blades.
* A '''ROW''' wire(s), (with a capacitor leg, if needed) to one end of either switch blade
* A '''COLUMN''' wire (usually daisy chained) plus the NON-banded end of the diode to the DEAD LUG
* The '''BANDED''' (cathode) end of the diode to the opposing switch blade, either by itself, or sharing the lug with a leg of the capacitor
 

Remember that switches are usually daisy-chained together, so except for the last switch in a group, there will be a common COLUMN wire (sometimes NOT insulated) between each switch, along with the NON-banded diode. Any break is this wire will cause all the switches below it to not function. Keep in mind that the schematics show a logic progression of switches which may or may not match the physical chain under the playfield. A failed or leaky diode can only be tested for by desoldering one end of the diode & checking with the diode test function of your multimeter. It is very little more work to just simply replace the diode with new if it is suspected. 

=====Troubleshooting multi- ball games that will not start=====
There are Bally (and some Stern) multi-ball games produced which require ALL balls to be in the correct position before a game will start. If a pinball is stuck on the playfield, missing, or the switch does not register, is broken or maladjusted, then the game will not start. The symptoms each game shows varies. After the game boots, a few insert lights may flash repeatedly, or the game will not coin up, the general illumination will not light and credits will not count down, etc. Check the chart below for specific games.

These switches can be checked in the game diagnostic switch test see if they are stuck closed, or manually operated to see if they register. Remember that only the LOWEST number closed switch will appear on the display, so if other switches are closed or have a fault, they must be cleared to check for the higher switch number.

{| class="wikitable"
|-
! Game
! # of balls
! Symptoms
! Check switch
|-align=center
| Centaur
| 5
| All zeros on; displays flicker
| #01 Ball trough 4
#02 Ball trough 5
#08 Outhole (will start with #01 or #02)
|-align=center
| Elektra
| 2
| Will not start; displays blank
| #01 Outhole
#02 Left/Right of Outhole (Starts with #01 or #02)
|-align=center
| Embryon
| 2
| Always starts
| #05 Left/Right of Outhole
#08 Outhole
|-align=center
| Fathom
| 3
| Won't start; no GI, 2 insert lights flash, displays blank
| #01 Outhole
#02 Left of Outhole 1
#03 Left of Outhole 2 (Starts with #1& 2, OR #1&3)
|-align=center
| Fireball II
| 3
| Won't start; displays blank
| #01 Outhole
#02 Left of Outhole
#03 Left of Outhole
#18 Right of Outhole
|-align=center
| Vector
| 3
| Won't start; displays normal
| #01 Left of Outhole 2
#02 Left of Outhole 2
#03 Outhole
|-align=center
| Xenon
| 2
| Won't start; displays blank
Note that game will start with only ball release 1 switch (#02) closed.
| #02 Ball release 1
#28 Ball release 2

|-align=center
| Freefall
| 3
| Won't start; displays blank; credit display shows zeroes in all 6 positions
| #04 Outhole
#35 Left of Outhole 1 (closest to outhole) or #38 Shooter Lane
#34 Left of Outhole 2
#33 Left of Outhole 3 (closest to shooter lane)

|-align=center
| Flight 2000
| 3
| Won't start; all player displays show HSTD; credit display blank
|
#33 Outhole Right
#34 Outhole Center
#35 Outhole Left
|}

*Note: Neither Freefall nor Flight 2000 will go into test mode, until switches 33 (or 38 - shooter lane with Freefall), 34, & 35 are closed.
 

=====Electrical short troubleshooting Fuse helper=====

[[file:Circuit-Breaker-Adapter.jpg|300px|thumb|left|alt=alternative text|Circuit breaker with a blown fuse soldered in position]]As an aid to finding the cause for an electrical short, you can make a circuit breaker tool to eliminate the need to constantly replace a fuse, while you investigate the cause. This could save you money in the long run. It is better to under-fuse the connection by a small amount, then to use the rated fuse rating, so a 3 amp circuit breaker could be used on a 5 amp fuse holder, or a 10 amp breaker for a 20 amp G.I. fuse holder. The very small GMA fuses (5x20mm) will probably need some kind of jumper wire setup.

*a burned out fuse of any amperage or voltage (you were saving them just for such a thing!)
*a circuit breaker of 1, 3, 5, or 10 amps, whatever amperage you require for the circuit you are troubleshooting. Buy ones like Mouser P/N 691-CMB10311C3NBA (Carling) or 655-W57-XB7A4A10-10 (Tyco).

Solder the burned out fuse to the spade terminals of the circuit breaker as shown in the photo. Alternatively, make a two wire female spade mini harness, and solder the bare wires to each ends of the bad fuse and attach the circuit breaker that way.
 

===Display problems===

====Display High Voltage Section====
'''Bally High Voltage Section Repair''' 
WARNING: This circuit uses high voltages. Don't continue, unless you are confident in your diagnostic abilities.

'''WARNING: The case of the 2N3584 (Q21) high voltage transistor is live!!! Touching the case will result in a dangerous shock!!!''' Also, some Stern solenoid driver boards use very long screws to support the protective plastic over the HV section. These screws are not isolated from the case of the 2N3584 HV transistor. The screws / nuts which support the protective plastic are live! 

If all displays are blank, your high voltage (HV) section may not be working. On the Solenoid Driver Board (SDB), use a DMM to measure volts DC on test points TP2 and TP4, to determine if this section needs repair: TP2 = 150 to 190VDC TP4 = 230VDC +/- 25VDC If TP2 is less than about 150VDC or over 200VDC, the HV section is malfunctioning. It is worth mentioning that when the source display voltage rises above the core acceptable levels, the displays will still operate. However, the increased voltage will strain the display circuitry. In turn, the displays glass life expectancy will decrease dramatically. If TP4 is 0VDC, then power is not getting from the Power Supply board, and the problem is located either on the Power Supply, or in the wiring/connectors carrying power to the SDB, so you must correct this before working on the HV section. '''Replacing the components in the HV Section''' (TP2=0VDC or 230VDC AND TP4=230VDC) If you prefer to replace only the failed components, follow page 50 of the [http://gamearchive.askey.org/Pinball/Manufacturers/Bally/pdfs/ballyfo560.pdf Bally repair manual, F.O. 560], dtd 20 June 1977.
 Since there are not that many components, it is may be less time consuming to replace all the components in the HV section. Most of these components are located between the two large heat sinks. There is a school of thought when working with high voltage regulator circuitry that dictates replacing ALL the components, as a baked, tired, component can take out new components as well. This is one area where shotgunning the section might not be a bad idea. 
[[Image:HVSection.png]]

Check the [http://pinwiki.com/wiki/index.php?title=Pinball_Parts_Suppliers Parts Suppliers] section of the wiki to find suppliers, and get the following replacement parts (1/2 watt resistors can be substituted for 1/4 watt). 

{| border="1"
| align="center" | '''Part'''
| align="center" | '''Part No.'''
| align="center" | '''Location'''
|-
| Transistor
| 2N3584,250V,2A,NPN, note: a [https://www.greatplainselectronics.com/products.asp?cat=105 BUX-85G] may be substituted  
| Q21
|-
| Transistor
| 2N3440,250V,1A,NPN
| Q22,Q23(heatsink)  
|-
| Zener diode
| 1N5275A,140V,1/2W,10% or 1N5275B,140V,1/2W,5%
| VR1
|-
| Diode
| 1N4004,400PIV,1A
| CR21
|-
| Fuse
| 3/16A,8AG
| F1(-22 only)
|-
| Resistor
| 22k Ohm,1/2W,5%
| R51
|-
| Resistor
| 1.2k Ohm,1/4W,5%
| R55
|-
| Resistor
| 82k Ohm,1/2W,5%
| R56
|-
| Resistor
| 8.2k Ohm,1/4W,5%
| R54
|-
| Resistor
| 390 Ohm,1/4W,5%
| R52
|-
| Resistor
| 100k Ohm,1W,5%,metal film
| R35
|-
| Capacitor
| 0.01 uF, 400V metal polyester
| C27,C28
|-
| Capacitor
| 150 uF, 350V (if original, replace)
| C26
|-
| Potentiometer  
| 25k Ohm, PC-mount
| RT1
|}

Possible replacement parts for the HV-section are....

Q22 and Q23 are 2N3440 and is getting harder to find.
Replacement can be a TIP50, but be aware of the correct orientation (as with all transistors).
The use of a small heatsink is advised for Q23 (like Wakefield-Vette/291-H36AB).

Q21 is a 2N3284 (very expensive and hard to find).
A good replacement is a BUX85 mounted on the original heatsink (very easy to do, cut the middle leg).

The zener diode VR1 is a 1N5275 and is getting harder to find.
A good replacement is a Z4KE140A zener diode.

The adjustment pot RT1 (25K) is an open type and cause bad adjustment.
This can/should be replaced with a Bourns 3306P-1-203 (20K).

 '''Remove and replace components'''

* Clip the old components from the board (make sure you have new ones first).
* Use one of the desoldering methods to remove solder from the holes.
* Stuff board with new components.
* Check for correct orientation on transistors, diodes and the large capacitor if you replace it.
* Leave a little space under components for air flow.
* Bend leads on components so they won't fall out when board is inverted for soldering.
* Double check that all the correct parts are in the correct places and properly oriented.
* Solder the parts to the board
* Clip excess off leads

 '''Ready to test''' Prior to powering up and testing, remove all display connectors, or test with F1 removed from the SDB. I recommend connecting your DMM with a clip lead to TP2 prior to powering the game, so you don't have to probe the HV section. Power up the machine and verify TP2 voltage is 150VDC to 190VDC. If the correct voltage is read, power down the machine and reconnect all the displays and put F1 back in. Leave your DMM connected to TP2. Power up the machine and adjust RT1 so TP2 reads about 150VDC to 160VDC. If some of the displays no longer light, then adjust the voltage up until they are all lit. New displays may require to be burned in at 190VDC for an hour or two, but then the voltage can be reduced. The lower voltage will prolong the life of the gas plasma displays. If TP2 is not correct after your repair, you will need to recheck your work. If you cannot find a problem with your repair, then I recommend you follow the troubleshooting steps on page 50 of the [http://gamearchive.askey.org/Pinball/Manufacturers/Bally/pdfs/ballyfo560.pdf Bally repair manual, F.O. 560], dtd 20 June 1977.

After you have repaired your HV section and verified that it is providing the correct voltage, the next part of the wiki will address how to correct problems with the displays.

====Repairing Bally/Stern Displays====
This page will help you repair your Bally 6- and 7-digit displays. The information is focused on the AS-2518-21 display. Since the AS-2518-15 display is interchangeable with the "-21" display, everything mentioned here will apply to both displays. Bally 7-digit displays (AS-2518-58) work the same way, they just contain additional components to support the additional digit, and lighting of commas. Some Stern DA-100 6-digit displays are very similar to the Bally versions, and the information here will also work for them. The Stern 7-digit display is slightly different, as its circuit board is physically deeper than any of the other displays and is not directly interchangeable with a Bally 7 digit display. Additionally, there are some input pin differences; however, if you have the schematic you can use the information here on the display, some transistors might be labeled differently.

First off, let's make sure your malfunctioning display is even repairable. If the glass display itself is shot, there's not much that can be done except to replace it. Here's a couple of photos of things that can go wrong with the glass display.

[[File:B-disp-d1.jpg|center]]
<center>Burn spots on the digit segments - You can't fix these but you can live with them</center> 

[[File:B-disp-n1.jpg|center]]
<center>Broken glass nipple - This display glass is ruined</center>

Then there's the circuit board. Most if not all of the components can be replaced without much effort, but if there is damage to the circuit board itself, it may be impossible, or unreliable to repair.

[[File:B-disp-b1.jpg|center]]
<center>Burn marks on the driver board</center> 

[[File:B-disp-b2.jpg|center]]
<center>Underneath - The traces are a mess</center> 

So we're assuming you have displays that do not fall into the categories above. If your problem is with the digits not being displayed properly, and it's NOT the MPU's fault, then it can be fixed, and fairly easily too!

'''FIRST THING''' - Before you go any further, there are two things you should do to ALL your displays, even if they seem to be working fine. First, reflow the solder on the joints for the header pins. On the bottom side of the circuit board, just heat each header pin solder joint with your soldering iron, then add a little fresh solder. Be careful not to create any solder bridges between adjoining pins, unless there is already one there. Next, replace the six 100K ohm 1/4 watt resistors with 1/2 watters. They are the ones with the color code brown-black-yellow, and are labeled R1, R3, R5, R7, R9 and R11. You'll find seven of them, but only the ones I just listed need to be replaced. For 7-digit displays there will be eight of them, so replace R56 too, along with the six I just mentioned. 1/4 watt is just too small for their circuits and often they are overheated which causes them to change their resistance. On the photo of the burnt circuit board up above, the area that was burnt was under 3 of these resistors.

'''SECOND THING''' - Connectors, connectors, connectors! There are lots of signals going from the MPU to each display driver, and if these signals are not making it due to bad wiring or connectors, then your displays will misbehave. Check all the display driver connectors for loose or broken wires, burnt pins, busted connectors, and replace or repair anything that looks bad. Remember that some of the signals are daisy-chained from display to display, and a bad connection at one display can effect the others "downstream". Then check the J2 connector on the MPU, since this is where all the signals come from. Next check the J3 connector on the solenoid driver board. There's a high voltage regulator used by the displays on this board, and J3 is where it gets the 230 VDC from the power supply (pins 6 & 3) and feeds the regulated 190 VDC to the displays (pin 8). Finally, check the J3 connector on the rectifier board, since this is where the high voltage comes from. Connectors are always a big pain!

[[File:B-disp-hp1.jpg|center]]
<center>Header pin solder joints - Notice the cracks around the last two pins on the right</center> 

[[File:B-disp-hp2.jpg|center]]
<center>Header pin solder joints after being re-soldered - No cracks</center> 

[[File:B-disp-r1.jpg|center]]
<center>Can you find the six 100K ohm resistors (brown-black-yellow)</center> 

[[File:B-disp-r2.jpg|center]]
<center>Here they've been replaced them with 1/2 watt resistors of the same value (100K ohms)</center> 

Now we'll look at come common problems and briefly describe the cause, but I assume you've already replaced or checked the 100K Ohm resistors and re-soldered the header pins:

=====All displays are blank=====

Most likely cause of all blank displays is a lack of high voltage. First off, check F2 on the rectifier board. It's a 3/4 Amp slow blow fuse and it's test point on the rectifier board is TP2. You should read 230 VDC at this test point. If it's OK, then check the fuse on the solenoid driver board. The high voltage regulator's output is fused and if this fuse is blown then there's probably a short somewhere on one of your displays or the wiring harness. The high voltage regulator fuse is a 3/16 Amp, but it's a bit smaller (8AG) than a standard fuse, and a hard one to find. If the fuse is not blown, then the next thing to do is verify that at least 170 VDC is making it from the regulator to the displays. Check TP2 on the solenoid driver board. It should read between 170 and 190 VDC. If it does, then the regulator is working. While you're there, if your display glasses are not new, use the small trimmer pot on near the fuse and adjust the high voltage to be 170 VDC. Older displays work just fine on 170 VDC and it's less stressful.

Next thing to check is to be sure that the 170 volts is making it to the displays. Check connector pin J3-8 on the solenoid driver board, that's where the 170 VDC leaves. Check for a good connector, and check the solder joint on the header pin. The high voltage hits all of the displays at connector J1-1 and is daisy-chained from display to display. Check these connectors and the header pins too. On at least some early Stern games like Dracula, there is a fuse for the displays mounted on the back of the backbox door, often covered by a cardboard tag. It may be that these early games came without the fuse on the SDB. Check for proper amperage and continuity on this fuse holder if no voltage is reaching the displays.

Note - If there is any light at all on the display, then it is probably repairable. Some type of Bally display glasses will have some light on them, besides the digits. If there is light anywhere on the display, then the glass is most likely OK and your problems are elsewhere.

[[File:Dispglow.jpg|center]]
<center>See how this display is glowing when it's first turned on? This indicates that the glass is good.</center>.

<center>
REMEMBER - 170 VDC WILL HURT! 
TURN YOUR MACHINE OFF IF YOU'RE GOING TO MESS WITH IT BEYOND MEASURING VOLTAGES
</center> 

If you have 170 VDC at all of the displays, and the decoder is still working, but the displays are still blank, then there is probably a problem on the MPU or the MPU connectors, such as a "stuck-on" blanking signal, etc.

If the blanking signal for the displays is stuck high or low on the MPU then the displays will remain blank. To check the blanking signal use your DMM or logic probe on MPU J1 P10. During the flash tests it should remain high (5v on DMM). Once attract mode begins it should begin pulsing (DMM will show somewhere between 1v and 4v). If the blanking signal is stuck high or low examine the blanking circuit including CR6, U14, U20. It could be the PIAs but unlikely as the power on flash test should check that the PIAs changes states. I have seen CR6 be open and cause displays to be blank.

=====A single display is blank=====

If you have one display that is blank, it could be the same problems as mentioned above (lack of 170VDC), something wrong on the circuit board, or something with the glass display itself. If you see any light glowing at all on the display, then the glass is most likely good and your problem is elsewhere.

The main cause of a single display being blank is a bad glass. If the glass is good, then your problem is most likely a bad 4543 decoder IC. The decoder on the display driver board is used to decode the digit data from the MPU into signals that light the proper displays. If the decoder is blown, then this could cause the display to be blank. A quick check with a logic probe will help you decide if the decoder is function properly.

Sometimes the solder joints on the display glass needs are cracked and need to be reflowed. Depending on which solder joints are bad, this could cause the display to be blank.

If you can verify there is 170VDc, and the decoder is working, then it may be just a bad display. If there is some light anywhere, then it's probably good. If not, it may or may not be good. A totally blank display is the hardest thing to fix. If everything looks good, but the display is completely blank, then you may just have to chalk it up as a bad display glass. Unfortunately they can not be repaired.

=====All displays are missing the same digit=====

If all the displays have the same digit out, then the problem is most likely caused by a bad connector at the MPU. The MPU daisy-chains the digit enable signal to all the displays, and if the same digit is out on all, then it's either an amazing thing that they all have a problem w/ the same digit, or the digit enable signal is not present. Check the connectors on the MPU and all of the displays. If all seem well, then one-by-one, disconnect each display and see if the problem goes away. If it does, then there's a short or a bad connector problem on the board you just removed. Be sure to turn the power off between swap-outs, and wait 10 seconds for the high voltage filter capacitor to discharge before you remove any connectors.

=====The Same Number is Displayed Multiple Times During Display Test=====
If one or all of the displays show the same number more than once during display test, (ie. instead of 0,1,2,3,4,5,6,7,8,9 being displayed, 0,0,2,2,4,4,6,6,8,8 or similar is displayed), the 4543 decoder chip on one of the displays is probably bad. To test this, turn the power off, and disconnect all displays but one. Continuing performing this procede until the suspect display is found. DO NOT REMOVE THE CONNECTOR FROM THE DISPLAY WITH THE POWER ON. This will result in damage to the MPU board, the display, or both.

=====One display is missing the same segments on all the digits=====

Each display has it's own decoder chip, which takes four inputs from the MPU and outputs seven signals to light the seven segments of a digit. If you're having problems with one or more segments on all the digits, then it's either the segment driver transistor or the decoder itself. I'm sure there's a way to test the transistor but I just go ahead and install a new one. If that doesn't fix it, then replacing the decoder will. I've not had a segment problem that was not fixed by replacing both segment drivers and decoders (other than MPU problems). Be sure to orient the transistor and/or IC in the proper position. You'll notice a flat side on the transistor and a small notch on one end of the decoder IC. Be sure they line up just like the one you removed, and that the wires of the transistor go into the same holes that the old one came out of. Also, if you're replacing the IC, use a socket, so it'll be easier to replace it next time. Here's a handy chart that shows which segment driver transistor drives which segment, and another diagram of how the segments are labeled. Just find the segment that's giving you trouble on the chart, then look up it's corresponding driver transistor. Then find this transistor on the circuit board and replace it.

[[File:B-decoder-chart.jpg|center]]

=====One display has a segment locked on all digits=====

The segment driver has failed. When this issue is seen a lot of times the display will be blank except for the locked on segment. Replace the segment driver (see chart above) and then retest the display. If the display now works except for the segment drive you replaced is now turned off then replace the decoder chip. When the segment driver locks on it usually blows out that segment on the decoder chip.

=====One digit is out on one of the displays=====

If there is a single digit out, then it's probably the the level shifter and digit driver transistors for that digit. Just to be sure, check the connector on the display at pins J1-4 through J1-9. These are the connectors that supply the digit-enable signals from the MPU. The problem may be that the display driver is not getting the enable signal from the MPU. If it is, then just replace the two transistors and you should be back in business. Here's a handy chart that shows you which level shifter and digit driver are associated with each digit. The transistor labels should be printed on the circuit board, or look at the diagram below. Just look at this chart, find the digit that's blank, and then locate the two transistors listed for that digit. Find them on the circuit board and replace them.

{| class="wikitable sortable"
|-
!Digit
!Level Shifter (MPS-A42)
!Digit Driver (2N5401)
|-
|1's
|Q1
|Q7

|-
|10's
|Q2
|Q8

|-
|100's
|Q3
|Q9

|-
|1,000's
|Q4
|Q10

|-
|10,000's
|Q5
|Q11

|-
|100,000's
|Q6
|Q12

|-
|1,000,000's
|Q20
|Q21

|}

=====One display is missing a digit or segment=====
If one digit or segment is out on a display, but segment drivers, transistors, and the IC have all been replaced, be sure to check the resistors for damage and that they are giving the correct resistance.

If all else fails, try gently flexing or wiggling the glass a little bit to see if the segment or digit lights up. If that's the case, there may be an issue with one of the finger leads on the glass.

In the best case scenario, there is [[#Display(s) flicker|merely a cracked solder joint on a finger lead]] where it is soldered to the PCB.

Sometimes, the finger lead has been stressed and will snap on the top side of the PCB above the solder joint. A jumper wire might be able to address this.

In the worst case scenario, the finger lead has separated from the contact pad inside the glass. Unfortunately, there is not currently a recommended approach for performing a repair.

One suggestion included using a dremmel tool to drill out the glass to expose the finger contact, and then solder a jumper wire to it (note that solder might or might not stick to the contact, and instead, conductive glue or silver epoxy may need to be used, similar how a repair for a broken lead wire in a DMD display on newer games is performed).

On 6-digit glass, all the contacts are on the same side of the slot for the finger leads, and if the front side of the glass is drilled out, all the contacts accessible. On 7-digit glass, the contacts alternate which side of the slot inside the glass that they are adhered to, so only about half of these contacts are accessible from the front of the glass--some are adhered to that same front side that needs to be drilled out. So, it might not be possible to access all the contacts on a 7-digit glass.

[[file:bally-7-digit-glass-finger-contacts.jpg|left|thumb|300px|7-digit glass with alternating contact pads]] 

=====One digit is very bright, and the rest are out=====

If you have one digit that's very bright and all the rest are out, simply replace the digit driver and level shifter transistors for that digit. Turns out sometimes a short transistor will draw so much current that there's not enough left to drive the remaining digits, and so they all go blank. Just use the chart above to determine which transistors to replace.

=====Display(s) flicker=====
[[Image:CrackedHeadersAnnotated.jpg|300px|thumb|left|Closeup of Cracked Header Pins on a Bally/Stern Display Module. These cracks caused rapid "flicker" of the display.]]
[[Image:ColdSolderJoint.jpg|300px|thumb|right|Magnified view of a cold solder joint on a Bally/Stern Display Module.]] 
This is almost always caused by fractured solder joints at the header pins. If you have already re-flowed the solder, double check them, then look for other broken solder joints and check all connectors for tight fits. Something is loose that's making them flicker. This "flicker" is about the fastest flicker you can imagine.

Another cause of flickering or strobing digits is a faulty decoder IC. If your digits are flickering or "wavy", try replacing the decoder IC.

[[File:YT.png]] Here is a link to a [http://www.youtube.com/watch?v=KCsisnUJWoY video] of a display board with a faulty 4543 decoder IC. Keep in mind that failed / failing decoder chips do emit symptoms other than what is seen in the video. Please see the other symptoms discussed above in this section.

Yet another cause of flicker is low HV or a shorted display that drags down the HV.

'''Centaur Specific'''

Centaur, being a multiball game, requires that all 5 balls be in the trough. This means that switch 2, "5th Ball Trough", must be seen by the MPU as being closed. Unless the MPU sees switch 2 as closed, the displays will flicker.
 

=====Conclusion=====

That covers the most common display problems. If the pinball machine manual is not available, click on any of the thumbnails below for a large picture of the component layout of the all three boards. The 100K Ohm resistors are the ones colored brown-black-yellow.
 

===Sound problems===
Regardless of the sound board, it is always best to first remove the existing solder from the header pins, and reflow new solder onto them. Due to vibration over time, the header pin connections can end up with cracked solder joints, which is very common on the Bally sound boards. The next order of business would to replace the volume pot and the secondary pot, if one is used on the board. The original, factory pots used were not sealed, therefore, dirt and other contaminants can cause the pot to have dead spots or fail in general. Once these two things are done initially, troubleshooting the sound board, if it's still not working will be a lot easier. 

If the board is still not working after the above recommended procedures, the next thing would be to check all of the voltages used on the board. See the [http://pinwiki.com/wiki/index.php?title=Bally/Stern#Sound_Test_Point_Values Sound Test Point Value] section for the test point voltage values for each particular sound board. 

If all of the voltages check out, it's time to move onto the appropriate sound board troubleshooting section below.
 
==== AS-2518-32 & AS-2518-50 Sound Board Troubleshooting====
[[File:Bally -32 Cracked Headers.JPG|300px|thumb|left|Typical cracked solder joints on the header pins of a -32 board]]
[[File:BallySoundFracturedHeaders.jpg|300px|thumb|right|Close-up of severely cracked solder joints on the header pins of a -32 board]] 
The first course of action, before performing any troubleshooting to the board, is to inspect the header pin connections on the reverse side of the board. It is common to have cracked joints, where the header pins are soldered to the board. If cracked solder joints are apparent, heat and remove the old solder, and reflow new solder onto the connections. This will ensure that incoming voltages, ground and sound signals are solid on the board itself. Inspection of the connectors located in the female housing, which connects to the header pins, is equally a good idea. Replace any connectors that appear to be marginal. Molex Trifurcon crimp connectors are recommended as replacements.
 

[[File:Bally -32 Sound Min Components.JPG|300px|thumb|left|Minimal component replacement for -32 and -50 boards]] 
There are several components which should be replaced on these boards to speed the troubleshooting process. Both the -32 and -50 sound boards use at least two 10Kohm pots. One pot controls overall volume. The other pot controls sound sustain (or tone duration). Both pots should be replaced to eliminate them as possible culprits and improve reliability. Likewise, a 1N4004 diode (CR3) is used on the board at the incoming +43vdc. Should this diode fail, it can cause the CPU to halt at 6 flashes at boot up. 

Capacitor kits for both the [http://www.greatplainselectronics.com/proddetail.asp?prod=BALLY-S32E-KIT -32] and [http://www.greatplainselectronics.com/proddetail.asp?prod=BALLY-S50E-KIT -50] boards are available from GPE. Although it is not always necessary to replace the caps on these boards, it is recommended. 

Should the 86L93 (U11) chip fail, the [http://www.greatplainselectronics.com/search.asp?pg=1&stext=74LS93&sprice=&stype=&scat= 74LS93] is a viable substitute.

There is a great [http://www.pinball4you.ch/okaegi/rep_soundold.html repair website with step-by-step checkpoints, created by Oliver Okaegi]. You do need to have scope to see the signals. 

'''Voltage Test Points''' 
The following DC voltages are required and may be measured on the sound board:

*TP1 = 5v,
*TP3 = 12v,
*TP4 = 43v.

If any voltages are missing, check the connectors. Specifically check the integrity of the header pins.

'''12v regulator section:''' 
Check for 67 volts on the positive side of C17. If missing replace CR3. If positive side of C17 is the same as TP4(43v) replace C17 and CR3.

If 12v is too high, check Q1, R22, CR4, and C18.

'''Clock Generator:''' 
U1(4049) can fail. Check for about 2.5vdc where R3 and R5 meet. (On my functioning -50 board, I see .8vdc at this point) If voltage incorrect replace U1 which is a 4049 hex inverter. If still incorrect suspect U4 which is a 4526B programmable 4 bit counter. The 4526 can be purchased from vendors such as [http://www.mouser.com/ProductDetail/ON-Semiconductor/MC14526BCPG/?qs=sGAEpiMZZMtsbn1GaJyslzVwwLLwbjUEVTxCaemDWNo%3d Mouser] or [http://www.digikey.com/product-detail/en/MC14526BCPG/MC14526BCPGOS-ND/1478908?WT.z_cid=ref_octopart_dkc_buynow&cur=USD Digi-Key].

'''Amplification / no sound issues:''' 
First, make certain that the cabinet speaker is present, connected, and functioning. If an audible hum is heard from the speaker, then the amp is working. Next, check both pots. It is best to replace them if they are the originals (typically blue or black thumb wheel pots). Measuring across the two outer legs of the pot is the total resistance (10k). Measuring from the middle leg gives a resistance with regards to how the pot is adjusted (a value from 0 ohms to 10 kohms depending on the pot's position).

To check the amplifier at U9 (LM741), look for about 2vdc at U9 pin 2. (On my functioning -50 board, I see 6vdc at U9 pin 2. Before replacement, 12vdc was seen when it wasn't functioning.) If voltage is missing, replace the amp. Note that the LM741 must be a specific part; part number LM741CN. Other LM741 parts may work, but often the volume is not amplified, resulting in only low volume output. A modification to the -32 sound board can be made to overcome this issue. The modification adds three components to the -32 sound board that Bally added to the -50 sound board during production. A discussion of this mod can be found [https://pinside.com/pinball/forum/topic/volume-problem-after-replacing-u9-on-bally-32-sound-board here].

 

==== AS-2518-51 Sound Board Troubleshooting====
Note: The following games do not make sound when the diagnostic button is pressed on the board:
*Nitro Groundshaker
*Future Spa
*Space Invaders
*Xenon
*Speakeasy

Sound Board References: 
[[image:YT.png]] [https://www.youtube.com/shorts/lhaC5cxpoDY Future Spa] 
[[image:YT.png]] [https://www.youtube.com/shorts/iiU78w-oZ3w Mystic] 
[[image:YT.png]] [https://www.youtube.com/shorts/B4YmV-gqujw Skateball] 

[[File:As-2518-51.jpg| 300px| left |thumb | Bally AS-2518-51 Sound Board]]
[[File:Bally-51SoundBoard.jpg| 300px| right|thumb | Bally AS-2518-51 Sound Board Schematics]]
Although the AS-2518-51 sound board uses a 6800 family of microprocessor, the lack of an on-board, boot status LED makes this board more difficult to troubleshoot than the Squawk and Talk sound board. On the plus side, this sound board utilizes some of the same ICs, which are commonly found on the game's MPU board. Fortunately, all of the larger ICs on this board are socketed. Like the OEM sockets on the MPU board, the sockets used on this board are subject to failure. Replacement with new, high quality sockets is advised to eliminate this possible cause of failure and for long term reliability. 

The first course of action, before performing any troubleshooting to the board, is to inspect the header pin connections on the reverse side of the board. It is common to have cracked solder joints, where the header pins are soldered to the board. If cracked solder joints are apparent, heat and remove the old solder, and reflow new solder onto the connections. This will ensure that incoming voltages, ground and sound select signals are solid on the board itself. Inspection of the connectors located in the female housing, which connects to the header pins, is equally a good idea. Replace any connectors that appear to be marginal. Molex Trifurcon crimp connectors are recommended as replacements.
 

Like all sound boards of this age, the capacitors are likely to have dried out and are no longer doing their job. Capacitor kits for this board can be acquired at [http://www.greatplainselectronics.com/proddetail.asp?prod=BALLY-S51E-KIT Great Plains Electronics]. Installing a cap kit brings most dead boards back to life. 

If the board is producing no sound at all, start by checking the volume adjustment pot. When turning the pot, the volume of the hum should get quieter and louder. If this is not heard, the amp/pot may be bad. If the hum volume changes, it is likely that the amp and pot are working. However, the 1K volume adjustment pot is 30+ years old, and was an "open" design. It is recommended that this pot be replaced with a quality sealed 1K ohm pot, whether or not the original pot tests good. 

Check the power at the board with a DMM. TP3 is ground. TP2 and TP1 should measure 5VDC and 12VDC respectively. These are nominal values. Minor variation from these values is acceptable. 

Next, it is time to check the large ICs on the board itself. First, swap the 6821 PIA at U2 on the sound board with either U10 or U11 on the MPU, and retest. Second, swap the 6810 RAM at U10 on the sound board with the 6810 at U7 on the MPU and retest. 

If the problem persists, swap in a known good sound ROM at U4 and retest. Pay particular attention to the legs of U4, if it is a factory masked ROM. It is common for the legs of these masked ROMs to oxidize or tarnish, just like the masked ROMs used on the MPU board. Hence, the legs can be fragile, and are easily broken. Likewise, tarnished legs on U4 could potentially be responsible for the lack of sound. Evidence of oxidation is visible in the form of blackened chip legs (silver oxide). The oxidation can be removed in several ways. The most common methods are gently using a pencil eraser over the legs, or soaking the chip legs in Tarn-X, followed by rinsing the legs in clean water, and allowing to dry before re-installation. As mentioned previously, if the legs are oxidized, use extreme caution when removing the chip from its socket and removing the oxidation. 

If a known good 6808 (a 6802 can be used when jumper A is installed, and jumper B removed) is available, swap it for the processor at U3 and retest. 

If a known good AY-3-8910 is available, swap it for the sound IC at U1 and retest. The AY-3-8910 produces '''ALL''' of the sound from this board. If sounds continue to play after the completion of a game, this can be caused by a failed AY-3-8910. 

The sound interrupt signal and the sound select signal IC should also be checked. Connect a logic probe to the board; red lead at TP2 (+5VDC), black lead at TP3 (GND). With J1 connected to the game, place the probe on pin 40 of the PIA at U2. The signal should start high. When the game's MPU completes it's 7th flash, it will command the sound board to make the boot sound. At this point, pin 40 will go low for a split second, then return to high. If all goes well, consider the sound interrupt signal good. 

Test the function of the sound select inverter 4049 at U5. U5 is a simple hex inverter. In attract mode, with no sounds being produced, pin 3 should be low, pin 2 should be high. Pins 5/4, 7/6, and 14/15 should test the same as pins 3/2 respectively. Pins 9 and 11 may not be connected on the game. If so, there will be no signal on those pins. However, their "inverted" signals at pins 10 and 12 should be high. Pins 13 and 16 are not connected. 

The 6808 / 6802, AY-3-8910, and 6821 ICs require a reset signal which is created via a 1N4004, 1Mohm resistor, and NAND gates at U6 (4011). Test the 1N4004 diode via normal diode test. U6 can be tested with a logic probe similarly to U5. With a logic probe on pin 40 of the 6808 processor, at power on the signal will remain low for a split second and then go high. 

The external clock signal can be probed at pin 37 of the 6808. It should pulse steadily. If not, suspect the crystal oscillator.

Although U7 is specified as a 555 timer IC on the schematics, it is not listed on the BOM, and was not installed on this board. Nor were any of the several discrete components to the right of the U7 solder pads (i.e. C10, C11, R11, R12).

Loud Hum 
While it might seem OK to connect analog and digital ground for testing on the bench, this causes the board to produce a loud hum. Pin 15 (analog ground) must be grounded separately from pins 6 and 14 (digital ground).
 

====Sounds Plus Sound Board Troubleshooting====
This is a stub.
 
====Vocalizer Speech Board Troubleshooting====
There is a [https://pinside.com/pinball/forum/topic/xenon-vocalizer-eprom-repair-vids-guide repair guide on pinside] for addressing ROM issues and replacing the original ROMs with EPROMS.
 

====Squawk & Talk Sound Board Troubleshooting====
===== Sound Test Reference =====

The following video links demonstrate properly operating Squawk & Talk sound boards.

[[image:YT.png]] Place Holder.

=====Basic Information=====
[[File:SquawkAndTalkJumperAndTestPointLocations.jpg|300px|left|thumb|Bally Squawk & Talk Jumper Locations. Note that the -61B revision of the board contains a jumper FF located within the stack of resistors below the AD558. Neither the -61 or the -61a revision has this jumper.]] 

The image at left indicates jumper and test point locations.
Jumper settings for various game and ROM combinations can be found [[Bally/Stern#Squawk_.26_Talk_Jumper_Settings | here]].
 

Test Point Number and Functions

{| class="wikitable"
!   TP   
! Function 
|-
| <center>1</center> ||  Ground 
|-
| <center>2</center> ||  +5VDC 
|-
| <center>3</center> ||  +11.5VDC 
|-
| <center>4</center> ||  -5VDC 
|-
| <center>5</center> ||  Speech Volume Control Voltage 
|-
| <center>6</center> ||  Sound Volume Control Voltage 
|-
| <center>7</center> ||  AY-3-8912 Output 
|-
| <center>8</center> ||  E (external clock provided by the 6808/6802) 
|-
| <center>9</center> ||  TMS5200 Output 
|-
| <center>10</center> ||  VMA (valid memory address) 
|-
| <center>11</center> ||  TMS5200 clock (not used. Would clock the TMS6100) 
|-
| <center>12</center> ||  Reset 
|}
Source: Bally AS-2518-61 Squawk and Talk Schematics.
 

Integrated Circuits used by the Squawk & Talk sound board.

*U1 - Motorola 6802 or 6808 8-bit microprocessor
*U2 - ROM
*U3 - ROM
*U4 - ROM
*U5 - ROM
*U6 - 6810 RAM (only used if a 6808 microprocessor is used. If a 6802 is used, the socket is empty)
*U7 - 6821 PIA for controlling the speech IC - TMS5200 VSP and TMS6100 VSM phrase ROM
*U8 - TMS 5200 VSP Speech IC (does not occupy address space)
*U9 - TMS6100 VSM 16k byte Phrase ROM containing speech data (never populated). Again, it does not occupy address space
*U10- AD558 DAC for converting digital wave data stored in the ROMs to audio
*U11- 6821 PIA for controlling the AY-3-8912 sound IC and the test LED
*U12- General Instruments AY-3-8912 PSG (Programmable Sound Generator) IC, which again, does not occupy address space

=====The Very Easy Simple Fix aka the General Illumination is Out=====
If for some reason, the general illumination is not lit on the playfield or backbox of the game, suspect a blown 20A fast blow F5 fuse on the power module or possibly fuse clips in poor condition. One leg of the general illumination is fed to the Squawk & Talk, and it becomes the -5VDC, which is one of the voltages needed to power the TMS5200 speech chip. Without the general illumination, the Squawk & Talk board will not successfully boot!
 

=====General Troubleshooting=====
Troubleshooting the Bally Squawk & Talk board is much simpler than it might first seem. First, the board provides "blink codes" at power up, similar to the way that Bally MPUs do. These codes help isolate the failed component.

[[File:TMS5200LegTarnish.jpg|300px|right|thumb|The legs of the TMS5200 Speech Processor chip almost always tarnish over time, perhaps due to the legs and the socket being constructed from dissimilar metals. Replacing the socket and removing the tarnish is always advisable. Be cautious as the legs sometimes become fragile.]]
The Squawk & Talk sound board is itself a single board computer. At it's heart is the 6808 processor with external RAM, or the 6802 processor with integrated RAM. Two 6821 PIAs are used to interface the processor to peripheral devices. The 6821 at U11 provides an interface to the AY-3-8912 (if used) or the U16, a 4049 inverter where sound selects are sent from the MPU. The 6821 at U7 provides the interface to the TMS5200 Speech Processor.

Up to 4 ROMs can populate the board with either 2716, 2532, or 2732 ROMs.

An AD558 DAC (digital to analog converter) is used to make traditional pinball beeps, squeeks, and tones.

A TMS5200 Speech Processor is used to convert digitally stored (and compressed) sound information in the ROMs to analog "speech" (which can also be sounds).

An AY-3-8912 Sound Generator is sometimes populated at U12 to produce simple tone sounds.

Two LM3900 operational amplifiers (op amps) amplify the analog signals from both the speech and the sound lanes before they are summed and provided to the main amplifier.

At TDA2002 amplifier is used at the final stage of amplification. A TDA2003 may be used to replace this amp.

Variable 1KOhm pots at R69 and R70 control speech and sound volumes independently (respectively).

Provisions are available for controlling volume via external pots by connecting to J2, pins 5 and 6.
 

[[File:SandTRegulator.jpg|300px|left|thumb|The 5V regulator sometimes develops cold solder joints. Without 5VDC, the diagnostic LED won't blink at all.]]
 Techniques 
Power the board on the bench. 
Recognize blink codes. 
Check voltage regulation circuits. 
Use the "self-test" button. 
Isolate the problem to the "digital" section or the "analog" section. 
Use a logic probe to "listen" at points in the analog section.
 

[[File:PoweringSquawkAndTalkOnTheBenchAnnotated.jpg|300px|thumb|left|Powering the Bally Squawk & Talk Sound Board on the Bench.]] 
Powering the board on the bench 
To power the board on the bench, use an old computer power supply that is capable of providing -5VDC and +12VDC.
*Connect +12VDC to J1 pin 10. The board will use the +12VDC and will also regulate it down to +5VDC
*Connect -5VDC to TP4
*Connect the power supply ground to TP1
Double check all of your connections before applying power. 

If the board is a -61b revision, as used in Centaur for instance, install a temporary jumper at location "FF". This allows operation without attaching the "Say it again" board.
 

Blink Codes 
An overview of "Blink Codes" follows. 
For a more in depth discussion of these blink codes, see the excellent information developed by Clive Jones, [http://webpages.charter.net/coinopcauldron/squalkart.html here]. 

{| class="wikitable"
!   Blink   
! Meaning 
|-
|  First "flicker"  ||  The processor has found the program code in ROM, and has begun to configure the board. 
|-
|  First Blink  ||  The 128 bytes of system RAM (either within the 6802, or external in the 6810 if configured with a 6808) have tested good. 
|-
|  Second Blink  ||  The 6821 PIA at U7 (which controls speech) has passed test. 
|-
|  Third Blink  ||  The 6821 PIA at U11 (which interfaces with the AY-3-8912 and fields sound codes from the MPU) has passed test. 
|-
|  Fourth Blink  ||  Communication with the AY-3-8912 has passed. Note that the PIA at U11 must be communicating correctly with the AY-3-8912 for this test to pass. If there is no fourth blink, first swap a known good 6821 into U11. 
|-
|  Fifth Blink  ||  The TMS5200 Speech Chip has passed testing. 
|}

Pressing the red diagnostic button on the Squawk and Talk board, should cause the board to play various speech calls (games like Medusa seem to go on forever, Spectrum plays only a short speech call) followed by a sound call. The speech is generated by the TMS5200. The lone sound call at the end of this test is generated by either the AY-3-8912 (as in EBD, for instance) or the AD558 digital-to-analog converter. At the conclusion of playing these various speech calls and sound call, the board then reboots itself, and the same blink codes should be seen.

Basic maintenance actions 
There are 5 actions you can take to ease the process of debugging the S&T board (priority order):
#Ensure the correct jumpers are installed, matching the game and sound ROM type
#Replace ALL electrolytic capacitors on the board
#Replace both 1KOhm pots (one for speech, one for sound)
#Replace IC sockets (empty sockets don't need to be replaced obviously, ScanBe sockets must go, RU sockets can remain)
#Replace .156 male headers at J1 and J2 (at a minimum, reflow the solder joints)

Completing each of the above items usually results in a working Squawk & Talk board.

Capacitor list and recommended modern replacements 
C1 - Axial Electrolytic 47uF, 25 Volt 
C14 - Axial Electrolytic 4700uF, 25 Volt 
C15 - Axial Electrolytic 10uF, 50 Volt 
C19, C24, C25, C28, C31, C34 and C42 (7 capacitors) - Axial Electrolytic 1uF, 50 Volt 
C27 - Axial Electrolytic 1000uF, 25 Volt 
C29 - Axial Electrolytic 470uF, 16 Volt 
C36 and C43 (2 capacitors) - Axial Electrolytic 2.2uF, 50 Volt 
C37 and C38 (2 capacitors) - Axial Electrolytic 330uF, 50 Volt 
 

=====Locked on LED on Squawk & Talk Sound Board (Minimizing Chips Needed to Boot)=====
As mentioned above, there are LED blink codes used when passing specific chip tests during the boot up process. However, the Squawk & Talk sound board is similar to the Bally -17 / -35 MPUs, and it too can end up with the dreaded locked on LED. The end result is the board not proceeding through the boot process. On the plus side, battery damage is far less of an issue for the S&T board versus the MPU board. 

For starters, it would be best to reduce the amount of chips installed on the S&T board to try to get it to boot. At a minimum, only the following. factory socketed chips are needed to achieve some "signs of life" out of the board. Only having these chips installed will not allow the board to complete its boot up process. However, chips can be installed in a systematic method to get the board to successfully boot. 

'''Flicker''' 
To achieve a flicker from the diagnostic LED on the board, the U1 CPU (either a 6808 or 6802), the U11 PIA (this 6820 or 6821 activates the LED), and the U5 ROM (boot up instructions are located on U5). Make certain that the [[Bally/Stern#Squawk_.26_Talk_Jumper_Settings | jumper settings]] are correct for U1 and U5. Keep in mind that a known working 6820 / 6821 can be acquired from a working Bally MPU board. Likewise, the 6820 / 6821 from the S&T board can be installed in a known working MPU board to test. 

If the board still has a locked on LED, the following things should be investigated: 
*Make sure that the reset on the CPU chip starts low briefly and then goes high. With a logic probe, check pin 40 of U1. If the reset does not go high, suspect C1 (47uF 25v), CR1 (1N4148), R1 (27K 1/4w), U15 (74LS14), or possibly U17 (74LS155).
*Next, check for an active clock signal. With a logic probe, check pins 38 and 39 of U1. Both legs of the CPU should be pulsing (some logic probes may not pulse, the clock voltage is rather low). These legs go directly to the clock crystal (Y1 - 3.58 mHz). If these signals are not pulsing, suspect the crystal or its associated capacitors, C3 and C4 (both are 27pF caps). It is fairly common for the crystals to fail on these boards.
*Make sure that the transistor (Q1 - 2N3904 or 2N4401) which drives the LED is functioning.
*Again, check that the correct jumpers are installed. If the incorrect jumpers are installed for U1 / U6 (K or L) or U5 (Y, Z, AA, BB), the LED will remain solidly lit.
*Inspect the chip sockets. Although the chip sockets used on the S&T are of decent quality, they have aged and can fail. If a chip can be removed from its socket by merely pulling it out with one's fingers, the socket is bad and needs replaced.
*Lastly, make certain that U1, U5, and U11 are good. 

'''1st Flash''' 
Once a flicker is achieved, the road to recovery is much smoother. Install the U6 RAM (6810), if using a 6808 CPU at U1. A good 6810 can be pulled from a working MPU board. Likewise, the 6810 on the S&T board can be tested in a known working MPU board. If using a 6802, the 6810 is not needed. Also, the 1st flash will be automatic with just the 6802 installed, as long as jumper K is installed. Having U6 installed with a 6802 CPU chip installed does not hurt anything, and either the L or K jumper can be installed, as long as the 6810 is good. 

'''2nd Flash''' 
Install the U7 PIA (6820 / 6821). Again, a good PIA can be acquired from a known working MPU board. 

'''3rd Flash''' 
Since the U11 PIA (6820 / 6821) is already installed, the 3rd flash should appear, if this chip is good. 

'''4th Flash''' 
Install the U12 sound generator chip (AY-3-8912), if it is used. If the U12 chip is not used, the 5 EE jumpers must be installed.

'''5th Flash''' 
Install the U8 speech generator chip (TMS5200). It is very common for the speech chips to have tarnished legs. To remove the tarnish, a pencil eraser can be used, if used very gently and cautiously. Tarn-X is a much better product to remove the tarnish. 

'''Closing Notes''' 
Once the board boots, a single sound is typically heard. A single sound is typically heard when the test button is pressed too. At this point, the remaining sound ROM(s) can be installed. Again, make certain the ROMs have the appropriate jumpers installed. If the incorrect jumpers are installed, the LED will remain solidly lit. 

The U10 DAC (AD558) does not need to be installed at any point during the above process to get the board to successfully boot. However, U10 must be installed to generate all of the sounds associated with any particular game.
 

=====Speech is Heard but No Sounds=====
If the board is booting, but only speech can be heard, and the above "Basic maintenance actions" were not performed, there are several things which can make this occur. The first would be to make certain the sound potentiometer is functioning. Dead spots and / or a completely failed pot can cause the sounds not to be heard. Secondly, replace the electrolytic capacitors. This should be done in most cases anyhow. If after replacing the capacitors did not cause the board to produce sounds, there are a couple of other things to look at. 

A starting point would be to make certain that the wiring harness is intact between the MPU and S&T boards. To test this, place an alligator clip on each of the resistors located on the bottom left of the board. The sound signals come into these resistors first. Next, take the alligator test lead, and attach it to one side of a DMM. Put the DMM in contintuity mode. Place the other lead of the DMM on the resistor leg of R97-R100 and R106 located on the MPU board. Repeat the steps for each sound signal. Performing a continuity test in this manner (from board to board) narrows down bad connectors and / or header pins.

If the harness is all right, make certain the U16 (4049) inverter on the S&T has not failed. 
 

=====Pitch of Speech is too high/low=====
[[File:SAndTR9.jpg|300px|left|thumb|R9, shown in-situ, on the Bally Squawk and Talk board. Note that this 120K resistor is not the OEM resistor and has been substituted.]]
The "pitch" of Squawk and Talk speech can be adjusted by varying the value of resistor R9, pictured in-situ at left. Typically, in almost every instance, the factory value of the resistor is 130K 1/4W. However, Flash Gordon uses a 240K resistor.

[[File:YT.png]] If changing out the typical 130K resistor, using a higher resistance (140K) resistor will lower the pitch; a lower resistance resistor (100K) will increase the pitch. Example videos of both higher and lower pitch speech using these resistor values can be found here ([https://www.youtube.com/watch?v=BFeL47DoSJQ high], [https://www.youtube.com/watch?v=nef-wOmuduk low])
 

=====Speech is Garbled, Clipped, or Unintelligible=====
The TMS5200 is practically unobtainable as of July, 2020. At times, a TMS5220 will be substituted to replace a failed TMS5200. The TMS5220 will create voice, but the audio will be garbled and somewhat unintelligible.

[[File:YT.png]] A video comparing "Flash Gordon" voice/sound diagnostics with a TMS5200 and a TMS5220 can be found [https://www.youtube.com/watch?v=Mml7fH6QYFw here].
 

=====Hum In Voice Circuit=====
If the "hum" present during voice calls is noticeably louder than the "hum" present during sound calls, this can be caused by excessive AC "noise" in the -5VDC generation circuit.

Isolating the hum to the voice or sound circuit is as simple as adjusting the trim pots clockwise to reduce the volume of that channel. The hum can be caused by failed C37 or C38 (both 330uf/50V axial caps). However, if the board has been recapped, which is always advisable for this board, and the hum is still present, suspect the 7905 negative 5VDC regulator.
 

====Say It Again Reverb Board Troubleshooting====

=====Say It Again Reverb Board Basic Information=====

{| class="wikitable"
|+Test Point Number and Functions
!TP
!Function
|-
| 1 || Ground
|-
| 2 || Test Oscillator
|-
| 3 || Test Oscillator Output
|-
| 4 || Sound Input
|-
| 5 || Regen Adjustment
|-
| 6 || Audio Post U1 Op Amps
|-
| 7 || Clock
|-
| 8 || Clock
|-
| 9 || Clock
|-
| 10 ||
|-
| 11 || On/Off Switch
|-
| 12 || +12V DC
|-
| 13 || Audio Post U3 Op Amps

|}
''Source: Bally Say It Again Schematics.''

'''Integrated Circuits used by the Say It Again sound board.'''

*U1 - LM3900 Quadruple Operational Amplifier
*U2 - SAD4096 n-channel Bucket-brigade audio delay line
*U3 - LM3900 Quadruple Operational Amplifier
*U4 - CD4066 Quad Bilateral Switch
*U5 - CD4046 Phase-Locked Loop
*U6 - CD4001 4-Channel NOR Gates
*U7 - CD4001 4-Channel NOR Gates
*U8 - LM7812 12V Voltage Regulator

'''Powering the board on the bench'''

The Bally Say It Again board requires only the solenoid voltage of +43V DC to operate.

If tracing the audio signal, a sine wave signal generator or another audio source, plus a scope is required.

=====The Very Easy Simple Fix aka the Solenoid Voltage is Out=====
If for some reason, the solenoid voltage is out, suspect a blown 5A F4 fuse on the power module or possibly fuse clips in poor condition. The Say It Again board runs on +12V DC voltage that is derived from the +43V DC solenoid voltage. Without this voltage, the reverb effect cannot take place although the board should pass the unaltered sound back to the Squawk and Talk board.

Note that the MPU will not boot without the +43V DC solenoid voltage.

=====Say It Again Sound Board General Troubleshooting=====

'''Basic maintenance actions'''

The "Regen" 50K and "Bias" 10K controls should be replaced. The 50K can be replaced with part 3386P-1-503TLF, while the 10K part is 3386P-1-103TLF.

The Say It Again board does not use the 1uF caps used in the Squawk and Talk board, but there are three capacitors in the 12V DC power supply that should be replaced. All are axial:

* C16 100uF 160V
* C18 100uF 100V
* C20 10uF 25V

C20 is a tantalum capacitor that can be replaced with a Kemet T322D106K035AT. However an electrolytic 106TTA035M could be substituted. Both are 35V.

=====Say It Again Sound Board - No Sound=====
If there is no sound at all coming from the cabinet speakers, troubleshooting must include both the Say It Again board and the Squawk and Talk Board as they work together.

*Make certain that the volume control on the coin door is turned up mid-way or higher. Move this volume control back and forth and check for noise from the speaker. If there is noise, then the cabinet speaker is connected and working. If no noise, check speaker and speaker wiring.
*Check to insure jumper FF is cut on the Squawk and Talk board. If it is cut, you can temporarily jumper FF and press the test button to insure that the Squawk and Talk board is working. If it does not work, see the Squawk and Talk section troubleshooting.
*With jumper FF removed, check the connections at plug J2 on the Say It Again board and J2 on the Squawk and Talk board. The audio leaves the Squawk and Talk board and enters the Say It Again board, then returns. If these connections are not correct, then there will be no sound.
*If the audio connections to and from the two boards are good, and the Squawk and Talk board is working, there should be sound even if the Say It Again Board is not working, although, perhaps at a lower volume. The audio should bypass the circuit through C1 and around U3 via R31, R32, C32 and C12.

[[File:J2 Bally S&T PCB IMG 8349.jpeg|300px|thumb|left|J2-9 is audio out. J2-7 is audio in. J2-8, 10 are grounds for the shields.]]
[[File:J2 Bally SIA PCB IMG 8350.jpeg|250px|thumb|right|J2-6 is audio in. J2-2 is audio out. J2-1, 5 are shield grounds. Only one shield is usually grounded to this board.]] 

=====Say It Again Sound Board - Sound But No Reverb=====

'''Adjust the Pots'''

Try adjusting the two pots, "Regen" and "Bias". If the reverb is restored, consider replacing the pots. Adjust the "Bias" pot following the procedure outlined in the Bally Centaur manual 'Set Up Procedure For 'Say It Again' (AS-2518-81) Module'.

'''Check the Power Supply'''

The Say It Again board has its own +12 regulated power supply. Test TP12 vs. TP1 to confirm that 12V DC is present. If missing, connect to the (+) side of C18 and check for 24V DC. If present, U8 or C20 are suspect.

If no voltage at C18, check the (+) side of C16 for ~60 - 70V DC. If present, suspect C20, U8 or VR1.

Lift one leg of C20 and see if the voltage returns. C20 is a tantalum capacitor that can fail as a short. If voltage is not restored, remove U8 and check the voltage at C18. If voltage at C18 is good, then replace U8. While this circuit can work with C20 missing, it is a good idea to replace it.

If voltage is not returned at C18, suspect VR1 but also inspect R41 for damage.

If the voltage is missing at C16, check C16, CR1 and the connections at J1-1,5.

'''Check the On/Off Circuit'''

U4 controls the reverb on/off function. Grounding at J1-3 turns off the reverb, but that option is not used in Centaur.

Check TP11 for approximately 11V DC. If present, the reverb switch should be on unless that section of U4 is defective.

To check the function of U4, hook up a scope to TP13 and TP1 and press the test switch on the Bally Squawk and Talk board. If signal is present at TP13, but not at U4-2 and TP11 is about 11V DC, then suspect U4.

It maybe possible to take U4 out of the circuit by jumping U4-1 to U4-2 since this on/off function is not utilized anyway.

If U4-13 is not about 11V DC, then check U4-12, which should be about zero and the base of Q3 which should be about 0.7V DC. Also check C30 which is a tantalum capacitor in this circuit. U4-5 should read about 11V DC, while U4-4/6 should read about zero.

'''Sound But Still No Reverb'''

If the power supply, the on/off circuit and the adjustment pots all work and there is still no reverb and no audio at TP13, the fault may lie with U1 or U3 that are LM3900 op amps, or the U2 reverb IC.

To test this circuit, press the test button on the Bally Squawk and Talk board and use a scope to confirm audio at TP4, then at TP6. If present, then U1 is OK.

Connect the scope at the junction of R19/R18 or the base of Q2 to confirm output from U2. If OK, but still no signal at TP13, then suspect U3, or Q1/Q2.

If the reverb IC U2 is not operating, check the presence of the clock at TP7 and TP8. If present, suspect U2. If missing, check TP9. If present, suspect U6 or U7. If no clock at TP9, suspect U5 and C14.

===== Say It Again Sound Board - Bias and Reverb Adjustments=====

[[File:J2 Bally SIA PCB IMG 8350.jpeg|150px|right|thumb|The REGEN and BIAS controls.]]
* Turn the main speaker volume control on the coin door all the way off.
* Turn REGEN R29 all the way off (counterclockwise).
* Connect a jumper from TP1 to TP2.
* Connect a jumper from TP3 to TP4.
* Connect a voltmeter to TP5 and TP1 and set to AC.
* Adjust the BIAS control R15 to obtain the maximum reading. The value should be about 0.5 to 0.6 AC.
* Disconnect jumpers.
* Turn the main speaker control on the coin door up to a normal level.
* Press the test button on the Bally Squawk and Talk board.
* Adjust REGEN R29 to the desired echo repeats.

Source: Bally 1983 Centaur II Manual.

====Cheap Squeak Sound Board Troubleshooting====

The schematic for this board can be found here: [[media:BallyCheapSqueakSchematics.pdf|Bally Cheap Squeak Schematics]]

[[File:Bally Cheap Squeak.JPG|300px|right|thumb|Bally Cheap Squeak Sound Board A080-91603-XXXX or Midway P/N M-051-00114-XXXX]]

At power up, the Cheap Squeak's LED will flicker briefly, then flash, flash again, then turn on and stay on. Once the LED stays on, it seems to turn itself off for certain sounds, and then turn back on. Likewise, it appears to idle with the LED on, when no sounds are playing.

The Cheap Squeak uses a single 1Kohm volume pot. If repairing this board, replace the pot with a high quality sealed 1K pot.

'''Test Points'''
*TP1 should measure about 11VDC.
*TP2 is 5VDC.
*TP3 is ground.
*TP4 is the clock signal, provided externally by the 6803 for the purpose of synchronizing address and data read cycles.
*TP5 is the reset signal, which is also present on pin 6 of the 6803. 

'''Bench Testing'''
# To power the board on the bench, provide 12VDC to J1, pin 10.
# Provide ground from the power supply to J1 pins 14 and 15.
# Connect a small speaker to the speaker output pins at J2 (2 pins).
# The board generates it's own 5VDC via a 7805 voltage regulator at U9. Therefore, an external 5VDC source does not need to be connected.

