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Williams System 9 - 11

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1 Introduction

Williams System 9 Board Set from Space Shuttle
Placeholder for Williams System 11 Board Set from xxxx
Williams System 11A Board Set from Pinbot
Williams System 11b Board Set from Jokerz! (Note that power supply is a prototype)
System 11b Board Set from Earthshaker. The CPU board pictured is upside-down and harness has been removed
Placeholder for Williams System 11c Board Set from xxxx

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 interboard 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. . . (add more info later)

2 Games

2.1 System 9

Title Date of Release Model # Sound Other Boards Notes
Strike Zone 1984 1916 unknown This is a shuffle alley which uses some pinball boards
Star Light 06-1984 530 no speech only a few were made with System 9 boards inside
Space Shuttle 12-1984 535 C-10716 (Speech only)
Sorcerer 03-1985 532 C-10716 (Speech only)
Comet 06-1985 540 C-10716 (Speech only)

2.2 System 11

Title Date of Release Model # Sound Other Boards 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)
Grand Lizard 04-1986 523 C-11030 (Background sound only)
Road Kings 07-1986 542 D-11197-542 (Background music only)

2.3 System 11A

Title Date of Release Model # Sound Other Boards Notes
Pinbot 10-1986 549 D-11297-549 (Background Speech & Sound)
Tic Tac Strike 11-1986 1919 Unknown This is a shuffle alley which uses some pinball boards
Millionaire 01-1987 555 D-11298-555 (Background Speech & Sound)
F-14 Tomcat 03-1987 554 D-11298-554 (Used on 1st 5,000 games - Background Speech & Sound) / D-11581-554
Fire! 08-1987 556 D-11581-556
Fire! Champagne Edition 09-1987 556 D-11581-556

2.4 System 11B

Title Date of Release Model # Sound Power Supply Aux Power Driver Master Interconnect Notes
Big Guns 10-1987 557 D-11581-557 D-8345-557 D-11583-557 C-11762 Uses D-11814 Flash Lamp Resistor Board
Space Station 12-1987 552 D-11298-552 D-8345-557 D-11813-552 C-11762-552 Uses D-11814-552 Flash Lamp Resistor Board
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 D-11581-564 D-8345-557 D-11813-574 C-11762-564 Uses D-11814-564 Flash Lamp Resistor Board
Banzai Run 05-1988 566 D-11581-566 D-8345-566 D-12247-566 D-12112
Swords of Fury 06-1988 559 D-11581-559 D-8345-557 D-12247-559 D-12313-559
Taxi 08-1988 553 D-11581-553 D-12246-553 D-12247-559 D-12313-553
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
Earthshaker 02-1989 568 D-11581-568 D-12246-568 D-12247-559 D-12313-568
Black Knight 2000 04-1989 563 D-11581-585 D-12246 D-12247-563 D-12313-563
Transporter the Rescue 04-1989 2008 D-11581-2008 D-12246 D-12247-2008 D-12313-2008
Police Force 08-1989 573 D-11581-573 D-12246 D-12247-566 D-12313-573
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
Bad Cats 11-1989 575 D-11581-575 D-12246 D-12247-566 D-12313-575
Mousin' Around! 12-1989 2009 D-11581-2009 D-12246 D-12247-2009 D-12313-2209
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

2.5 System 11C

Title Date of Release Model # Sound Other Boards Notes
The Bally Game Show 04-1990 2003 D-11581-2003 Uses a C-13286 Sound Overlay Lamp Board
Pool Sharks 06-1990 2014 D-11581-2014
Rollergames 06-1990 576 D-11581-576
Diner 09-1990 571 D-11581-571
Radical! 09-1990 2015 D-11581-2015
Dr. Dude 11-1990 2016 D-11581-2016
Riverboat Gambler 11-1990 50007 D-11581-50007
Bugs Bunny's Birthday Ball 01-1991 20009 D-11581-20009

Game date of release and model numbers provided by the Internet Pinball Database -

3 Technical Info

System 9 eliminated a huge issue with the earlier system 3 through 7 boardsets - the 40 pin interconnector used between the MPU and Driver boards. Now, all the circuitry of the mpu, driver, and sound boards was contained on one board. Helper boards were still used for displays, speech, special purposes, and solenoid expansion. Starting with Banzai Run, Williams re-introduced a weak link into their system: the interconnect board, itself designed to eliminate many under playfield flasher driver boards, which had proven themselves problematic.

