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Gottlieb System 1

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1 Introduction

Gottlieb® System 1 Board Set

Of the big 4 pinball makers, Gottlieb® was slowest converting from EM to Solid State, producing EMs into 1979 while Bally, Stern, and Williams had all abandoned doing so in 1977 / early 1978. The reason why Gottlieb® manufactured EMs so much longer into the solid state era is primarily due to the demand for EMs in their French market.

In the mid-70's, Gottlieb® approached several companies to manufacture their solid state board set, including National Semiconductor and Rockwell International. The bid ultimately went to Rockwell, because they could supply the circuit boards, chips, and provide the equipment necessary to program the games' OS and game code.

The Gottlieb® System 1 boardset was designed to directly replace the EM logic from the earlier machines. The main differences between the solid state and EM version of a Gottlieb® title with the same layout is the resetting of drop targets during a ball in play, the maximum bonus multiplier values, and in some cases, specific scoring values. The EM games would not reset drop target banks during a specific ball in play; the bonus multiplier was limited to a double bonus only; and similar targets or switches had lower values in some instances. All of these differences are attributed to the scoring threshold of an EM. A Gottlieb® EM game was limited to 199,990, while a solid state game could record scores up to 999,990. Consequently, System 1 games play almost exactly like an EM, just with solid state scoring. The exception is Cleopatra, which is identical in all game and scoring aspects between the EM and solid state version.

The playfield layouts were solid EM-esque designs, with rock-solid Gottlieb® mechanical parts. Unfortunately, the electronics were not as robust in terms of longevity. Major problems were exhibited with connectors, battery corrosion issues, and today's unavailability of essential, proprietary system chips.

One of the biggest issues with the System 1 platform was that it had unreliable ground connections. Unlike the other popular manufacturers of the time, Gottlieb® relied solely on connectors and daisy-chained wiring to transport the ground lines from board to board. A large ground plane was used behind the boards, but the circuit boards' grounds were not physically secured to it. Gottlieb® instead opted to use plastic standoffs to elevate and secure the boards to the backbox. Thus, if a single ground connector failed in the chain, the logic ground could fail for one or several of the circuit boards. This could potentially lead to locked on coils, relays, and / or controlled lamps. In turn, transistors and chips would fail.

2 Games

Title Date of Release Production# ROM Sound Notes
Cleopatra 11-1977 ~7300 A or 409 Chimes Also produced as a 4-player EM 'Cleopatra' and a 2-player EM 'Pyramid'
Sinbad 05-1978 12950 B Chimes Also produced as a 4-player EM 'Sinbad' and a 2-player EM 'Eye of the Tiger'
Joker Poker 08-1978 9280 C Chimes Also produced as a 4-player EM 'Joker Poker'
Close Encounters of the Third Kind 10-1978 9950 G Chime board Also produced as a 4-player EM 'Close Encounters of the Third Kind'
Dragon 10-1978 6550 D Chime board Also produced as a 4-player EM 'Dragon'
Charlie's Angels 11-1978 7950 H Chime board Also produced as a 4-player EM 'Charlie's Angels'
Solar Ride 02-1979 8800 E Chime board Also produced as a 4-player EM 'Solar Ride'
Count-Down 05-1979 9899 F Chime board Also produced as a 2-player EM 'Space Walk'
Pinball Pool 08-1979 7200 I Chime board
Totem 10-1979 6643 J Sound board J-SND ROM
The Incredible Hulk 10-1979 6150 K Sound board K-SND ROM
Genie 11-1979 6800 L Sound board L-SND ROM
Buck Rogers 01-1980 7410 N Sound board N-SND ROM
Torch 02-1980 3880 P Sound board P-SND ROM
Roller Disco 02-1980 2400 R Sound board R-SND ROM
Asteroid Annie and the Aliens 12-1980 211 S Sound board S-SND ROM Only available as a single player game

The information in the above table was provided by Click the link to view more detailed information and pictures on the IPDB of these Gottlieb® System 1 games.

Conversion kits for system 1 from other manufacturers:

  • (circa 1982) Movie (Bell Games, 4p)
  • (unknown date) Sky Warrior (IDI, 4p)
  • (circa 1982) Tiger Woman (IDI, 4p)
  • 1984 Sahara Love (Christian Automatic, 4p, production 150) [conversion of Sinbad]
  • 1986 L'Heaxagone (Christian Automatic, 4p, production 150) [original playfield design]
  • 1985 Jungle Queen (Pinball Shop, 4p) [playfield based on Gottlieb's® Jungle Queen]

Conversion kit info provided by Click the link to view more detailed information and pictures on the IPDB of these System 1 conversion games.

2.1 Physical Dimensions

Below are the physical dimensions of a Gottlieb® System 1 pinball machine. These dimensions apply to all of the System 1 games, excluding Asteroid Annie and the Aliens, Genie, and Roller Disco (the latter two are widebodies). The difference between Asteroid Annie and all other System 1 games is the backbox. The backbox used with Asteroid Annie, which does not have a flat top or hinged access door, is the same as the early System 80 games, such as Spider-Man, Panthera, and Counterforce.

3 Technical Info

3.1 Recommended Documentation

Although it is not completely necessary to fix a System 1 pinball machine, having a game specific manual can be extremely helpful, and is recommended. The game manual includes detailed information such as:

  • Lamp assignments and location
  • Switch assignments and location
  • Coil assignments
  • Game rules including 3 / 5 ball game rule differences
  • Playfield parts list including a rubber ring list and locator
  • Game specific wiring connections, lamp, and coil diagrams

The first three System 1 game manuals, (Cleopatra, Sinbad, and Joker Poker), include all of the above information, plus circuit board schematics for all circuit boards, except the tone board. Starting with Close Encounters, Gottlieb® minimized the amount of information in the game manuals. Game specific material is included, however, circuit board schematics are not. The Solid State Pinball Games Service Manual (red cover) served as a generic, supplemental manual, which complimented the game manuals. The 2nd edition service manual with the black and blue cover shown below is a revised supplemental manual. The information and scope is more extensive than the first edition (red cover) manual.

Please note that game specific connector wiring is not always game specific for the first three game manuals.

Gottlieb® Solid State Pinball Games Service Manual - 2nd Edition

If you intend to work on System 1 games on a consistent basis, a highly recommended manual to possess is the Gottlieb® Solid State Pinball Games Service Manual - 2nd Edition. This manual is full of great information including:

  • Circuit board schematics
  • Component bill of materials for circuit boards
  • Complete wiring color codes for boards and junctions (early and later codes)
  • Troubleshooting tips
  • Theory of operation
  • Detailed explanations of the System 1 components (switch matrix, displays, etc.)

3.2 The Wiring Color Code

Early on, System 1 games up until around Close Encounters used a single-color and two-color wiring code system. Starting around Close Encounters, Gottlieb® adopted a three color system. Most wiring in a Gottlieb® game used a white base color, which is the wire's insulation color, and three "striped" traces on each wire. I state most cases, because there are some wires which only used two colors - the green insulated ground lines which have a single yellow trace. Below is the Gottlieb® color chart.

0 1 2 3 4 5 6 7 8 9
Color Black Brown Red Orange Yellow Green Blue Purple Gray White

Does the color chart look familiar? Well, if you have an electronics background, it should. The Gottlieb® wire code system is the same as the resistor color coding system.

Here are some examples of the color coding system. The color wire code for switch strobe line 0 is 011. 011 would be a white insulated wire with a black trace and two brown traces, or commonly referred to as a black-brown-brown wire. The ground lines in later System 1 games are code 54. 54 would be a green insulated wire with one yellow trace.

3.3 Connector Designations

All Gottlieb® 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 or an inline wire junction, and the suffix is the connection on the board or a sequential wire junction number. When referencing a specific connector pin within a housing, a dash follows the connection number. For example, the connector pin for the slam switch signal on the CPU board is A1J6-2. The exceptions are the scoring displays. For their designation, a single digit prefix is used in front of the display board prefix for the player position of the display (ie. 3A4-J1 is the connection for the player 3 display). All in-line junctions have a common designation too. For example, the large in-line connection for the coin door is A6P1 and A6J1. The connector pin for switch return 0 on the coin door is A6J1-1 / A6P1-1.

The following boards / connections are assigned the same numbers throughout the System 1 games.

  • CPU Board - A1
  • Power Supply - A2
  • Driver Board - A3
  • Scoring Displays - A4
  • Status Display - A5
  • All Five of the "In-Line" Connections - A6
  • Sound Board - A7

3.4 Connectors

The most prevalent connector contacts used in Gottlieb® System 1 games are Molex KK .156" 2578 series contacts. Nearly all housings, the three connections on the power supply, the top housing on the driver board (A3J1), and in-line (A6) connections being the exceptions, are Molex KK single-sided card edge connectors.

Typical Gottlieb® System 1 Harness Connection Between CPU Board (A1J5) and Driver Board (A3J1)

Connection A3J1 on the driver board is a Molex KK single-sided card edge connector, however, it has mounting "ears" on either side. This type of housing was used, so that the A1J5 / A3J1 harness between the CPU board and driver board could not be installed upside down. Unfortunately, this particular housing with ears is no longer available. The power supply uses three different Molex KK .156" crimp terminal housings for header pin connections. All A6 in-line connectors use a combination of Molex .093" plug / receptacle housings with appropriate Molex .093" male / female crimp contacts. Please refer to the table below for the type and connector count of each System 1 board connection.

Connection Location Preferred contact type Housing Part # Housing contact total Total contacts used
A1J1 CPU Board - left Molex .156" edge 09-01-6061 6 5
A1J2 CPU Board - right top Molex .156" edge 09-01-6191 19 16
A1J3 CPU Board - right bottom Molex .156" edge 09-01-6211 21 18
A1J4 CPU Board - bottom right Not used Not used Not used 0
A1J5 CPU Board - bottom middle Molex .156" edge 09-01-6241 24 23
A1J6 CPU Board - bottom left Molex .156" edge 09-01-6091 9 7†
A1J7 CPU Board - bottom left Molex .156" edge 09-01-7171 17 15†
A2J1 Power supply - bottom Molex .156" trifurcon 09-50-8071 7 7
A2J2 Power supply - top Molex .156" trifurcon 09-50-8061 6 5
A2J3 Power supply - right Molex .156" trifurcon 09-50-8081 8 5
A3J1 Driver board - top Molex .156" edge 09-01-6241 24 23
A3J2 Driver board - bottom right Molex .156" edge 09-01-6071 7 5
A3J3 Driver board - bottom middle Molex .156" edge 09-01-6211 21 21†
A3J4 Driver board - bottom middle Molex .156" edge 09-01-6083 8 6†
A3J5 Driver board - bottom left Molex .156" edge 09-01-6191 19 19†
A4J1 Scoring displays - bottom Molex .156" edge 09-01-6191 19 18
A5J1 Status display - bottom Molex .156" edge 09-01-6191 19 19
A6J1 / A6P1 In-Line - coin door Molex .093" male / female 03-09-1157 / 03-09-2159 15 14
A6J2 / A6P2 In-Line - chimes / knocker Molex .093" male / female 03-09-1064 / 03-09-2062 6 6
A6J3 / A6P3 In-Line - backbox Molex .093" male / female 03-09-1157 / 03-09-2159 15 15
A6J4 / A6P4 In-Line - playfield / bottom board Molex .093" male / female 03-09-1094 / 03-09-2092 9 9
A6J5 / A6P5 In-Line - playfield / bottom board Molex .093" male / female 03-09-1126 / 03-09-2121 12 12
A7J1 Tone board - bottom Molex .156" edge 09-01-6091 9 6
A7J1 Sound board - left Molex .156" edge 09-01-6121 12 9

†Note: total amount can differ from game to game

3.5 Switch Matrix

Gottlieb® System 1 Switch Matrix

The Gottlieb® System 1 switch matrix consists of a maximum of 40 switches. There are a total of 5 switch strobes, (starting with 0, ending with 4), and 8 switch returns, (starting with 0, ending with 7). The first number of every switch is its return number, while the second number is the switch's strobe number. An example would be switch 54. Switch 54 is located on return 5 and strobe 4 of the switch matrix. Due to the switch numbering system used, consecutive switch numbers are not used from return to return. In other words, when the last switch numbered in the last strobe of a particular return, the next switch number in the next switch return is not the consecutive number following the last used number. For example, the last switch number in switch return 0 is 04. The first switch number in switch return 1 is not 05. It is switch 10.

Likewise, not every switch in the matrix is used on every System 1 game.

Connections for the switches originate from the two edge connectors located at the lower left bottom of the CPU board. Connector A1J6 is used for all the switches on the coin door, the ball roll tilt (which is the second slam switch), and in some cases, the pendulum tilt. While connector A1J7 is for all of the switches on the playfield.

Strobe 0

(A1J7-2 / A1J6-8)

Strobe 1

(A1J6-3 / A1J6-4)

Strobe 2

(A1J7-4 / A1J6-5)

Strobe 3

(A1J7-7 / A1J6-6)

Strobe 4


Return 0 (A1J7-12 / A1J6-3)
Return 1 (A1J7-13)
Return 2 (A1J7-14)
Return 3 (A1J7-17) 30
Return 4 (A1J7-16)
Return 5 (A1J7-15)
Return 6 (A1J7-11)
Return 7 (A1J7-10)

Gottlieb® System 1 Diode Board

Unlike most other manufacturers, Gottlieb® isolated each switch with a 1N270 Germanium diode versus a 1N4004 or 1N4148 silicon diode. The use of a silicon diode will cause the switch matrix to function incorrectly. Furthermore, Gottlieb® attached the diodes to central location diode boards for each switch return versus attaching a diode to the switch itself. In some cases, like shown in the pic, the diode boards are stacked on top of one another. This can make testing the diodes on the lower diode board somewhat difficult. Although, it is not too common for the switch diodes to fail.