'''Special Note'''
The +5v can be connected directly to TP2, or +12V can be connected to TP1 to power the board. However, both do not need to be connected. If powering the board in this manner, the power amp will not be powered. +12v needs to be connected to the bottom of the L1 inductor, and ground connected either to the left leg of the L3 inductor or the left leg of the large capacitor at the bottom of the board (C24).

When powered on, the reset circuitry on the board holds pin 6 of the 6803 (~RESET) low for a split second, then allows it to go high.

Pressing SW1 should cause the board to generate a test sound, then the board reboots itself. Note that different sound ROMs may act differently. Generating a tone and rebooting is characteristic of the "X's and O's" sound ROM.

The test sound can be heard using an inexpensive logic probe like the [http://www.amazon.com/dp/B000Z9HAP4/ Elenco LP-560] at some points in the analog sound path. Attach the logic probe to +5VDC (TP2) and Ground (TP3) on the board. Probe pin 4 of the ZN429 DAC then press SW1. Some sort of tone should sound briefly, then the board will reboot. The tone can also be heard at pins 1 and 4 of the TDA2002 amp. Unfortunately, between the amp and R25, a logic probe isn't adequate for cheaply hearing the tone. However, if there is a tone at pin 4 of the ZN429, but no tone at pin 1 of the amp, then there is a good chance that the LM3900 has failed.

[[File:CheapSqueakBlownTantalum.jpg|300px|left|thumb|An example of a blown tantalum capacitor on a Cheap Squeak board (blue caps, top blown)]]

The Cheap Squeak board likes to blow the tantalum caps as shown in the picture on the left. While it's unclear why they tend to blow, simply replacing the blown cap usually returns the board to proper function. A gentle reminder, tantalum caps ARE polarized and must be installed in the correct direction, or they will burst into flames and/or explode, which could lead to injury. The marking for C22 isn't clear on the Cheap Squeak board. Use a multimeter to determine which through-hole is ground, and install accordingly. Most tantalum caps are marked on the +/positive side lead. 

This [http://www.pinball4you.ch/okaegi/pro_cheap.html link] contains some additional info regarding the Cheap Squeak sound board.
 

=====Cheap Squeak Schematic Errors=====
Note that the Cheap Squeak schematics for Black Pyramid have some incorrect info regarding the connections for U3 pin 2 to ground and U3 pin 20 to U4 pin 10.

[[File:BLY_Cheap_Squeak_Schems_Before.JPG|300px|left|thumb|Bally Cheap Squeak Sound Board Schematics w/ incorrect info]]
[[File:BLY_Cheap_Squeak_Schems_After.JPG|300px|right|thumb|Bally Cheap Squeak Sound Board Schematics adjusted to the board layout]]

All Cheap Squeak schematics have the following error. Diodes D7 and D8 are connected opposite of what the schematics state. Also, test point (TP1) is not located where the schematics show that it is. Please see the pic to the left (original schematics), and the pic to the right (corrected areas are circled).
 

====SB-100 Sound Board====
Technical write up regarding the SB-100 sound board is located [http://www.techdose.com/projects/Stern-Pinball-SB100-Sound-Board/346/page1.html here]. The Wayback Machine copy of this is here [https://web.archive.org/web/20110609040811/https://www.techdose.com/projects/Stern-Pinball-SB100-Sound-Board/346/page1.html page 1] 

Just some general tech notes. Please be advised of the following per the Stern SB-100 sound board schematics. A single 220mfd 50v capacitor can be installed at either position C47 and C48. Likewise, two 100mfd 50v capacitors at these two positions are acceptable substitutes. Even though the circuit board stencils are marked with a "+" on one of the cap leg positions, the capacitor(s) at these positions must bi-polar / non-polarized.
 

=====Sound Board Does not Make Sound at all=====
Much like the www.techdose.com website recommends, check for cold solder joints on all of the header connections. Since all of the generations of these boards are all single-sided, they are susceptible to cold / cracked solder joints. Also, make certain that the ribbon cables or harnesses are installed correctly. Pin 1 J5 of the MPU board should connect to pin 1 J1 on the sound board. If sound is still not present, check the voltage test points on the board. Finally, make certain that the amp is powered (a slight hum will be heard), the speaker is good, and the volume potentiometer is turned up and / or good too.

=====Missing Sounds on the Fully Populated SB-100 Sound Board=====
During solenoid test, the first 6 solenoids are allocated for sound board sounds. If sounds are only heard during the first 4 solenoids during test, it may not be that they are actually missing. Make certain that the MPU dipswitch 23 is set to on, otherwise only the first 4 sounds will be triggered during solenoid test. Hearing only 4 sounds is normal operation, if the sound board is set for chime sounds only. 

=====Missing Sounds on the Less Populated SB-100 Sound Board=====
The sounds for the games using the less populated boards are not the first 6 solenoids, like the fully populated sound boards. Instead, the sounds are the last things triggered during solenoid test. And, if the game's dipswitch is set for chimes (dipswitch 23 on some of the later games), no sounds will be heard, when the sound board's sounds should be triggered. 

=====Second Generation SB-100 Sound Board Does not Allow MPU to Boot (Typically After a Successful 1st Boot)=====
[[File:Stern SB11 SB-100 Reset.jpg|thumb|300px|left|Stern Service Bulletin 11]]
[[File:Stern SB-100 Less Pop Reset Front.jpg|thumb|right|300px|Stern SB-100 Less Populated (second generation) Sound Board. Note the 47Kohm resistor installed in place of a standard jumper, and the tantalum cap installed from one leg of the unpopulated C52 to the 47Kohm resistor. This is a common factory fix found on most second generation SB-100 sound boards.]] 
At some point, Stern released a service bulletin, regarding a fix to keep from erroneous info showing up in bookkeeping, due to "multiple toggling of the power switch of the game". With this bulletin, it recommends that a 47Kohm resistor and 3.3uF 6v tantalum capacitor be installed on the /RESET line of the 74107 chip. Likewise, pin 25 at J1 should be removed from the SB-100, or removal of the line that comes from the MPU, as this is the data line that carries the /RESET line. 

[[File:Stern SB-100 Less Pop Reset Line 74107 Back.jpg|thumb|300px|left|Factory modification on second generation board where /RESET line and +5V is tied together presuming that J1 pin 25 is removed.]]
[[File:Stern SB-100 Early Cut Reset.jpg|thumb|300px|right|/RESET line cut on a second generation sound board]] 
What is not stated in the service bulletin is that if pin 25 of J1 or the cable is not removed, the /RESET line and the +5V on the SB-100 will be tied together. The end result is a sound board that seems fine upon the very first boot of a "cold" game. If the game has been on at all, subsequent attempts of turning the game on and off results in an MPU board that is locked up. The signs of it locked up are that the diagnostic LED on the MPU board will never come on or is on immediately and stays locked on. The sound board also may belch out a very obnoxious loud BLURT, akin to a siren which does not descend in sound, that continues unless the game is turned off.

To resolve the problem without question, it is best just to cut the /RESET line right before it is tied to the +5V line.

Although this issue has not been observed on the first generation SB-100, which is fully populated, it can occur if the suggested service bulletin modification is performed.

One thing to note is that this problem doesn't appear to occur when using an Alltek Ultimate MPU board. Also, the problem can be overcome when using a Two Bits Fix-It board by pressing the reset button (performing a hard reset).
 

=====Removing the Sound Blurt from the SB-100 Upon MPU Boot Up=====
[[File:Stern SB-100 MCP120-460DI Reset Gen.jpg|thumb|300px|left|An MCP120-460DI reset generator and 4.7K pull up resistor added to the 2nd generation sound board]] 
Don't like the initial "PEW" sound that the SB-100 board blurts out when the MPU first turns on, add a reset generator to the board. A reset generator can be added to the sound board, which ties the /RESET line of the reset generator to pin 10 of U6 (the CLR signal for the 74107). In this example, an MCP120-460DI reset generator was used along with an external 4.7Kohm pullup resistor. Note that a small hole must be drilled into the board to pick up the needed +5V for the center leg of the reset generator. An MCP130-460DI can be used just as easily, and an external pullup resistor will not be needed. The board shown here is a 2nd generation board. A 1st generation board should be the same procedure.
 

=====Mapping the Sound Signals on the SB-100=====
[[File:Stern SB-100 Sound Signals Input.jpg|thumb|300px|left|SB-100 sound signals noted on the input side of the board.]]
[[File:Stern SB-100 Sound Signals Output.jpg|thumb|300px|right|SB-100 sound signals noted on the output side of the board.]] 
These two pics show the specific six different sound paths of the SB-100. If a specific sound is missing from the board, hopefully these will help in locating the failure point a little easier.
 

[[File:SB-100Annotated.jpg|thumb|500px|left|SB-100 sound signals annotated on a hi-resolution image. Cleaned up image provided by PinSider La4s. Annotation by Jim Palson.]] 
The image at left consolidates the two images above.
 

=====Bench Testing the SB-100=====
Connect the SB-100 board with the two ribbons normally used to connect the board to the MPU.

Additionally, connect the following as shown below...
* J2/6 - 12VDC
* J2/3 - Ground
* J3/8-9 - Speaker
* An 8Kohm resistor across J3 pins 1 and 3. 8Kohm provides a reasonable volume for debugging.
[[File:SB-100BenchTestConnections.jpg|300px|thumb|left|Bench connections for the Stern SB-100 sound board]]
 

=====Adjusting the Sound Quality on a Stern SB-100 board=====
Earlier versions of the Stern SB-100 Sound board can have an unpleasant high pitched sound for all the different sounds. STERN advises the following changes to lower the frequency of the tones, which sound much better to my ears.

* Replace all 3 of the 5k potentiometers at R2,R6, & R13 with 25k ohm pots. Suggested part # is 15mm Piher PT15LH06-253A2020
* Replace the 2.2k ohm resistor at R12 with an 8.2k ohm 1/4 watt resistor
* Upon completion of component replacement, adjust the trim pots according to the instructions below

[[File:Stern SB-100 Pots TPs.JPG|400px|thumb|left|The 3rd generation SB-100 with pots and complimentary test points notated]] 
Adjust the frequencies by putting the BLACK lead on ground (TP4) on the sound board and the RED lead of the multimeter set to the frequency setting (Hz) on the appropriate test point (see below and the pic to the left). Then, turn the pots one way or the other in small increments to the following specs. 

TP2 Adjust R6 138 Hz +/- 3Hz 
TP3 Adjust R2 104 Hz +/- 3 Hz 
TP5 Adjust R13 172 Hz +/- 3 Hz 
 

====SB-300 Sound Board====
Technical write up regarding the SB-300 sound board is located [http://www.pinball4you.ch/okaegi/rep_soundsb300.html here].

If some of the sounds are missing or incorrect when using a SB-300 sound board with an Alltek MPU board (e.g. especially noticable for the spinner sounds on a Meteor), try clearing memory on the MPU board to see if that fixes the issue.

 
=====Stern SB-300 Sound Board Modification for VSU-100 Usage=====
Games with a VSU-100 speech card require a modified SB-300 to utilize the speech. First, see if your SB-300 already has a trace for this connection by checking continuity between pin 5 of the rightmost connector at the bottom and the top of capacitor C14. If you read continuity, you do not need to do this mod. 

<center>
<gallery widths=300px heights=300px perrow=3 caption="Stern SB-300 Added Jumper Modification for Speech">
File:sb300sig3.jpg|<center>First solder point for jumper (pin 5 of rightmost connector)</center>
File:sb300sig2.jpg|<center>Second solder point for jumper (top of capacitor C14)</center>
File:sb300sign1.jpg|<center>Overall picture of jumper</center>
</gallery>
</center>
 

====VSU-100 Speech Board====
Unlike most all other combination sound speech boards made by Bally, Williams, and Gottlieb, Stern did not use a potentiometer for mixing the sounds and speech volume. 

If the speech is nonexistent, first make certain that the SB-300 sound board has the appropriate jumper added. The jumper goes between the right .156 connector pin 5 and the top of capacitor C14. Later revision SB-300 boards have a trace on the board for this so measure for continuity between those 2 points; if it is there, no need to add the additional jumper. Next, make certain that the EPROMs installed are valid. Very common for bad 2716's to cause the board to not work. You can replace both 2716's on games that use both U9 and U10 with a single 2532 installed into U9. Create this eprom file by using the DOS copy command: copy /b u9.716 + u10.716 u9comb.532. For Flight 2000, which only uses U9, just copy /b u9.716 + u9.716 u9f2k.532, or just burn the image into the lower half of a 2532. No jumper changes are needed to do this conversion, but you must make sure you only have ONE eprom installed in to u9 - you cannot install or leave an eprom into u10 due to the way the VSU-100 handles addressing. 

If the speech is much lower than the sound, suspect capacitor C6 first. 

Although the S14001A speech chip is somewhat expensive, it is still available from some online outlets. Do not assume that this chip is bad just because the speech is not working - it is more common for support components or missing voltages to cause speech board issues.

There is a short jumper handling the pass-through signals to the lamp board which uses IDC connectors, these can be problematic and cause lamp issues. A cable can be built with discrete wires and .100 connectors to replace this often overlooked issue.
 

===Flipper problems===
[[File:SeaWitchMeteorFlipperResistor.jpg|left|thumb|300px|Upper Flipper Mech with 1ohm sand resistor in series. Image courtesy of David Rowland.]] 
Some games, like Meteor and SeaWitch, make use of a 1ohm resistor, in series with the flipper coil "power winding", to reduce flipper power strength, while using a "standard" coil. This prevents drop targets from being damaged and allowed Stern to use the same coil across their game production.
 

====Rebuilding Flippers====
Nothing makes more of a difference on a game than having taut, crisp, flippers. Even if every other mechanical component on a game is rebuilt, if the flippers are sluggish and weak, players walk away with a sour taste of the games' experience. At a minimum, flippers should be taken apart, inspected for wear, have their coil sleeve replaced with new, and reassembled while dressing any worn plungers/stops with a file. Additionally, the end of stroke switch should be filed and adjusted, as well as the cabinet switches that actuate the flippers.

It is best to replace the plungers and links, the coil stop, and the end of stroke switch(es) with brand new components. Quality varies in replacement parts for this era game, with some components being completely unavailable in suitable replacements. One example is the proper Stern coil stop for flippers - while there is a modern replacement, it is very expensive and does not seem to work as well as the original copper colored stops. You can swap the copper stops from stern pop bumpers which show very little wear into the flipper positions. The worn stop from the flipper will usually work on the pop bumper fine as the pulse rarely pulls the pop plunger down to the stop (hence why they are perfect to swap).

Another part that seems to be available are replacement flipper bats for Stern games - while they will fit and work, they are slightly fatter in profile at the inlane end and will cause flipper hop.

Recently a supplier (pinballlife.com) has started remanufacturing classic Stern style flipper parts in the generation 2 style as well as Bally flipper parts and full flipper assmblies. The flipper plates are a welcome addition to the repair arsenal, as the holes are usually stripped out from hacky repairs over the years.

When reassembling the flipper, check the bushing for cracks or wear - the bushing's job is to hold the flipper bat square to the playfield at a high enough height to prevent the flipper from dragging across the playfield surface, causing gouging and wear. Be sure the flipper has a slight up-down leeway built in at both rest and at extension. The inlane guide should be a smooth transition from guide to flipper; while you can't adjust the flipper to tweak this, you can and should adjust the lane guide.

====Converting Bally or Stern Flipper Assys. to WMS WPC Style Flipper Assys.====
[[File:Stern Flipper Wiring Diagram.png|300px|thumb|left|Standard Stern flipper wiring diagram]]
[[File:Stern Flipper Wiring Diagram WPC Coils.png|thumb|300px|right|Stern flipper wiring with WPC coils installed]]
[[File:Stern Lower Left Flipper Stock Wiring.jpg|300px|thumb|left|Stern lower left flipper - stock wiring]]
[[File:Stern Lower Left Flipper WPC Wiring.jpg|thumb|300px|right|Stern lower left flipper - WPC wiring]]
[[File:Stern Lower Right Flipper Stock Wiring.jpg|300px|thumb|left|Stern lower right flipper - stock wiring]]
[[File:Stern Lower Right Flipper WPC Wiring.jpg|thumb|300px|right|Stern lower right flipper - WPC wiring]] 
Considered drastic by some, while sacrilege by others, converting Bally or Stern flippers to Williams WPC style flippers can be done. The only restriction may be whether or not the Williams flipper plate, which has a much larger footprint, will fit for a specific application or not. The closest Williams flipper coil in strength is the FL-11630. It is remarkably similar. It is also recommended to use the A-12390 coil stop. The A-12390 coil stop will result in nearly the same stroke at the Stern original flipper set up. Also, use end-of-stroke switch 03-7811. This was the EOS switch used on pre-fliptronics Williams games. If using the original Stern EOS switches, the long blade may need to be trimmed back. Otherwise, the blade may get caught on one of the flipper bushing screws.

As illustrated in the pics, the white wiring with the black Sharpie mark on it is the wire which goes to the secondary switch on the flippers. The secondary switch is used to send ground to the upper flippers of the game. The plain two white wires connect to the EOS switch of the flipper. Either white wire can be attached to either EOS switch blade solder lug. It does not matter.
 

===Pop Bumper Problems===
Pop bumpers on Bally/Stern games aren't that unusual, and the "usual" advice applies.

====Pop Bumper Randomly Fires====
An occasional spurious pop from a pop bumper on these games is normal. This is, somehow, an intentional artifact of the software, attempting to aggressively "debounce". These kick with full strength, but do not score. (This is discussed in the Bally Theory of Operation manual.) However, a failing capacitor on a switch may also cause issues. See the [[#Switch_Capacitor_Purpose_and_Failure|information under the switch capacitor section]] for additional details.

If the bumper activates whenever the flipper fires, check to make sure the switch is clean and gapped properly.

====Bally New-Style Pop Bumpers====
Bally changed the pop bumper assembling starting with Eight Ball Deluxe. Gone were the "Sunburst" caps. Caps are now two pieces, a large trim ring and a smaller inner logo circle.

Three tabs on the body of the pop bumper hold the trim ring on. These tabs tend to break off. Eventually, Bally added screw holes to the top of the bumper so that they could again be screwed on. Either the bumper cap or bumper body may be missing the screw holes, in which case the bumper body must be replaced.

If the original "pinned" lamp socket is present, replacing the body on these pop bumpers is quite easy. Remove the two nuts that hold the rod/ring assembly on under the playfield. Lower the playfield and remove the bumper cap and trim ring. Two screws can be removed from the bottom of the body. Pull the body off the playfield. The lamp socket will come with it, and two female housings will be holding the lamp socket on. These get pulled off. The socket comes out with a little coaxing and can be moved to the new pop bumper body.

One more note: The tabs of the bumper body were originally reinforced with a thin ring, 1mm in thickness and about as big around as the bumper cap itself. These were used to give the tabs a little more reinforcement so they don't flex and break off. Unfortunately, these are now unavailable.

===Setting Free Play===
If you read the manual that came with your game, you'll notice there are no factory provisions for setting the games on non-coin play. There are several options for homeowners to set their machines up so quarters or opening the coin door aren't required.

'''Free play via low replay scores'''

The easiest way to keep a quantity of credits on the machine is to set the first replay score to a very low value (10,000 on most machines). This way you can put several credits on the machine initially, and then each game played will probably win a credit. Press the self-test button inside the coin door until you see "01" in the ball-in-play display. Press the button on the mpu board itself (S33) to clear this value to zero, then use the credit button (on the coin door) to step the setting one click forward to 10,000. (Some games let you 'flick' a coin door switch to zero the value, S33 works for all games)

In most cases you will score 10,000 very quickly enabling the machine to self-replenish its credits.

'''Free play via adding a switch'''

If you like having the 'coin-up' sound most machines make, adding a free play switch to a game is relatively simple. Any type of normally open switch can be soldered to one of the coin switches and mounted in an unobtrusive way (through the coin door return is a popular example, or mounted to the coin return instead). While it is also possible to drill a hole in the cabinet or coin door to mount this type of switch, it is discouraged to do this as it is difficult or impossible to reverse cleanly.

This type of switch can be piggybacked onto the credit button switch itself, the initial full press will add a credit, and the pullback stroke will start a game.

'''Free play via ROM replacement'''

As of this writing, free play replacement ROMS are available for all Bally/Stern games. For many years only Bally freeplay roms of various flavors were available, and these romsets are incorporated into some of the aftermarket replacement MPU boards. In 2009 freeplay roms became available for all the stern mpu-100 and mpu-200 games as well, but as of yet (6/2020) are only incorporated into the Weebly replacement board (https://nvram.weebly.com/new-pcbs.html).

Some varieties of free play roms never let the credits go below one, some require a DIP switch setting, and some are free play only. Regardless of the type of free play rom used, they all work similarly. When the credits fall below a certain amount, the software code either increments a credit automatically, simply allows a game start with credits showing 00, or never lets the credits decrement below 01.

For many people free play roms are the preferred method of handling free play as no hardware modifications are needed to incorporate free play, and you can still have replay levels set to challenging levels. It also allows the machines to be placed in clubs, businesses, shows, etc. without the owner having to worry about people not knowing how to add credits via some other method. Press the credit button and go.

Free play ROM images for Stern MPU-100 games can be found here: [[File:Mpu100-freeplayroms.zip]]‎. 
Free play ROM images for Stern MPU-200 games can be found here: [[File:Mpu200-freeplayroms.zip]].

===Game Trips Power Line Circuit Breaker When Plugged into Outlet===
[[File:Stern Blown Varistor.JPG|300px|thumb|left|Incoming power cord, line filter, and blown / shorted varistor (Stern Seawitch)]] 
Had a thunderstorm roll through or a power surge from the electric company recently? If so, and the game is now tripping the circuit breaker of the outlet it's plugged into, without the game's power switch turned on, the [http://en.wikipedia.org/wiki/Varistor varistor] may have shorted. The varistor is used to protect the rest of the game's circuitry from power surges. 

Both Bally and Stern use varistors, which are typically located on the left cabinet wall. The varistor leads are soldered directly to the junction of the two power cord leads (hot and neutral) and the line side of the line filter. 

The obvious sign of a failed varistor is typically a black, charred discoloration throughout the "button" portion of the varistor. Varistors can blow rather violently, as seen in the adjacent pic, and there may be charred or burnt remains in the area surrounding the varistor. 

Varistors can be purchased from [https://www.greatplainselectronics.com/products.asp?cat=76 Great Plains Electronics]. Order the 130V variant for 120VAC (typically games in the US), and the 275V variant for 240VAC (typcailly games in Europe).
 

===Bally/Stern LED stays on after boot===
7th flash produced but no led dimming afterward:
The problem was one of the capacitors around the u12 (clock signal) were bad. I replaced c12,c16?, and c17. After that I
got the 7th flash and the dimmed led afterward.

===Solenoid Expander Board===
[[file:Solenoid_Expander.jpg|300px|thumb|left|alt=alternative text|Bally Solenoid Expander board- Arrow indicates necessary bulb]] 
There is a 555 bulb near (or sometimes not so near) that lights when the solenoid expander is activated. This bulb is essential for proper operation of the expander as the main opto isolator chip on the expander board needs a load to work. If you're having entire sets of solenoids not working, check this bulb. 

The header pins on this board like to crack, also, so standard operating procedure should be to replace or at minimum resolder the headers, and re-pin the connector with Trifurcon connectors. 

Also, it's very important that all solenoids on the expanded circuits have *TWO* diodes on them! If a coil was replaced with one that one had only a single diode, multiple solenoids could potentially activate on any solenoid expanded solenoid. Some side effects of a single diode coil installed could be a "memory" drop target activating when it shouldn't, or a target bank reset engaging when a saucer is supposed to eject.
 

===Using a Bally 7 digit display in a Stern game or using a Stern 7 digit display in a Bally game===
Bally and Stern 7 digit displays are interchangeable. However, Stern displays do not support commas and a small modification to the printed circuit board is necessary to make each board display all 7 digits in a "foreign" platform. 

First, use a small jumper to connect J1, pins 11 and 12 together. Bally and Stern chose different pins (Bally used pin 12, where as Stern used pin 11) to strobe the 7th digit. Without this mod, placing a Stern 7 digit display into a Bally game will result in the 7th digit not being displayed (and vice versa). Making this modification creates a "universal" Bally/Stern 7 digit display. 

[[File:Stern Bally Display Depth.JPG|300px|thumb|left|Comparison between the PCB size of a Bally and Stern 7-digit display]]
[[File:Stern Display Trays.JPG|300px|thumb|right|Stern display trays - 7-digit player displays are mounted to back of insert, while shallower 6-digit status display is mounted to front]] 

Bally and Stern also chose a different depth dimension for their display PCBs. Fortunately, the difference can be accommodated merely by mounting the display tray on the opposite side of the lamp insert panel. Note that this is also necessary when using "PinScore" displays in a Stern game. Alternatively, if using a Bally (or PinScore) display in a Stern game, since the Bally circuit board itself is not as deep, insert the display only as far as necessary for it to "flush up" to the backglass when installed.
 

[[File:Bally 7digit Stern Status.JPG|300px|thumb|left|Bally 7-Digit display used as a Stern status display before modification]] 
Bally displays automatically show '''commas''' whenever the thousands and millions digits are lit. To make a Bally display "match" the Stern display's non-comma capable display, clip the base lead from Q22 and commas will no longer light up. You can alternatively clip one end of diodes CR1 and CR2 and lift the diodes off the board. This modification would be easier to reverse.
 

Since Stern 7 digit displays do not support commas, using a Stern display in a Bally game will look a little "off" versus the other displays in the game, but this will get your displays running if you have no other choice.
 

=== Bally Game running slow (delayed score, controlled lamp flicker) or if game crashes before attract mode starts ===

If your Bally game is running very slow (solenoid pulses are delayed and long, controlled lamps flicker, scoring takes a few seconds to register) or if your game boots with the typical 7 LED flashes but then crashes (dead game with garbage on the displays), before attract mode starts you may have a bad C16 capacitor. C16 controls the display interrupt speed. If it is out of spec, it could cause the gap between display interrupts to be too small, leaving the processor no time to service other game operation. C16 is in the corrosion area near the 555 timer.

[[image:YT.png]] A YouTube video of a slow game caused by a failed capacitor at C16 can be viewed [http://www.youtube.com/watch?v=TlGMGLHrDD8&feature=channel_video_title here].

A game running slow can also be caused by a failed U14, which implements the "zero crossing" circuit.
Do NOT use the HEF4049. These will cause controlled lamps flicker.
CD4049 is a good choice.

===Converting a Bally -17, -35 or Stern -100 CPU Board to a Stern -200===
Stern MPU-200 CPU boards are probably the least common of the four CPU boards. The -200 boards are compatible in -17, -35, and -100 games. Although considering that -17, -35, and -100 boards are much more prevalent, it would be somewhat of a waste to use a -200 in any of these games. What if the more common boards could be converted to a -200? Check out [https://web.archive.org/web/20160309024537/http://warpzonearcade.com/?p=580 WarpZoneArcade's] blog entry to find out how to modify a -17, -35, or -100 to work as a -200.
 

==Game Specific Problems and Fixes==
===Stern Seawitch===
====Ball Trapped on Upper Left Flipper Plastic====
[[file:Seawitch-Protector2.jpg|left|300px|thumb|alt=alternative text|Ball deflector installed on a Seawitch]]
'''Problem:'''The ball gets trapped between the glass and the left side plastic above the 3 drop targets, from a hard shot to the center 3 drop targets. 

'''Solution:''' Cut a 11" (28cm) long by 5/8" to 7/8" (16mm to 22mm) strip of acrylic commonly used for home window glass replacement. Acrylic sheet can be scored and cut with a knife, but a bandsaw works best. Remove the plastic protector sheet, and plan the areas and angle you wish to bend.

With a propane torch (the instant on Bernz-o-Matic is great for this), heat the bend area for 2 seconds, and form the bend freehand or with a tabletop. The acrylic will stay soft and bendable for about 20 seconds, so if the angle is not right you can change the bend with or without additional heat from the torch. Clean up the cut edges and corners with a file and/or sandpaper. Brackets can be made out of thin stainless or mild steel. Keystone makes a bracket that is small and has 1 hole tapped for a 6-32 screw. (Manufacturer P/N#614 or Mouser P/N 534-614) A 6-32 nut & 3/8" computer case screw can be used to provide the needed clearance.
 

[[File:Seawitch Ball Trap Lexan.jpg|left|300px|thumb|Flat Lexan Ball Deflector installed on a Seawitch]] 
[[File:Seawitch Ball Trap Standoff.jpg|right|300px|thumb|Style of standoff used to secure Lexan to playfield]]
Here is an alternate method to keep from balls getting trapped on top of the plastic behind the upper left flipper. First, remove the existing large plastic behind the upper left flipper. Next, place the plastic onto a piece of Lexan, and trace the right side of the plastic's shape onto the piece of Lexan. Make certain to use enough of the plastic to cover the 3 screw holes in the vicinity of the flipper. These 3 screw holes will be used to secure the Lexan. Now, cut the piece of Lexan with a jigsaw. The edges can be smoothed with a file or sandpaper. Next, again place the plastic on the Lexan, and if satisfied with the results, mark the 3 screw holes that secure the plastic to the threaded metal standoff posts. Using about an 1/8" bit, (double check the exact size), drill the holes where the Lexan is marked. Place the original plastic back on the playfield. Take 3 nylon standoffs, which are typically used to secure circuit boards to a flat surface, and screw them onto the threaded metal standoff posts, where the nylon or rubber cap nuts would normally go. Do not use too long of a post, otherwise the playfield glass will hit the Lexan. Standoffs can be purchased from [https://www.greatplainselectronics.com/products.asp?cat=134 Great Plains Electronics]. Finally, firmly place the piece of Lexan down on the 3 nylon standoffs. 

====Upper Flippers Power Resistor====
[[File:Seawitch Upper Flip Resistor.JPG|300px|left|thumb|Power Resistor Installed in Series on Upper Left Flipper (Seawitch)]] 
On Seawitch, both upper flippers have a single 1 ohm 5 watt power resistor installed in series with the power winding of each flipper coil. Neither resistor is listed in the game's manual or schematics. It is presumed that the resistors were installed due to the upper flippers close proximity of nearby drop targets and plastics. The resistors are not necessary for proper function, and could be by-passed, but it is best to keep the resistors installed. The lack of this resistor will increase the flipper power, and more frequent breakage of drop targets or plastics may result. 

Similar resistors were installed on other Stern games at this time typically on upper flippers that were close to targets.

An alternate to leaving the resistors in place (used in this application as a crude voltage reduction device; i.e. runs very hot and causes burn marks on the bottom of the playfield) is to open up the end of stroke switches instead. The flipper will flip with less power which is the intended goal.
 

===Stern Hot Hand Not Booting at 5th Flash or Game Locks-up at Game Over===

If you find that your Stern Hot Hand game sometimes won't boot-up on the 5th flash; or that sometimes at Game-Over the displays go blank and the game dies, there is a good possibility it's the rotating flipper motor. The rotating flipper is pulsed briefly (on/off) as a byproduct of the PIA U11 test (5th flash) during boot-up. It also rotates constantly during a game and shuts off at game-over.

[[File:SternHH.png|300px|thumb|left|Diagram of the Stern Hot Hand motor showing the capacitor and MOV soldered across the motor terminals]]
The rotating flipper motor is connected directly to the 48V terminals 2 and 6 of the transformer. The 48V to the motor is controlled by a relay mounted to the motor bracket. Q18 on the Solenoid Driver Board energizes and de-energizes the relay coil which turns the motor on and off. When the motor turns off, it sends a voltage spike (EMF collapsing) that can sometimes be picked up by the MPU and cause the game to not boot (5th flash) or just shut down after game-over. During the boot sequence U11 PIA test (5th flash) the game enables all solenoids briefly as an artifact of how the test is performed. The slight on/off and resulting EMF pulse during the boot up on the 5th flash can cause the MPU to lock up.

Apparently Stern didn't realize this issue until later and seemed to have modified Orbitor 1 to suppress the spike. On Orbitor 1, there is both a 1uF, 2kV capacitor and 130V Metal Oxide Varistor (MOV) in parallel across the bumper motor terminals. This can also be accomplished with a 2.2uF, 250V mylar film capacitor and a 100V MOV soldered in parallel across the motor terminals. These devices help suppress the voltage spike
at the motor and keep it from reaching the MPU and causing lock ups. Simply solder both the MOV and capacitor across the rotating flipper motor terminals. The capacitor and MOV are not polarity specific so it doesn't matter which device lead goes on which motor terminal.
 

===Stern Meteor===
There is a software bug in Meteor's software concerning the bonus countdown - you will get a seemingly endless bonus multiplier at the end of your ball. (It's actually 255 x)

This is caused by a re-use of a memory location that holds your original bonus multiplier value during bonus countdown. The memory location is shared with the "collect all rockets" subroutine on the outlanes. If the software is dealing with lots of active threads, such as the spinner spinning at the same time as the collect all rockets and outhole subroutine are active, the bonus multiplier will become zero and count down from 255->1.

An updated game ROM named "U1a" includes a patch for the bug and is available on [http://www.ipdb.org/machine.cgi?id=1580 the Meteor IPDB page].

===Stern Orbitor 1===
Two balls need to be in the trough on boot up, or else you will hear "shoot pinball again" over and over with no attract mode

===Centaur===
If the game is missing any of the pinballs (or a bad trough switch) the game will not fully boot. The displays will show all "0"s across all displays. Hitting the test button will allow you to enter the test menu, and you can proceed to switch test to diagnose the trough switches.

==Parts Substitutions & Replacements==

===Components===
====Driver Board LM323K 5V Regulator====
Since the LM323K has become scarce, with mainly just sub-par Chinese knock-offs and counterfeit components available as replacements, an alternative is the [https://www.ezsbc.com/product/psu5/ EZSBC PSU5 LM323K replacement], and [https://www.ezsbc.com/product/psu5-nonoise/ the newer "no noise" version] for games exhibiting speaker noise when using the original style PSU5.

When installing on a Bally solenoid driver board, be sure to remove R49 since it adds an unnecessary load to the device (which is only necessary with a real LM323K), and replace R50 with a jumper, since the this device expects a direct path to ground. However, make sure to use an actual wire for the jumper and not a zero ohm resistor. A lot of current can surge through this critical connection and the wire on some zero ohm resistors may be too thin to handle it, which can result in voltage drops.

When using the PSU5, the large heatsink required by the LM323K is no longer needed and can be removed. It can also be left in place in the event that it is ever needed in the future.

Note that since the PSU5 is a switching device (rather than a linear device like the LM323K), it may introduce noise/static (or a "machine gun" sound) to the sound board or speaker. Adding a 1000uf/20v capacitor to the driver board between the 5V trace and the ground trace near J3 may help reduce or eliminate the issue.

An updated version of the PSU5, called the PSU5NN (NN = no noise) eliminates the "machine gun" sound sometimes imparted when powering a game down with the older version of the PSU5 installed. It can be found [https://www.ezsbc.com/product/psu5-nonoise/ here]. 

[[File:Bally5VAdjust.png|400px|thumb|left|Resistors that can be used to adjust output of the OEM LM323K or 78H05. (Image courtesy of PinSider barakandl)]]
[[File:EzSBCBallyStern.jpg|300px|thumb|right|A Stern Solenoid/Driver board updated with the ezSBC 5V regulator. R49 has been removed (previously located where the dotted line is) and R50 ha been removed and replaced with a beefy wire jumper. R49 and R50 are pictured laying on the board for reference. (Image courtesy of Chris Hibler)]] 
In the standard Bally/Stern implementation, resistors R49 and R50 increase the output voltage, presumably to accommodate voltage loss across connectors and the variance within the LM323K 5% specification.

If the LM323K outputs a perfect 5.00 volts between its pin 2 and 3, R49 and R50 will increase the output voltage according to this simplified equation:

*Vout = 5.00 * (1+ (R50/R49))

Bally and Stern used a 100 ohm resistor at R49. 
Bally used a 2.2 ohm resistor at R50. 
Stern used a 4.7 ohm resistor at R50.

Therefore, based on the above formula, a Bally board will deliver about 5.11 volts. 
A Stern board, based on the above formula, will deliver about 5.23 volts.

The specified tolerance of the LM323K is 5%. 
A 5% tolerance means that parts will deliver somewhere between 4.75 and 5.25 volts. 
Using Stern's resistor values, with a LM323K delivering the spec maximum of 5.25 volts, the formula above yields an output of 5.49 volts.
 

===Available 3D Printed Replacements===

With the increased availability of 3D printed parts, some Bally and Stern parts are being offered up via Shapeways and other 3D object marketplaces. Some of the available parts are:

* [http://www.shapeways.com/product/5A3C6F67G/bally-pinball-ball-outhole-kicker-arm-c-972-3?li=shop-results&optionId=43401482 Bally C-972-3 outhole kicker arm] used on games like Fathom 
* [http://www.shapeways.com/product/Z49NGF785/bally-ss-pinball-1-globe-light-shroud-upgrade?li=shop-results&optionId=43386300 Bally lamp insert single lamp shroud] 
* [http://www.shapeways.com/product/TNXKP3CPZ/bally-ss-pinball-2-globe-light-shroud-upgraded?li=shop-results&optionId=41384171 Bally lamp insert double lamp shroud] 
* [http://www.shapeways.com/product/X9SK45SSM/bally-pinball-rollover-button-c-587-6-ss-em?li=shop-results&optionId=43385429 Bally C-587-6 miniature white rollover button] used on games like Xenon 
* [http://www.shapeways.com/product/WV6TYWTKB/80-s-stern-ss-pinball-coin-plate-chute?li=shop-results&optionId=43403498 Stern coin insert plate] it is assumed that these have large enough slot openings to accept dollar coins
 

===Repair Logs===
====MPU boot halts after 2nd flash on Centaur====
Note: One possible reason that the boot process may stop after 2 flashes is if MPU J1 connector and lamp board J1 connector have been swapped, as indicated by this repair:
Here's a weird gotcha. While reconnecting the wiring harness to a previously known working Centaur II, the game wouldn't boot (only 2 flashes). We swapped in a known working Alltek reproduction board. Same symptom! After looking at a set of Centaur schematics we had on hand, the first half dozen pins of J1 on the MPU were striped wires, while the schematics called for solid-colored wires. Wait a minute... That's when we realized that the J1 connector on the MPU and the adjacent lamp driver board are not only the same number of pins, but the same KEY!! ARGH!!! Thankfully no damage was done on these low voltage lines. Swapping the MPU and lamp driver boards' J1 connectors resulted in a perfectly bootable/functional game. Why this accidental swap caused the 5101 RAM check to fail is an exercise left to the user.

Bally/Stern

2025-02-16T16:28:13Z

The Hammer: /* Say It Again Sound Board - No Sound */

Click to go back to the [[Bally/Stern_Electronics_Repair_Guides | Bally/Stern solid state repair guides index]].

==Introduction==
[[File:Bally-17_boardset.jpg|200px|thumb|left|Bally -17 Board Set]]
[[File:-35 boardset centaur.jpg|200px|thumb|right|Bally -35 Board Set]] 
Bally first started to experiment with solid state in the mid 70s with a couple conversions of EM games, Flicker and Bow & Arrow. Flicker's control system was designed by Jeff Frederiksen of Dave Nutting Associates, a Bally think-tank. This board utilized the Intel 4004 microprocessor. One prototype was built and was re-discovered in 1998. The Bow & Arrow system of which 17 were eventually built more closely resembles what actually ended up in the production games starting with Freedom. This boardset was designed by a Bally engineer named Doug MacDonald. There are at least two revisions of the prototype run's software in existence. 

For an interesting read, the patent Bally filed for their first "computerized pinball machine" can be viewed [http://www.google.com/patents/US4198051 here].
 

[[File:SternMPU-100.jpg|200px|thumb|left|Stern M-100 Board Set]]
[[File:Stern m-200 boardset.jpg|200px|thumb|right|Stern M-200 Board Set]] 
The early circuit boards were fabricated by a company called Universal Research Laboratories (URL). URL was purchased by Gary Stern as part of his strategy in acquiring the assets of the defunct Chicago Coin; it is this connection that enabled Stern to use essentially the same hardware for their solid state games as Bally. The software is remarkably similar as well, although Bally was more apt to use a "set" of operating system roms (the U6 chip) for several games, whereas Stern opted to custom-compile their roms for each game, or at most, pairs of games. 

[[File:GB8.jpg|200px|thumb|left|Bally Goldball special driver/voltage board]] 
Some later -35 Bally games used a combination of the solenoid driver board and the lamp driver board.
 

The core system consists of:
* A transformer to produce various AC voltages from line voltage
* A rectifier board to convert those AC voltages to DC and provide fuse protection
* A solenoid driver/voltage regulator board to regulate/filter the DC voltages and provide switching for solenoids
* A lamp driver board to switch up to 60 lamps on/off
 

Optional components added to the system at later dates include:
* Various sound boards, providing various type of sounds from simple tones, to background sound, to complex speech and sounds
* Auxiliary lamp driver boards, to provide control for more than 60 lamps
* Solenoid expander boards to allow more than 15 controllable momentary solenoids to be connected
 

==Games==
A list of solid state games by system and manufacturer (including those that aren't necessarily pinball). Source: http://www.ipdb.org
===Bally===
{|class="wikitable"
! scope="col" style="width:15%;" | Game Title
! scope="col" style="width:10%;" | MPU
! scope="col" style="width:10%;" | Power Supply
! scope="col" style="width:15%;" | Lamp driver
! scope="col" style="width:10%;" | Sound
! scope="col" style="width:30%;" | Additional Boards
! scope="col" style="width:10%;" | Transformer
|-
|[[Freedom]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125 [[#as2877freedom|see note]]
|-
|[[Night Rider]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Black Jack]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Evel Knievel]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Eight Ball]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Power Play]] || AS-2518-17 || AS-2518-18 || AS-2518-14 || Chimes || || E-122-125
|-
|[[Mata Hari]] || AS-2518-17 || AS-2518-18 || AS-2518-23 || Chimes || || E-122-125
|-
|[[Strikes & Spares]] || AS-2518-17 || AS-2518-18 || AS-2518-23 || Chimes || || E-122-125
|-
|[[Bally Lost World|Lost World]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| || E-122-125
|-
|[[The Six Million Dollar Man]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| || E-122-125
|-
|[[Bally Playboy|Playboy]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| || E-122-125
|-
|[[Voltan]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| A few games were outfitted with an AS-2518-51 sound board for testing || E-122-125
|-
|[[Supersonic]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-32|| || E-122-125
|-
|[[Bally Star Trek|Star Trek]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-50|| || E-122-125
|-
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Additional Boards
! scope="col" | Transformer
|-
|[[Bally Kiss|Kiss]] || AS-2518-35 || AS-2518-49 || AS-2518-23 || AS-2518-50|| Auxiliary Lamp Driver AS-2518-43 || E-122-131
|-
|[[Paragon]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-50|| || E-122-125
|-
|[[Harlem Globetrotters]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-50|| || E-122-125
|-
|[[Dolly Parton]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-50|| || E-122-125
|-
|[[Future Spa]] || AS-2518-35 || AS-2518-49 || AS-2518-23 || AS-2518-51|| Auxiliary Lamp Driver AS-2518-43 || E-122-131
|-
|[[Space Invaders]] || AS-2518-35 || AS-2518-49 || AS-2518-23 || AS-2518-51|| Auxiliary Lamp Driver AS-2518-52 || E-122-131
|-
|[[Nitro Groundshaker]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Silverball Mania]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Bally Rolling Stones|Rolling Stones]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Mystic]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Hotdoggin]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Viking]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Skateball]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Frontier]] || AS-2518-35 || AS-2518-18 || AS-2518-23 || AS-2518-51 || || E-122-125
|-
|[[Xenon]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-56 (Sounds Plus) || Auxiliary Lamp Driver AS-2518-52, Vocalizer module AS-2518-57 || E-122-142
|-
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Additional Boards
! scope="col" | Transformer
|-
|[[Flash Gordon]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61 (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, early games used the Sounds Plus (AS-2518-56) board and Vocalizer module (AS-2518-57) instead of the S&T board || E-122-142
|-
|[[Eight Ball Deluxe]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 || E-122-142
|-
|[[Embryon]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52 || E-122-142
|-
|[[Fireball II]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Auxiliary Driver - SCR Lamp Flasher AS-2518-67, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Centaur]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Say It Again AS-2518-81 (Reverb), Auxiliary Lamp Driver AS-2518-43, Solenoid Expander AS-2518-66, Auxiliary Driver - SCR Lamp Flasher AS-2518-67, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Elektra]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Fathom]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 || E-122-142
|-
|[[Medusa]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61A (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 || E-122-142
|-
|[[Vector]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66, Auxiliary Driver - GI Flasher AS-2518-68, Auxiliary Driver - Triac Lamp Flasher AS-2518-82 || E-122-142
|-
|[[Rapid Fire]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Ball Delivery Sensor & Motor Board AS-2518-102 || E-122-142
|-
|[[Mr. & Mrs. Pacman]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-161
|-
|[[Speakeasy]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-51 || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 || E-122-142
|-
|[[Spectrum]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Uses a second AS-2518-23 for lamps (2 total in game), Auxiliary Driver - SCR Lamp Flasher AS-2518-67, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Baby Pac-Man]] || AS-2518-133 || AS-2518-132 || AS-2518-107 (combo lamp and solenoid driver) || n/a || Vidiot AS-2518-121 || AS-3071-12
|-
|[[Eight Ball Deluxe Limited Edition]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61 (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52, Solenoid Expander AS-2518-66 ||
|-
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Additional Boards
! scope="col" | Transformer
|-
|[[BMX]] || AS-2518-35|| AS-2518-54 || AS-2518-23 || AS-2518-51 || Solenoid Expander AS-2518-66 || E-122-161
|-
|[[Grand Slam]] || AS-2518-133 || AS-2518-151 || AS-2518-147 (combo lamp driver/solenoid driver/regulator) || AS-2518-51 || || ?
|-
|[[Centaur II]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61B (Squawk & Talk) || Say It Again AS-2518-81 (Reverb), Auxiliary Lamp Driver AS-2518-43, Solenoid Expander AS-2518-66, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Goldball]] || AS-2518-133 || AS-2518-151 || AS-2518-147 (combo lamp and solenoid driver) || AS-2518-51 || Auxiliary Driver - GI Flasher AS-2518-68 || E-122-170
|-
|[[Eight Ball Deluxe Classic]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || AS-2518-61 (Squawk & Talk) || Auxiliary Lamp Driver AS-2518-52 || ?
|-
|[[Granny and the Gators]] || AS-2518-133 || AS-2518-132 || AS-2518-107 (combo lamp and solenoid driver) || M-051-00114-B045 (Cheap Squeak) || Vidiot Deluxe A062-91600-D000 || AS-3071-12
|-
|[[X's & O's]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43 || E-122-142
|-
|[[Kings of Steel]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43 || E-122-142
|-
|[[Black Pyramid]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43 || E-122-142
|-
|[[Spy Hunter]] || AS-2518-35 || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43, Auxiliary Driver - GI Flasher AS-2518-68 || E-122-142
|-
|[[Fireball Classic]] || AS-2518-35 [[#fbmpu|†]] || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Solenoid Expander AS-2518-66 || AA40-0037-0000
|-
|[[Cybernaut]] || AS-2518-35 [[#cympu|‡]] || AS-2518-54 || AS-2518-23 || M-051-00114-B045 (Cheap Squeak) || Auxiliary Lamp Driver AS-2518-43 || ?
|}
<div id="as2877freedom"></div>*Note: Part of the AS-2877 POWER TRANSFORMER MODULE which has the AS-2518-18 Rectifier Board Assembly mounted directly onto the transformer using a bracket. Later games had the AS-2877-1 POWER TRANSFORMER MODULE which had a large metal plate onto which both the transformer and AS-2518-18 Rectifier Board Assembly were mounted. See [http://www.ipdb.org/showpic.pl?id=4500&picno=40867 Inside Backbox] photo on the Internet Pinball Database page of Freedom for an example of AS-2877. See also [http://www.planetarypinball.com/reference/partsmanuals/BLY_Parts_1979/index.html#/4/ Page 4 of the Bally 1979 Parts Catalog].
 
<div id="fbmpu"></div>† Note: Fireball Classic was sometimes fitted with a 6802 MPU board (an upgrade from the -35 board)
 
<div id="cympu"></div>‡ Note: Cybernaut was sometimes fitted with a 6802 MPU board (an upgrade from the -35 board), or a 6803 MPU board.

===Stern===
{|class="wikitable"
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Transformer
! scope="col" | Notes
|-
|[[Pinball]]|| M-100 || TA-100 || LDU-100 || Chimes || 16B-3 ||
|-
|[[Stingray]]|| M-100 || TA-100 || LDU-100 || Chimes || 16B-3 ||
|-
|[[Stars]]|| M-100 || TA-100 || LDU-100 || Chimes || 16B-3 ||
|-
|[[Memory Lane]]|| M-100 || TA-100 || LDU-100 || Chimes || 16B-3 ||
|-
|[[Lectronamo]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Wild Fyre]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Nugent]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Dracula]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Trident]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Hot Hand]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Magic]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
|[[Cosmic Princess]]|| M-100 || TA-100 || LDU-100 || SB-100 || 16B-3 ||
|-
! scope="col" | Game Title
! scope="col" | MPU
! scope="col" | Power Supply
! scope="col" | Lamp driver
! scope="col" | Sound
! scope="col" | Transformer
! scope="col" | Notes
|-
|[[Meteor]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Galaxy]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses relay to turn on / off general illumination
|-
|[[Ali]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses relay to turn on / off general illumination
|-
|[[Big Game]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || First Stern 7 digit game, widebody
|-
|[[Seawitch]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Cheetah]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || First stern game using plastic pop bumper rod and ring, widebody
|-
|[[Quicksilver ]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Stargazer]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Nine Ball]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Iron Maiden]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Widebody. Uses IM-100 flash lamp board.
|-
|[[Viper]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Widebody
|-
|[[Dragonfist]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Cue]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 ||
|-
|[[Flight 2000]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, widebody
|-
|[[Freefall]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, widebody
|-
|[[Lightning]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, uses interface board for bonus display in playfield
|-
|[[Split Second]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, widebody
|-
|[[Catacomb]]|| M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100
|-
|[[Orbitor 1]] || M-200 || TA-100 || LDU-100 || SB-300 || 16B-6 || Uses voice module VSU-100, widebody
|}

==Technical Info==
===The Bally / Stern Board Set===
The Bally/Stern boardsets always consist of a rectifier board, a solenoid driver/power regulator board, a lamp driver board, and an mpu board. These boards utilize the Motorola 6800 series of microprocessors, 2 peripheral interface adapter chips (6821 PIAs), a switch matrix, multiplexed gas plasma displays, and direct driving of lamps and solenoids (no matrix). Lamps are switched on near the zero crossing 120 times a second to prevent premature lamp filament burnout. 

Additional boards present in games may include various flavors of sound boards, as well as additional lamp driver boards (both main and auxiliary), solenoid expander boards, specialized boards such as an echo (say-it-again) board, and speech boards. 

The software utilized in these games is very similar to one another, consisting of an "operating system" and a "game rom"; Bally utilized a masked rom for their OS over several games, enabling many roms to be ordered at one time for lower manufacturing cost. Stern custom compiled their operating system for each game, although some games have the same exact rom codes, differing switches in each of those affected games perform different functions although the rulesets are the same/very similar to one another. 

Starting with the Stern Mpu-200 series of games (Meteor, 1979), Stern utilized a state machine architecture, where the core operating system handles the various housekeeping functions (displays, switch reading, memory management, lamps/solenoid driving, etc.) and the state layer handles things like game rules and timing of lamp and sound effects. This enabled the programmers to concentrate on defining their rulesets and lamp effects instead of tweaking timing within the assembly code itself. The state machine is multi-threaded and is able to execute up to 16 threads at one time. 

Bally games continued to use a real-time setup, where all functions are coded in 6800 assembly language, necessitating lots of additions to the operating system over the years to enable more sophisticated light and sound effects/choreography. Contemporaries of Bally (Gottlieb, Stern, and Williams) all switched to the state machine architecture at some point in their solid state eras. The coding speed advantage of the state machine enabled more rapid development of software, a distinct advantage when production runs started to become shorter and shorter. 

===Recommended Documentation===
====Manuals & Schematics====
Schematics for each game are essential in tracing down connections to lamps, switches, and solenoids. The owner's manual is a handy resource to have for dip switch settings as well as audit information.

The early -17 Bally games as well as the early stern mpu-100 games have both an owner's manual and a separate schematic package available. If buying documentation on ebay or the like, be sure to check with the seller to see what is included. Most documentation is also available via ipdb.org although the quality of some of the scans make it difficult to extract the needed information. Be aware that although rare, some factory documentation contains errors in schematics as well as game descriptions and settings.

=====Documentation Errors/Addendums=====
======Schematic Errors with Stern MPU-200 MPU======
<center>
<gallery widths=200px heights=200px perrow=3 caption="MPU-200 Schematic Errors">
File:MPU-200 Upper Schem.jpg|<center>Modified schematics showing the TP3 and R16 errors</center>
File:MPU-200 Lower Schem.jpg|<center>Modified schematics showing the actual path of U17 pin 10</center>
File:Stern MPU-200 U17 Jumper.jpg|<center>Factory jumper installed on a Stern MPU-200 board. This ties U17 pin 10 to U15 pin 3 and pin 25 of both U10 and U11.</center>
</gallery>
</center>
There are two TP1s noted on the schematics. The upper TP1 (noted as 21.5vdc pulsating) should be TP3.

There are two R18 resistors noted in the "zero crossing detector" cited at the top left of the page. The lower resistor should be R16 and the upper resistor should be R18.

U18 pin 6 '''SHOULD NOT''' connect to U17 pin 10, nor should U19 pin 13 as drawn in the schematics.

U17 pin 10 should go to U15 pin 3, U10 and U11 pin 25, U7 pins 10 and 13, and to E37 and E38, which are tied together without a jumper.

The signal going to U17 pin 10 is VUA 02', not VUA as the schematics state.

It has been noted in online forums that some MPU-200s have the trace cut between U18 pin 6 and U17 pin 10, and a jumper installed from U17 pin 10 to a via located to the right of U17. This ties U17 pin 10 to U10 pin 25, as it should be. A picture of the factory jumper installed is above, however, the cut trace could not be found in this instance.
 

======Stern Transformer Schematics======
* On the 16B-6 transformer schematics, the transformer voltage for lugs 2/4/6 is omitted. It should be noted as 49VAC, like in the schematics for the earlier 16B-3 transformer.
[[File:Stern-16b-6_schematic-error.jpg|thumb|left|250px|Stern 16B-6 transformer schematics omission]] 

======Game Manual Errors/Updates======
* [https://www.ipdb.org/files/249/Stern_1980_Big_Game_Corrections_to_Game_Manual_March_1980.pdf Stern Big Game: Manual Corrections]

====Introduction to Pinball====
Bally produced a series of "Introduction to Flipper Games" guides that included the basics of pinball machines.
{| class="wikitable"
|-
!Guide
!Cover
!Source
!Notes

|-
|Introduction to Bally Flipper Games, Revised June 1981
|[[file:Introduction-to-bally-flipper-games_revised-june-1981-cover.jpg|thumb|left|140px]]
|
|

|-
|Introduction to Bally Midway Flipper Games, Revised July 1983
|[[file:Introduction-to-bally-flipper-games_revised-july-1983-cover.jpg|thumb|left|140px]]
|[[media:Introduction-to-bally-flipper-games_revised-july-1983.pdf|PDF]]
|

|}

====Theory of Operation & Repair Guides====
Less important but still handy are the Bally Theory of Operation manual and the Repair Manuals.

The repair manuals are written with the use of test boards called AID1 and AID2 in mind (essentially a specialized logic probe), but can still have some helpful troubleshooting steps outlined. The latest revision of a repair manual normally supersedes all other previous repair manual revisions.

{| class="wikitable"
|-
!Guide
!Cover
!Source
!Notes

|-
|Bally Electronic Pinball Games Theory of Operation FO 601-2
|[[file:Bally-theory-fo601-2-cover.jpg|thumb|left|140px]]
|[[media:Bally-theory-of-operation-FO-601-2.pdf|PDF]]
|Supersedes Theory of Operation guides FO 601 and 601-1.

|-
|Bally Electronic Pinball Games Repair Procedures FO 560-3
|[[file:bally-repair-fo560-3-cover.jpg|thumb|left|140px]]
|[[media:Bally-repair-procedures-FO-560-3.pdf|PDF]]
|Supersedes repair guides FO 511, FO 512, FO 513, [[media:Bally-repair-procedures-FO-560.pdf|FO 560]], [[media:Bally-Repair-Procedures-FO-560-1.pdf|FO 560-1]], and 560-2.

|-
|Theory of Operation - Stern's Microprocessor Controlled Solid State Games (1979)
|[[file:Stern-theory-of-operation-book-1979-cover.jpg|thumb|left|140px]]
|[[media:Theory_Of_Operation_Stern's_Microprocessor_Controlled_Solid_State_Games_(Stern_MPU-100).pdf|PDF]]
|Applicable to Stern MPU-100 games from 1977-1979: Pinball, Stingray, Stars, Memory Lane, Lectronamo, Wild Fyre, Nugent, Dracula, Trident, Hot Hand, Magic.
|}

=====Individual Guides=====
* [[media:Bally-vidiot-deluxe-theory-of-operation.pdf‎|Vidiot Deluxe Theory of Operation]]

====Parts Catalogs====
Parts catalogs can also be useful, which include part numbers (helpful for purchasing parts online), exploded views of assemblies (helpful to see how the assemblies are put together), and board layouts & parts lists, and diagrams for controlled lamp, solenoid, and rubber locations. Online copies of Bally parts catalogs can be found on [http://www.planetarypinball.com/mm5/merchant.mvc?Screen=BOOK Planetary Pinball].

{| class="wikitable"
|-
!Manufacturer
!Catalog
!Cover
!Source
!Games
!Notes

|-
|Bally
|1979 Parts Catalog
|[[file:bally-1979-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/gseb/ Viewer] [[media:Bally-Parts-Catalog-1979-fixed.pdf|PDF]]
|Freedom, Night Rider, Black Jack, Mata Hari, Evil Knievel, Eight Ball, Lost World, Power Play, Strikes & Spares, Six Million Dollar Man
|

|-
|Bally
|1979-1 Parts Catalog
|[[file:bally-1979-1-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/wjsc/ Viewer] [[media:Bally-Parts-Catalog-1979-1.pdf|PDF]]
|Playboy, Supersonic, Star Trek, Kiss, Paragon
|

|-
|Bally
|1980 Parts Catalog
|[[file:bally-1980-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/afmm/ Viewer] [[media:Bally-Parts-Catalog-1980.pdf|PDF]]
|Harlem Globetrotters, Dolly Parton, Future Spa, Nitro Groundshaker, Silverball Mania, Rolling Stones, Space Invaders
|

|-
|Bally
|1980-1 Parts Catalog
|[[file:bally-1980-1-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/tzut/ Viewer] [[media:Bally-Parts-Catalog-1980-1.pdf|PDF]]
|Mystic, Hotdoggin', Viking, Skateball, Frontier, Xenon, Flash Gordon
|

|-
|Bally
|1981 Parts Catalog
|[[file:bally-1981-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/wurt/ Viewer] [[media:Bally-Parts-Catalog-1981.pdf|PDF]]
|Eight Ball Deluxe, Fireball II, Embryon, Fathom, Medusa, Centaur
|Note: Even though the parts catalog states otherwise, Fathom does use the sound board EE jumpers

|-
|Bally
|1982 Parts Catalog
|[[file:bally-1982-parts-catalog-cover.jpg|thumb|left|140px]]
|[https://online.fliphtml5.com/vrtyz/fimq/ Viewer] [[media:Bally-Parts-Catalog-1982.pdf|PDF]]
|Elektra, Vector, Rapid Fire, Mr. & Mrs. Pac Man, Spectrum, Speakeasy, BMX
|Note: Even though the parts catalog states otherwise, Fathom does use the sound board EE jumpers

|-
|Stern
|General Parts Book
|[[file:Stern-general-parts-book-cover.jpg|thumb|left|140px]]
|
|
|

|-
|Stern
|Parts Catalog (1979)
|[[file:stern-70s-parts-catalog-cover.jpg|thumb|left|140px]]
|[[media:Stern-parts-catalog-1979.pdf|PDF]]
|Pinball, Stingray, Stars, Memory Lane, Lectronamo, Wild Fyre, Nugent, Dracula, Trident, Hot Hand
|Service bulletins, diagnostic information, playfield parts, circuit board layouts & parts lists. Does not contain any playfield layout diagrams.

|-
|Stern
|1981 Parts Catalog
|[[file:Stern-1981-parts-catalog-cover.jpg|thumb|left|140px]]
|[[Media:Stern-parts-catalog-1981.pdf|PDF]]
|Pinball, Stingray, Stars, Memory Lane, Lectronamo, Wild Fyre, Nugent, Dracula, Trident, Hot Hand, Meteor, Galaxy, Magic, Cheetah, Quicksilver, Ali, Big Game, Seawitch, Star Gazer, Flight 2000, Nine Ball, Freefall, Lightning
|Includes playfield parts, but no board information or schematics. Includes information, parts lists, and diagrams for Stern video games.

|}

Note: Baby Pacman and Granny & The Gators do not specifically appear in the pinball parts catalogs, but many of the same parts are used on the playfield. The game specific manuals and the Vidiot and Vidiot Deluxe theory of operation manuals for each game will need to be referred in most cases for information about each game.

