What Repair Experience Is Expected?
Little experience in fixing pinballs is assumed. Basic electrical knowledge is helpful, but not necessary. I do assume you can solder and use the basic features of a Digital Multi-Meter (DMM) such as measuring voltage and resistance. Please see http://marvin3m.com/begin for details on the basic electronics skills and tools you will need. This document should help if you just bought your first (or second, or third) pinball "as-is", and hope to fix it.

Got Schematics?
Having a schematic for your game would be ideal, but sometimes you can fix your game without it. If you don't have a schematic, order one from Steve Young's Pinball Resource (845-473-7114 or mailto:PBResource@idsi.net?subject=from_the_Sys11_Repair_Document), or in Europe from Pinball Heaven at mailto:Phil@pinballheaven.co.uk?subject=from_the_Sys11_repair_document.

Online schematics are available too at http://www.stormaster.com/RGP-Stuff/manuals/williams-system-11a.zip (900k) in ZIP format (WinZip required). These are system 11A schematics, from the game F-14 Tomcat. Individual scans are in TIF format.

Fixing electronic pinball games will require a few tools. Luckily, most are not that specialized and are easy to get.

Non-Specialized Tools Required:

• Work Light: clamp style lamp
• Screwdrivers: small and medium size, phillips and flat head
• Nut Drivers: 1/4", 5/16", and 11/32"
• Wrenches: 3/8", 9/16", 5/8" required, other sizes suggested
• Allen Wrenches: get an assortment of American sizes
• Needle Nose Pliers
• Hemostat. Handy for holding parts and springs. Best to have both the curved and straight versions if possible.
• Right Angled Screwdriver: both phillips and flat head.

Specialized Tools Required:
These specialized electronics tools are needed. Please see http://marvin3m.com/begin for details on the basic electronics tools you will need.

• Alligator clips and wire. You can buy these at Radio Shack, part number 278-001, $3.69.
• Soldering Iron.
• Rosin Core 60/40 Solder.
• De-soldering tool.
• Digital Multi-Meter (DMM).
• Logic probe.

Cleaning "Tools" Required:

• Novus #2 or MillWax (for cleaning playfields and rubber)
• Novus #3 (for polishing metal parts)
• Johnson's Paste Wax or Meguire's Carnauba Wax (for waxing playfields and cleaning rubber)
You can get Novus at many places (my local grocery store sells it), or from any good pinball vendor. I don't recommend MillWax, but others like it (mostly because they have been around for a LONG time and are used to it). Do not use any Wildcat products or CP-100! They react with plastic and can yellow ramps and lift mylar. Johnson's paste wax or Meguires Carnauba Wax you can get at Kmart.

When fixing electronic pinballs, I would highly recommend having some parts on-hand to make things easier and cheaper. All these parts are available from a pinball retailer.

Parts to have:

• #47 light bulbs: have 20 or so around. Fifty is plenty to do most games. I suggest using #47 bulbs instead of #44 bulbs, as they consume less power and produce less heat.
• #555 light bulbs: have 20 or so around. Fifty is plenty to do most games.
• #906 or 912 flash bulbs: have 10 or so around.
• #89 flash bulbs: have 10 or so around.
• #1251 flash bulbs: (used on some system 11 games).
• Fuses: I would have five of any needed value on hand at all times.
  Get 250 volt fuses, not 32 volt. Radio Shack sells fuses for a decent price. Slow-blo fuses are known as MDL fuses. Fast-blo fuses are known as AGC fuses. At minimum you'll need:
  • 1/10 amp slo-blo (not all games use this)
  • 1/4 amp slo-blo
  • 1/2 amp slo-blo
  • 2 amp slo-blo
  • 4 amp slo-blo
  • 5 amp slo-blo
  • 7 amp slo-blo
  • 8 amp slo-blo
• Nylon Coil Sleeves: the longer 2 3/16" length (part number 03-7066-5) are used when rebuilding flippers. The 1.75" length (part number 03-7066) are used for pop bumpers, etc. Sleeves with a lip (part number 03-7067-5) and tubing on each side (known as an "inline" sleeve) are used on the knocker, ball popper, etc. Also 03-7067-7 sleeves are used on drop target reset coils.
• Ball shooter sleeve, part number 03-7357.
• Flipper assembly, part number A-15848.
• Flipper Plunger/Link: used when rebuilding flippers (part number A-15847 or A-10656).
• Flipper Link Spacer Bushings: these small bushings go inside the flipper links (part number 02-4676).
• Flipper Coil Stops: used when rebuilding flippers (part number A-12390).
• Flipper EOS Switch: part number 03-7811.
• Flipper Cone Return spring: part number 10-376. I prefer not to use this style of return spring (I update all the system 11 games I work on to the newer WPC fliptronics style of return spring).
• 1/4" Heat Shrink Tubing: this is used on the flipper pawl when rebuilding flippers.
• Shooter Spring: the short chrome spring on the outside of the shooter mechanism (part number 10-149). These rust and look like crap in short order.
• 1 1/16" Pinballs: a new pinball will make your playfield last longer.
• Leg Levelers: replace those old crummy looking leg levelers with brand new ones. 3" are used on solid state games.
• Rubber Rings: you can order game-specific ring kits with exactly the rings you need. Don't forget to get flipper rubbers and a shooter tip.
• Transistors: keep a few TIP102, TIP42 and TIP36c transistors around.
• Diodes: keep a few 1N4004 and 1N4148 diodes around.
• Capacitors: keep a couple 2.2 mfd 250 volt non-polarized (Williams part number 5045-12098-00) around. These are used on the EOS switches.
• Bridge Rectifiers: keep an extra 35 amp, 200 volt (or higher) bridge rectifiers around, with wire leads. The industry part number is MB352 (Williams part number 5100-09690). System 11 games also use the "lug" lead version of this bridge too (Williams part number 5100-09418).
• 18,000 mfd 20 volt cap. Used for the +5 volt filter cap.
• 39k Ohm 1 or 2 watt "flameproof" resistors: often go bad on system 11 power supplies.
• 5 ohm 10 watt resistors: these flasher resistors often break.
• 330 ohms 7 watt resistors: if your game is Fire! or before, have some of these around as they often break from the under the playfield flash boards.
• 6808 CPU chip: have a couple around (they are hard to find). Replaces the hard to find 6802 used on early system 11 CPU boards.
• 6821 PIA chip: have several around as the CPU board uses 6 of these PIA chips.
• 74LS244 chip: a common TTL (transistor to transistor logic) chip used on the CPU board.
• 7408 chip: a common TTL (transistor to transistor logic) chip used on the CPU board.
• 2k by 8 CMOS static 24 pin RAM chip. The part number will be 2016 or 6116 or NTE2128. This RAM chip holds settings and bookkeeping totals.
• .156" Connector pins and housings: used to repair burnt connectors.