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. It does this via a relay on a separate board called the A/C relay. The theory is that coils that are seldom fired 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, letting the flashers be driven. If the driver transistor for the A/C relay itself is bad, the relay defaults to the coil side, allowing the game continue to operate in a semi-normal 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 like a sling coil or pop bumper coil. (Data East's boardset was essentially a copy of the system 11 boardset - but they programmed it the opposite way, so that the flasher side of the A/C relay is active by default. So on a Data East game when the A/C relay doesn't operate, the game 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 boardsets - they still utilize special solenoid circuitry. The pops and slings on system 9/11 games do not activate a switch which is seen by the mpu's program which fires the coil - instead, the switches directly fire their associated coils via some 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).

The software in system 9-11 games continued the state machine architecture from system 6 and 7. More ram became available, up to 2k, but no game used over 800 bytes. This is likely due to the obsolescence of earlier style ram chips more than any other reason. Additional diagnostics in the form of switch error checking appeared in system 11; any switch not being activated over 30 games (16 games for flipper switches) would cause an error flag at bootup. The software was able to compensate for broken switches by designating another switch to perform the same function as the broken switch.

3.1 MPU Driver Boards

Williams used a single version of the System 9 MPU in all System 9 games.

System 9 MPU

System 9 MPU

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).

System 11 MPU

System 11 (nothing) MPU
This picture shows the early System 11 MPU. There is a later revision available which has an additional jumper W16 located between the 7 digit display and the relay. This early pcb 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.

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).

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 plain 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.

A rare prototype System 11a MPU

System 11a Prototype MPU
This MPU was only used in Pin Bot. It's actually a System 11 MPU with the 7 segment replaced by the factory with the 3 LEDs used in System 11A. The latest trace revision of this board also has the ground mod 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.

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.

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.

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.

3.1.1 Converting the System 9 Rom Images to System 11

You can easily create System 11 compatible rom images with the existing roms. Below you will find DOS/Windows copy commands to do this. The file pad.732 is not part of the existing roms. It's a 4K (4096 Bytes) binary file filled with 0xff. Create it using your favorite hex editor, or download here: The System 11 CPU will work out of the box with a 27128 eprom at location U27 but you might want to double it up to a 27256 anyway so that it's size is the same as the other System 11 U27 roms.
Remove jumper W8 and insert jumper W9 on the System 11 CPU or you sound will likely not work. System 11 controls the sound reset via software. Space Shuttle

copy /b 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 Sorcerer

copy /b ..\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

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 is jumpered for the 27128. Comet

copy cpu_u49.128 /b cpu_u21.128 /b
copy spch_u7.732 /b + spch_u5.732 /b + spch_u6.732 /b + spch_u4.732 /b cpu_u22.128 /b
copy cpu_u20.128 /b + cpu_u20.128 /b cpu_u27.256 /b

3.2 Sound Boards

System 9 Speech Board Using 2532 PROMs (from Space Shuttle)
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 it so either 2532 or 2732 EPROMs could be used. So when burning EPROMs, check which ones are used in your game.

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.

Background Sound board as found in High Speed
Background Sound board as found in Pinbot
D-11581 Sound Board, not Completely Populated
D-11581 Sound Board, not Completely Populated
D-11581 Sound Board, Completely Populated
D-12238 Sound Board - specific to Jokerz! only

3.3 Power Supply

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
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"

A closeup of the corrected trace routing error on a Fire! power supply board.