====Service Bulletins====
Service bulletins detailed any problems or issues with games that were discovered after they were released.

'''Service Bulletin Books'''
{| class="wikitable"
|-
!Manufacturer
!Version
!Cover
!Source
!Games
!Notes

|-
|Bally
|Service Bulletins, August 1978
|[[file:Bally-service-bulletin-book-1978-cover.png|thumb|left|140px]]
|[[media:Bally-service-bulletin-book-1978.pdf|PDF]]
|Black Jack, Eight Ball, Evel Knievel, KISS, Lost World, Mata Hari, Night Rider, Paragon, Playboy, Power Play, Six Million Dollar Man, Skateball, Star Trek, Strikes and Spares, Supersonic, Voltan
|

|-
|Bally
|Service Bulletin Book, 1987
|[[file:Bally-service-bulletin-book-1987-cover.png|thumb|left|140px]]
|[[media:Bally-service-bulletin-book-1987.pdf|PDF]]
|Kings of Steel, Spy Hunter, Fireball Classic, Cybernaut
|Also contains some early Bally 6803 games
|}

'''Individual Service Bulletins'''

Note: Stern Electronics service bulletins 1 through 16 can be found in the [[media:Stern-parts-catalog-1979.pdf|1979 Stern Parts Catalog]].

{| class="wikitable sortable"
|-
!Manufacturer
!Service Bulletin
!Date
!Game(s)
!Summary
!Notes
|-
|Stern
|[[media:Stern_service-bulletin_15.pdf|15]]
|1979
|All Games (General)
|Solid State Digit Display Repair Procedures
|
|-
|Stern
|[[media:Stern_service-bulletin-23.pdf|23]]
|1980-12-02
|Flight 2000
|Flight 2000 breaking flipper return plastic
|Fix: Insert metal bar under return plastic
|-
|}

===The Wiring Color Code===
The Bally color coding system is a carry over from the EM era. Either one color or a two color code is used for every wire. The first number is the wire's insulation color, while the second number is the trace color, if one is used. The traces on the wire can either be dashes or stripes. Either type of marking has the same coding designation. An example of a wire with the code 15, would be a red wire with a white trace. A black wire with no trace would be code 80. If a wire color is used more than once, a "-" and the "nth" time the color is used is added as a suffix to the color code. An example of this is a red wire with white traces used a second time. The code for the wire would be 15-1. 

Conversely, Stern never adopted a color coding system. Instead, the wire color was marked accordingly in the associated documentation, (ie. a white wire with a blue trace is referred to as W-BLU, red with yellow is R-Y, black is just B, etc.). 

Below is the Bally color chart. 

{| class="wikitable" style="margin: 1em auto 1em auto;"
!
!1
!2
!3
!4
!5
!6
!7
!8
!9
!0
!Jumper
|-
| Color
|| <center>  Red  </center>
|| <center>  Blue  </center>
|| <center>  Yellow  </center>
|| <center>  Green  </center>
|| <center>  White  </center>
|| <center>  Brown  </center>
|| <center>  Orange  </center>
|| <center>  Black  </center>
|| <center>  Gray  </center>
|| <center>  No Trace  </center>
|| <center>  Jumper  </center>
|}

===Connector Designations===
All Bally / Stern machines have a common naming convention for all of the connectors in the game. A specific connection uses two parts - a prefix and a suffix. The prefix is the board number, and the suffix is the connection on the board. When referencing a specific connector pin within a housing, a dash follows the connection number. For example, the connector pin for the coin door self test switch signal on the CPU board is A4J3-1. A single connection, in this case the key on a display, for the player 2 display would be 2A1-14. The same connection on a player 3 display would be 3A1-14. 

The following boards are assigned the same numbers throughout Bally / Stern games.
*Lamp Driver Board - A5
*MPU Board - A4
*Solenoid Driver Board - A3
*Transformer Module / Rectifier Board - A2
*Displays - A1
 

===Switch Matrix===
[[File:Bally Stern switch matrix.png|thumb|left|200px|Bally / Stern 5 x 8 Switch Matrix]] 

The Bally / Stern switch matrix is a 5 x 8 matrix consisting of a maximum of 40 switches. There are a total of 5 switch strobes (columns), (starting with 0, ending with 4), and 8 switch returns (rows), (starting with 0, ending with 7). The numbering convention for the switches is to start at 01, increase by 1 in the same strobe, and continue consecutively to 40. To isolate the switches, a 1N4004 diode, or in some cases a 1N4148 diode, is placed across the switch itself. Not every switch in the matrix is used on every Bally / Stern game. 

Although rare, Bally did add a 6th strobe (strobe 5) for some games, such as Centaur, Fathom, Medusa and Spectrum.
 

Connections for the switch matrix originate from the two connectors located on the right side of the CPU board. Connector A4J3 is used for all the switches on the coin door, the ball roll tilt, and the pendulum tilt. While connector A4J2 is for all of the switches on the playfield. 

{| class="wikitable"
!
!Strobe 0 
(A4J2-1 / A4J3-2) 
!Strobe 1 
(A4J2-2 / A4J3-3) 
!Strobe 2 
(A4J2-3) 
!Strobe 3 
(A4J2-4) 
!Strobe 4 
(A4J2-5)
!Strobe 5 (When Used) 
(A4J4-5)
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 0 (A4J2-8 / A4J3-9) 
| style="vertical-align: top; text-align: center;" | 01 
| style="vertical-align: top; text-align: center;" | 09 
| style="vertical-align: top; text-align: center;" | 17 
| style="vertical-align: top; text-align: center;" | 25 
| style="vertical-align: top; text-align: center;" | 33 
| style="vertical-align: top; text-align: center;" | 41 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 1 (A4J2-9 / A4J3-10) 
| style="vertical-align: top; text-align: center;" | 02 
| style="vertical-align: top; text-align: center;" | 10 
| style="vertical-align: top; text-align: center;" | 18 
| style="vertical-align: top; text-align: center;" | 26 
| style="vertical-align: top; text-align: center;" | 34 
| style="vertical-align: top; text-align: center;" | 42 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 2 (A4J2-10 / A4J3-11) 
| style="vertical-align: top; text-align: center;" | 03 
| style="vertical-align: top; text-align: center;" | 11 
| style="vertical-align: top; text-align: center;" | 19 
| style="vertical-align: top; text-align: center;" | 27 
| style="vertical-align: top; text-align: center;" | 35 
| style="vertical-align: top; text-align: center;" | 43 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 3 (A4J2-11 / A4J3-12)
| style="vertical-align: top; text-align: center;" | 04 
| style="vertical-align: top; text-align: center;" | 12 
| style="vertical-align: top; text-align: center;" | 20 
| style="vertical-align: top; text-align: center;" | 28 
| style="vertical-align: top; text-align: center;" | 36 
| style="vertical-align: top; text-align: center;" | 44 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 4 (A4J2-12 / A4J3-13) 
| style="vertical-align: top; text-align: center;" | 05 
| style="vertical-align: top; text-align: center;" | 13 
| style="vertical-align: top; text-align: center;" | 21 
| style="vertical-align: top; text-align: center;" | 29 
| style="vertical-align: top; text-align: center;" | 37 
| style="vertical-align: top; text-align: center;" | 45 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 5 (A4J2-13 / A4J3-14) 
| style="vertical-align: top; text-align: center;" | 06 
| style="vertical-align: top; text-align: center;" | 14 
| style="vertical-align: top; text-align: center;" | 22 
| style="vertical-align: top; text-align: center;" | 30 
| style="vertical-align: top; text-align: center;" | 38 
| style="vertical-align: top; text-align: center;" | 46 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 6 (A4J2-14 / A4J3-15) 
| style="vertical-align: top; text-align: center;" | 07 
| style="vertical-align: top; text-align: center;" | 15 
| style="vertical-align: top; text-align: center;" | 23 
| style="vertical-align: top; text-align: center;" | 31 
| style="vertical-align: top; text-align: center;" | 39 
| style="vertical-align: top; text-align: center;" | 47 
|-
| style="vertical-align: top; text-align: left; font-weight: bold;" | Return 7 (A4J2-15 / A4J3-16) 
| style="vertical-align: top; text-align: center;" | 08 
| style="vertical-align: top; text-align: center;" | 16 
| style="vertical-align: top; text-align: center;" | 24 
| style="vertical-align: top; text-align: center;" | 32 
| style="vertical-align: top; text-align: center;" | 40 
| style="vertical-align: top; text-align: center;" | 48 
|}

It is worth mentioning that the self test switch, which is located on the inside of the coin door and used to enter tests, audits, and bookkeeping, is not part of the switch matrix. A single signal is sent to the self test switch from the U10 PIA on the CPU board via connection A4J3-1, and returned to ground via a connection A3J2-7 on the solenoid driver board. 

Also, the switch commonly referred to as "switch 33" on a Bally or Stern CPU board, and used to reset audits and bookkeeping, is not part of the switch matrix either. This switch receives a signal from the 6800 CPU chip, and when closed, sends the signal to ground. Starting with the first MPU-200 Stern game, Meteor, Stern added a second switch to the inside of the coin door to serve the purpose of remotely resetting audits and bookkeeping. The signal for this secondary switch is tied to the input line of switch 33, and leaves the CPU board via connection A4J3-5. Its return line is sent to ground via a daisy-chained lead to the self test switch.
 

===Bally and Stern MPU Boards===
<gallery widths=300px heights=300px>
File:Bally -17 MPU.JPG|Bally AS-2518-17 MPU Board
File:Bally -35 MPU.JPG|Bally AS-2518-35 MPU Board
File:Bally-6802-mpu-board.jpg|Bally 6802 MPU Board (A080-91638-D000). Note alkaline corrosion abatement and addition of "SuperCap" to retain CMOS memory
</gallery>
<gallery widths=300px heights=300px>
File:Mpu100-01.jpg|Stern M-100 MPU Board
File:Mpu200-01.jpg|Stern M-200 MPU Board
</gallery>
All Bally and Stern MPU boards are built around the Motorola 6800 series CPU chip and 6820 or 6821 peripheral interface adapters (PIAs).

In most cases, if a Bally MPU board has taken a bad hit from alkali damage, the bottom right corner of the board typically takes a hit. Unfortunately, the bottom right corner of the board is also the location where the board number is stenciled onto the masking. If the masking has delaminated, it will take the stenciled board number information with it. At this point, it would be difficult to determine what board it actually is.

[[File:Bally -17 Quick ID.JPG|left|300px|thumb|32 pins at J5 of a -17 MPU]]
[[File:Bally -35 Quick ID.JPG|right|300px|thumb|33 pins at J5 of a -35 MPU]]

However, there is a quick and easy way to determine whether the board is either a -17 or -35. Simply look at the J5 header pin connection located at the top center of the board. If there are only 32 pins (including one empty key) at the connection, the board is a -17. If there are 33 pins (including one empty key) at this connection, the board is a -35.

The Bally 6802 MPU board was only found in two games (Fireball Classic and Cybernaut) and in small quantities before the introduction of [[Bally_6803|6803 games]]. Some specifics of the 6802 board [http://www.pinball4you.ch/okaegi/pro_6802.html can be found here].
 

====Bally -35/Stern MPU-200 Parts Bill of Materials and Part Placement Chart====
[[File:CorrosionArea.jpg|300px|thumb|left|Bally -35/Stern MPU-200 Parts Bill of Materials|link=https://www.pinwiki.com/wiki/images/5/54/BallySternMPUPartsBOMandLocator.pdf]] 
Clicking on the thumbnail at left will open a .pdf file detailing the part location and complete bill of materials for Bally -35 and Stern MPU-200 MPU boards. The original parts "skeleton layout" and BOM was done by Ed at [http://www.greatplainselectronics.com Great Plains Electronics].
 

===Transformers===
{|class="wikitable"
! scope="col" | Manufacturer
! scope="col" | Part Number
! scope="col" | Power Transformer Module
! scope="col" | Rectifier Board Assembly
! scope="col" | Winding 1
! scope="col" | Winding 2
! scope="col" | Winding 3
! scope="col" | Winding 4
! scope="col" | Winding 5
|-
|Bally || E-122-125 || AS-2877, AS2877-1 || AS-2518-18 || 49VAC || 173VAC || 7.3VAC || 7.8VAC || 12VAC
|-
|Bally || E-122-131 || AS-2877-3 || AS-2518-49 || 49VAC || 173VAC || 7.3VAC || 9.2VAC || 12VAC
|-
|Bally || E-122-141 / AS-3071-2 || AS-2877-6 || AS-2518-54 || 49VAC || 170VAC || 6.5VAC || 8.2VAC || 14.2VAC
|-
|Bally || E-122-142 / AS-3071-2 || AS-2877-6 || AS-2518-54 || 49VAC || 170VAC || 6.5VAC || 9.4VAC || 14.2VAC
|-
|Bally || E-122-170 / AS-3071-15 ‡ || AS-2877-13 ‡ || AS-2518-151 ‡ || 49VAC || 170VAC || 8.5VAC || 20V CT † || 14.2VAC
|-
|Bally || AS-3071-12 § || AS-2877-11 § || AS-2518-132 § || || || || ||
|}

{|class="wikitable"
! scope="col" | Manufacturer
! scope="col" | Part Number
! scope="col" | Rectifier Board Assembly
! scope="col" | Lugs 2/4/6
! scope="col" | Lugs 8/10
! scope="col" | Lugs 13/14
! scope="col" | Lugs 15/16
! scope="col" | Lugs 17/18
|-
|-
|Stern|| 16B-3 || TA-100 || 49VAC || 173VAC || 7.8VAC || 12VAC || 7.3VAC
|-
|Stern|| 16B-6 || TA-100 || 49VAC || 173VAC || 7.8VAC || 12VAC || 7.3VAC

|}
† Center Tapped 
‡ Goldball and Grand Slam only. 
§ Baby Pacman and Granny & The Gators only

===Rectifier Boards===
====AS-2518-18 Schematic====
[[File:ClassicBallySternRectifierBoardSchematic.jpg|400px|left|thumb|Bally AS-2518-18 Rectifier Board Schematics]] 
Click on the image at left to show the schematic for the AS-2518-18 Rectifier Board (square board).
 
====Models====
The rectifier board is the first part of the power train in any Bally or Stern machine. In addition to rectifying four discrete AC voltages to DC, the rectifier board consists of the bulk of fuses for the game, including the main fuse. After all associated voltages are fused, the power is dispersed to the backbox, playfield, and lower cabinet.

There are two revisions of the AS-2518-54 rectifier board. The first revision has 5 fuses. Revision "B" has an additional fuse. On revision B, two fuses are used for the general illumination instead of just one fuse. One fuse is for the GI on the playfield, and the second fuse for the GI in the backbox. The AS-2518-132 rectifier board (used only in [[Baby Pac-Man]] and Granny & The Gators) is based on the AS-2518-54 revision B board.

The AS-2518-132 rectifier board is only used in Bally's two hybrid games--[[Baby Pac-Man]] and Granny & The Gators. The AS-2518-132 board backwards compatible with the AS-2518-54 board. However, in order to use a standard AS-2518-54 board in a hybrid game, the rectifier diodes at CR5, CR6, CR7, and CR8 need to be upgraded from the stock 3 Amp diodes to 6 Amp diodes.

<gallery widths=250px>
File:Bally AS-2518-18 Rec Brd.JPG|Bally AS-2518-18 Rectifier Board
File:Bally_-49_rectifier_board.jpg|Bally AS-2518-49 rectifier board
File:Bally AS-2518-54 Front.JPG|Bally AS-2518-54 Rectifier Board
File:Bally AS-2518-54 revision B.JPG|Bally AS-2518-54 Revision B Rectifier Board. Two fuses are used for the general illumination instead of one (the GI for the playfield and the GI for the backbox)
File:Bally_AS-2518-132.jpg|Bally AS-2518-132 Rectifier Board. Only used in Baby Pacman and Granny & The Gators.
File:Bally AS-2518-151 Rec Board.JPG|Bally AS-2518-151 Rectifier Board
</gallery>
 

<gallery widths=250px>
File:Stern TA-100 Rec Brd.JPG|Early Stern TA-100 Rectifier Board
File:Stern TA-100 Newer.JPG|Later Stern TA-100 Rectifier Board
File:Stern TA-100 Rec Brd Blank.JPG|Later Stern TA-100 Rectifier Board (blank)
</gallery>
 

====How To Hook Up a Bally AS-2518-18 Rectifier Board====
Often folks buy a new or used rectifier board and then when they get it, they realize that they have to hook it back up to the old wiring harness. If this is you, and you forgot to take notes or pictures before you removed your old board, then here you go. The photo below shows an original [http://stevekulpa.net/pinrepair/as-2518-18a.jpg AS-2518-18] rectifier board connected to a factory wiring harness. As far as I know, the wire colors are the same for ALL AS-2518-18 applications. 

[[File:As-2518-18-wiring.jpg|350px|left|thumb|Bally AS-2518-18 Rectifier Board (Solder Side)]]

{| class="wikitable" style="margin: 1em auto 1em auto;"
!Board Connection
!Wire Color / Gauge
!Transformer Lug
!Circuit
|-
|E1 || Red 18 AWG || 5 || Primary AC Hot
|-
|E2 || Yellow 18 AWG || 1 || Primary Neutral
|-
|E3 || Red 20 AWG || 2 || Solenoid Bus Hot
|-
|E4 || White/Red 20 AWG || 6 || Solenoid Bus Neutral
|-
|E5 || Green 20 AWG || 8 || Display High Voltage Hot
|-
|E6 || White/Green 20 AWG || 10 || Display High Voltage Neutral
|-
|E7 || Blue 18 AWG (2 wires) || 17 || GI Bus Hot
|-
|E8 || Black 18 AWG (2 wires) || 18 || GI Bus Neutral
|-
|E9 || Orange 18 AWG || 13 || Controlled Lamp Bus Hot
|-
|E10 || Green 18 AWG || 14 || Controlled Lamp Bus Neutral
|-
|E11 || White 20 AWG || 15 || 12V Input for 5-Volt Regulator Hot
|-
|E12 || White/Black 20 AWG || 16 || 12V Input for 5-Volt Regulator Neutral
|}
 
AWG = American Wire Gauge (18 = fat, 20 = skinny) 

"E" solder pads are labeled on the top side of the circuit board
 

====How To Hook Up a Stern TA-100 Rectifier Board====
[[File:Stern-ta100-16b-6.png|300px|left|thumb|Stern TA-100 Rectifier Wire Color connections]] 
As mentioned above when you replace or remove and reattach your rectifier board you need to know how to hook it back up. I have done this with a lot of Stern pins and made myself a chart for quick and easy reference when re-attaching the rectifier to the transformer. I figured it may be useful to others as well.
 

====How To Properly Mount a Bally AS-2518-54 Rectifier Board====
[[File:Bally-54mount01.jpg|200px|left|thumb|Bally AS-2518-54 Rectifier Board]]
[[File:Bally AS-2518-54 Back.JPG|200px|right|thumb|Bally AS-2518-54 Rectifier Board (back)]] 

The Bally AS-2518-54 rectifier board normally mounts on a large metal plate found in the bottom of the pinball machine’s cabinet. It uses the metal plate as a heat sink for the two large bridge rectifiers on the underside of the board, so mounting it properly is important. Carefully following the steps illustrated below will ensure the board is correctly mounted for long term reliability.
 

<center>
<gallery widths=300px heights=200px perrow=3 caption="Mounting a Bally -54 rectifier board">
File:Bally-54mount02.jpg|<center>Locate the two mounting holes for the bridge rectifiers, circled in red, and the seven mounting holes for the circuit board, circled in yellow.</center>
File:Bally-54mount03.jpg|<center>Practice laying the board in the proper position once, so you’re sure you know where it goes. You want the two holes that go through the bridge rectifiers to line up with the holes in the plate. Also make sure the mounting screws around the edge of the board are lining up with their holes too.</center>
File:Bally-54mount04.jpg|<center>Prep the surface of the mounting plate by cleaning the area, where the two bridges will mount, with some alcohol or acetone.</center>
File:Bally-54mount05.jpg|<center>Make a circle of heat sink grease around each bridge mounting screw hole approximately the diameter of a dime. Heatsink grease is available from most all the popular vendors.</center>
File:Bally-54mount06.jpg|<center>Carefully place the rectifier board in back on the mounting board. You want to get the board positioned as best as you can without moving it around a lot or you will smear the heat sink grease all over the place. What I like to do is peek through one of the two mount holes on the board and locate the corresponding screw hole on the plate. Then as you peek through this hole, guide the board into place while keeping the screw hole in sight.</center>
File:Bally-54mount07.jpg|<center>Double check your work, being careful not to move the board around too much. To avoid smearing the heat sink grease, it’s best if you can place it directly into the proper position the first time, without having to scoot it around afterwards.</center>
File:Bally-54mount08.jpg|<center>Next, start the two mounting screws that go through the bridge rectifiers, but do not tighten them all the way.</center>
File:Bally-54mount10.jpg|<center>Now locate and install the remaining seven mounting screws along the perimeter of the board, but don’t tighten them all the way yet. Since all the screws are a little loose, you have a little bit of board movement available to help locate the mounting screw holes on the plate.</center>
File:Bally-54mount11.jpg|<center>Once all the perimeter screws are in place, tighten the two bridge rectifier screws. You want them nice and tight so it spreads the heat sink grease into a nice, evenly spread thin layer. Just be careful that you don’t strip the threads out of the mounting holes. Then tighten up the perimeter screws after that. All done!</center>
File:Bally-54mount12.jpg|<center>One word of warning: The mounting screws protrude way past the bottom of the board, so be careful where you place this assembly. The screws may scratch your workspace (a nice table, countertop, etc.).</center>
</gallery>
</center>
 
====Pinout for Rectifier Board Connectors J1, J2, J3====
[[File:BallySternRectifierBoards.jpg | thumb | left| 300px| Diagram originally authored by PinSider Quench. Used by permission.]]
[[File:RectifierBoardsStern.jpg | thumb | right| 300px| Diagram originally authored by PinSider Quench. Used by permission.]] 
A frequently asked question when working on Bally and Stern rectifier boards is, "can someone post a picture of their wiring"?

These diagrams provide the wire colors and locations for Bally (left) and Stern (right) rectifier boards.

The original diagrams, plus an addendum regarding Bally Kiss, Space Invaders, and Future Spa (which used the AS-2518-49 rectifier board) can be found in the PinSide thread [https://pinside.com/pinball/forum/topic/bally-rectifier-board-j3-pinout-paragon here].

Note: Wire gauge is also indicated in each diagram. Thicker wires (for GI for example) are drawn thicker.
 

===Bally and Stern Solenoid Driver Board===
[[File:As-2518-16.jpg|200px|thumb|left|Bally AS-2518-16 Solenoid Driver/Regulator]]
[[File:As-2518-22.jpg|200px|thumb|right|Bally AS-2518-22 Solenoid Driver/Regulator]]
[[File:Stern-sdu100a.jpg|200px|thumb|left|Stern SDU-100 Solenoid Driver/Regulator]]
[[File:Stern-sdu100b.jpg|200px|thumb|right|Another style of the Stern SDU-100 Solenoid Driver/Regulator (Revision B)]]

First of all, everything mentioned in the following sections specifically reference the Bally AS-2518-22 solenoid driver board, found in most Bally pins from 1977 through 1985. Since the Bally AS-2518-16 and Stern SDU-100 boards are very similar, and all are identical as far as the operation of the solenoid driver circuits, the information is applicable to these boards as well. The main differences between Bally and Stern solenoid driver boards used from the factory are the physical layout of parts, and whether or not the board is single-sided or double-sided. Since the physically connector locations are the same, Bally and Stern solenoid driver boards are similar enough to be interchangeable. 

Secondly, if all this is Greek and you have no idea how decoder ICs work, or what a transistor is, take a look at the [http://www.pinwiki.com/wiki/index.php?title=Bally/Stern#How_Bally_Coils_are_Driven_for_Dummies How Bally Coils are Driven for Dummies] section to learn the basics of how things work. 

Third, the solenoid driver board actually has three functions.
#Drive the solenoid and relay coils of a pinball machine.
#Regulate the logic voltage which provides a nice and steady +5VDC to the other boards for their various logic circuits.
#Regulate the high voltage (+190 VDC) for the display driver boards

The regulated voltage will not be discussed here, only the solenoid drive section. 

Finally, don't forget that the Solenoid Driver board contains the high voltage circuitry for the displays. There is 190 volts DC here and if you're not careful, you'll get knocked on your butt. '''A shock from 190 volts DC will hurt.''' If you don't know what you're doing, stay away from it and have a professional fix it instead. In addition to high voltages, there are static sensitive parts on these boards. While working on boards, be sure to properly ground yourself before touching the board, and always work in a static-free workspace.
 

====Stern Driver Board Revisions====
There are several versions of the Stern SDU-100 driver board. Revision A is the most radically different than all the other versions, since it has a blue solder mask and hand-drawn traces. This revision can have either "Rev 1" or "Rev 2" printed on the board below the "SDU-100" label.

Revision B is marked as "B432" in the lower right hand corner. There is a lot of extra masking and labels on this board that are not seen on any other revisions.

Revision C is is marked as "Revision C" in the center of the board. A fuse was added for the high voltage section for the displays. However, this fuse was proven to be largely useless, and did not blow if there was a short in the high voltage section's regulation transistors.

The final revisions of the board lacked a fuse, but included a shutdown transistor in the high voltage section intended to cut the high voltage power if there is a short in this section (however, this is not always successful depending on where the short is). The later revisions went up to revision D, and possibly E or F, but this is currently unconfirmed.

<gallery widths=250px>
file:Stern-sdu100a.jpg|SDU-100 Revision A (Rev 1 and Rev 2)
file:Stern-sdu100b.jpg|SDU-100 Revision B (B432)
file:stern-sdu-100-rev-c-front.jpg|SDU-100 Revision C
file:placeholder.jpg|SDU-100 Revision D/E/F?
</gallery> 

====How Bally Coils are Driven for Dummies====
[[File:Ballycoil1.jpg|200px|right|thumb|Typical Bally Coil (Mata Hari)]] 
There are three main characteristics regarding the coils and coil connections in Bally games.
*Two large gauge yellow wires going to one lug (mostly two wires as the wire is "daisy chained" from coil to coil).
*One small gauge wire going to the other lug.
*A diode soldered across the two lugs, with the "banded" end of the diode facing the yellow wires (power).

The majority of information in this section is applicable to Stern games too. Bally and Stern solenoid driver boards are similar enough in overall design for them to interchange between games / manufacturers. The only other primary difference between Bally and Stern is the wire color of the solenoid bus line in most cases.
 

One lug on every coil is connected via a parallel circuit by the fatter wires. This type of connection is also commonly referred to as a daisy-chained circuit. These fat wires supply each coil with positive 43 volts DC (+43VDC), so each coil is connected to the +43VDC bus. Most have two fat wires, but some may only have one. Flipper coils have these wires too, but they are connected a little differently, and are discussed elsewhere. For now, just assume regular solenoids are being discussed here. 

Each coil has a small skinny wire on the other lug. This wire goes to the control circuits on the solenoid driver board. In order to energize the coil, there must be a path to ground for the +43VDC. In its at rest state, the coil does not have a path to ground. When the small skinny wire gets connected to ground, the path is complete and current will flow. This current flow turns the coil into an electro-magnet, which then pulls the plunger into the coil. When the wire is disconnected from ground, current flow stops, the electro-magnet is turned off, and the plunger returns to it's normal position with help from either a spring or gravity. 

Finally, there is a diode on each coil. When the current is quickly turned off on an energized coil, the magnetic field around the coil collapses quickly. This action causes the coil to generate a huge voltage spike. The job of the diode is to prevent the majority of this spike from reaching the solenoid driver circuity. If the diode is bad (shorted) or installed backwards, the drive transistor will be destroyed the very first time the coil is energized, then released. The process is similar to the ignition system used in older cars. When the points open, the 12 volts is removed from the car's coil quickly, which causes another coil to generate a huge voltage spike to the spark plug.
 

[[File:Ac-dc43.jpg|200px|left|thumb|Comparison of Electrical Sine Waves]] 
The computer program that runs the machine also tries to limit this spike by turning off the coil near the zero crossing of the AC line. This helps because the DC that drives the coils is rectified, but not filtered, so it's not smooth DC, but "humpy", as shown in the adjacent picture. 

By energizing the coils just after the zero crossing, the in-rush of current caused by a coil is limited. By turning the coils off just after the zero crossing, the voltage spike caused by the collapsing field is also kept to a minimum.
 

[[File:Bsoledraw1.jpg|200px|left|thumb|Depiction of Multiple Coils in a Bally Game with Manual Switches Inserted and tied to Ground]] 
So, in the simplest form, the solenoid driver circuits in a Bally game look like what is shown in the accompanying pic. Look at it as a bunch of coils all connected to the +43VDC bus, and the other lugs going to switches which are connected to ground. If a switch were to close, it would connect the circuit from +43VDC to ground, and the coil would energize as long as the switch is closed.
 

[[File:Bsoledraw2.jpg|200px|left|thumb|One Switch Closed and Energizing the Coil]] 
See how the circuit is complete due to the switch being closed, and the coil is energized. When the switch is opened again, the coil turns off, and is returned to the same state as the previous picture. If the diode were not there, there would be a big arc across the switch contacts upon the moment they opened up.
 

[[File:Bsoledraw3.jpg|200px|left|thumb|Depiction of Multiple Coils in a Bally Game with Transistors Shown]]
Now, take this one step further, and replace the manual switches with transistors. Transistors are normally used as amplifiers, but you can also use them as switches too. There are 3 leads on a transistor, the base, the emitter, and the collector. For NPN transistors like the ones on the Bally solenoid driver, the emitter and collector can be used like a switch. With no current supplied to the base, there is no current flow between the collector and emitter - the transistor switch is open, or OFF. If current is supplied to the base, the current will then flow between the collector and emitter, so now the switch is closed, or ON. 

Without getting into too much detail - what happens is a current is applied to the base which is high enough to 'saturate' the transistor. This means the collector-to-emitter current will be amplified as high as it can, and the transistor will then conduct a large amount of current from COLLECTOR to EMITTER, in relation to the current flow from the BASE to the EMITTER. This is how it acts like a switch. The base goes high to turn it on, and low to turn it off. Since the collector is connected to the wire that goes to the coil (the small single wire), and the emitter is connected to ground, turning the transistor has the effect of connecting the collector to ground. This completes the circuit to the coil and it turns on (fires).
 

A coil can be tested by momentarily grounding the tab on the coil's drive transistor. For the TIP-102 or similar transistors used in the Bally solenoid driver, the metal tab is connected to the collector. Knowing this, and what was just discussed, grounding the tab is the same as grounding the collector, which will complete the circuit to ground and fire the coil. However, this test only tests the wiring from the solenoid driver to the coil. It '''DOES NOT''' test the transistor itself or any circuitry before the transistor. 

The transistor and "control signal" in the simplified drawing above can be replaced with the actual circuit. More details regarding this circuit are found in the following section.
 

====Overview====
Two circuit boards will be discussed: the MPU board (AS-2517-17 or -35) and the Solenoid Driver board (AS-2518-22 or -16). The solenoid driver gets signals from the MPU board. These signals tell the solenoid driver which solenoid to fire. Up to 15 momentary and 4 continuous solenoids can be controlled by the solenoid driver. The flipper solenoids are enabled or disabled from the solenoid driver too, but are not controlled like the other solenoids.
 

====How the Solenoid Driver Works====
The solenoid driver is responsible for energizing the solenoid coils of the pinball machine. Four signals from the U11 PIA integrated circuit on the MPU board travel out from the J4 to the J4 connector on the Solenoid Driver board. These four signals tell the Solenoid Driver which solenoid to fire. This is accomplished by using a decoder chip that takes the binary pattern of the four signals (16 different patterns) and decodes (or demultiplexes) them into one of sixteen different outputs. The four signals are applied to the decoder then the decoder is strobed. Normally, all sixteen of the decoder output lines are held high (+5vdc). When strobed, the decoder lowers one of it's sixteen output lines, depending on the pattern of the four input signals. Detailed info about the 74LS154 decoder chip is availalbe [http://www.datasheetcatalog.org/datasheets/134/231586_DS.pdf here]. 

[[File:B_solenoid1.jpg|200px|thumb|left|Typical Solenoid Driver Circuit]]
With no input supplied (strobe is high), the output lines of the decoder are high (+5 vdc). This puts a voltage at the base of Q1 (this transistor is one of seven in the CA3081 transistor array chip). This turns Q1 "on" and the voltage supplied to it's collector via resistor R1 passes through the transistor to ground. At this point, little or no voltage is present at the base of Q2, and Q2 is "off". With Q2 off, the 40vdc at the coil has no place to go, and the coil remains deenergized. 

When the MPU board supplies the proper input signals (A-B-C-D) to the decoder, and the decoder is strobed (signal drops to low), the proper output signal will go low, which turns Q1 "off" (notice one of the two strobe lines goes to ground, so it's always low). This allows the +5vdc at Q1's collector to flow through the diode instead of Q1 on it's way to ground via resistor R3. This also puts a voltage at the base of Q2 and turns this transistor "on". When Q2 turns on, the 40vdc at the solenoid now has a path to ground through Q2 and current flows through the coil, thereby energizing it. Then the strobe to the decoder is released, the decoder output goes high again, Q1 turns on, Q2 turns off, and everything is back to normal.
 

Diode D1, resistor R3 and capacitor C1 work to slow the speed at which Q2 and the solenoid are able to turn off. This is important to prevent the "inductive kick" voltage that builds up when you try to turn off a solenoid quickly. A solenoid coil can build up hundreds of volts if it is switched off too quickly. For example, the spark in the spark plug of a car is generated from this inductive kick when the ignition coil is turned off quickly. In this case, D1 allows Q2 and the solenoid to turn ON quickly (which is OK) because the current that used to be flowing through Q1 can now flow forward through D1 and turn on Q2 quickly. However, when the decoder output goes back to high and Q1 turns back on, D1 prevents the charge from the base of Q2 from being sucked down Q1. The charge on C1 must drain off (slowly) through R3 and the base of Q2. This takes awhile and slows the turn-off of Q2 and the solenoid COIL, thus reducing the kick. Also, as the solenoid turns off and the voltage on the collector of Q2 starts to rise, this voltage is "fed back" by C1 to the base of Q2 and tends to keep Q2 on a little longer, slowing the turn-off of the solenoid even more. The OTHER diode (D2, across the solenoid) works to absorb the solenoid's turn-off kick by conducting when the voltage on the collector of Q2 is greater than about 40 volts.
 

====Pinout for Solenoid Driver Board Connector J3====
[[File:BallySolenoidDriverJ3ViaQuench.png | thumb | left| 300px| Diagram originally authored by PinSider Quench. Used by permission.]] 
A frequently asked question when working on Bally solenoid driver boards is, "can someone post a picture of their wiring"?

This diagram provides the wire colors and locations for Bally solenoid driver boards, connector J3 (25 pins, .100).
 

===Lamp Driver Board===
Bally and Stern controlled lamps are driven discretely via SCRs located on the lamp driver board. Because of this, neither manufacturer utilizes a lamp matrix. Any variation of the lamp driver boards are capable of controlling a maximum of 60 discrete lamp circuits. Typically the 2N5060 SCRs can only control one lamp, while the MCR106 / SCR106 / C106 SCRs can control up to two lamps. 

The first generation of both the Stern and Bally lamp driver boards has 4050 hex buffer chips installed between the 4514s and the MCR106 SCRs. It is unknown why both companies chose to remove these chips from later designs. 

<center>
<gallery widths=300px heights=300px perrow=3 caption="Bally Lamp Driver Boards">
File:Bally AS-2518-14 LDB.JPG|<center>AS-2518-14, Rev. 2</center>
File:Bally AS-2518-23 LDB.JPG|<center>AS-2518-23</center>
File:Bally AS-2518-23 LDB rev 1.jpg|<center>AS-2518-23, Rev. 1</center>
File:Bally AS-2518-23 LDB A000.jpg|<center>AS-2518-23, A000</center>
File:AS-2518-23PinsOnly.jpg|<center>AS-2518-23, A000, no header pin carriers</center>
File:AS-2518-23PinsOnlyPinsRemoved.jpg|<center>AS-2518-23, A000, with pins removed for replacement</center>
File:AS-2518-23PinsOnlyPinsReplaced.jpg|<center>AS-2518-23, A000, "pins only", replaced</center>
</gallery>
</center>
 
<center>
<gallery widths=300px heights=300px perrow=3 caption="Stern Lamp Driver Boards">
File:Stern LDA 1st Ver.JPG|<center>LDA-100</center>
File:Stern LDA-100 2nd Ver.JPG|<center>LDA-100 Rev. B</center>
File:Stern LDA-100 RevC.JPG|<center>LDA-100 Rev. C</center>
</gallery>
</center>
 
====Lamp Driver Board Connector / SCR Mapping====

{| class="wikitable sortable"
! SCR !! Connector !! Wire Color Code !! Wire Color !! SCR Type
|-
| Q10 || J1-15 || 13 || Red-Yel || MCR-106
|-
| Q22 || J1-10 || 32 || Yel-Blu || MCR-106
|-
| Q37 || J3-23 || 98 || Gry-Blk || 2N5060
|-
| Q60 || J3-03 || 81 || Blk-Red || 2N5060
|-
| Q11 || J1-16 || 12 || Red-Blu || 2N5060
|-
| Q26 || J1-07 || 34 || Yel-Grn || 2N5060
|-
| Q32 || J3-27 || 40 || Grn || 2N5060
|-
| Q54 || J3-11 || 20 || Blu || MCR-106
|-
| Q49 || J3-17 || 27 || Blu-Orn || MCR-106
|-
| Q06 || J2-14 || 12 || Red-Blu || 2N5060
|-
| Q19 || J2-15 || 32 || Yel-Blu || 2N5060
|-
| Q31 || J2-02 || 20 || Blu || 2N5060
|-
| Q45 || J2-01 || 60 || Brn || 2N5060
|-
| Q16 || J2-22 || 62 || Brn-Blu || MCR-106
|-
| Q14 || J1-18 || 58 || Wht-Blk || 2N5060
|-
| Q29 || J1-01 || 41 || Grn-Red || 2N5060
|-
| Q36 || J3-26 || 38 || Yel-Blk || 2N5060
|-
| Q57 || J3-01 || 10 || Red || 2N5060
|-
| Q12 || J1-19 || 60 || Brn || 2N5060
|-
| Q27 || J1-09 || 52 || Wht-Blu || 2N5060
|-
| Q38 || J3-25 || 36 || Yel-Brn || 2N5060
|-
| Q50 || J3-12 || 21 || Blu-Red || 2N5060
|-
| Q13 || J1-17 || 57 || Wht-Orn || 2N5060
|-
| Q28 || J1-08 || 51 || Wht-Red || 2N5060
|-
| Q44 || J3-19 || 67 || Brn-Orn || 2N5060
|-
| Q53 || J3-14 || 84 || Blk-Grn || 2N5060
|-
| Q39 || J3-24 || 72 || Orn-Blu || 2N5060
|-
| Q21 || J1-12 || 61 || Brn-Red || 2N5060
|-
| Q05 || J2-16 || 34 || Yel-Grn || 2N5060
|-
| Q18 || J2-20 || 35 || Yel-Wht || 2N5060
|-
| Q30 || J2-06 || 85 || Blk-Wht || 2N5060
|-
| Q43 || J2-07 || 91 || Gry-Red || 2N5060
|-
| Q52 || J3-13 || 13 || Red-Yel || 2N5060
|-
| Q51 || J3-15 || 53 || Wht-Yel || 2N5060
|-
| Q33 || J2-11 || 95 || Gry-Wht || MCR-106
|-
| Q15 || J2-23 || 97 || Gry-Orn || MCR-106
|-
| Q23 || J2-08 || 93 || Gry-Yel || MCR-106
|-
| Q58 || J3-02 || 95 || Gry-Wht || 2N5060
|-
| Q20 || J1-13 || 96 || Gry-Brn || 2N5060
|-
| Q03 || J2-21 || 47 || Grn-Orn || MCR-106
|-
| Q40 || J3-22 || 23 || Blu-Yel || MCR-106
|-
| Q46 || J3-18 || 56 || Wht-Brn || 2N5060
|-
| Q41 || J3-20 || 64 || Brn-Grn || MCR-106
|-
| Q17 || J1-11 || 65 || Brn-Wht || MCR-106
|-
| Q56 || J3-10 || 91 || Gry-Red || MCR-106
|-
| Q42 || J3-21 || 30 || Yel || MCR-106
|-
| Q47 || J2-10 || 98 || Gry-Blk || MCR-106
|-
| Q09 || J1-14 || 54 || Wht-Grn || MCR-106
|-
| Q34 || J1-02 || 43 || Grn-Yel || MCR-106
|-
| Q08 || J1-23 || 56 || Wht-Brn || MCR-106
|-
| Q01 || J1-24 || 50 || Wht || MCR-106
|-
| Q02 || J1-25 || 90 || Gry || MCR-106
|-
| Q07 || J1-27 || 53 || Wht-Yel || 2N5060
|-
| Q04 || J1-28 || 78 || Orn-Blk || 2N5060
|-
| Q35 || J1-03 || 45 || Grn-Wht || MCR-106
|-
| Q24 || J1-05 || 48 || Grn-Blk || MCR-106
|-
| Q25 || J1-06 || 25 || Blu-Wht || 2N5060
|-
| Q48 || J3-16 || 25 || Blu-Wht || MCR-106
|-
| Q59 || J3-04 || 14 || Red-Grn || 2N5060
|-
| Q55 || J3-09 || 15 || Red-Wht || MCR-106
|-
| Q23 || J1-04 || 35 || Yel-Wht || MCR-106
|-
| Key || J1-20 || -- || ---- || Key
|-
| N/U || J1-21 || -- || ---- || N/U
|-
| N/U || J1-22 || -- || ---- || N/U
|-
| Q53 || J2-03 || 84 || Blk-Grn || 2N5060
|-
| Q39 || J2-04 || 72 || Org-Blu || 2N5060
|-
| Q52 || J2-05 || -- || ---- || 2N5060
|-
| Q21 || J2-12 || 61 || Brn-Red || 2N5060
|-
| Q07 || J2-13 || 53 || Wht-Yel || 2N5060
|-
| N/U || J2-17 || -- || ---- || N/U
|-
| Key || J2-18 || -- || ---- || Key
|-
| N/U || J2-19 || -- || ---- || N/U
|-
| N/U || J3-05 || -- || ---- || N/U
|-
| N/U || J3-06 || -- || ---- || N/U
|-
| N/U || J3-07 || -- || ---- || N/U
|-
| Key || J3-08 || -- || ---- || Key
|-
| N/U || J3-28 || -- || ---- || N/U
|-
| Q40 || J2-09 || -- || ---- || MCR-106
|-
| Q03 || J1-26 || 91 || Gry-Red || MCR-106
|}
 

===Combination Solenoid / Lamp Driver Board===
Two different solenoid driver boards were used in some later games. Both of these solenoid driver boards are a combination solenoid driver board, lamp driver board, and where the +5v regulation. The difference between the two in essence is one has a high voltage section for displays, while the other does not.

====AS-2518-107 Combination Solenoid / Lamp Driver Board====
[[File:AS-2518-107.jpg|300px|left|thumb|Bally AS-2518-107 Combination Solenoid/Lamp Driver Board. This board integrates 5V regulation, along with lamp and coil drivers--all onto a single board.]] 
The AS-2518-107 board was used only in two games: Baby Pac-Man and Granny and the Gators. The reason for its development is that both games are hybrid pinball / video games with smaller playing areas. Therefore, neither game needed all of the overhead that a standard pinball had, and there were less solenoids (10). Likewise, the lack of a high voltage section on this board is because these games use video monitors and did not have plasma displays. It appears that there is a lesser amount of lamp drivers (30) also, however, that total is deceiving. The difference between this board and the previous lamp driver boards is that previous boards had one SCR per lamp drive. This board controls two lamps (multiplexed) per lamp drive. And the lamp drives do not control two lamps simultaneously at any given time. This gives the board a total of 60 controlled lamps.
 

====AS-2518-147 Combination Solenoid / Lamp Driver Board====
[[File:AS-2518-147_rev-b.jpg|300px|left|thumb|Bally AS-2518-147 Combination Solenoid/Lamp Driver Board. This board integrates 5V and display voltage regulation, along with lamp and coil drivers--all onto a single board. The photo is of Revision B of this board.]] 

The AS-2518-147 board was used only in two games: Gold Ball and Grand Slam. The reason for its development is assumed to be twofold. First, Bally was looking to cut costs, and this board would have done the job. Secondly, the board may have been used as a test transition between the now very old -35 boardset architecture and the next boardset (6803). The AS-2581-147 had a total of 11 solenoid drives. Likewise, there were what appeared to be less lamp drives (30). But, like the AS-2518-107 board, this board multiplexed the lamps. Again, two lamps can be controlled per lamp drive, but none of the lamp drives control two lamps simultaneously at any given time.
 

===Vidiot Board===
[[File:BLY_Vidiot.JPG|200px|thumb|left|Bally AS-2518-121 Vidiot Board (Note that some chips have been pulled from their sockets on this board)]]
[[file:bally-vidiot-deluxe-board.jpg|200px|thumb|right|Bally Vidiot Deluxe Board (Note that this board has been refurbished)]]
Bally created two Hybrid video/pinball games, [[Granny and the Gators]] and [[Baby Pac-Man]], which included a video game monitor and a pinball playfield. The Vidiot board is a special circuit board used to operate the video game portion and sounds of the hybrid games. However, each game used a slightly different Vidiot board. Baby Pacman used a "Vidiot Board", while Granny and the Gators used a "Vidot Deluxe Board". The two boards are not interchangeable.
 

===Miscellaneous Boards===
====Solenoid Expander Board (AS-2518-66)====
[[file:Solenoid_Expander.jpg|thumb|left|alt=alternative text|Bally Solenoid Expander board- Arrow indicates necessary bulb]] 
The Solenoid Expander board was used in several Bally games. Its purpose is to enable a particular coil or to multiplex several coils. It is typically driven by a lamp SCR on the lamp driver board versus a solenoid transistor on the solenoid driver board. However, at least Centaur and Centaur II are exceptions. Both games drive the solenoid expander board via the Q11 transistor on the solenoid driver board. 

There is a 555 bulb near (or sometimes not so near) that lights when the solenoid expander is activated. This bulb is essential for proper operation of the expander as the main opto isolator chip (MOC3011) on the expander board needs a load to work. Neither Centaur nor Centaur II use this bulb.
 

====Auxiliary Driver - GI Flasher (AS-2518-68)====
[[FILE:BallyA-2518-68.jpg|thumb|left|Placeholder for Bally Auxiliary Driver Board]] 
The auxiliary driver board is used on some Bally games to drive a triac, which in turn switches some of the general illumination on and off for effect. It is typically driven by a lamp SCR on the lamp driver board. The driven triac is typically located on a bracket which is attached to the rectifier board mounting plate in the bottom of the cabinet. 

Much like the solenoid expander board, there is a 555 bulb near the auxiliary driver board that lights when the auxiliary driver board is activated. This bulb is essential for proper operation of the auxiliary driver, as the opto isolator chip (MOC3011) on the board needs a load to work.
 

====Bally Strobe Board====
The Bally strobe board was used on Flash Gordon. A small transformer in the cabinet bottom provides the voltage required for this board. That power is fused by an "in-line" fuse at the small transformer.

There isn't much to go wrong with this board as it's comprised of a few diodes and resistors. Other than replacing the actual strobe lamp and the "trigger" transformer, parts are easy to find. Some folks have been successful using a strobe lamp acquired from Radio Shack. A source for the trigger transformer is unknown.

The trigger transformer should measure about 32 ohms between the pins marked 1 and 2, and about .2 ohms between the pins marked 3 and 4.

If your strobe is producing a very weak strobe, or not working at all, test the two 22uf/250V electrolytic capacitors. Simply replacing out of spec capacitors may bring the strobe back to life.

Another area for concern, as with all single sided PCBs is the header pins. Replacing these pins or simply reflowing the solder on them is a good idea as they are subject to cracked solder joints.

If working properly, the strobe will fire 4 times at game power up. It also strobes along with the controlled lamps during "all lamp" test. It obviously will strobe during game play too.
 

<center>
<gallery widths=200px heights=200px perrow=4 caption="Flash Gordon Strobe Board Components">
File:FlashGordonStrobeBoardFront.jpg|<center>Bally Strobe Lamp Board as found on Flash Gordon (front), with new 22uf capacitors.</center>
File:FlashGordonStrobeBoardRear.jpg|<center>Bally Strobe Lamp Board as found on Flash Gordon (rear).</center>
File:FlashGordonStrobe.jpg|<center>The "HAL-9000 like eye" strobe lamp as seen from the front of the lamp insert panel.</center>
File:FlashGordonSmallTransformer.jpg|<center>Small transformer and in-line fuse in cabinet bottom.</center>
</gallery>
</center>
 

====Stern IM-100 Flash Lamp Board ====

As part of Iron Maiden (1982) Stern utilized a prominent flasher lamp on the backbox lamp board, controlled by a unique aux lamp driver board part number IM-100.

However, Stern did not document the use of this strobe lamp as part of the game manual or schematics.

===Displays===
Here are some different types of Bally displays
<center>
<gallery widths=300px heights=200px perrow=3 caption="Bally 6 and 7 digit displays">
File:B-disp6-21.jpg|<center>AS-2518-21 6-Digit Display</center>
File:B-disp6-15.jpg|<center>AS-2518-15 6-Digit Display</center>
File:B-disp7-58.jpg|<center>AS-2518-58 7-Digit Display</center>
</gallery>
</center>
 

Here are some different Stern displays. Note that the DA-300 circuit board is deeper than any of the other display types.
<center>
<gallery widths=300px heights=200px perrow=3 caption="Stern 4, 6, and 7 digit displays">
File:Stern4display.JPG|<center>4-Digit Display</center>
File:Stern DA-100 6 Digit Display Dbl Sided.JPG|<center>DA-100 6-Digit Display (Double-Sided)</center>
File:Stern DA-100 6 Digit Display RevB.JPG|<center>DA-100 (Rev B) 6-Digit Display (Single-Sided)</center>
File:Stern DA-100 6 Digit Display Sng Sided.JPG|<center>DA-100 6-Digit Display (Single-Sided)</center>
File:B-disps2.jpg|<center>Different DA-100 6-Digit Display (Single-Sided)</center>
File:placeholder.jpg|<center>DA-300 (Rev A) 7-Digit Display</center>
File:Stern-display-da300-revb.jpg|<center>DA-300 (Rev B) 7-Digit Display</center>
File:S-disp7-300.jpg|<center>DA-300 (Rev C) 7-Digit Display</center>
</gallery>
</center>
 

====Bally 6-Digit Displays====
[[File:B-disp6.jpg|200px|left|thumb|A healthy Bally 6-Digit Display]] 
The following information is focused on the AS-2518-21 display. Since the AS-2518-15 display is interchangeable with the "-21" display, everything mentioned here will apply to both displays. 7-digit displays behave the same too, so this information will be helpful for those too. The only real difference is an additional digit enable signal, and some more electronics on the board to drive the 7th digit. 

If you could care less displays work, but are looking for information on how to repair them, then jump to the [http://pinwiki.com/wiki/index.php?title=Bally/Stern#Repairing_Bally.2FStern_Displays Repairing Bally Displays] article below. We'll also show you some ideas on how to keep your displays working properly.
 

[[File:B-disp15.jpg|200px|left|thumb|Example of a Bally AS-2518-15 6-digit display]]
[[File:B-disp21.jpg|200px|right|thumb|Example of a Bally AS-2518-21 6-digit display]] 
The two displays are a little different in the way the components are laid out. Regardless of the differences in appearance, they both perform the same function and are interchangeable with each other. The original display (at least the one mentioned in the Power Play Owner's Manual) is the "-21". The two shown here were upgraded with 1/2 watt 100K ohm resistors. A modification that should be done on all displays.
 

[[File:B-disps1.jpg|200px|left|thumb|Example of a Stern 6-digit display]]
[[File:B-disps2.jpg|200px|right|thumb|Example of a Stern 6-digit display]] 
Likewise, there are different versions of Stern 6-digit displays. These displays are interchangeable with all Bally and Stern games.
 

=====How the displays work=====
The way the display circuitry works is really quite interesting. Although the human eye can not detect it, at any given moment, each display is only showing one digit at a time. The program that runs on the machine's computer is changing the digits so fast that it is not visible. If you were to film the displays and play the film back in slow motion, you'd see all the displays showing the same digit, and it cycles through all six, from left to right. It just cycles so fast that your brain thinks the whole display is lit all the time. 

Each display has six digits, and upon closer inspection, each digit consists of seven segments. This is important stuff to know in order to understand how these displays work, and most important, how to fix them cheaply! 

There are 4 main "parts" of a display assembly:
*The glass display itself
*The display driver consisting of the input decoder
*The six digit driver circuits
*The seven segment driver circuits

There is one digit driver circuit for each of the six digits, and one segment driver circuit for each segment of a digit. How the actual glass display does what it does in order to light various digits and segments is beyond the scope of this tutorial. The decoder takes a number from 0 - 9 as input and determines which segments need to be energized in order to represent this number. The digit drivers are responsible for applying the proper voltages to the proper pins of the display to tell it which digit to light. The segment drivers are responsible for applying the proper voltage to the proper pins of the display to tell it which segments of the digit to light. It is the MPU's job to supply the proper signals to the display driver to make it do all this stuff. 

The decoder is a small integrated circuit (MC14543LE) called a "BCD To Seven Segment Decoder". This decoder happens to be a "latching" decoder, which means it latches onto its inputs and keeps them, even if they are no longer applied, until the decoder is told to release them (blanked). The decoder also has an input called a strobe. When strobed, the decoder will read it's four inputs and latch on to them. A strobe signal is usually a quick off/on/off pulse. There is also an input for the blanking signal. 

[[File:Dispchart.jpg|300px|left|thumb|Labeled Segments and Truth Table]] 
BCD stands for Binary Coded Decimal and is a fancy term for storing a number from 0 - 9 in a half byte of storage (four bits). Using BDC encoding, each byte of memory can store two digits. The input of the decoder is a BCD number from 0 - 9, and the output of the decoder is seven signals. These seven signals are either on or off, and relate to the seven segments of a digit. Each of the seven output signals go to a MPS-A42 transistor, which is part of a circuit called a segment driver. This transistor acts like a switch to turn the segments on or off. The outputs of the seven segment drivers go to the seven segment pins of the display glass. This is how the computer tells the display driver which segments to light. The MPU has a four-signal data path that goes to all five displays (or seven for Six Million Dollar Man). These four signals provide the 4-bit input into the decoder, and remember, all four signals go to ALL of the displays. Please see the diagram of how the segments are labeled, and a truth table showing the 15 possible inputs and outputs to the decoder. For those of you that don't know about binary arithmetic, you can get 15 possible combinations of on/off with 4 digits. (e.g., "0000", "0001", "0010", ..., "0111", "1111"). This is also how you count in binary, or base-2. Remember that the display driver is only interested in 10 of the 15 possible combinations, the ones that represent the numbers 0 - 9, or "0000" - "1001". Any other input combinations will result in unpredictable outputs from the decoder, so we label these as "don't cares", since we know they will never happen under normal circumstances.
 

The digit driver circuit consists of an MPS-A42 transistor and a 2N5401 transistor connected in a circuit that acts as a switch. Normally with no input signal applied, the switch is off, keeping the high voltage supplied by the HV Regulator away from the display. There are 6 digit signals provided by the MPU, one for each digit. The MPU will enable one signal at a time, telling the display driver which digit to operate. This signal will then turn on the "switch" for the digit, allowing the high voltage a connection to the proper pins of the glass display to energize the desired digit. These signals from the MPU are simply 6 wires and the MPU will activate one of them at a time. Like the segment signals, the six digit signals go to all of the displays in a daisy chain fashion. 

Before explaining how the computer makes all this work, let's summarize:
A display driver has four inputs from the MPU. The first is a collection of six signals used to tell the display driver which digit to energize (six digits in the display, six digit signals). Only one of these signals are on at a time. The second input is a collection of four signals that tell the display driver which number to display, in the form of segments. These four signals provide a binary pattern that is interpreted as a binary number from 0 to 9. The third input is a strobe signal, which tells the decoder to read it's inputs, and the fourth signal is a blanking signal, which tells the decoder to turn off all it's outputs. Also, but not mentioned above, are various voltages from the power supply and high-voltage regulator. Each display driver is supplied with +5VDC from the 5-volt regulator on the solenoid driver board. This is used to drive the logic circuits of the decoder. There is also +190VDC<nowiki>*</nowiki> applied to the display driver from the high-voltage regulator on the solenoid board. Finally there is a connection to ground, which brings all the voltages to the proper reference point. 

<nowiki>*</nowiki>For brand new displays, this voltage should be at +190VDC in order to "burn in" the display. Once a display has become used, this voltage may be backed down to +170VDC, which will work just fine and will help prolong the life of the display.
 

=====How The Computer Controls The Display=====
The next thing to understand is how the computer in the pinball machine operates the displays. For this section, referenced MPU board will be the AS-2518-17 module, but all this also holds true for the "-35" MPU module as well. And again, the Bally AS-2518-21 and AS-2518-15 Display Drivers will be referenced. The Stern style display drivers operate the same, and the six digit Stern drivers are 100% swappable with the Bally displays. There are a few minor differences between the seven digit varieties of displays preventing a direct swap without modifications. 

[[File:B-dispdiag.jpg|300px|left|thumb|Display Signals from MPU Board Illustrated]]
 
As mentioned above, there are four sets of signal lines that go from the MPU module to the display driver modules. The first set is the BCD data set which carry the display segment BCD data to all the displays on 4 wires. They leave the MPU module (A4) at connector J1, pins 25-28 and visit every display driver module at connector J1 and pins 16-19 (D4 - D0). The next set of signals is the digit enable signals. These 6 wires carry signals to all the display driver modules with information telling it which digit to light. The third set of signals are 5 latch strobe signals. There is one separate signal for each display driver, and it is the signal that tells the driver's decoder to read the decoder inputs, and output the proper segment signals. The final signal is a single single that goes to all the display drivers called Display Blanking. The signal tells the display driver's decoder to turn off all segment outputs, thereby blanking out the display, or turning all segments off.
 