You can order the transistors and diodes from many sources. I would suggest Hosfelt in Ohio at 800-524-6464. They have cheap prices, no minimum, and good service. Also you can get the 6802, 6808, 6821 and 6116 chips from Jameco at Jameco.com and BGMicro.com. Lots of pinball parts can be ordered cheaply from Competitive Products Corp (800-562-7283) too. They have great prices on fuses, plunger & links, coil stops, EOS switches, flipper link spacer bushings, barrel springs, pinballs, optos, bridge rectifiers, etc. All other parts (especially game specific parts) and schematics should be ordered from Steve Young's Pinball Resource (845-473-7114 or mailto:PBResource@idsi.net?subject=from_the_Sys11_Repair_Document), or in Europe from Pinball Heaven at mailto:Phil@pinballheaven.co.uk?subject=from_the_Sys11_repair_document.

There are essentially four different generations of the Williams system 11 CPU board. You will need to know which generation you have, because components and circuit boards change with each generation. The differences in the four generations has mostly to do with the sound. With each new generation of system 11, the sound became more complex. This required components of the sound to move to a separate sound board. In the final version of system 11 (C), nearly all the sound circuitry is removed from the CPU board and moved to the sound board.
• System 11: first generation of system 11.
• System 11A: second generation of system 11. System 11a boards can be used in system 11 games too.
• System 11B: third generation of system 11. Actually there were two version of System 11B boards, with the first version having the sound amplifier at U1 (a TDA2002). Special solenoids now CPU controlled and games have Auxiliary power driver board (actually these both started with "Big Guns, the last system 11a game).
• System 11C: fourth generation of system 11. System 11c boards can only be used in system 11c games because all sound circuits have been removed from the CPU board. There are no ROMs at U21 and U22, and most of the circuitry from the top left corner of the board has been moved to the sound board.
The most flexible CPU is system 11b. This board can be used in system 11, 11a, 11b or even 11c. To use a system 11b board in a system 11c game, you just don't use connectors 1J16 (volume control) and 1J15 (speakers) on the system 11b board. Also the sound ROMs at U21 and U22 are not used, since they are moved to the sound board.

Changing CPU boards amoung Early System 11 games.
High Speed, Grand Lizard and Road Kings do not use ground at the CPU connector 1J18, pins 6,7. If you try and use this older System 11 CPU board in a newer System 11A game (not recommended), you will have to run a ground wire to connector 1J18 pins 6,7. Otherwise, your special solenoids will not work.

System 11 CPU board.
Part number D-10881. Uses a 7 segment LED on the CPU board to display the game's diagnostic codes. This version of system 11 contains the amplifier circuit for the sound board. It also has a complete, but unused opto switch circuit.

System 11A CPU board.
Part number D-11392. Uses 3 LED's to replace the 7 segment LED for the game's diagnostic code display on the CPU board. The special solenoid circuit is changed; jack 1J18 now has ground connected to pins 6,7. Also zener diodes ZR3-ZR8 (1N5234, 6.2 volts) were added. Finally jumpers W16, W17 were added to ground pin 38 of the 6802/6808 microprocessor U24. If a Motorola microprocessor is used, W16, W17 must be connected. If any other brand of microprocessor was used W16, W17 must not be jumpered.

System 11B CPU board.
Part number D-11883-xxx (where xxx is the game number). The first phase of system 11B had the opto switch circuit and SRC6 removed. Also the sound amplifier circuit at U1 was removed. Phase two of system 11B had the layout and type of switch circuit changed. Also Q42-Q49 changed from two rows of four transistors to a single row of eight transistors, and were changed from 2N3904 to 2N5550.

System 11C CPU board.
Part number D-11883-xxx (where xxx is the game number). Note this is the same CPU part number as system 11B! But system 11C has eliminated the sound circuit entirely. All audio and sound now processed on the sound/audio board. Because of this, the easiest way to tell you have a system 11C CPU board is if there is no sound EPROMs at positions U21 and U22 (these were moved to the sound board for system 11C).

Score Displays Used in System 11 Games.
The score displays uses in System 11 games varies. Initially (High Speed to Millionaire), Williams used five score displays: two 7 character alpha-numeric displays, two 7 character-7 segment numeric displays, and one four character numeric display (for the credits and ball in play). Starting with F-14 Tomcat, Williams dropped the 4 character credit display, and all four display glasses were now mounted on a single circuit board. The software now displayed credits and ball in play in the four displays (this saved some production costs). Then when Taxi came out, Williams switched to using two 16 character alpha-numeric displays.

Williams Schematics for System 11 Games.
Interestingly, Williams often didn't print their system 11 game manual schematics with the correct system 11 board! For example, many system 11c games had system 11b schematics printed in their manuals instead. For example, the Diner game manual has system 11b schematics, even though it's a system 11c game. There is usually a note at the bottom of the schematics about the sound section of the board that says, "removed in certain assemblies" to signify this. Keep this in mind when reading the schematics.

Williams System 11 High Speed, 1/86, #541 Does not use multiplexing, five score displays. Alley Cats, 2/86 This is a Bowler, not a pinball game, but uses system11 boards. Grand Lizard, 3/86, #523 Does not use multiplexing. Road Kings, 7/86, #542. First game to use a Yamaha YM2151 sound chip on the sound board. Williams System 11a Pinbot, 10/86, #549 Millionaire, 1/87, #555 F-14 Tomcat, 3/87, #554. First game with four 7 character score displays. Also first game with the new FL11630 parallel wound flipper coil, which used two flipper diodes (instead of one). Fire!, 8/87, #556 Big Guns *, 10/87, #557. First game to have Auxiliary power driver board and Special solenoids CPU controlled. * System 11b started in the middle of "Big Guns" production. So "Big Guns" can have either System 11a or 11b boards. System 11b Big Guns *, 10/87, #557. First game to have Auxiliary power driver board and Special solenoids CPU controlled. Space Station, 1/88, #552 Cyclone, 2/88, #564 Banzai Run, 7/88, #566. First game with an interconnect board, but the interconnect board used on this game is unique. Swords of Fury, 8/88, #559 Taxi, 10/88, #553. First game with only two alpha-numeric 16 character displays, new power supply D-12246. Jokerz, 1/89, #567. This game only used a special stereo sound board with different sound board power requirements and cabling. Earthshaker, 4/89, #568 Black Knight 2000, 6/89, #563 Police Force, 9/89, #573 Transporter the Rescue (Bally), 6/89, #2630 Elvira and the Party Monsters (Bally), 9/89, #782 Bad Cats, 12/89, #575 Mousin' Around (Bally), 12/89, #1635 Whirlwind, 4/90, #574 System 11c Game Show (Bally), 4/90, #985 Roller Games, 5/90, #576 Pool Sharks (Bally), 6/90, #1848 Diner, 8/90, #571 Radical (Bally), 9/90, #1904 Riverboat Gambler, 10/90, #1966 Bugs Bunny Birthday Ball (Bally), 11/90, #396 Dr.Dude (Bally) *, 11/90, #737 About 100 Dr.Dude games were made with the new WPC system boards.