It should be noted that the switches on return 0 are always the same for every System 1 game. The following switches have the same designations:

  • Switch 00 = Test Switch
  • Switch 01 = Coin Switch #1
  • Switch 02 = Coin Switch #2
  • Switch 03 = Credit (Start) Button
  • Switch 04 = Tilt Switches (pendulum tilt on the tilt board and the weighted tilt on the playfield)

Even though the switch matrix is being discussed here, it should also be noted that there are three switches used in System 1 games, which are not on the switch matrix. These three switches are the two slam switches and the outhole switch. Each game has two slam switches. The first is a weighted, normally closed switch on the coin door. The second is a normally closed switch, located at the end of the ball roll tilt cage. Neither the slam switches nor the outhole switch have a switch number designation.

3.5.1 Setting up a Game for Free Play

Early Gottileb® solid state pinball machines, prior to 1990, did not have a free play option available within the game settings. With this simple modification, a game can be set up for free play. First, identify the diode strip in the bottom of the cabinet. Once the diode strip is found, locate the credit button and coin switch strobe line wires. The wires will be located on the left of the diode strip - the non-banded side of the diodes. Below is a list of the wires.

Credit button wire - Green-White or Brown-Yellow-Yellow

1st coin switch wire - Orange-White or Brown-Red-Red

2nd coin switch wire - Brown-White or Brown-Orange-Orange

Gottlieb® System 1 Transformer Board. Note the location of the cabinet switch matrix 1N270 diodes.
Gottlieb® System 1 "Free Play" Jumper on a Sinbad (yellow wire with red tracer)

Solder a small lead wire from the credit button wire to any of the coin switch wires. Make certain that the diode, credit button wire, and coin switch wire are still soldered securely to the diode strip terminal when finished. If soldering is not an option, use a small alligator clip test lead instead. Now, when the credit button is pressed, a credit will be incremented and decremented. A game can be easily started without the need to open the coin door to trip the coin switches anymore.

3.6 Transformer Panel

A Typical Gottlieb® System 1 Transformer Panel

3.7 The System 1 Board Set

Gottlieb® System 1 Board Diagram

3.8 Power Supply

Gottlieb® System 1 Power Supply - Front
Gottlieb® System 1 Power Supply - Back

The -12 volt regulator (marked LIC1 on the schematic) which is a type 7912, is mounted at the top edge of the board and is bolted to the metal frame with an insulated plastic insert. At the very bottom edge of the board and also bolted to the frame with an insulated plastic insert is transistor Q2 (a type TIP31C) which regulates the +60 volts to the displays. There should be insulating mica wafers between each of these transistors and the metal frame. Silicone heat sink grease will need to be applied to both sides of the mica insulator. Attached to the large "L" bracket metal frame is transistor Q1 (original is type PMD-12K-40 but you can sub an NTE247) which is the +5 volt regulator. This transistor is also insulated with a mica wafer and silicone heat sink grease.

Gottlieb® System 1 Power Supply with heat sink / mounting plate removed - back

3.9 CPU Board

Gottlieb® System 1 CPU Board - Version 1 (-001) (Pinball Pool Masked Game ROM Installed)
Gottlieb® System 1 CPU Board - Version 2 (-011)
Gottlieb® System 1 CPU Board - Version 3 (-021)
Gottlieb® System 1 CPU Board - Version 4 (-031)

The Gottlieb® System 1 CPU board is responsible for controlling all switches, displays, lamps, relays, and solenoids. The lamps, relays, and solenoids are ultimately driven by the driver board, however, the CPU board actually controls these items.

3.10 Driver Board

Gottlieb® System 1 Driver Board

The System 1 Driver board is responsible for all CPU controlled lamps, relays, and solenoids in the game. The CPU controls the driver board operation via an interface between A1J5 on the CPU and A3J1 on the driver board.

Gottlieb® did not implement a lamp matrix as some other manufacturers did. Therefore, diodes to isolate each controlled lamp are not necessary. To control the total of 36 lamps, the interface provides device select signals for each of the 9 Quad-D Flip-Flop 74175 chips on the driver board, and 4 bits of data that is loaded (or "clocked") into a particular 74175 via the aforementioned device selects. Each lamp is driven discretely by a particular output of a particular 74175, which in turn drives either an MPS-A13 (32 total) or an MPS-U45 (4 used for lamps) transistor. There are 2 dedicated lamp driven circuits used for the tilt and game over relays on all System 1 games. The transistors for the game over (Q) and tilt (T) relays are always Q1 and Q2 respectively. Equally, there are 2 dedicated lamp circuits for the high game to date and both shoot again lamps,(one in the backbox and one on the playfield). The transistors for these circuits are always Q3 and Q4 respectively.

There is a maximum of 8 solenoids that the driver board can control. Solenoid transistors receive a pulsed signal from the CPU board, which is applied to the associated transistor base. In turn, the solenoid turns on momentarily. 7 of the 8 solenoid transistors used are a 2N6043. TIP102 transistors are a viable, cheaper replacement for the 2N6043. The 8th transistor is a actually a pair of transistors consisting of an MPS-U45 and a 2N3055. There are 5 dedicated controlled solenoids used on all System 1 games. A table of all the solenoids, their associated transistors, and whether or not they are dedicated is listed below.

Sol. # Sol. Name Transistor # Dedicated (Y / N)
1 Outhole Q32 Y
2 Knocker Q25 Y
3 10's Chime Q26 Y
4 100's Chime Q27 Y
5 1000's Chime Q28 Y
6 Solenoid 6 Q31 N
7 Solenoid 7 Q30 N
8 Typically drop target reset Q29 & Q45 N

Remote Transistor Mounted Under Playfield

Starting with Joker Poker, Gottlieb® went beyond the threshold of controlled solenoids with 9 total. To accomplish this, they used an MPS-A13 lamp transistor to "pre-drive" a 2N5875 transistor remotely located under the playfield. This practice continued on other System 1 games. See the Remote Mounted Transistor section for a complete listing of games.

Early System 1 Driver Board w/o Blocking Diodes
Gottlieb® System 1 Driver Board w/ Blocking Diodes

There are two variations of the driver board used in System 1 games. Either board will work in any of the System games. The main difference between the two versions of driver boards is the addition of isolation / blocking diodes. These blocking diodes were added to the transistor signal lines from the CPU board. The change occurred during the run of Close Encounters machines. Games prior to Close Encounters and early runs of the same game will not have the blocking diodes added. Late runs of Close Encounters, and any game after will have the blocking diodes. Keep in mind, it is very common to find a board in a game, which was not originally from that particular game. So, don't rely on your Totem or Genie having a driver board with blocking diodes without actually physically looking at the boards installed first.

Instructions to retrofit blocking diodes can be found here.

3.11 Sound

Gottlieb® System 1 Chime Box

The first three System 1 games: Cleopatra, Sinbad, and Joker Poker all used EM style chimes. A chime for 10 points, 100 points, and 1000 points scored during a game would sound off accordingly. The chime unit is the same one used on Gottlieb electromechanical games with two exceptions: the coils used are different, and the dioes on the coils must be used, if in a System 1 game.

Gottlieb® System 1 Chime Board (Tone Board)

Starting with Close Encounters of the Third Kind through Pinball Pool, the first generation sound board is used. This is a very rudimentary sound board, which is only capable of generating a total of three beep and boop tones. The tone board uses the same three solenoid drive transistors for input as the chime units, which extremely limits the amount of output sounds. The tone board and chime units are interchangeable, and the tone board often gets swapped for the better sounding chimes.

Gottlieb® System 1 Multi-Mode Sound Board

Games from Totem to Asteroid Annie used the Multi-Mode sound board, also referred to as the "2nd generation" sound board. This is the first sound board created by Gottlieb®, which has its own on board CPU chip. The same three solenoid drive transistors used by chime units and tone boards is used by the 2nd generation sound board. Two additional input signals, tilt and game over, are used with this board, increasing its input signals from three to five total. Still, the 2nd generation sound board is somewhat limited, mainly due to the minimal amount of input line signals.

3.12 Display Boards

"What's new is blue!", touted the Cleopatra flyer regarding the blue Futaba displays used in Gottlieb's® first solid state venture. Generally speaking, the System 1 displays are a fairly reliable, long-lasting display. These vacuum fluorescent displays (VFD) have a tendency to outlast the plasma gas displays, which were commonly used by Williams, Bally, and Stern.

Gottlieb® 6 Digit Display
Gottlieb® 4 Digit Display

Two different styles of displays were used throughout all System 1 games - four 6 digit displays for the player's score and one 4 digit display for game status. There were two different 6 digit displays used during the System 1 era, however, either style will work in any game, and can be mixed among styles. The display boards and glasses were the same, but the chip sets which were used differed. One style was based on Sprague UDN6118A chips, while the other was based on Dionics DI513 chips.

Three distinct voltages are needed for either the 6 digit or 4 digit displays to function properly.
6 Digit Display

  • +60vdc
  • +8vdc
  • 5vac

4 Digit Display

  • +42vdc
  • +4vdc
  • 3vac

3.12.1 Display Test

Gottlieb® System 1 display tests are steps 11 and 12 of the diagnostics. Step 11 tests player 1 and 3, cycling 000000, 111111, 222222, etc. on each display. Step 12 tests player 2 and 4 displays in the same way. The credit/match display, unlike System 80 display test, is not tested during either System 1 display test. That is, the digit sequences are not displayed on the credit/match display during test steps 11 and 12.

3.13 Solenoids and Relays

All System 1 solenoids and relays are powered by a +24VDC solenoid bus. Each game has CPU controlled solenoids and "non-controlled" solenoids consisting of the same types of solenoids:

  • flippers
  • pop bumpers
  • kicking rubbers (slingshots)

The CPU controlled solenoids are ultimately driven via the driver board, while the non-controlled solenoids are essentially "live" at the start of a game. The conditions which make them live are a normally closed switch on the tilt relay and a normally open switch on the game over relay. Once the game over relay locks in, all that is necessary for these solenoids to activate is an associated playfield switch to close, or in the case of the flippers, pressing the appropriate flipper button. All of the non-controlled solenoids have switches with tungsten contacts, which supply power to the solenoids. It is safe to file or burnish these types of switches. However, there are secondary "gold flashed" scoring switches on the pop bumpers and slingshots, which should not be filed or burnished.

Gottlieb® System 1 Game Over and Tilt Relays

System 1 games employ the use of "open cage" relays. Relays relevant to every game are the tilt relay, game over relay, and coin lockout relay. There are seldom used extra relays on some games such as the vari-target reset too. The tilt, game over, and var-target relays are all controlled by the driver board. But, the coin lockout relay is energized as soon as the game is turned on.

Whether or not a solenoid or relay is controlled by the CPU board, all solenoids and relays should have 1N4004 diodes installed.

Below is a list of solenoids / coils used in System 1 games.

Sol. # Common Usage Wire Gauge Windings Resistance
A-1496 Pop bumper 23 635 2.95
A-5194 Kicker (Slingshot), Pop Bumper 24 780 4.5
A-5195 Outhole (early), Knocker, Kickout Hole 26 1305 12.3
A-16570 Outhole (later), Kickout Hole 27 1450 15.5
A-16890 Game over relay, Tilt relay, coin lock out 35 4000 231.0
A-17564 Vari-Target Reset
A-17875 Flipper 24 / 31 560 / 1100 2.8 / 40.0
A-17876 Chimes 28 1750 24
A-18102 3 or 7 (2 used) bank drop target reset 24 1430 9.0
A-18318 4 bank drop target reset 24 1130 6.7
A-17891 5 bank drop target reset, Roto 22 850 3.35

3.13.1 Solenoid and Relay Test

+++describe built in game test diagnostics+++

3.14 Flippers

++++Add more pics of individual parts of the flipper assy. within text and a parts explosion++++

Gottlieb® System 1 Flipper Assy.

The System 1 3" flipper mechanism first appeared in later Gottlieb® electro-mechanical games. Starting with Buccaneer in 1976, this flipper style assembly was used throughout all of the System 1 and System 80/80A/80B games, except for the last System 80B game, Bone Busters, Inc. in 1989. These flippers are referred to as "fat boy" or "brick" flippers, however, there really isn't a distinct nickname for them which stuck.

Where the System 1 flipper mechanism lacks in overall smoothness, it makes up for this in durability and reliability. The System 1 flipper mechanism is incredibly hardy, and if cleaned and assembled correctly, it will work reliably for a relatively long time. Hence, operators who actually operated System 1 games loved this style of flipper, mainly because they rarely break.

The flipper coil used is serial-wound, dual coil with high power and hold winding. Only a single diode is used with the flipper coil, because the windings are wound in series. The only major difference between EM, System 1, and System 80/80A/80B flipper assemblies is the flipper coil used. EM games used A-5141 coils, while System 1 games used the standard A-17875 coil, which is stronger. Some System 80/80A/80B games used A-17875 coils, but starting around Black Hole, games were using the even stronger A-20095 "super flipper" coil. An intermediate strength flipper coil, the A-24161 coil, was occasionally used starting with System 80A games.

Power to the coil's windings is transferred via an EOS switch, and flippers are activated by a cabinet switch which completes the coil's circuit to ground. Operation of these flippers is similar to any other pinball manufacturer. Although, there are several physical attributes which make them different.