[[File:BallySternDisplayInterruptCircuit.jpg|300px|right|thumb|Bally and Stern Display Interrupt Circuitry. The 555 timer is configured as a pulse generator.]] 
Once the machine has been turned on and has booted up, the processor on the MPU module is continuously running a program that is stored in the module's ROM chip(s). This program is responsible for controlling the game by reading all the switches, lighting all the lamps, activating all the solenoids, and controlling the displays. The program keeps a lot of information in RAM and uses this information to keep track of scores, switches, etc. An interrupt is a term for a section of computer program that interrupts the "main" program in order to execute a smaller program, sometimes referred to as a "service routine". We won't get into just how this actually happens, just be aware that the main program of a computer may be interrupted at any given time. And to make things even more complicated, interrupts themselves can be interrupted by higher priority interrupt service routines. There may be several different interrupts that occur in a pinball's computer program, but the one we want to study is the one that controls the displays. Keep in mind what was mentioned above, that at any given instant, only one digit is lit on any display. This is called multiplexing. 

320 times a second, or once every 3-1/4 milliseconds (thousands of a second), the CPU is interrupted to service the displays. In memory, the CPU keeps track of all the information it needs to operate all the displays. This information includes a counter used to indicate which display digit is active, the BCD data for all the displays, etc. Here's what the display service routine actually does: 

*'''Determine which digit was updated last time''' - The MPU looks at the digit counter and adds 1 to this value. If the new value is 7, it is changes to 1, then the new value is stored back into memory. Let's assume the new value is 4, so we're going to update the 4th digit.

*'''Blank out all the displays''' - The CPU raises the signal on the Blanking Line which causes all displays to go blank (the blanking signal tells all the decoders to turn off their segment outputs).

*'''Fetch the BCD data from memory''' - The BCD data for the first display, 4th digit is fetched from memory. 

*'''Send the BCD data to the display driver''' - This BCD data is placed on the BCD data bus and display #1 is strobed. This will cause the display's decoder to latch onto the input signals (store them for future use).

*'''Do it again''' - The previous two steps are repeated for the second, third, fourth, and fifth display.

*'''Enable the digit''' - The MPU then enables the 4th digit and disables the other 5 digits by raising and lowering signals on the Digit Enable lines.

*'''Finally, turn the digit on''' - The MPU lowers the signal on the Blanking Line, which causes the all of the decoders to output their proper segment signals and the 4th digit on each display is displayed.

*'''All done!''' - The interrupt service routine then exits and control returns to the main program

As you can see, the display interrupt service routine only handled 1 digit for all displays. Every time it is invoked, it will process the "next" digit, resetting the counter back to 1 when necessary. The process of updating 1 digit for all displays takes about 500 microseconds, or 1/2 of a millisecond, to complete. Pretty cool, eh? 

So, lets do some math. It takes 1/2 millisecond to update one digit, and since there are 6 digits, it takes 3 milliseconds to display all six digits. Since the interrupt runs 320 times a second, and it takes 6 interrupts to update the entire display, dividing 320 by 6 means that the displays are completely updated just over 54 times every second. That's fast enough to fool your eyes and brain into thinking the display is completely lit all the time. Also, since the interrupt routine takes about 1/2 millisecond to run, and it runs 320 times every second, that means about 160 milliseconds of every second of time is spent updating the displays, which is about 16 percent of the time.
 

===Bally Auxiliary Lamp Driver Boards===
[[File:Bally AS-2518-43 Aux Lamp.JPG|left|thumb|200px|Bally AS-2518-43 Aux. Lamp Driver Board]]
[[File:BLY aux lamp3.JPG|right|thumb|175px|Midway A084-91614-A000 Aux. Lamp Driver Board - same as AS-2518-43)]]

To increase the total of controlled lamps used in a particular game, Bally implemented auxiliary lamp driver boards. These aux. lamp driver boards were either used for effect (chaser or infinity lamps used between backglasses in games such as Xenon or Space Invaders), additional controlled insert lamps, or both (top rollover insert lamps and Queen's Chamber chaser lamps used on Centaur). 

There are essentially only two different boards used in games. The first is an AS-2518-43. This is the smaller footprint board, which has only one output connection. It is capable of driving 12 discrete circuits or a total of 24 lamps (12 sets of 2 lamps).
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
|-
! colspan=21 align='center' | Outputs for AS-2518-43 Aux. Lamp Driver Board
|-
!J2 Header
!1
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!19
!20
|-
| Output
|| <center>Q1</center>
|| <center>Q2</center>
|| <center>Q3</center>
|| <center>KEY</center>
|| <center>Q4</center>
|| <center>Q5</center>
|| <center>Q6</center>
|| <center>GND</center>
|| <center>GND</center>
|| <center>--</center>
|| <center>Q7</center>
|| <center>Q8</center>
|| <center>--</center>
|| <center>--</center>
|| <center>--</center>
|| <center>--</center>
|| <center>Q9</center>
|| <center>Q12</center>
|| <center>Q11</center>
|| <center>Q10</center>
|}

 
[[File:BLY aux lamp2.JPG|left|thumb|300px|Bally AS-2518-52 Aux. Lamp Driver Board]] 
The second board is the AS-2518-52. This board is narrower, yet longer in construction. It is capable of driving 28 discrete circuits or a total of 56 lamps (28 sets of 2 lamps). Either aux. lamp driver board receives the same inputs from the CPU board. Likewise, these signals are identical to the signals sent to the primary lamp driver board. The only differing signal between the primary lamp driver board and either aux. lamp driver board is the lamp strobe. The primary lamp driver board receives lamp strobe 1, while the aux. lamp driver boards receive lamp strobe 2.
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
|-
! colspan=21 align='center' | Outputs for AS-2518-52 Aux. Lamp Driver Board
|-
!J2 Header
!1
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!--
!--
|-
| Output
|| <center>--</center>
|| <center>--</center>
|| <center>KEY</center>
|| <center>Q2</center>
|| <center>Q7</center>
|| <center>Q6</center>
|| <center>Q1</center>
|| <center>Q3</center>
|| <center>Q5</center>
|| <center>Q4</center>
|| <center>Q9</center>
|| <center>Q14</center>
|| <center>Q13</center>
|| <center>Q8</center>
|| <center>Q10</center>
|| <center>--</center>
|| <center>Q12</center>
|| <center>Q11</center>
|| <center>--</center>
|| <center>--</center>
|-
!J3 Header
!1
!2
!3
!4
!5
!6
!7
!8
!9
!10
!11
!12
!13
!14
!15
!16
!17
!18
!19
!20
|-
| Output
|| <center>--</center>
|| <center>KEY</center>
|| <center>Q16</center>
|| <center>Q21</center>
|| <center>GND</center>
|| <center>GND</center>
|| <center>Q20</center>
|| <center>Q15</center>
|| <center>Q17</center>
|| <center>Q19</center>
|| <center>Q18</center>
|| <center>Q23</center>
|| <center>Q28</center>
|| <center>Q27</center>
|| <center>Q22</center>
|| <center>Q24</center>
|| <center>Q26</center>
|| <center>Q25</center>
|| <center>GND</center>
|| <center>GND</center>
|}
 

[[file:placeholder.jpg|thumb|left|200px|Grand Products 0200-700 auxiliary lamp driver board]]A third auxiliary lamp driver board was produced, but not by Bally. It was specific to the [http://www.ipdb.org/machine.cgi?id=403 301/Bulls Eye conversion kit] produced by Grand Products, Inc. It can sometimes be misidentified as a standard Bally AS-2518-52 aux lamp board because of its similar footprint and layout. However, it does not have any silkscreened text on the top of the board, the .156" pins are keyed differently, and it has an additional row of .100" header pins.
 

===Bally Sound Boards===
====Bally AS-2518-32 Sound Board====

[[File:As-2518-32.jpg| 180px | left |thumb | Bally AS-2518-32 Sound Board with 2 pots]]
[[File:Bally -32 Sound 3-Pot.jpg| 180px | right |thumb | Bally AS-2518-32 Sound Board with 3rd pot at R35]]
 

-32 Sound Board ROMs & Jumper Settings 
{| class="wikitable"
!Game
!U3 ROM
!Jumper Settings
|-
| Lost World ||  E729-18  ||  B 
|-
| Six Million Dollar Man||  E729-18  ||  B 
|-
| Playboy ||  E729-18  ||  B 
|-
| Voltan Escapes Cosmic Doom || ? || ?
|-
| Supersonic ||  E729-18  ||  B 
|}
Source: Bally / Midway 1982 parts catalog.
 

====Bally AS-2518-50 Sound Board====
[[File:As-2518-50.jpg| 180px | left |thumb | Bally AS-2518-50 Sound Board]]
 

-50 Sound Board ROM & Jumper Settings 
{| class="wikitable"
!Game
!U3 ROM
!Jumper Settings
|-
| Star Trek ||  E729-18  ||  B, D 
|-
| Kiss ||  E729-18  ||  B, D 
|-
| Paragon ||  E729-51  ||  B, C 
|-
| Harlem Globetrotters ||  E729-51  ||  B, C 
|-
| Dolly Parton ||  E729-51  ||  B, C 
|}
Source: Bally / Midway 1982 parts catalog.
 

====Bally AS-2518-51 Sound Board====
[[File:As-2518-51.jpg| 180px | left |thumb | Bally AS-2518-51 Sound Board]]

The AS-2518-51 sound board improved over earlier sound boards that only made tones and introduced the ability to produce sound effects.

This sound board has a single sound ROM labeled u4.

There is a single self-test push-button on the board, which has the ability to produce a tone or a series of sounds. However, not all game sound ROMs have the self-test feature available. Some ROMs will make the board beep only once, some ROMs will repeat a test sound, and other ROMs do not respond to the self-test button at all. To complete a successful self-test, a sound ROM with a self-test feature must be used. Note that when a sound ROM without a self-test feature is installed and results in an unresponsive self-test, this does not necessarily indicate a problem with the sound board or sound ROM. 

-51 Sound Board ROMs & Jumper Settings 
Jumper A is used when U3 is a 6802 and U10 (6810) is not installed. 
Jumper B is used when U3 is a 6808 and U10 (6810) is installed. 
Jumper C is used when U4 is 2K in size (9316B or 2716). 
Jumper D is used when U4 is 4K in size (2532 or 4732).

{| class="wikitable"
!Game
!U4 ROM
!ROM Size
!Jumper Settings
!Self-Test
|-
| Nitro Groundshaker || E776-14, E776-15 || 2K || B, C || No
|-
| Future Spa || E781-2, E781-5 (or sub with E781-13) || 2K || B, C || No
|-
| Silverball Mania || E786-8, E786-11 || 2K || B, C || Yes
|-
| Space Invaders || E792-2, E792-7 || 2K || B, C || No
|-
| Rolling Stones || E796-11, E796-19 || 2K || B, C || Yes
|-
| Mystic || E798-2, E798-5 || 2K || B, C || Yes
|-
| Viking || E802-2, E802-7 || 2K || B, C || Yes
|-
| Hot Doggin || E809-2, E809-7 || 2K || B, C || Yes
|-
| Frontier || E819-2, E819-9 || 2K || B, C || Yes
|-
| Skateball || E823-2, E823-14 || 2K || B, C || Yes
|-
| Speakeasy || E877-1 || 2K || B, C || ?
|-
| BMX || E888-02 || 4K || B, D || ?
|-
| Grand Slam || E895-? || 4K || B, D || Yes
|-
| Gold Ball || E896-? || 4K || B, D || Yes
|-

|}
Source for Jumper Information: Bally / Midway 1982 parts catalog.
 

====Sounds Plus Sound Board (AS-2518-56)====
[[File:BallySoundsPlus.jpg|200px|left|thumb| Bally AS-2518-56 Sounds Plus Board]] 
The Sounds Plus board was only used in Xenon and very early Flash Gordons. The Sounds Plus board has a daughter card called the Vocalizer that contains the roms and circuitry needed to generate speech.
 

====Vocalizer Speech Board (AS-2518-57)====
[[File:Bally Vocalizer.JPG|200px|left|thumb|Bally AS-2518-57 Vocalizer Board]]
[[File:BallyVocalizerAndSoundsPlus.jpg|300px|Right|thumb|Bally AS-2518-57 Vocalizer and Sounds Plus Boards Insitu]] 
The Vocalizer board was only used in Xenon and very early Flash Gordons. It is a complimentary board to the AS-2518-56 Sounds Plus board, and contains the numerous roms needed for an extensive speech vocabulary. 
 

====Squawk & Talk Sound Board (AS-2518-61)====
The Squawk & Talk (S&T) sound board was the first to offer sound and speech in one board to Bally games. It is probably the most intuitive sound board Bally offered too. Similar to the Bally MPU boards, the S&T uses an LED flashing system during board initialization. There are at least 4 variations of the board: -61, -61a, -61b and -61d. 

Some variations of this board have a J3 header connection located at the top upper left edge of the board. This connection was never implemented. Likewise, some boards are populated with a 2 x 20 pin .100" header connection located on the left edge of the board. This connection is marked on the schematics for the use of a vocalizer, which was never implemented. 

All of the different variations of this board should work on all games. The exceptions are Centaur and Centaur II. These two games must use the -61b board. The reason for this are the extra input/output connections at J2 (bottom right of board) needed for connection to the Say It Again board and the "FF" jumper which routes analog audio to the SIA board (or not). A standard -61 or -61a has a total of 6 header pins at J2, while the -61b has a total of 10 header pins. 

<center>
<gallery widths=300px heights=200px perrow=2 caption="4 Revisions of the AS-2518-61 Squawk and Talk Sound Board">
File:S&T AS-2518-61.JPG|<center>AS-2518-61 Squawk & Talk Sound Board</center>
File:As-2518-61a.jpg|<center>AS-2518-61a Squawk & Talk Sound Board</center>
File:SquawkAndTalk-61BRevision.jpg|<center>AS-2518-61b Squawk & Talk Sound Board. Note expanded connector at J2 (lower right).</center>
File:AS-2518-61D.jpg|<center>AS-2518-61d Squawk & Talk Sound Board installed in VECTOR.</center>
</gallery>
</center>
 

 

Squawk & Talk Jumper Settings 
[[File:SquawkAndTalkJumperAndTestPointLocations.jpg|200px|left|thumb|Bally Squawk & Talk Jumper Locations. Note that the -61B revision of the board contains a jumper FF located within the stack of resistors below the AD558. Neither the -61 or the -61a revision has this jumper.]] 

The first table below is a list of the Squawk & Talk jumper settings by game as specified in the 1982 Bally / Midway parts catalog. These jumpers reflect the original ROM configuration when the game was released. If you've changed your sound ROMs to 2716s or from 2532s to 2732s, see the second table below. 

*If using a 6808 CPU chip with a 6810 chip, install L, remove K
*If using a 6802 CPU chip, install K, remove L. The 6810 can be removed if using a 6802, but doesn't impede proper operation if left in place
*The 5 EE jumpers must be installed when the AY-3-8912 chip is not present.
*The -61B revision of the board has an FF jumper, located in the stack of resistors below the AD558. This jumper should be OUT when a "Say it again" board is used (ala Centaur). This jumper should be IN when a "Say it again" board is not used or connected. The jumper "short cuts" the path used when a SIA board is connected. If the jumper is OUT and a SIA board is not connected, then there is no path for the analog sound to reach final amplification by the TDA2002 at U8. 

{| class="wikitable"
!Game
!Original Jumper settings as shipped with factory configured ROMs
|-
| Flash Gordon ||  C, D, E, G, Q, S, U, W, Y, AA, H, DD, N, and L or K 
|-
| Eight Ball Deluxe ||  C, D, E, G, Q, S, U, X, Y, AA, H, DD, N, and L or K 
|-
| Fireball II ||  C, D, E, G, Q, S, U, X, Y, AA, H, DD, N, and L or K 
|-
| Embryon ||  C, D, E, G, Q, S, U, X, Y, AA, H, DD, N, EE, and L or K 
|-
| Fathom ||  C, D, E, G, Q, S, U, W, Y, AA, H, DD, N, EE*, and L or K 
|-
| Medusa ||  C, E, G, Q, S, U, W, Y, BB, D, H, DD, N, EE, and L or K 
|-
| Elektra ||  C, E, G, Q, S, U, W, Y, BB, D, H, DD, N, and L or K 
|-
| Centaur ||  C, E, G, Q, S, U, W, Y, BB, D, H, DD, N, EE, FF (if no SIA board), and L or K 
|-
| Rapid Fire ||  C, E, G, Q, S, U, W, Y, AA, H, EE, CC, M 
|-
| Mr. & Mrs. Pac-Man ||  C, D, E, G, Q, S, W, Y, U, AA, H, DD, N, and L or K 
|-
| Spectrum ||  C, D, E, G, Q, S, U, W, Y, BB, H, DD, N, EE, and L or K 
|-
| Vector ||  C, D, E, G, Q, S, U, W, Y, AA, H, DD, N, and L or K 
|}
Source: Bally / Midway 1982 parts catalog. 
''*''Note: Even though the parts catalog states otherwise, Fathom does use the EE jumpers. 
 

Squawk and Talk board jumper settings for various sized ROMs at U2 through U5
{| class="wikitable"
!ROM Size/Location
!     ALL    
!    U2    
!    U3    
!    U4    
!    U5    
|-
|  2716 or 9316 || <center>C, E</center> || <center>D, P</center> || <center>Q, T</center> || <center>U, X</center> || <center>Y, BB</center>
|-
|  2532 or 9332 || <center>C, E</center> || <center>D, G</center> || <center>Q, S</center> || <center>U, W</center> || <center>Y, AA</center>
|-
|  2732 || <center>C, E</center> || <center>F, P</center> || <center>R, T</center> || <center>V, X</center> || <center>Z, BB</center>
|}
 

====Say It Again Board====
[[File:SIA.jpg| 180px | left |thumb | Bally AS-2518-81 Say It Again Sound Board. ''Image courtesy of PinSider Victor Nash.'']]
The "Say It Again" sound board adds reverb to a Squawk & Talk sound and speech board. This board was only used on Centaur and Centaur II.
 

'''Board Theory of Operations'''

The Say It Again board is connected to the audio from Squawk and Talk board.

Jumper FF needs to be cut on the Bally Squawk & Talk board.

Sound from the Bally Squawk & Talk board exits from J2-9 via a shielded wire which is grounded at J2-10. It returns from the Say It Again board via J2-7 via another shielded wire which is grounded at J2-8.

The input on the Say It Again Board is via J2-6 with the shield grounded at J2-5. It is then processed through three op amp stages of a LM3900 at U1, then through a dual channel audio delay SAD4096 at U2.

The dual outputs are combined into one and pass through two more op amps LM3900 U3. The U4 4066 acts as an on / off switch. This board is turned 'off' by grounding J1-3.

There are two adjustments on the Say It Again board: Bias and Regen. The Bias adjustment minimizes distortion. The Regen or Regeneration adjustment sets the number of times the echo will repeat.

A detailed procedure for adjusting the Bias is in the Centaur and Centaur II manuals.

====Cheap Squeak Sound Board====
[[File:Bally Cheap Squeak.JPG|200px|left|thumb|Bally Cheap Squeak Sound Board A080-91603-XXXX or Midway P/N M-051-00114-XXXX]]
The Cheap Squeak was designed as a lesser expensive sound board. It only utilizes a 6803 microprocessor, which allows it to function without 6821 PIAs and external ram memory. This sound board is only capable of simple tones and sounds and no speech. 

The following -35 games use the Cheap Squeak:
*Black Pyramid
*Cybernaut
*Fireball Classic
*Kings Of Steel
*Spy Hunter
*X's & O's
 
Granny and the Gators, a -133 game also uses the Cheap Squeak. Lady Luck, a 6803 based game, also uses this sound board. 

At power up, the Cheap Squeak's LED will flicker briefly, then flash, flash again, then turn on and stay on. Once the LED stays on, it seems to turn itself off for certain sounds, and then turn back on. Likewise, it appears to idle with the LED on, when no sounds are playing. The LED May turn on and off when sounds are playing or idle, but this is not always the case. With some games (Kings of Steel, X's and O's, and Black Pyramid), after the sound board successfully boots, the LED remains on. 

There are differing results when pressing the self test button depending on the sound ROMs. For example, pressing the self test with Black Pyramid ROMs results in a differing tone played every time. While pressing self test with Kings of Steel or X's and O's ROMs, causes the sound board to play the same sound each time. 

'''Board Theory of Operations''' 
The 6803 (U1) microprocessor multiplexes A0-A7 with D0-D7, calling those signals AD0-AD7. The processor fetches information from the sound ROMs (both code to execute and sound clips) by placing address information on AD0-AD7 and strobing the processor's AS (address strobe) signal to the 74LS373 (U2), thereby latching the lower 8 bits of the address bus in the LS373. A8-A15 are used along with jumpers JW1 through JW12, to implement a memory mapped I/O scheme to address the 2 sound ROMs which can be 2532s, 2732s, or 2764s. A14 and A15 control the 74LS10 (a triple 3-input nand gate) to assert device selects to the ROMs. 

Note that the processor does not use the traditional R/W signal as it never "writes" to memory. Besides placing instruction address and data on the address and data busses, the processor reads sound selects via P20-P24 and writes sound data to the DAC via P10-P17. Think of these lines as PA1-PA7 of a 6821 or 6532. 

The 6803 is initialized by the MPU at power up into 6803 mode N. Once initialized and running, the sound ROM code running in the 6803 accepts sound signal commands and merely reads pre-formatted sound "clips" from the sound ROMs and then writes the data to the ZN429 (U6) digital-to-analog converter (DAC) 8 bits at a time. The DAC converts the digital data to an analog level which is presented to the amplifiers for output to the speaker(s). 

The board creates 5VDC on board by regulating 12VDC down to 5VDC. Unregulated 12VDC enters the board at J1-10. It is filtered by C8, C9, and C10. The inductor at L1 smooths the voltage somewhat. D6 (VR332, equivalent to a 1N5402), D7, and D8 drop the voltage by .5 - .7 volts (normal voltage drop across a diode). The 7805 at U9 further regulates the voltage down to 5VDC which can be measured at TP2 (TP3 is ground). 

This 5VDC is used to power the TTL logic ICs. The ZN429 DAC also uses this 5VDC as a voltage reference. To prevent the sound volume from fluctuating over the range of operating temperatures, the reference voltage is held constant by a "voltage divider biasing circuit" comprised of resistors at R22, R23, and R24, and a 2N5305 NPN transistor at Q7. This reference voltage is presented at pin 5 of the DAC. 

'''Test Points''' 
*TP1 should measure about 11VDC.
*TP2 is 5VDC.
*TP3 is ground.
*TP4 is the clock signal, provided externally by the 6803 for the purpose of synchronizing address and data read cycles.
*TP5 is the reset signal, which is also present on pin 6 of the 6803. 

Cheap Squeak ROMs & Jumper Settings 
[[File:CheapSqueak.jpg|180px|left|thumb|Bally Cheap Squeak Sound Board with Jumpers Highlighted]]

{|class="wikitable"
! scope="col" |  General EPROM Configuration 
! scope="col" |  Jumpers Connected 
|-
|  U3 & U4 using 2532s
|  J6, J9, J12
|-
|  U3 & U4 using 2732s
|  J7, J10, J11
|-
|  U3 ONLY using 2764 (works only for Cybernaut and X's & O's) 
|  J2, J4, J7, J11, J10*
|}

*Note: If J10 is already installed, leaving it in should cause no ill effects when only using a single 2764.
 
Sound ROM Configuration and Behavior by Game
{|class="wikitable"
! scope="col" |  Game 
! scope="col" |  EPROM Configuration Tested 
! scope="col" |  Jumpers Connected 
! scope="col" |  LED Boot Behavior 
! scope="col" |  SW1 Tune 
! scope="col" |  Boot Tune 
|-
|  Granny and the Gators 
|    
|    
|    
|    
|    
|-
|  Cybernaut 
|  U3 - 2764, U4 - nu 
|  J2, J4, J7, J11 
|  Flicker, Blink, Blink, On 
|  Space Ship Landing 
|  Ding followed by Decaying Buzz 
|-
|  X's & O's 
|  U3 - 2764, U4 - nu 
|  J2, J4, J7, J11 
|  Flicker, Blink, Blink, On 
|  Single Chime that decays 
|  Single Chime that decays 
|-
|  Spy Hunter 
|  U3 - 2732, U4 - 2732 
|  J7, J10, J11 
|  Flicker, Blink, Blink, On 
|  Cartoon Electrical Short Circuit 
|  Chime followed by Rising Laser 
|-
|  Lady Luck 
|    
|    
|  Flicker, Blink, Blink, On 
|  Explosion 
|   
|-
|  Black Pyramid 
|  U3 - 2732, U4 - 2732 
|  J7, J10, J11 
|  Flicker, Blink, Blink, On 
|  Random Pitched Chime 
|  Ding followed by Decaying Buzz 
|-
|  Kings of Steel 
|  U3 - 2732, U4 - 2732 
|  J7, J10, J11 
|  Flicker, Blink, Blink, On 
|  Bell 
|  Chime followed by Rising Laser 
|-
|  Fireball Classic 
|  U3 - 2732, U4 - 2732 
|  J7, J10, J11 
|  Flicker, Blink, Blink, On (assumed - please verify) 
|  Bell 
|  Chime followed by Rising Laser 
|}

After pressing the test switch (SW1), a sound is played, and then the board reboots itself. 
Note: Combining 2732 images into a single 2764 does not work for Black Pyramid, Fireball Classic, Kings Of Steel, or Spy Hunter.

====Bally Sound Board Pinouts====
NC = not connected, and verified. 
Not all N/U have been verified as NC. Some may actually be NC.
{| class="wikitable"
!Pin Connection
!AS-2518-32
!AS-2518-50
!AS-2518-51
!AS-2518-56 Sounds Plus
!AS-2518-61 Squawk & Talk
!AS-2518-61A Squawk & Talk
!AS-2518-61B Squawk & Talk
!A080-91603-C000 Cheap Squeak
!A080-91864-C000 Sounds Deluxe

|-
|J1-1
|Sol. Address A
|Sol. Address A
|Sol. Address A
|Sol. Address A
|Sound Select
|Sound Select
|Sound Select
|Sound Select
|Sound Select

|-
|J1-2
|Sol. Address B
|Sol. Address B
|Sol. Address B
|Sol. Address B
|Sound Select
|Sound Select
|Sound Select
|Sound Select
|Sound Select

|-
|J1-3
|Sol. Address C
|Sol. Address C
|Sol. Address C
|Sol. Address C
|Sound Select
|Sound Select
|Sound Select
|Sound Select
|Sound Select

|-
|J1-4
|Sol. Address D
|Sol. Address D
|Sol. Address D
|Sol. Address D
|Sound Select
|Sound Select
|Sound Select
|Sound Select
|Sound Select

|-
|J1-5
| +5VDC
| +5VDC
| +5VDC
| +5VDC
|N/U
|NC
|N/U
|N/U
|N/U

|-
|J1-6
|Ground
|Ground
|Ground
|Ground
|Ground
|Ground
|Ground
|Logic Ground
|Logic Ground

|-
|J1-7
|NC
|N/U
|N/U
|N/U
|Gen. Ill. Bus (6VAC)
|Gen. Ill. Bus (6VAC)
|Gen. Ill. Bus (6VAC)
|N/U
|Wired in game, but N/U in schematics, need info

|-
|J1-8
|Sol. Bank Select
|Sol. Bank Select
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt
|Sound Interrupt

|-
|J1-9
| +43V
| +43V
|N/U
|N/U
|N/U
|NC
|N/U
|N/U
|N/U

|-
|J1-10
|NC
|N/U
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated
| +12V Unregulated

|-
|J1-11
|Key
|Key
|Key
|Key
|Key
|Key
|Key
|Key
|Key

|-
|J1-12
|Sol. Address E
|Sol. Address E
|Sol. Address E
|Sol. Address E
|Sound Select
|Sound Select
|Sound Select
|N/U
|N/U

|-
|J1-13
|N/U
|N/U
|N/U (Spare Address Line)
|N/U (Spare Address Line)
|N/U
|NC
|N/U
|Earth Ground
|Earth Ground in schematics, not wired in game

|-
|J1-14
|Ground
|Ground
|Ground
|N/U (Ground)
|Ground
|Ground
|Ground
|Logic Ground
|Logic Ground in schematics, not wired in game

|-
|J1-15
| +43V Return (Sol. Ground)
| +43V Return (Sol. Ground)
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return
| +12V Unregulated Return

|-
|J1-16
|n/a
|n/a
|n/a
|n/a
|n/a
| +12V Unregulated Return
| +12V Unregulated Return
|n/a
|n/a

|-
|J1-17
|n/a
|n/a
|n/a
|n/a
|n/a
| +12V Unregulated
| +12V Unregulated
|n/a
|n/a

|-
|J1-18
|n/a
|n/a
|n/a
|n/a
|n/a
|N/U
|N/U
|n/a
|n/a

|-
!Pin Connection
!AS-2518-32
!AS-2518-50
!AS-2518-51
!AS-2518-56 Sounds Plus
!AS-2518-61 Squawk & Talk
!AS-2518-61A Squawk & Talk
!AS-2518-61B Squawk & Talk
!A080-91603-C000 Cheap Squeak
!A080-91864-C000 Sounds Deluxe

|-
|J2-1
|Speaker +
|Speaker +
|Speaker -
|Speaker -
|Speaker -
|Speaker -
|Speaker -
|Speaker -
|Speaker -

|-
|J2-2
|Speaker -
|Speaker -
|Speaker +
|Speaker +
|Speaker +
|Speaker +
|Speaker +
|Speaker +
|Speaker +

|-
|J2-3
|n/a
|n/a
|n/a
|n/a
|Key
|Key
|Key
|n/a
|n/a

|-
|J2-4
|n/a
|n/a
|n/a
|n/a
|Remote Volume Return
|Remote Volume Return
|Remote Volume Return
|n/a
|n/a

|-
|J2-5
|n/a
|n/a
|n/a
|n/a
|Speech Volume
|Speech Volume
|Speech Volume
|n/a
|n/a

|-
|J2-6
|n/a
|n/a
|n/a
|n/a
|Sound Volume
|Sound Volume
|Sound Volume
|n/a
|n/a

|-
|J2-7
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Reverb Audio In
|n/a
|n/a

|-
|J2-8
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Shield Ground
|n/a
|n/a

|-
|J2-9
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Audio Out
|n/a
|n/a

|-
|J2-10
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Shield Ground
|n/a
|n/a

|-
!Pin Connection
!AS-2518-32
!AS-2518-50
!AS-2518-51
!AS-2518-56 Sounds Plus
!AS-2518-61 Squawk & Talk
!AS-2518-61A Squawk & Talk
!AS-2518-61B Squawk & Talk
!A080-91603-C000 Cheap Squeak
!A080-91864-C000 Sounds Deluxe

|-
|J3-1
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Ground
|n/a
|n/a

|-
|J3-2
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Data
|n/a
|n/a

|-
|J3-3
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Clock
|n/a
|n/a

|-
|J3-4
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
| +5VDC
|n/a
|n/a

|-
|J3-5
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|Key
|n/a
|n/a

|-
|J3-6
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|PB3
|n/a
|n/a

|-
|J3-7
|n/a
|n/a
|n/a
|n/a
|n/a
|n/a
|PB2
|n/a
|n/a
|}

===Stern Sound Boards===
====Stern SB-100 Sound Board====
[[File:YT.png]] A demonstration of the sounds made by a fully populated SB-100 driven by "Nugent" ROMs can be found [https://youtu.be/iul4a1cGXO8 here].
[[File:Stern SB-100 Sound1.JPG|left|thumb|300px|Stern SB-100 Sound Board - 1st Generation]]
[[File:SternSB-100Schematics.jpg|right|thumb|300px|Stern SB-100 Sound Board - 1st Generation - Schematics]] 
The first generation SB-100 sound board was used on the earliest Stern games with electronic sound. These boards were fully populated, because in addition to electronic sounds, there was a (simulated) chimes option (typically dipswitch setting 23 on M-100 MPU boards). Although they will have higher pitched sounds, the first generation boards are compatible with all Stern games using the M-100 MPU board and electronic sounds. With some [[Bally/Stern#Adjusting_the_Sound_Quality_on_a_Stern_SB-100_board|modifications]], this board can be made to sound like the lower pitched 3rd generation board.
 

[[File:Stern_SB-100_Sound2.JPG|left|thumb|300px|Stern SB-100 Sound Board - 2nd Generation (less populated)]] 
The second generation SB-100 sound board was used on Stern games with electronic sound and no chime sound option (typically dipswitch setting 23 on M-100 MPU boards). Due to the lack of the optional chime sounds option, this board is less populated. Although they will have higher pitched sounds, the second generation boards are compatible with all Stern games using the M-100 MPU board and electronic sounds, which did not use the chime option. With some [[Bally/Stern#Adjusting_the_Sound_Quality_on_a_Stern_SB-100_board|modifications]], this board can be made to sound like the lower pitched third generation board.
 

[[File:Stern SB-100 C-1 Ver 3.JPG|left|thumb|300px|Stern SB-100 Sound Board - 3rd Generation (C-1 - less populated)]]
[[File:SternSB100C1.jpg|right|thumb|300px|Another image of the Stern SB-100 Sound Board - 3rd Generation (C-1 - less populated)]] 
The third generation SB-100 sound board was used on some of the last Stern M-100 games with electronic sound and no chime sound option. Like the second generation board, due to the lack of the optional chime sounds, this board is less populated. The difference with this board and the second generation board is that the component markings and through holes have been removed where components are no longer used. Although they will have lower pitched sounds, the third generation boards are compatible with all Stern games using the M-100 MPU board, which did not use the chime option. This board also shipped in the "standard" green PCB variety. This board is easily identified by the large "C-1" notation. Some test points are located in different positions compared to the first two generations, and TP8 has been deleted.
 

<center>
<gallery widths=300px heights=300px perrow=3 caption="Differences Found Between Different Versions of SB-100 Sound Board">
File:Stern SB-100 Full Pop Reset Line 74107 Front No Pullup.jpg|<center>Front side of 1st gen board in vicinity of 74107</center>
File:Stern SB-100 Full Pop Reset Line 74107 Front Pullup.jpg|<center>Modification found on /RESET line of 1st gen board</center>
File:Stern SB-100 Full Pop Reset Line 74107 Back.jpg|<center>Back side of 1st gen board in vicinity of incoming /RESET line and 74107</center>
File:Stern SB-100 Less Pop Reset Front.jpg|<center>Front side of 2nd gen board in vicinity of 74107. Note the addition of a 47Kohm resistor and 3.3uF 6v tantalum capacitor</center>
File:Stern SB-100 Less Pop Reset Line 74107 Back.jpg|<center>Back side Modification found on /RESET line of 2nd gen board. Unless J1 pin 25 is removed from the board, this will tie the /RESET line to the +5v.</center>
File:Stern SB-100 Early J1 Header Pin25.jpg|<center>Back side of 2nd gen board in vicinity of incoming /RESET line (J1 pin 25)</center>
File:Stern SB-100 C-1 Reset Line 74107 Front.jpg|<center>Front side of 3rd gen (C-1) board in vicinity of 74107. Note that service bulletin 11 has been implemented into the design of the board by this time. R93 (47Kohm 1/4W resistor) and C56 (3.3uF 6v tantalum cap) are not in the earlier boards original design, and are possibly not notated on the schematics.</center>
File:Stern SB-100 C-1 Reset Line 74107 Back.jpg|<center>Back side of 3rd gen board in vicinity of where incoming /RESET line used to be. +5V trace is directly tied to the top of R93.</center>
File:Stern SB-100 C-1 J1 Header Pin25.jpg|<center>Back side of 3rd gen board in vicinity of incoming /RESET line (J1 pin 25). The /RESET line is no longer used on the board.</center>
</gallery>
</center>

====Stern SB-300 Sound Board====
[[File:Stern_SB-300_Sound.JPG|left|thumb|180px|Stern SB-300 Sound Board]]
The Stern SB-300 sound board was used in all games which used the M-200 MPU board. The SB-300 is interfaced to the MPU board via the 34 pin J5 connector located at the top of the board.

Note that the sound board only uses pins 1-32 on its J1 connection. Some ribbon cables used were 2 - 16 pin connections, while others were 2 - 17 pin connections, or a combination of the two.

Make certain that pin 34 of the sound board is not connected to the MPU. Pin 34 on J1 of the sound board and pin 34 on J5 of the MPU board is the /IRQ signal. This signal is never used by the sound board. However, if it is connected to the MPU board from the sound board, it can sometimes cause the MPU to lock up or hang. Either bend pin 34 of J1 on the sound board away from the connector (if it is even connected), or snip the pin off completely.
 

=====Stern VSU-100 Speech Board=====
[[File:Stern_VSU-100.JPG|left|thumb|180px|Stern VSU-100 Speech Board]]
[[File:Stern Speech and Sound.JPG|right|thumb|180px|The Stern sound board and speech boards shown installed in a game]] 
The Stern VSU-100 speech board was used as a complimentary board to the SB-300 sound board. In other words, Stern never designed a sound board which was capable of both sound and speech. The speech synthesis is based on the S14001A speech chip. They are pricey, but still available.
 

===Speakers===
All Bally -35 and -133 games use a speaker, Bally -17 games do not. In some cases, games use more than one speaker. The early games use a very small, xxx ohm, low wattage speaker in the bottom of the cabinet.

[[File:Hot Hand Speaker.jpg|thumb|left|200px|Typical M-100 speaker from a Hot Hand. Note that the volume control is missing from this unit.]]
[[File:Seawitch Speaker.jpg|thumb|right|200px|Typical M-200 speaker from a Seawitch]] 
With the exception of the first four Stern M-100 games, which shipped with a 4-bar chime box, all others use a speaker. And most of them have the speaker mounted on a board, aimed at the coin door. The speaker is a 6-1/2", low wattage speaker, but has an odd impedance of 6.4 ohms.

The Stern M-200 games use a single speaker in the lower cabinet. It is a 6-1/2", 8 ohm, low wattage (some are marked 8W) speaker.
 

===Stern MAA-100 ROM Board===
For the first Stern solid state game, Pinball, a ROM board was initially used. It was also used in Stingray, as Stingray has the same ROM set as Pinball.

This board was mounted to the backbox and a harness connected the board to the MPU board at the top connector J5.

<gallery heights=250 widths=250>
File:Stern Pinball ROM Board.JPG|Stern MAA-100 ROM Board
file:Stern-maa-100-board.jpg|Stern MAA-100 ROM Board installed
file:Stern-stingray-backbox-maa-100-board.jpg|Stern MAA-100 ROM Board installed in Stingray
</gallery> 

===Jumper/ROM Info===
Jumpers are small zero ohm resistors or pieces of bare or insulated wire used to connect various points of an MPU board together to allow the board to utilize varying sizes and types of ROM/EPROM chips. Many of the logic gate chips on the MPU boards are used to steer address signals to the proper pins on the various U1-U6 chip sockets. If you have changed the jumpers and you cannot make the board boot with known good working roms, it is possible you have an addressing problem caused by one of the logic gate support chips. Always double check your jumper work by following the trace or schematic to the next point after the jumper; i.e. do not just measure continuity across the jumper. Go to the next point where the jumper connects and test between those points.

Be careful soldering to the pads, as they can be fragile. It is best to remove all the solder from the pad and insert the jumper fully into the via rather than just solder to the top. Soldering the jumper top and bottom will help with any cracked vias. Solder the jumpers to the top of the board where the jumper silk screening is printed rather than the back so that you can easily spot what type of rom chips the board is jumpered for.

All software for Bally/Stern boards can be reformatted into a 2x2732 configuration. It helps to understand how the original software is formatted to understand how to combine and pad the software to get different formats. Any board jumpered to take 2x2732 has its address ranges of U2 as $1000-$17FF (lower half) $5000-$57FF (upper half). The U6 ranges are $1800-$1FFF (lower half) and $5800-$5FFF (upper half).

If the game was originally 4x2716, U1=$1000-$17FF, U2=$5000-$57FF, U5=$1800-$1FFF, and U6=$5800-$5FFF. Thus, to combine this setup to work on a 2x2732 configuration, you would combine U1+U2 into U2.732 and U5+U6 into U6.732 using either your burner software, or the DOS command '''copy /b u1.716 + u2.716 u2.732'''.

If you need to use 2716 eproms but don't have any, you can use a 2732 eprom in its place by duplicating the data. Either use the DOS command '''copy /b rom.716 + rom.716 rom.732''' or load the data twice into your burner; depending on its software, you might change the buffer address by $800 (so the duplicate data loads after the first segment) or it might ask if you want to append the data to the existing buffer.

==== Bally AS-2518-35 or AS-2518-133 Jumper Info====
The following is a list or various ROM and EPROM combinations that can be used with the Bally -35 or -133 board and the associated jumpers and jumper cuts. The letter "E" has been eliminated on every jumper number after the first to save space. '''9332''' ROMS are the "Black" masked ROMS originally supplied by the factory and can be replaced with 2532 EPROMS without any modification to the original board, provided that board has not been altered.

{| class="wikitable"
|-
! U1 ROM
! U2 ROM
! U6 ROM
! MPU Jumpers in Numeric Order
! Jumper CUTS
|-
| '''9316'''
| '''9316'''
| '''9316'''
| '''E1-4,2-6,7-8,9-11,12-36,13-15,16a-19,31-32,33-34'''
|
|-
| '''2716'''
| '''74S474'''
| '''74S474'''
| '''E1-3,2-6,9-11,12-36,13-15,16a-18,31-32,33-35'''
|
|-
|
| '''2532 or 9332'''
| '''2532 or 9332'''
| '''E4-12, 7-8, 10-11, 13a-14, 16a-34, 29-33, 31-32'''
| '''E13-15'''
|-
|
| '''2532 or 9332'''
| '''2732'''
| '''E4-12,7-8,10-11,13a-14,16a-29,31-32,33-35'''
| '''E13-15'''
|-
|
| '''9316'''
| '''9316'''
| '''E2-6,7-8,9-11,12-36,13-15,16a-19,31-32,33-34'''
|-
| '''9316'''
| '''9316'''
| '''2716'''
| '''E1-4,2-6,7-8,9-11,12-36,13a-19,16a-18,31-32,33-35'''
| '''E13-15'''
|-
|
| '''2716'''
| '''9316'''
| '''E1-5,2-4,7-8,10-12,11-29,13a-14,16a-19,31-32,33-34'''
| '''E13-15'''
|-
|
| '''2716'''
| '''2716'''
| '''E1-5,2-4,7-8,10-12,11-29,13a-14,16a-18,31-32,33-35'''
| '''E13-15'''
|-
| '''2716'''
| '''2716'''
| '''2716'''
| '''E1-5,2-4,7-8,10-12,11-25,13a-14,16a-18,31-32,33-35'''
| '''E13-15'''
|-
| '''2716'''
| '''2716'''
| '''9316'''
| '''E1-5,2-4,7-8,10-12,11-25,13a-14,16a-19,31-32,33-34'''
| '''E13-15'''
|-
| '''2716'''
| '''2716'''
| '''2532 or 9332'''
| '''E1-5,2-4,7-8,10-12,11-25,13a-14,16a-34,29-33,31-32'''
| '''E13-15'''
|-
|
| '''2732'''
| '''2716'''
| '''E4-13a, 7-8, 10-11, 12-GND, 16a-18, 31-32, 33-35'''
| '''E13-15'''
|-
|
| '''2732'''
| '''2732'''
| '''E4-13a, 7-8, 10-11, 12-GND, 16a-29, 31-32, 33-35'''
| '''E13-15'''
|-
! '''U1 ROM'''
! '''U2 ROM'''
! '''U6 ROM'''
! '''MPU Jumpers in Numeric Order'''
! '''Jumper CUTS'''
|}

The -133 board was used in 3 games: Baby Pacman, Granny and the Gators, and Grand Slam. If you want to use a -133 board in a game that uses another board, you must change CR52 (a 1n4148 diode near J4) to a 2k resistor. If you want to use a -35 board in a game that requires a -133, change resistor R113 to a 1n4148 diode, banded end farthest away from J4. IMPORTANT: Before plugging the board in, measure the voltage at the MPU J4-15. If it is 6.3 VAC, this game requires a -133. If it is 43 VDC, the game requires the -35 configuration.

==== Bally AS-2518-17 and Stern MPU-100 Jumper Info====
The following is a list of various ROM and EPROM combinations that can be used with the Bally -17 or STERN MPU-100 board and the associated jumpers and jumper cuts. The letter "E" has been eliminated on every jumper number after the first to save space. '''9316'' ROMS are the "Black" masked ROMS originally supplied by the factory. The "-DASH" between numbers means to jump one point to the other, e.g. E 1-2 means jump E1 to E2. Some jumps are very close to each other, others are much farther away. Some cuts in the traces must also be made on the solder or component side of the MPU board, so read the NOTES section below carefully.

{| class="wikitable"
|-
! U1 ROM
! U2 ROM
! U6 ROM
! MPU Jumpers in Numeric Order
! Jumper CUTS
|-
|
| '''9316'''
| '''9316'''
| '''E1-2, 3-4, 6-7, 8-10'''
| '''Usual Factory Setting'''
|-
|
| '''2716'''
| '''9316'''
| '''E1-2, 3-4, 6-7, 8-10'''
| '''Cut & Jumper See Note A'''
|-
|
| '''2716'''
| '''2716'''
| '''E1-2, 3-4, 6-7, 8-10'''
| '''Cut & Jumper See Note B'''
|-
|
| '''2732'''
| '''NONE'''
| '''E6-7, 8-10'''
| '''Cut & Jumper See Note C'''
|-
|
| '''2732'''
| '''2732'''
| '''E1-2, 3-5, 6-7, 8-10'''
| '''Cut & Jumper See Note D'''
|-
| '''74S474'''
| '''74S474'''
| '''2716 or 9316'''
| '''1-2, 3-4, 8-9 Factory Setting for Freedom or Night Rider ONLY'''
|
|-
| '''2716'''
|
| '''2716'''
| ''' See Note E'''
| '''Freedom/Night Rider ONLY'''
|-
! '''U1 ROM'''
! '''U2 ROM'''
! '''U6 ROM'''
! '''MPU Jumpers in Numeric Order'''
! '''Jumper CUTS'''
|}

=====Notes to above Cut and Jumper Section=====
If a jumper combination is '''NOT''' listed in the chart above, this jumper must be cut or removed! Double check your work and verify that someone else has not modified the board before you begin the process. '''Incorrect''' jumper combinations will prevent the MPU from booting, showing a locked on MPU LED. This is a very common fault.

'''Note A, 2716 in U2, 9316 in U6''' 
In addition to the jumpers listed above, you must also make the following cuts and jumps to use this configuration.

#On the component side of the -17 or MPU-100 board, cut the trace that runs from U2 pin 18 to U3 pin 18. Do this where the trace passes between sockets U2 and U3.
#On the solder side of the -17 board, run a jumper from U2 pin 18, to U17 pin 11. 
#On the solder side of the -17 board, cut the trace going to U2 pin 21. 
#On the solder side of the -17 board, run a jumper from U2 pin 21 to U2 pin 24. 

'''Note B, 2716 in U2, 2716 in U6''' 
In addition to the jumpers listed above, you must also make the following cuts and jumps to use this configuration.

Make sure jumpers E1-2, E3-4, E6-7, and E8-10 are in place.
Note: Trace cuts were completed using a "ball" cutter in a Dremel. The "cut" is marked with a black marker.

'''Reference the left picture.'''

#On the solder side of the -17 board, cut the trace leading to U18 pin 4.
#On the solder side of the -17 board, connect U18 pin 5 to the trace you cut leading to U18 pin 4. It's easiest to run the wire from U18 pin 5 to the via ("trace thru dot") that connects to this trace. 

'''Reference the center picture.'''
<ol start="3">
<li>
On the solder side of the board, cut the trace leading to U2 pin 21.
</li>

<li>
On the solder side of the board, jumper from U2 pin 21 to U2 pin 24.
</li>
</ol>

'''Reference the right picture.'''
<ol start="5">
<li>
On the solder side of the board, cut the trace leading to U6 pin 21.
</li>

<li>
On the solder side of the board, jumper from U6 pin 21 to U6 pin 24.
</li>
</ol>

<center>
<gallery widths=300px heights=300px perrow=3 caption="Note B Cuts and Jumpers">
File:U18Jumper.jpg|<center>Solder Side Trace Reroute at U18 and "through hole" to U2, pin 18</center>
File:U2Jumper.jpg|<center>U2 Cut and Jumper from pin 21 to pin 24</center>
File:U6Jumper.jpg|<center>U6 Cut and Jumper from pin 21 to pin 24</center>
</gallery>
</center>

'''Note C, Single 2732 at U2''' for the early 1977 to 1979 games. 
This modification combines the two original 9316 ROMs at U2 and U6 into a single 2732 EPROM at location U2. This configuration works for the following Bally games. This modification should also work for early Stern games with two original 9316 ROMs at U2 and U6.

*Black Jack
*Bobby Orr Power Play
*Eight Ball
*Evel Knievel
*Mata Hari
*Night Rider

To combine the original 9316 (or 2716) U2 and U6 ROM images into a single 2732 U2 image, use this DOS command:

:COPY /B U2ROM.716 + U6ROM.716 U2COMBO.732

Make sure to use the "/b" switch when copying, as shown above. The command combines the two files into a single binary file.

Add the following cuts and jumpers to the -17 MPU to use this configuration.

'''Reference the left picture.'''

#Verify that jumper E6-E7 is in place. E8-E10 can remain in place or can be removed (i.e. "don't care") as it is only useful when U3 and/or U4 ROMs are used. Remove '''any''' jumpers at E1, E2, E3, E4, or E5. That is, remove all jumpers except E6-E7.

'''Reference the center picture.'''

<ol start="2">
<li>
On the solder side of the -17 board, find U18 pin 4. Cut the trace close to pin 4 as shown below. In the picture below, a blue/black dot marks the cut made with a Dremel "ball cutter" bit.
</li>

<li>
Scrape the solder mask from the trace leading to pin 4.
</li>

<li>
Tack solder one end of a short length of wire (or resistor lead) to the bare trace. Solder the other end to U18 pin 5. This connects U18 pin 5 to U2 pin 18. You may choose an alternate method. Just be sure to connect the trace from the "trace through hole dot" to U18 pin 5.
</li>
</ol>

'''Reference the right picture.'''

<ol start="5">
<li>
On the component side of the board, locate U2 pin 13 (top right hand corner of U2). Slightly higher and to the right is a via "trace through hole" with a trace running straight down. Cut this trace to separate the via from the trace. In the picture below, the blue/black dot marks the location to cut.
</li>

<li>
On the component side, jumper from the via noted in step 5 to pad E4 (red wire in picture below). This connects jumper pad E4 to U2 pin 21.
</li>

<li>
On the component side, notice the large '''GROUND''' trace that runs down the board just to the right of the ROM sockets. To the right of the U2 ROM socket, scrape the solder mask from this large ground trace and add a jumper wire from this trace to pad E3 (orange wire/white tracer in picture below. Note that in this instance, U3 was also removed and the ground pad of U3 is used as a jumper point). This connects U2 pin 20 to ground.
</li>

<li>
Use your multimeter to verify that continuity exists between jumpered points.
</li>
</ol>

<center>
<gallery widths=300px heights=300px perrow=3 caption="Note C Cuts and Jumpers">
File:-17MPUFrontAnnotated.jpg|<center>Component Side Jumper Locations</center>
File:-17BackSideJumperAnnotated.jpg|<center>Solder Side Trace Reroute at U18 and "through hole" to U2, pin 18</center>
File:-17FrontSideJumpers.jpg|<center>Component Side Cut (black dot) and Jumper Detail</center>
</gallery>
</center>

'''Note D, 2732 in both U2 & U6''' 
This is a popular modification to the -17 & MPU-100 board as it maximizes the ROM space available and can accommodate almost every game from this period.

In addition to the jumpers listed above,make the following cuts and jumps to use this configuration.
Make sure jumpers E1-2, E3-5, E6-7, and E8-10 are in place, & NO others are connected. It is a good idea to continuity check each of the necessary jumpers, '''BEFORE''' beginning work.

#On the solder side of the -17 or MPU-100 board, cut the trace that runs to U2 pin 21. 
#On the component side of the board, cut the trace that runs to U2 pin 18. Best place to do this is where the trace passes between sockets U2 and U3. Use a mulitmeter continuity setting to figure out the trace to cut, and mark it with a Sharpie to avoid confusion and cutting of the wrong trace. 
#On the solder side, jump a wire from U2 pin 18 to U2 pin 12. 
#On the solder side, jump a wire from U2 pin 21 to U9 (6800CPU) pin 24. 
#On the solder side of the board, cut the trace that runs to U6 pin 21. 
#On the component side of the board, cut the trace that runs to U6 pin 18. A good place to do this is where the trace passes between sockets U6 and U5. Use your DMM's continuity setting to figure out the trace to cut. 
#On the solder side, add a jumper from U6 pin 18 to U6 pin 12.
#On the solder side, jump a wire from U6 pin 21 to U2 pin 21 (this connects both U2 and U6 pins 21 to U9 pin 24). 
#On the solder side, cut the trace that runs to U17 pin 2. 
#On the solder side, cut the trace that runs to U18 pin 4. 
#On the solder side, add a jumper from U17 pin 2 to U18 pin 4.

<center>
<gallery widths=300px heights=300px perrow=2 caption="Note D Cuts and Jumpers">
File:Bally -17 2732 Convert Front.JPG|<center>Component side cut locations</center>
File:Bally -17 2732 Convert Back.JPG|<center>Solder side cuts and added jumpers</center>
</gallery>
</center>

'''Note E Bally Freedom and Night Rider ONLY''' 
These notes are for the Bally Freedom and Night Rider ROMs

These two games used an unique set of ROMs at U1 and U2. These are 74S474 or 7461
(512 byte) ROMs at U1 and U2, and a 9316 or 2716 (2K byte) at U6. According to Williams tech, they state that a U1 2716 EPROM and a U6 2716 EPROM can be used for these two games.If using a -17 or M-100 MPU with a U1 2716 EPROM and U6 2716 EPROM, there are some cuts and jumps required:

#Cut the trace from U1 pin 18 to U2 pin 18. 
#Cut the trace from U1 pin 21 to pad E7. 
#On the solder side, add a jumper from U1 pin 21 to U1 pin 24. 
#On the solder side, add a jumper from U1 pin 18 to U17 pin 11. 
#On the solder side, add a jumper from U1 pin 22 to U2 pin 22. 

==== Stern MPU-200 Jumper Info====
The following is a list or various ROM and EPROM combinations that can be used with the Stern MPU-200 board and the associated jumpers and jumper cuts. '''9316''' ROMS are the "Black" masked ROMS originally supplied by the factory, used on the first few MPU-200 games. Stern switched almost exclusively to a 4x2716 configuration sometime around Seawitch through the end of their run and various boards have been spotted in the wild that seem factory with 2x2732 configuration. Galaxy has been spotted with an oddball 3x9316 + 1x2716 configuration.

{| class="wikitable"
|-
!  U1 ROM 
!  U2 ROM 
!  U5 ROM 
!  U6 ROM 
!  MPU Jumpers in Numeric Order
!  Jumper CUTS 
|-
| ''' (empty)'''
| ''' 2716'''
| ''' (empty)'''
| ''' 2716'''
| ''' 2-3, 5-7, 13-14, 16-18, 23-25, 32-33, 34-35'''
| ''' All others'''
|-
| ''' 9316'''
| ''' 9316'''
| ''' 9316'''
| ''' 9316'''
| ''' 1-5, 2-6, 8-9, 12-13, 16-18, 19-20, 22-25, 26-28, 29-31, 32-33, 34-35'''
| ''' All others'''
|-
| ''' 9316'''
| ''' 2716'''
| ''' 9316'''
| ''' 9316'''
| ''' 2-3, 5-7, 8-9, 12-13, 16-18, 19-20, 22-25, 26-28, 29-31, 32-33, 34-35 '''
| ''' All others'''
|-
| ''' 9316'''
| ''' 9316'''
| ''' 9316'''
| ''' 2716'''
| ''' 1-5, 2-6, 8-9, 13-14, 16-18, 19-20, 23-25, 26-28, 29-31, 32-33'''
| ''' All others'''
|-
| ''' 2716'''
| ''' 2716'''
| ''' 2716'''
| ''' 2716'''
| ''' 2-3, 5-7, 9-10, 13-14, 16-18, 19-21, 23-25, 27-28, 29-30, 32-33, 34-35 '''
| ''' All others'''
|-
| ''' (empty)'''
| ''' 2732'''
| ''' (empty)'''
| ''' 2732'''
| ''' 1-2, 4-5, 13-15, 16-18, 24-25, 32-33, 34-35'''
| ''' All others'''
|-
! ''' U1 ROM'''
! ''' U2 ROM'''
! ''' U5 ROM'''
! ''' U6 ROM'''
! ''' MPU Jumpers in Numeric Order'''
! ''' Jumper CUTS '''
|}

To combine the 9316 or 2716 ROM images into the proper format 2732 images, use the following MSDOS commands.
*copy /b U1ROM.716 + U2ROM.716 U2Combined.732
*copy /b U5ROM.716 + U6ROM.716 U6Combined.732

Note that jumpers 32-33 and 34-35 control the clock speed of the MPU-200. To use an MPU-200 in a game that normally uses a Bally -17/-35 or a Stern MPU-100 board, you should remove these jumpers as they will cause the software to run faster. This isn't really a problem, but timings of sound events might be affected as well as other unforeseen consequences. If using a MPU-200 board in a Bally -17 or -35 or a Stern MPU-100 game, you should remove the 5101 RAM at U13, as it will not be accessed directly. (Some of the software depends on the values being read with the lower nibble high (1111 or $F) - they will load the byte expecting $1f for instance and if you leave U13 in, it will return either random values or more likely $10). If the chip or socket at U13 is bad, it can be ignored. This however is a waste of resources, as the MPU-200 board is hard to find and cannot be substituted by a -17 or -35 board [http://warpzonearcade.com/?p=415 without some modifications]. 

Additionally, if all 32 dip switches are turned off upon boot with an MPU-200, it will flash seven times and jump into self-test mode. This will toggle alternatively every solenoid, flashing controlled lamps, and test each digit on the score displays. At least one DIP switch must be on to avoid this. This is not a function of the board itself, just the software used. For example, if you put earlier stern software (previous to Meteor) or any Bally software in an MPU-200, it will not enter self-test with all dips off.

* To down-grade the MPU-200 to the older MPU-100, remove jumpers 32-33 and 34-35 (used on all Stern MPU-200 EPROM configurations), and remove the 5101 RAM chip from U13.

* The MPU-200, when jumpered for four 2716 EPROMS (U1,U2,U5,U6), will run Bally games using three 2716 (U1,U2,U6) ERPOMs.

* On a MPU-200 configured for four 2716 EPROMs (U1,U2,U5,U6), to run Bally games using two 2716 (U2,U6) EPROMs, change the MPU-200's jumpers E13-14 to E13-15, and E5-7 to E1-5.
 

====Using a single 2732 at U2 in a -35 MPU for Bally games originally released with a -17 MPU====

Bally games released with a -17 MPU can use a single 2732 at position U2 of a -35 MPU.

This includes the following games:
*Black Jack
*Bobby Orr Power Play
*Bow and Arrow
*Eight Ball
*Evel Knievel
*Freedom
*Mata Hari
*Night Rider

Install the following jumpers. 

E12-Gnd ...connects U2 /CE ~ Pin 18 to Gnd 
E11-E15 and E35-E16A ...connects U2 /OE ~ Pin 20 to /VUA-O2-A12 
E13-E9 ...connects U2 A11 ~ Pin 21 to A11 
E7-E8 ...connects U2 A9 ~ Pin 22 to A9 

Remove any jumper at E13A above U1. 
Other jumpers should be irrelevant. 

The original 2716 ROM images can be be combined using the DOS command:
copy /b U2.716+U6.716 CombinedU2.732

====Bally -35 2764 EPROM Conversion====

These instructions will convert a Bally -35 MPU to use a single 2764 EPROM. Colors in the table will match the wire colors in the example photos.
 