System 11 uses a combination CPU and driver board (known as the "CPU" board). It contains all the logic and TIP122/102 driver transistors for the game. Starting with "Big Guns", an Auxiliary power driver board was added which houses another eight TIP36c transistors for high voltage applications (but these TIP36c transistors are pre-driven by one of the existing TIP122/102 transistors on the CPU board).

Board/Connector/Pin Numbering.
A prefix number preceeds all connector "J" numbers. This prefix signifies which board the connector belongs to. The number immediately after the "J" is the connector number for that board. The number after a hyphen is the pin number for that connector. For example, connector 1J8-5 would be CPU board connector 8, pin 5. Here are a list of board number prefixes:
• 1 = CPU board.
• 2 = Interconnect board (Banzai Run and later).
• 3 = Power Supply board.
• 4 = Master Score Display board.
• 5 = Auxiliary power driver board (Big Guns and later), or Slave display board on early games.
• 6 = Backbox wiring
• 7 = Cabinet wiring
• 8 = Playfield wiring
• 9 = Insert board.
• 10 = Sound board.
• 11 = Audio board.
• 15 = Flipper power supply board (Fire! and before).

Switched Solenoids (Multiplexing).
The basic concept of system 11 is the use of a switched solenoid ("multiplexing") design. Solenoids 1 to 8 have two banks: the "A" and "C" banks. This allows one TIP122/102 transistor to control two functions (usually multiplexed between a solenoid and a flasher). The eight bank selected TIP122/102 transistors can control 16 functions. A bank select relay controls which of the two functions any of the eight driving transistors control. The "A" bank consists primarily of coils. The "C" bank consists primarily of flasher lamps. Not all games use the multiplexing technique. High Speed and Grand Lizard (the first two system 11 games) do not multiplex. The games after Grand Lizard however required more driver transistors, and multiplexing was used to allow this.

Multiplexing works like this; when the bank select relay is de-energized, solenoid power is connected to bank "A". Then only solenoids 1A to 8A can be driven by the driver transistors. There is no power available to bank "C". The "A" bank is usually reserved for coils.

When the bank select relay is energized, solenoid power V+ is connected to bank "C". Then only solenoids 1C to 8C can be driven by the driver transistors. There is no power available to bank "A". The "C" bank is usually reserved for flash lamps.

Norbert Snicer's description of System 11 multiplexing. Note the solenoid power V+ on the left is directed to either bank A (top) or bank C (bottom) by the bank select relay, through transistor Q8 (or Q7 on earlier system 11 and 11A games).

Controlled Solenoids.
There are also eight "controlled solenoids" on system 11 games, in addition to the above "switched" solenoids. These are solenoids 9 to 16. These can control only one device (unlike the switched solenoids which are multiplexed). Note if your game doesn't use the above solenoid bank switching (like High Speed and Grand Lizard only), all solenoids are considered "controlled" solenoids.

The Six Special Solenoids.
Williams' ROM software originally did not have CPU control of "special solenoids". These six solenoids includes the pop bumpers, kicking rubbers (slingshots), and kickback solenoids, and sometimes other coils. The original theory behind this was these items needed instant response. Having them controlled by the CPU would add enough of a delay to slow the solenoids down. After all, the CPU had to sense a switch closure of a pop bumper, then turn on a transistor which would fire the pop bumper coil. All this while the CPU was doing all the other chores it does (like scoring and controlling other devices). It was thought that this would not happen fast enough for good game play.

The down side to this was when a pop bumper switch was stuck on, the coil would "machine gun" (quickly pulsing on and off), and eventually either burn the coil or blow a fuse. On early system 11 games, the coils may not "machine gun", but instead may just lock on and burn the coil. This system also required a redundant switch, connected to the switch matrix for each coil, which controlled the scoring for this device. Also each special solenoid had to have its own fuse.

CPU Board Connector 1J18 (Special Solenoid Switches)
If your system 11 CPU board has no connector at plug 1J18, the special solenoids are CPU controlled. This connector is used for the "special switches" which control the special solenoids on games Fire! and before. This connector is no longer used on games Big Guns and later, because the special solenoids are now CPU controlled.

50 volt Coils in Early System 11 Games.
Two different solenoid voltages were used in earlier system 11 games: +25 and +50 volts. The CPU board was not able to handle both voltages, it could only handle the lower 25 volts. To accommodate the higher 50 volt coils, a small relay board was located under the playfield to drive the 50 volt coils. The CPU board's TIP122/102 transistor would activate the 25 volt relay on the relay board. This would turn on the 50 volt coil. The relay is really acting like a mechanical version of a TIP36 transistor (which was later used instead of the relay).

Robert Snicer's drawing of how early system 11 games handled the higher voltage 50 volt coils, using a under the playfield relay board.

Power Supply board.
The power supply board provides +5 volts for all circuit boards. It also produces the +100 and -100 volts for the score displays. It also acts as a liaison for the +18 volts for the lamp matrix (no circuit, just a fuse) and the general illumination (GI) on games before Banzai Run. The power supply board does some mild processing of the solenoid voltage too.

There were basically four different system 11 versions of the power supply. The first version was D-8345-xxx (where xxx is the game number). This was used from High Speed to Swords of Fury. On these power supplies there are three different sub-versions of this board, all with the same prefix (D-8345) number:
• High Speed to Fire! (no Auxiliary power supply board, no Interconnect board): has GI connectors and GI relay on the power supply board.
• Big Guns, Space Station, Cyclone (Auxilary power supply board, no Interconnect board): has GI connectors, but no GI relay (moved to the Auxiliary power supply board).
• Banzai Run, Swords of Fury (Auxiliary power supply board, Interconnect board): no GI connectors (moved to the Interconnect board), no GI relay (moved to the Auxiliary power supply board).