  1. A bakelite flipper link was no longer used with this style. Instead, a molded one-piece link and plunger were used. The link and plunger are technically two separate pieces held together via a roll pin, but the two pieces are not available as two separate parts.
  2. A dual (upper and lower) flipper bushing, (Gottlieb® refers to them as bearings), system was used. This setup is unique to this style of flipper system, because every other manufacturer and Gottlieb® flippers previously and after only used a single flipper bushing.
  3. The normally closed flipper EOS switch uses a plastic, triangular actuator to open the EOS switch. This plastic actuator is secured within the EOS switch stack.

The only major weakness to this flipper design is how the EOS switch is actuated. The EOS switch is opened via the flipper crank / pawl assembly, and it's a metal-on-metal contact point. Even though the thicker than normal metal switch leaf where contact is made on the EOS switch, the flipper crank / pawl can potentially wear a hole in this leaf over time. Gottlieb® did rectify this potential issue in the late '80s, (around the production of TX-Sector), by offered a kit to modify the assembly. The new style crank / pawl had an added a plastic roller, which made contact with the EOS switch instead of the pointed edge of the flipper crank / pawl. The EOS switch was attached to a bracket which attached to the flipper plate's old EOS switch bracket. This was done to compensate for the difference in spacing the roller created. The flipper mechanism was now even better, but in home use this modification may be a bit of overkill.

The only design change the flipper mechanism underwent, during the course of the System 1 platform, was a change in the flipper link. The molded plastic flipper link used on earlier System 1 games had a "tail", which protruded through a hole in the bearing bracket. It is assumed that this "tail" was used to center the motion of the flipper plunger and link, and the "tail" does effectively do this. However, there is one drawback. As the flippers wear with age, the tail can start "dragging" through the hole. In turn, this can create weak flipper action. It is suggested that if the flipper mechanism still has a tail present on the flipper link to cut or grind the tail off.

The majority of this discussion has focused on the 3" System 1 flipper assembly. Not to be forgotten, some System 1 games, such as Joker Poker, Count-Down, and Genie, used secondary 2" flippers. The 2" System 1 flipper design is the same mechanism as electro-mechanical Gottlieb® games. The only difference is the coil used. EM games used an A-5141 coil, while System 1 games used an A-17875 coil.

3.15 Pop Bumpers

Anatomy of a System 1 Pop Bumper
System 1 Pop Bumper

View of Pop Bumper Switches

Pop bumpers of System 1 are not operated from any circuit boards. When the bumper skirt stem moves and closes the spoon switch, the high current contacts directly power the pop bumper for as long as the switch remains closed. If by chance the spoon switch gets stuck closed, the coil will remain energized and burn up. There are actually two sets of switches that make up the pop bumper switch assembly. The spoon switch has very heavy duty tungsten contacts to switch the high current to the coil. These contacts can corrode/pit over time and cause weak/poor performance of the pop bumper due to low current passing to the coil. The second set of switches which are the farthest away from the spoon switch are the low current "scoring" switch. This switch is connected to the cpu board and when closed, scores the points that the bumper is worth. The contacts of the scoring switch are usually gold flashed. Sometimes the long blade of the scoring switch will break off which will then prevent scoring any points when the pop bumper is activated. This long blade is moved open and closed by the action of the bakelite yoke moving up and down.

3.16 Drop Targets

This is a stub

3.17 Vari-Target

Vari-Target as viewed from Top of Playfield (Totem)
Vari-Target as viewed from Under Playfield (Totem)

3.18 Accessing Bookkeeping and Diagnostics

Placeholder for Sys 1 coin door test button

3.19 Lamps

++describe lack of lamp matrix, driver board / CPU control of lamps, etc.++

3.19.1 Lamp Test

+++describe built in lamp test diagnostics+++

3.20 Rubber Ring Chart

Although the Gottlieb® System 1 game manuals do list the location and part numbers for rubber rings used, they fail to list the actual rubber ring size. Below is a handy chart, which lists the Gottlieb® rubber OEM number and its size.

Gottlieb® # Description
A-14793 23/64" White Mini-Post
A-15705 27/64" White Mini-Post
A-10217 5/16" White Ring
A-17493 7/16" White Ring
A-10218 3/4" White Ring
A-10219 1" White Ring
A-10220 1-1/2" White Ring
A-10221 2" White Ring
A-10222 2-1/2" White Ring
A-10223 3" White Ring
A-10224 3-1/2" White Ring
A-10225 4" White Ring
A-10226 5" White Ring
A-13151 3/8 x 1-1/2" Standard Red Flipper
A-13149 3/8 x 1" - Small Beaded Red Flipper
A-1344 Rebound Rubber
1872 Shooter Tip

4 Problems and Solutions

4.1 Connectors

Connectors, connectors, connectors!!! Since the Gottlieb® System 1 boardset primarily relies on Molex connectors to pass data and voltages from board to board, the connectors should be addressed first. Before even attempting to turn a Gottlieb® System 1 game on for the first time, worn or corroded edge connector contacts must be replaced. Cleaning or burnishing connector contacts is not a viable option to ensure a game's reliability.

Poor connector contacts are the number one reason why System 1 games do not function properly. Poor or missing connector contacts have a cascading effect too. The end results of bad connector contacts can be, but are not limited to:

  • voltages which mysteriously disappear and reappear
  • increased resistance
  • specific switches not functioning
  • lamps locking on
  • lamps not turning on
  • displays not properly functioning
  • coils not turning on
  • coils locking on
  • CPU boards not booting, booting sporadically, or randomly resetting
  • driver boards not functioning or functioning sporadically

So, it is very important that the connector contacts are shiny, have proper spring tension, and are properly crimped for the over all reliability of the game. Random, flaky issues which happen either sporadically or all the time are attributed to poor connector contacts in nearly every case.

4.1.1 Replacing (Repinning) System 1 Connectors

Replacing connectors in a pinball machine somehow adopted the term repinning. Repinning a System 1 edge connector housing is probably the most difficult. On a scale of 1 to 10 (1 being the easiest to do, 10 being the most difficult) compared to all other makes and platforms made, System 1 edge connector replacement is about an 8. Provided the ear inside the plastic housing does not get sheared off, System 1 edge connector housings are reusable. Below are the steps to remove the connector from its housing.

System 1 connector housings are primarily "single-sided" edge connectors. The exceptions are the three connectors used on the power supply. To remove pins from these connector housings, you need a pricey yet effective tool called a Molex contact extraction tool, (commonly referred to as a Molex extractor). The Molex part number for the extractor is 11-03-0016, and can be purchased from Great Plains Electronics or other electronics vendors. Slide the extractor behind the pin to release the "locking tab" that holds the pin in. Firmly grip the wire and pull the pin out of the connector.

4.1.2 The CPU / Driver Board Interconnect Harness

The A1-J5 / A3-J1 Interconnect Harness

There are 23 discrete signals which pass from the CPU board to the driver board via this connection. Two of the connectors pass ground and +5v logic to the driver board, while the remaining signals are for lamp, relay, and solenoid control. It is extremely important to have solid connectors installed in the CPU / Driver board interconnect harness. Without decent connections, lamps, coils, and relays can either lock on or not turn on at all.

Repinning both sides of the interconnect housings is the solution to reliable game function. If repinning is not an option, several vendors sell replacement new harnesses. When buying a replacement, use some caution. The original factory harness uses single-sided Molex edge connections. There are some replacement harnesses being sold with double-sided edge connection housings. It is easy to identify these housings, as they are black in color versus the "natural" color of all the other housings used in the game. These types of harnesses do work, but there is one caveat. They are not specifically built to fit the System 1 edge connections on the CPU or driver board, and are a fraction larger than the board edges fingers they are installed on. Hence, there is some lateral (side to side) movement in the connections at both A1-J5 and A3-J1. Because of this "slop", the housing connectors can cross signals to adjacent edge fingers. The end result is relays, lamps, or coils which do not turn on at all or never turn off.

4.2 Ground Updates

Gottlieb® System 1 games are notorious for having poor ground connections. As mentioned at the introduction of this System 1 guide, ground problems are one of the biggest issues with the System 1 platform. Poor ground connections are the number two reason for unreliable System 1 games. Unlike the other popular manufacturers of the time, Gottlieb® relied solely on connectors and daisy-chained wiring to transport the ground lines from board to board. A large ground plane was used behind the boards, but the circuit boards' grounds were not physically secured to it. Gottlieb® opted to use plastic standoffs to elevate and secure the boards to the backbox instead. Thus, if a single ground connector failed in the chain, the logic ground could fail for one or several of the circuit boards. This could potentially lead to erratic behavior with locked on coils, relays, and / or controlled lamps. In turn, transistors and chips would fail.

Chiefly due to age and / or alkaline battery damage, the connectors carrying the ground lines would fail. Connectors become fatigued losing their tensile strength against the edge finger surface of the board. Thus, the ground connections would become compromised. Equally, if battery damage was present due to an aged, leaky battery, the connectors would corrode, and either have too much resistance, or completely break. Replacing the failed connectors is always a great start, and highly recommended. However, there are additional procedures to keep from the ground being lost at each board. Once the ground lines are added to the circuit boards, Gottlieb® System 1 games are one step closer to being as reliable or more reliable than the other pinball manufactures' games from the same era.

Ground tie point in backbox for CPU and driver boards

4.2.1 Additional Ground - Power Supply

Ground added to System 1 power supply on 12v filtering cap

If you happen to be one of the lucky few, where the power supply does not have to be disassembled for repair, an additional ground line can be soldered to the negative leg of +12VDC filtering capacitor. The filtering capacitor is the large axial capacitor, which is oriented horizontally on bottom of power supply board.

Ground added to System 1 power supply on back

If component level work has to be performed on the power supply, the circuit board will have to be physically removed from the heat sink / mounting plate. While the board is removed, an additional ground line can be added to the ground on the backside of the power supply board. This line can then be secured to the pinball machine's backbox via one of the three sheet metal screws used to mount the power supply's metal mounting bracket.

For a cleaner look, the additional ground line could be soldered to the ground on the backside of the board, and then soldered to one of the two threaded standoffs used to secure the power supply board to the heat sink / mounting plate. Make certain to solder to one of the outer standoffs which have no traces surrounding them. Do not tie the additional ground line to either standoff used to secure Q1 to the heat sink / board.

Regardless of the method chosen above, the power supply will have a more solid ground connection, once the additional work has been completed.

4.2.2 Additional Ground - CPU Board

Ground added to System 1 CPU board at A1J4-1 - front

Ground added to System 1 CPU board at A1J4-1 - back

Alternate location for added ground at negative leads of capacitors C16 & C17

Ground added to Ni-Wumpf System 1 CPU board at A1J2-3,4 - back

There really isn't a good place on the front of a Ni-Wumpf CPU board to connect to ground. The best choice is to go to the back of the board and find the large ground trace that connects to J2 pins 3 & 4. Find a nice clear spot on this ground trace and scrape away a section of the mask covering the trace. Solder a wire to this section of the trace, crimp a fork connector to the other end of the wire, and connect the wire to an existing screw on the metal rail the board is mounted to. This will connect the board's ground to the ground plane in the back box.

4.2.3 Additional Ground - Driver Board

Ground Added to System 1 Driver Board

The best place to add an additional ground on the driver board is the negative side of capacitor C1. The capacitor is marked with a "+" on the top side. Using 18ga stranded wire, the new line must be soldered to the bottom of C1, which is the negative side. This coincidentally happens to be the same place the driver board receives ground from the CPU board via the interconnect harness (A1J5 pin 24 to A3J1 pin 22). On the other side of the newly added ground wire, either a solderless crimp eyelet or solderless crimp fork should be added. Once the driver board is reinstalled into the game, mechanically secure the eyelet or fork with one of the screws which hold the metal board rails. Just ensure the screw used to hold the added ground line has continuity to ground.

Ground Added to Ni-Wumpf System 1 Driver Board

The Ni-Wumpf driver board has a spot on the upper left corner of the board labelled "H2" that seems to be intended to be used to install a screw terminal to connect to ground on the board. If you don't have a screw terminal handy, you can just solder a wire into one of the 4 mount points for H2, crimp a fork connector onto the other end of the wire, and attach it to one of the screws that hold the metal board rails onto the metal ground plane in the back box.

4.2.4 Additional Ground - Sound Boards

Ground Added to System 1 Multi-Mode Sound Board

There is a fairly large area where an additional ground can be soldered to the Multi-Mode sound board. This area can easily be identified on the back of the board. One of the nuts used to fasten the 5v voltage regulator to the board is secured to the large ground plane on the board.

Once attached to the sound board, run the additional ground lead directly to the ground plate located on the transformer board. It is a good idea to splice a "quick connect" in the added ground line, so the sound board can easily be removed for service if necessary.

4.3 Power Problems

4.3.1 The Upside Down A2J1 Power Supply Connection

Gottlieb® System 1 power supply with connection A2J1 highlighted

The first power problem is more of a word of caution than anything else. The issue stems from the power input to the power supply, which is located at the bottom connection of the power supply. A2J1 is a 7 pin connection, which is fed power directly from the transformer panel. The problem is that the female connector is not keyed. Since the connector is not keyed, there is a slight risk of installing the connector upside down. The connector would have to be installed with brute force though, as there is a ramp on the bottom of the header pins. On most games, Gottlieb® affixed an orange sticker to this connector, stating THIS SIDE DOWN. However, over time due to heat, moisture, and other circumstances, the warning sticker is typically missing.

If you have to exert force to put the the connector on at A1J2, it is being installed upside down.

4.4 MPU Boot Issues

4.4.1 Battery Leakage and Corrosion

Like most any other pinball machine manufactured, Gottlieb® System 1 games use batteries to supply power to the non-volatile RAM memory. Certain game settings, high score thresholds (including high score to date), audit information, and bookkeeping information are all options which are saved when the game is powered off. And unless some kind soul, who worked on your machine before, either removed the battery and mounted it remotely away from circuit boards, or just plain removed the battery, there will be some variety of a 3.6v Nickel Cadmium (NiCad) rechargeable battery soldered onto your CPU board.