<table border="1" cellspacing="0" cellpadding="1" width="680">
<tr>
<th colspan="3" bgcolor="C0C0C0">Bally -35 MPU - 2764 EPROM Conversion Instructions</th>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>1.</td>
<td>Remove any PROMs or EPROMs from U1, U2, U3, U4, U5 and U6.</td>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>2.</td>
<td>
Bend out pins 1, 2, 27, and 28 on a 28 pin EPROM socket so we can solder wires to the pins and install it in socket U2 on the MPU. Pin 26 of the EPROM is not connected. I usually remove this pin from the socket but you can just bend it out and not connect anything to it.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>3.</td>
<td>
Ensure that there are no jumpers connected to E4, E13, E13a, E11, E9, E12, and E35.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>4.</td>
<td>
Connect jumpers E7 and E8. This connects EPROM A9 to CPU A9.
</td>
</tr>
<tr>
<td align=center width=20>5.</td>
<td width="5" bgcolor="red"></td>
<td>
Connect EPROM socket pins 1, 27 and 28 to +5V. I chose to use pin 24 of U3 as the source for +5V. This wire is RED in my examples.
</td>
</tr>
<tr>
<td align=center width=20>6.</td>
<td width="5" bgcolor="E89DB1"></td>
<td>
Connect EPROM pin 2 (A12) to jumper location E4 (A14). This wire is pink in my examples.
</td>
</tr>
<tr>
<td align=center width=20>7.</td>
<td width="5" bgcolor="black"></td>
<td>
Connect jumper location E12 to ground. I use the large ground trace closest to E12. That will connect EPROM CE to ground. This wire is BLACK in my examples.
</td>
</tr>
<tr>
<td align=center width=20>8.</td>
<td width="5" bgcolor="green"></td>
<td>
Connect jumper positions E9 and E13A. That will connect EPROM A11 to CPU A11. This wire is green in my examples. 
NOTE: There is an error on the Bally schematic which shows jumper position E13 connected in common with E13A. This is an error and E13A will need to be used for this step.
</td>
</tr>
<tr>
<td align=center width=20>9.</td>
<td width="5" bgcolor="yellow"></td>
<td>
Connect jumper position E11 to the side of resistor R14 closest to the EPROM socket. That will connect EPROM OE to the output of the gate at U17A. That is an enable that combines CPU A12, VMA and phase 2 of the clock creating an enable that we can use for our EPROM. We could also use jumper location E35 but R14 is closer and makes for a cleaner installation, in my opinion. This wire is yellow in my examples.
</td>
</tr>
</table>
 
<gallery widths=200px heights=100px perrow=3 caption="Bally -35 2764 EPROM Conversion">
File:PinWiki dash 35 2764 conversion 1.jpg
File:PinWiki dash 35 2764 conversion 2.jpg
File:PinWiki dash 35 2764 conversion 3.jpg
File:PinWiki dash 35 2764 conversion 4.jpg
File:PinWiki dash 35 2764 conversion 5.jpg
</gallery>

====Bally -17 And Stern MPU-100 2764 EPROM Conversion====
These instructions will convert a Bally -17 or Stern MPU-100 MPU to use a single 2764 EPROM. Colors in the table will match the wire colors in the example photos.

<table border="1" cellspacing="0" cellpadding="1" width="680">
<tr>
<th colspan="3" bgcolor="C0C0C0">Bally -17 And Stern MPU-100 - 2764 EPROM Conversion Instructions</th>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>1.</td>
<td>Remove any PROMs or EPROMs from U1, U2, U3, U4, U5 and U6.</td>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>2.</td>
<td>
Bend out pins 1, 2, 20, 23, 27, and 28 on a 28 pin EPROM socket so we can solder wires to the pins and install it in socket U2 on the MPU. Pin 26 of the EPROM is not connected. I usually remove this pin from the socket but you can just bend it out and not connect anything to it.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>3.</td>
<td>
Ensure that there are no jumpers connected to E3, E4, and E8.
</td>
</tr>
<tr>
<td align=center width=20>4.</td>
<td width="5" bgcolor="red"></td>
<td>
Connect EPROM socket pins 1, 27 and 28 to +5V. I chose to use pin 24 of U3 as the source for +5V. This wire is RED in my examples.
</td>
</tr>
<tr>
<td align=center width=20>5.</td>
<td width="5" bgcolor="E89DB1"></td>
<td>
Next we need to connect EPROM A12 (pin 2) to CPU A14 (pin 24 of U9). The problem is that there are no jumper locations on the -17 and MPU-100 that are connected to A14 so we have to connect directly to pin 24 of the Motorola 6800 (U9). One option is to run the wire over the top of the board to the back (solder side) but I wanted to make my conversions look as clean as possible so I use pin 20 of U3 as a through hole to get to the other side of the board. So we connect pin 2 of the EPROM to pin 20 of U3 on the components side of the board then connect pin 20 of U3 to pin 24 of U9 on the solder side of the board. This makes for a clean looking conversion on the components side of the MPU. If you're going to use this method you need to ensure that there are no jumpers connected to E8. This wire is pink in my examples.
</td>
</tr>
<tr>
<td align=center width=20>6.</td>
<td width="5" bgcolor="black"></td>
<td>
Connect EPROM pin 20 (CE) to ground. I like to use the large ground trace closest to the EPROM socket. This wire is black in my examples.
</td>
</tr>
<tr>
<td align=center width=20>7.</td>
<td width="5" bgcolor="yellow"></td>
<td>
Connect jumper E3 to the side of resistor R14 closest to the EPROM socket. That will connect EPROM OE to the output of the gate at U17A. That is an enable that combines CPU A12, VMA and phase 2 of the clock creating an enable that we can use for our EPROM.
</td>
</tr>
<tr>
<td align=center width=20>8.</td>
<td width="5" bgcolor="green"></td>
<td>
Connect EPROM pin 23 to jumper location E4. That will connect EPROM A11 to CPU A11. This wire is green in my examples.
</td>
</tr>
</table>

 
<gallery widths=200px heights=100px perrow=3 caption="Bally -17 and Stern MPU-100 2764 EPROM Conversion">
File:PinWiki dash 17 2764 conversion 1.jpg
File:PinWiki dash 17 2764 conversion 2.jpg
File:PinWiki dash 17 2764 conversion 3.jpg
File:PinWiki dash 17 2764 conversion 4.jpg
File:PinWiki dash 17 2764 conversion 5.jpg
File:PinWiki dash 17 2764 conversion 6.jpg
</gallery>

====Stern MPU-200 2764 EPROM Conversion====

These instructions will convert a Stern MPU-200 to use a single 2764 EPROM. Colors in the table will match the wire colors in the example photos.

NOTE: You may need to first convert your board to use [[#Stern_MPU-200_Jumper_Info|two 2732 EPROM]]s before applying this conversion. If you leave the board configured for another rom setup; you may note the board will not flash the diag LED.

<table border="1" cellspacing="0" cellpadding="1" width="680">
<tr>
<th colspan="3" bgcolor="C0C0C0">Stern MPU-200 - 2764 EPROM Conversion Instructions</th>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>1.</td>
<td>Remove any PROMs or EPROMs from U1, U2, U3, U4, U5 and U6.</td>
</tr>
<tr>
<td align=center valign=top width=20 colspan=2>2.</td>
<td>
Bend out pins 1, 27, and 28 on a 28 pin EPROM socket so we can solder wires to the pins and install it in socket '''U2''' on the MPU. Pin 26 of the EPROM is not connected. I usually remove this pin from the socket but you can just bend it out and not connect anything to it.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>3.</td>
<td>
Ensure that there are no jumpers connected to E2, E4, E5, E6, E10, E17, and E18.
</td>
</tr>
<tr>
<td align=center width=20>4.</td>
<td width="5" bgcolor="red"></td>
<td>
Connect EPROM socket pins 1, 27 and 28 to +5V. I chose to use pin 24 of U3 as the source for +5V. This wire is RED in my examples.
</td>
</tr>
<tr>
<td align=center width=20>5.</td>
<td width="5" bgcolor="E89DB1"></td>
<td>
Connect EPROM pin 2 to jumper location E10. This wire is pink in my examples.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>6.</td>
<td>
Connect jumper location E5 to E4.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>7.</td>
<td>
Connect jumper location E17 to E18.
</td>
</tr>
<tr>
<td align=center width=20 colspan=2>8.</td>
<td>
Connect jumper location E2 to E6
</td>
</tr>
</table>

 
<gallery widths=200px heights=100px perrow=3 caption="Stern MPU-200 2764 EPROM Conversion">
File:PinWiki MPU 200 2764 conversion 1.jpg
File:PinWiki MPU 200 2764 conversion 2.jpg
File:PinWiki MPU 200 2764 conversion 3.jpg
</gallery>

====Bally/Stern ROM Memory Map====

ROM images based on 2732 EPROMs are available on the net for all Bally and Stern machines so I'll give an example of the ROM memory map using these as the example. This is important to consider when doing single EPROM conversions because you will need to create a custom ROM image from original game code.

<table width=600 border=1 cellspacing="0" cellpadding="1">
<tr><th> ROM image</th><th> Memory Location (Hex)</th><th> Memory Location (Decimal)</th></tr>
<tr><td>U2 First half:</td><td>$1000-$17FF</td><td>(Decimal: 4096-6143)</td></tr>
<tr><td>U2 Second half:</td><td>$5000-$57FF</td><td>(Decimal: 20480-22527)</td></tr>
<tr><td>U6 First half:</td><td>$1800-$1FFF</td><td>(Decimal: 6144-8191)</td></tr>
<tr><td>U6 Second half:</td><td>$5800-$5FFF</td><td>(Decimal: 22528-24575)</td></tr>
</table>

====Creating A 2764 ROM Image From 2732/2532 ROM files====

This is one way to create a 2764 EPROM image.

<table border=1 border=1 cellspacing="0" cellpadding="1">
<tr><td>

<table width=700 border=0>
<tr>
<td width=5% valign=top>1.</td>
<td>Download the game code. Most should be available from [http://www.ipdb.org/ ipdb.org].</td>
</tr>

<tr>
<td valign=top>2.</td>
<td>Download Oliver's Vector home ROM files [http://www.pinball4you.ch/okaegi/p-vec2v05.zip here]. The archive will contain fsp.exe which we will use below to split the ROM images in half.</td>
</tr>

<tr>
<td valign=top>3.</td>
<td>Open a command (DOS) prompt and navigate to the directory where you unzipped the Vector home ROM file downloaded above. You will also want to have your 2732 game code images in this directory. What we are going to do is split the ROM images in half creating 4 new files. Here is the command syntax:

fsp U2_2732_image.bin U2_split
fsp U6_2732_image.bin U6_split

Where U2_2732_image.bin and U6_2732_image.bin are the names of the U2 and U6 ROM images and U2_split and U6_split are the prefixes for the output files.

We should now have files named U2_split-0, U2_split-1, U6_split-0 and U6_split-1.
</td>
</tr>

<tr>
<td valign=top>4.</td>
<td>Now we can issue this command to create our image:

copy /b U2_split-0 + U6_split-0 + U2_split-1 + U6_split-1 2764_ROM_Image.bin

The command above must be entered as one string.

This will create a file called 2764_ROM_Image.bin. Burn that to your EPROM and you're ready to go!
</td>
</tr>

</table>

</td></tr></table>

===Attract Mode Test Points===

====Rectifier Board Test Point Values====
{|class="wikitable"
|+ Bally
! scope="col" | Model
! scope="col" | TP1 (LAMPS)
! scope="col" | TP2 (DISPLAYS)
! scope="col" | TP3 (LOGIC)
! scope="col" | TP4 (GI)
! scope="col" | TP5 (COILS)
|-
|AS-2518-18 || +5.4 +/-.8VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC || 7.3 +/-.9VAC || +43 +/-5.4VDC
|-
|AS-2518-49 || +5.4 +/-.8VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC || 7.3 +/-.9VAC || +43 +/-5.4VDC
|-
|AS-2518-54 || +5.4 +/-.8VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC || 7.3 +/-.9VAC || +43 +/-5.4VDC
|-
|AS-2518-132 || || || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

{|class="wikitable"
|+ Stern
! scope="col" | Model
! scope="col" | TP1 (LAMPS)
! scope="col" | TP2 (DISPLAYS)
! scope="col" | TP3 (LOGIC)
! scope="col" | TP4 (GI)
! scope="col" | TP5 (COILS)
|-
|TA-100 || +5.4VDC || +230VDC || +11.9VDC || 7.3VAC || +43VDC
|}

====MPU Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
|-
|AS-2518-17 || +5 +/-.25VDC || +11.9 +/- 1.40VDC || +21.5 +/- 2.7VDC || GND || +5 +/-.25VDC
|-
|AS-2518-35 || +5 +/-.25VDC || +11.9 +/- 1.40VDC || +21.5 +/- 2.7VDC || GND || +5 +/-.25VDC
|-
|AS-2518-133 || +5 +/-.25VDC || +11.9 +/- 1.40VDC || || GND || +5 +/-.25VDC
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

====Lamp Driver Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
|-
|AS-2518-14 || Lamp Driver || +5 +/-.25VDC || GND || || ||
|-
|AS-2518-23 || Lamp Driver || +5 +/-.25VDC || GND || || ||
|-
|AS-2518-43 || Aux Lamp Driver || +5 +/-.25VDC || GND || || ||
|-
|AS-2518-52 || Aux Lamp Driver || +5 +/-.25VDC || GND || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

====Solenoid Driver/Regulator Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
|-
|AS-2518-16 || Solenoid Driver || +5 +/-.25VDC || +190 +/-5VDC || +5 +/-.25VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC
|-
|AS-2518-22 || Solenoid Driver || +5 +/-.25VDC || +190 +/-5VDC || +5 +/-.25VDC || +230 +/-27.4VDC || +11.9 +/- 1.40VDC
|-
|AS-2518-107 || Combo Lamp/Solenoid Driver || || || || ||
|-
|AS-2518-147 || Combo Lamp/Solenoid Driver || || || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

====Sound Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
! scope="col" | TP6
! scope="col" | TP7
! scope="col" | TP8
! scope="col" | TP9
! scope="col" | TP10
! scope="col" | TP11
! scope="col" | TP12
! scope="col" | TP13
|-
|AS-2518-32 || Sound || +5 +/-.25VDC || GND || +12.5 +/-1.3VDC || +43 +/-5.4VDC || SOL RET || N/A || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-50 || Sound || +5 +/-.25VDC || GND || +12.5 +/-1.3VDC || +43 +/-5.4VDC || SOL RET || N/A || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-51 || Sound || +11.9 +/- 2.5VDC || +5 +/-.25VDC || GND || 0VDC (No Sound), 2.5+/-.2VDC (Sound) || +2.5 +/-.2VDC || 0VAC (No Sound), .35 +/-.1VAC (Sound) || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-56 || Sound || +11.9 +/- 2.5VDC || +5 +/-.25VDC || GND || 0VDC (No Sound), 2.5VDC (Sound) || +2.5 +/-.2VDC || 0VAC (No Sound), .35 +/-.1VAC (Sound) || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-57 || Vocalizer || GND || +5 +/-.25VDC || Analog Output || Digital Input || Speech Clock || N/A || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-61 || Sound || GND || +5 +/-.25VDC || +11.5VDC || -5VDC || Speech Volume Control Voltage || Sound Volume Control Voltage || AY-3-8912 Output || E || TMS5200 Output || VMA || TMS5200 Clock || Reset ||
|-
|AS-2518-81 || Reverb || GND || || || Audio In || || || || || || || +11.9VDC || +12VDC || +4VDC to +8VDC
|-
|M-051-00114-B045 || Sound || || || || || || || || || || || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3 

{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
! scope="col" | TP4
! scope="col" | TP5
! scope="col" | TP6
! scope="col" | TP7
! scope="col" | TP8
! scope="col" | TP9
|-
|SB-100 || Sound || +5VDC || Frequency adjustment for R6 pot || Frequency adjustment for R2 pot || GND || Frequency adjustment for R13 pot || Vdd || +11.6VDC || +6.2VDC || +10VDC
|-
|SB-300 || Sound || Analog GND || +12VDC || +10VDC || +5VDC || Clock input for U18 || GND || N/A || N/A || N/A
|}

====Display Module Test Point Values====
{|class="wikitable"
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | TP1
! scope="col" | TP2
! scope="col" | TP3
|-
|AS-2518-15 || Display Module || +5 +/-.25VDC || +190 +/-5VDC || GND
|-
|AS-2518-21 || Display Module || +5 +/-.25VDC || +190 +/-5VDC || GND
|-
|AS-2518-58 || Display Module || +5 +/-.25VDC || +190 +/-5VDC || GND
|-
|AS-2518-121 || Vidiot || || ||
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3

===Fuse Values===
{|class="wikitable"
|+ Bally
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | F1
! scope="col" | F2
! scope="col" | F3
! scope="col" | F4
! scope="col" | F5
! scope="col" | F6
! scope="col" | F7
|-
|AS-2518-18 || Power Supply || 10A, 32V 3AG || 3/4A, 250V 3AG || 4A, 32V 3AG || 5A, 32V 3AG || 20A, 32V 3AG || 3A, 32V 3AG SB || N/A
|-
|AS-2518-22 || Solenoid Driver || 3/16A, 250V 8AG (can be modified to accept 3AG) || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-49 || Power Supply || 20A, 32V 3AG || 3/4A, 250V 3AG || 4A, 32V 3AG || 5A, 32V 3AG || 20A, 32V 3AG || N/A || N/A
|-
|AS-2518-54 || Power Supply || 20A, 32V 3AG || 3/4A, 250V 3AG || 4A, 32V 3AG || 5A, 32V 3AG || 20A, 32V 3AG || N/A || N/A
|-
|AS-2518-107 || Combo Lamp/Solenoid Driver || N/A || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-132 || Power Supply || || || || || || ||
|-
|AS-2518-147&dagger; || HV Lamp/Solenoid Combo || 3/16A, 250V 8AG (can be modified to accept 3AG) || N/A || N/A || N/A || N/A || N/A || N/A
|-
|AS-2518-151&dagger; || Power Supply || 6A, 250V 3AG || 5A, 250V 3AG || 3/4A, 250V 3AG || 8A, 32V 3AG || 8A, 32V 3AG || 8A, 32V 3AG || 8A, 32V 3AG
|}
Source: Bally Electronic Pinball Games Repair Procedures, F.O. 560-3 except &dagger;Source: [http://ipdb.org/files/1024/Bally_1983_Gold_Ball_Manual.pdf Bally Midway GOLD BALL Manual]

Unless noted as slow blow (SB), all fuses are fast blow.

{|class="wikitable"
|+ Stern
! scope="col" | Model
! scope="col" | Board Type
! scope="col" | F1
! scope="col" | F2
! scope="col" | F3
! scope="col" | F4
! scope="col" | F5
! scope="col" | F6
! scope="col" | F7
|-
|TA-100 || Power Supply || 10A, 32V 3AG || 3/4A, 250V 3AG, SB || 4A, 32V 3AG || 5A or 7A or 7.5A †, 250V 3AG, SB || 20A, 32V 3AG || 3A, 250V 3AG, SB || N/A
|-
|}
Unless noted as slow blow (SB), all fuses are fast blow.

† Games that use a 16B-6 transformer & MPU-200 may take a 5A, 7A, or 7.5A fuse at F4, as specified on each individual game's schematics.

{|class="wikitable"
|+ Stern TA-100 F4 Fuse Values
! scope="col" | Game
! scope="col" | F4 Fuse Value
|-
| Ali || 5A
|-
| Big Game || 7.5A
|-
| Catacomb || 7A
|-
| Cheetah || 7A
|-
| Cue || ?
|-
| Dragonfist || 7A
|-
| Flight 2000 || 7A
|-
| Freefall || 7A
|-
| Galaxy || 5A
|-
| Lightning || 7A
|-
| Meteor || 5A
|-
| Nine Ball || 7A
|-
| Orbitor 1 || 7A
|-
| Quicksilver || 7A
|-
| Seawitch || 7A
|-
| Split Second || 7A
|-
| Star Gazer || 7A
|-
| Viper || 7A
|-
|}

 

Various Bally and Stern games have under playfield fuses as well. A common symptom of a blown playfield fuse is flippers operational, but no other on playfield solenoids work. This is because the flippers draw too much current for the under playfield fuse (which is usually 1 or 2 amp), so they are connected before the fuse is in the circuit. The main solenoid fuse on the rectifier board is used to protect against a shorted flipper coil instead.

Sometimes a large under playfield mechanism will be fused separately. Gottlieb did this often, but it is rarer in Bally/Stern games. Examples of the games with auxiliary fuses under the playfield are Silverball Mania and Eight Ball Deluxe. If you have a solenoid not working it doesn't hurt to check and see if it has a fuse, or if someone decided to add one in the past. The under playfield solenoid fuse is a very small value, as for the most part Bally/Stern games are only able to fire one solenoid at a time. This is a limitation of the hardware design, as the 4-to-16 decoder chip on the solenoid driver board can only decode one of 15 signals to fire an associated solenoid.

Some games do utilize the remaining 4 continuous drivers for a momentary coil. (One example is the ball walker area in Flight 2000 - the 2 kickers are activated by the continuous solenoids, for a momentary period). You should identify which under playfield solenoids if any are used as such in your game and add a fuse to the activation (single, thinner wire) side of the coil to prevent a software glitch from locking on that coil. Simply splice it inline with the single wire and use a 1 amp fast blow fuse to protect the driver circuit and coil in the case of a lockup. It would only be necessary to add the fuse for large loaded coils - relay or high resistance coils like on a flag gate or pop-up post coil relay do not place such a great load on the driving transistor that it is in any danger of burning out.

Weak playfield solenoids can be caused by a weak connection on the under playfield fuse holder. Remove the fuse and check for proper tension on the fuse clips for any tarnishing. It is best to just replace suspect fuse holders with new vs. attempting to clean the originals.
 

===Proprietary Numbers on Chips===
Some Bally IC chips are marked with proprietary Bally part numbers, and no other markings are present. Below is a list of some of the most common chips found on Bally boards, and the more commonly referred to chip.
*620-28 - 6800 CPU chip
*620-29 - 6820 PIA chip
*620-30 - 6810 RAM chip
*620-37 - 14514 / 4514 CMOS 4-Bit Latch / 4-to-16 Line Decoder chip
*620-38 - 14534 / 4543 CMOS BCD-to-Seven-Segment Latch / Decoder / Driver chip
*620-39 - 74L154 4 to 16 decoder chip (can sub with 74HCT154)
*620-125 - 6808 CPU chip
 

===Flippers===
====Identification of Different Flipper Assemblies====
<center>
<gallery widths=225px heights=300px perrow=4 caption="Bally & Stern Flipper Assemblies">
File:BallyStarTrekFlipper.jpg|<center>Early Bally Flipper mechanism from a 1978 Star Trek</center>
File:BallyMedusaFlipper.jpg|<center>Later Bally Flipper mechanism from a 1981 Medusa. Commonly referred to as "linear flippers". Note-Double EOS switch for Upper Zipper Flipper</center>
File:SternDraculaFlipper.jpg|<center>Early Stern Flipper mechanism (Generation 1) from a 1979 Dracula. Note-Double EOS switch for Upper Flipper</center>
File:SternSeawitchFlipper.jpg|<center>Later Stern Flipper mechanism (Generation 2) from a 1981 Star Gazer</center>
</gallery>
</center>
 

===Accessing Bookkeeping and Diagnostic Modes===
<center>
<gallery widths=200px heights=200px perrow=3 caption="Bally and Stern Coin Door Test Buttons">
File:Bally-coin-door-switches.jpg|<center>Bally -17 and -35 Coin Door Test Button (L:Early -17, R:Late -35)</center>
File:Stern-coin-door-switches.jpg|<center>Stern -100 Coin Door Test Button (L:Early, R:Late)</center>
File:Stern M-200 Coin Door.JPG|<center>Stern -200 Coin Door Buttons</center>
</gallery>
</center>
 

 

The game must be working properly for the test button to function at all. The test button is not within the game switch matrix. It merely grounds pin 1 of MPU connector J3, (note that the ground wire for this switch connects to the solenoid driver board at pin J2-7, not the MPU board as one would expect). The switch itself is surprisingly resilient to beer/soda. Most failures of continuity to the MPU circuitry are due to either the connector pin in the female housing, or due to fractured solder joints on the male header.

With the exception of Stern -200 based games, pressing the test button the '''first''' time will enter the lamp test. All cpu controlled lamps will flash on and off including backbox lamps. This test will put the greatest load on the rectifier bridge as well as the connectors, enabling you to see "weak" connections.

Pressing the button for the '''first''' time with a Stern -200 based game will start a "burn in" test (lamps, displays, and solenoids will all be tested at the same time).

The '''second''' press of the test button will bring you into display test. Digits from 0-9 will appear on all displays in sequence, enabling inspection of the display elements. This test will not assist in some problems that can occur in displays concerning digit decoding, nor problems where one display ghosts its information onto another, as all displays are displaying the same information. Some games will "walk" an eight across the displays in a sequence enabling issues with decoders to be determined.

The '''third''' press of the test button will start a solenoid test. For Bally games, only the solenoids installed in that particular game will be tested, with their corresponding number showing on the displays. Most Stern games will test all solenoid driver circuits regardless of if they are utilized in that game or not. For this reason, it is desirable to test a solenoid board with Stern software to be able to test all components of the solenoid drive circuit (especially if you are fixing a board foreign to your game). After all solenoids are tested, Stern games will test the sound board during solenoid test, while Bally games will not.

With Bally -17 games and all Stern games, the '''fourth''' press of the test button will start a switch test. The lowest numbered stuck or closed switch will show in the displays. If there are no stuck switches a zero will show in the match display. NOTE: Multiple closed switches will NOT display anything other than the lowest numbered switch. This can be an issue with various switch matrix diode problems, as the switch displayed as closed may not be the switch with a problem. There is a special test rom available that will show ALL closed switches in a sequence similar to how Williams' machines did so. The special test ROM can be downloaded [https://www.pinwiki.com/wiki/images/0/05/Sco_testrom8.zip here].

With Bally -35 games, the '''fourth''' press of the test button will initiate a sound test. The same sound will be played repeatedly until the test is exited.

The '''fifth''' press of the test button will start switch test with Bally -35 games, and start the audits/settings with all other games. Regardless, subsequent presses will get you into audit/adjustment mode; you will see an 01 in the match display when you are at the first adjustment.

==First Things First (WIP)==
As exciting as it may be to acquire a pinball machine, there are several things which should be done before turning one on, or even plugging it in for that matter. It may have been plugged in where it was purchased, but there may be some hidden issues looming inside the game. Following this systematic approach should be very beneficial.

===Keep Game Unplugged Until Further Notice===
When fixing a game of unknown origin, it is best to initially keep it unplugged. There are several things which should be inspected on game, and these things require the game to be unplugged. While it's unplugged, make certain that the 3-prong is present on the line cord, and is actually connected to the earth ground of the game. Likewise, if the 3-prong plug was ever changed in its life, it's a good idea to remove the cover of the plug, and inspect how the wires are connected to the terminal screws of the replacement plug.

After looking over the line cord plug, inspect the line cord. Make certain that there are no nicks or cuts in the cord, deeming it unsafe. [http://www.pbresource.com/tools.html#Parts Pinball Resource] carries an inexpensive, flat, 3-conductor, 14ft. line cord. Next, move to the inside of the cabinet. Make certain that the line cord is securely soldered to the terminals on the line filter. Equally, make certain the ground of the line cord is fastened to the earth ground of the cabinet.

===Check All of the Fuses===
It is highly recommended to check all of the fuses in the game. This includes the fuses on the rectifier board. However, on some games, there are fuses also located under the playfield (for solenoids), on the cabinet wall (for chime coils), behind the display panel (for displays on early Stern games), and / or on the solenoid driver board (for the displays). As mentioned, not all games have fuses in these locations, but be on the look out for them. The best way to make certain that all of the correct fuses go in the correct places is to first remove all of the fuses. Once they are removed, use an ohmmeter or DMM, and check continuity across all of the fuses. Once the fuse have been checked, start placing them back into their proper locations. By removing all of the fuses, the user is forced to put the correct values in the correct locations. Fuses can be kept in the game, but if checking continuity, one side of the fuse must be removed from the fuse holder to attain an accurate reading.

===Inspect the Circuit Boards===
*Burnt / scorched portions of board
*Battery rot on MPU
*Battery rot on lamp driver board and other boards
*Bulging caps on SDB

===Inspect / Test the Circuit Board Components===
*Quick test on the solenoid transistors

===Inspect the Circuit Board Connections===

*Wires soldered directly to rec. board.
*Connectors destroyed due to battery rot

===Check the Solenoids===
*Physically move plungers in coils
*Check solenoid resistance
*Don't forget hidden coils, such as knocker, chimes, and coin lockout
*Check EOS switches on flippers

===Inspect Harness Wiring===
*Make sure screw is secured for ground braid between head and cabinet
*Make sure cabinet ground braid is connected to ground (gets ripped / torn)
*Look for cuts on coin door wiring
*Look for unsoldered / cut wires "floating around"
*Look for burns / scorching

===Plug It In and Turn It On===
*Plug in minimal amount of boards
*Start w/ input to rec. board
*Plug in 20 pin head harness to rec. board next
*Plug in upper right of SDB next
*Plug in lower left of MPU next
*Plug in upper left of LDB next
*Plug in all others on LDB next
*Plug in upper left of MPU next
*Plug in lower right and all others on SDB
*Listen for locked on coils
*Plug in upper right and lower right of MPU

 

==Problems and Solutions==
===Connectors===
Vibration, heat, poor storing conditions, and in some cases alkali damage all take their toll on the connectors used in a pinball machine. Both the male header pins and crimp connectors within plastic housings, (in rare instances, IDC connectors too), are susceptible to the aforementioned conditions. Likewise, some previous person may have performed work on the game which got the job done, but was not necessarily the proper or most desirable way to do it. 

Since the backbone to a properly and reliably functioning game is the connectors, spend some time inspecting all of the connectors in the game, before turning it on for the first time. If any connectors appear to be suspect, repair or replace the connector involved. The best practice is to replace both the male headers and the crimp connectors, if a specific area has seen some sort of damage from heat, oxidation, or alkali damage. In most every case, the plastic or nylon connector housings can be reused, if the crimp connectors are carefully removed.
 

====The Importance of Keying Plugs====
[[File:Stern J3 Rec Two 10s.JPG|200px|left|thumb|Connector as found on a Stern Rectifier Board J3 Connector]]
[[File:Stern J1 Rec Board Keyless.JPG|200px|left|thumb|Connector as found on a Stern Rectifier Board J1 Connector]]
[[File:Stern J3 Rec Replaced.JPG|200px|right|thumb|Connector repinned, keying plug installed, and proper housing for Stern Rectifier Board J3 Connector]]
In addition to connectors, keying plugs play a large role in a game. Every .100" and .156" header connection has one pin removed. The purpose of this practice is to differentiate between connectors with minimal effort. The compliment housing will have a keying plug installed in the position where the header pin is absent. This was done originally at the factory. However, if a connector was replaced or repinned, a person who previously worked on the machine may not have installed a new keying plug. 

Two examples of connectors without keying plugs can be seen in the pics on the left. This game had its wiring harness removed, so the connectors were not placed in their proper positions, and had to be reinstalled. The problem with the first pic is these two .156" 10-pin housings were being used in lieu of the proper, single .156" 20-pin housing at the J3 connection of the rectifier board. The potential to incorrectly plug these two connectors onto the J3 header is extremely high. Because neither housing had a key installed, plus two housings were used instead of one, there are at least four different ways that this connector could be connected. Incorrectly plugging the connector onto the header may have caused extreme unnecessary damage to several of the circuit boards. 

In the lower pic to the left, the connector which goes onto J1 of the rectifier boards was missing a key too. In addition to possibly being plugged in upside down, this connector just as easily could have been plugged in one pin off. If the connector was installed incorrectly, the results would not have been good. 

Considering the overall cost of a keying plug (around $0.25) it is well worth the small cost and effort it takes to install one. It can potentially save the user from unnecessary and costly repairs to the game. If you simply do not have a keying plug and can't remove the old one from the connector, you can use a square toothpick or a Qtip shaft cut down slightly to make one. It is a hack but it's better than destroying good boards and components.
 

====So, Just What is this Green Slime?====
[[File:YouveBeenGreased.jpg|200px|left|thumb|Typical Blue-Green Slime, sometimes found on Bally/Stern header pins.]] 
Sometimes, a blue-green slime seems to be "bleeding" from a header pin connector. This is most likely the insulation coating breaking down into a slime. The best course of action, for long term reliability, is to repin both the male and female sides of the connector, getting rid of the slime as you go.
 

===Powering up the first time===
Thanks to Bally's decision to modularize their system, there is a technique you can use to save yourself some headaches when you first power up a machine. This method connects one section/board at a time and allows you to test each board thoroughly before moving onto the next so you can isolate any issues to one board. This method concentrates on the -18, -49, and all stern games rectifier boards. The -54 rectifier board on later Bally games would employ a slightly different technique.

Disconnect all connectors from the mpu, lamp, sound (if present) and solenoid driver boards. Disconnect J1 and J3 from the rectifier board. Leave J2 connected. Check all the fuses for proper values on the rectifier board. Power on the game, watching to see if any fuses blow. Use a meter and test each test point on the rectifier board to ensure proper voltage is present (remember some of the voltages are AC). Get the rectifier board working 100%.

Turn the game off and reconnect J3 to the solenoid driver board. Connect J3 to the rectifier board as well. Power on the game and repeat the voltage tests on all the test points on the rectifier and solenoid driver board. Investigate any suspect voltages and correct any faults found. Keep in mind that the displays use both the high voltage and +5 voltage so it might be a good idea to remove the displays from the circuit, also.

RottenDog Solenoid Driver/Voltage Regulator

[[File:RottenDogTL783.jpg|300px|left|thumb|A RottenDog high voltage regulator, a TL783.]] 
The RottenDog solenoid driver board uses a TL783 voltage regulator to create display High voltage which should be about 185VDC. This voltage regulator isn’t designed to work as it has been implemented on this board. If the TL783 fails, and they do quite often with this implementation, the full 240VDC will be sent to your displays. This will cause the displays to develop “zits” and fail prematurely. 

Once the solenoid driver board tests ok, connect J4 to the mpu board. Do not reconnect any other connectors to any other boards at this point. Power on the game; if all is well, you will see the mpu board start its LED flash sequence. This is where the majority of repairs will take place; there's no point in hooking other boards up until you have a solid rectifier, solenoid driver/power regulator, mpu board combination working.

After/if the mpu board is booting, add the rest of the connectors back in. When you add the playfield's connectors back in and power up, listen for any solenoids locking on at power-up. Repair the solenoid circuits before proceeding if any do lock on.

At each step in the chain, be sure to inspect and repair any and all connectors in the circuits. Often the connectors get tarnished and do not conduct well enough for reliable game operation. Do not try to clean or sand any suspect connectors - this is a temporary fix at best and only delays the inevitable task of replacement.

Using this method for powering up the game for the first time ensures that any issues you encounter will be isolated to the last piece you added in. Diagnosing and repairing one board at a time is much simpler than multiples.

===Rectifier Board Issues===

====-18, Stern Rectifier boards====
The rectifier board takes the AC voltage from the transformer and uses bridge rectification to convert those voltages to DC. No filtering is done on the rectifier board (that's the solenoid driver/power supply board's job). Depending on the generation of board, there are varying amounts of discrete diodes or bridge rectifiers that produce the DC voltages needed. Additionally, all of the circuits have a fuse for protection in the event of a short on this board.

Putting a meter on the test points across the top of the board will tell you if you're missing any voltages. Refer to the schematics or the charts above to determine the proper voltages at each test point, and remember that some of the voltage outputs are AC volts. If there are any missing voltages investigate further to determine the cause. The main issues with the rectifier board are cracked header pins, bad bridges, poor fuse clips, and poor connections on through hole vias.

If you do nothing else to your power supply, replace the header pins and the connectors that connect to them. The pins are usually burnt beyond usage as are the connector pins. (Often, operators chopped the harness connectors off and soldered the wires directly to the pins as a "fix".) You can get 10 amp header pins from various suppliers that are more robust than the original 7 amp versions. Often just this change alone will fix many lamp "wavering" problems you see on games with lots of feature lamps.

When you replace the header pins consider prying up the plastic insulator piece slightly that keeps the pins in place so you can solder to the top and bottom of each pin. This technique will cure any problems with vias you have and obviate the need for jumper wires that accomplish the same thing. After soldering you can push the insulator piece back down.

Many times the fuse clips are weak or aren't making good contact with the fuses. If you inspect the fuse clips and they are tarnished at all, replace them. Any fuse rated at 4 amps or more use a high current fuse clip to eliminate issues in the future with that circuit. Lower value fuses can use lower current clips with no problem. Solder the fuse clips bottom and top where appropriate for maximal mechanical strength and conductivity.

It's a good idea to replace the discrete diode bridge for the high voltage score display with 1N4007 diodes mounted slightly off the board (about 1/4") so that air can circulate all around them. Solder the leads top and bottom where appropriate. The power resistors should be replaced also with a slight air gap below them to help with cooling. It is possible to approximately double the size of the power resistors (25 ohm to 47 ohm, 600 ohm to 1.3k ohm) to help with the heat dissipated [http://groups.google.com/group/rec.games.pinball/browse_frm/thread/4f40e7f54348acd6/b428979e9f2597c3?lnk=gst&q=bally+rectifier+resistor+gpe#b428979e9f2597c3 Resistor/temperature discussion] although the final test results were not posted.

If you need to replace any bridges, the original style VJ248 bridge can be replaced on the -18 board with a wire lead 25 or 35 amp bridge rectifier. The notch in the bridge is the positive + output; diagonally opposite this lead is the DC negative -. The other 2 leads are the AC inputs and are interchangeable. You have to bend the leads slightly to get them to fit in the smaller VJ248 solder pads. Mark the top of the board with the positive, negative, and AC leads so you don't solder the bridge off by mistake.

If you decide to use the original style bridge, make sure it's not thicker than the other bridges in any other position. The 3 bridges must lie flat against the heat sink slug for proper cooling. The best way to install a replacement VJ248 of the same thickness is to put the bridge in place, then bolt the slug back onto all 3 bridges. Solder the replacement bridge in place. Reinstall the slug with heat sink compound (available at computer supply stores or Radio Shack) smeared in a single thin layer on each bridge surface, and the slug surfaces. Use the least amount possible to get a good even layer; more is not better.

After replacing any parts, test your work with only the J2 cabinet connector installed. Never over fuse a circuit unless the manual for the game specifies; for instance, games with more than 2 flippers often recommend a larger fuse for the solenoid circuit to handle the additional load multiple flipper coils place on the fuse.

====Bally -54 Rectifier board====
[[File:Bally Rectifier board -54 component side,jpg.jpg|300px|left|thumb|Bally -54 Rectifier Board (Component Side)]]
[[File:Bally Rectifier board -54 solder side.jpg|300px|right|thumb|Bally -54 Rectifier Board (Solder Side)]] 

The weak link of this generation of rectifier board are the CR1-CR4 diodes (originally 1n4004, replace with 1n4007 - not so much for the added power capacity, but for the increased heat dissipation) and CR5-CR8 (6 amp at least 50v diodes). The original bridges are much hardier on this generation of rectifier board. If you do need to replace a bridge, the best way is to install it and bolt it onto the bottom mounting plate, then solder it into place. The bottom mounting plate acts as a heat sink for the bridges. 

BR1 is for the feature lamps on the game, BR2 is for the solenoids. The bridge formed by CR5-CR8 forms the +5 vdc, and the one formed by CR1-CR4 supplies the high voltage for the displays. Mount the discrete diodes slightly off the board for better cooling. While not a large problem on this board, inspect the fuse clips as well to ensure they are not tarnished.
 

===The Single Largest Culprit in MPU death===
[[File:Batery_damaged_bally_-17.jpg|300px|left|thumb|Typical Alkaline Damage to a Bally MPU board]] 
By far the largest reason the MPU board stops working is because of alkaline corrosion from the on-board rechargeable batteries. The original battery used on the board is a 3.6 volt nickel cadmium rechargeable battery; over time, this type of battery leaks corrosion into the traces surrounding it, affecting the 5101 memory, the reset circuit, the 6810 memory, the LED area, and all the traces around it. One of the worst boards had corrosion stretching throughout the entire ground plane of the board.
 

====Get rid of that battery now!====
[[File:nicad_elim_options.jpg|left|300px|thumb|Some Options to Eliminate the Ni-Cad Battery on the board]] 
If a battery is on the board, it is recommended to remove it immediately. There are several different ways to replace the battery; in order of preference: 5101 ram eliminator, memory capacitor, nothing, lithium battery, remote mounted AA battery pack, exact replacement. The different options with pros and cons are listed below.
 

5101 Ram Eliminator
:A 5101 ram eliminator doesn't eliminate the ram per se; it replaces it with a more modern ram that is either flash ram or has an internal battery built into it.
:Advantages: eliminating a static sensitive obsolete part, eliminating any type of battery that could leak, high reliability, very long retention time (10-99 years)
:Disadvantages: relatively high cost, need to remove the 5101 (if not socketed) and replace or add a socket, stressing relatively frail mpu board traces, flash ram type can wear out (although unlikely)

Memory Capacitor
:A small capacitor (5.5 volt 1.5 farad works well) is added to the board in place of the original battery. The charging circuit for the rechargeable battery works just fine in maintaining enough of a voltage to enable the capacitor to act in place of the battery. Experience with memory capacitors is somewhat unpredictable. In some games, a charge lasts only a couple months; in other games, it has been seen to last at least a couple years.
:Advantages: relatively low cost, easy installation, no risk of battery leakage, high reliability
:Disadvantages: large initial charge time, some 5101s draw too much current, must turn machine on every couple of months to top off capacitor

Nothing
:Removing the battery and cleaning the board up, you do have the option to replace the battery with nothing. If you don't care about audits, settings, or high scores, this is a valid option. Some software might not like having random garbage in its memory range, though. If you have a Stern MPU-200 based game, do not leave the battery out as the random garbage will cause problems with Stern's software. However, there have been free play romsets developed for this era game that zero out the memory on every bootup, ensuring no garbage gets into the audits causing game errors. Note that not all free play roms have this option, since there is no battery, there's no way for the game to save high scores, options, etc.
:Advantages: No risk of leakage, ever
:Disadvantages: No high scores save, no audits, garbage in ram can cause issues with some software, unless a specific romset is installed with this usage in mind.

Lithium Battery
:Replacing the original nickel cadmium battery with a lithium battery is possible; however it is imperative that you add a blocking diode to prevent the battery from being charged.
:Advantages: Very long life (10 years on average), cheap, can be mounted far from boards so any leakage would not leak onto boards
:Disadvantages: Must use blocking diode, can leak (unlikely), any leakage difficult to clean up

Remote Mounted AA Battery Pack
:A popular and inexpensive option is to replace the original battery with a small AA pack, with a blocking diode. Like the lithium replacement option, it is essential to have a blocking diode (usually incorporated into the pack) so the mpu doesn't try and charge the AA batteries. If you get lithium AA batteries you can get very long life. This type of battery pack needs to be checked periodically to ensure no leakage is occurring.
:Advantages: Low cost, can be moved far from boards so if batteries so leak they do not leak directly onto boards
:Disadvantages: Periodic maintenance (replacing/checking), can leak

Exact Replacement
:You can replace the NiCad with a NiCad. Not recommended as all of the original pitfalls of the original battery are still present, but it will work. Many people use cordless phone batteries to do this; just make sure the voltage and amp hour rating are similar to the original battery. (3.6 volt 150 milliamp hours)
:Advantages: Low cost, can also be mounted far from boards so any leakage does not leak directly onto boards
:Disadvantages: Can leak, needs periodic maintenance (checking for corrosion)

Note that all of the replacement options that include batteries are subject to the same conditions causing leakage as the original battery was. It is strongly recommended that if you decide to use a solution that uses a battery as its power source to remotely mount the battery so that any future leakage does not drip onto the boards. The bottom of the head is a good choice as is the sidewall in cases where there are no boards mounted there. Corrosion can and does travel through the wiring used to relocate the batteries however, so periodic inspection of the batteries and board are necessary to ensure that no further corrosion is occurring.

====Installation of Various Battery Eliminators====
=====AA Battery pack=====
[[file:Battery-Holder-and-Diode.jpg|thumb|left|300px|4 AA cell battery holder & diode]] 
One inexpensive option is to replace the Ni-Cad rechargeable battery pack with a 4 AA battery pack plus diode using ordinary alkaline batteries. You must install a blocking diode (1N5817 or 1N4004 work fine) to prevent the game from trying to charge the battery and causing damage. Install the diode in the 1st bay with the banded side soldered to the "+" or RED terminal and the non-banded end to the "-" BLACK negative spring. Having a battery backup will save high scores & credits, and some sound settings. The holder can be mounted in a convenient spot in the backbox, and leads soldered to the MPU and a Molex .062 2 terminal pin and socket connected to the battery holder for easy servicing of the MPU. Mouser P/N 12BH348-GR for the 4 AA pack.
 

=====Lithium Battery with Holder=====
[[File:Stern M-200 Lith Bat.JPG|thumb|left|300px|Lithium Battery with Holder Installed on Stern M-200 Board]] 
Adding a 3v lithium button battery is an option. It is recommended to install a lithium battery holder. Adding a holder is beneficial for two reasons. First, heating a lithium battery is dangerous. There is potential for explosion, if the battery is overheated. Secondly, adding a holder makes future replacement of the battery much easier. 

If adding a lithium battery, a blocking diode must be installed to keep the MPU from charging the battery. Although it cannot be seen in the pic to the left, a blocking diode is installed on the component side under the battery holder. The M-200 has 4 through holes located just above the bottom ground trace. These through holes are used to install an alternate block style Ni-Cad battery. The bottom left through hole is for the battery's positive terminal. The upper left through hole is used only to support the battery (the pad does not go to any of the board's circuitry). 

In this example, the banded side of the diode is soldered to the lower left through hole. The non-banded side is soldered to the upper left through hole. Additionally, the positive lead of the lithium battery holder is placed in the same upper left through hole. The negative terminal of the battery holder is soldered into the center larger through hole located along the large ground trace (bottom perimeter of board). 

Once the battery holder is installed, install the battery. A CR2032 lithium battery was used in this case. Once the battery is installed, use a voltmeter to make certain that the battery voltage is getting to the 5101 RAM chips. Place the black lead of the voltmeter on any of the ground traces, and the red lead on pin 22 of U8 and U13. A reading of ~3vdc should be seen.
 

=====Memory Capacitor=====
[[File:Cap_install.jpg|300px|thumb|left|Prepping an MPU Board for Memory Cap Installation]]
[[File:Bally -17 Mem Cap.JPG|300px|thumb|right|Alternate method for installing a memory cap. Negative lead is tack soldered to perimeter ground plane. -17 board shown in pic.]] 
Remove original battery, neutralize and clean any corrosion left behind/inspect parts in area, replace as needed. Drill a small hole to the left of the original batteries' negative terminal. Install the capacitor with the negative lead in the leftmost hole of the negative terminal, soldering it into place. Solder a lead to the positive terminal of the capacitor and bend the leg over to help hold it in place. Solder the other end of the lead to either the positive hole from the original battery, or to the bottom lead of R12. Double check your work in reference to the negative lead of the capacitor. Turn the machine on an let the capacitor charge for around 1/2 - 1 hour. Once the cap is charged, turning the machine on for about 1/2 hour a month will keep it topped up.
 

=====Original style battery or cordless phone battery=====
:Remove original battery, neutralize and clean any corrosion left behind/inspect parts in area, replace as needed. Solder new battery in, or better yet, attach fly leads to battery and remote mount. Installing leads long enough for the battery to rest inside the cabinet versus the backbox is optimal. Sealing the battery inside a Ziploc bag is another good idea. Turn machine on for large initial charge to battery. Note that NiCad batteries will leak, just like the original batteries that were used on the MPU. Lithium batteries will be less prone to leaking.
 

====Repairing Alkaline Damage ====
Should a leaky battery damage your MPU, the first decision to make is this: is the board worth repairing? The extent of the alkaline damage combined with your PCB repair skills, the value you place on your time, and the quality of the result you want to obtain may drive you to replace the board entirely with either an OEM board or one of several aftermarket replacements. Alkaline cleanup, component sourcing and replacement, and socketing troublesome old IC sockets can take 3 to 8 hours.

Should you decide to repair the board, component kits to replace everything in the "corrosion zone" are available from several sources for about $10.

Note: Most alkaline damage repair kits do not include the L1 and L2 inductors which are often damaged. Since these inductors are so small in value, simply replace them with a jumper.

Once you've decided to proceed, to neutralize alkaline, you need an acid. The most common way to accomplish this is to wash the affected area of the board with a mild vinegar solution (50% vinegar to 50% water). Use a toothbrush to scrub the board's affected area and outside the affected area, front and back. After scrubbing, rinse the board with water, then use isopropyl alcohol (the highest percentage you can get - 99% or 91%) in a wave action down the board to displace the water. Let the board air dry, or use a hair dryer without heat to speed the drying process.

After the board is dry, replace any components that were affected by the corrosion damage. The parts will be harder to remove and solder as the combination of corrosion and cleaning makes the solder difficult to heat. Adding new solder before desoldering will help in this process, as will boosting your temperature controlled soldering station up by about 50 degrees. Be careful as the pads are very fragile at this point and can lift easily.

Alternate methods of cleaning the affected areas include bead blasting, and sanding. If the damage is very slight, sanding might work best but you remove all the conformal coating when you do so (that's the green masking material applied to the traces on the board). You have to either replace this coating, or use an alternate material to protect the bare traces from oxidation. Clear nail polish has been used to do this, but isn't a great substitute. You can also tin the affected traces with new solder which will protect the copper. It is also possible to purchase conformal coating but it is toxic and messy to work with. **** Note when sanding your MPU you should wear a mask. The board has glass fibers that are bad for the lungs.

Bead blasting is a technique that uses small glass beads on a sand-blaster type setup to blast away the corrosion. Again, the conformal coating is removed and should be replaced. Some critics of the bead blasting technique indicate that the corrosion actually gets embedded in the board by this method; however, it is an accepted repair practice in electronics repair. Most people do not have the equipment needed to do this.

Regardless of the method used, any bare copper traces should be at minimum tinned with solder. Often after removing the components, you will need to sand the remaining pad to get a good soldering surface. A small fiberglass sanding pen is ideal for this purpose (available at auto parts stores). It allows precise sanding on small surfaces. Sand right before you solder as copper starts to oxidize immediately. Use a can of compressed air to blow any fiberglass particles out of your work area and be careful using the fiberglass pen as the fibers will become embedded in your skin causing irritation. Wear eye protection as well as you really do not want these particles flying into your eyes!

Use a meter to test your work, following point by point as you replace components to ensure you have a clean circuit path. Add jumpers as needed, and solder replaced components top and bottom to ensure good via continuity. Use a high quality socket when you replace the 5101 ram and be very careful around this area, as it is right next to the battery zone and is usually heavily damaged. All of the traces in this area are part of the address and data bus for all the roms, pias, and cpu, so any shorts or damage here will affect the rest of the board.

Finally, remember also that the alkaline will travel both down and up from the original position of the battery. Inspect the lamp driver board (right below the MPU) to ensure it hasn't become corroded also. If the corrosion was really bad, inspect the J4 connector on the MPU too. Corrosion will travel into the wires in this connector. If this has happened, you must cut the wires back far enough so the corrosion is not seen; otherwise it will leach back into your board and continue to spread through the wiring harness. Hopefully, the harness will still have enough slack to make it to the J4 connector. If not, you can extend the wires neatly by soldering and heat-shrinking new wires onto the harness. Having a parts machine to pull this type of wiring from enables you to match closely the wire markings so prevent confusion in the future.

Another thing about the J4 connector is that on most boards the two ground pins only connect from the top of the board. If battery corrosion made it to that connector it is a good idea to add a jumper on the solder side of the board from J4 Pin 18 and 19 to ground that runs along the outside of the board.

<center>
<gallery widths=300px heights=200px perrow=2 caption="Bally/Stern MPU Alkaline Damage Abatement">
File:BallyMPUAlkalineCleanedUpFront.jpg|<center>The front side of a Stern MPU-200 with alkaline damage removed.</center>
File:BallyMPUAlkalineCleanedUpBack.jpg|<center>The back side of a Stern MPU-200 with alkaline damage removed.</center>
File:BallyMPUAlkalineCleanedUpCorner.jpg|<center>An MPU-200, "corrosion zone" cleaned up.</center>
File:Corrosion_Cleaned_MPU.JPG|<center>A Bally -17 MPU, "corrosion zone" cleaned up.</center>
</gallery>
</center>

===== Alkaline Corrosion Area Parts List=====
[[File:CorrosionArea.jpg|200px|thumb|left|Bally/Stern Corrosion Area Parts List|link=https://www.pinwiki.com/wiki/images/f/f5/-17and-35MPUComponentListForPinWiki.pdf]] 
Clicking on the thumbnail at left will open a .pdf file detailing parts used in the alkaline corrosion zone for Bally and Stern MPUs. The original parts "skeleton layout" was done by Ed at [http://www.greatplainselectronics.com Great Plains Electronics].
 

==== Using the Dallas/Maxim DS1811 Reset Generator on Bally and Stern MPUs ====
Like the [[Gottlieb_System_80#Using_a_Reset_Generator_for_the_CPU_Reset_Section| technique]] employed to repair alkaline damage on Gottlieb System 80 MPUs, the Dallis/Maxim DS1811 reset generator may be used on Bally and Stern MPUs also. The DS1811-10 has a typical trip point of 4.35VDC. You may also use the Microchip Technology equivalent, part number [http://www.greatplainselectronics.com/proddetail.asp?prod=MCP130-460DI%2FTO MCP130-460DI/TO], available from Great Plains Electronics.

Unlike Gottlieb System 80 MPUs, using the DS1811 on Bally and Stern boards doesn't save you much work. It replaces only 10 easily sourced components. And since you've done the hard work of cleaning up the alkaline damage already, using the DS1811 isn't really worth the trouble. But, if you'd like to use the DS1811, the procedure is described below.

After you've cleaned up the alkaline damage, replace all components except these 10:
*VR1
*R1, R2, and R3
*R112
*R138, R139, and R140
*Q1 and Q5

With the board oriented as it would be in the game (J5 at top), install a jumper from the top through-hole of where R139 was, to the bottom through-hole of where R138 was.

There are several ways to form the legs of the DS1811 for a Bally or Stern MPU. However, with the flat side of the DS1811 facing left (i.e. at J4), the legs of the DS1811 should be placed in the prior location of Q5 such that:

*Pin 3 of reset generator (top pin) is where the upper, right lead of where Q5 was
*Pin 2 of reset generator (middle pin) is where the lower, right lead of Q5 was
*Pin 1 of reset generator (bottom pin) is where the left lead of Q5 was

Add a 1K, 1/4W resistor from pin 1 of the reset generator to +5VDC. This signal can be picked up conveniently at the banded end of CR5 (a 1N4148 diode).

<center>
<gallery widths=300px heights=200px perrow=2 caption="Using the Dallas/Maxim 1811 Reset Generator">
File:MPU200DallasReset.jpg|An MPU-200 MPU with alkaline damage abated, and reset components replaced with the DS1811 reset generator.
File:MPU200DallasResetAnnotated.jpg|The same image, but with the single jumper indicated (yellow dot), where to install the DS1811 flat side facing left, and the added 1K resistor.
File:Placeholder.jpg|Illustrated picture of components to remove, keep, and jumpers to add.
File:MPU200DallasResetCloseup.jpg|Closeup of the DS1811 equivalent installed.
</gallery>
</center>
 
One could also use The MCP100-460-DI/TO although there are a some variations from the DS-1811.

The following need to be removed (or not replaced)
*VR1
*R1, R2, and R3
*R112
*R138, and R140
*Q1 and Q5
The difference here is that R139 is left intact.

Jumper R2 & R3.

Add a 1N4148 diode. Anode to anode of CR7, cathode (banded end) to "left" hole of R140. The CR7 anode hole is large enough to accommodate both diode leads without trouble.

The MCP100 is added in the Q1 (not Q2) location.

With the flat side of the part facing and the leads pointing down, the leads are from left to right, RESET, V (+5v), and Ground.

*V (+5v) the middle lead, is soldered in the "top" hole, close to the now occupied hole of R140
*RESET in the left most hole
*Ground in the bottom most hole (which clearly goes to ground)

This solution is slightly less messy because it does not require the "floating" 1K resistor.

===MPU boot issues===
Non-booting Bally/Stern MPU boards fall into a couple different categories. If the board's LED is good and turns off at bootup, you're part of the way there. Refer to the flash sequence section to figure out where your issue lies to narrow down the problem area. 

You must have a good set of roms in a game as well as a known good working 6800 cpu chip. Suspect any sockets that have a brown color or closed frame - often the spring tension on these sockets is poor necessitating replacement. Be very careful soldering on the mpu boards as the traces and pads are very fragile. 

A "cheat sheet" comprised of the signals and pinouts for the primary chips and all of the header connections used with a Bally -35 MPU board is available [[Media:Bally_MPU_Board.pdf | here]]. The PDF is specifically for a -35 board, however, Bally -17 and Stern M100 boards are similar. The obvious differences are the ROM jumper settings and connection J5 (J5 on a -35 board has one more pin).

====LED locked on====
Remove all ICs except for U6, U9, U11, and U2 if it is a Stern. Leon's test rom is recommended for tricky MPUs. This allows you to leave out U11 and check most address and data lines.

Short pins 40 and 39 momentarily on the cpu chip; after doing so, see if the LED goes off. If it does, concentrate your efforts on repairing the reset circuit as it's not holding the reset low on powerup for the minimum required 50 milliseconds. If it doesn't, it's best to pull the board from the machine and put it on the bench, using the benchtop power supply details to keep working on the board outside the machine.

Ensure that Q2 and the LED itself are working properly (i.e. the board may be booting but the LED provides no indication). Pin 39 of the 6821 PIA at U11 drives the LED. Probing pin 39 and finding it pulsing indicates that the MPU is booting (or at least partially booting) and that R28 (8.2K), R29 (470), Q2 (2n3904), or the LED itself has failed.

An easy quick test for the reset section is putting your DMM on pin 40 of the cpu. It should read 5v, and in most cases if it does the reset is good. Attach a logic probe to the output of Q5 - on power on, you should see this circuit start low and then go high approximately 50 milliseconds later. If it goes high immediately, at a minimum replace Q5, then Q1. Make sure the 2 watt resistor is not leaning on Q5. The heat can kill the transistor.

Next put the probe on U9 pin 3, 36, and 37 to see if you get pulsing - these are all clock signals and you should see pulsing on all 3 pins. If you have an oscilloscope you can visually see the signals, or even on a multimeter, the voltage will show between 2.5-2.9 volts. If you see zero volts or 5 volts, your clock signal is bad. The CPU could be dragging down the clock. Remove U9 and see if the clock signal is now good. When clock signal is bad suspect U15 or U16. Also check C15 and C14. U15 is failed most often.

Check U9 Pin 2. This is the HALT line. You should see 5v, if not replace U9

Check U9 Pin 5. This is the VMA line. It is a pulsing signal and reads about 2.8v with a DMM. If incorrect first try a new U9. Next check U14D, U15C, U19B. U15 is the most likely IC to have failed.

Still locked on? After double checking all your jumper changes, roms, and rams in another board if possible, time to start suspecting other issues such as bad sockets, traces, or addressing chips. Bad sockets are quite common.

====Reset Circuit====
The purpose of the reset circuit is to ensure the +5 vdc is stable before allowing the system to start. At startup, the reset signal is held low via pull-down resistor R139 until the +12 vdc line rises above the zener diode VR1's value (8.2 or 9.1 volts depending on your board). At this time, the input voltage threshold for the +5 regulator on the solenoid driver board has been met with some headroom. Q1 starts conducting, turning on Q5, which provides the actual reset signal. All of this happens in approximately 50 milliseconds. 

Most of the reset circuit is in the corrosion zone (lower left corner of the mpu board) and consists of most of the components commonly included in "repair kits". If the reset circuit is not working, the LED will not turn off. If Q1 or Q5 fails, conducting all the time, the cpu chip will never come out of reset. 

The reset circuit continuously monitors the +12 volt line; if it falls below VR1's threshold voltage, the game will reset. If a Bally/Stern game is resetting, concentrate on why the +12 volts is dropping below 8.2/9.1 volts. (VR1 sets the threshold at which the reset signal turns on, and also when it would turn off in a rebooting scenario.) 