Starting with Taxi, a new power supply was used, number D-12246.

Low +5 volts from the Power Supply board.
A low +5 volts coming from the power supply can often be attributed to the 47 mfd 50 volt capacitor at C8. If this cap fails, a low +5 volts will result. If the large filter cap C10 (18,000 mfd 20 volts) wears out, this can cause low or bad +5 volts also.

System 11's Auxiliary Power Driver board.
Starting with Big Guns, system 11 games had an additional "auxiliary power driver" (APD) board. This board was used to hold the:
• Bank select circuit and bank select relay.
• Bridge rectifiers that supply the solenoid power (previously these bridges were just bolted to the back of the backbox).
• Driver transistors (TIP36) for the 50 volt devices. This eliminated the small relay boards under the playfield. Up to eight TIP36c transistors can be used on this board. But if a game didn't use all eight, only the number used was actually installed!
• Coil diodes. The coil diodes were no longer mounted on the coils themselves, but were instead installed on this board. This eliminated diodes breaking off the coils due to vibration. It also simplified coil replacement, as the operator no longer had to worry about which coil lead the diode's band was attached to on the coil.
• Solenoid fuses. The 50 volt solenoid fuses were mounted on this board.
With the addition of the auxiliary power driver board, the backbox became much neater.

Zero Ohm "Resistors" on the Auxiliary power driver board.
On many of the games with the new Auxiliary power driver board, Williams used zero ohm resistors as jumpers on this board. The reason they used these "resistors" was they could be automatically installed into the circuit boards with production machines before being wave soldered. Unfortunately, sometimes these zero ohm resistors fail and go open. For this reason, system 11 games used actual wire jumpers instead of these zero ohm resistors. Check W1, W3, W4 and W6 for open zero ohm resistors on the APDB.

The Interconnect Board.
Starting with Banzai Run, Williams started using an "interconnect board" inside the backbox (note the Banzai Run interconnect board is unique to other interconnect boards). Often this long, skinny board was mounted beneath the CPU board, or on the sides of the backbox. This board was a "truck stop" for lamps (GI, controlled, flashers), switch matrix, and coil power on the game. The lamp GI (general illumination) wiring from the playfield would come here, go through some fuses, and then continue on to the CPU board. This board also held the resistors for the flash lamps. At this time Williams dropped resistor R1 from the flash lamp circuit and only used R2 on the interconnect board. This greatly increased reliability because flash lamp resistor R1 (330 ohms 7 watts) failed quite often. The interconnect board also holds several MOC3010 opto-couplers for the flipper lane change circuit (games before the interconnect board did lane changes with a second switch on the flipper cabinet switch).

Flipper Power Supply board.
All system 11 games, Fire! and before, have a small flipper power supply board to the right of the CPU board. This board was basically a fuse, a bridge rectifier, a resistor, and a few capacitors. It was used to provide power to the flipper coils. When the Auxiliary power driver board (APDB) was introduced in Big Guns, this board was combined into the APDB.

 

Flipper Differences.
Flipper coils are actually two coils in one package. The "high power" side is a few turns of thick gauge wire. This provides low resistance, and therefore high power. The "low power", high resistance side is many turns of much thinner wire. This side of the coil is important if the player holds the cabinet switch in, keeping the flipper coil energized. The high power low resistance side of the coil is only active when the flipper is first energized. But when the flipper is energized and at full extension, the low powered side of the flipper coil is used so the coil doesn't get hot and burn.

Flipper worked different on games High Speed to Millionaire. These games used a series wound FL23/600-30/2600 flipper coil. The common lug (where both the low and high powered coil wires were connected together) on these flipper coils was the middle of the three lugs. Also these coils used ONE diode across the two outside lugs. The EOS switch on these games, when opened, enabled BOTH the high power and low powered coils together. This style of flipper coil did NOT use a 2.2 mfd anti-spark EOS capacitor. The problem with this series wound coil was the "back spike" of current that occured when the EOS switch was opened. This cause the EOS switch to excessively wear and pit.

With the introduction of F-14 Tomcat, Williams changed to the parallel wound FL11630 style flipper coil. This coil now used an outside lug as the common lug (where both the low and high powered coil wires were connected together). Also TWO diodes were used and required on these flipper coils. This parallel wound coil eliminated the "back spike" of current when the EOS switch opened. It also allowed the use of a 2.2 mfd 250 volt capacitor to further limit EOS switch sparking and pitting. Now when the EOS switch opens, this removed the high powered side of the coil from the circuit. The low powered side of the flipper coil is always in the circuit, but is essentially ignored when the high powered side is in the circuit. This happens because the current takes the easiest path to ground (the low resistance, high power side of the coil). The low power high resistance side of the flipper coil won't get hot if the player holds the flipper button in.

The CPU Board Flipper Relay K1.
The flippers are only enabled during game play and in diagnostic mode. The flipper enable relay is what turns the ground connected to the flippers off and on. This enable relay is located on the CPU board at K1, and is a 4P, 40 ohm, 6 volt relay. When you enter diagnostic mode, you should hear the flipper relay K1 click on (activating the flipper buttons).

Norbert Snicer's drawing of the flipper circuit used from F-14 and later. Notice the CPU board relay K1 that energizes the flippers during a game.

Check every fuse! Seems like such a simple thing, yet many of us forget to do it. Before you even turn the game on, check the fuses. Not only look for blown fuses, but especially over-fused circuits. For example, is there an 8 amp fuse where there should be a 5 amp? Is there a slow blow fuse where there should be a fast blow?

Most of the fuses for these games are located in the backbox.

Testing Fuses: the Right Way.
Don't depend on your eyes or sense of smell to check fuses. A perfectly good looking fuse could be blown, it happens all the time. Use your Digital Multi-Meter (DMM). First remove the fuse from its holder, (or remove just one end of the fuse from the holder). Don't try and test the fuse installed as it can give false readings, depending on the circuit. Set your DMM to "continuity", put a lead on each end of the fuse, and buzz out those fuses. No buzz means fuse is bad.

(Side Note: a "buzz" on your meter means zero resistance. If you don't get a "buzz", either the circuit is OPEN, or the resistance is 100 ohms or greater. If your meter doesn't have a continuity function, just use the lowest resistance setting. A good fuse will measure zero ohms.)