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.

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.

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 the board is different than later board. Exercise caution when you do board work.

3.4 Auxiliary Power Driver Board

Auxiliary Power Board from Space Station (D-11813-552)
Auxiliary Power Board from Earthshaker (D-12247-568)

3.5 Interconnect Boards

Backbox Interconnect Board from Space Station
Backbox Interconnect Board from Earthshaker

Although the first four System 11B games, which include Big Guns, Space Station, Cyclone, and Banzai Run, 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 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. 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.

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 and fuse values used for the flash lamp power circuits.

3.6 Master Display Driver Board

3.6.1 System 9

Early System 9 Master Display Driver Board

3.6.2 System 9 (Late Comet)

System 9 Comet Display Driver Board

3.6.3 System 11 (Discrete Displays High Speed to Pin Bot and Banzai Run)

System 11 Master Display Driver Board

3.6.4 System 11A (Millionaire / Early F-14)

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.

3.6.5 System 11A/B (F-14 to Cyclone)

System 11A/B 4 7 Digit Segmented Displays Driver Board

3.6.6 System 11B (Taxi and Police Force)

System 11B Display Driver Board for 2 16 digit segemented displays + one external connector for a 7 digit display

3.6.7 System 11B (all other WMS 11B/C games)

System 11B/C Display Driver Board for 2 16 digit displays

3.6.8 System 11C (Riverboat Gamber)

System 11C Display Driver Board for 2 16 digit displays and 2 connectors for 7 digit jackpot displays

Riverboat Gambler uses a 12232-3 Masterdisplay with all ribbon connectors stuffed. It is only used in this game but if it's missing from your game you can modify the older boards just fine.

3.6.9 System 11B/C (all Bally 11B/C games)

WMS Bally left side 16 digit Master Display Driver Board

WMS Bally right side 16 digit Master Display Driver Board

3.7 Other Boards

3.7.1 Sound Overlay Board (C-13287)

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.

3.7.2 High Current Driver Boards

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 Williams / Bally WPC under multiple part numbers.

3.7.3 Space Station Opto Position Board (C-11872)

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.

3.7.4 Flash Lamp Resistor Board (Remotely Located)

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.

3.7.5 Flash Lamp Resistor Board (Centrally Located)

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.

3.7.6 A/C Relay

Placeholder for A/C relay board (early design ie. F-14, Pinbot)
Placeholder for A/C relay board (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" flashers would engage. When the A/C relay was powered, the "C side" solenoids would engage.

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.

3.8 Flipper Coils

System 11 games (starting with F-14 Tomcat) use different flipper coils dependent on flipper placement and application. Below is a chart of the flipper coils used, their wrapper color, and strength.

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

3.9 Accessing Bookkeeping, Settings, and Diagnostic Modes

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 left. 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 audit or adjustments mode, the credit button is used to zero, turn off, or turn on features.

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.

3.10 Transformer Power Selection Connector

Typical power selection connection for a System 11 transformer - 115VAC (f/ Space Station)

4 Problems and Solutions

4.1 Sporadic Problems in General - System 9

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 high quality replacement header.

4.2 Power Problems

Replacement power supply If using the Rottendog WDP011A power supply for Williams Cyclone or Big Guns, you may have to move the +12v jumper from the bottom jump to the top. If your machine has GI but doesn't boot (only the 5v light on the CPU is lit) and is one of these two games, that is the most likely reason.

Bridge Rectifier Fuses A design flaw carried over from the earlier systems was the lack of fuses on the two bridge rectifiers used for the solenoid and lamp power. In theory, if either of these bridges short, the main power fuse in the game will blow, but that's not always the case. On games before Fire, interrupt one of the AC input lines and install a fuse holder with an 8 amp fuse installed. Games made after Fire already have a factory installed fuse holder and fuse on these bridges.

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.

4.3 System 11 MPU Jumpers

For normal game operation no jumpers need to be changed on the MPU board. The default configuration works with all System 11 game roms.