Note that Q1 and Q5 actually form a switching power regulator for the reset signal only. The normal +5 supplied to the rest of the board is derived entirely from the solenoid driver board's regulator. The reset signal regulated power is used to charge the battery, provide the reset signal, and to power the 5101 chip(s) on the board. Normal +5 vdc is blocked from entering the reset circuit by the 1N4148 diode CR7. Diode CR5 (1N4148) blocks the battery voltage from powering the entire board via CR7. 

====Bally / Stern MPU Board LED Never Lights or is Locked On====
If the LED never lights, either the +12v (TP2, J4 pin 12) is missing or the LED is bad. By default, the LED is ON until the software tells U11 to turn it OFF. 

If the LED lights solid, there's some digging to do. First off, if the board has any corrosion damage at all, it needs to be cleaned and neutralized before attempting any repairs. While shot-gunning components might fix the board, it won't be 100% reliable if the corrosion isn't addressed. 

Make sure you are getting a solid power path from the rectifier board through the solenoid driver / power regulator board to the MPU board. A locked on LED can be caused by a poor connection anywhere in this chain. Sometimes reseating connector J4 on the MPU board (lower left) will 'clean' a connector well enough to make a better connection. While this may be a short term fix, be aware that any connector, which seems to work better after being reseated, really should be repinned and have its header pins replaced. 

Next, put your DMM or a logic probe on pin 40 of the 6800 cpu chip (U9). Power on the board. You should see the voltage remain low / at zero, and then approx 1/10 of a second later, rise to about +5 vdc (high). This is the reset signal, which originates from the components in the lower left corner of the board, and is sent throughout the board to U9, U10, and U11. What the reset section (called the 'valid power detector') does is not allow the MPU to boot until the +12 volts are stable over the value of ZR1 (a zener diode, usually either 8.2 or 9.1 volts). This delay ensures that the +5 voltage is stable enough to run the MPU board reliably (the +5 volts is derived from the +12 volts on the solenoid driver / power regulator board). 

The 6800 CPU chip will not 'unlock' and start program execution until it sees a transition from a low (0 volts) to high (~5 volts) signal. This is the purpose of the power on reset delay. The reset delay and signal must be present at all three of the reset inputs at U9 (pin 40), U10 (pin 34), and U11 (pin 34). If the signal starts out immediately at a high level, the MPU will not start to boot until the transition takes place. If you have a locked on MPU, you can take a screwdriver or your meter probe and short pins 39 and 40 together for a brief moment on U9. If the game starts to boot after doing this, it's a safe assumption that the reset circuit is to blame. Shorting the pins together simulates what the reset circuit does. 

If you need to rebuild the reset circuit, full kits are available from specialty suppliers such as Great Plains Electronics or Big Daddy Enterprises. The kits include all replacement components in the corrosion zone. Bare bones component replacements are Q1 (2n3904 or 2n4401) and Q5 (2n4403 or 2n3906), but it is a good idea to go ahead and replace all the parts that come in the kit. Replace components one at a time to ensure that you do not mix any up. Note there are some components that are polarized in their installation, which include VR1, CR5, Q1, and Q5. Look carefully at the board to see if there are traces on the top and bottom of a component. The continuity at a through hole can be compromised due to alkaline corrosion. Therefore, it is recommended to solder these components from the top and bottom of the board to ensure that a good connection is maintained. 

The following is the list of parts for the reset section that should be replaced. Parts listed with more than one type are equivalent and can be substituted freely. It is also possible that the inductors L1 and L2 need to be replaced as well, however this is very rare. If there is heavy corrosion on them they should be replaced. 

'''Transistors:'''

Q1 - 2N3904/2N4401 (lower left area)

Q2 - 2N3904/2N4401 (near LED)

Q5 - 2N3906/2N4403 (lower left area) 

'''Diodes:'''

VR1 - zener 1N9598/1N4738A

CR44 - 1N4004 rectifier diode

CR5, CR7 - 1N4148 switching diode

CR8 - LED 

'''Capacitors:'''

C1, C2 - 820pF ceramic capacitor

C3 - 0.01uF ceramic capacitor

C5 - 4.7uF tantalum capacitor

C13, C80 - 0.01uF ceramic capacitor 

'''Resistors:''' (1/4 w unless noted)

R1, R3, R24, R28 - 8.2k

R2 - 120k

R11 - 82 ohm/2 watt

R12 - 270 ohm

R16 - 2k

R16 - 2.2k (stern mpu-200 only)

R17 - 150k

R29 - 470 ohm

R107 - 3.3k

R112 - 1k

R134 - 4.7k

R140 - 20k 

If your reset circuit is operating as designed, yet the LED is still locked on, next step is to pull all the chips from the board except for U9, U11, and U6 (leave all chips U1-U6 installed on Stern MPU boards. Only U6 is required on Bally boards to perform the initial LED turn off). It helps to have a known working U6 from a Bally game to use as a test chip for this purpose. Be aware that you need to know/have the board jumpered for the correct type of chip you're inserting. 

See if the board starts and turns off the LED with just the chips above installed - if it does, add these chips back in this order to see which might be bad: U10 PIA, U1-U5 program chips, U7 6810 ram, U8 5101 ram. Often a bad ram/rom can cause the entire system to lock up. Bad chip sockets can be a factor as well; the early Bally -17 boards have a closed type brown socket that's especially prone to failure. 

Double check the jumpers to ensure they match the ROM chips you have available, and change the ROM chips to known working ones for testing. A final thing to check if the machine won't boot is the clock circuit. It is fairly robust, and far more common that the reset circuit itself or chip sockets are the issue. To check the clock circuit you need a logic probe or oscilloscope. A multimeter might show the average voltage on a clock circuit, or it might just show meaningless constantly changing numbers. The clock signal is pin 3 on the CPU chip, and the shifted clock signal goes to pins 36 and 37. The frequency is about 500 kilohertz for Bally -17, -35 and Stern MPU-100 boards, and approximately 850 kilohertz for the Stern MPU-200 board. 

If the clock signal is missing, pull U9 first to make sure the CPU chip isn't damaged, and test it again. 

It can be frustrating to track down a locked on LED problem, but breaking the problem up and testing each section individually helps. Just remember that if the LED turns on and then off, most of the battle is won. The board has booted far enough that the software was able to start and turn off the LED. Proceed onto the LED flash testing to determine what needs to be fixed beyond that. 

====Bally / Stern MPU Board LED Flash Sequence====

Upon start up, Bally and Stern boards have an LED that flashes. The LED is used to convey the results of specific tests conducted on various parts of the system. This section explains what is being tested and how, according to information from the Bally "FO-561-2 Theory of Operation rev. 5-1982" manual, and the Stern manual "Theory of Operation, Stern's Microprocessor Controlled Solid-State Games".

When power is first applied to the MPU board, the LED by default is ON. The very first set of valid instructions in every Bally / Stern game is to turn the LED off. This is more of a flicker than a flash, so is not counted as a flash in the 7 flash sequence.

=====Quick summary=====

Flicker: MPU reset good, program booted. 
1st Flash: ROM Checksums OK 
2nd Flash: U7 6810 ram OK 
3rd Flash: U8 5101 ram OK (U8 & U13 on mpu-200) 
4th Flash: U10 PIA OK (see details for caveats) 
5th Flash: U11 PIA OK (see details for caveats) 
6th Flash: U12 555 Display interrupt timer OK 
7th Flash: Zero crossing interrupt detector OK (solenoid voltage present) 

=====LED flicker=====
The LED flicker tells you the CPU chip was able to start a valid program stored in the EPROMs, and that the reset circuit itself is good. 

=====First flash=====
After the program is running, it performs a checksum of all programmed chips U1-U6. Most Bally games' programming is split between an operating system chip U6 and game ROM chip(s) at U1/U2. Stern games were programmed a little looser: operating system and game code are freely interspersed. 

Bally checksums are calculated by summing each byte, and discarding any carries. Most games check their code in $0400 blocks, so it would be possible to determine down to the chip which chip failed this checksum. (A 2716/9316 chip has hex $0800 space available in it - 2732 sized images are $1000 in size. The smallest chip used was a 474 PROM which has $0200 bytes available) However, to do so would require a way to read the X register from the 6800 CPU chip at the time of checksum failure. So if you do not get the first flash, it is best to replace the U6 chip first, then move onto the other chips - U5, U2, and U1 (if present). 

Stern checksums are calculated similarly, but not in chunks. The entire program space is summed and must equal $00 for the first flash to occur. 

Regardless of whether the manufacturer is Bally or Stern, after the checksum is passed, the first flash occurs. 

=====Second flash=====
Next, the program tests the 6810 RAM chip at U7, by writing the data $00 to each memory location contained in the RAM ($00-$7F). It then reads back each location to ensure that $00 is returned. It increments the data to $01 and repeats this test. This continues until the data read back is $FF (256), which is the maximum value of any one byte stored in the RAM. It then increments the memory location being tested, and repeats the $00-$FF data storage test. If any of the tested locations return an unexpected result, the program stops, and alerts you to a problem with U7 (since you got the first ROM checksum flash, but not the 2nd U7 OK flash). 

=====Third flash=====
Now, the program tests the non-volatile 5101 RAM chip at U8 (U8 AND U13 on Stern MPU-200 boards). The 5101(s) store(s) bookkeeping data, game parameters, high scores, replay levels, etc. The program tests this RAM ($200-$2FF) by reading the original nibble / byte (see sidebar), and saves it in a temporary location. Then, it stores a test pattern in the location similar to the U7 test. After the byte successfully passes the test, the original data is returned to the location, and the program loops onto the next byte. 

LEARN MORE: How does a 128 byte 5101 RAM occupy 256 memory locations? 

If you look at a pinout of the 5101 memory, you will notice it is a 128 byte device. Yet, it is addressed by the MPU via 256 memory locations ($200-$2FF). This is because the 5101 is actually a 256 nibble device - a nibble is a half-byte (4 bits). So data stored to a 5101 in a pinball machine actually only stores half of the data byte being sent to it. Which half it stores is dependent on the board design. Bally and Stern use the upper nibble for storage, and Williams used the lower nibble. Stern MPU-200 boards have an additional 5101 at U13. This stores the lower nibble in conjunction with U8 storing the upper nibble of a byte saved to $200-$2FF. This allows MPU-200 games to store more data, and avoid doing some fancy processing by getting the data in and out of the non-volatile ram area. 

For example, here's some pseudo-machine code for what happens:
*LOAD #$24 (the data you want to store is 24)
*STORE $231 (you want to store the data 24 at memory location $231)
*READ $231 (you want to read back the data you just stored)
The data returned is not #$24 as expected, but rather #$2F. The lower nibble was never stored, because the 5101 memory does not store data as bytes but rather as nibbles. To store #$24 properly would require splitting the byte into its nibbles '2' and '4'. The 2 would be stored in one memory location, while the 4 would be shifted, and stored in another memory location. 

Showing the byte as binary might be helpful to visualize what's involved. The hex #$24 in binary is %00100100. Split into nibbles is %0010 (the 2) and %0100 (the 4). The upper nibble is the one the 5101 is able to store directly, but the position in the byte of the lower nibble prevents it from being stored. A shift operation is performed 4 times on the byte to reposition the lower nibble as the upper nibble, which enables it to be stored to the 5101. Each shift moves the binary pattern to the left one bit - here's the full sequence:
*Start=%00100100
*Shift left=%0100100x
*Shift left=%100100xx
*Shift left=%00100xxx
*Shift left=%0100xxxx

This gives the #$4 in the high nibble. All byte data has to be split this way to be saved, and recombined upon reading from boards (Bally -17 and -35, Stern MPU-100) with a single 5101 RAM chip. You can see why Stern added the second 5101 RAM to their boards. It makes programming much easier! 

=====Continuity Chart for U8 5101 RAM in a Bally AS2518-17, -35 or Stern MPU-100 Board=====

{| class="wikitable"
|-
! IC & Pin#
! Data Address
! Continuity Points

|-
| U8 pin 1
| (A3)
| U7 pin 20, U6 pin 5, U9 pin 12
|-
| U8 pin 2
| (A2)
| U7 pin 21, U6 pin 6, U9 pin 11
|-
| U8 pin 3
| (A1)
| U7 pin 22, U6 pin 7, U9 pin 10, U11 pin 35
|-
| U8 pin 4
| (A0)
| U7 pin 23, U6 pin 8, U9 pin 9, U11 pin 36
|-
| U8 pin 5
| (A5)
| U7 pin 18, U6 pin 3, U9 pin 14
|-
| U8 pin 6
| (A6)
| U7 pin 17, U6 pin 2, U9 pin 15
|-
| U8 pin 7
| (A7)
| U7 pin 15, U6 pin 1, U9 pin 16, U11 pin 24
|-
| U8 pin 8
|
| GROUND
|-
| U8 pins 9&10
| (D10&D00)
| U7 pin 6, U6 pin 14, U9 pin 29, U11 pin 29 (* pins 9 & 10 siamesed together)
|-
| U8 pins 11&12
| (D11&D01)
| U7 pin 7, U6 pin 15, U9 pin 28, U11 pin 28 (* pins 11 & 12 siamesed together)
|-
| U8 pins 13&14
| (D12& D02)
| U7 pin 8, U6 pin 16, U9 pin 27, U11 pin 27 (*pins 13 &14 siamesed together)
|-
| U8 pins 15&16
| (D13&D03)
| U7 pin 9, U6 pin 17, U9 pin 26, U11 pin 26 (* pins 15&16 siamesed together)
|-
| U8 pin 17
| (CE2)
| Q5 Right Upper leg, U9 pin 40, U11 pin 34
|-
| U8 pin 18
| (OD)
| U18 pin 6
|-
| U8 pin 19
| (CE1)
| U17 pin 8
|-
| U8 pin 20
| (R/W)
| U7 pin 16, U9 pin 34, U11 pin 21, U18 pin 7
|-
| U8 pin 21
| (A4)
| U7 pin 19, U6 pin 4, U11 pin 22
|-
| U8 pin 22
| (Vcc)
| C13 Left Leg, R12 upper Leg, CR5 Lower Leg
|}
 

=====U8 & U13 5101 RAM Continuity Chart for Stern MPU-200 Only =====

{| class="wikitable sortable"
! Data Address
! U8 Pins
! U13 Pins
! Other Continuity Points
|-
|A0 || 4 || 4 || U9-9
|-
|A1 || 3 || 3 || U9-10
|-
|A2 || 2 || 2 || U9-11
|-
|A3 || 1 || 1 || U9-12
|-
|A4 || 21 || 21 || U9-13
|-
|A5 || 5 || 5 || U9-14
|-
|A6 || 6 || 6 || U9-15
|-
|A7 || 7 || 7 || U9-16
|-
|D0 || NC || 9-10 || U9-33
|-
|D1 || NC || 11-12 || U9-32
|-
|D2 || NC || 13-14 || U9-31
|-
|D3 || NC || 15-16 || U9-30
|-
|D4 || 9-10 || NC || U9-29
|-
|D5 || 11-12 || NC || U9-28
|-
|D6 || 13-14 || NC || U9-27
|-
|D7 || 15-16 || NC || U9-26
|-
|GND || 8 || 8 || U9-1
|-
|VCC (+5V) || 22 || 22 || U9-8
|-
|CS1 || 19 || 19 || U17-8
|-
|CS2 || 17 || 17 || U9-40
|-
|OD || 18 || 18 || U14-9
|-
|RW || 20 || 20 || U9-34
|}
 

Note: The U8 5101 RAM Continuity Chart below is under review for correctness. Hibler reviewing it now...
{| class="wikitable sortable"
|-
! IC & Pin#
! Signal
! Continuity Points
|-
|  U8 pin 01
|  (A3)
|  U13 pin 1, U7 pin 20, U6 pin 5, U9 pin 12
|-
|  U8 pin 02
|  (A2)
|  U13 pin 2, U7 pin 21, U6 pin 6, U9 pin 11
|-
|  U8 pin 03
|  (A1)
|  U13 pin 3, U7 pin 22, U6 pin 7, U9 pin 10, U11 pin 35
|-
|  U8 pin 04
|  (A0)
|  U13 pin 4, U7 pin 23, U6 pin 8, U9 pin 9, U11 pin 36
|-
|  U8 pin 05
|  (A5)
|  U13 pin 5, U7 pin 18, U6 pin 3, U9 pin 14
|-
|  U8 pin 06
|  (A6)
|  U13 pin 6, U7 pin 17, U6 pin 2, U9 pin 15
|-
|  U8 pin 07
|  (A7)
|  U13 pin 7, U7 pin 15, U6 pin 1, U9 pin 16, U11 pin 24
|-
|  U8 pin 08
|  GROUND
|  U13 pin 8
|-
|  U8 pin 09
|  (DI0 & DO0; D4)
|  U13 pins 9 & 10, U7 pin 6, U6 pin 14, U9 pin 29, U11 pin 29 (*pins 9 & 10, shorted together)
|-
|  U8 pin 10
|  (DI0 & DO0; D4)
|  U13 pins 9 & 10, U7 pin 6, U6 pin 14, U9 pin 29, U11 pin 29 (*pins 9 & 10, shorted together)
|-
|  U8 pin 11
|  (D11 & DO1; D5)
|  U13 pins 11&12, U7 pin 7, U6 pin 15, U9 pin 28, U11 pin 28 (*pins 11 & 12 shorted together)
|-
|  U8 pin 12
|  (D11 & DO1; D5)  
|  U13 pins 11&12, U7 pin 7, U6 pin 15, U9 pin 28, U11 pin 28 (*pins 11 & 12 shorted together)
|-
|  U8 pin 13
|  (DI2 & DO2; D6)
|  U13 pins 13 & 14, U7 pin 8, U6 pin 16, U9 pin 27, U11 pin 27 (*pins 13 & 14 shorted together)
|-
|  U8 pin 14
|  (DI2 & DO2; D6)
|  U13 pins 13 & 14, U7 pin 8, U6 pin 16, U9 pin 27, U11 pin 27 (*pins 13 & 14 shorted together)  
|-
|  U8 pin 15
|  (DI3 & DO3; D7)
|  U7 pin 9, U6 pin 17, U9 pin 26, U11 pin 26 (*pins 15 & 16 shorted together)
|-
|  U8 pin 16
|  (DI3 & DO3; D7)
|  U7 pin 9, U6 pin 17, U9 pin 26, U11 pin 26 (*pins 15 & 16 shorted together)
|-
|  U8 pin 17
|  (CE2)
|  U13 pin 17, Q5 Right Upper leg, U9 pin 40, U11 pin 34
|-
|  U8 pin 18
|  (OD)
|  U13 pin 18, U14 pin 9
|-
|  U8 pin 19
|  (CE1)
|  U13 pin 19, U17 pin 8,
|-
|  U8 pin 20
|  (R/W)
|  U13 pin 20, U7 pin 16, U9 pin 34, U11 pin 21, U14 pin 10
|-
|  U8 pin 21
|  (A4)
|  U13 pin 21, U7 pin 19, U6 pin 4, U11 pin 22
|-
|  U8 pin 22
|  (Vcc)
|  U13 pin 22, C13 Left Leg, R12 upper Leg, CR5 Lower Leg
|}

 
Note: The U13 5101 RAM Continuity Chart below is under review for correctness. Hibler reviewing it now...
{| class="wikitable sortable"
|-
! IC & Pin#
! Signal
! Continuity Points
|-
|  U13 pin 08
|  GROUND
|  U8 pin 8
|-
|  U13 pin 09
|  (DI0 & DO0; D0)
|
|-
|  U13 pin 10
|  (DI0 & DO0; D0)
|
|-
|  U13 pin 11
|  (DI1 & DO1; D1)
|  U7 pin 3, U6 pin 10, U9 pin 32, U11 pin 32  
|-
|  U13 pin 12
|  (DI1 & DO1; D1)  
|  U7 pin 3, U6 pin 10, U9 pin 32, U11 pin 32
|-
|  U13 pin 13
|  (DI2 & DO2)  
|  U7 pin 4, U6 pin 11, U9 pin 31, U11 pin 31
|-
|  U13 pin 14
|  (DI2 & DO2)
|  U7 pin 4, U6 pin 11, U9 pin 31, U11 pin 31
|-
|  U13 pin 15
|  (DI3 & DO3)
|  U7 pin 5, U6 pin 13, U9 pin 30, U11 pin 30 (*pins 15 & 16 shorted together)
|-
|  U13 pin 16
|  (DI3 & DO3)
|  U7 pin 5, U6 pin 13, U9 pin 30, U11 pin 30 (*pins 15 & 16 shorted together)  
|}
 

=====Issues with 5101 RAM chips=====

The socket at U8 (and U13 for Stern MPU-200) is very close to the corrosion effects of the alkali of a leaking battery. This is often the cause of boards not showing a 3rd flash. There are traces on the component and solder side of the board, and the socket can hide corrosion to these traces. In turn, the corrosion can affect the 5101 chip's contact with the socket pins. Be careful when replacing corroded or SCANBE sockets at U8, U13, U11, etc. Bally/Stern boards run a number of exposed traces on the top-side of the board in between socket pins. It is extremely easy to splash a miniscule amount of solder, accidentally bridging a socket pin to an adjacent in-between signal line. Use of a logic probe (ground lead at TP4 and 5V at TP5) and sampling all of the signals after a socket replacement will make it very easy to verify your work and locate crossed up (typically scratchy/floating) signals! This can save you minutes or hours of troubleshooting. 

Unless the board is unusually clean, a rebuild of a non-working board should include replacing the socket at U8 (and U13, for MPU-200). The chip is an oddball configuration with 22 pins which makes machine pin sockets hard to find. Use 2 strips of machine sockets, so that you can solder both above and below the board. Inspect the traces closely on the top; it is best to avoid soldering on the top of a board unless you have to as it makes it extremely difficult to desolder the sockets in the future. Take extreme care not to make a solder bridge of the traces on the component side, as it is easy to do. Performing a continuity test to adjacent socket legs after soldering is a good practice. Also, note that some of the pins are shorted together. (see above) 

Failure to achieve the third flash can also be attributed to the following: If the U8 and U13 (MPU-200) show correct continuity as charted above, and the 5101 RAM is known to be good, the problem could lie with the U19 (4011) chip. On Stern MPU-200, replace U14 (4572) instead. Finally, although rare, the 6800 CPU at U9 could be bad. 

The speed of the 5101 RAM chip can make a difference in the functioning of an otherwise good MPU board. If a slow chip is put into a good MPU, strange behavior such as inconsistent boot ups, incorrect score display behavior, among other things can result from the RAM not being able to keep up with the demand from the CPU. Below is a list of 5101 RAM chips and their speed. A lower number means a faster chip. A Stern MPU-200 board needs 2 chips of at least 450ns, while the Bally AS 2518-17 or -35 and the Stern MPU-100 can work correctly with a slower chip of 650ns. The stern mpu-200 board should have matching speeds for the 2 RAM chips, as they are selected and accessed simultaneously. A faster chip is fine for a replacement, but there will not be a performance enhancement. It is usually best that the speeds of the RAM chips match (eg, 450ns and 450ns, not 450ns and 150ns), or there could be strange side effects, such as strange sound behavior and audits not saving correctly to RAM. 

*PCD5101P (Philips manu) 150ns
*5101-1 450ns
*5101L-1 450ns
*5101L-2 450ns
*5101-2 450ns
*5101 650ns
*5101L 650ns
*5101-3 650ns
*5101L-3 650ns
*5101-8 800ns (too slow for any board)

The 5101 RAM chip is especially sensitive to static discharge that will damage it, so take extra precaution in handling.

The memory RAM replacement chip sold by Tom Callahan at pin-logic.com (now offline) uses a 6116 and special adapter, and makes a good replacement. Pin-logic also sells the static ram chips that do not require batteries for backup; although he advertises that these do not work in the Stern MPU-200 board, 2 of them did work on a test board. Another source for varying types of 5101 and 6116 replacements is a blog site [http://warpzonearcade.com/?p=392 WarpZoneArcade]. There is information how to roll-your-own 5101 replacement adapters. Or, visit its accompanying site, [http://pinforge.com PinForge] for pre-made RAM adapters. A source for [http://www.pinitech.com/products/stern_mpu200_ram.php MPU-200 pre-built adapters is Pinitech]. Here is a list of [[MPU_Battery_Replacement_Options#Products|additional sources for NVRAM adapters]]. 

If you opt to go for a (recommended) NVRAM solution, a highly recommended modification (after discarding the battery!) is to power the NVRAM directly from the +5V line and remove the 12V line circuitry. This can be easily accomplished by cutting out R11. And then cut out CR5 and CR7 and replace these two with jumper wires (or 0 ohm resistors).

=====Fourth and Fifth flashes=====
Next, the program tests each of the 2 6820/6821 peripheral interface adapters (PIAs) at U10 and U11, starting with U10. The PIAs are set to a known state, then data is stored and read back from them to verify their registers are functioning properly. It is important to note that it is not possible for the PIA to be 100% tested with this test, as external data would have to be fed in to do so. However, the test will at least test the internal registers. It would be possible for a PIA to pass the self-test, but still not work properly with external inputs. 

Assuming the PIAs pass, the fourth (U10) and fifth (U11) LED flashes occur. The LED itself is connected to the U11 PIA. So if the LED is locked on, U11 might be bad. It's worth letting a locked on LED board 'sit' for a minute or so to see if the game boots all the way up without flashing each test step. This is an example of how a PIA can pass self test but still be bad. The LED control pin has no feedback as to if the LED is in fact flashing. 

Because the PIA tests all possible values in all possible registers, anything connected to the registers will be activated very briefly as well. This manifests itself most obviously via the flipper relay which on most games will click during the U11 PIA test. Holding the flipper buttons in will usually result in a flip or half-flip during this test. This could be helpful if purchasing a machine/repairing one in a noisy environment and you want to see how involved you might getting before removing the backglass to visually see the LED diagnostic flashing. 

=====Sixth flash=====
The sixth flash waits for an external input on U11 pin 40 from the display interrupt generator circuit, which occurs 320 times a second. If you're missing the sixth flash, there may be a problem with either the U12 circuit, '''OR''' the input pin on the PIA. A logic probe, oscilloscope, or a multimeter on pin 40 can help you determine which is at fault. A logic probe will pulse if the display circuit is operating; the scope will show you the signal's waveform; and the multimeter should settle on a voltage somewhat between 0-5 volts. 

One definite reason for lack of a sixth flash is a poor connection on the ground side of C16, the film capacitor. If there isn't a sixth flash, but all other tests and measurements are good, it's a safe bet that U11 is bad and needs to be replaced. 

Note that the sixth flash does '''NOT''' check for the proper '''frequency''' of operation of the display generation circuitry. As long as there is a pulsing signal (technically, ONE state change), the test is marked good and the program allowed to continue. 

=====Seventh flash=====

Note: Before troubleshooting further, if testing on the bench with only +5 and +12V applied, a 7th flash will not happen even if the MPU is fully functional. The 7th flash requires the +43V solenoid voltage.

For bench testing, it is possible to "trick" The MPU into completing the 7th flash without applying the solenoid voltage by temporarily jumpering the top of R17 and the top of R23.

The 7th and final flash waits for an external input on U10 pin 18 from the zero crossing detector circuit, which occurs 120 times a second (as the AC waveform passes or "crosses" 0 volts). Diagnosis of issues with the 7th flash are similar to the 6th flash. The input to pin 18 can be measured to determine if the signal is present or not. A signal present, but no flash could mean a bad U10 PIA. Again, a missing signal usually points to missing solenoid voltage. The source of the zero crossing signal is derived from the solenoid voltage delivered from the rectifier board. Equally, if a signal is present, there may be an issue with the zero crossing detection circuit itself.

Note again that the seventh flash does '''NOT''' check for the proper '''frequency''' from the zero crossing detector. It simply checks for a pulsing signal, and only checks for '''ONE''' transition.

After the 7th flash, the program does some background setup: reads dip switches, enables the displays, attract modes, switch scanning etc. in a 'game over' mode, waiting for player input. The LED will sometimes be dimly glowing or even pulse as this happens, which is not a cause for alarm. The LED circuit around Q2 can be rebuilt if this is concerning, but it is harmless.

One interesting anomaly is that the 7th flash will not occur, if there is a bad 1N4004 diode (CR3) used on -32 / -50 sound boards. On these two sound boards, the +12VDC used on the boards is derived from the +43VDC solenoid voltage, and isolated by CR3.
 

[[File:R113_and_R16_on_bally_-35.jpg|300px|left|thumb|Bally MPU with burned R113 and R16]] 
If there is +43VDC solenoid voltage present, but no 7th flash, check R113 and R16 on the MPU. These two resistors take the 43v and form a voltage divider. If these resistors burn they can stop the 7th flash from happening. Test point 3 should show approximately 21.5 pulsating DC if the resistors are ok.
 

If there is still no 7th flash and there is 21.5 VDC on TP3, check CB1 which is on U10 pia pin 18. It is the logic side of the zero crossing and should be pulsing. If it is stuck low or stuck high replace u14.
 

====Chip Sockets====
Reliable socket connections are a requirement for any printed circuit card to work as designed. Old sockets, as discussed below, should be replaced. Use extreme care in desoldering the old sockets, the traces and pads on Bally Mpu-17 boards are easily lifted. It is possible to lift other boards' traces and pads as well, especially if any battery corrosion is in the area.

The chip sockets on old Bally and Stern boards (also most any board of this era) are long past their reliable lifetimes. They may work, but they may also cause intermittent connections that will have you chasing your tail tracking down odd problems with your game. Like the 40-pin interconnect used in Williams System 3-7 games, these sockets should always be replaced. On Bally/Stern MPUs, these include U2, U6 (more game ROMs if you don't combine the ROM images), U7 RAM, U8 5101 RAM (and U13 5101 RAM if a Stern MPU-200), U9 CPU, U10 and U11 6820/6821 Peripheral Interface Adapters. 

Perhaps the most maligned socket brand, and rightfully so, is the Scanbe brand. In the picture below, you can see why. These 30+ year old sockets passed the point of reliability many years ago. Included in the Scanbe socket picture below are two pins pulled from a Scanbe socket. The pins were designed to grip the SIDES of the IC legs, unlike the design of modern sockets that grip the front and back faces of the IC leg. Get rid of them now.

<center>
<gallery widths=400px heights=400px perrow=2 caption="Poor quality and old sockets found on many early pinball machine circuit boards">
File:Bally MPU Sockets Orange.JPG|<center>It's hard to believe that these "brown" sockets ever worked.</center>
File:Bally MPU Sockets Augat.JPG|<center>The spring strength of the pins in these AUGAT sockets eroded over time.</center>
File:ScanbeSocket.jpg|<center>Closeup of the infamous "Scanbe" brand socket. "Scanbe" is molded into the top of the socket face.</center>
File:SternCraptasticSocket.jpg|<center>This style of Molex socket is particularly troublesome. Like Scanbe sockets, they don't work well after many years and the legs are so large that they are almost as hard to remove as a "WPC Snap Cap" without damaging the delicate through holes found on Stern MPU-100 MPUs</center>
</gallery>
</center>
 
<center>
<gallery widths=300px heights=300px perrow=3 caption="One Method of Socket Removal (works for at least ScanBe and Augat sockets)">
File:PryScanBeSocketOff.jpg|<center>Prying off an OEM Augat socket. Be careful to not crush/damage traces as you pry.</center>
File:HeatAndRemoveEachPin.jpg|<center>Heat and remove each pin individually.</center>
File:CleanThroughHoles.jpg|<center>Clean up the through holes with your favorite solder sucker. Here, a Hakko 808 is being used.</center>
</gallery>
</center>
 

====ROMs/ICs====
this is a stub

The Motorola part number equivalencies that appear on the top of U9, U10, and U11 are...
*SC44216P = 6800 microprocessor
*SC44067P = 6820 PIA

====Clock Signal====
replacement 9602 board: http://www.homepin.com/9602.html

replace with a 6802: http://pinballeon.com/6802/e6802.htm

===How to make a Benchtop power supply for the MPU board===
[[file:power_Supply_Connector.jpg|300px|left|thumb|ATX Power Supply connector modification]]
[[file:power_Supply_hookupR.jpg|300px|thumb|right|Bench Top Power Supply hooked up to MPU board]]
Being able to test the MPU board on the bench is a great advantage in trouble shooting. A benchtop power supply is quite easy and inexpensive to put together. All that is required is a computer supply and some mods to the connectors. An ATX or old AT computer power supply will supply the + 5 vdc and +12 VDC that is needed to run the first 6 flashes. The 7th and final flash requires +43 vdc and cannot be supplied by the ATX power supply, but the MPU can be "fooled" into thinking it is present. 
An ordinary ATX computer can be had used or new for under $20. Exact wattage is unimportant. In order to be able to switch the power on and off, the 20 pin connector on a ATX supply must be modded. This is not necessary on an older AT supply. Because modern motherboards use a soft power on/off, the green pwr-ON at pin 14 must be tied to the black COM ground at pin 13 or 15 thru 17. This can be done easily done with a short length of wire and a .062 pin attached to each end and shoved into the 20 pin connector at pin 14 and 15. Or, simply cut the wires free from the connector and solder them together.<bt>

Take one of the molex 4 pin connectors which have 1 RED wire (+5 vdc), 1 YELLOW (+12 vdc) and 2 BLACK ground wires. Attach an alligator clip to the RED, YELLOW and one BLACK lead. A good tip is to use the color coded rubber boots to protect from accidental shorts and keep it easier to identify the leads at a glance. If you should accidentally short the +12 volts to +5 via you will kill all the ICs on the board! 

To use the power supply, with the power OFF, clip the black lead to TP 4 at the top right of the board. Clip the RED +5 vdc lead to TP 5 at the bottom right, near the battery. Finally clip the YELLOW +12 vdc to TP 2 on the bottom left of the board. Make certain that this connector is not on or shorted to TP3 which is nearby. This error would damage the board, so double check this before turning on the power. Connect the power supply to 120vdc outlet and flip the switch to boot. 

Upon power up, the brief flicker should be seen, then 6 (not 7) more flashes for a good board. The 7th flash cannot be achieved without +43vdc present. On some occasions, the LED will lock on and not go into the flash sequence. This COULD BE because the MPU is sensitive to the exact voltage supplied and will not boot with a computer supply. If the board successfully boots in the game, this could be the cause. This condition is rare, but possible. Also, if the LED locks on immediately, try doing a manual reset by briefly shorting together pins 39 and 40 of the U9 CPU with a small screwdriver. This forces the pin 40 to go low and begin the boot process. It is also possible to short the junction of resistors R1 and R3, on the right side of R1, to board GROUND with a jumper clip to accomplish the same effect.
 

===Solenoid Driver Board Issues===
====Failed LM323K or Mission 5VDC====
While the LM323K (or 7805) is a reliable voltage regulator, periodically, they do fail. 
:::A discussion on replacing the LM323K can be found [https://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Driver_Board_LM323K_5V_Regulator here].

====Testing and Replacing Transistors====
[[File:Transistor_Replacement.jpg|300px|left|thumb|Before and After of Replaced Drive Transistor, Diode, and Resistor]] 
To test a transistor set the DMM to diode test mode. With the game turned off, place the black lead on the metal tab of the transistor. Probe the two outer legs of the transistor with the red lead. The DMM should read between .4v and .6v (some DMM will show 4xx - 6xx). The center leg should be a dead short to the metal tab. If either outer leg reads anything outside of the .4v to .6v range, the transistor more than likely needs to be replaced. Use a TIP-102 as the replacement transistor. 

If a transistor needs to be replaced it is usually a good idea to check / replace the 1n4004 diode and 330 ohm resistor associated with that transistor as these will often burn / short. Also check the diode on the associated coil, it is likely to be shorted as well.
 

The transistor output can also be tested by using the diagnostic LED on the MPU board. An alligator test lead and a component lead clipping or finishing nail are needed.
#With the power off, attach one end of the alligator test lead to TP6 located on the MPU board. TP6 is located in the vicinity of of the diagnostic LED.
#Next, attached the other end of the test lead to the component lead clipping or finishing nail.
#Turn the game on, and place it into solenoid test or just allow it to remain in attract mode.
#Carefully place the lead with the finishing nail into one of the many solenoid outputs on the solenoid driver board (J1, J2, or J5).

If the LED lights briefly as the solenoid test cycles, the transistor and header connection on the solenoid driver output is good.

If the LED does not light, suspect the following...
*a failed transistor,
*a cracked header joint,
*a discontinuity between the transistor and the header pin,
*the associated diode on SDB has failed,
*the 3081 transistor array on the SDB,
*the 74154 4 to 16 decoder on the SDB, or
*failed connections on J4 of MPU and / or J4 of the SDB, or bad daisy-chain connection at J1 of the sound board (if a sound board is used)

If the LED remains on, this means that the transistor is shorted. The exceptions are the diagnostic button return connection (ground) located at J2 pin 7, and the coin lockout coil ground at J2 pin 8. The coin lockout is a high resistance coil, and can remain on without destroying its associated drive transistor. 

The above test using the MPU diagnostic LED can be performed with the J1, J2, or J5 connectors connected or disconnected. '''WARNING: DO NOT place the lead on the J3 or J4 connectors on the solenoid driver board.'''
 

====Replacing a failed Solenoid Transistor====
If a coil has locked on, or any SE9302 (TIP-102) transistor has failed the diode test with your multimeter, replace the following components on the Solenoid Driver board as a set. In addition, also test the playfield coil disconnected from the game wires, with the ohm setting. The coil should have a value higher than 3 ohms up to around 15 ohms. Lower than 3 ohms is a dead short and will heat up and burn up components if the fuse does not blow. The coil diodes should also be replaced if the coil has locked on. Since the diode must be disconnected from the lugs to test it, it just makes sense to clip it off, replace the diodes, and not bother to test them. 1N4004 diodes or better, (1N4005,6 or 7) should be used. You cannot test the diode in place. The diode band (cathode) goes to the power lug of the coil, usually a double wire connection, because the coils are daisy chained. If it is a single wire, look at another nearby coil and note the color of the double wire. 

Replace any suspect SE9302 with a TIP-102 transistor. They are used in many pinball machines, so having a small supply of them is highly recommended. The TIP-102 is a more robust transistor and can handle more current. On the SDB replace the associated diode, and resistor for any driver transistor you replace. Check the associated pin for signs of burning and replace the header pins and connector pins if they have turned brown or look corroded. If a diode and/or resistor has actually burnt, check for continuity and make sure the circuit board traces have not also burnt up. This is a common problem when someone has over-fused the game. 

====Solenoid Transistor Mapping====
[[File:TransistorMappingThumb.jpg|300px|thumb|left|Bally Solenoid Transistor Mapping|link=Transistor Mapping for Bally Games]]
[[File:Stern_TransistorMappingThumb.jpg|300px|thumb|right|Stern Solenoid Transistor Mapping|link=Solenoid Transistor Mapping for Classic Stern Games]] 
To view a chart of what specific transistor controls a specific coil on a particular Bally game (transistor mapping), click the image at left. 
To view a chart of what specific transistor controls a specific coil on a particular classic Stern game (transistor mapping), click the image on the right.
 

==== Solenoid Driver Board Transistor, Resistor, Diode & associated Connector Chart====
{| class="wikitable"
|-
! TIP 102
! 1N4004 Diode
! 330 ohm Resistor
! SDB Connector
|-
| Q1
| CR1
| R9
| J1-pin 2, J2-pin 9
|-
| Q2
| CR2
| R6
| J1-3, J2-4
|-
| Q3
| CR3
| R16
| J2-5, J3-4
|-
| Q4
| CR4
| R18
| J1-5
|-
| Q5
| CR5
| R10
| J2-10
|-
| Q6
| CR6
| R12
| J2-11
|-
| Q7
| CR7
| R14
| J2-12
|-
| Q8
| CR8
| R20
| J5-10
|-
| Q9
| CR9
| R26
| J5-9
|-
| Q10
| CR10
| R28
| J5-15
|-
| Q11
| CR11
| R32
| J5-14
|-
| Q12
| CR12
| R30
| J5-13
|-
| Q13
| CR13
| R22
| J5-12
|-
| Q14
| CR14
| R24
| J5-11
|-
| Q15
| CR15
| R39
| Flipper Relay
|-
| Q16
| CR16
| R34
| J2-6, J3-7, J5-8
|-
| Q17
| CR17
| R42
| J5-7
|-
| Q18
| CR18
| R45
| J2-15, J3-9, J5-3
|-
| Q19
| CR19
| R47
| J2-8
|-
| '''TIP 102'''
| '''1N4004 diode'''
| '''330 ohm Resistor'''
| '''SDB Connector'''
|}

====Solenoid Driver Upgrades====
[[File:BallySternSDBupgrades.jpg|300px|left|thumb|Visual of Solenoid Driver Upgrades. Note that TP1 and TP3 are tied together.]]
There are several upgrades which can be performed to reduce stress on connectors. 

The two 5v test points on the SDB can be tied together. On the solder side of the driver board jump TP1 and TP3 together. Be careful to apply this to the correct test points. This eliminates a possible failure point on J3 pins 13 and 25. Note that TP1 is for the raw +5vdc coming directly from the regulator. TP3 is for the voltage that feeds all the +5vdc circuits in the driver section. If there's a problem in the driver section, it can be isolated by removing this jumper, and removing pin 13 or 25 from J3.
 

Next the C23 capacitor needs a common ground with the rest of the SDB. Jump the negative side of C23 to a convenient ground trace. On most boards there is a ground trace in the vicinity of the C23 negative lead. Other boards might require a longer jumper. Scrape the solder mask off the trace to get a good solder surface to solder the jumper. If replacing the C23 capacitor, (a good idea, they can be 30+ years old at this point), it may be possible to leave the negative lead "long" on the new capacitor. Then, bend the leg down to the ground trace, and solder it in both the mounting hole and the trace. 

The C26 capacitor needs a ground upgrade similar C23 mentioned above. Tie the negative side of C26 to the ground trace located at the perimeter of the board. This connects both C23's and C26's negative side to a common ground on the SDB. The goal of these modifications is to provide redundant grounds with the least resistance possible.

On the Stern SDU-100 and the older Bally AS-2518-16 boards there is a "gap" between pin J3-22 and J3-23. Both are ground connections. Use some additional solder and connect the two, bridge the "gap". Now all grounds (J3-18 thru J3-24) are tied together.
 

====How to Rebuild the Bally/Stern Solenoid Driver Board====
The Solenoid Driver board is critical to the operation of the electronics of the game. The Solenoid Driver Board (SDB) comes in several types for Bally and Stern, and are completely interchangeable for any game of the 6800 MPU type. The SDB supplies the game with the voltages for the MPU, coils and high voltage for the displays. Recommendations are given below for replacing components to ensure proper operation and reliability. In all cases, do the ground modifications as shown in another part of this Wiki.

'''Minimum Recommendation for a Working board'''

:At a minimum, replace both large capacitors on a working or non-working board, especially if they look original. Original caps are often metallic blue or metallic silver, and are at least 30 years old and due to fail, owing to the electrolytic chemicals in the capacitor drying up. The capacitor at C23 has a factory value of 11,000uf and 20 volts, but these values are not easily found these days. An electrolytic capacitor of between 11,000uf and 16,000uf and 25 volts or greater can be safely substituted. A screw terminal capacitor makes for a easy installation, but a snap cap with leads can be used as well. Recent prices for screw terminal caps have increased greatly so this may be a factor in your decision.

:The high voltage capacitor at C26 has an original spec of 160uf and 350 volts and is an axial electrolytic capacitor. Once again, this part is difficult to encounter with these exact specs, but an axial or radial cap from 150uf to 180uf and at least 350 volts can substitute. 400v or 450v caps can be had in a radial format and size that will fit. With a radial cap you will have to make leads that bend back to the negative (-) solder pad.

'''Preferred recommendation for a working board'''

[[File:BallyAndSternFracturedSolderJoints.jpg|300px|right|thumb|Clearly fractured .156 header pins on a Bally single sided driver board]]
:Besides the above, replace ALL the .100 and .156 molex header pins and the connector terminals in the nylon housings with Molex TRIFURCON Phosphor Bronze tin plated crimp terminals (Molex Part# 08-52-0113 for 18-20 gauge Wire, and 08-52-0125 for 22-26 gauge) for the .156 connectors, and Molex .100 tin plated Phosphor Bronze crimp terminals, (Molex Part#08-52-0123). Do NOT skimp on this step and just do one or the other. The receptacles can be re-used if not burnt. If replacing the receptacles, the locking or non- locking ramp type are fine. Often, the connector at J5 does not cover the last few pins. I don’t like this personally, although no harm can be done if the key is in place.

:Check every resistor that is usually covered by the plastic shield between the two big heat sinks for correct value and no sign of burn. Replace any that are suspect. Use the diode function on your multimeter to check the zener diode at VR1 and the 1N4004 diode. The zener diode can be difficult to source. See below for recommendation. 

'''Gold Standard for Working or NON-WORKING board'''

:It doesn’t make too much sense trying to trace down the exact problem and replacing only the bad components on a NON-WORKING board. Better to replace every possible bad component and start fresh. To ensure long life and proper operation of a working board, in ADDITION TO THE ABOVE, it is recommended that the components below are replaced regardless. Below is a list of components that effect the HV and +5 volt logic circuits on the SDB. Replace them all! * The Stern Revision J board is rather different, & a component list for that board follows. It can be identified by the extensive silk screening of each component and its function as seen in the 4th photo above, and by the HUGE 2 Watt and (2) large 1 Watt resistors. It is most often found on late date Stern games like Flight 2000 or Viper, etc.

'''Component replacement list for Bally AS2518-16 or -22 and Stern SDU100 SDBs, except * revision J'''

'''Resistors'''
*R51 22k ohm 1/2Watt
*R52 390 ohm 1/4 Watt
*R54 8.2k ohm 1/4 Watt
*R55 1.2k ohm 1/4 Watt
*R56 82k ohm 1/2 Watt
*R35 100k ohm 1 Watt

'''Diodes'''
*CR21 1N4004 400PIV 1 amp or better (1N4007, etc.)
*VR1 Zener diode 1N5275A 140 volts, 1/2 Watt. Can Sub 1N5275B or NTE 5099A

'''Transistors'''
*Q21 2N3584 250volts, 2 amp, TO-66 NPN
*Q22&23 2N3440 250 volts 1 amp TO-39 NPN
*Q20 LM323K (original 78H05KC or LAS1405)

'''Capacitors'''
*C27&28 .01 uf 400 vdc metal polyester capacitor

*RT1 25k ohm potentiometer (2 types) a 15mm black one, Piher Part# PT15LH06-253A2020 or a 6mm blue one BournsPart#3306P-1-253

'''Stern SDU100 revision J'''

*R35 100k ohm 1 Watt
*R51 33k ohm 2 Watt
*R52 390 ohm 1/4 W
*R53 2.4k ohm 1/4 W
*R54 8.2k ohm 1/4 W
*R55 1.2k ohm 1/4 W
*R56 82k ohm 1/2 Watt
*R73 3.3 ohm 1/4 W
*R74 470 ohm 1/4 W
*R75 100k ohm 1 Watt
*CR22 1N4004 or better
*Q24 2N3904 Transistor

Other diodes, transistors and capacitors as above for AS2518-18

====Modify the Display Fuse holder====
[[file:Fuse_adaptor.jpg|left|300px|thumb|alt=alternative text|Fuse adapter for the SDB allowing use of a common fuse]] 
Some versions of the solenoid driver board have a small fuse present for the displays. This fuse is a difficult to find, expensive, type 8AG 3/16 amp fast blow fuse. It would be best when rebuilding the SDB to replace the fuse holder with new clips and convert it to a more commonly available 3AG type. The original value of 3/16 amp can be substituted with a more common 1/4 amp fast blow fuse without worry of over fusing the circuit, due to inherent variations of tolerance by the manufacturer. 

Perform the following to replace the existing 8AG fuse holder:
*Bend up or clip off the upper solder lead of the clip
*Move the TOP fuse holder up one hole
*Solder a 20 ga. wire from the base of the clip back down to the lower hole. 

Be careful not to solder the clips with the inner "ears" facing in the wrong direction, or the work will have to be redone. It may be helpful to put an old 3AG fuse in the clips to aid in spacing, and assure that the "ears" are positioned correctly. The fuse will also hold the clips in place while soldering. See the photo above. Of course, an inline fuse holder can also be used instead, but looks less professional.
 

===Solenoid problems===
Before proceeding to diagnose solenoid or problems, see this section: [[General#How_coils_are_driven| How coils are turned on]]. 

One very common issue with solenoids not functioning on the playfield is a blown fuse under the playfield. This fuse, typically a 1 amp slo-blo, powers all of the solenoids on the playfield, except the flippers. The symptom of a blown playfield fuse is when the flippers, knocker, coin lockout relay, and chimes (if the game uses chimes) function in solenoid test, but no other solenoids will enable.
 

====Game starts, ejects ball, but no other playfield coils or flippers work====
On early Stern games, if the symptoms include all these:
* There are no blown fuses
* The game boots
* The driver board relay engages
* The coin door relay engages
* When a game is started it ejects a ball into the shooter lane
* No other playfield coils work
* The flippers don't work

Be sure to check the backglass for the tilt lamp to make sure the game isn't in tilt. If it's on (or if the lamp isn't working) check the slam tilt switches and ball tilt switch. It's possible that the ball on the ball tilt assembly got stuck at the rear of the assembly.

====Solenoid Expander Board and Diodes at the Coils====
[[File:BallyEightBallDeluxeSaucerCoilDualDiodes.jpg|300px|thumb|left|Bally Eight Ball Deluxe Limited Edition Saucer Coil showing dual diode connections at the coil lugs.]]
[[File:EightBallDeluxeDualDiodeSchematic.jpg|300px|thumb|right|Bally Eight Ball Deluxe Limited Edition Schematic snippet showing dual diode connections and 6 coils multiplexed by the solenoid expander board relay.]] 
The solenoid expander board allowed additional coils to be installed in games beyond what was originally supported on the driver board. The relay essentially worked as an A/B switch for two banks of coils. Each return line could then control two different coils, depending on which way the relay was switched.
 

===Lamp problems===

====Lamp Sockets====
Most lamp problems stem from the sockets themselves. The recommended best practice for problem sockets is to replace them. If you want to try and get them working reliably, here are some things you can try. 

First off, clean the inside of the socket. There are nice dremel tool tips to help, but even a screw driver can scratch off some crud from inside a socket. Sometimes a light squeeze on the socket with pliers can make the bulb stay in nice and snug and be less likely to move and stop lighting. 

[[File:Fixing_Lamps.jpg|300px|left|thumb|Repairing Single Lamp Sockets]]
The bare wire running under the playfield for controlled lamp power carries 5-6 vdc and is usually soldered onto the sockets mounting bracket. The mounting bracket then connects to the outside of the socket. After 30 years or so the connection from the mounting bracket to the lamp socket's outside can break. To remedy this there are two things you can try. You can solder the barrel of the lamp socket directly to the base of the socket (so it can no longer swivel). This can be kind of tricky without a higher power soldering iron - if you use paste flux it is easier. Radio Shack also sells a solder called "Crystal Clear" flux which works well. To do this well, you need to either sand or file (the file works best and saves your fingers) the area to be soldered on the base and the barrel. The other option is to run a small jumper wire that connects the bare wire directly to the outside of the socket, thus eliminating the poorer connection between the mounting bracket and barrel. 

Another less common issue is the connection between the lamp socket's solder lug (insulated wire to the driver board connects here), and the back tip of the socket (what moves out/in and is spring loaded to hold bulb in place). What you can do here is to move the insulated wire off of the lamp socket's solder lug and solder it directly to the back of the socket tip. This eliminates any potential connection issues with the solder lug/tab and the back pin. 

Before soldering onto a socket, either the barrel or the spring terminal, it must be sanded or filed clean or the solder will not stick. Paste flux or the crystal clear flux solder recommended above will help. If you have a temperature controlled soldering station crank it up above what you would normally use for boardwork to about 800 degrees.
 

[[File:Lamp_Mounting_Brackets.jpg|300px|left|thumb|Repairing Multiple Lamp Sockets Tied Together]] 
Another issue is the multiple lamp mounting boards/brackets like those used in Stern Big Game, Meteor, and others. The lamp sockets are riveted to these mounting boards and are not replaceable. These mounting boards suffer from a bad connection to the bare controlled lamp wire running under the playfield. You can either solder each lamp barrel to the base plate or run a daisy chain wire from barrel to barrel to help fix issues with the sockets. Again, lamp sockets need to be sanded (200 grit works well) or filed before solder will stick.
 

==== General Illumination (GI) Problems ====

[[File:BallyBurnedGIHeader.jpg|left|thumb|300px|The primary cause for General Illumination problems...burned connectors.]] 
One of the main reasons for lack of GI in Bally/Stern games is burned connectors on the rectifier board. If your game's GI connector looks like the one pictured at left, it's time to replace it. Generally, it's good policy to replace both the male header pins and the pins within the female plug.

The female plug can be reused if not too toasty. Using a small flat blade screwdriver, drive the blade through the slot where the pin's "tang" locks it into place. This will release the tang and smash the old pin. Only moderate hand pressure is needed to accomplish this. Once the tang has been released, the wire and pin should pull from the female housing easily. Crimp a new TriFurcon pin on to improve connectivity. Be sure that the "key pin" is installed on the female plug in the right location.
 

==== Controlled Lamp Problems ====

=====Lamp Driver Board SCR / Connection Chart=====
{|class="wikitable"
! scope="col" | SCR
! scope="col" | MC14514
! scope="col" | Connection
! scope="col" | SCR
! scope="col" | MC14514
! scope="col" | Connection
! scope="col" | SCR
! scope="col" | MC14514
! scope="col" | Connection
! scope="col" | SCR
! scope="col" | MC14514
! scope="col" | Connection

|-
| Q1 || U1 || J1-24 || Q16 || U1 || J2-22 || Q31 || U3 || J2-2 || Q46 || U4 || J3-18
|-
| Q2 || U1 || J1-25 || Q17 || U2 || J1-11 || Q32 || U3 || J3-27 || Q47 || U4 || J2-10
|-
| Q3 || U1 || J1-26, J2-21 || Q18 || U2 || J2-20 || Q33 || U3 || J2-11 || Q48 || U3 || J3-16
|-
| Q4 || U1 || J1-28 || Q19 || U2 || J2-15 || Q34 || U2 || J1-2 || Q49 || U3 || J3-17
|-
| Q5 || U1 || J2-16 || Q20 || U3 || J1-13 || Q35 || U2 || J1-3 || Q50 || U4 || J3-12
|-
| Q6 || U1 || J2-14 || Q21 || U2 || J1-12, J2-12 || Q36 || U3 || J3-26 || Q51 || U4 || J3-15
|-
| Q7 || U1 || J1-27, J2-13 || Q22 || U2 || J1-10 || Q37 || U3 || J2-23 || Q52 || U4 || J2-5, J3-13
|-
| Q8 || U1 || J1-23 || Q23 || U2 || J1-4, J2-8 || Q38 || U3 || J3-25 || Q53 || U4 || J2-3, J3-14
|-
| Q9 || U1 || J1-14 || Q24 || U2 || J1-5 || Q39 || U3 || J2-4, J3-24 || Q54 || U4 || J3-11
|-
| Q10 || U1 || J1-15 || Q25 || U2 || J1-6 || Q40 || U3 || J2-9, J3-22 || Q55 || U4 || J3-9
|-
| Q11 || U1 || J1-16 || Q26 || U2 || J1-7 || Q41 || U3 || J3-20 || Q56 || U4 || J3-10
|-
| Q12 || U1 || J1-19 || Q27 || U2 || J1-9 || Q42 || U3 || J3-21 || Q57 || U4 || J3-1
|-
| Q13 || U1 || J1-17 || Q28 || U2 || J1-8 || Q43 || U3 || J2-7 || Q58 || U4 || J3-2
|-
| Q14 || U1 || J1-18 || Q29 || U2 || J1-1 || Q44 || U3 || J3-19 || Q59 || U4 || J3-4
|-
| Q15 || U1 || J2-23 || Q30 || U3 || J2-6 || Q45 || U4 || J2-1 || Q60 || U4 || J3-3
|}
 

===== Failed Lamp SCRs =====
[[File:Mcr106_subbed_for_2n5060.jpg|300px|left|thumb|Using an MCR-106 in place of a 2N5060]]
Lamp locked on 
The usual cause for a lamp that is stuck on is a failed SCR. Bally/Stern employed two different SCR parts to control lamps. The MCR-106 is able to drive two lamps at the same time. The smaller 2N5060 will drive one lamp only. These SCRs fail from sinking too much current, from old blackened bulbs (which draw more current) or from being shorted to something under the playfield carrying high voltage (solenoids). If you accidentally short several lamps together, this can cause the SCR to fail also. 

If you are in a bind it is possible to use an MCR-106 in place of a 2N5060, with one caveat. Two legs of the MCR-106 SCR need to be reversed. As you are looking at the board the top and middle leg of the MCR-106 need to be reversed.
 
'''<nowiki>**Note:</nowiki>''' a 2N5060 '''CANNOT''' be used instead of an MCR106 which drives more than one lamp.
 

Lamp never lights 
A lamp that never lights might be caused by a failed SCR or the connection from the lamp driver board to the lamp socket. Use your meter's continuity test to "buzz" the path from the SCR to the lamp itself. Lack of continuity means that either the lamp driver board male header/female housing connector or the wire from the female housing to the lamp socket is severed. 

Some lamp boards feature buffer and (4514) decoder chips. A failed buffer or decoder chip can prevent a lamp from lighting. If you have multiple lamps out, and you have tested the wiring for each, look back to the chips to see if the lamps in question share a chip in common. Refer to the game's schematics. If so, and the SCRs have tested good, the chip may have failed. A logic probe is the best tool for this diagnosis.

[[File:LampDriverBoardCrackedHeaderPins.jpg|left|thumb|300px|A Bally Lamp Driver board with clearly cracked header pins. Cracked headers like these cause the lamp to be intermittent or to not light at all.]] 
The .100 headers on lamp driver boards are subject to a lot of stress. This is mostly because the backbox cabling has typically been liberated from the "tie downs" that were installed at the factory. The constant pull of gravity, vibration, etc, generally causes the top or lower several header pin solder joints to crack. You can attempt to "reflow" the solder on these joints, but they don't take solder well. The absolute best course of action is to replace the header pins since in addition to cracked solder joints, the header pins themselves lose their plating, another source negative impact on reliability. 

[[File:Bally LDB MCR106.JPG|left|thumb|300px|Bally Lamp Driver board using MCR-106 SCRs]]
[[File:Stern LDB MCR106.JPG|right|thumb|300px|Stern Lamp Driver board using MCR-106 SCRs]] 
Pay close attention to the orientation of an MCR-106 when replacing one. Bally and Stern lamp driver board MCR-106s are installed facing opposite directions. T106 SCRs in a TO-202 package (the style with an extended metal tab) are easily oriented per the board silkscreen.
[[File:MCR-106OrientationBallySternLampDriverBoard.jpg|left|thumb|300px|A Bally/Stern lamp driver board, showing proper orientation of smaller MCR-106 SCRs. Note the position of the metal part of the component relative to the silkscreen.]]
 

===== Testing Lamp Driver SCRs =====
Testing a 2N5060 (also 2N5061, etc)
[[File:2N5060Test.jpg|300px|thumb|left|Testing a 2N5060]]
*Set the DMM to diode check
*Place the red lead on the center leg (the "G" leg)
*Place the black lead on the lower left lead (the "C" leg)
*A measurement between .5 and .8 should be displayed.
*Place the black lead on the center leg (the "G" leg)
*Place the red lead on the lower left lead (the "C" leg)
*A measurement between 1.4 and 1.6 should be displayed.
*Readings outside of these ranges (generally dead shorts, sometimes opens) indicate the part has failed.
 

Testing an MCR-106
[[File:MCR-106Test.jpg|300px|thumb|left|Testing an MCR-106]]
*Set the DMM to diode check
*Place the red lead on the left leg (the "G" leg)
*Place the black lead on the right lead (the "C" leg)
*A measurement between .5 and .8 should be displayed.
*Place the black lead on the left leg (the "G" leg)
*Place the red lead on the right lead (the "C" leg)
*A measurement between 1.4 and 1.6 should be displayed.
*Readings outside of these ranges (generally dead shorts, sometimes opens) indicate the part has failed.
 