So, what's so bad about having a battery on the CPU board? Well, nothing really, unless it becomes forgotten, and most cases it does. While you let your pinball machine sit unplayed for weeks, months, or even years at a time, the battery remains perched on the circuit board like a ticking time bomb. I'm not saying the battery is going to blow up, although some replacement non-rechargeable batteries could overheat and / or explode if not correctly installed. The battery is like a ticking time bomb, because it is a threat to the overall health of the electronic components, traces, and connectors attached to your CPU board.

Now that I have your attention regarding the whole battery thing, let's talk about the battery, and what happens. . .WHEN GOOD BATTERIES GO BAD. It's not that some batteries were born on the wrong side of the tracks or anything. Any good battery can go bad without much warning. It takes time, but eventually you will find out that your battery has stepped over to the "dark side". That particular time is typically when you turn your game on, the lights come on, and that's it. The displays don't light up, the start up sounds don't resonant, and the silver ball stays in its comfy little home. Nada, nothing, no signs of anything resembling a fun game of pinball. UH-OH! So what happened? The pinball machine worked fine the last time you played it.

Well, while you were out having a good time and enjoying life, the poor, aged, neglected battery decided to wreak havoc all over your CPU board. The CPU battery spewing its guts all over the place is akin to the batteries in the flashlight you haven't turned on since the last power outage over a year or two ago. You go to turn on the flashlight when you need it most, and find out there's something wrong. So being the curious type, you open the flashlight's battery compartment only to find some kind of funk leaking all over, or the batteries now look like they need a shave. The resolution to the flashlight scenario is pretty simple. Throw it away, and buy a new one. Your CPU board problem can be resolved the same way, except it will be a lot more costly, and is not recommended to just pitch it in the trash. If the battery damage to the CPU board is not overly extensive, attempt to repair it.

Gottlieb® System 1 CPU with a Data Sentry Ni-Cad Battery still installed NOTE: U5 spider chip was removed from this board.

It's unfortunate, but every battery has a life expectancy. The only silver lining is that some of the Ni-Cad batteries installed on System 1 CPU boards can last longer than others. Probably the worst offender of board destruction is the Data Sentry pack, and its associated knock-offs. This battery comes in a black rectangular plastic package, and is typically found on newer generation CPU boards.

One of the two typical Ni-Cad batteries found on a System 1 CPU board

The other common battery style is a what looks like an AA battery on steroids. This style is a fraction longer and fatter than an AA battery's physical form, and has two soldered leads on either end. These are normally held by two clips, which are screwed to the CPU board. Although these types of batteries are found on early generation CPU boards, there are some cases where this style of battery is the chosen replacement. Even though a newer battery of this type may be installed on the board, the same results of battery seepage can occur. The only benefit of this type of battery is that it can be carefully cut (in most cases) from the board without removing the board from your game. This is a plus if no battery damage has occurred.

So what happens if you don't heed the above warnings, and the battery is allowed to remain on the board? Plain and simple - THE BATTERY WILL LEAK! It's only a matter of time. Equally, the path of destruction is uncertain. Batteries don't just leak - they release caustic, alkaline fumes. These fumes attack wherever there is copper, even tinned or soldered copper. The end results are:

  • solder joints which become green or gray and crusty as opposed to a shiny silver
  • connectors which are also now green / gray or potentially broken
  • solder mask, the green covering the electronic traces, on the circuit board has either flaked off or is partially delaminating (lifting)
  • insulated wire becomes less flexible and brittle
  • sometimes the alkaline "cloud" in the game's backbox can even effect the upper portion of driver board.

Particular areas of a System 1 CPU which are susceptible to alkaline damage are:

  • Edge connector fingers at A1J6 and A1J7, in worse cases, A1J5. The associated edge connectors inside the housings will be effected in part or in whole too.
  • Solder vias from A1J7 to the component side of the CPU board
  • The following chips: Z28, Z8, possibly Z9 and Z6, and in worst cases, the U5 spider chip located just above and to the left of the battery. The majority of chips involved are associated with the switch matrix with the exception of Z6 used for some solenoids.
  • Resistors R33 - R36 and R37 - R39, in worse cases R45 - R50
  • Other components above the top of the battery.

If the spider chip U5 took a substantial hit, writing off the CPU board for parts only may be the best approach. Although it can be a tedious repair, any of the other components mentioned above are readily available, and can be acquired for replacement.

Electronic components, related solder joints, circuit board traces, connectors, and even insulated wire will become unreliable and/or fail. In all cases, the effected components are less conductive.

The only silver lining with System 1 battery alkaline damage is that in most cases the CPU board will still boot. That's not saying there won't be issues with the switches not reacting or solenoids locking on, but the potential for the board to boot is there. So, if you're curious whether the board is worth repairing, first see if the board boots with only A1J1 (power) and A1J2 / A1J3 (displays) connected. This is of course provided that there is no alkaline damage on any of these three connections. The connections may have to be repinned prior to an attempt of booting the board. Likewise, the slam switches will have to be disabled on the CPU board.

If battery damage has occurred, the related parts must now be replaced. Attempting to remove soldered through components on the circuit board is now even more of a task. The green / gray dull solder does not transfer heat well. Battery damaged solder does not flow like clean solder. Also, crimped connectors are more difficult to remove from their housings, and have a tendency to break before they can be successfully pulled out.

After all the effected electronic components are removed, the board must be treated. This process starts by sanding the traces and solder pads until shiny copper is exposed. It is worth mentioning that a battery damaged board can be treated by bead blasting instead of sanding, however, most people do not have access to such a machine. After the copper areas of the board have been either sanded or bead blasted, an acidic bath of 50% vinegar and 50% (preferably distilled) water is applied to the board. A small brush like a toothbrush can be used to scrub the board's area. The purpose of introducing an acid to the effected area is to neutralize what the battery has left behind. The liquid and fumes from the battery are actually a base, not an acid. Next, rinse the area of the board with water. Once the board is clean, isopropyl alcohol (the higher the alcohol percentage the better) is applied to the same area to rinse away the acid bath, and hopefully dissipate any remaining water. Finally, the board is either blown dry or air dried. This may be a given, but DO NOT ATTEMPT TO APPLY POWER TO THE BOARD IF IT IS STILL WET! Most liquids are conductive to some extent. After the previous steps are performed, the task of installing the new components begins. If any traces or solder pads were damaged, see the Repairing Traces portion of this Wiki guide on to to fix them.

The point I'm trying to ultimately make is this. . . regardless of age, shape, or form, remove the battery from the CPU board, as soon as it realized that there is a battery on the board. If not, the board can be damaged, nonfunctional, and become more difficult or even impossible to repair.

4.4.2 Relocating the Battery from the CPU board

Adding a remote battery to a System 1 CPU board

4.4.3 Permanently Disabling the Slam Switches

A jumper used on each side of the C2 capacitor

Replace capacitor C2 with a jumper wire. This permanently holds the slam switch closed on a Gottlieb® System 1 CPU board. Alternately just solder a piece of wire across C2 to accomplish the same thing.

There are three main drawbacks after disabling the slam switches.

  • If the game is still being operated in an arcade environment, the door could be banged, kicked, etc., and it will not end the game and go into attract mode.
  • If the game is still being operated in an arcade environment, the game could be lifted from the front, and it will not end the game and go into attract mode.
  • Exiting from the bookkeeping, audits, and tests will not be as easy. However, this still can be accomplished by gently swinging the tilt bob against the tilt bob ring.

Considering the drawbacks, which in most instances the first two don't apply, versus the benefits, (no more sporadic resets due to flaky slam switches), permanently disabling the slam switches is typically a good idea.

If jumpering around C2 did not disable the slam switches, presume that the gate on Z29 (pin 3 - input, pin 4 - output) is potentially bad. If Z29 tests all right, the U3 spider chip may be bad. Before deeming U3 as bad, verify continuity between pin 17 of U3 and pin 4 of Z29.

4.4.4 Connecting a Logic Probe to the CPU Board

Logic probe connected to a System 1 CPU board

The most convenient place to connect a logic probe to a System 1 board set is at the positive (+5vdc) and negative (ground) legs of axial capacitor C16. The positive lead is on the top, while the negative is on the bottom. By no means should a logic probe be connected to axial capacitor C17, which located just below C16, (there is a yellow "X" over it in the adjacent picture). Capacitor C17 is for the -12vdc line. Connection to C17 could destroy a logic probe in short order, and if it doesn't, odd results will be obtained while probing circuits.

4.4.5 Using a PC Power Supply For Bench Testing

Connecting a PC Power Supply to a System 1 CPU board

System 1 CPU board needs 3 voltages to power it on the bench: +5VDC, -12VDC, and ground.

4.5 Game resets

4.6 Driver Board Issues

4.6.1 Improving 2N3055 Transistor Connection

Nut / Screw Which Secures 2N3055 Collector to Drive Line

Make certain to inspect and tighten the screws which secure the 2N3055 TO-3 transistor to the driver board. Specifically, the screw / nut as marked in the pic. It ties the transistor case (collector) to the solenoid drive line. If the case is not secured, the transistor will not function as intended.

4.6.2 Installing Blocking Diodes on the Early Driver Board Revision

Early System 1 Driver Board w/o Blocking Diodes. The seven 2N6043 transistors enclosed in the boxes will require blocking diodes.
Blocking diodes retrofitted to an early production System 1 Driver Board at Q32-Q30 (left-to-right). Q25-Q28 require the same treatment.

Early in the production of System 1 driver boards (during the run of Close Encounters), diodes intended to protect the CPU from transistor or coil issues, were omitted. Later production driver boards included these diodes in series with Q25-Q28 as well as Q30-Q32. If you have a Cleopatra, Sinbad, Joker Poker or Close Encounters, inspection of the driver board is highly recommended. Even if your game was produced after Close Encounters, inspection of the driver board is still recommended since boards were frequently swapped for repair purposes.

Retrofitting blocking diodes is fairly simple. One fairly clean method is pictured at right. Other methods would include adding the diodes to the traces on the solder side of the board as well as inserting them "in line" into the CPU-to-Driver Board wire harness.


  1. Acquire 7 1N4004 diodes (1N4001s will work).
  2. Desolder 2N6043 transistors at Q25-Q28 and Q30-Q32.
  3. Solder a 1N4004 diode into the left through hole of each 2N6043 location with the band of the diode away from the board (up).
  4. Test each 2N6043 previously removed using the diode test to ensure the transistor is still good. We want to ensure that we don't have to rework the board.
  5. Bend the left lead of a 2N6043 straight up (remember, a TIP-102 can be substituted).
  6. Fit the right two legs of the 2N6043 into the right two through holes.
  7. Solder the right two legs into place.
  8. Use a small pliers to bend the left lead (which is pointing up) and the diode lead (also pointing up) together.
  9. Solder the transistor and diode leads together.
  10. Clip the excess wire lead from both sides of the diode, being careful to not cut into the solder meniscus (volcano mound).

4.7 Solenoid and Relay Problems

When troubleshooting a System 1 solenoid / relay problem, the first thing is to determine whether or not the solenoid is controlled by the CPU. The following solenoids and relays are not controlled by the CPU:

  • Pop Bumpers
  • Slingshot Kickers
  • Flippers
  • Coin Lockout Relay

The remaining solenoids and relays are all controlled by the CPU. These solenoids and relays include:

  • Outhole
  • Drop Target Bank Reset
  • Kickout Hole
  • Knocker
  • Chimes
  • Game Over Relay
  • Tilt Relay
  • Vari-Target Reset Relay

Regardless of the type of solenoid or relay, both types are on the same +24VDC solenoid bus. Therefore, any solenoid or relay used in a System 1 game is fused by the same main solenoid fuse, and receives rectified DC voltage from the same solenoid bridge rectifier located on the transformer board. Equally, all solenoids and relays have a path which goes to ground to complete the power circuit. The paths to ground between controlled and non-controlled are just different. Non-controlled solenoids have a high powered switch between the solenoid and ground, while controlled solenoids use a transistor or group of transistors to complete the path to ground.

4.7.1 Identifying Potentially Bad Solenoids

Before turning a game on for the first time, it's best to determine if there are any solenoids, which have locked on and overheated. There are primarily two methods to approach this.

The first and easiest method to check for bad solenoids is via a visual inspection, and actuating all of the solenoids' assemblies by hand. One typical sign of a potentially bad solenoid is if there is a brown / burnt ring present around the center of the solenoid wrapper. Not all solenoids with a brown / burnt ring are bad though, and some solenoids are completely missing their solenoid wrappers all together. Therefore, it is necessary to push a solenoid's associated plunger into the solenoid. If the plunger moves freely, the solenoid is more than likely good. Don't forget to inspect the chime solenoids, (if they are used in the game), the outhole kicker, and knocker solenoid. Keep in mind that early System 1 games, Close Encounters and earlier, had a outhole kicker solenoid mounted perpendicular to the underside of the playfield. These are just like standard hole kicker assemblies. However, later System 1 games, Dragon and newer, used an outhole kicker solenoid mounted on the top of the playfield, located under the lower apron. For this style of outhole kicker, the lower apron may have to be removed to get a visual of the solenoid and to actuate it. It is very common for System 1 games to have bad knocker solenoids. This is due to the subtle signs when a knocker locks on. It will only make a noise once prior to locking on. Since it is not located on the playfield, a locked on knocker can easily go unnoticed. Chime solenoids are susceptible to this too, except the lack of a chime or a faint vibration of the chime bar may be heard. Although it is rare for a Gottlieb® solid state relay coil to fail, relay solenoids should be inspected too. If a particular solenoid plunger will not move freely, the solenoid is more than likely bad.