There are 5 exceptions:

W7: This is the language select jumper. It is only used on games up to Cyclone. Games with 16 digit alphanumeric displays do not use this jumper. If set, your game automatically reverts to English after losing the content of the ram and installing fresh batteries. Otherwise you need to change the language in the adjustments menu. So far I have only seen early System 11 roms which contain German and English text. So if cut the game usually displays German Text.
Later System 11 games have language specific roms. If your game text is in a foreign language U26 and U27 need to be changed. If you have an eprom burner you can check if your U26 is the same but to be on the safe side better exchange them both.

W16+W17: This only applies to System 11A and newer boards. The W16 jumper on original System 11 boards is in a different location and used for backwards compatibility with system 9 boards. Just leave it alone there. W16 on the 11A MPU is connected to the XTAL pin 38 of you main MC6802/08 MPU at location U15. Likewise W17 is connected to the XTAL pin 38 of the U24 MC6802/08 MPU which is responsible for controlling the sounds.
If the board uses Hitachi HD46802 MPUs these jumpers are cut. They have an incompatibility in the clock circuit compared with other brands. If the jumpers are installed ond pin 38 grounded on them the board will not boot. If using other brands they need to be installed. So if you get a non booting board from epay just check this first. If you want to use you Hitachi MPU in a System 9 or early 11 board just bend pin 38 on it away from the socket. Do not cut the pin. For whatever reason you might still want to put the processor in another board.

W5/W6 + W18/W19: This only applies to System 11B and newer boards. The System 11 CPU uses 2 6116 rams at location U23 (sound) and U25 (game). They are obsolete now. Even the common 8K 6264 ram is going the way of the Dodo now but it can still be purchased new. On later System 11B boards you can replace the 2K ram with the 8K type but a jumper needs to be set. For U23 remove W19 and set W18. For U25 remove W5 and set W6. Check your schematics; it's in them but not documented.

4.4 MPU boot issues

4.4.1 Normal Game Boot Behavior

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.

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.

+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.

+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.

4.4.2 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.

Code Description
 Normal game boot with no problems detected. The game should be in attract mode.
 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.
 U20 Game ROM 1 faulty
 U20 Game ROM 1 faulty
 U19 Game ROM 2 faulty
 Blanking signal stuck, coin door closed, memory protect circuit faulty, or the U18 CMOS RAM faulty
 System failure. Occasionally, the following components can contribute to this problem: U21 (4MhZ crystal); components in the IRQ circuit; broken leads on C9 (22uF) in the reset section; loosely seated ICs on the CPU board
Other or no indication
 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.

Code Description
 Normal game boot with no problems detected. The game should be in attract mode.
 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.
 U27 Game ROM checksum failure
 U26 Game ROM checksum failure
 not used
 Blanking signal "stuck", or the coin door is closed, or the memory protect circuit is faulty, or the CMOS RAM at U25 has failed.
Other or no indication
 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, the error message that might be displayed, and the explanation (Source: Williams System 11A game manual. with embellishment).
MEMPROT FAILURE, (use browser page search to find in page link)

Code Description Notes
 no message  Normal game boot with no problems detected. The game should be in attract mode.
 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.
 MEM. PROT. FAILURE   This message means that either:
   a) the Coin Door may be shot,
   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.
 U51 PIA FAILURE  The PIA at U51 has failed.
 U38 PIA FAILURE  The PIA at U38 has failed.
 U41 PIA FAILURE  The PIA at U41 has failed.
 U42 PIA FAILURE  The PIA at U42 has failed.
 U54 PIA FAILURE  The PIA at U54 has failed.
 U10 PIA FAILURE  The PIA at U10 has failed.
 IRQ FAILURE  The interrupt request line is not working normally. It may be missing, stuck, too fast, or too slow.
 U27 ROM FAILURE  U27 failed checksum (test 11 is skipped).
 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. 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 WPC games, 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"
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 dieing. 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 "AJUSTMENT FAILURE".