Another Reason to Pull a Fuse from its Holder to test it.
Always remove a fuse from its holder to test it. Do this because a particularly fatigued fuse will often fall apart as you take it out of its holder. You may never see this if the fuse is tested in its holder. This is especially true if the fuse tests 'good' then the fuse wire pulls away from an end-cap as it heats up.

A blown fuse: where did it blow?
If you look at a blown fuse, most often it's blown in the middle of the fuse. This is where a fuse should blow, and indicates the fuse was doing its job (protecting an overloaded circuit). But if the fuse has blown at either end of the fuse, this could indicate another problem; a bad fuse holder. Keep this in mind, and examine the blown fuses you remove. If the fuse blew at either end, maybe you should replace its fuse holder too.

Adding Fuses to System 11 games Fire! and before.
Williams made a design error on games before Fire!. They forgot to add a fuse going from the transformer to the bridge rectifiers powering the +25 volts for the solenoids, and the +18 volts for the lamp matrix. If either of these bridges shorts, or capacitors that smooth the voltages fails, you game could start on fire (no joke!). This has happened, so it is recommended that you add fuses.

It is very easy to modify your game (Fire! and before) and install these fuses. Just buy two fuse blocks at Radio shack. Then find the two bridges mounted on the inside of the backbox. There should be a lead on the bridge that is labeled "AC". Remove the wire going to this lead, and connect it to one lead of a fuse block. Connect the other lead of the fuse block back to the bridge. Do this for both the +25 volt solenoid voltage bridge, and for the +18 volt lamp matrix bridge. Install 8 amp slow blow fuses. Note some bridges will have both "AC" leads labeled. You can connect the fuse to either of these two "AC" leads.

Fuse Locations in System 11 games.
Though the following list will not apply to all system 11 games, here are the fuse types and locations of a typical system 11 game. All fuses are the slow-blow variety. Also there are probably other fuses in the backbox not located on circuit boards (for example on pre-Banzai Run games the general illumination fuses are located on fuse blocks inside the backbox).

Power Supply board.

• F1 = 1/10 amp. Earlier games score display voltage.
• F1 = 1/4 amp. Earlier games score display voltage.
• F1 = 3/8 amp. Score display voltage.
• F2 = 1/8 amp. Score display voltage.
• F2 = 2.5 amp. Earlier games +34 volt solenoid voltage.
• F3 = 1/8 amp. Score display voltage.
• F3 = 8 amp. Earlier games +18 volt lamp matrix power.
• F4 = 7 amp. -12 volts.
• F5 = 7 amp. +5, +12 volts.

Auxiliary Power Driver Board (Big Guns and later).

• F1 = 5 amp (slingshots)
• F2 = not used
• F3 = 2.5 amp (pop bumpers)
• F4 = 2.5 amp
• F5 = 2 amp (right flipper)
• F6 = 2 amp (left flipper)
• F7 = 4 amp (flipper bridge main power)
• F8 = 7 amp (special solenoids main power)

Interconnect Board (Swords of Fury and later).

• F1 = 5 amp (general illumination)
• F2 = 5 amp (general illumination)
• F3 = 5 amp (general illumination)
• F4 = 5 amp (general illumination)

Flipper Power Supply Board (Fire! and before).

• F1 = 5 amp (flipper bridge main power)

Often you'll get a new game, turn on the power and the general illumination (GI) lights don't work. The whole game is somewhat dark. This can be caused from burned GI connectors.

The GI connectors can get hot and fail. This happens because the Molex connectors don't always have enough surface area to handle the GI power requirements. The heat from the connector will cause the solder joints to fatigue which causes resistance (and more heat). The connector pins get so hot they soften the solder. All this causes more resistance, which causes more heat. It doesn't end till the board burns, the fuse heat fatigues and fails, or the connectors pins fall out (or burn!), and open the circuit.

The GI connectors on the Interconnect board, for games
Banzai Run and later. Note connector 2J6 on the far right
with the yellow wires will be the one that is most likely
to burn on this board.

The Interconnect board and the GI.
Later system 11 games (Banzai Run and after), use an interconnect board which also "turns around" the GI power. These GI connectors 2J6, 2J7, 2J9, 2J10 on the interconnect board can also burn. The input GI connector at 2J6 will probably be the one that burns, but the output GI connectors at 2J10 (cabinet, coin door), 2J9 (playfield) and 2J7 (backbox) can also burn.

Fixing a Burnt Connector.
Fixing a burnt connector requires more than just replacing the connector! You also need to remove the board and replace the male pins. In the short run, you can sand clean and tin the old pins with solder, and re-solder them to the board. But since the original plating is burned off the pins, they will re-tarnish quickly, and the problem will re-occur. If you only replace the connector and don't replace (or minimally clean and tin) the board pins, the resistance will still be there (from the cold or fatigued solder joints and dirty pins). The new connector will burn in short order.

When replacing the Male Header pins...
When you replace the circuit board male header pins for the GI, it's a good idea to solder the pins on BOTH sides of the board. The traces on top of the board will be a bit tricky; you may have to suspend the header pins up a bit to get your soldering iron between the board and the pins. But it's a good idea to solder them on both sides of the board to get the best connection.

A crimping tool (top), two different types of pins (left),
and a new connector housing and male pins. Note the connector
pins; the far left two pins are the crimp-on, single wiper type. The
two pins on the right are insulation displacement pins, but with
two wipers. It's ideal to use the crimp-on style pin, but with
two wipers (not shown).

If your game is getting home use, you can probably replace the burnt GI connectors with the white low temp versions. You can probably get away with cleaning and tinning the board pins. These may burn again however after extended use. If you are operating your game (where it's powered-on for hours and hours), you should replace the connectors with the black hi-temp Molex connectors (available from a Williams distributor or Pinball Resource).

Crimp-On Pin Connectors vs. Insulation Displacement Connectors (IDC) Plugs.
Insulation displacement connector (IDC) plugs are very convenient for an assembly line or automated procedure to install. No wire stripping is needed, the wire is just pushed onto the "V" in the pin, which cuts (displaces) the insulation to make contact with the wire. But they aren't very good in the long run. Many problems with games are attributed to these IDC plugs. A far better connector uses the crimp-on style of pin. You'll need a special tool to crimp them, but the reliability will be much higher. Only use crimp-on pin connectors when replacing burnt ones.