When in doubt whether a solenoid is bad or not, check the resistance of the solenoid with an ohmmeter. Use the solenoid resistance chart above to determine if the solenoid is within spec or not. In most cases, solenoids will have a higher or lower resistance reading than specified. An example would be an A-5195 solenoid. Its factory specified resistance is 12.3 ohms. It is not uncommon for an A-5195 to measure as low as 10 ohms. This resistance is acceptable. In general, if a solenoid measures approximately 30% less than its specified resistance, it may be bad. Likewise, if a solenoid's resistance measures approximated 1 - 1.5 ohms, it is probably bad due to a short in the windings. If a solenoid measures 0 ohms, it may be a shorted diode instead of a bad solenoid.

On the subject of diodes, look for the absence of a loose or missing solenoid diode during a visual inspection. All solenoids used in System 1 games must have a 1N4004 or higher rated diode soldered across the solenoid's lugs. Missing or shorted diodes will potentially strain the associated circuitry. Gently tug on the existing solenoid diodes to make certain they have a good mechanical connection to the solenoid lugs. If one leg of the diode is not connected to the solenoid, it is as if the diode is not on the solenoid at all.

The second, better method for identifying potentially bad solenoids is to measure each solenoid's resistance with an ohmmeter. The reason why this method is better is because a shorted coil diode will be identified while checking the solenoid's resistance. When measuring a solenoid's resistance, place the ohmmeter probes on either side of the solenoid's diode instead of on the solenoid lugs. Following this procedure will identify if a diode is connected to the coil or not in addition to measuring the solenoid's resistance

4.7.2 Non-Controlled Solenoids and Relays

Gottlieb® Non-Controlled Solenoid Circuit

Non-controlled solenoid problems are fairly straightforward. The source current for the solenoid is provided through a normally open switch pair on the Game Over ('Q') relay and a normally closed switch pair on the Tilt ('T') relay. If all of the pop bumpers and slings aren't working, take a look at the switch blades on the game over and tilt relays. They are most likely misaligned or fouled. Also, gently tug on the wires attached to the solder lugs of these switches. This ensures that the connections do not have cold solder joints, where the wires appear to be soldered to the lugs but aren't. Likewise, check the single ground wire responsible for all of these solenoids.

Non-controlled solenoids consist of the pop bumpers, slingshot(s), and flippers. They are called "non-controlled", as the driver board / CPU board does not control the activation of the solenoid. Instead, a high-current tungsten switch is used. When the switch closes, it ties the circuit directly to ground, which activates the solenoid. It is a good idea to add an inline fuse holder to this type of solenoid, except for the flippers, with a 2 amp fuse installed in case a solenoid locks on. The fuse will open protecting the circuit from overheating. Simply remove one of the wires from the coil, and add the fuse holder nearby, either the inline wire type, or a holder mounted to the bottom of the playfield.

The high current switch in this type of circuit needs filing with a points file for cleaning, and also a slightly larger gap vs. a gold flashed/low voltage switch. Too close of an adjustment gap will cause the arc produced when this switch opens to eventually pit the contacts and / or weld the switch points together. In the case of slingshots, make certain the switch dampener, which should rest on the smaller of the two switch leaves, is not contacting the larger switch leaf. If the switch dampener stays in contact with the larger leaf, the circuit path will complete inadvertently, and the solenoid will remained energized. If the solenoid stays energized for too long, the solenoid can potentially melt the insulated coating on its windings, short out, and fail, provided that the solenoid fuse does not blow.

There will also be a low voltage contact at the full stroke of the solenoid, used to supply a switch closure signal to the CPU board for scoring purposes. These switches are part of the switch matrix. Failure of these switches will not impede the physical operation of the solenoid.

None of the non-controlled solenoids are activated during solenoid test. Although, any of these solenoids can be activated by their associated switches during solenoid test, because the game over relay will be energized.

4.7.3 Controlled Solenoids and Relays

Gottlieb® CPU Controlled Solenoid Circuit

Controlled solenoid problems can be a little more tricky. In comparison to the non-CPU controlled switches, think of the driver transistor as the high current switch. Its job is to switch the coil to ground, completing the circuit and causing the solenoid to fire.

A bad driver transistor (locked on) will cause issues including the coils melting and other burning issues on the driver boards. Earlier driver boards lack protection diodes for this situation, which could lead to failed chips on the CPU board. Because of this risk many large coils on System 1 games already have factory mounted fuses installed under the playfield to protect against this situation. Any coil not protected can always have fuses added to protect the boards against damage.

Problems with driver transistors locking on are directly attributable to the poor grounds on Gottlieb® system 1 machines; all grounding mods should be done to minimize the effects of transistors that seemingly turn themselves on.

All of the 8 controlled solenoids, (if all 8 are used), are activated one by one during solenoid test. However, any controlled solenoid which is driven by an MPS-A13 lamp transistor and a remote mounted under playfield transistor will not activate during solenoid test. See the chart below for games which use lamp drivers and remote transistors to control specific solenoids.

4.7.4 Remote Mounted Transistor

Under Playfield Transistor with Emitter, Base, and Collector Labeled

Some System 1 games went beyond the threshold of 8 controlled solenoids total. The first game to do as such was Joker Poker. There are 4 drop target banks on the game, but only 3 solenoid drivers are available. To overcome this issue, a remote mounted 2N5875 transistor was added under the playfield, and an MPS-A13 lamp transistor was used to pre-drive the remote mounted transistor.

In other cases, Gottlieb® didn't run out controlled solenoid transistors. Instead, they chose to "beef up" the solenoid drive by using a 2N6043 as a pre-drive transistor. System 1 games which use remote mounted transistors are listed in the table below. If a game is not listed in this table, then it does not use remotely mounted under-playfield transistors.

Game Name Sol. Name Solenoid or Lamp Designation Pre-Driver Transistor # Transistor Type Notes
Joker Poker Kings Drop Target Bank Reset Lamp 17 Q17 MPS-A13
Close Encounters Roto Target Solenoid 7 Q30 2N6043
Count-Down Yellow Target Bank Reset Lamp 17 Q17 MPS-A13
Count-Down Blue Target Bank Reset Lamp 18 Q18 MPS-A13
Pinball Pool Left (1-7) Drop Target Bank Reset Lamp 17 Q17 MPS-A13
Hulk Left ("A") Shooter Solenoid 6 Q31 2N6043
Hulk Right ("B") Shooter Solenoid 7 Q30 2N6043
Buck Rogers Vari-Target Reset Lamp 17 Q17 MPS-A13 Remote mounted TIP-115
Roller Disco Left Drop Target Bank Reset Solenoid 7 Q30 2N6043
Torch Left Drop Target Bank Reset Solenoid 6 Q31 2N6043
Torch Right Drop Target Bank Reset Solenoid 7 Q30 2N6043
Asteroid Annie Left Drop Target Bank Reset Solenoid 7 Q30 2N6043 Remote Mounted Transistor Upgrade

Under Playfield Transistor from Joker Poker (Stock)

Gottlieb® Remote Transistor Circuit

Shortly after the release of the System 80 game Black Hole, Gottlieb® realized that it was necessary to add pull up resistors to remote mounted transistors. Otherwise, the transistor could potentially lock its associated solenoid on, and burn the transistor. However, there were several games prior to Black Hole, where a pullup resistor was never installed. It is highly recommended to add this resistor. This upgrade will decrease the chances of particular solenoids, which use a remote mounted transistor, from locking on upon power first applied to the game.

Pullup Resistor Added to Under Playfield Transistor

Gottlieb® Remote Transistor Circuit w/ Pull Up Resistor Upgrade

The 4.7K resistor is soldered to the base of the remote mounted transistor, and then tied to the 24vdc solenoid bus.

4.8 Flipper Problems

System 1 Flippers

Gottlieb® System 1 flipper assemblies are very well engineered, and very little goes wrong with them. Due to this, they are considered to be the "Sherman Tanks" of flippers.

System 1 games utilize the traditional "fat" flipper bat design (similar to Bally, Chicago Coin, and Stern), which is a carry over from the last flipper design of Gottlieb EM games. The 3" plastic flipper bat is technically called a "flipper island" (Gottlieb® part number A-13150), and uses a 3/8" wide rubber ring versus the more common 1/2" wide rubber all other manufacturers use. Another anomaly regarding System 1 flippers is they are the only flipper design that uses an upper and lower flipper bushing system. Neither bushing protrudes through the playfield.

All System 1 flippers use an A-17875 dual wound flipper coil. The general design is a coil with two windings, the "power stroke" (low resistance) and "hold" (high resistance) windings, just like many other flipper coil designs. However, only a single diode is used with this serial winding design versus others which employ a dual diode, parallel winding design. Here's how it all works. When initially engaged via the flipper cabinet button switches, both the power stroke and hold windings receive power, however, the hold winding is bypassed or shorted by the end of stroke (EOS) switch (electricity follows the path of least resistance). As the flipper actuates and opens the EOS switch, the power is then transferred to both the power and hold windings (the resistance sum of the two windings), creating a very high resistance. The high resistance allows the coil to remain turned on without creating stress on the low resistance power winding. Hence, the coil can stay turned on indefinitely in theory.

Gottlieb System 1 flipper systems do not use a flipper relay per se. Although flipper power does flow through switch pairs on Q & T relays located under the playfield.

4.8.1 Flippers Won't Work at All

Like any flipper issue, it has be determined whether the problem is electrical or mechanical in nature. Start with obvious first. Look for broken wires at the flipper coil, EOS switch, and cabinet switch first.

During visual inspection, make certain that the flipper EOS switch is closed (use an ohmmeter to determine this), and the switch pairs on the game over (normally open) and tilt (normally closed) relays are properly gapped and closed. Equally, inspect the switch pairs to see if any of the switch blades are broken or missing their contacts.

If any of the other non-controlled solenoids are functioning properly in the game, pop bumpers and slingshots, the source of the problem will be the flippers (mechanical) and or flipper circuit(s). Tilt and game over relay switch issues can be ruled out at this point.

Since high current passes through all of the switches which enable the flipper, any of the switches may be suspect. It is somewhat common for games which have been sitting dormant for years that the cabinet switch and / or EOS switch become so fouled, the flipper will not budge at all. The remedy is to file these switches with an ignition file. See the How to Properly File Switch Contacts section. A flexstone will not work for this job, as the cabinet and EOS switch contacts are very hard.

Inspect the cabinet switches for broken female spade connectors where the cabinet wiring attaches to the switch.

Finally, look at the flipper plunger / link assembly. The plunger link is a hefty plastic piece which inserted into at hollowed out end of the flipper plunger. The link is connected to the plunger with a small roll pin. The link can break or the roll pin can fall out, due to vibration. If the link is no longer connected to the plunger, the flipper will not move at all. Refrain from trying to engage the flipper with the cabinet switches. Continuing to enable the flipper coil will stress the coil, because the EOS switch will not open, transferring power. The end result is an overheated flipper or damaged flipper coil.

4.8.2 Flippers are Weak, Sluggish, or Erratic

A Gottlieb® System 1 Flipper Plunger/Link/Crank Parts. Note the "hogged out" part of the link

Worn Flipper Link
The design of the flipper crank and flipper link / plunger is peculiar to Gottlieb games. Gottlieb games from the System 1 era use a very meaty flipper link, which does not have a pivot point between it and the connected plunger. To achieve the necessary fulcrum, the flipper link has an oval opening at the point where the link and flipper crank connect. The two pieces are simply connected with a roll pin protruding through the two parts. Over time, the roll pin can sometimes cut into the opening in the link, and the roll pin will catch as the flipper crank pivots. The result is a weak flipper or a flipper which does not return to the at rest position. Using a roll pin punch tool, remove the roll pin, and replace the flipper link / plunger assembly. Pay close attention when installing the roll pin into the new plunger link. It is very easy to cut into the link with the roll pin, deeming the new link / plunger worthless.

Flipper Crank Installed Incorrectly
Reassembling a flipper bat / shoe incorrectly can result in a weak flipper. Before tightening the two set screws which hold the flipper shaft in place, make certain that the flipper crank is centered equidistant between the upper and lower flipper bushings. If placed too close to the upper bushing, it will "sandwich" the upper bushing between the crank and bat. If placed too close to the lower bushing, the crank will have friction between it and the lower bushing. The end result is a weak flipper or a flipper which does not return to the at rest position.

Fouled / Pitted Switch Contacts
Fouled switch contacts can reduce current, which in turn reduces power / strength. Make certain that the EOS switch, cabinet switch, and switch pairs on the game over (Q) and tilt (T) relays are all clean and not pitted. Filing the contacts with an ignition file will remedy the problem, provided that the contacts are not heavily pitted.

Bad Connection to Cabinet Switch
Another problem related to the cabinet switches is the female spade connector used to connect the cabinet wiring to the switch. These spade connectors can sometimes become sloppy or break. In most cases, the break is not evident, until the connector is removed and reinstalled on the cabinet switch tab. The spade connector can be removed and a new one crimped on, or the better solution is to solder the cabinet switch wires to the tabs on the cabinet switch.

Worn Flipper Plunger
A mushroomed flipper plunger can create excessive drag within the coil sleeve. When replacing the plunger / link, replace the coil sleeve and coil stop too.

Broken Coil Stop
The coil stop "slug" is pressed into the coil stop bracket. It is somewhat common for the slug to become detached from the coil stop bracket. The coil stop slug will then be "free floating" within the coil sleeve. This can create some interesting problems, but the most noticeable are reduction in flipper power, decrease in flipper stroke or both.