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.

4.4.3 Relocating the battery from the System 9 MPU board

Leaking Battery

Relocating the 3xAA batteries off 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.

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.

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.

4.4.4 Relocating the battery from the System 11 MPU board

A remote battery holder installed on a System 11 MPU. The purple wire is positive.

4.4.5 Installing NVRAM instead of batteries

Like most other pinball mpu boards, you can replace the battery-backed ram with a non-volatile memory ram. Unlike most other systems, you have to jumper around a diode so the game will boot. 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 you replace U25 with the memory ram, most 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 most 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. Make sure you do not have batteries installed if you do this as they will simply short to ground, get hot, and leak. It's recommended to remove D2 and the battery holder entirely if you do this so this will never be a possibility, and write with a sharpie where the battery holder was "upgraded to NVRAM".

You need a replacement ram that can replace a 6116 or a 6264. These are becoming scarce, but there are other solutions available that use surface mount equivalents on a small circuit board that plugs into the RAM's socket. Unfortunately, U25 is soldered in on most system 11 boards and would need to be removed to replace with an NVRAM.

4.4.6 Installing a Memory Capacitor Instead of Batteries

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.

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 1N5817 blocking diode (D2) will have to be removed, and a zero ohm jumper must be installed. A scrap piece from the leg of a new resistor or diode will do the trick. By adding a jumper where the blocking diode once was, this will enable the game to charge the capacitor. 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.

4.4.7 Repairing Alkaline Corrosion

Closeup of the delicate traces under the battery holder of a System 11 MPU. Luckily, these cleaned up nicely.

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.

To begin, remove the battery holder entirely from the MPU board. Remove any socketed ICs that might get wet during this process. Use a brass brush (or other slightly soft bristle brush) to remove loose alkaline bits. Scuff the solder where the alkaline has invaded it. Wash the affected areas with a 50/50 mix of vinegar and water. Scrub the corrosion with a soft brush. Rinse with water, then rinse again with 91% or 99% isopropyl alcohol to displace the water. Let the board dry thoroughly. An air compressor works great to blow moisture from under ICs. Or, let the board sit in the sun for a few hours.

Unfortunately, often the alkaline will eat into traces that are beneath the PIAs at U41 and U42. This dictates desoldering of those 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.

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.

Use fine sand paper to expose all damaged traces. You'll be able to identify damaged traces easily as they will be discolored under the solder mask.

At the top of the board are a few "SRC" parts. These are 10 pin resistor/capacitor SIPs. These parts are no longer available. You may substitute a 9 pin bussed, 8 resistor network (4.7Kohms) at positions SRC1 - SRC5 and SRC7 - SRC9.

A closeup of alkaline damage that has crept under the solder mask (the darker traces). Eventually, this corrosion will each completely through the trace, making the board unreliable.

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.

4.4.8 Connecting a logic probe to the MPU System 9
Logic Probe connected to System 9 CPU 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". System 11
Placeholder for Logic Probe connected to System 11 CPU Board

4.4.9 Using a PC Power Supply For Bench Testing

System 9 CPU connected to a PC power supply

4.5 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 between 20-26 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).

4.6 Solenoid problems

4.6.1 A/C solenoid/flasher problems

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 "make/break" relay that supplies power to either the "A-Side" or the "C-Side". It is locate on the Auxiliary Power/Driver Board.

There are a couple ways for the A-Side/C-Side (A/C after this) circuit to fail. If the driving transistor (Q8, 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 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.

Williams System 11 Auxiliary Power/Driver Board A/C Select Relay showing "welded" 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.

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.

Another failure point 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 machines use .156 connectors in most locations.

4.6.2 Special solenoid problems

Special solenoids on system 11 games are similar to the earlier variants used on all previous Williams' boardsets. 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.