Trifurcon Connector Pins.
Molex makes a crimp-on .156" size female terminal pin called a "trifurcon" pin (not available in the .100" pin size). This style .156" pin differs than the "normal" pin; the metal material is more heat resistant, and it has three wiper contacts instead of just one. The more contact points means the female pin "hugs" the male header pin with greater surface area. I highly recommend these. They are available from Digikey (800-344-4539 or http://www.digikey.com/). You can also view the specs for these pins at http://www.molex.com/product/pcb/6838.html. Compares these to the "normal" connector pin specs at http://www.molex.com/product/pcb/2478.html.

Note Molex sells these pins in "strips" or on a "reel". Do NOT buy connector pins this way! Always buy them in "bags" (separated). It's just too difficult to cut them when they are in strips. If you don't do a good job cutting them, they won't insert into their plastic housing correctly. Also always get the tin plated version, NOT the gold plated pins.

• .156" Trifurcon pins (three wipers): Digikey part# WM2313-ND (Molex part# 08-52-0113, for 18 to 24 gauge wire). Price is $1.02 for 10, $8.50 for 100.
• .156" tin pins (one wiper): Hosfelt (800-524-6464) part# 08-50-0106, for 18 to 24 gauge wire). Price is $0.06 each.

Board Mounted Header Pins.
These are available in several styles. Get the most number of pins available, and cut the header to the size you need. They also come with a "lock" and without a lock. The lock variety is what you'll use the most.

• .156" header pins with lock (12 pins): Hosfelt (800-524-6464) part# 26-48-1125, $0.94 each.
• .156" header pins with no lock (12 pins): Hosfelt (800-524-6464) part# 26-48-1121, $0.70 each.

Connector Housings.
Sometimes you'll have to replace the plastic connector housing too if it is burnt, in addition to the pins within the housing. Get the most number of pins available, and cut the connector to the size you need.

• .156" white housings (12 pins): Hosfelt (800-524-6464) part# 09-50-3121, $0.79 each.
• .156" black hi-temp housing: Williams part #5792-13384-xx. The "xx" is the number of pins for the housing from "02" to "18".

Polarized Pegs.
A polarized peg is a small nylon plug that go into the connector housing so the housing is "keyed" (you can't plug it into the wrong board header pin connector). I highly recommend using these if you replace a connector housing.

• .156" polarized peg: Hosfelt (800-524-6464) part# 15-04-0220, $0.13 each.

Whenever I get a new system 11 game, before I ever turn it on, I test all the TIP122/102 solenoid transistors. I do this because I'm already in the backbox (examining the fuses and the GI connectors), and a blown transistor can really confuse a system 11 game. This is the procedure I use, and it takes about 20 seconds to test all the TIP122/102 transistors:
• Make sure the game is off.
• Put your DMM (digital multi meter) on ohms (buzz tone).
• Put one lead on the ground strap in the backbox.
• Touch the other lead to the metal tab on the TIP122/102 transistors. These are the 16 transistors at the lower left side of the CPU board, the six transistor at the upper right, and the eight transistors at the far lower right of the CPU board in a vertical row.
• If you get zero ohms (buzz), the transistor is bad! (shorted on)

I replace the bad TIP122 transistor(s) with a more robust TIP102 immediately before I turn the game on. I also usually replace the associated pre-driver 2N4401 transistor too.

This is a very common question. After all, arcades leave their games on almost continually with minimal damage (that you know of!). So why not do it with your game at home?

Although commercial pinball machines can handle being powered on continually, I would recommend you do not leave your games turned on when not in use. Here are some reasons:

• Electronic score displays on your game have a limited life, which is proportional to how much time they have been turned on.
• General illumination circuits will be stressed. Burnt pins and connectors are very common on games that are on for extended periods of time.
• Light bulbs don't last forever, and aren't all that easy to change on a playfield.
• The bulbs, displays, fans, and transformers only attract dirt when they are on. Leaving your game on means sucking dirt out of the air and depositing it into your machine.
• Heat generated by the general illumination lamps can warp playfield plastics or help delaminate backglass paint.
• Electricity is a precious resource. Conserve it! An electronic game from this era consumes about 4 amps in attract mode. So leaving your game on is like running a 240 watt light bulb. By comparison, an entire stereo system plus a television use about the same amount of power.

Leaving your pin on all the time can cost much more than any potential damage you could do turning it off and on as you need it.

If you have found a bad component, now comes the hard part; replacing it! Transistors, bridge rectifiers, and most chips are not socketed. They are soldered directly into the driver board. Care must be taken when replacing a bad component.

Please see http://marvin3m.com/begin for details on the basic electronics skills and tools you will need when replacing circuit board components.

When replacing components, the object is to subject the board to the least amount of heat as possible. Too much heat can lift or crack the board's traces. Too little heat and you can rip out the plated-through holes when removing the part. New circuit boards are too expensive to replace. So you must be careful when doing this.

To remove a bad component, just CUT it off of the board, leaving as much of its original lead(s) as possible. Then using needle nose pliers, grab the lead in the board while heating it with your soldering iron, and pull it out. You can clean up the solder left behind with a desoldering tool.

When replacing chips, alway install a socket. Buy good quality sockets. Avoid "Scanbe" sockets at all costs! A good machine pin socket is desirable.

There are basically four types of transistors used on a system 11 CPU board:
• TIP122: used for transistor Q69, Q71, Q73, Q75, Q77, Q79 (special solenoids), Q81-Q87 (lamp return rows), Q22-Q25 and Q30-Q33 (multiplexed solenoid drivers), Q6 (coin lockout relay), Q7 or Q8 (bank select relay), Q9 and Q14-Q17 (miscellanous devices). These transistors are used to control all solenoids and flashers. When replacing a TIP122 on a system 11 game, always replace it with a TIP102 instead. The TIP102 is a more robust version of the TIP122. Equivalent transistors include TIP122 = NTE261, TIP102 = NTE2343.
• TIP36c: used for transistor Q1-Q8 on the Auxiliary power driver board (if your game is earlier than Big Guns, you do not have this board, and hence do not have any TIP36c transistors). These transistors control the high voltage 50 volt coils that were previously controlled by under-the-playfield relay boards. NTE393 is an equivalent transistor.
• 2N4401: Q2-Q5, Q10-Q13, Q18-Q21, Q26-Q29, Q34-Q38, Q41, Q67-Q68, Q70, Q72, Q74, Q76, Q78. Used as a pre-driver for all the TIP122 transistors. NTE123AP is an equivalent transistors.
• TIP42: Q52, Q54, Q56, Q58, Q60, Q62, Q64, Q66. Used to control the lamp matrix columns. The TIP42 switches the +18 volts on for any particular lamp column. NTE197 is an equivalent transistor.