System 1 Flipper w/ Link Extension (tail) Circled

Flipper Tail Dragging
Some System 1 flipper plunger / links have a centering "tail" located on the backside of the flipper link. This tail can create drag, in turn, reducing power to the flippers. When servicing System 1 flippers, remove the link extension / tail with a pair of dikes or a hacksaw. Make certain the tail is completely removed, otherwise the remains of the tail could potentially get caught in the centering hole. The tail was removed with later flipper designs and remanufactured links.

Incorrect Flipper Rubber Installed
Gottlieb used 3/8" wide rubber on flippers. It fits perfectly into the groove on the plastic flipper bat. Everybody else used 1/2" wide rubber, and that tended to get installed on the Gottlieb games, too. When a 1/2" wide ring is used, it almost fits, but because of the groove, it will present a funny angle to the ball instead of a flat plane. The results are either air balls, or the flipper will smack the ball downward into the playfield.

Cracked / Broken Plastic Bat
Sometimes the flipper bat cracks. Replacements are available. The screw that holds the plastic flipper bat on the metal shoe is located on the underside of the flipper. Loosen the two set screws on the flipper crank, and the shoe and bat will come free.

Broken Hold Winding
Erratic flipper function is defined as a flipper which will not remain in the up (hold) position when activated. The flipper will move rapidly up and down as if it is "machine gunning". This is typically the result from a break in the hold winding right at the flipper coil lug. One resolution is to locate the broken coil winding (this will be the thinner of the two windings), and unwind one turn from the coil. This can be accomplished if the side of the winding is not connected to the common lug of the flipper coil. Note that the power winding cannot be unwound if it breaks. This is because the power winding is wound on the coil bobbin first, and is located beneath the hold winding. Once one turn of the hold winding is unwound from the coil, the excess length must be shortened. After the correct length is determined, the portion of the winding which will be soldered to the coil lug must have its insulation stripped off. The red or green hue on the coil winding is actually a thin insulation, which is used to keep the winding from shorting to adjacent windings. Gently scrape the coating off the winding by using an exacto or utility knife, exposing the copper wire of the winding. Then wrap the uninsulated winding around the coil lug, and solder it. If a single winding cannot be removed from the existing coil, complete coil replacement is the solution.

4.8.3 Flippers Will not Return to at Rest Position

The EOS switch assembly is actuated by the pointed part of the flipper crank assembly. This is a metal-on-metal contact point. Due to the design of the flipper crank, it will eventually wear a hole in the EOS actuating blade. The fix is to replace the EOS switch assembly.

As mentioned in the previous section, the flipper link can become cut by the roll pin which secures it to the flipper crank. This can also cause the flipper to not return to the rest position.

Also mentioned in the previous section, the flipper coil stop slug can detach from the coil stop bracket, causing the flipper not to return completely.

If the flipper return spring has become stretched or is no longer connected to the flipper crank or coil stop anymore, the flipper will not return properly.

4.9 Lamp Problems

Lamp problems are common with most any pinball machine, and Gottlieb® System 1 games are no exception. All Gottlieb® System 1 games use either a #44 or #47 lamp. The choice of which lamp to use is the preference of the game owner. An occasional #455 blinker bulb is used in the backbox in a specific socket, and will only be powered when the game is in the game over state. Of course, #455s can be used elsewhere in the backbox for effect purposes.

It is highly recommended not to replace or remove lamps with the power to the game on. There are primarily two reasons for this.

  1. Some lamp sockets must have their mounting brackets bent back to access the bulb for replacement. In turn, the potential of inadvertently shorting one lamp socket to another is possible.
  2. Lamps are constructed of an equal balance of glass and conductive metal. If a bulb slips out of one's grasp when trying to remove or install with the power on, there are many areas in the bottom of the cabinet, where the metal of the bulb can short across. A short across other circuits could potentially lead to other unplanned or otherwise unnecessary repairs needed to perform.

So in short, change or remove bulbs with the game's power off, just to be safe.
All System 1 games have three separate lamp circuits. The circuits are comprised of:

  • General illumination for the backbox
  • General illumination for the playfield
  • Controlled lamps for primarily the playfield, although, there are four controlled lamps located in the backbox (shoot again, high score game to date, tilt, and game over)

Just one note about controlled lamps. It’s unfortunate, but System 1 games do not strobe the lamps, (turn the controlled lamps on / off), during attract mode. Being at the mercy of the game’s lamp test mode, (self test step 13), is not the greatest option for testing lamps either. During lamp test, the lamps are only powered on solidly for 5 seconds. 5 seconds isn’t nearly enough time to troubleshoot a non-functioning lamp. So, it is best to start a game, and figure out what events it takes to turn the lamp on.

Below are several approaches used to determine the source of a lamp problem, and how it can be resolved.

4.9.1 Bad Bulbs

The first thing when troubleshooting lamp problems, and this may seem blatantly obvious, but determine whether the lamp is good or not. Don't rely on the bulb being brand new either. The ratio of brand new, bad bulbs is slim, but there is that chance a new bulb is not good.

Making certain an old 9v battery is putting out an acceptable lower voltage
Testing a 6v bulb with a dying 9v battery

The bulbs used in a System 1 game are powered by ~6 volts. A great way to quickly test a bulb is to use a dying 9v battery. Don't use a fresh 9v battery, or you will shorten the life of the bulb. Find a battery that is roughly putting out 7v - 8.25v. An old battery from a smoke detector works pretty well.

Place the tip of the bulb on one of the battery terminals, and cock the outer metal casing of the bulb to touch the other terminal. Orientation of the bulb with regards to the positive and negative terminals does not make a difference in this case. Do not hold the bulb across the battery terminals for very long. Just long enough to determine if the bulb's filament is lighting or not.

4.9.2 Lamp Power Issues

Secondly, make certain there is power at the lamp socket. The game will have to be turned on for the following procedures. General Illumination Lamp Power Issues

GI lamps are powered by ~6VAC. When testing a GI lamp socket for power, each lead of the DMM (now set in AC mode) will be placed on the two leads of the lamp socket. If there isn't power at the lamp socket, suspect a bad fuse first. Keep in mind that the backbox GI and playfield GI have two separate fuses located on the transformer board in the bottom of the cabinet. These are typically higher amperage rated fast-blo fuses. The backbox GI on a System 1 game is always on when the game is turned on. If the backbox GI fuse is good, and no backbox lights are lit, the connection at A6J3 / A6P3 (pins 12 and 13) which feeds the GI could possibly be bad.

Gottlieb® System 1 Tilt Relay with Make-Break Switch Highlighted

The playfield GI is always powered on too, except when the game is in tilt mode. If the game was not tilted and /or the tilt switches are not stuck closed, check the switch stack on the tilt relay under the right top of the playfield. Specifically focus on the lower two switch leaves of the make-break switch. These switches can sometimes get bent or misaligned due to the nature of the location of the relay and stack, and become inadvertently closed. If the playfield GI fuse is good and the tilt relay switches are good, the connections at A6J5-1 / A6P5-1 and A6J4-7 / A6P4-7 may be suspect.

If the fuse to a particular GI circuit is bad, and continues to blow every time a new fuse is installed, a short is probably causing the issue. A shorted lamp GI circuit is probably the worst and most difficult lamp related issue to resolve. In most cases, the GI power lines are uninsulated wiring, which make them susceptible to shorted circuits. First, determine if the GI short originates on the backbox lamp insert or on the playfield. GI shorts on the playfield are typically more common than lamp insert shorts. Pop bumper lamps are not CPU controlled, and are included in the playfield GI string. Also, depending on the game, star rollover lamps and kickout hole lamps are sometimes part of the playfield GI circuit. Consult the game manual for these particulars.

Although it can be a pain and time consuming, the best approach is to remove all of the bulbs in the associated shorted GI string. In removing all of the bulbs, we are trying to isolate whether the problem is a bad, defective bulb, or one of the GI power lines is shorting to something else. Controlled Lamp Power Issues

Controlled lamps are powered by ~6VDC. When testing a controlled lamp socket, the red lead of the DMM (now set in DC mode) will be placed on the lamp socket mounting bracket. The bare wire soldered to the lamp socket's mounting bracket is the power bus not the ground bus, so be careful. The black lead of the DMM will be placed on ground. If working under the playfield, the ground plate in the bottom of the cabinet is a good place to connect to ground. If working in the backbox, find where one of the green wires with a yellow trace is screwed to the metalwork, and place the lead on it. System 1 game side rails, lockdown bar assemblies, and other associated trim metalwork, except the coin door, were not grounded from the factory like Bally, Williams, and Stern. Therefore, using any of these as a ground reference is not recommended.

If there isn't any power at the lamp socket, suspect a bad fuse first. The controlled lamp circuit has a separate fuse on the transformer board, and is normally a 5 amp slo-blo fuse. If the fuse tests fine, there is a separate set of normally closed switch leaves on the tilt relay, which pass the controlled lamp power to the playfield lamps. Inspect and adjust these switches if necessary. If the controlled lamp fuse and the switches on the tilt relay both test good, there may be an issue with the connection at A6J4-6 / A6P4-6.

If the fuse for the controlled lamps is bad, and continues to blow after a new fuse is installed, suspect a bad controlled lamp bridge rectifier. The lamp bridge rectifier is located on the transformer board. Please see the "Testing a Bridge Rectifier" portion of the PinWiki guides.

If all of the above tests good, there may be a short on the controlled lamp bus line. This is not a very common occurrence, but it can happen. Inspect the underside of the playfield for any wires or brackets touching the controlled lamp bus line, which shouldn't be touching.

4.9.3 Bad Lamp Sockets

Third, determine if the lamp socket is good. Some games have been through the wringer, and the sockets didn't hold up too well due to abuse, a damp environment, or other various reasons. Start by turning the power to the game off. If the socket has some corrosion, try using a lamp socket cleaning tool first. If a lamp socket cleaning tool is not available, a small wire brush used for cleaning copper fittings, a rolled up piece of 220 grit sandpaper, or a Dremel tool with a small wire brush attachment can all be used. After the socket has been cleaned, place the bulb in the socket for the following procedures.

If testing a GI lamp socket, use the dying 9v battery trick again. Remove the fuse of the particular GI circuit which the lamp socket being tested is located. Connect the terminals of the 9v battery to the bulb socket with alligator clip leads. Be careful not to short the alligator clips to each other at the battery's terminals. Equally be very careful not to short the clip leads to an adjacent switch on the pinball machine, or anything else for that matter. One clip will connect to one side of the socket, and the other lead will go to the other side of the socket. DO NOT ALLOW THE BATTERY TO STAY CONNECTED VERY LONG. Since this is a GI lamp circuit, other lamps in the string will be powered by the battery. If the battery is connected to the string for too long, the battery will start to get hot. The battery does not have enough power to keep a string of bulbs lit for too long. The lamp may only glow very dimly, but that is enough to determine if the socket is good or not.

If testing a controlled lamp socket, remove the A3-J3 and A3-J5 connector housings from the bottom of the driver board first. Then remove the fuse for the controlled lamp circuit. Clip one lead of the battery to the lamp socket mounting bracket and the other to the solder tab. The orientation of the negative and positive leads of the battery terminals makes no difference. Again, keep the battery connected just long enough to see if the lamps lights to determine whether the lamp socket is good or not.

4.9.4 Controlled Lamp Issues Lamp(s) Will Not Turn On

So, the bulb is good; the socket is good; there's power at the socket; and the lamp still won't light. Well, this occurrence can only really happen if there is a controlled lamp involved. If all three of the above things apply, it can only mean one thing - the bulb is not getting properly grounded, and will not turn on. The source of this problem may be due to several different issues. But, it is best to start at the bulb socket, and work backward towards the CPU board.

Determine if the connector and wiring from the output of the driver board to the lamp socket is good. With the power off, check the continuity between the solder tab of the lamp socket and the collector (right leg) of the associated lamp transistor. If there is continuity, it’s time to test the transistor. See the How to test a transistor portion of the PinWiki guide. If the transistor tests fine, a gate on the 74175 may be bad. The use of a logic probe on the input and output of the associated lamp gate would be a the best test procedure for definitive results.

If more than one controlled lamp is not lighting, check the game’s manual / schematics to see if the bulbs are related in some way. When four lamps are not lighting, it may appear that the 74175 which controls the lamp transistors may be at fault. This can happen, but the more commonly related issue is that the device select signal for a particular 74175 is lost between the CPU and driver board. This can be due to a bad connection at A1J5 or A3J1. See the chart below for the lamp device select signal path. Finally, if the connections, associated 74175, and lamp transistors are all right, the circuitry on the CPU board is probably at fault.

Device Select CPU Connector Driver Input Driver Quad Flip-Flop (74175) Transistor #s Lamp #s
DS1 A1J5-21 A3J1-5 Z1 Q1-Q4 L1-L4
DS2 A1J5-20 A3J1-6 Z2 Q5-Q8 L5-L8
DS3 A1J5-19 A3J1-7 Z3 Q9-Q12 L9-L12
DS4 A1J5-18 A3J1-10 Z4 Q13-Q16 L13-L16
DS5 A1J5-17 A3J1-13 Z5 Q17-Q20 L17-L20
DS6 A1J5-16 A3J1-14 Z6 Q21-Q24 L21-L24
DS7 A1J5-14 A3J1-15 Z7 Q33-Q36 L25-L28
DS8 A1J5-15 A3J1-16 Z8 Q37-Q40 L29-L32
DS9 A1J5-13 A3J1-17 Z9 Q41-Q44 L33-L36

One last thing to keep in mind is that the grounds for the lamp drive transistors are discrete, and they are not all tied together on the driver board. If more than four lamps are not lighting, one of the grounds may potentially have a bad connection. Here are the groups of lamp transistors which share common grounds and their associated ground connector pin:

  • L5 - L11 (pin A3J5-16)
  • L12 - L19 (pin A3J3-21)
  • L20 - L27 (pin A3J3-19)
  • L28 - L36 (pin A3J3-10) Lamp(s) Will Not Turn Off

If a single lamp is involved, or only a handful of lamps with different lamp device select signals, suspect the lamps' associated drive transistors. If a group of four lamps will not turn off, and they are all controlled by the same 74175, suspect the associated 74175 or the device select ("DS" on the schematics). If numerous groups of four lamps will not turn off, suspect the associated 7404 on the CPU board, either Z24 for DS1-DS5 device select signals or Z25 for DS6-DS9 device select signals. If the lamps involved originate from both groups of device select signals, suspect the 74154 4-to-16 decoder IC, Z30, on the CPU board, or possibly the U3 10696EE spider chip on the CPU.