If a special solenoid actuation switch locks on, the solenoid itself will lock on as well, (hopefully) blowing the associated fuse before blowing the Tip122/2n4401/7402 grounding chain. 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 non-polarized capacitor and a 100 ohm resistor mounted across the special solenoid switches. The use of the capacitor and resistor creates what is called an RC circuit. The RC circuit is used to filter noise from the switch signal. Should a special solenoid lock on, and the switch leaves are properly gapped, the issue may be a shorted switch capacitor or resistor.

Later system 11 games do not use the special solenoids in the same way. They were changed to a cpu polled switch instead, keeping all the solenoid pulses under cpu control. You can easily tell if your game has the cpu controlled type by inspecting the activation switches on the pops and slings; if there are a primary and secondary switch installed, it is a 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.)

4.7 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.

4.7.1 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!
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

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. 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.

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.

4.7.2 Controlled Lamp Issues 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.

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.

"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.

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 presumedly 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
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:

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.

  1. Remove the backglass and open the insert to get access to CPU board connectors 1J6 (row) and 1J7 (column).
  2. Unplug connectors 1J6 and 1J7 (lower right corner of CPU board)
  3. 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
  4. Clip one end of the test jumper to 1J6 pin 1, the rightmost pin on the connector
  5. Touch the other end of the jumper to 1J7 pin 1, the rightmost pin on the connector
  6. The test lamp should flash to indicate that the column driver is working.
  7. 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.

   Pin    Wire Colors Lamp number Transistor number
Key Pin

Testing the lamp matrix rows:

Jumper connection for testing lamp matrix rows.

Use the following procedure to test the TIP102/122 transistors that drive the lamp matrix rows.

  1. Remove the backglass and open the insert to get access to CPU board connectors 1J6 (row) and 1J7 (column).
  2. Unplug connectors 1J6 and 1J7 (lower right corner of CPU board)
  3. 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
  4. Clip one end of the test jumper to 1J7 pin 1, the rightmost pin on the connector
  5. Touch the other end of the jumper to 1J6 pin 1, the rightmost pin on the connector
  6. The test lamp should flash to indicate that the column driver is working.
  7. 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.

   Pin    Wire Colors Lamp number Transistor number
Key Pin

4.8 Switch problems

4.8.1 Switch Matrix Row and Column Testing

The CPU logic for the switch matrix can be tested by simulating switch closures using a jumper wire. The following sections show the separate procedures for testing the switch matrix columns and rows. The example is on a Sys11A PinBot, but applies to all Sys11 CPU boards.

Testing the switch matrix columns:

Jumper connection for testing switch matrix columns. This picture shows a diode which is not necessary for this test.

  1. Remove the backglass and open the insert to get access to CPU board connectors 1J8 (column) and 1J10 (row).
  2. 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
  3. Unplug connectors 1J8 and 1J10
  4. Clip one end of the test jumper to 1J10 pin 9, the leftmost pin on the connector
  5. Touch the other end of the jumper to 1J8 pin 1, the rightmost pin on the connector
  6. 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.
  7. Move the jumper to 1J8 pin 2 and check the reported switch by comparing to row 1 in the switch matrix table
  8. 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.

   Pin     Wire Colors   Switch number 
Key Pin

Testing the switch matrix rows:

Jumper connection for testing switch matrix rows. This picture shows a diode which is not necessary for this test.

  1. Remove the backglass and open the insert to get access to CPU board connectors 1J8 (column) and 1J10 (row).
  2. 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
  3. Unplug connectors 1J8 and 1J10
  4. Clip one end of the test jumper to 1J8 pin 1, the rightmost pin on the connector
  5. Touch the other end of the jumper to 1J10 pin 1, the rightmost pin on the connector
  6. The display should report that switch 1 was actuated
  7. Move the jumper to 1J10 pin 2 and check the reported switch by comparing to column 1 in the switch matrix table
  8. 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.