The Bank Selected Solenoids.
On all System 11 games, transistor Q7 or Q8 controls the "solenoid A/C select relay". This is the relay that controls which bank (either "A" or "C") that transistors Q22-Q25 and Q30-Q33 will control. This means one transistor can control two different devices (usually a flasher on bank C, and a solenoid on bank A). Note if your game is pre-Big Guns (no Auxiliary power driver board), transistor Q7 controls the solenoid A/C select relay on the power supply board. If your game is Big Guns or later (with an Auxiliary power driver board), than Q8 controls this relay on the Auxiliary power driver board. The solenoid A/C select relay is a 24 volt DC, 10 amp, DPDT relay.

To make things even more confusing, some System 11 games do not utilize the solenoid A/C select relay. For example, the first two system 11 games (High Speed and Grand Lizard) do not. There are enough transistors on the CPU board so there is no need for any transistors to be shared between two devices. In this case transistor Q7 is used for a kickback lane (on High Speed) and the A/C select relay is present (but not used).

First Test the Solenoid A/C Select Relay!
If the solenoid A/C select relay is not working correctly, you will have all kinds of coil problems. A messed up A/C relay, if stuck on bank "C", won't give any power to coils 1 to 8. If the relay is constantly energized (stuck on bank "C"), it's probably because it's driver transistor (either Q7 or Q8) is shorted. If it's stuck on bank "A" (where the relay sits at rest) or won't energize, the flashlamps in the game won't work.

I recommend the first thing you do is to test the solenoid A/C select relay. To do this, take your aligator test wire and connect it to the metal tab on transistor Q7 (Fire! or before) or Q8 (Big Guns or later). Then with the game on and in attract or diagnostic mode, touch the other end of the aligator clip to the ground strap in the backbox. You should hear the A/C select relay click on and off on the power supply or Auxiliary power driver board.

If you don't hear the relay "click", you should now test transistor Q7/Q8. The quick and easy way to do this is:

• Turn the game off.
• Put your DMM on ohms (buzz tone).
• Put one lead on the ground strap in the backbox.
• Touch the other lead to the metal tab on transistor Q7/Q8.
• If you get zero ohms (buzz), the transistor is bad! (shorted on)

Is the Solenoid A/C Select Relay Bad?
Be aware that relays can go bad too. This can especially happen if transistor Q7/Q8 locks on for some time, and leaves power to the relay turned on. The relay can actually get so hot, it burns the relay contacts together. Also, the solder joints on the A/C select relay can go "cold" or fatique too. This often will make an A/C select relay not work (but reflowing the relay solder joints can often fix this). If you need to replace the A/C select relay, it's a 24 volt DC, 10 amp, DPDT relay.

Turning on Relay A/C to test both coils/flashers that driver
transistors Q22-Q25 and Q30-Q33 control. Here transistor Q8's
metal tab is grounded with an alligator clip.

Special Solenoids.
If you are having problems with the special solenoids, keep this in mind. Since games before "Big Guns" use hardware logic to fire the solenoids, there are some other smaller (and easily damaged!) components that can fail too. Check capacitors C70 to C75 (.01 mfd), and resistor network SR20 (4.7k). If these become damaged, a special solenoid can "stick on". Even if your game is Big Guns or later (CPU controlled special solenoids), damage to these components can cause special solenoid problems.

Transistor Testing procedures, circuit board out of the game.
If you have a circuit board out of the game for some reason, I would suggest testing all the solenoid/flasher driver transistors. It only takes a moment, and will ultimately save you time.

To test a transistor, you'll need your digital multi-meter (DMM) set to the "diode" position.

• TIP122/102: Put the black lead of your DMM on the center lead or on the metal tab of the transistor. Put the red lead of your DMM on each of the two outside legs of the transistor. You should get a reading of .4 to .6 volts. Any other value, and the transistor is bad and will need to be replaced.

Testing a TIP36c on the Auxiliary power driver board.

• TIP36c: Put the red lead of your DMM on the center lead or on the metal tab of the transistor. Put the black lead of your DMM on each of the two outside legs of the transistor. You should get a reading of .4 to .6 volts. Any other value, and the transistor is bad and will need to be replaced.

Testing a 2N4401 pre-driver on the CPU board.

• 2N4401 (pre-drivers): Put the red lead of your DMM on the center lead of the transistor (note this transistor doesn't have a metal tab). Put the black lead of your DMM on each of the two outside legs of the transistor. You should get a reading of .4 to .6 volts. Any other value, and the transistor is bad and will need to be replaced.

Testing a TIP42 lamp matrix column driver transistor on the CPU board.

• TIP42: Put the red lead of your DMM on the center lead or on the metal tab of the transistor. Put the black lead of your DMM on each of the two outside legs of the transistor. You should get a reading of .4 to .6 volts. Any other value, and the transistor is bad and will need to be replaced.

Most often transistors short when they go bad. This will usually give a reading of zero or near zero, instead of .4 or .6 volts.

Testing Transistors/Coils, circuit boards installed in a (near) WORKING game, using the Diagnostics Test.
If your game powers on, you can use the diagnostics to test most devices. From the attract mode:
• Press the center red button inside the coin door to the "down" position.
• Press the black button closest to the coin door once.
• Press the center red button inside the coin door to the "up" position.
• Press the black button closest to the coin door to move from test to test.

Solenoid Doesn't Work during Diagnostic Tests.
If a solenoid doesn't work from the diagnostic tests, here's what to check. Turn the game off before doing this.
• Check all the fuses. A non-working solenoid could be as easy to fix as just replacing a fuse.
• Find the solenoid in question under the playfield. Make sure the wire hasn't fallen off or become cut from the coil (a very common problem).
• If the above is correct, make sure the windings of the coil haven't broken off from the solder lugs. If one has broken, you can re-solder it. Make sure you sand the painted enamel insulation from the wire before re-soldering.
• Check the coil diode. For games before Big Guns, the coil diode will be right on the coil, with the banded side of the diode connecting to the power side of the coil. For games with an Auxiliary power driver board (Big Guns and later), the coil diodes are mounted on the auxiliary power driver board (flipper coils should always have diode(s) though, for all system 11 and WPC games). Moving the diodes away from the coil increases reliability as the diode is not subject to the jarring and heat a coil can produce. It also eliminates the need for the operator to know which coil wire goes to the banded side of the diode when replacing a coil!

A Coil doesn't Work, What To Do.
The following procedures will start at the coil, and work back to the CPU board, testing components. This will eliminate things and make finding the problem easier.