===== No Controlled Lamps Working =====
If all of the controlled lamps are not working properly in the backbox, on the playfield, or both, this could be due to several reasons. Bad / marginal connectors, either on the rectifier board itself (male header pins) or the female housing that connects to it. A bad lamp bridge rectifier or blown controlled lamp fuse on the rectifier board could cause this too. The easiest way to determine if the controlled lamps are receiving the proper voltage on the playfield or backbox is to probe the bare controlled lamp bus wire (make certain to probe the controlled lamp bus and not the general illumination bus) on either or both areas with the red lead of a DMM. Then, connect the black lead of the DMM to a known, solid ground. Voltage should read approximately in the 6-8vdc range. 

Additionally, if the +5vdc is missing on the lamp driver board, no lamps will light. Only one incoming pin (pin 3) on the J4 connection (upper left connection on board) of the lamp driver board carries the +5vdc. Check for the presence of +5vdc at TP1 of the lamp driver board. 

Finally, the lack of a solid ground on the lamp driver board will also cause all lamps not to light. Most all of the different variations of the lamp driver board have the grounds secured via the screws which fasten the board to the backbox. However, the second generation of the Bally lamp driver board, the AS-2518-23, does not have these extra ground points. Since all of the lamp driver boards are interchangeable, there is the potential to have any one of the boards in the backbox. Pins 1, 2, and 11 of the J4 connection (upper left connection on board) carry the incoming grounds for the lamp driver board. The grounds originate from pins 3, 4, and 14 at connector J3 of the rectifier board.
 

===== Dim controlled lamps =====
The biggest cause of dim controlled lamps is a weak connection via the power chain's connectors. The original lamp driver bridge rectifier is slightly undersized on the rectifier board at 8 amps; either changing to #47 bulbs can alleviate some of the load placed on this bridge, or it can be upgraded to a larger capacity (25 amp or higher). Changing the header pins on the rectifier board to a 10 amp capable pin plus changing the connector pins to Trifurcon connectors will help the power chain. Application of a dielectric to prevent oxidation can help prevent new pins from prematurely wearing out, but do not apply any chemical to old, tarnished pins. 

The fuse clips on the rectifier board can get tarnished, too. Replacement with high current phosphor-bronze clips will help dimming issues. The less resistance in the power chain the better and brighter your lamps will be.

Another thing that can cause dim controlled lamps is a partially failed BR1 on the power transformer module assembly. Measure the voltage at TP1 on the power supply board--if the voltage is found to be about 2.5-2.8vdc, also measure it for AC voltage. If it reads 2.5vac on the test point, replace BR1. What happens is one of the diodes in the bridge fails open and causing an AC bias to be on the DC voltage pushing the voltage down when the AC wave goes opposite to the DC voltage.
 

===== Lamp Driver Board Attacked by Battery Corrosion =====
[[File:Lamp_board_battery_corrosion.jpg|300px|left|thumb|Lamp Board Attacked by Alkaline Corrosion]] 
[[File:Bally AS-2518-23 Bat Damage.JPG|300px|right|thumb|Lamp Board Traces Attacked by a Leaky MPU battery]]
Corrosion can drip down from the battery on the MPU board to the lamp board. Corrosion that has seeped into the SCR's can cause them to act erratic, (such as not fully turning on, or not fully turning off the controlled lamp) not switching the lamp on (even if the lamp is replaced), or a lamp being "stuck" on. If this erratic behavior is happening, inspect the lamps SCR for green/black corrosion on the legs and metal backs. Replace any components with signs of corrosion on them, even if they seem to operate normally--they will eventually fail.

Although it is not nearly as common, a leaky battery can destroy the traces on the solder side of the lamp driver board. If everything else has been checked regarding some lamps not functioning, remove the lamp driver board from the game, turn the board over, and inspect the board traces. Primarily the top horizontal traces are the most susceptible to alkali damage. Since alkali damage is very unpredictable, any of the other areas of the board may be damaged.
 

=====Testing Lamp Outputs=====
The group who designed the Bally boardset was a crafty bunch! Did you know that there is already a built in set up to test a lamp driver output? The diagnostic LED on the MPU board can double as a lamp output tester. What is needed is an alligator test lead and a component lead clipping or finishing nail. With the power off, attach one end of the alligator test lead to TP6 located on the MPU board. TP6 is located in the vicinity of of the diagnostic LED. Next, attached the other end of the test lead to the component lead clipping or finishing nail. Turn the game on, and place it into lamp test mode. Carefully place the lead with the finishing nail into one of the many lamp outputs on the lamp driver board (J1, J2, or J3). If the LED lights, the SCR and / or the header connection on the lamp driver output is good. If the LED does not light, suspect either a bad SCR, a cracked header joint, or a discontinuity between the SCR and the header pin. Pretty neat, huh?
 

===== Lamp-to-SCR (Silicon Controlled Rectifier) Mapping for Classic Stern Games =====

Click [[Lamp Transistor Mapping for Classic Stern Games|here]] to access a table showing the mapping from the Lamp Driver Board (LDB) SCRs to individual feature lamps for some classic Stern games.

 

=====Controlled Lamp Fuse Blows Instantly (With LED Adapter Add-on Boards)=====
If the fuse for the controlled lamps blows almost instantly at power up, and there are LED adapter add-on boards installed on the lamp board connectors, it's possible that there is an issue on one or more of the add-on boards. Remove each add-on board individually to isolate which one might be causing the problem. Check for solder splashes or solder bridges on the suspected board(s). Also, if the add-on boards have SIP resistor arrays/networks, it's possible one or more of these components may have failed.

===AS-2518-147 Combo Solenoid/Lamp Driver Board===
The AS-2518-147 is a combination Solenoid, Lamp, and Voltage regulator board. It is much like a AS-2518-16 or a AS-2518-22 board but includes some lamp driver circuitry.

====AS-2518-147 ground updates / bullet proofing====
The following are several ground updates to aid in reducing current stress on the connectors of the -147 combo board. Applying these ground mods should aid in reducing browned charred connectors and provide redundant grounds with the least resistance possible. 
[[File:AS-2518-147_gnd_bulletProofing-1.jpg|thumb|left|300px|AS-2518-147 overall ground-mod plan]]
 
<ol>
<li>The two 5v test points can be tied together. On the solder side of the driver board jump TP1 and J3-25 together. This eliminates a possible failure point on J3 pins 13 and 25. J3-25 is for the voltage that feeds all the +5vdc circuits in the driver section. If there's a problem in the driver section, it can be isolated by removing this jumper, and removing pin 13 or 25 from J3.
[[File:AS-2518-147_gnd_bulletProofing.jpg|thumb|left|300px|AS-2518-147 ground mods - Step 1 & 2]]</li> 
<li>The C4 and C5 capacitors need a common ground with the rest of the SDB. Jump the negative side of C4 to the above C5 negative trace and continue to the main ground trace on the edge of the board. Scrape the solder mask off the trace to get a good solder surface to solder the jumper.</li>
 
<li>Add a jumper from the large lampdriver ground trace to the main ground trace on the edge of the board. 
[[File:AS-2518-147_gnd_bulletProofing-3.jpg|thumb|left|300px|AS-2518-147 Step#3]]</li>
 
<li>Add a jumper from the solenoid driver section ground trace to the main ground trace. 
[[File:AS-2518-147_gnd_bulletProofing-4.jpg|thumb|left|300px|AS-2518-147 Step#4]]</li>
</ol>
 

===Switch problems===
[[File:Bally Stern switch matrix.png|thumb|left|300px|Bally / Stern 5 x 8 Switch Matrix]] 

Bally/Stern games use a switch matrix arranged as a 5x8 matrix for a total capability of 40 switches. Some games (Medusa, Spectrum, and others) have a sixth column of switches making a total of 48 switches in a 6x8 matrix. This guide will concentrate on the "normal" 5x8 matrix but the information applies also to the 6x8 matrix; the sixth column signal wire is merely in a different location, and for switch matrix troubleshooting purposes the information is interchangeable. 

Columns 0 and 1 are shared by the playfield and cabinet switches. Any problems with switches in these columns can be further diagnosed by disconnecting the J2 connector (playfield) or J3 connector (cabinet) to isolate the playfield, cabinet, or both from switch tests. Switch test on Bally/Stern machines is entered by pressing the self-test button on the coin door 4 or 5 times, depending on the game. The stock software in each game only shows the lowest switch number that's closed; multiple closures or an entire row/column closed will still only show the lowest switch number. (There is a special test rom available that will walk through all the closed switches one at a time).
 

Start a switch diagnostic test by removing all balls from a game and placing all drop targets into an upright position. Enter switch test and you should have a zero flashing on the match display, signifying no closed switches. Use the chart from the manual in your game if you see a closed switch to investigate why it's showing closed. 

Probable reasons for a stuck switch are:

* points or blades adjusted too closely/touching
* switch diode touching lamps/other wiring
* solder splashes/conductive debris on a switch
* shorted switch capacitor, if used 

Here is where disconnecting the playfield will help. If you disconnect the switch connector for the playfield from the MPU board (J2) and the stuck switch stays, you know the problem is not on the playfield. If the switch is in column 0 or 1, you might have a problem with the switch matrix going to the cabinet. It is common for switches on the coin door to become mangled, either being stuck closed or shorted to the coin door in some way. You can disconnect the coin door separately while in switch test to see if the switch faults clear. 

If you disconnect both J2 and J3 isolating all switches in the game from the MPU board, you should always see the flashing 0 indicating no switches closed in switch test. If you do not, there is a board fault that should be investigated and corrected. All of the signals for pulsing and reading the switch matrix originate and terminate at the U10 6821 PIA chip. As a quick test for this chip, you can swap it with the U11 PIA to see if the problem's symptoms change. If they do or the switch matrix starts to work correctly, you have a probably failed PIA chip and should replace it. Be aware that the U11 PIA chip controls the solenoids in the game, so if the U10 chip is bad in any way, you might have locked on solenoids causing more damage if your fuse doesn't blow. Before swapping the PIA chips, remove the solenoid driver board's .156 connectors to the solenoids to prevent damage. You could also just remove the J4 connector that feeds the solenoid driver board's input signals. (Lower right connector on the SDB). 

Sometimes due to wiring error a switch diode is reversed in the switch matrix, either from previous repair work, or even from the factory. When this happens, you will see the wrong switch closing. Test for this by entering switch test and activating each switch one at a time referencing the switch chart in the manual, ensuring that each switch reports the correct switch number. This means that each drop bank will need to be reset by hand after each drop target test. If the game in question has a spinner, test the spinner with the playfield down and then place a piece of paper between its switch points so testing other switches with the playfield up doesn't show a false positive on the spinner from movement. 

Momentary contact switches will sometimes have a switch capacitor installed. The purpose of this capacitor is to ensure the MPU board "sees" very quick hits to a tilt, pop bumper, sling, or standup target. Switch capacitors should not be installed on rollover, saucer, spinner, outhole, or trough switches. There are a few games that do have capacitors installed on these switches. You can cut these off safely and not worry about replacing them. 

A symptom of a failed (shorted) switch capacitor will be a stuck switch showing in the switch test, and no scoring/scoring once/multiple repeated scoring in gameplay. As a test, you can cut one leg of the capacitor off a suspect switch and see if the problem goes away. If it does, the capacitor was probably bad and you can replace it. (A 0.047 mfd 16 volt or higher non-polarized ceramic disc replacement works well.) 

Quick hits to switches that do not have capacitors installed can have a capacitor installed to improve performance, or if you have a pop or sling that activates when hit but does not score. You can add the 0.047 mfd capacitor to these switches on the two lugs that do not have the diode installed; one end of the capacitor goes to the blade lug that has one end of the diode but not the matrix wiring, and the other end of the capacitor goes to the switch lug that only has the matrix wires without the diode. If you do add a capacitor to a sling or pop bumper, be aware that it is possible for radio frequency interference from a coil's collapsing magnetic field to be picked up by the capacitor, causing the switch to activate. This is most common with flipper coils - holding a flipper up and releasing generates a short pulse of radio frequency static. 

It is good preventative maintenance on machines that have switch capacitors to methodically replace each and every one with a new one. Adding a switch capacitor to pops and slings is a good idea also as you can run a slightly larger switch gap on the activation switches, which helps to prevent switch bounce and repeat, unwanted, activations.
 

=====Leaf Switch Theory,Operation and Adjustment=====

Leaf switches in pinball games come in 4 formats: Normally Open (N.O.), Normally Closed (N.C.), Break-Make, & Make-Make, the last 2 of which are really combinations of a N.O. and/or a N.C. switch. Regardless of their function, all switches are in fact, a N.O. or N.C. type.

Leaf switches in electronic games are of 2 compositions,at least 2 bronze blades each holding a gold flashed contact or a Tungsten contact. Since gold is a very high conductor of electricity, it is used on most switches, with the exception of the flipper cabinet and End of Stroke (EOS) contacts, which are tungsten. Gold will not tarnish or turn black, but sometimes gets dirty from solenoid dust, and this may effect its conductivity. Tungsten flipper contacts must be redressed with an ignition-type flat file as used in automotive repair, as the contacts are too hard to be smoothed by sandpaper or flex file abrasive. Gold flashed contacts must NEVER be cleaned with a file or sandpaper. A business card, or thin cardboard, is all that is necessary to clean electronic gold flashed contacts. If they seems to have a foreign substance on them, a Q-Tip with a degreaser like Mean Green, or alcohol can be used and then wiped off. Contact cleaner must NOT be sprayed liberally on the switch, but can be applied with a swab.

=====Normally Open (N.O.) Switch=====
[[file:SwitchNormallyOpen.jpg|thumb|left|Normally Open Switch in resting state]][[file:GenericSchematicSwitchDiagram.jpg|thumb|right|Schematic rendering of N.O. & N.C. switches]]
This is a leaf switch that has 2 contacts that complete a circuit when pushed closed by some mechanical device. The switch re-opens when the device moves away from the moveable contact, and the springiness of the blade opens the circuit. 

=====Normally Closed (N.C.)Switch=====
[[file:SwitchNormallyClosedLabelled.jpg|thumb|left|Normally Closed (N.C.) switch in resting state with optional nylon spacer]]
This type of switch opens a circuit when a mechanical device pushes against the blade. 

=====Break-Make switch=====
[[file:SwitchMakeBreakLabelled.jpg|thumb|left|Break-Make switch in resting state]]
This switch is really a composite of a N.O. and a N.C. switch with just three blades instead of four. The movable center blade has contacts on BOTH sides. Proper adjustment insures that when a device moves the center blade towards the open contact, the CLOSED switch OPENS BEFORE the center contact touches the open switch’s contact. When the pressure is released, the center blade returns to its N.C. side and re-makes contact. This type of switch is often used on relays. A Make-Break switch is really the same, just upside-down, or in reverse, of the order of actions of a Break-Make switch. Special care should be taken with a Make-Break switch that the three blades are not at any time shorted together. This can happen often when the blade stiffener is maladjusted, and contacts the other blade of the pair. Note that this type of switch is rarely seen in Bally/Stern solid state machines. 

=====Make-Make switch=====
[[file:SwitchMakeMakeLabelled.jpg|thumb|left|Make-Make switch in resting state]]
A make-make switch is a composite switch consisting of two N.O. switches using only 3 blades. When mechanical pressure is applied to the blade, the switch “makes” or closes the circuit, and continues to move until a second switch contact is closed, tying all 3 blades together. 

=====Adjusting Switch Gaps=====
Proper switch clearance gaps are crucial for correct operation of any pinball game. Very many problems in games come down to a problem with incorrect operation of a switch. The switch blades are made up of phosphor bronze, which has high conductivity, resilience to form and excellent soldering characteristics, but has the drawback of being brittle compared to copper. Switch blades therefore, are commonly broken by the game, or careless actions by the repair person. A switch adjusting tool, purchased or homemade, is a necessity. Pliers or screwdrivers might be used in special circumstances, or in extremis, but are not best practice.

Switches in games are designed to have a degree of over-travel, which creates a wiping motion that helps clean the switch. The contacts must meet, stay together and slide across the face of the contact slightly, to be perfectly adjusted. They also must be gapped wide enough that they do not bounce, causing multiple switch closures. This problem is seen often in electronic games, when the rapid nature of the switch closures cause machine-gunning of the slingshots .

Before adjusting switches, make certain the screws holding the switch stacks are down tightly. Bakelite spacers in the switch stacks, due to excessive moisture, have occasionally shrunk by drying out, causing poor adjustment. After tightening a switch stack, be sure to recheck the gap of each switch.

To adjust a leaf switch, first make sure the switch stack of bakelite or plastic spacers and blades are tightly packed against each other by giving the 2 screws a twist of your screwdriver. As long as there is no screw movement with reasonable pressure, you can procede. Some switches have a regular nut on the backside instead of a speednut, which will require holding it as you turn.

Using your switch adjusting tool, put twisting pressure on the moveable switch blade as close to the switch stack as possible, and include the blade stiffener(if present) in the adjuster slot. Try to use as little force and change of gap as possible, and incrementally reach your gap goal. Using too much force and a back and forth gap readjustment, tends to bend and weaken the switch blade, and can make a deformed switch blade difficult to set for correct operation. This is often seen in games that have been “hacked”, and sometimes the only way to remedy the situation is to replace the entire switch, or disassemble it entirely. Cycle and recycle the mechanical device that activates the switch and observe the switch for proper gap, wiping action and release.

=====Recommended Gap Specifications=====
Kicking rubber, or slingshot switches usually have a generous gap, at least 1/16", due to the rubber ring pushing back against the switch, and a bit of trial and error will be necessary to find the ideal gap setting. Pop bumper switches and scoring “dead” bumper switches, should have a gap of 1/64" for the actuating switch under the spoon, and a 1/32" gap for the score switch when open. Flipper cabinet switch have a generous gap which can be adjusted to suit the owner of the machine to provide a good "feel". All other types of switches will probably function well with a 1/32" gap, and this would be a starting point, modifying the gap on a case by case basis.

=====The Importance of Diodes and Capacitors on Switches=====
[[file:DiodeOrientation.jpg|300px|thumb|left|Orientation of Diodes]]
[[file:Ceramic_Capacitor.jpg|300px|thumb|right| A ceramic capacitor of the type used on switch. '''NOTE:''' The number is NOT the correct value for switches. Use 0.047 mfd for replacement]] 
On all Bally and Stern solid-state (SS) pinball games, there '''MUST''' be a diode connected to each pair of switch blades. The diode’s purpose is to isolate the switch from the other switches in the switch matrix. A shorted or reversed diode will cause the MPU to read the strobe signal on the wrong return line, causing a switch read error. 

Bally (and Stern) used a matrix of 5 columns (strobes, designated 0-4) and 8 rows (returns, designated 0-7) allowing for 40 switches. Some Bally games have a sixth column allowing for 48 total switches. The sixth column games re-use a signal pin from the earlier games that was the sound board address "E" pin. Stern uses this same pin for the 7th digit enable on their displays, and never used it for their sound boards. No Stern game has a sixth column of switches. 

Bally and Stern both state 1N4004s as original, but 1N4148 diodes can be used, and in some cases, were used from the factory.
 

=====Switch Capacitor Purpose and Failure=====
[[file:BallySternSwitchClosureCapacitor.jpg|300px|thumb|left|A typical standup target with an OEM switch capacitor. The capacitor is the green disk. The other component is the isolation diode.]]
[[file:BallySwitchCapacitor.jpg|300px|thumb|right|Schematic showing capacitor connections relative to switch and switch isolation diode. Image from Bally Silverball Mania.]]
 
Capacitors are used on switches that may open and close very rapidly, to lengthen the switch pulse that the MPU can read. Not all switches will have capacitors. Standup targets, pop bumpers, slings, and tilt mechanisms are switches that benefit from a capacitor. All switches that need a quick reaction can have switch capacitors added to them (such as rollover buttons). These are ceramic non-polarized capacitors with a value of .047 or .050 uf and 16 volts or greater. A commonly available cap is the .047 uf/50 volt through Mouser P/N 140-50U5-473M-RC.

The factory-installed caps are often damaged by the high wattage industrial soldering irons used in manufacturing of the games, or they succumb to the vibration over time and no longer serve their purpose of lengthening the switch closures so that the MPU can read them. Often times, a technician will clip the cap off to diagnose a stuck switch problem and not bother to replace it. The switch will still operate in this fashion for the most part, but might not always detect rapid or brief switch closures. For more sensitive play, the capacitor should be replaced. A failing cap can also make a switch bounce, and cause machine-gunning of a slingshot or pop bumper.

Sometimes the operation of the flippers or other solenoids will cause a phantom switch close on a pop bumper or slingshot. This is due to the way the software reads the fast react switches on those mechanisms. The RF produced by the flipper coil's collapsing EMF field is picked up by the switch capacitor, causing the pop or sling to fire. In most cases, no score is added; the mechanism just operates. Keeping the leads short on the switch capacitors might reduce their tendency to pick up this stray RF in the machine.
 

=====Proper Location of Wiring, Diodes, & Capacitors=====
Color coded wiring of the playfield switches will vary by game model and manufacturer, but the following should hold true for any Bally or Stern game made from at least 1977 to 1985 . Switches may have two or three lugs, depending on function. If the switch has 3 lugs, one of them is a '''DEAD LUG''', which is electrically isolated from the other switch blades and ground. It may be that the dead lug is off to the side, or positioned the same as the other lug, and it may be difficult to visually verify which is the dead lug. The Dead Lug does not have a blade. The purpose of the dead lug is to have a isolated soldering point for the '''COLUMN''' wire(s) and the '''NON-banded''' (anode) end of the diode.
[[file:BallySwitchwithDiode.jpg|300px|thumb|left|Switch capacitor is wired as shown, some switches will not have one.]]
[[file:SternSwitchwithDiodeCapac.jpg|300px|thumb|right|A stand up target with capacitor & diode]] 
A 3 lug switch will have the following connections.

* A switch capacitor (if required) between the 2 switch blades.
* A '''ROW''' wire(s), (with a capacitor leg, if needed) to one end of either switch blade
* A '''COLUMN''' wire (usually daisy chained) plus the NON-banded end of the diode to the DEAD LUG
* The '''BANDED''' (cathode) end of the diode to the opposing switch blade, either by itself, or sharing the lug with a leg of the capacitor
 

Remember that switches are usually daisy-chained together, so except for the last switch in a group, there will be a common COLUMN wire (sometimes NOT insulated) between each switch, along with the NON-banded diode. Any break is this wire will cause all the switches below it to not function. Keep in mind that the schematics show a logic progression of switches which may or may not match the physical chain under the playfield. A failed or leaky diode can only be tested for by desoldering one end of the diode & checking with the diode test function of your multimeter. It is very little more work to just simply replace the diode with new if it is suspected. 

=====Troubleshooting multi- ball games that will not start=====
There are Bally (and some Stern) multi-ball games produced which require ALL balls to be in the correct position before a game will start. If a pinball is stuck on the playfield, missing, or the switch does not register, is broken or maladjusted, then the game will not start. The symptoms each game shows varies. After the game boots, a few insert lights may flash repeatedly, or the game will not coin up, the general illumination will not light and credits will not count down, etc. Check the chart below for specific games.

These switches can be checked in the game diagnostic switch test see if they are stuck closed, or manually operated to see if they register. Remember that only the LOWEST number closed switch will appear on the display, so if other switches are closed or have a fault, they must be cleared to check for the higher switch number.

{| class="wikitable"
|-
! Game
! # of balls
! Symptoms
! Check switch
|-align=center
| Centaur
| 5
| All zeros on; displays flicker
| #01 Ball trough 4
#02 Ball trough 5
#08 Outhole (will start with #01 or #02)
|-align=center
| Elektra
| 2
| Will not start; displays blank
| #01 Outhole
#02 Left/Right of Outhole (Starts with #01 or #02)
|-align=center
| Embryon
| 2
| Always starts
| #05 Left/Right of Outhole
#08 Outhole
|-align=center
| Fathom
| 3
| Won't start; no GI, 2 insert lights flash, displays blank
| #01 Outhole
#02 Left of Outhole 1
#03 Left of Outhole 2 (Starts with #1& 2, OR #1&3)
|-align=center
| Fireball II
| 3
| Won't start; displays blank
| #01 Outhole
#02 Left of Outhole
#03 Left of Outhole
#18 Right of Outhole
|-align=center
| Vector
| 3
| Won't start; displays normal
| #01 Left of Outhole 2
#02 Left of Outhole 2
#03 Outhole
|-align=center
| Xenon
| 2
| Won't start; displays blank
Note that game will start with only ball release 1 switch (#02) closed.
| #02 Ball release 1
#28 Ball release 2

|-align=center
| Freefall
| 3
| Won't start; displays blank; credit display shows zeroes in all 6 positions
| #04 Outhole
#35 Left of Outhole 1 (closest to outhole) or #38 Shooter Lane
#34 Left of Outhole 2
#33 Left of Outhole 3 (closest to shooter lane)

|-align=center
| Flight 2000
| 3
| Won't start; all player displays show HSTD; credit display blank
|
#33 Outhole Right
#34 Outhole Center
#35 Outhole Left
|}

*Note: Neither Freefall nor Flight 2000 will go into test mode, until switches 33 (or 38 - shooter lane with Freefall), 34, & 35 are closed.
 

=====Electrical short troubleshooting Fuse helper=====

[[file:Circuit-Breaker-Adapter.jpg|300px|thumb|left|alt=alternative text|Circuit breaker with a blown fuse soldered in position]]As an aid to finding the cause for an electrical short, you can make a circuit breaker tool to eliminate the need to constantly replace a fuse, while you investigate the cause. This could save you money in the long run. It is better to under-fuse the connection by a small amount, then to use the rated fuse rating, so a 3 amp circuit breaker could be used on a 5 amp fuse holder, or a 10 amp breaker for a 20 amp G.I. fuse holder. The very small GMA fuses (5x20mm) will probably need some kind of jumper wire setup.

*a burned out fuse of any amperage or voltage (you were saving them just for such a thing!)
*a circuit breaker of 1, 3, 5, or 10 amps, whatever amperage you require for the circuit you are troubleshooting. Buy ones like Mouser P/N 691-CMB10311C3NBA (Carling) or 655-W57-XB7A4A10-10 (Tyco).

Solder the burned out fuse to the spade terminals of the circuit breaker as shown in the photo. Alternatively, make a two wire female spade mini harness, and solder the bare wires to each ends of the bad fuse and attach the circuit breaker that way.
 

===Display problems===

====Display High Voltage Section====
'''Bally High Voltage Section Repair''' 
WARNING: This circuit uses high voltages. Don't continue, unless you are confident in your diagnostic abilities.

'''WARNING: The case of the 2N3584 (Q21) high voltage transistor is live!!! Touching the case will result in a dangerous shock!!!''' Also, some Stern solenoid driver boards use very long screws to support the protective plastic over the HV section. These screws are not isolated from the case of the 2N3584 HV transistor. The screws / nuts which support the protective plastic are live! 

If all displays are blank, your high voltage (HV) section may not be working. On the Solenoid Driver Board (SDB), use a DMM to measure volts DC on test points TP2 and TP4, to determine if this section needs repair: TP2 = 150 to 190VDC TP4 = 230VDC +/- 25VDC If TP2 is less than about 150VDC or over 200VDC, the HV section is malfunctioning. It is worth mentioning that when the source display voltage rises above the core acceptable levels, the displays will still operate. However, the increased voltage will strain the display circuitry. In turn, the displays glass life expectancy will decrease dramatically. If TP4 is 0VDC, then power is not getting from the Power Supply board, and the problem is located either on the Power Supply, or in the wiring/connectors carrying power to the SDB, so you must correct this before working on the HV section. '''Replacing the components in the HV Section''' (TP2=0VDC or 230VDC AND TP4=230VDC) If you prefer to replace only the failed components, follow page 50 of the [http://gamearchive.askey.org/Pinball/Manufacturers/Bally/pdfs/ballyfo560.pdf Bally repair manual, F.O. 560], dtd 20 June 1977.
 Since there are not that many components, it is may be less time consuming to replace all the components in the HV section. Most of these components are located between the two large heat sinks. There is a school of thought when working with high voltage regulator circuitry that dictates replacing ALL the components, as a baked, tired, component can take out new components as well. This is one area where shotgunning the section might not be a bad idea. 
[[Image:HVSection.png]]

Check the [http://pinwiki.com/wiki/index.php?title=Pinball_Parts_Suppliers Parts Suppliers] section of the wiki to find suppliers, and get the following replacement parts (1/2 watt resistors can be substituted for 1/4 watt). 

{| border="1"
| align="center" | '''Part'''
| align="center" | '''Part No.'''
| align="center" | '''Location'''
|-
| Transistor
| 2N3584,250V,2A,NPN, note: a [https://www.greatplainselectronics.com/products.asp?cat=105 BUX-85G] may be substituted  
| Q21
|-
| Transistor
| 2N3440,250V,1A,NPN
| Q22,Q23(heatsink)  
|-
| Zener diode
| 1N5275A,140V,1/2W,10% or 1N5275B,140V,1/2W,5%
| VR1
|-
| Diode
| 1N4004,400PIV,1A
| CR21
|-
| Fuse
| 3/16A,8AG
| F1(-22 only)
|-
| Resistor
| 22k Ohm,1/2W,5%
| R51
|-
| Resistor
| 1.2k Ohm,1/4W,5%
| R55
|-
| Resistor
| 82k Ohm,1/2W,5%
| R56
|-
| Resistor
| 8.2k Ohm,1/4W,5%
| R54
|-
| Resistor
| 390 Ohm,1/4W,5%
| R52
|-
| Resistor
| 100k Ohm,1W,5%,metal film
| R35
|-
| Capacitor
| 0.01 uF, 400V metal polyester
| C27,C28
|-
| Capacitor
| 150 uF, 350V (if original, replace)
| C26
|-
| Potentiometer  
| 25k Ohm, PC-mount
| RT1
|}

Possible replacement parts for the HV-section are....

Q22 and Q23 are 2N3440 and is getting harder to find.
Replacement can be a TIP50, but be aware of the correct orientation (as with all transistors).
The use of a small heatsink is advised for Q23 (like Wakefield-Vette/291-H36AB).

Q21 is a 2N3284 (very expensive and hard to find).
A good replacement is a BUX85 mounted on the original heatsink (very easy to do, cut the middle leg).

The zener diode VR1 is a 1N5275 and is getting harder to find.
A good replacement is a Z4KE140A zener diode.

The adjustment pot RT1 (25K) is an open type and cause bad adjustment.
This can/should be replaced with a Bourns 3306P-1-203 (20K).

 '''Remove and replace components'''

* Clip the old components from the board (make sure you have new ones first).
* Use one of the desoldering methods to remove solder from the holes.
* Stuff board with new components.
* Check for correct orientation on transistors, diodes and the large capacitor if you replace it.
* Leave a little space under components for air flow.
* Bend leads on components so they won't fall out when board is inverted for soldering.
* Double check that all the correct parts are in the correct places and properly oriented.
* Solder the parts to the board
* Clip excess off leads

 '''Ready to test''' Prior to powering up and testing, remove all display connectors, or test with F1 removed from the SDB. I recommend connecting your DMM with a clip lead to TP2 prior to powering the game, so you don't have to probe the HV section. Power up the machine and verify TP2 voltage is 150VDC to 190VDC. If the correct voltage is read, power down the machine and reconnect all the displays and put F1 back in. Leave your DMM connected to TP2. Power up the machine and adjust RT1 so TP2 reads about 150VDC to 160VDC. If some of the displays no longer light, then adjust the voltage up until they are all lit. New displays may require to be burned in at 190VDC for an hour or two, but then the voltage can be reduced. The lower voltage will prolong the life of the gas plasma displays. If TP2 is not correct after your repair, you will need to recheck your work. If you cannot find a problem with your repair, then I recommend you follow the troubleshooting steps on page 50 of the [http://gamearchive.askey.org/Pinball/Manufacturers/Bally/pdfs/ballyfo560.pdf Bally repair manual, F.O. 560], dtd 20 June 1977.

After you have repaired your HV section and verified that it is providing the correct voltage, the next part of the wiki will address how to correct problems with the displays.

====Repairing Bally/Stern Displays====
This page will help you repair your Bally 6- and 7-digit displays. The information is focused on the AS-2518-21 display. Since the AS-2518-15 display is interchangeable with the "-21" display, everything mentioned here will apply to both displays. Bally 7-digit displays (AS-2518-58) work the same way, they just contain additional components to support the additional digit, and lighting of commas. Some Stern DA-100 6-digit displays are very similar to the Bally versions, and the information here will also work for them. The Stern 7-digit display is slightly different, as its circuit board is physically deeper than any of the other displays and is not directly interchangeable with a Bally 7 digit display. Additionally, there are some input pin differences; however, if you have the schematic you can use the information here on the display, some transistors might be labeled differently.

First off, let's make sure your malfunctioning display is even repairable. If the glass display itself is shot, there's not much that can be done except to replace it. Here's a couple of photos of things that can go wrong with the glass display.

[[File:B-disp-d1.jpg|center]]
<center>Burn spots on the digit segments - You can't fix these but you can live with them</center> 

[[File:B-disp-n1.jpg|center]]
<center>Broken glass nipple - This display glass is ruined</center>

Then there's the circuit board. Most if not all of the components can be replaced without much effort, but if there is damage to the circuit board itself, it may be impossible, or unreliable to repair.

[[File:B-disp-b1.jpg|center]]
<center>Burn marks on the driver board</center> 

[[File:B-disp-b2.jpg|center]]
<center>Underneath - The traces are a mess</center> 

So we're assuming you have displays that do not fall into the categories above. If your problem is with the digits not being displayed properly, and it's NOT the MPU's fault, then it can be fixed, and fairly easily too!

'''FIRST THING''' - Before you go any further, there are two things you should do to ALL your displays, even if they seem to be working fine. First, reflow the solder on the joints for the header pins. On the bottom side of the circuit board, just heat each header pin solder joint with your soldering iron, then add a little fresh solder. Be careful not to create any solder bridges between adjoining pins, unless there is already one there. Next, replace the six 100K ohm 1/4 watt resistors with 1/2 watters. They are the ones with the color code brown-black-yellow, and are labeled R1, R3, R5, R7, R9 and R11. You'll find seven of them, but only the ones I just listed need to be replaced. For 7-digit displays there will be eight of them, so replace R56 too, along with the six I just mentioned. 1/4 watt is just too small for their circuits and often they are overheated which causes them to change their resistance. On the photo of the burnt circuit board up above, the area that was burnt was under 3 of these resistors.

'''SECOND THING''' - Connectors, connectors, connectors! There are lots of signals going from the MPU to each display driver, and if these signals are not making it due to bad wiring or connectors, then your displays will misbehave. Check all the display driver connectors for loose or broken wires, burnt pins, busted connectors, and replace or repair anything that looks bad. Remember that some of the signals are daisy-chained from display to display, and a bad connection at one display can effect the others "downstream". Then check the J2 connector on the MPU, since this is where all the signals come from. Next check the J3 connector on the solenoid driver board. There's a high voltage regulator used by the displays on this board, and J3 is where it gets the 230 VDC from the power supply (pins 6 & 3) and feeds the regulated 190 VDC to the displays (pin 8). Finally, check the J3 connector on the rectifier board, since this is where the high voltage comes from. Connectors are always a big pain!

[[File:B-disp-hp1.jpg|center]]
<center>Header pin solder joints - Notice the cracks around the last two pins on the right</center> 

[[File:B-disp-hp2.jpg|center]]
<center>Header pin solder joints after being re-soldered - No cracks</center> 

[[File:B-disp-r1.jpg|center]]
<center>Can you find the six 100K ohm resistors (brown-black-yellow)</center> 

[[File:B-disp-r2.jpg|center]]
<center>Here they've been replaced them with 1/2 watt resistors of the same value (100K ohms)</center> 

Now we'll look at come common problems and briefly describe the cause, but I assume you've already replaced or checked the 100K Ohm resistors and re-soldered the header pins:

=====All displays are blank=====

Most likely cause of all blank displays is a lack of high voltage. First off, check F2 on the rectifier board. It's a 3/4 Amp slow blow fuse and it's test point on the rectifier board is TP2. You should read 230 VDC at this test point. If it's OK, then check the fuse on the solenoid driver board. The high voltage regulator's output is fused and if this fuse is blown then there's probably a short somewhere on one of your displays or the wiring harness. The high voltage regulator fuse is a 3/16 Amp, but it's a bit smaller (8AG) than a standard fuse, and a hard one to find. If the fuse is not blown, then the next thing to do is verify that at least 170 VDC is making it from the regulator to the displays. Check TP2 on the solenoid driver board. It should read between 170 and 190 VDC. If it does, then the regulator is working. While you're there, if your display glasses are not new, use the small trimmer pot on near the fuse and adjust the high voltage to be 170 VDC. Older displays work just fine on 170 VDC and it's less stressful.

Next thing to check is to be sure that the 170 volts is making it to the displays. Check connector pin J3-8 on the solenoid driver board, that's where the 170 VDC leaves. Check for a good connector, and check the solder joint on the header pin. The high voltage hits all of the displays at connector J1-1 and is daisy-chained from display to display. Check these connectors and the header pins too. On at least some early Stern games like Dracula, there is a fuse for the displays mounted on the back of the backbox door, often covered by a cardboard tag. It may be that these early games came without the fuse on the SDB. Check for proper amperage and continuity on this fuse holder if no voltage is reaching the displays.

Note - If there is any light at all on the display, then it is probably repairable. Some type of Bally display glasses will have some light on them, besides the digits. If there is light anywhere on the display, then the glass is most likely OK and your problems are elsewhere.

[[File:Dispglow.jpg|center]]
<center>See how this display is glowing when it's first turned on? This indicates that the glass is good.</center>.

<center>
REMEMBER - 170 VDC WILL HURT! 
TURN YOUR MACHINE OFF IF YOU'RE GOING TO MESS WITH IT BEYOND MEASURING VOLTAGES
</center> 

If you have 170 VDC at all of the displays, and the decoder is still working, but the displays are still blank, then there is probably a problem on the MPU or the MPU connectors, such as a "stuck-on" blanking signal, etc.

If the blanking signal for the displays is stuck high or low on the MPU then the displays will remain blank. To check the blanking signal use your DMM or logic probe on MPU J1 P10. During the flash tests it should remain high (5v on DMM). Once attract mode begins it should begin pulsing (DMM will show somewhere between 1v and 4v). If the blanking signal is stuck high or low examine the blanking circuit including CR6, U14, U20. It could be the PIAs but unlikely as the power on flash test should check that the PIAs changes states. I have seen CR6 be open and cause displays to be blank.

=====A single display is blank=====

If you have one display that is blank, it could be the same problems as mentioned above (lack of 170VDC), something wrong on the circuit board, or something with the glass display itself. If you see any light glowing at all on the display, then the glass is most likely good and your problem is elsewhere.

The main cause of a single display being blank is a bad glass. If the glass is good, then your problem is most likely a bad 4543 decoder IC. The decoder on the display driver board is used to decode the digit data from the MPU into signals that light the proper displays. If the decoder is blown, then this could cause the display to be blank. A quick check with a logic probe will help you decide if the decoder is function properly.

Sometimes the solder joints on the display glass needs are cracked and need to be reflowed. Depending on which solder joints are bad, this could cause the display to be blank.

If you can verify there is 170VDc, and the decoder is working, then it may be just a bad display. If there is some light anywhere, then it's probably good. If not, it may or may not be good. A totally blank display is the hardest thing to fix. If everything looks good, but the display is completely blank, then you may just have to chalk it up as a bad display glass. Unfortunately they can not be repaired.

=====All displays are missing the same digit=====

If all the displays have the same digit out, then the problem is most likely caused by a bad connector at the MPU. The MPU daisy-chains the digit enable signal to all the displays, and if the same digit is out on all, then it's either an amazing thing that they all have a problem w/ the same digit, or the digit enable signal is not present. Check the connectors on the MPU and all of the displays. If all seem well, then one-by-one, disconnect each display and see if the problem goes away. If it does, then there's a short or a bad connector problem on the board you just removed. Be sure to turn the power off between swap-outs, and wait 10 seconds for the high voltage filter capacitor to discharge before you remove any connectors.

=====The Same Number is Displayed Multiple Times During Display Test=====
If one or all of the displays show the same number more than once during display test, (ie. instead of 0,1,2,3,4,5,6,7,8,9 being displayed, 0,0,2,2,4,4,6,6,8,8 or similar is displayed), the 4543 decoder chip on one of the displays is probably bad. To test this, turn the power off, and disconnect all displays but one. Continuing performing this procede until the suspect display is found. DO NOT REMOVE THE CONNECTOR FROM THE DISPLAY WITH THE POWER ON. This will result in damage to the MPU board, the display, or both.

=====One display is missing the same segments on all the digits=====

Each display has it's own decoder chip, which takes four inputs from the MPU and outputs seven signals to light the seven segments of a digit. If you're having problems with one or more segments on all the digits, then it's either the segment driver transistor or the decoder itself. I'm sure there's a way to test the transistor but I just go ahead and install a new one. If that doesn't fix it, then replacing the decoder will. I've not had a segment problem that was not fixed by replacing both segment drivers and decoders (other than MPU problems). Be sure to orient the transistor and/or IC in the proper position. You'll notice a flat side on the transistor and a small notch on one end of the decoder IC. Be sure they line up just like the one you removed, and that the wires of the transistor go into the same holes that the old one came out of. Also, if you're replacing the IC, use a socket, so it'll be easier to replace it next time. Here's a handy chart that shows which segment driver transistor drives which segment, and another diagram of how the segments are labeled. Just find the segment that's giving you trouble on the chart, then look up it's corresponding driver transistor. Then find this transistor on the circuit board and replace it.

[[File:B-decoder-chart.jpg|center]]

=====One display has a segment locked on all digits=====

The segment driver has failed. When this issue is seen a lot of times the display will be blank except for the locked on segment. Replace the segment driver (see chart above) and then retest the display. If the display now works except for the segment drive you replaced is now turned off then replace the decoder chip. When the segment driver locks on it usually blows out that segment on the decoder chip.

=====One digit is out on one of the displays=====

If there is a single digit out, then it's probably the the level shifter and digit driver transistors for that digit. Just to be sure, check the connector on the display at pins J1-4 through J1-9. These are the connectors that supply the digit-enable signals from the MPU. The problem may be that the display driver is not getting the enable signal from the MPU. If it is, then just replace the two transistors and you should be back in business. Here's a handy chart that shows you which level shifter and digit driver are associated with each digit. The transistor labels should be printed on the circuit board, or look at the diagram below. Just look at this chart, find the digit that's blank, and then locate the two transistors listed for that digit. Find them on the circuit board and replace them.

{| class="wikitable sortable"
|-
!Digit
!Level Shifter (MPS-A42)
!Digit Driver (2N5401)
|-
|1's
|Q1
|Q7

|-
|10's
|Q2
|Q8

|-
|100's
|Q3
|Q9

|-
|1,000's
|Q4
|Q10

|-
|10,000's
|Q5
|Q11

|-
|100,000's
|Q6
|Q12

|-
|1,000,000's
|Q20
|Q21

|}

=====One display is missing a digit or segment=====
If one digit or segment is out on a display, but segment drivers, transistors, and the IC have all been replaced, be sure to check the resistors for damage and that they are giving the correct resistance.

If all else fails, try gently flexing or wiggling the glass a little bit to see if the segment or digit lights up. If that's the case, there may be an issue with one of the finger leads on the glass.

In the best case scenario, there is [[#Display(s) flicker|merely a cracked solder joint on a finger lead]] where it is soldered to the PCB.

Sometimes, the finger lead has been stressed and will snap on the top side of the PCB above the solder joint. A jumper wire might be able to address this.

In the worst case scenario, the finger lead has separated from the contact pad inside the glass. Unfortunately, there is not currently a recommended approach for performing a repair.

One suggestion included using a dremmel tool to drill out the glass to expose the finger contact, and then solder a jumper wire to it (note that solder might or might not stick to the contact, and instead, conductive glue or silver epoxy may need to be used, similar how a repair for a broken lead wire in a DMD display on newer games is performed).

On 6-digit glass, all the contacts are on the same side of the slot for the finger leads, and if the front side of the glass is drilled out, all the contacts accessible. On 7-digit glass, the contacts alternate which side of the slot inside the glass that they are adhered to, so only about half of these contacts are accessible from the front of the glass--some are adhered to that same front side that needs to be drilled out. So, it might not be possible to access all the contacts on a 7-digit glass.

[[file:bally-7-digit-glass-finger-contacts.jpg|left|thumb|300px|7-digit glass with alternating contact pads]] 

=====One digit is very bright, and the rest are out=====

If you have one digit that's very bright and all the rest are out, simply replace the digit driver and level shifter transistors for that digit. Turns out sometimes a short transistor will draw so much current that there's not enough left to drive the remaining digits, and so they all go blank. Just use the chart above to determine which transistors to replace.

=====Display(s) flicker=====
[[Image:CrackedHeadersAnnotated.jpg|300px|thumb|left|Closeup of Cracked Header Pins on a Bally/Stern Display Module. These cracks caused rapid "flicker" of the display.]]
[[Image:ColdSolderJoint.jpg|300px|thumb|right|Magnified view of a cold solder joint on a Bally/Stern Display Module.]] 
This is almost always caused by fractured solder joints at the header pins. If you have already re-flowed the solder, double check them, then look for other broken solder joints and check all connectors for tight fits. Something is loose that's making them flicker. This "flicker" is about the fastest flicker you can imagine.

Another cause of flickering or strobing digits is a faulty decoder IC. If your digits are flickering or "wavy", try replacing the decoder IC.

[[File:YT.png]] Here is a link to a [http://www.youtube.com/watch?v=KCsisnUJWoY video] of a display board with a faulty 4543 decoder IC. Keep in mind that failed / failing decoder chips do emit symptoms other than what is seen in the video. Please see the other symptoms discussed above in this section.

Yet another cause of flicker is low HV or a shorted display that drags down the HV.

'''Centaur Specific'''

Centaur, being a multiball game, requires that all 5 balls be in the trough. This means that switch 2, "5th Ball Trough", must be seen by the MPU as being closed. Unless the MPU sees switch 2 as closed, the displays will flicker.
 

=====Conclusion=====

That covers the most common display problems. If the pinball machine manual is not available, click on any of the thumbnails below for a large picture of the component layout of the all three boards. The 100K Ohm resistors are the ones colored brown-black-yellow.
 

===Sound problems===
Regardless of the sound board, it is always best to first remove the existing solder from the header pins, and reflow new solder onto them. Due to vibration over time, the header pin connections can end up with cracked solder joints, which is very common on the Bally sound boards. The next order of business would to replace the volume pot and the secondary pot, if one is used on the board. The original, factory pots used were not sealed, therefore, dirt and other contaminants can cause the pot to have dead spots or fail in general. Once these two things are done initially, troubleshooting the sound board, if it's still not working will be a lot easier. 

If the board is still not working after the above recommended procedures, the next thing would be to check all of the voltages used on the board. See the [http://pinwiki.com/wiki/index.php?title=Bally/Stern#Sound_Test_Point_Values Sound Test Point Value] section for the test point voltage values for each particular sound board. 

If all of the voltages check out, it's time to move onto the appropriate sound board troubleshooting section below.
 
==== AS-2518-32 & AS-2518-50 Sound Board Troubleshooting====
[[File:Bally -32 Cracked Headers.JPG|300px|thumb|left|Typical cracked solder joints on the header pins of a -32 board]]
[[File:BallySoundFracturedHeaders.jpg|300px|thumb|right|Close-up of severely cracked solder joints on the header pins of a -32 board]] 
The first course of action, before performing any troubleshooting to the board, is to inspect the header pin connections on the reverse side of the board. It is common to have cracked joints, where the header pins are soldered to the board. If cracked solder joints are apparent, heat and remove the old solder, and reflow new solder onto the connections. This will ensure that incoming voltages, ground and sound signals are solid on the board itself. Inspection of the connectors located in the female housing, which connects to the header pins, is equally a good idea. Replace any connectors that appear to be marginal. Molex Trifurcon crimp connectors are recommended as replacements.
 

[[File:Bally -32 Sound Min Components.JPG|300px|thumb|left|Minimal component replacement for -32 and -50 boards]] 
There are several components which should be replaced on these boards to speed the troubleshooting process. Both the -32 and -50 sound boards use at least two 10Kohm pots. One pot controls overall volume. The other pot controls sound sustain (or tone duration). Both pots should be replaced to eliminate them as possible culprits and improve reliability. Likewise, a 1N4004 diode (CR3) is used on the board at the incoming +43vdc. Should this diode fail, it can cause the CPU to halt at 6 flashes at boot up. 

Capacitor kits for both the [http://www.greatplainselectronics.com/proddetail.asp?prod=BALLY-S32E-KIT -32] and [http://www.greatplainselectronics.com/proddetail.asp?prod=BALLY-S50E-KIT -50] boards are available from GPE. Although it is not always necessary to replace the caps on these boards, it is recommended. 

Should the 86L93 (U11) chip fail, the [http://www.greatplainselectronics.com/search.asp?pg=1&stext=74LS93&sprice=&stype=&scat= 74LS93] is a viable substitute.

There is a great [http://www.pinball4you.ch/okaegi/rep_soundold.html repair website with step-by-step checkpoints, created by Oliver Okaegi]. You do need to have scope to see the signals. 

'''Voltage Test Points''' 
The following DC voltages are required and may be measured on the sound board:

*TP1 = 5v,
*TP3 = 12v,
*TP4 = 43v.

If any voltages are missing, check the connectors. Specifically check the integrity of the header pins.

'''12v regulator section:''' 
Check for 67 volts on the positive side of C17. If missing replace CR3. If positive side of C17 is the same as TP4(43v) replace C17 and CR3.

If 12v is too high, check Q1, R22, CR4, and C18.

'''Clock Generator:''' 
U1(4049) can fail. Check for about 2.5vdc where R3 and R5 meet. (On my functioning -50 board, I see .8vdc at this point) If voltage incorrect replace U1 which is a 4049 hex inverter. If still incorrect suspect U4 which is a 4526B programmable 4 bit counter. The 4526 can be purchased from vendors such as [http://www.mouser.com/ProductDetail/ON-Semiconductor/MC14526BCPG/?qs=sGAEpiMZZMtsbn1GaJyslzVwwLLwbjUEVTxCaemDWNo%3d Mouser] or [http://www.digikey.com/product-detail/en/MC14526BCPG/MC14526BCPGOS-ND/1478908?WT.z_cid=ref_octopart_dkc_buynow&cur=USD Digi-Key].

'''Amplification / no sound issues:''' 
First, make certain that the cabinet speaker is present, connected, and functioning. If an audible hum is heard from the speaker, then the amp is working. Next, check both pots. It is best to replace them if they are the originals (typically blue or black thumb wheel pots). Measuring across the two outer legs of the pot is the total resistance (10k). Measuring from the middle leg gives a resistance with regards to how the pot is adjusted (a value from 0 ohms to 10 kohms depending on the pot's position).

To check the amplifier at U9 (LM741), look for about 2vdc at U9 pin 2. (On my functioning -50 board, I see 6vdc at U9 pin 2. Before replacement, 12vdc was seen when it wasn't functioning.) If voltage is missing, replace the amp. Note that the LM741 must be a specific part; part number LM741CN. Other LM741 parts may work, but often the volume is not amplified, resulting in only low volume output. A modification to the -32 sound board can be made to overcome this issue. The modification adds three components to the -32 sound board that Bally added to the -50 sound board during production. A discussion of this mod can be found [https://pinside.com/pinball/forum/topic/volume-problem-after-replacing-u9-on-bally-32-sound-board here].

 

==== AS-2518-51 Sound Board Troubleshooting====
Note: The following games do not make sound when the diagnostic button is pressed on the board:
*Nitro Groundshaker
*Future Spa
*Space Invaders
*Xenon
*Speakeasy

Sound Board References: 
[[image:YT.png]] [https://www.youtube.com/shorts/lhaC5cxpoDY Future Spa] 
[[image:YT.png]] [https://www.youtube.com/shorts/iiU78w-oZ3w Mystic] 
[[image:YT.png]] [https://www.youtube.com/shorts/B4YmV-gqujw Skateball] 

[[File:As-2518-51.jpg| 300px| left |thumb | Bally AS-2518-51 Sound Board]]
[[File:Bally-51SoundBoard.jpg| 300px| right|thumb | Bally AS-2518-51 Sound Board Schematics]]
Although the AS-2518-51 sound board uses a 6800 family of microprocessor, the lack of an on-board, boot status LED makes this board more difficult to troubleshoot than the Squawk and Talk sound board. On the plus side, this sound board utilizes some of the same ICs, which are commonly found on the game's MPU board. Fortunately, all of the larger ICs on this board are socketed. Like the OEM sockets on the MPU board, the sockets used on this board are subject to failure. Replacement with new, high quality sockets is advised to eliminate this possible cause of failure and for long term reliability. 

The first course of action, before performing any troubleshooting to the board, is to inspect the header pin connections on the reverse side of the board. It is common to have cracked solder joints, where the header pins are soldered to the board. If cracked solder joints are apparent, heat and remove the old solder, and reflow new solder onto the connections. This will ensure that incoming voltages, ground and sound select signals are solid on the board itself. Inspection of the connectors located in the female housing, which connects to the header pins, is equally a good idea. Replace any connectors that appear to be marginal. Molex Trifurcon crimp connectors are recommended as replacements.
 

Like all sound boards of this age, the capacitors are likely to have dried out and are no longer doing their job. Capacitor kits for this board can be acquired at [http://www.greatplainselectronics.com/proddetail.asp?prod=BALLY-S51E-KIT Great Plains Electronics]. Installing a cap kit brings most dead boards back to life. 

If the board is producing no sound at all, start by checking the volume adjustment pot. When turning the pot, the volume of the hum should get quieter and louder. If this is not heard, the amp/pot may be bad. If the hum volume changes, it is likely that the amp and pot are working. However, the 1K volume adjustment pot is 30+ years old, and was an "open" design. It is recommended that this pot be replaced with a quality sealed 1K ohm pot, whether or not the original pot tests good. 

Check the power at the board with a DMM. TP3 is ground. TP2 and TP1 should measure 5VDC and 12VDC respectively. These are nominal values. Minor variation from these values is acceptable. 

Next, it is time to check the large ICs on the board itself. First, swap the 6821 PIA at U2 on the sound board with either U10 or U11 on the MPU, and retest. Second, swap the 6810 RAM at U10 on the sound board with the 6810 at U7 on the MPU and retest. 

If the problem persists, swap in a known good sound ROM at U4 and retest. Pay particular attention to the legs of U4, if it is a factory masked ROM. It is common for the legs of these masked ROMs to oxidize or tarnish, just like the masked ROMs used on the MPU board. Hence, the legs can be fragile, and are easily broken. Likewise, tarnished legs on U4 could potentially be responsible for the lack of sound. Evidence of oxidation is visible in the form of blackened chip legs (silver oxide). The oxidation can be removed in several ways. The most common methods are gently using a pencil eraser over the legs, or soaking the chip legs in Tarn-X, followed by rinsing the legs in clean water, and allowing to dry before re-installation. As mentioned previously, if the legs are oxidized, use extreme caution when removing the chip from its socket and removing the oxidation. 

If a known good 6808 (a 6802 can be used when jumper A is installed, and jumper B removed) is available, swap it for the processor at U3 and retest. 

If a known good AY-3-8910 is available, swap it for the sound IC at U1 and retest. The AY-3-8910 produces '''ALL''' of the sound from this board. If sounds continue to play after the completion of a game, this can be caused by a failed AY-3-8910. 

The sound interrupt signal and the sound select signal IC should also be checked. Connect a logic probe to the board; red lead at TP2 (+5VDC), black lead at TP3 (GND). With J1 connected to the game, place the probe on pin 40 of the PIA at U2. The signal should start high. When the game's MPU completes it's 7th flash, it will command the sound board to make the boot sound. At this point, pin 40 will go low for a split second, then return to high. If all goes well, consider the sound interrupt signal good. 

Test the function of the sound select inverter 4049 at U5. U5 is a simple hex inverter. In attract mode, with no sounds being produced, pin 3 should be low, pin 2 should be high. Pins 5/4, 7/6, and 14/15 should test the same as pins 3/2 respectively. Pins 9 and 11 may not be connected on the game. If so, there will be no signal on those pins. However, their "inverted" signals at pins 10 and 12 should be high. Pins 13 and 16 are not connected. 

The 6808 / 6802, AY-3-8910, and 6821 ICs require a reset signal which is created via a 1N4004, 1Mohm resistor, and NAND gates at U6 (4011). Test the 1N4004 diode via normal diode test. U6 can be tested with a logic probe similarly to U5. With a logic probe on pin 40 of the 6808 processor, at power on the signal will remain low for a split second and then go high. 

The external clock signal can be probed at pin 37 of the 6808. It should pulse steadily. If not, suspect the crystal oscillator.

Although U7 is specified as a 555 timer IC on the schematics, it is not listed on the BOM, and was not installed on this board. Nor were any of the several discrete components to the right of the U7 solder pads (i.e. C10, C11, R11, R12).

Loud Hum 
While it might seem OK to connect analog and digital ground for testing on the bench, this causes the board to produce a loud hum. Pin 15 (analog ground) must be grounded separately from pins 6 and 14 (digital ground).
 

====Sounds Plus Sound Board Troubleshooting====
This is a stub.
 
====Vocalizer Speech Board Troubleshooting====
There is a [https://pinside.com/pinball/forum/topic/xenon-vocalizer-eprom-repair-vids-guide repair guide on pinside] for addressing ROM issues and replacing the original ROMs with EPROMS.
 

====Squawk & Talk Sound Board Troubleshooting====
===== Sound Test Reference =====

The following video links demonstrate properly operating Squawk & Talk sound boards.

[[image:YT.png]] Place Holder.

=====Basic Information=====
[[File:SquawkAndTalkJumperAndTestPointLocations.jpg|300px|left|thumb|Bally Squawk & Talk Jumper Locations. Note that the -61B revision of the board contains a jumper FF located within the stack of resistors below the AD558. Neither the -61 or the -61a revision has this jumper.]] 

The image at left indicates jumper and test point locations.
Jumper settings for various game and ROM combinations can be found [[Bally/Stern#Squawk_.26_Talk_Jumper_Settings | here]].
 

Test Point Number and Functions

{| class="wikitable"
!   TP   
! Function 
|-
| <center>1</center> ||  Ground 
|-
| <center>2</center> ||  +5VDC 
|-
| <center>3</center> ||  +11.5VDC 
|-
| <center>4</center> ||  -5VDC 
|-
| <center>5</center> ||  Speech Volume Control Voltage 
|-
| <center>6</center> ||  Sound Volume Control Voltage 
|-
| <center>7</center> ||  AY-3-8912 Output 
|-
| <center>8</center> ||  E (external clock provided by the 6808/6802) 
|-
| <center>9</center> ||  TMS5200 Output 
|-
| <center>10</center> ||  VMA (valid memory address) 
|-
| <center>11</center> ||  TMS5200 clock (not used. Would clock the TMS6100) 
|-
| <center>12</center> ||  Reset 
|}
Source: Bally AS-2518-61 Squawk and Talk Schematics.
 

Integrated Circuits used by the Squawk & Talk sound board.

*U1 - Motorola 6802 or 6808 8-bit microprocessor
*U2 - ROM
*U3 - ROM
*U4 - ROM
*U5 - ROM
*U6 - 6810 RAM (only used if a 6808 microprocessor is used. If a 6802 is used, the socket is empty)
*U7 - 6821 PIA for controlling the speech IC - TMS5200 VSP and TMS6100 VSM phrase ROM
*U8 - TMS 5200 VSP Speech IC (does not occupy address space)
*U9 - TMS6100 VSM 16k byte Phrase ROM containing speech data (never populated). Again, it does not occupy address space
*U10- AD558 DAC for converting digital wave data stored in the ROMs to audio
*U11- 6821 PIA for controlling the AY-3-8912 sound IC and the test LED
*U12- General Instruments AY-3-8912 PSG (Programmable Sound Generator) IC, which again, does not occupy address space

=====The Very Easy Simple Fix aka the General Illumination is Out=====
If for some reason, the general illumination is not lit on the playfield or backbox of the game, suspect a blown 20A fast blow F5 fuse on the power module or possibly fuse clips in poor condition. One leg of the general illumination is fed to the Squawk & Talk, and it becomes the -5VDC, which is one of the voltages needed to power the TMS5200 speech chip. Without the general illumination, the Squawk & Talk board will not successfully boot!
 