   Pin    Wire Colors Switch number
Key Pin

4.8.2 Shorted or non-working switch column

If you found out during testing that you have one or more bad switch columns this is usually caused by a bad switch transistor at location Q42 to Q49 or a bad SRC6 1K SIP.

The type of the switch transistors changed with the system 11B CPU. System 9 to 11A use 2N3904 transistors at location Q42 to Q49 with 1K5 pre-resistors. They fail quite often after the years now. If you replace them use 2N4401s. With 11B WMS beefed up the section and used 2N5550s with 470R pre-resistors. The 2N5550 can be substituted with the 2N5551 which is the better part and also used in the HV section so you likely have a spare anyway. Before replacing the transistor check your board. Early 11Bs still have 2N3904s installed despite the manual showing otherwise.

A broken SIP usually causes more than one switch column not to work. Measure resistance between pin 1 and 2 to 8. If it's broken it's usually open after pin 3 or 4. This is a SIP with capacitors and practically NLA. Fortunately the caps are not needed because they are also mounted on the boardso 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.

A broken resistor package.

This is a picture of a broken resistor package similar to SRC6 but out of a System 11 master display. As you can see it still might look good but it's actually broken in half. So if you suspect a fault always measure resistance!

4.9 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.

4.9.1 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
Symptom Possible Cause Replacement
0V ON BOTH +100/-100 lines Check F1 1/4 Amp SB
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
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
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
* 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:

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
**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 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!

MJEInstall.png Note on installation of MJE15030/MJE15031 replacement transistors
High Voltage section with MJE15031 installed. Note the crossed legs on the left transistor.
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.

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 Sys 3-7 PSU Problems section entitled +/-100v Display HV Section of PSU, for some more detail. It also provides links to source complete HV rebuild kits which will normally cost under $10 shipped.

4.9.2 Display Panel Problems 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.


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
Replacement glass installed with glass nipple in proper location
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". If you don't want to drill or your board is simply worn out you can buy replacements from

4.10 Sound problems

4.10.1 System 9 Sound Problems Jumper Settings for a newer System 9 Speech Board
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.

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. With a alligator test lead, connect each alligator clip to 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. With a jumper installed at W10, some sounds should be heard when SW2 is pressed. If no sounds are heard, further troubleshooting must be performed.

4.10.2 System 11 Sound Problems

System 11 games are known to have some amount of hum present in the sound. To minimize this interference, make sure all boards are secured tightly to the backbox ground plain with all screws installed. This will insure the boards have a solid ground.

Another cause of hum could be an inconsistent +5 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 fix this issue. 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: Jokerz service bulletin at

4.11 Flipper problems

4.12 Pop bumper problems

5 Repair Logs and Game Specific Problems and Fixes

Did you do a repair? Log it here as a possible solution for others.

5.1 System 9

Comet Pinball Repair Log

  • Battery corrosion -- but no leaks.
  • Display Power Supply voltage problem.
  • All displays are dead.
  • Displays showing wrong numbers.

Putting displays through the display test would show players 3 and 4 counting wrong. They would count 1,2,3,1,2,3,8,9. I used a scope to test each pin on the U5 chip and found pin 12 was not putting out any signal. I replaced the U5 chip and it fixed the issue.

  • All ramps are damaged to some degree. The middle ramp is warped.

5.2 System 11

Space Station Pinball Repair Log

  • Display Power Supply voltage problem (+/- 100v = 120v/-130v).
  • Player 3 Display is out.
  • Left Dock Kicker (does not kick).
  • Shooter Lane: 2 balls at same time.
  • Top Pop Bumper (does not bump).
  • Flipper Rebuild:
    • Right Flipper is sloppy.
  • Right Dock: ball cannot escape.
  • Stuck switches (x 5).
  • Rubbers need replacing.
  • Shooter power barely/not always enough to get ball to top of playfield.
  • General Illumination (G.I.): Left side is completely out.

5.3 Using a System 6/7 Speech Board in a Comet

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 modified to use 2732 EPROMs for a Comet.

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