4.10 Switch Problems

There are two types of switches used in System 1 games:

  • High current switches with tungsten contacts
  • Low current switches with gold flashed contacts

And there are two rules to follow regarding switches.


The first rule is a little obvious with high current switches, but possibly not so evident with low current switches. The potential to short switches to adjacent metal objects or power bus lines is there. To keep from creating worse, more complicated issues beyond the initial issue, please heed the above two rules.

4.10.1 High Current Switch Problems

High current switches are used wherever the +24VDC solenoid bus passes through. These switches have large surface contacts which allow the solenoid power to pass through without prematurely failing. Assemblies such as the pop bumper power switches, (switches closest to the underside if the playfield), slingshot power switches (located above the playfield), flipper end of stroke switches, flipper cabinet switches. and some relay stack switches. All of the high current switches can be burnished with an ignition file or a flexstone.

Common problems related to high current switches are:

  • Fouled or pitted switch contacts
  • Maladjusted switches
  • Missing contacts
  • Contacts no longer peened to its switch leaf
  • Broken switch leaves

The first two issues can typically be resolved by either filing the switch pairs or readjusting the switch leaves accordingly. However, if switch contacts are severely pitted, or switches are overly bent numerous times that restoring their proper function is not possible, it is best to replace the switch pair. Likewise, if the switch problem falls into the latter three issues, it is best to replace the switch pair.

4.10.2 Low Current (Switch Matrix) Switch Problems

Low current switches are all of the switches used in the switch matrix. A signal is sent from the CPU on one leaf, while the signal is sent back to the CPU via the other leaf, provided that the switch is closed and functioning properly. The amount of current passing through the switches and its contacts is minimal. Each switch on the switch strobe side has a 1N270 Germanium diode. The purpose of this diode is to isolate each switch from one another in the matrix. Without a diode installed, more than one switch closure would be recognized by the CPU. Switches Stuck Closed

Two of the most common problems with switches staying closed are:

  1. The switch dampener is shorting to the adjacent switch leaf.
  2. Switch closures suddenly appear after new rubber is applied to the playfield.

The switch dampener is a piece of slightly bent metal located between the two switch leaves. The purpose of the switch dampener is twofold. First, it is used to adjust the switch leaf, which is typically furthest away from rubber or a rollover switch actuator. The dampener rests against the shorter adjustable switch leaf of a switch pair. Since thicker, more rigid metal is used than the switch leaves, the dampener is easier to adjust a switch more precisely if bending it alone or while paired with the switch leaf. The downturn is that the dampener can be adjusted so it rests against the longer switch leaf, thus shorting the switch closed.

Often, when you replace the rubber on the playfield, since the rubber is tighter, switches that are behind the rubber will exhibit less gap. This is especially true when you tighten the posts that hold the rubber before installing the new rubber (always check the post tension to the playfield as often the posts become loose). When you put the new rubber on, check the switch(es) behind it to ensure they are not gapped too close, and adjust if so. The blade that touches the rubber should barely touch it, and the blade behind it should be about 1/8"-3/32" away. This way a slight graze of the ball on the rubber will activate the switch, but not so close that multiple closures will occur, nor will vibration from other mechanical devices cause false closures. Multiple Switch Closures From the Same Switch

Two of the most common problems with switches closing more than once are:

  1. The switch dampener is not adjusted tightly against the adjustable switch leaf of a switch pair.
  2. Switches are gapped too close.

The second purpose of the switch dampener is to decrease the amount of bounce from a switch once it closes. If you inspect the action of a switch closure, there is always some degree of bounce after the two switch leaf contacts make initial contact. Because the switch leaves are very flexible, the amount of bounce without a switch dampener is much more drastic. The end result of more switch bounce is multiply switch closures.

Switches can become gapped too close, especially if new rubber replaced on the playfield. See the above description regarding replaced rubber for a detailed explanation why this occurs. Switches not Showing as Closed When They Should Be

Conversely, switches may not be identified by the CPU board as being closed when the switches are physically closed. There are several reasons why this occurs. The reasons, (listed from most common or simplest to resolve to least common or most difficult to resolve), for this to happen are:

  1. The switch is dirty.
  2. The gold contacts on the switch have have been burnished or filed at one time.
  3. The connector contacts at A1-J7 or A1-J6 are bad.
  4. There is a break in the switch strobe or switch return line.
  5. A shorted switch diode.
  6. The buffer or spider chips in the switch matrix have failed.
  • Inside a pinball machine, there are many different contaminants which can foul a switch, and switch contacts do and will get dirty over time. See the section below on how to clean a low current switch.
  • If cleaning a switch does not resolve the issue, carefully inspect the switch contacts with high magnification. If the contacts are drastically scored or appear to have been sanded, the only resolution is to replace the switch pair. During the EM era, the common practice was to clean switches with an ignition file or a flexstone. Because only high current switches were used then, these were both acceptable practices to clean a switch. However, some operators or repair people did not initially grasp the concept of not cleaning solid state switches by filing or burnishing.
  • The connectors at A1-J7 and A1-J6 handle all of the switch strobes and returns. If the connectors have not been repinned, it is common for the metal connectors to loose tensile strength, become corroded due to alkaline battery damage, or break. If any of these things have happened, the connection to the CPU board is compromised, and switches may work sporadically or not at all. The best recourse is to remove all the existing connectors, and replace the connectors with new ones. Replacing connectors by crimping new ones in place is the proper method. Cleaning connectors with contact cleaner, sanding the connectors, or bending the connectors are all considered only temporary fixes, if they even work at all.
  • It's not too common with System 1 games to have switch lines that break or cold solder joints on switch solder tabs, but it can happen. The best method to find a break in the line is to perform a continuity test from the switch solder tab to the appropriate connection on the CPU board, (A1J7 for playfield switches and A1J6 for coin door switches).
  • As mentioned above, the switch strobes do have 1N270 Germanium diodes soldered in line. The diodes are located on a centralized diode board. Although it's not too common, but the diodes can fail. It is best to remove the appropriate connector on the CPU board, either A1J7 or A1J6 before testing a switch diode. In doing this, other components on the CPU, if they have failed, will not skew the readings. Using a DMM in diode test mode, the typical readings seen when testing a 1N270 diode are ~.18 - .27, and no reading when the DMM leads are reversed. These numbers are just a gauge, and different DMMs will yield different results. To best identify a failed diode, take sample measurements from several other switch diodes. If a specific diode under test is comparatively out of the range with the other diodes, chances are that particular diode has failed. Replace failed diode with a 1N270 diode only.
  • All of chips responsible driving the switch matrix can fail. The return (Z9 or Z28) and strobe (Z8) buffer chips are the first chips to test. The returns use a 7405, while the strobes use a 7404. It is common for a single gate or a couple of gates to fail on these chips. The chips do not necessarily have all gates fail. A logic probe should be used to ensure that the switch strobe and return line inputs and outputs are reacting as they should. (++++add more result detail here+++). If the buffer chips test fine, the next course of action is test the output of U5 with a logic probe. (++++add more result detail here+++) Cleaning Low Current Switches

Low current switches SHOULD NOT BE FILED OR BURNISHED. As mentioned above, the low current switches are gold flashed, and filing, using a flexstone, nail file, or sandpaper will remove the thin gold plating. In turn, the switch will become less reliable or not function at all. The best approach to cleaning a gold flashed switch is to place a piece of heavy card stock (a business card, index card, etc.) between the two switch leaves. A 1/2" wide strip of card stock works best for getting into tight locations, but a business card works in a pinch.

  1. Insert the card stock between the two switch leaf contacts.
  2. Gently close the two switch leaves, applying slight pressure at the switch contact of the outer switch leaf or leaves.
  3. With the switch leaves still closed on the card stock, slowly pull the card stock strip from the length of the switch leaf. Do not pull the card stock strip from the side of the switch, because not as much surface area of the strip will be "wiping" the switch contacts. Plus, the potential to bend or twist the leaf switches out of shape is more probable.
  4. The end results of cleaning a switch are what looks like light pencil marks on the card stock, if the switch leaf contacts are in fact dirty.
  5. Repeat the whole process, until grey streaks on the card stock are no longer seen. Testing Switches in the Switch Matrix

Gottlieb® has a switch test option to test any of the switches in the switch matrix. The switch test can be entered via the white test button, which is located inside the coin door. Switch test starts once "13" is notated on the left side of the status display, and after lamp and solenoid tests have completed. For switch test, the ball can remain in the outhole, as the outhole switch is not on the switch matrix, and not tested while in switch test.

During switch test, any of the switches on the switch matrix can be tested by activating a switch closure, and the associated switch number will be notated on the right side of the status display. If multiple switches are activated, all switches will be displayed from the lowest strobe number first, incrementing the switches on the same return, and continuing to the next switch strobe line, until all results have been displayed. An example would be if all of the drop targets are down (all drop target switches closed) on Charlie's Angels. The 3 bank drop targets are switch numbers 10, 11, and 12, (top to bottom), while the 5 bank drop targets are switch numbers are 30, 31, 32, 33, and 34 (left to right). The results during switch test will display the numbers in the following sequence: 10, 30, 11, 31, 12, 32, 33, and 34.

The System 1 switch test is especially beneficial for identifying complete switch strobe or return failures. If none of the switches are closed in the switch matrix upon entering switch test, but multiple switches are identified as being closed, a switch strobe or return failure is more than likely the culprit. An example would be if switches 02, 12, 22, 32, 42, 52, 62, and 72 are reported as closed, there is a switch strobe issue. Likewise, if switches 30, 31, 32, 33, and 34 are reported as closed, there is a switch return issue.

The switch test on a System 1 game is implemented quite well, except it is painstakingly slow. However, there is an alternate, quick and dirty method to test System 1 switches. This test will not display the actual switch number closure, but it will let the tester know that a switch has successfully been closed or not.

  1. Put the game in attract mode.
  2. Close the switch to be tested. If the displays "flicker" for a brief moment as the switch closes, the game has identified it as a successful switch closure. If the displays do not "flicker", the switch closure was not identified. Note: This test works with the original Gottlieb® and the Ni-Wumpf replacement MPU board - Pascal PI-1 or PI-1X4 replacement boards may not exhibit this behavior.

This test is particularly great for identifying whether or not a parallel wired scoring switch is stuck closed by closing a second scoring switch with the exact same switch number. If the displays do not flicker, the reason is more than likely due to one of the other parallel switches with the same number remaining closed. An example would be the 10 pt. switches used on a System 1 game. Most games have at least four 10 pt. switches. If all of the 10 pt. switches fail to score during game play, the issue is typically one of the parallel switches is closed. Although the attract mode switch test will not identify which of the many 10 pt. switches is closed, it is great for quickly verifying a switch closure.

4.11 Display Problems

The blue Futaba display glasses used by Gottlieb® System 1 machines are a fairly reliable, long-lasting display. Although, they can and do still fail. It's just a matter of diagnosing the symptoms of a failed display.

Display problems can primarily be classified into the following categories:

  1. Power problems
  2. Display glass failure
  3. Data problems
  4. Tired displays

4.11.1 Display Power Problems

Before even attempting to work on System 1 displays, there are two caveats to heed. First and foremost, the displays function due to the necessity of several voltages, including high voltage. IF YOU ARE UNCOMFORTABLE WORKING ON HIGH VOLTAGE CIRCUITS, THEN DO NOT WORK ON SYSTEM 1 DISPLAYS! High voltage can hurt or even kill you. If you don't feel comfortable working around this type of scenario, then hire a professional to do the work. Secondly, any time a display connector needs to be disconnected, DO NOT REMOVE ANY DISPLAY RELATED CONNECTOR WITH THE POWER ON! This goes for the connectors located directly at the display, connectors A1J2 and A1J3 on the CPU board, A2J3 on the power supply board, and A6J3 / A6P3 from the transformer. Removing connectors with the power on can damage the display, the CPU board, and / or you. Sorry to "yell", but it is extremely important to stress the above two statements. Now that this is out of the way, let's move on.

As stated above, the displays need several sources of voltage to function properly. The display voltages used are broken down by the type of display: +60VDC, +8VDC offset, and 5VAC are used for the 6-digit displays; +42VDC, +4VDC offset, +5VDC logic (for the 7432 chip - Z1), and 3VAC are used for the 4-digit status display. When using a 6 digit display with DI513 Dionics chips, +5VDC is necessary for RP1 and RP2 8.2K resistor networks. If any of the above voltages are missing, the display will never light.