=====General Troubleshooting=====
Troubleshooting the Bally Squawk & Talk board is much simpler than it might first seem. First, the board provides "blink codes" at power up, similar to the way that Bally MPUs do. These codes help isolate the failed component.

[[File:TMS5200LegTarnish.jpg|300px|right|thumb|The legs of the TMS5200 Speech Processor chip almost always tarnish over time, perhaps due to the legs and the socket being constructed from dissimilar metals. Replacing the socket and removing the tarnish is always advisable. Be cautious as the legs sometimes become fragile.]]
The Squawk & Talk sound board is itself a single board computer. At it's heart is the 6808 processor with external RAM, or the 6802 processor with integrated RAM. Two 6821 PIAs are used to interface the processor to peripheral devices. The 6821 at U11 provides an interface to the AY-3-8912 (if used) or the U16, a 4049 inverter where sound selects are sent from the MPU. The 6821 at U7 provides the interface to the TMS5200 Speech Processor.

Up to 4 ROMs can populate the board with either 2716, 2532, or 2732 ROMs.

An AD558 DAC (digital to analog converter) is used to make traditional pinball beeps, squeeks, and tones.

A TMS5200 Speech Processor is used to convert digitally stored (and compressed) sound information in the ROMs to analog "speech" (which can also be sounds).

An AY-3-8912 Sound Generator is sometimes populated at U12 to produce simple tone sounds.

Two LM3900 operational amplifiers (op amps) amplify the analog signals from both the speech and the sound lanes before they are summed and provided to the main amplifier.

At TDA2002 amplifier is used at the final stage of amplification. A TDA2003 may be used to replace this amp.

Variable 1KOhm pots at R69 and R70 control speech and sound volumes independently (respectively).

Provisions are available for controlling volume via external pots by connecting to J2, pins 5 and 6.
 

[[File:SandTRegulator.jpg|300px|left|thumb|The 5V regulator sometimes develops cold solder joints. Without 5VDC, the diagnostic LED won't blink at all.]]
 Techniques 
Power the board on the bench. 
Recognize blink codes. 
Check voltage regulation circuits. 
Use the "self-test" button. 
Isolate the problem to the "digital" section or the "analog" section. 
Use a logic probe to "listen" at points in the analog section.
 

[[File:PoweringSquawkAndTalkOnTheBenchAnnotated.jpg|300px|thumb|left|Powering the Bally Squawk & Talk Sound Board on the Bench.]] 
Powering the board on the bench 
To power the board on the bench, use an old computer power supply that is capable of providing -5VDC and +12VDC.
*Connect +12VDC to J1 pin 10. The board will use the +12VDC and will also regulate it down to +5VDC
*Connect -5VDC to TP4
*Connect the power supply ground to TP1
Double check all of your connections before applying power. 

If the board is a -61b revision, as used in Centaur for instance, install a temporary jumper at location "FF". This allows operation without attaching the "Say it again" board.
 

Blink Codes 
An overview of "Blink Codes" follows. 
For a more in depth discussion of these blink codes, see the excellent information developed by Clive Jones, [http://webpages.charter.net/coinopcauldron/squalkart.html here]. 

{| class="wikitable"
!   Blink   
! Meaning 
|-
|  First "flicker"  ||  The processor has found the program code in ROM, and has begun to configure the board. 
|-
|  First Blink  ||  The 128 bytes of system RAM (either within the 6802, or external in the 6810 if configured with a 6808) have tested good. 
|-
|  Second Blink  ||  The 6821 PIA at U7 (which controls speech) has passed test. 
|-
|  Third Blink  ||  The 6821 PIA at U11 (which interfaces with the AY-3-8912 and fields sound codes from the MPU) has passed test. 
|-
|  Fourth Blink  ||  Communication with the AY-3-8912 has passed. Note that the PIA at U11 must be communicating correctly with the AY-3-8912 for this test to pass. If there is no fourth blink, first swap a known good 6821 into U11. 
|-
|  Fifth Blink  ||  The TMS5200 Speech Chip has passed testing. 
|}

Pressing the red diagnostic button on the Squawk and Talk board, should cause the board to play various speech calls (games like Medusa seem to go on forever, Spectrum plays only a short speech call) followed by a sound call. The speech is generated by the TMS5200. The lone sound call at the end of this test is generated by either the AY-3-8912 (as in EBD, for instance) or the AD558 digital-to-analog converter. At the conclusion of playing these various speech calls and sound call, the board then reboots itself, and the same blink codes should be seen.

Basic maintenance actions 
There are 5 actions you can take to ease the process of debugging the S&T board (priority order):
#Ensure the correct jumpers are installed, matching the game and sound ROM type
#Replace ALL electrolytic capacitors on the board
#Replace both 1KOhm pots (one for speech, one for sound)
#Replace IC sockets (empty sockets don't need to be replaced obviously, ScanBe sockets must go, RU sockets can remain)
#Replace .156 male headers at J1 and J2 (at a minimum, reflow the solder joints)

Completing each of the above items usually results in a working Squawk & Talk board.

Capacitor list and recommended modern replacements 
C1 - Axial Electrolytic 47uF, 25 Volt 
C14 - Axial Electrolytic 4700uF, 25 Volt 
C15 - Axial Electrolytic 10uF, 50 Volt 
C19, C24, C25, C28, C31, C34 and C42 (7 capacitors) - Axial Electrolytic 1uF, 50 Volt 
C27 - Axial Electrolytic 1000uF, 25 Volt 
C29 - Axial Electrolytic 470uF, 16 Volt 
C36 and C43 (2 capacitors) - Axial Electrolytic 2.2uF, 50 Volt 
C37 and C38 (2 capacitors) - Axial Electrolytic 330uF, 50 Volt 
 

=====Locked on LED on Squawk & Talk Sound Board (Minimizing Chips Needed to Boot)=====
As mentioned above, there are LED blink codes used when passing specific chip tests during the boot up process. However, the Squawk & Talk sound board is similar to the Bally -17 / -35 MPUs, and it too can end up with the dreaded locked on LED. The end result is the board not proceeding through the boot process. On the plus side, battery damage is far less of an issue for the S&T board versus the MPU board. 

For starters, it would be best to reduce the amount of chips installed on the S&T board to try to get it to boot. At a minimum, only the following. factory socketed chips are needed to achieve some "signs of life" out of the board. Only having these chips installed will not allow the board to complete its boot up process. However, chips can be installed in a systematic method to get the board to successfully boot. 

'''Flicker''' 
To achieve a flicker from the diagnostic LED on the board, the U1 CPU (either a 6808 or 6802), the U11 PIA (this 6820 or 6821 activates the LED), and the U5 ROM (boot up instructions are located on U5). Make certain that the [[Bally/Stern#Squawk_.26_Talk_Jumper_Settings | jumper settings]] are correct for U1 and U5. Keep in mind that a known working 6820 / 6821 can be acquired from a working Bally MPU board. Likewise, the 6820 / 6821 from the S&T board can be installed in a known working MPU board to test. 

If the board still has a locked on LED, the following things should be investigated: 
*Make sure that the reset on the CPU chip starts low briefly and then goes high. With a logic probe, check pin 40 of U1. If the reset does not go high, suspect C1 (47uF 25v), CR1 (1N4148), R1 (27K 1/4w), U15 (74LS14), or possibly U17 (74LS155).
*Next, check for an active clock signal. With a logic probe, check pins 38 and 39 of U1. Both legs of the CPU should be pulsing (some logic probes may not pulse, the clock voltage is rather low). These legs go directly to the clock crystal (Y1 - 3.58 mHz). If these signals are not pulsing, suspect the crystal or its associated capacitors, C3 and C4 (both are 27pF caps). It is fairly common for the crystals to fail on these boards.
*Make sure that the transistor (Q1 - 2N3904 or 2N4401) which drives the LED is functioning.
*Again, check that the correct jumpers are installed. If the incorrect jumpers are installed for U1 / U6 (K or L) or U5 (Y, Z, AA, BB), the LED will remain solidly lit.
*Inspect the chip sockets. Although the chip sockets used on the S&T are of decent quality, they have aged and can fail. If a chip can be removed from its socket by merely pulling it out with one's fingers, the socket is bad and needs replaced.
*Lastly, make certain that U1, U5, and U11 are good. 

'''1st Flash''' 
Once a flicker is achieved, the road to recovery is much smoother. Install the U6 RAM (6810), if using a 6808 CPU at U1. A good 6810 can be pulled from a working MPU board. Likewise, the 6810 on the S&T board can be tested in a known working MPU board. If using a 6802, the 6810 is not needed. Also, the 1st flash will be automatic with just the 6802 installed, as long as jumper K is installed. Having U6 installed with a 6802 CPU chip installed does not hurt anything, and either the L or K jumper can be installed, as long as the 6810 is good. 

'''2nd Flash''' 
Install the U7 PIA (6820 / 6821). Again, a good PIA can be acquired from a known working MPU board. 

'''3rd Flash''' 
Since the U11 PIA (6820 / 6821) is already installed, the 3rd flash should appear, if this chip is good. 

'''4th Flash''' 
Install the U12 sound generator chip (AY-3-8912), if it is used. If the U12 chip is not used, the 5 EE jumpers must be installed.

'''5th Flash''' 
Install the U8 speech generator chip (TMS5200). It is very common for the speech chips to have tarnished legs. To remove the tarnish, a pencil eraser can be used, if used very gently and cautiously. Tarn-X is a much better product to remove the tarnish. 

'''Closing Notes''' 
Once the board boots, a single sound is typically heard. A single sound is typically heard when the test button is pressed too. At this point, the remaining sound ROM(s) can be installed. Again, make certain the ROMs have the appropriate jumpers installed. If the incorrect jumpers are installed, the LED will remain solidly lit. 

The U10 DAC (AD558) does not need to be installed at any point during the above process to get the board to successfully boot. However, U10 must be installed to generate all of the sounds associated with any particular game.
 

=====Speech is Heard but No Sounds=====
If the board is booting, but only speech can be heard, and the above "Basic maintenance actions" were not performed, there are several things which can make this occur. The first would be to make certain the sound potentiometer is functioning. Dead spots and / or a completely failed pot can cause the sounds not to be heard. Secondly, replace the electrolytic capacitors. This should be done in most cases anyhow. If after replacing the capacitors did not cause the board to produce sounds, there are a couple of other things to look at. 

A starting point would be to make certain that the wiring harness is intact between the MPU and S&T boards. To test this, place an alligator clip on each of the resistors located on the bottom left of the board. The sound signals come into these resistors first. Next, take the alligator test lead, and attach it to one side of a DMM. Put the DMM in contintuity mode. Place the other lead of the DMM on the resistor leg of R97-R100 and R106 located on the MPU board. Repeat the steps for each sound signal. Performing a continuity test in this manner (from board to board) narrows down bad connectors and / or header pins.

If the harness is all right, make certain the U16 (4049) inverter on the S&T has not failed. 
 

=====Pitch of Speech is too high/low=====
[[File:SAndTR9.jpg|300px|left|thumb|R9, shown in-situ, on the Bally Squawk and Talk board. Note that this 120K resistor is not the OEM resistor and has been substituted.]]
The "pitch" of Squawk and Talk speech can be adjusted by varying the value of resistor R9, pictured in-situ at left. Typically, in almost every instance, the factory value of the resistor is 130K 1/4W. However, Flash Gordon uses a 240K resistor.

[[File:YT.png]] If changing out the typical 130K resistor, using a higher resistance (140K) resistor will lower the pitch; a lower resistance resistor (100K) will increase the pitch. Example videos of both higher and lower pitch speech using these resistor values can be found here ([https://www.youtube.com/watch?v=BFeL47DoSJQ high], [https://www.youtube.com/watch?v=nef-wOmuduk low])
 

=====Speech is Garbled, Clipped, or Unintelligible=====
The TMS5200 is practically unobtainable as of July, 2020. At times, a TMS5220 will be substituted to replace a failed TMS5200. The TMS5220 will create voice, but the audio will be garbled and somewhat unintelligible.

[[File:YT.png]] A video comparing "Flash Gordon" voice/sound diagnostics with a TMS5200 and a TMS5220 can be found [https://www.youtube.com/watch?v=Mml7fH6QYFw here].
 

=====Hum In Voice Circuit=====
If the "hum" present during voice calls is noticeably louder than the "hum" present during sound calls, this can be caused by excessive AC "noise" in the -5VDC generation circuit.

Isolating the hum to the voice or sound circuit is as simple as adjusting the trim pots clockwise to reduce the volume of that channel. The hum can be caused by failed C37 or C38 (both 330uf/50V axial caps). However, if the board has been recapped, which is always advisable for this board, and the hum is still present, suspect the 7905 negative 5VDC regulator.
 

====Say It Again Reverb Board Troubleshooting====

=====Say It Again Reverb Board Basic Information=====

{| class="wikitable"
|+Test Point Number and Functions
!TP
!Function
|-
| 1 || Ground
|-
| 2 || Test Oscillator
|-
| 3 || Test Oscillator Output
|-
| 4 || Sound Input
|-
| 5 || Regen Adjustment
|-
| 6 || Audio Post U1 Op Amps
|-
| 7 || Clock
|-
| 8 || Clock
|-
| 9 || Clock
|-
| 10 ||
|-
| 11 || On/Off Switch
|-
| 12 || +12V DC
|-
| 13 || Audio Post U3 Op Amps

|}
''Source: Bally Say It Again Schematics.''

'''Integrated Circuits used by the Say It Again sound board.'''

*U1 - LM3900 Quadruple Operational Amplifier
*U2 - SAD4096 n-channel Bucket-brigade audio delay line
*U3 - LM3900 Quadruple Operational Amplifier
*U4 - CD4066 Quad Bilateral Switch
*U5 - CD4046 Phase-Locked Loop
*U6 - CD4001 4-Channel NOR Gates
*U7 - CD4001 4-Channel NOR Gates
*U8 - LM7812 12V Voltage Regulator

'''Powering the board on the bench'''

The Bally Say It Again board requires only the solenoid voltage of +43V DC to operate.

If tracing the audio signal, a sine wave signal generator or another audio source, plus a scope is required.

=====The Very Easy Simple Fix aka the Solenoid Voltage is Out=====
If for some reason, the solenoid voltage is out, suspect a blown 5A F4 fuse on the power module or possibly fuse clips in poor condition. The Say It Again board runs on +12V DC voltage that is derived from the +43V DC solenoid voltage. Without this voltage, the reverb effect cannot take place although the board should pass the unaltered sound back to the Squawk and Talk board.

Note that the MPU will not boot without the +43V DC solenoid voltage.

=====Say It Again Sound Board General Troubleshooting=====

'''Basic maintenance actions'''

The "Regen" 50K and "Bias" 10K controls should be replaced. The 50K can be replaced with part 3386P-1-503TLF, while the 10K part is 3386P-1-103TLF.

The Say It Again board does not use the 1uF caps used in the Squawk and Talk board, but there are three capacitors in the 12V DC power supply that should be replaced. All are axial:

* C16 100uF 160V
* C18 100uF 100V
* C20 10uF 25V

C20 is a tantalum capacitor that can be replaced with a Kemet T322D106K035AT. However an electrolytic 106TTA035M could be substituted. Both are 35V.

=====Say It Again Sound Board - No Sound=====
If there is no sound at all coming from the cabinet speakers, troubleshooting must include both the Say It Again board and the Squawk and Talk Board as they work together.

*Make certain that the volume control on the coin door is turned up mid-way or higher. Move this volume control back and forth and check for noise from the speaker. If there is noise, then the cabinet speaker is connected and working. If no noise, check speaker and speaker wiring.
*Check to insure jumper FF is cut on the Squawk and Talk board. If it is cut, you can temporarily jumper FF and press the test button to insure that the Squawk and Talk board is working. If it does not work, see the Squawk and Talk section troubleshooting.
*With jumper FF removed, check the connections at plug J2 on the Say It Again board and J2 on the Squawk and Talk board. The audio leaves the Squawk and Talk board and enters the Say It Again board, then returns. If these connections are not correct, then there will be no sound.
*If the audio connections to and from the two boards are good, and the Squawk and Talk board is working, there should be sound even if the Say It Again Board is not working, although, perhaps at a lower volume. The audio should bypass the circuit through C1 and around U3 via R31, R32, C32 and C12.

[[File:J2 Bally S&T PCB IMG 8349.jpeg|300px|thumb|left|J2-9 is audio out. J2-7 is audio in. J2-8, 10 are grounds for the shields.]]
[[File:J2 Bally SIA PCB IMG 8350.jpeg|250px|thumb|right|J2-6 is audio in. J2-2 is audio out. J2-1, 5 are shield grounds. Only one shield is usually grounded to this board.]] 

=====Say It Again Sound Board - Sound But No Reverb=====

'''Adjust the Pots'''

Try adjusting the two pots, "Regen" and "Bias". If the reverb is restored, consider replacing the pots. Adjust the "Bias" pot following the procedure outlined in the Bally Centaur manual 'Set Up Procedure For 'Say It Again' (AS-2518-81) Module'.

'''Check the Power Supply'''

The Say It Again board has its own +12 regulated power supply. Test TP12 vs. TP1 to confirm that 12V DC is present. If missing, connect to the (+) side of C18 and check for 24V DC. If present, U8 or C20 are suspect.

If no voltage at C18, check the (+) side of C16 for ~60 - 70V DC. If present, suspect C20, U8 or VR1.

Lift one leg of C20 and see if the voltage returns. C20 is a tantalum capacitor that can fail as a short. If voltage is not restored, remove U8 and check the voltage at C18. If voltage at C18 is good, then replace U8. While this circuit can work with C20 missing, it is a good idea to replace it.

If voltage is not returned at C18, suspect VR1 but also inspect R41 for damage.

If the voltage is missing at C16, check C16, CR1 and the connections at J1-1,5.

'''Check the On/Off Circuit'''

U4 controls the reverb on/off function. Grounding at J1-3 turns off the reverb, but that option is not used in Centaur.

Check TP11 for approximately 11V DC. If present, the reverb switch should be on unless that section of U4 is defective.

To check the function of U4, hook up a scope to TP13 and TP1 and press the test switch on the Bally Squawk and Talk board. If signal is present at TP13, but not at U4-2 and TP11 is about 11V DC, then suspect U4.

It maybe possible to take U4 out of the circuit by jumping U4-1 to U4-2 since this on/off function is not utilized anyway.

If U4-13 is not about 11V DC, then check U4-12, which should be about zero and the base of Q3 which should be about 0.7V DC. Also check C30 which is a tantalum capacitor in this circuit. U4-5 should read about 11V DC, while U4-4/6 should read about zero.

'''Sound But Still No Reverb'''

If the power supply, the on/off circuit and the adjustment pots all work and there is still no reverb and no audio at TP13, the fault may lie with U1 or U3 that are LM3900 op amps, or the U2 reverb IC.

To test this circuit, press the test button on the Bally Squawk and Talk board and use a scope to confirm audio at TP4, then at TP6. If present, then U1 is OK.

Connect the scope at the junction of R19/R18 or the base of Q2 to confirm output from U2. If OK, but still no signal at TP13, then suspect U3, or Q1/Q2.

If the reverb IC U2 is not operating, check the presence of the clock at TP7 and TP8. If present, suspect U2. If missing, check TP9. If present, suspect U6 or U7. If no clock at TP9, suspect U5 and C14.

===== Say It Again Sound Board - Bias and Reverb Adjustments=====

[[File:J2 Bally SIA PCB IMG 8350.jpeg|150px|right|thumb|The REGEN and BIAS controls.]]
* Turn the main speaker volume control on the coin door all the way off.
* Turn REGEN R29 all the way off (counterclockwise).
* Connect a jumper from TP1 to TP2.
* Connect a jumper from TP3 to TP4.
* Connect a voltmeter to TP5 and TP1 and set to AC.
* Adjust the BIAS control R15 to obtain the maximum reading. The value should be about 0.5 to 0.6 AC.
* Disconnect jumpers.
* Turn the main speaker control on the coin door up to a normal level.
* Press the test button on the Bally Squawk and Talk board.
* Adjust REGEN R29 to the desired echo repeats.

Source: Bally 1983 Centaur II Manual.

====Cheap Squeak Sound Board Troubleshooting====

The schematic for this board can be found here: [[media:BallyCheapSqueakSchematics.pdf|Bally Cheap Squeak Schematics]]

[[File:Bally Cheap Squeak.JPG|300px|right|thumb|Bally Cheap Squeak Sound Board A080-91603-XXXX or Midway P/N M-051-00114-XXXX]]

At power up, the Cheap Squeak's LED will flicker briefly, then flash, flash again, then turn on and stay on. Once the LED stays on, it seems to turn itself off for certain sounds, and then turn back on. Likewise, it appears to idle with the LED on, when no sounds are playing.

The Cheap Squeak uses a single 1Kohm volume pot. If repairing this board, replace the pot with a high quality sealed 1K pot.

'''Test Points'''
*TP1 should measure about 11VDC.
*TP2 is 5VDC.
*TP3 is ground.
*TP4 is the clock signal, provided externally by the 6803 for the purpose of synchronizing address and data read cycles.
*TP5 is the reset signal, which is also present on pin 6 of the 6803. 

'''Bench Testing'''
# To power the board on the bench, provide 12VDC to J1, pin 10.
# Provide ground from the power supply to J1 pins 14 and 15.
# Connect a small speaker to the speaker output pins at J2 (2 pins).
# The board generates it's own 5VDC via a 7805 voltage regulator at U9. Therefore, an external 5VDC source does not need to be connected.

'''Special Note'''
The +5v can be connected directly to TP2, or +12V can be connected to TP1 to power the board. However, both do not need to be connected. If powering the board in this manner, the power amp will not be powered. +12v needs to be connected to the bottom of the L1 inductor, and ground connected either to the left leg of the L3 inductor or the left leg of the large capacitor at the bottom of the board (C24).

When powered on, the reset circuitry on the board holds pin 6 of the 6803 (~RESET) low for a split second, then allows it to go high.

Pressing SW1 should cause the board to generate a test sound, then the board reboots itself. Note that different sound ROMs may act differently. Generating a tone and rebooting is characteristic of the "X's and O's" sound ROM.

The test sound can be heard using an inexpensive logic probe like the [http://www.amazon.com/dp/B000Z9HAP4/ Elenco LP-560] at some points in the analog sound path. Attach the logic probe to +5VDC (TP2) and Ground (TP3) on the board. Probe pin 4 of the ZN429 DAC then press SW1. Some sort of tone should sound briefly, then the board will reboot. The tone can also be heard at pins 1 and 4 of the TDA2002 amp. Unfortunately, between the amp and R25, a logic probe isn't adequate for cheaply hearing the tone. However, if there is a tone at pin 4 of the ZN429, but no tone at pin 1 of the amp, then there is a good chance that the LM3900 has failed.

[[File:CheapSqueakBlownTantalum.jpg|300px|left|thumb|An example of a blown tantalum capacitor on a Cheap Squeak board (blue caps, top blown)]]

The Cheap Squeak board likes to blow the tantalum caps as shown in the picture on the left. While it's unclear why they tend to blow, simply replacing the blown cap usually returns the board to proper function. A gentle reminder, tantalum caps ARE polarized and must be installed in the correct direction, or they will burst into flames and/or explode, which could lead to injury. The marking for C22 isn't clear on the Cheap Squeak board. Use a multimeter to determine which through-hole is ground, and install accordingly. Most tantalum caps are marked on the +/positive side lead. 

This [http://www.pinball4you.ch/okaegi/pro_cheap.html link] contains some additional info regarding the Cheap Squeak sound board.
 

=====Cheap Squeak Schematic Errors=====
Note that the Cheap Squeak schematics for Black Pyramid have some incorrect info regarding the connections for U3 pin 2 to ground and U3 pin 20 to U4 pin 10.

[[File:BLY_Cheap_Squeak_Schems_Before.JPG|300px|left|thumb|Bally Cheap Squeak Sound Board Schematics w/ incorrect info]]
[[File:BLY_Cheap_Squeak_Schems_After.JPG|300px|right|thumb|Bally Cheap Squeak Sound Board Schematics adjusted to the board layout]]

All Cheap Squeak schematics have the following error. Diodes D7 and D8 are connected opposite of what the schematics state. Also, test point (TP1) is not located where the schematics show that it is. Please see the pic to the left (original schematics), and the pic to the right (corrected areas are circled).
 

====SB-100 Sound Board====
Technical write up regarding the SB-100 sound board is located [http://www.techdose.com/projects/Stern-Pinball-SB100-Sound-Board/346/page1.html here]. 

Just some general tech notes. Please be advised of the following per the Stern SB-100 sound board schematics. A single 220mfd 50v capacitor can be installed at either position C47 and C48. Likewise, two 100mfd 50v capacitors at these two positions are acceptable substitutes. Even though the circuit board stencils are marked with a "+" on one of the cap leg positions, the capacitor(s) at these positions must bi-polar / non-polarized.
 

=====Sound Board Does not Make Sound at all=====
Much like the www.techdose.com website recommends, check for cold solder joints on all of the header connections. Since all of the generations of these boards are all single-sided, they are susceptible to cold / cracked solder joints. Also, make certain that the ribbon cables or harnesses are installed correctly. Pin 1 J5 of the MPU board should connect to pin 1 J1 on the sound board. If sound is still not present, check the voltage test points on the board. Finally, make certain that the amp is powered (a slight hum will be heard), the speaker is good, and the volume potentiometer is turned up and / or good too.

=====Missing Sounds on the Fully Populated SB-100 Sound Board=====
During solenoid test, the first 6 solenoids are allocated for sound board sounds. If sounds are only heard during the first 4 solenoids during test, it may not be that they are actually missing. Make certain that the MPU dipswitch 23 is set to on, otherwise only the first 4 sounds will be triggered during solenoid test. Hearing only 4 sounds is normal operation, if the sound board is set for chime sounds only. 

=====Missing Sounds on the Less Populated SB-100 Sound Board=====
The sounds for the games using the less populated boards are not the first 6 solenoids, like the fully populated sound boards. Instead, the sounds are the last things triggered during solenoid test. And, if the game's dipswitch is set for chimes (dipswitch 23 on some of the later games), no sounds will be heard, when the sound board's sounds should be triggered. 

=====Second Generation SB-100 Sound Board Does not Allow MPU to Boot (Typically After a Successful 1st Boot)=====
[[File:Stern SB11 SB-100 Reset.jpg|thumb|300px|left|Stern Service Bulletin 11]]
[[File:Stern SB-100 Less Pop Reset Front.jpg|thumb|right|300px|Stern SB-100 Less Populated (second generation) Sound Board. Note the 47Kohm resistor installed in place of a standard jumper, and the tantalum cap installed from one leg of the unpopulated C52 to the 47Kohm resistor. This is a common factory fix found on most second generation SB-100 sound boards.]] 
At some point, Stern released a service bulletin, regarding a fix to keep from erroneous info showing up in bookkeeping, due to "multiple toggling of the power switch of the game". With this bulletin, it recommends that a 47Kohm resistor and 3.3uF 6v tantalum capacitor be installed on the /RESET line of the 74107 chip. Likewise, pin 25 at J1 should be removed from the SB-100, or removal of the line that comes from the MPU, as this is the data line that carries the /RESET line. 

[[File:Stern SB-100 Less Pop Reset Line 74107 Back.jpg|thumb|300px|left|Factory modification on second generation board where /RESET line and +5V is tied together presuming that J1 pin 25 is removed.]]
[[File:Stern SB-100 Early Cut Reset.jpg|thumb|300px|right|/RESET line cut on a second generation sound board]] 
What is not stated in the service bulletin is that if pin 25 of J1 or the cable is not removed, the /RESET line and the +5V on the SB-100 will be tied together. The end result is a sound board that seems fine upon the very first boot of a "cold" game. If the game has been on at all, subsequent attempts of turning the game on and off results in an MPU board that is locked up. The signs of it locked up are that the diagnostic LED on the MPU board will never come on or is on immediately and stays locked on. The sound board also may belch out a very obnoxious loud BLURT, akin to a siren which does not descend in sound, that continues unless the game is turned off.

To resolve the problem without question, it is best just to cut the /RESET line right before it is tied to the +5V line.

Although this issue has not been observed on the first generation SB-100, which is fully populated, it can occur if the suggested service bulletin modification is performed.

One thing to note is that this problem doesn't appear to occur when using an Alltek Ultimate MPU board. Also, the problem can be overcome when using a Two Bits Fix-It board by pressing the reset button (performing a hard reset).
 

=====Removing the Sound Blurt from the SB-100 Upon MPU Boot Up=====
[[File:Stern SB-100 MCP120-460DI Reset Gen.jpg|thumb|300px|left|An MCP120-460DI reset generator and 4.7K pull up resistor added to the 2nd generation sound board]] 
Don't like the initial "PEW" sound that the SB-100 board blurts out when the MPU first turns on, add a reset generator to the board. A reset generator can be added to the sound board, which ties the /RESET line of the reset generator to pin 10 of U6 (the CLR signal for the 74107). In this example, an MCP120-460DI reset generator was used along with an external 4.7Kohm pullup resistor. Note that a small hole must be drilled into the board to pick up the needed +5V for the center leg of the reset generator. An MCP130-460DI can be used just as easily, and an external pullup resistor will not be needed. The board shown here is a 2nd generation board. A 1st generation board should be the same procedure.
 

=====Mapping the Sound Signals on the SB-100=====
[[File:Stern SB-100 Sound Signals Input.jpg|thumb|300px|left|SB-100 sound signals noted on the input side of the board.]]
[[File:Stern SB-100 Sound Signals Output.jpg|thumb|300px|right|SB-100 sound signals noted on the output side of the board.]] 
These two pics show the specific six different sound paths of the SB-100. If a specific sound is missing from the board, hopefully these will help in locating the failure point a little easier.
 

[[File:SB-100Annotated.jpg|thumb|500px|left|SB-100 sound signals annotated on a hi-resolution image. Cleaned up image provided by PinSider La4s. Annotation by Jim Palson.]] 
The image at left consolidates the two images above.
 

=====Bench Testing the SB-100=====
Connect the SB-100 board with the two ribbons normally used to connect the board to the MPU.

Additionally, connect the following as shown below...
* J2/6 - 12VDC
* J2/3 - Ground
* J3/8-9 - Speaker
* An 8Kohm resistor across J3 pins 1 and 3. 8Kohm provides a reasonable volume for debugging.
[[File:SB-100BenchTestConnections.jpg|300px|thumb|left|Bench connections for the Stern SB-100 sound board]]
 

=====Adjusting the Sound Quality on a Stern SB-100 board=====
Earlier versions of the Stern SB-100 Sound board can have an unpleasant high pitched sound for all the different sounds. STERN advises the following changes to lower the frequency of the tones, which sound much better to my ears.

* Replace all 3 of the 5k potentiometers at R2,R6, & R13 with 25k ohm pots. Suggested part # is 15mm Piher PT15LH06-253A2020
* Replace the 2.2k ohm resistor at R12 with an 8.2k ohm 1/4 watt resistor
* Upon completion of component replacement, adjust the trim pots according to the instructions below

[[File:Stern SB-100 Pots TPs.JPG|400px|thumb|left|The 3rd generation SB-100 with pots and complimentary test points notated]] 
Adjust the frequencies by putting the BLACK lead on ground (TP4) on the sound board and the RED lead of the multimeter set to the frequency setting (Hz) on the appropriate test point (see below and the pic to the left). Then, turn the pots one way or the other in small increments to the following specs. 

TP2 Adjust R6 138 Hz +/- 3Hz 
TP3 Adjust R2 104 Hz +/- 3 Hz 
TP5 Adjust R13 172 Hz +/- 3 Hz 
 

====SB-300 Sound Board====
Technical write up regarding the SB-300 sound board is located [http://www.pinball4you.ch/okaegi/rep_soundsb300.html here].

If some of the sounds are missing or incorrect when using a SB-300 sound board with an Alltek MPU board (e.g. especially noticable for the spinner sounds on a Meteor), try clearing memory on the MPU board to see if that fixes the issue.

 
=====Stern SB-300 Sound Board Modification for VSU-100 Usage=====
Games with a VSU-100 speech card require a modified SB-300 to utilize the speech. First, see if your SB-300 already has a trace for this connection by checking continuity between pin 5 of the rightmost connector at the bottom and the top of capacitor C14. If you read continuity, you do not need to do this mod. 

<center>
<gallery widths=300px heights=300px perrow=3 caption="Stern SB-300 Added Jumper Modification for Speech">
File:sb300sig3.jpg|<center>First solder point for jumper (pin 5 of rightmost connector)</center>
File:sb300sig2.jpg|<center>Second solder point for jumper (top of capacitor C14)</center>
File:sb300sign1.jpg|<center>Overall picture of jumper</center>
</gallery>
</center>
 

====VSU-100 Speech Board====
Unlike most all other combination sound speech boards made by Bally, Williams, and Gottlieb, Stern did not use a potentiometer for mixing the sounds and speech volume. 

If the speech is nonexistent, first make certain that the SB-300 sound board has the appropriate jumper added. The jumper goes between the right .156 connector pin 5 and the top of capacitor C14. Later revision SB-300 boards have a trace on the board for this so measure for continuity between those 2 points; if it is there, no need to add the additional jumper. Next, make certain that the EPROMs installed are valid. Very common for bad 2716's to cause the board to not work. You can replace both 2716's on games that use both U9 and U10 with a single 2532 installed into U9. Create this eprom file by using the DOS copy command: copy /b u9.716 + u10.716 u9comb.532. For Flight 2000, which only uses U9, just copy /b u9.716 + u9.716 u9f2k.532, or just burn the image into the lower half of a 2532. No jumper changes are needed to do this conversion, but you must make sure you only have ONE eprom installed in to u9 - you cannot install or leave an eprom into u10 due to the way the VSU-100 handles addressing. 

If the speech is much lower than the sound, suspect capacitor C6 first. 

Although the S14001A speech chip is somewhat expensive, it is still available from some online outlets. Do not assume that this chip is bad just because the speech is not working - it is more common for support components or missing voltages to cause speech board issues.

There is a short jumper handling the pass-through signals to the lamp board which uses IDC connectors, these can be problematic and cause lamp issues. A cable can be built with discrete wires and .100 connectors to replace this often overlooked issue.
 

===Flipper problems===
[[File:SeaWitchMeteorFlipperResistor.jpg|left|thumb|300px|Upper Flipper Mech with 1ohm sand resistor in series. Image courtesy of David Rowland.]] 
Some games, like Meteor and SeaWitch, make use of a 1ohm resistor, in series with the flipper coil "power winding", to reduce flipper power strength, while using a "standard" coil. This prevents drop targets from being damaged and allowed Stern to use the same coil across their game production.
 

====Rebuilding Flippers====
Nothing makes more of a difference on a game than having taut, crisp, flippers. Even if every other mechanical component on a game is rebuilt, if the flippers are sluggish and weak, players walk away with a sour taste of the games' experience. At a minimum, flippers should be taken apart, inspected for wear, have their coil sleeve replaced with new, and reassembled while dressing any worn plungers/stops with a file. Additionally, the end of stroke switch should be filed and adjusted, as well as the cabinet switches that actuate the flippers.

It is best to replace the plungers and links, the coil stop, and the end of stroke switch(es) with brand new components. Quality varies in replacement parts for this era game, with some components being completely unavailable in suitable replacements. One example is the proper Stern coil stop for flippers - while there is a modern replacement, it is very expensive and does not seem to work as well as the original copper colored stops. You can swap the copper stops from stern pop bumpers which show very little wear into the flipper positions. The worn stop from the flipper will usually work on the pop bumper fine as the pulse rarely pulls the pop plunger down to the stop (hence why they are perfect to swap).

Another part that seems to be available are replacement flipper bats for Stern games - while they will fit and work, they are slightly fatter in profile at the inlane end and will cause flipper hop.

Recently a supplier (pinballlife.com) has started remanufacturing classic Stern style flipper parts in the generation 2 style as well as Bally flipper parts and full flipper assmblies. The flipper plates are a welcome addition to the repair arsenal, as the holes are usually stripped out from hacky repairs over the years.

When reassembling the flipper, check the bushing for cracks or wear - the bushing's job is to hold the flipper bat square to the playfield at a high enough height to prevent the flipper from dragging across the playfield surface, causing gouging and wear. Be sure the flipper has a slight up-down leeway built in at both rest and at extension. The inlane guide should be a smooth transition from guide to flipper; while you can't adjust the flipper to tweak this, you can and should adjust the lane guide.

====Converting Bally or Stern Flipper Assys. to WMS WPC Style Flipper Assys.====
[[File:Stern Flipper Wiring Diagram.png|300px|thumb|left|Standard Stern flipper wiring diagram]]
[[File:Stern Flipper Wiring Diagram WPC Coils.png|thumb|300px|right|Stern flipper wiring with WPC coils installed]]
[[File:Stern Lower Left Flipper Stock Wiring.jpg|300px|thumb|left|Stern lower left flipper - stock wiring]]
[[File:Stern Lower Left Flipper WPC Wiring.jpg|thumb|300px|right|Stern lower left flipper - WPC wiring]]
[[File:Stern Lower Right Flipper Stock Wiring.jpg|300px|thumb|left|Stern lower right flipper - stock wiring]]
[[File:Stern Lower Right Flipper WPC Wiring.jpg|thumb|300px|right|Stern lower right flipper - WPC wiring]] 
Considered drastic by some, while sacrilege by others, converting Bally or Stern flippers to Williams WPC style flippers can be done. The only restriction may be whether or not the Williams flipper plate, which has a much larger footprint, will fit for a specific application or not. The closest Williams flipper coil in strength is the FL-11630. It is remarkably similar. It is also recommended to use the A-12390 coil stop. The A-12390 coil stop will result in nearly the same stroke at the Stern original flipper set up. Also, use end-of-stroke switch 03-7811. This was the EOS switch used on pre-fliptronics Williams games. If using the original Stern EOS switches, the long blade may need to be trimmed back. Otherwise, the blade may get caught on one of the flipper bushing screws.

As illustrated in the pics, the white wiring with the black Sharpie mark on it is the wire which goes to the secondary switch on the flippers. The secondary switch is used to send ground to the upper flippers of the game. The plain two white wires connect to the EOS switch of the flipper. Either white wire can be attached to either EOS switch blade solder lug. It does not matter.
 

===Pop Bumper Problems===
Pop bumpers on Bally/Stern games aren't that unusual, and the "usual" advice applies.

====Pop Bumper Randomly Fires====
An occasional spurious pop from a pop bumper on these games is normal. This is, somehow, an intentional artifact of the software, attempting to aggressively "debounce". These kick with full strength, but do not score. (This is discussed in the Bally Theory of Operation manual.) However, a failing capacitor on a switch may also cause issues. See the [[#Switch_Capacitor_Purpose_and_Failure|information under the switch capacitor section]] for additional details.

If the bumper activates whenever the flipper fires, check to make sure the switch is clean and gapped properly.

====Bally New-Style Pop Bumpers====
Bally changed the pop bumper assembling starting with Eight Ball Deluxe. Gone were the "Sunburst" caps. Caps are now two pieces, a large trim ring and a smaller inner logo circle.

Three tabs on the body of the pop bumper hold the trim ring on. These tabs tend to break off. Eventually, Bally added screw holes to the top of the bumper so that they could again be screwed on. Either the bumper cap or bumper body may be missing the screw holes, in which case the bumper body must be replaced.

If the original "pinned" lamp socket is present, replacing the body on these pop bumpers is quite easy. Remove the two nuts that hold the rod/ring assembly on under the playfield. Lower the playfield and remove the bumper cap and trim ring. Two screws can be removed from the bottom of the body. Pull the body off the playfield. The lamp socket will come with it, and two female housings will be holding the lamp socket on. These get pulled off. The socket comes out with a little coaxing and can be moved to the new pop bumper body.

One more note: The tabs of the bumper body were originally reinforced with a thin ring, 1mm in thickness and about as big around as the bumper cap itself. These were used to give the tabs a little more reinforcement so they don't flex and break off. Unfortunately, these are now unavailable.

===Setting Free Play===
If you read the manual that came with your game, you'll notice there are no factory provisions for setting the games on non-coin play. There are several options for homeowners to set their machines up so quarters or opening the coin door aren't required.

'''Free play via low replay scores'''

The easiest way to keep a quantity of credits on the machine is to set the first replay score to a very low value (10,000 on most machines). This way you can put several credits on the machine initially, and then each game played will probably win a credit. Press the self-test button inside the coin door until you see "01" in the ball-in-play display. Press the button on the mpu board itself (S33) to clear this value to zero, then use the credit button (on the coin door) to step the setting one click forward to 10,000. (Some games let you 'flick' a coin door switch to zero the value, S33 works for all games)

In most cases you will score 10,000 very quickly enabling the machine to self-replenish its credits.

'''Free play via adding a switch'''

If you like having the 'coin-up' sound most machines make, adding a free play switch to a game is relatively simple. Any type of normally open switch can be soldered to one of the coin switches and mounted in an unobtrusive way (through the coin door return is a popular example, or mounted to the coin return instead). While it is also possible to drill a hole in the cabinet or coin door to mount this type of switch, it is discouraged to do this as it is difficult or impossible to reverse cleanly.

This type of switch can be piggybacked onto the credit button switch itself, the initial full press will add a credit, and the pullback stroke will start a game.

'''Free play via ROM replacement'''

As of this writing, free play replacement ROMS are available for all Bally/Stern games. For many years only Bally freeplay roms of various flavors were available, and these romsets are incorporated into some of the aftermarket replacement MPU boards. In 2009 freeplay roms became available for all the stern mpu-100 and mpu-200 games as well, but as of yet (6/2020) are only incorporated into the Weebly replacement board (https://nvram.weebly.com/new-pcbs.html).

Some varieties of free play roms never let the credits go below one, some require a DIP switch setting, and some are free play only. Regardless of the type of free play rom used, they all work similarly. When the credits fall below a certain amount, the software code either increments a credit automatically, simply allows a game start with credits showing 00, or never lets the credits decrement below 01.

For many people free play roms are the preferred method of handling free play as no hardware modifications are needed to incorporate free play, and you can still have replay levels set to challenging levels. It also allows the machines to be placed in clubs, businesses, shows, etc. without the owner having to worry about people not knowing how to add credits via some other method. Press the credit button and go.

Free play ROM images for Stern MPU-100 games can be found here: [[File:Mpu100-freeplayroms.zip]]‎. 
Free play ROM images for Stern MPU-200 games can be found here: [[File:Mpu200-freeplayroms.zip]].

===Game Trips Power Line Circuit Breaker When Plugged into Outlet===
[[File:Stern Blown Varistor.JPG|300px|thumb|left|Incoming power cord, line filter, and blown / shorted varistor (Stern Seawitch)]] 
Had a thunderstorm roll through or a power surge from the electric company recently? If so, and the game is now tripping the circuit breaker of the outlet it's plugged into, without the game's power switch turned on, the [http://en.wikipedia.org/wiki/Varistor varistor] may have shorted. The varistor is used to protect the rest of the game's circuitry from power surges. 

Both Bally and Stern use varistors, which are typically located on the left cabinet wall. The varistor leads are soldered directly to the junction of the two power cord leads (hot and neutral) and the line side of the line filter. 

The obvious sign of a failed varistor is typically a black, charred discoloration throughout the "button" portion of the varistor. Varistors can blow rather violently, as seen in the adjacent pic, and there may be charred or burnt remains in the area surrounding the varistor. 

Varistors can be purchased from [https://www.greatplainselectronics.com/products.asp?cat=76 Great Plains Electronics]. Order the 130V variant for 120VAC (typically games in the US), and the 275V variant for 240VAC (typcailly games in Europe).
 

===Bally/Stern LED stays on after boot===
7th flash produced but no led dimming afterward:
The problem was one of the capacitors around the u12 (clock signal) were bad. I replaced c12,c16?, and c17. After that I
got the 7th flash and the dimmed led afterward.

===Solenoid Expander Board===
[[file:Solenoid_Expander.jpg|300px|thumb|left|alt=alternative text|Bally Solenoid Expander board- Arrow indicates necessary bulb]] 
There is a 555 bulb near (or sometimes not so near) that lights when the solenoid expander is activated. This bulb is essential for proper operation of the expander as the main opto isolator chip on the expander board needs a load to work. If you're having entire sets of solenoids not working, check this bulb. 

The header pins on this board like to crack, also, so standard operating procedure should be to replace or at minimum resolder the headers, and re-pin the connector with Trifurcon connectors. 

Also, it's very important that all solenoids on the expanded circuits have *TWO* diodes on them! If a coil was replaced with one that one had only a single diode, multiple solenoids could potentially activate on any solenoid expanded solenoid. Some side effects of a single diode coil installed could be a "memory" drop target activating when it shouldn't, or a target bank reset engaging when a saucer is supposed to eject.
 

===Using a Bally 7 digit display in a Stern game or using a Stern 7 digit display in a Bally game===
Bally and Stern 7 digit displays are interchangeable. However, Stern displays do not support commas and a small modification to the printed circuit board is necessary to make each board display all 7 digits in a "foreign" platform. 

First, use a small jumper to connect J1, pins 11 and 12 together. Bally and Stern chose different pins (Bally used pin 12, where as Stern used pin 11) to strobe the 7th digit. Without this mod, placing a Stern 7 digit display into a Bally game will result in the 7th digit not being displayed (and vice versa). Making this modification creates a "universal" Bally/Stern 7 digit display. 

[[File:Stern Bally Display Depth.JPG|300px|thumb|left|Comparison between the PCB size of a Bally and Stern 7-digit display]]
[[File:Stern Display Trays.JPG|300px|thumb|right|Stern display trays - 7-digit player displays are mounted to back of insert, while shallower 6-digit status display is mounted to front]] 

Bally and Stern also chose a different depth dimension for their display PCBs. Fortunately, the difference can be accommodated merely by mounting the display tray on the opposite side of the lamp insert panel. Note that this is also necessary when using "PinScore" displays in a Stern game. Alternatively, if using a Bally (or PinScore) display in a Stern game, since the Bally circuit board itself is not as deep, insert the display only as far as necessary for it to "flush up" to the backglass when installed.
 

[[File:Bally 7digit Stern Status.JPG|300px|thumb|left|Bally 7-Digit display used as a Stern status display before modification]] 
Bally displays automatically show '''commas''' whenever the thousands and millions digits are lit. To make a Bally display "match" the Stern display's non-comma capable display, clip the base lead from Q22 and commas will no longer light up. You can alternatively clip one end of diodes CR1 and CR2 and lift the diodes off the board. This modification would be easier to reverse.
 

Since Stern 7 digit displays do not support commas, using a Stern display in a Bally game will look a little "off" versus the other displays in the game, but this will get your displays running if you have no other choice.
 

=== Bally Game running slow (delayed score, controlled lamp flicker) or if game crashes before attract mode starts ===

If your Bally game is running very slow (solenoid pulses are delayed and long, controlled lamps flicker, scoring takes a few seconds to register) or if your game boots with the typical 7 LED flashes but then crashes (dead game with garbage on the displays), before attract mode starts you may have a bad C16 capacitor. C16 controls the display interrupt speed. If it is out of spec, it could cause the gap between display interrupts to be too small, leaving the processor no time to service other game operation. C16 is in the corrosion area near the 555 timer.

[[image:YT.png]] A YouTube video of a slow game caused by a failed capacitor at C16 can be viewed [http://www.youtube.com/watch?v=TlGMGLHrDD8&feature=channel_video_title here].

A game running slow can also be caused by a failed U14, which implements the "zero crossing" circuit.
Do NOT use the HEF4049. These will cause controlled lamps flicker.
CD4049 is a good choice.

===Converting a Bally -17, -35 or Stern -100 CPU Board to a Stern -200===
Stern MPU-200 CPU boards are probably the least common of the four CPU boards. The -200 boards are compatible in -17, -35, and -100 games. Although considering that -17, -35, and -100 boards are much more prevalent, it would be somewhat of a waste to use a -200 in any of these games. What if the more common boards could be converted to a -200? Check out [https://web.archive.org/web/20160309024537/http://warpzonearcade.com/?p=580 WarpZoneArcade's] blog entry to find out how to modify a -17, -35, or -100 to work as a -200.
 

==Game Specific Problems and Fixes==
===Stern Seawitch===
====Ball Trapped on Upper Left Flipper Plastic====
[[file:Seawitch-Protector2.jpg|left|300px|thumb|alt=alternative text|Ball deflector installed on a Seawitch]]
'''Problem:'''The ball gets trapped between the glass and the left side plastic above the 3 drop targets, from a hard shot to the center 3 drop targets. 

'''Solution:''' Cut a 11" (28cm) long by 5/8" to 7/8" (16mm to 22mm) strip of acrylic commonly used for home window glass replacement. Acrylic sheet can be scored and cut with a knife, but a bandsaw works best. Remove the plastic protector sheet, and plan the areas and angle you wish to bend.

With a propane torch (the instant on Bernz-o-Matic is great for this), heat the bend area for 2 seconds, and form the bend freehand or with a tabletop. The acrylic will stay soft and bendable for about 20 seconds, so if the angle is not right you can change the bend with or without additional heat from the torch. Clean up the cut edges and corners with a file and/or sandpaper. Brackets can be made out of thin stainless or mild steel. Keystone makes a bracket that is small and has 1 hole tapped for a 6-32 screw. (Manufacturer P/N#614 or Mouser P/N 534-614) A 6-32 nut & 3/8" computer case screw can be used to provide the needed clearance.
 

[[File:Seawitch Ball Trap Lexan.jpg|left|300px|thumb|Flat Lexan Ball Deflector installed on a Seawitch]] 
[[File:Seawitch Ball Trap Standoff.jpg|right|300px|thumb|Style of standoff used to secure Lexan to playfield]]
Here is an alternate method to keep from balls getting trapped on top of the plastic behind the upper left flipper. First, remove the existing large plastic behind the upper left flipper. Next, place the plastic onto a piece of Lexan, and trace the right side of the plastic's shape onto the piece of Lexan. Make certain to use enough of the plastic to cover the 3 screw holes in the vicinity of the flipper. These 3 screw holes will be used to secure the Lexan. Now, cut the piece of Lexan with a jigsaw. The edges can be smoothed with a file or sandpaper. Next, again place the plastic on the Lexan, and if satisfied with the results, mark the 3 screw holes that secure the plastic to the threaded metal standoff posts. Using about an 1/8" bit, (double check the exact size), drill the holes where the Lexan is marked. Place the original plastic back on the playfield. Take 3 nylon standoffs, which are typically used to secure circuit boards to a flat surface, and screw them onto the threaded metal standoff posts, where the nylon or rubber cap nuts would normally go. Do not use too long of a post, otherwise the playfield glass will hit the Lexan. Standoffs can be purchased from [https://www.greatplainselectronics.com/products.asp?cat=134 Great Plains Electronics]. Finally, firmly place the piece of Lexan down on the 3 nylon standoffs. 

====Upper Flippers Power Resistor====
[[File:Seawitch Upper Flip Resistor.JPG|300px|left|thumb|Power Resistor Installed in Series on Upper Left Flipper (Seawitch)]] 
On Seawitch, both upper flippers have a single 1 ohm 5 watt power resistor installed in series with the power winding of each flipper coil. Neither resistor is listed in the game's manual or schematics. It is presumed that the resistors were installed due to the upper flippers close proximity of nearby drop targets and plastics. The resistors are not necessary for proper function, and could be by-passed, but it is best to keep the resistors installed. The lack of this resistor will increase the flipper power, and more frequent breakage of drop targets or plastics may result. 

Similar resistors were installed on other Stern games at this time typically on upper flippers that were close to targets.

An alternate to leaving the resistors in place (used in this application as a crude voltage reduction device; i.e. runs very hot and causes burn marks on the bottom of the playfield) is to open up the end of stroke switches instead. The flipper will flip with less power which is the intended goal.
 

===Stern Hot Hand Not Booting at 5th Flash or Game Locks-up at Game Over===

If you find that your Stern Hot Hand game sometimes won't boot-up on the 5th flash; or that sometimes at Game-Over the displays go blank and the game dies, there is a good possibility it's the rotating flipper motor. The rotating flipper is pulsed briefly (on/off) as a byproduct of the PIA U11 test (5th flash) during boot-up. It also rotates constantly during a game and shuts off at game-over.

[[File:SternHH.png|300px|thumb|left|Diagram of the Stern Hot Hand motor showing the capacitor and MOV soldered across the motor terminals]]
The rotating flipper motor is connected directly to the 48V terminals 2 and 6 of the transformer. The 48V to the motor is controlled by a relay mounted to the motor bracket. Q18 on the Solenoid Driver Board energizes and de-energizes the relay coil which turns the motor on and off. When the motor turns off, it sends a voltage spike (EMF collapsing) that can sometimes be picked up by the MPU and cause the game to not boot (5th flash) or just shut down after game-over. During the boot sequence U11 PIA test (5th flash) the game enables all solenoids briefly as an artifact of how the test is performed. The slight on/off and resulting EMF pulse during the boot up on the 5th flash can cause the MPU to lock up.

Apparently Stern didn't realize this issue until later and seemed to have modified Orbitor 1 to suppress the spike. On Orbitor 1, there is both a 1uF, 2kV capacitor and 130V Metal Oxide Varistor (MOV) in parallel across the bumper motor terminals. This can also be accomplished with a 2.2uF, 250V mylar film capacitor and a 100V MOV soldered in parallel across the motor terminals. These devices help suppress the voltage spike
at the motor and keep it from reaching the MPU and causing lock ups. Simply solder both the MOV and capacitor across the rotating flipper motor terminals. The capacitor and MOV are not polarity specific so it doesn't matter which device lead goes on which motor terminal.
 

===Stern Meteor===
There is a software bug in Meteor's software concerning the bonus countdown - you will get a seemingly endless bonus multiplier at the end of your ball. (It's actually 255 x)

This is caused by a re-use of a memory location that holds your original bonus multiplier value during bonus countdown. The memory location is shared with the "collect all rockets" subroutine on the outlanes. If the software is dealing with lots of active threads, such as the spinner spinning at the same time as the collect all rockets and outhole subroutine are active, the bonus multiplier will become zero and count down from 255->1.

An updated game ROM named "U1a" includes a patch for the bug and is available on [http://www.ipdb.org/machine.cgi?id=1580 the Meteor IPDB page].

===Stern Orbitor 1===
Two balls need to be in the trough on boot up, or else you will hear "shoot pinball again" over and over with no attract mode

===Centaur===
If the game is missing any of the pinballs (or a bad trough switch) the game will not fully boot. The displays will show all "0"s across all displays. Hitting the test button will allow you to enter the test menu, and you can proceed to switch test to diagnose the trough switches.

==Parts Substitutions & Replacements==

===Components===
====Driver Board LM323K 5V Regulator====
Since the LM323K has become scarce, with mainly just sub-par Chinese knock-offs and counterfeit components available as replacements, an alternative is the [https://www.ezsbc.com/product/psu5/ EZSBC PSU5 LM323K replacement], and [https://www.ezsbc.com/product/psu5-nonoise/ the newer "no noise" version] for games exhibiting speaker noise when using the original style PSU5.

When installing on a Bally solenoid driver board, be sure to remove R49 since it adds an unnecessary load to the device (which is only necessary with a real LM323K), and replace R50 with a jumper, since the this device expects a direct path to ground. However, make sure to use an actual wire for the jumper and not a zero ohm resistor. A lot of current can surge through this critical connection and the wire on some zero ohm resistors may be too thin to handle it, which can result in voltage drops.

When using the PSU5, the large heatsink required by the LM323K is no longer needed and can be removed. It can also be left in place in the event that it is ever needed in the future.

Note that since the PSU5 is a switching device (rather than a linear device like the LM323K), it may introduce noise/static (or a "machine gun" sound) to the sound board or speaker. Adding a 1000uf/20v capacitor to the driver board between the 5V trace and the ground trace near J3 may help reduce or eliminate the issue.

An updated version of the PSU5, called the PSU5NN (NN = no noise) eliminates the "machine gun" sound sometimes imparted when powering a game down with the older version of the PSU5 installed. It can be found [https://www.ezsbc.com/product/psu5-nonoise/ here]. 

[[File:Bally5VAdjust.png|400px|thumb|left|Resistors that can be used to adjust output of the OEM LM323K or 78H05. (Image courtesy of PinSider barakandl)]]
[[File:EzSBCBallyStern.jpg|300px|thumb|right|A Stern Solenoid/Driver board updated with the ezSBC 5V regulator. R49 has been removed (previously located where the dotted line is) and R50 ha been removed and replaced with a beefy wire jumper. R49 and R50 are pictured laying on the board for reference. (Image courtesy of Chris Hibler)]] 
In the standard Bally/Stern implementation, resistors R49 and R50 increase the output voltage, presumably to accommodate voltage loss across connectors and the variance within the LM323K 5% specification.

If the LM323K outputs a perfect 5.00 volts between its pin 2 and 3, R49 and R50 will increase the output voltage according to this simplified equation:

*Vout = 5.00 * (1+ (R50/R49))

Bally and Stern used a 100 ohm resistor at R49. 
Bally used a 2.2 ohm resistor at R50. 
Stern used a 4.7 ohm resistor at R50.

Therefore, based on the above formula, a Bally board will deliver about 5.11 volts. 
A Stern board, based on the above formula, will deliver about 5.23 volts.

The specified tolerance of the LM323K is 5%. 
A 5% tolerance means that parts will deliver somewhere between 4.75 and 5.25 volts. 
Using Stern's resistor values, with a LM323K delivering the spec maximum of 5.25 volts, the formula above yields an output of 5.49 volts.
 

===Available 3D Printed Replacements===

With the increased availability of 3D printed parts, some Bally and Stern parts are being offered up via Shapeways and other 3D object marketplaces. Some of the available parts are:

* [http://www.shapeways.com/product/5A3C6F67G/bally-pinball-ball-outhole-kicker-arm-c-972-3?li=shop-results&optionId=43401482 Bally C-972-3 outhole kicker arm] used on games like Fathom 
* [http://www.shapeways.com/product/Z49NGF785/bally-ss-pinball-1-globe-light-shroud-upgrade?li=shop-results&optionId=43386300 Bally lamp insert single lamp shroud] 
* [http://www.shapeways.com/product/TNXKP3CPZ/bally-ss-pinball-2-globe-light-shroud-upgraded?li=shop-results&optionId=41384171 Bally lamp insert double lamp shroud] 
* [http://www.shapeways.com/product/X9SK45SSM/bally-pinball-rollover-button-c-587-6-ss-em?li=shop-results&optionId=43385429 Bally C-587-6 miniature white rollover button] used on games like Xenon 
* [http://www.shapeways.com/product/WV6TYWTKB/80-s-stern-ss-pinball-coin-plate-chute?li=shop-results&optionId=43403498 Stern coin insert plate] it is assumed that these have large enough slot openings to accept dollar coins
 

===Repair Logs===
====MPU boot halts after 2nd flash on Centaur====
Note: One possible reason that the boot process may stop after 2 flashes is if MPU J1 connector and lamp board J1 connector have been swapped, as indicated by this repair:
Here's a weird gotcha. While reconnecting the wiring harness to a previously known working Centaur II, the game wouldn't boot (only 2 flashes). We swapped in a known working Alltek reproduction board. Same symptom! After looking at a set of Centaur schematics we had on hand, the first half dozen pins of J1 on the MPU were striped wires, while the schematics called for solid-colored wires. Wait a minute... That's when we realized that the J1 connector on the MPU and the adjacent lamp driver board are not only the same number of pins, but the same KEY!! ARGH!!! Thankfully no damage was done on these low voltage lines. Swapping the MPU and lamp driver boards' J1 connectors resulted in a perfectly bootable/functional game. Why this accidental swap caused the 5101 RAM check to fail is an exercise left to the user.