Prior to plugging in and turning the game on for the very first time, it is a good practice to check all of the fuse values located on the transformer board first. There is a 1/4 amp slo-blo fuse used for the display voltage, which is located on the transformer board in the bottom of the cabinet. With the game unplugged from the wall outlet, remove the fuse from its fuse holder. When checking fuses, never "eyeball" a fuse. Your eyes may tell you that the fuse is good, but your eyes can fool you. Use a digital multi-meter (DMM) or a continuity tester to check fuses. Put each lead of DMM on opposite ends of the fuse. A tone should be heard. If not, the fuse is bad, and should be replaced with the same value. Fuses are used to protect equipment, the surroundings, and you. Installing fuse values with higher ratings is very dangerous. DO NOT USE A FUSE RATED AT A HIGHER RECOMMENDED VALUE! If the existing fuse is blown, it may not necessarily mean there is a problem. Fuses do get stressed, and sometimes just fail. However, there is more than likely a problem somewhere in the display power train.

With the game still unplugged, the next course of action is to place connector A2J1 on the power supply. A2P1 is the bottom connection on the power supply, and receives all voltages directly from the transformers and a single ground from the ground strip. The connector can be plugged in upside down, but it will take a fair amount of effort to do so. Just be careful when plugging this connector in. Once A2J1 is connected, remove any other connections from the power supply (A2J2 and A2J3). All voltages should be tested before any boards or displays are connected to them.

System 1 Power Supply with A2J3 highlighted

At this point, plug the game in, and turn it on. Using a DMM or volt meter, check all of the voltages at A2P3. For the +60VDC (A2P3-1) and +42VDC (A2P3-3), pin 5 of A2P3 must be used as the ground reference. Using any other point for a ground reference will result in incorrect voltage readings. Pin 5 is marked "COM" on the board. If the +60VDC is a little low, it can be adjusted with the potentiometer located on the right of the board. The +42VDC is derived from the +60VDC. If there is +60VDC, but not +42VDC, The 18v CR12 zener diode or the R18 resistor may have failed.

If the two high voltages test all right, it's time to check the two offset voltages. The offset voltages are +4VDC (A2P3-7) and +8VDC (A2P3-8). This may seem odd, but either A2P2-4 or A2P2-5 must be used as a ground reference to test these voltages.

If all the display voltages are satisfactory, it is time to move onto the next step of visually inspecting the display boards for obvious defects.

4.11.2 Display Glass Failure

Display with a good display glass

The simplest and easiest problem to identify is display glass failure. All of the 6 digit displays used by Gottlieb® System 1 games will have a black "blotch", for lack of a better term, in the upper left and lower right corner of the glass. The 4-digit status display typically has only one black blotch. The evidence of a black blotch or blotches is good.

Display with Broken Nipple on Back

However, if there is a muted white blotch visible at the corners of the display, it means the display's "vacuum" has been compromised, either due to a cracked glass or broken nipple. If this is the case, the display glass can not be repaired and is useless.

Display with Broken Top Filament. Note that this is the Dionics chipset version of the display.

The display filaments within the glass can also break. The end result will be segments with missing sections or "hot spots" when the display is powered. The "hot spots" are caused by the "dangling", broken filament shorting to other good filaments. If a display filament breaks, do not use the display as shorted displays can damage other game components.

Even though the glass itself is bad, the chips on the display board may still be good. So don't necessarily discount the display as being all bad. UDN6118A and 7432, (chip used on status display only), chips are getting more costly, and Dionics DI513s are very scarce. Since the display board is single sided, removal of the chips is quite easy. Plus, the display PCBs are no longer being made. The display board and / or chips may come in handy some time in the future.

4.11.3 UDN6118 Failure

The majority of 4 and 6 digit displays utilize two UDN6118 "Vacuum Fluorescent Display Drivers". These ICs do not fail often. However, when they do fail shorted, they can affect the performance of the rest of the display set.

Test method for a UDN6118 or UDN7180 display driver. Colored dots represent DMM probe locations (red lead, black lead)

UDN6118 driver ICs can be tested using a DMM. Click on the image at left for the procedure.

4.11.4 Display Data Problems

When there are display issues, one first has to determine whether there is a problem with the display itself, the connectors involved, or the chips on the CPU board that control it.

NOTE: when removing the connectors from the displays or the connectors on the CPU board (A1J2 & A1J3), have the power to the game OFF. Failing to turn the power off can result in damage to the CPU board and or display board.

An excellent image to show both digit and segment problems. Note the red circles showing the same digit out on for players 1 and 3. Also note the yellow circles showing segment "g" out for players 1 and 2.

Issue with only 1 display
If the problem is only showing up one display, suspect that the connector at the display itself is problematic, or there is an issue on the display board. Problems on the display board can consist of a bad solder joint, a broken display lead from the display glass, or faults with the driver chips (Sprague UDN6118 or Dionics DI513) on the board.

Issue with more than one display
If the problem shows up on two or more displays, suspect one of the two connectors on the CPU board (A1J2 or A1J3), or the chips which control the display data on the CPU board. If there is a digit issue, the issue will be present on player 1 and 3 or player 2 and 4 displays. If there is a segment issue, the issue will be present on player 1, 2, and the status displays or player 3 and 4 displays. Although the picture shown to the left is from a System 80A game with 7-digit displays, the problems illustrated apply to System 1 games as well.

Gottlieb® System 1 Display Diagram

The charts listed below, map out each signal to each specific display. The first chart maps the display digit information, while the second and third charts map the display segment information.

Display Digit Information
Digit Number Display(s) CPU Pin Connection Chip on CPU Board - Pin
D1 Players 1 & 3 A1J3-9 Z21-3
D2 Players 1 & 3 A1J3-8 Z21-6
D3 Players 1 & 3 A1J3-6 Z21-8
D4 Players 1 & 3 A1J3-7 Z21-11
D5 Players 1 & 3 A1J3-17 Z20-3
D6 Players 1 & 3 A1J3-16 Z20-6
D7 Status A1J3-14 Z20-8
D8 Status A1J3-15 Z20-11
D9 Players 2 & 4 A1J3-11 Z19-3
D10 Players 2 & 4 A1J3-10 Z19-6
D11 Players 2 & 4 A1J3-12 Z19-8
D12 Players 2 & 4 A1J3-13 Z19-11
D13 Players 2 & 4 A1J3-19 Z18-3
D14 Players 2 & 4 A1J3-18 Z18-6
D15 Status A1J3-20 Z18-8
D16 Status A1J3-21 Z18-11

Display Segment Group A Information

Segment Display Group CPU Pin Connection Chip on CPU Board - Pin
a Segment Group A A1J2-3 Z16-13
b Segment Group A A1J2-4 Z16-12
c Segment Group A A1J2-5 Z16-11
d Segment Group A A1J2-6 Z16-10
e Segment Group A A1J2-7 Z16-9
f Segment Group A A1J2-1 Z16-15
g Segment Group A A1J2-2 Z16-14
h Segment Group A A1J2-18 Z15-8

Display Segment Group B Information

Segment Display Group CPU Pin Connection Chip on CPU Board - Pin
a Segment Group B A1J2-13 Z17-13
b Segment Group B A1J2-14 Z17-12
c Segment Group B A1J2-15 Z17-11
d Segment Group B A1J2-16 Z17-10
e Segment Group B A1J2-17 Z17-9
f Segment Group B A1J2-11 Z17-15
g Segment Group B A1J2-12 Z17-14
h Segment Group B A1J2-19 Z15-6

4.11.5 Rejuvenating Tired Displays

Rejuvenating tired System 1/80 displays

System 1 displays, especially those that haven't been turned on for a long time, sometimes fade. These displays can be rejuvenated by applying voltage to the outside pins of the display glass. Note that voltage should be applied to the display glass pins, NOT the card edge pins. This process "burns" the impurities that accumulate on the filaments off.

In the picture at left, general illumination power (7VAC) from the lamp insert panel is being used to rejuvenate a display.

1. Turn the game off
2. Remove the connector from the display
3. Connect jumper clips from a voltage source to each of the outside pins of the display glass. Note that the lower the voltage applied, the longer the display can tolerate this "rejuvenation".
    That is why some techs choose to use the lower GI AC voltage for this purpose.
4. Power the game on for 1 minute.
5. Disconnect the jumper wires and reconnect the display.
6. Power on to test the display.
7. If the display still isn't bright enough, repeat this process for 1 minute each time, until the display is satisfactorily bright.

Note that if the display filaments, which run across the display horizontally begin to glow orange (or worse, white), too much voltage is being applied or the display has been connected too long. This risks burning one or more of the display filaments out and ruining the display. A cautious, 1 minute at a time, process is warranted.

Note also that one particular System 80 tech ("System 80, not just a job, it's an adventure") suggests that merely leaving the game powered on for 24 hours will accomplish the same rejuvenation.

4.11.6 All Other Display Issues (Not Caused by Displays)

There are several issues which appear to be display related, however, they ultimately are not. In these instances, the displays are used instead as a visual identifier of a particular issue. Open Slam Switch

Simulation of a Display Effected by an Open Slam Switch

If after turning a System 1 game on, and the scoring displays turn on immediately without a 5 second delay, there is a problem. However, this is not a display issue, if the displays are showing all outer segments (all zeroes) lit, and "strobing" or "rolling" rapidly. The problem is actually due to an open slam switch on the coin door or the ball roll tilt.

See how to permanently disable the slam switches. Shorted Coin Switch

If after turning a System 1 game on, and the scoring displays turn on immediately without a 5 second delay, there is a problem. This is not a display issue either. In this case, the scoring displays will all solidly show 000000, and not alternate between high score to date. This is typically a symptom of one of the two coin switches shorting to the coin door.

4.12 Sound problems

4.12.1 Chime Box

There is a small rubber strip on the bottom of the chime box that functions as a cushion for the chime plungers. Over time it becomes sticky and prevents the chime plunger from reacting quickly, causing a weak sounding chime. Remove this strip and replace it with some thick foam weatherstripping; you might have to use 2 layers to get a nice thickness. Clean the ends of the plungers of any sticky residue with some isopropyl alcohol. Inspect the nylon tips of the plungers and replace any that are too short.

Each chime bar is held to the chime box by a screw with a rubber grommet enabling the chime bar to 'float' without touching any metal. If this grommet is old, missing or simply worn, the chimes won't ring true, they'll end up sounding like a dull ting instead of a music like tone. You can get new grommets at any hardware store that has a good selection of hardware. (Sears Hardware and Ace are good places to look). Make sure the chime bars are not screwed down all the way to the box; you want the bars to 'float' for aurally pleasing results.

4.12.2 Tone Board

The design of the basic tone sound board used in system 1's produces a tone as long as the 555 timer's input is grounded. If a continuous tone is produced, suspect a bad driver transistor on the lamp/solenoid driver board holding the ground on.

4.12.3 Multi-Mode Sound Board

Ground screw for 5v regulator on back side of sound board

Make certain to inspect and tighten the screws which secure the 5v regulator to the sound board. The screw / nut as marked in the pic ties the regulator case to ground. If the case is not tied to ground, the regulator will not function as intended.

4.12.4 Converting From a Tone Board to Chimes

Converting from a 3 tone sound board to a a mechanical chime box is rather a simple process. There is a 6-pin Molex connector (A6-J2 / A6-P2) located just prior to A7-J1 of the tone board. This connection carries the driver signals for each chime tone, the knocker, and two +24vdc solenoid lines. A factory System 1 chime box conveniently has the exact same connection.

Gottlieb® System 1 Tone Board w/ A6-J2 Connector Highlighted

  1. Disconnect A7-J1 from the tone board, and disconnect the 6-pin Molex connector (A6-J2 / A6-P2).
  2. Remove the tone board from the side of the cabinet.
  3. Find a suitable mounting location for the chime box, and place it on the side of the cabinet.
  4. Mark for the 3 holes at the top and a 4th hole at the bottom of the chime bracket.
  5. Drill all 4 holes.
  6. Place a screw in the lower hole first, and screw it in approximately 3/4 of the way. This screw is used only to support the chime box bracket, and should not be tightened completely.
  7. Screw in the remaining 3 screws.
  8. Connect the 6-pin connector.

Gottlieb® System 1 Chime Box w/ A6-J2 Connector Highlighted

A chime box can be used from an EM game by modifying some wiring and adding diodes to the coils. Daisy chain the +24vdc solenoid bus wire to one lug on each coil. Put the signal wire for each chime tone on the other lug; the smallest chime is the 10 point chime, middle sized is 100 points, and largest is 1000 points. The wire colors are orange-black (311) for 10, green-red (244) for 100, and purple-red (255) for 1000. Orient an 1N4004 diode with its band towards the power bus (daisy-chained) wire on each solenoid.

Keep in mind that most Gottlieb® EM chime boxes use A-5195 coils versus the A-17876 coils used in System 1 chime boxes. The A-5195 coils are half the resistance of the A-17876 coils, so the chimes will be struck harder.

4.12.5 Converting From Chimes to a Tone Board

Not nearly a common practice as converting from a sound board to chimes, but it is possible.

4.13 Drop Target Problems

4.13.1 Replacing Drop Target Plastics Early System 1 Drop Target Removal

For now, please review the drop target removal guide available at Later System 1 Drop Target Removal

For now, please review the drop target removal guide available at

4.14 Vari-Target Problems

This is a stub

System 1 Vari-Target Mechanism (Totem)
System 1 Vari-Target Mechanism with Recommended Lubricant

4.15 Roto Target Problems

5 Game Specific Problems

5.1 Joker Poker

If the "kings" drop target reset coil locks on at start up, see the Remote Mounted Transistorsection.

6 Repair Logs

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

Power supply.

  • Problem: Had a "no displays" symptom.
  • Cause: Found transistor Q4 shorted emitter to base.
  • Solution: Replaced transistor and all was good. Schematic calls out Q4 as a type MPS-A43, but you can also substitute a type MPS-A42 which is a better, more robust transistor. Either type can also be replaced with an NTE287 transistor.
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