Testing for Power at the Coil.
Most pinball games (including system 11) have power at each and every coil at all times. To activate a coil, GROUND is turned on momentarily by the driving transistor to complete the power path. Since only ground (and not power) is turned on and off, the driving transistors have less stress on them. With this in mind, if we artificially attach a coil to ground, it will fire (assuming the game is turned on and in attract mode).

• Turn the game on and leave it in "attract" mode.
• Lift the playfield.
• Put your DMM on DC voltage (100 volts or greater).
• Attach the black lead of your DMM to the metal side rail.
• Touch the red lead of your DMM on either/both/all lugs of the coil in question.
• You should get a reading of 25 to 80 volts DC. Switch your red test lead to the other lug of the coil, and you should get the same voltage again. On flipper coils, test all the lugs of the coil for power. If you don't get any voltage reading, no power is getting to the coil. If you don't get power at all lugs, then you have a broken winding on the coil itself. Replace the coil or fix it (if the winding is an outside winding, you can remove the paper label and unwrap a turn of wire, sand the insulation off, and resolder the coil winding to the lug).
• If no power is getting to the coil at any lug, it may be a coil that is A/C relay selected. Push the center red coin door button down, and press the black button closest to the coin door. This will put the game in diagnostics mode. This should de-energize the solenoid A/C relay, and turn the power to the coil in question on. If there is still no power, put an aligator clip on the metal tab of transistor Q7 (Fire! and before) or Q8 (Big Guns or later) to activate the solenoid A/C relay, and retest for power at the coil again.
• A broken solenoid A/C relay can cause power to not get to a coil. But this will affect more than one coil. Cold solder joints on the A/C relay-to-board solder pads can do this too.
• If no power is getting to the coil, a wire is may be broken somewhere. Trace the power wire. Remember, the power wires are "daisy-chained" together. So if there is a break in the wire at a previous coil, the coils down stream will not get power.

Coil Test to Make sure Coil is Good.
Here's another method of testing coils, which is more "low-level". This will test if the coil itself is good, and that there is power at the coil.

• Game is on and in "attract" mode, and the playfield lifted.
• Connect an alligator clip to the metal side rail of the game.
• Momentarily touch the other end of the alligator clip to the GROUND lead of the coil in question. This will be the coil lug with the single (thinner) wire attached. On coils with a diode, the ground coil lug is the one with the non-banded side of the diode connected. On FL11630 flipper coils F-14 Tomcat and later, touch the middle lug to ground.
• The coil should fire (if you accidentally touch the alligator clip to the power side of the coil, the game will reset and/or blow a fuse, as you are shorting solenoid high voltage directly to ground).
• If the coil does not fire, it may be a coil that is A/C relay selected. Push the center red coin door button down, and press the black button closest to the coin door. This will put the game in diagnostics mode. This should de-energize the solenoid A/C relay, and turn the power to the coil in question on.
• If the coil still does not fire, either the coil itself is bad, or the coil's fuse is blown and power to the coil is not present.

Testing the under-the-playfield Relay Board.
On most system 11 games, there are a mix of some 50 volt and 25 volt coils. For games without Auxiliary power driver boards, most games use relay boards to power the 50 volt coils. A TIP122/102 transistor on the CPU board energizes the under the playfield relay board. This relay then turns on the ground to the 50 volt coil, motor or other device. This was done because the original TIP122 on the CPU board can't handle the current draw of a 50 volt coils or motors.

The under the playfield relay boards were no longer required on 50 volt coils with games that had an Auxiliary power driver board (APDB). That's because the APDB had TIP36c transistors to control the 50 volt coils, replacing the need for the small relay boards. But some games even with the APDB still used under the playfield relay boards for other uses (like turning off specific strings of GI lights, like on Big Guns).

It is easy to test the under the playfield relay boards. Connect an alligator clip wire to the "DRV" lead on the small relay board. Connect the other end of the alligator clip to ground (the game's metal side rail). This will energize the relay (you should hear a "click"), and the device it powers should also operate (or possibly turn off a section of GI lights).

Coil or Cracked Solder Joints on the Relay Boards.
Quite often the solder joints on the under the playfield relay boards are cracked or "cold". If you are having a problem with any device that is controlled by a relay board, re-solder all the solder points on the relay board.

Grounding the "DRV" lead with an alligator clip on the under
the playfield relay board to energized the device this board
controls.

Testing TIP122/102 Transistor and Down-Stream Wiring/Coil.
If the coil fires in the above test, you may have a transistor problem. You can also test the TIP122/102 transistors this way. Only do this for the TIP122 or TIP102 transistors! Damage can occur if this test is done on other transistors (like TIP42 or TIP36). This test will test everything from the CPU board down to the coil itself. If the TIP122/102 and coil pass this test, and your coil still doesn't work in game play, you have a problem more "up stream". All that is left is the 2N4401 pre-driver transistor, and the logic TTL chip that ultimately controls the whole process (a 7402 for the special solenoids or 7408 for the standard solenoids).
• Game is on, and in diagnostic mode (push the center red coin door button down, and press the black button closest to the coin door; this will put the game in diagnostics mode).
• Remove the backglass.
• Find the transistor that controls the coil and/or flasher in question (refer to the manual).
• Attach an alligator clip to the grounding strap in the bottom of the backbox.
• Momentarily touch the other lead of the alligator clip to the metal tab on the TIP122/102 transistor (only works on these).
• The coil or flasher should fire.
• If the coil or flasher does not fire, it may be a transistor that is multiplexed through the solenoid A/C relay.
• To energized the solenoid A/C relay (which will fire the other coil/flasher that is multiplexed), attach an alligator clip to the grounding strap in the backbox. For games prior to Big Guns (no Auxiliary power driver board), connect the other end of the alligator clip to the metal tab of transistor Q7. For games Big Guns and later (with an Auxiliary power driver board), connect the other end of the alligator clip to the metal tab of transistor Q8. This will energize the solenoid A/C relay on the power supply or the Auxiliary power driver board.
• If the coil or flasher does not fire, and the coil or flasher did fire in the previous test, you probably have a wiring problem. A broken wire or bad connection at the connector would be most common. It is also possible you have a bad driver or pre-driver transistor. Use your meter and test the transistors on the board (see Transistors Testing Procedures for details).

I've Done the Above Tests & they Work, but the Coil still doesn't work in Game mode.
You have preformed all the above tests and replaced/tested the coil, TIP36c, TIP122/102 and/or the 2N4401 transistors. But the coil still doesn't work in game mode!

If the coil in question is a special solenoid (pop bumpers, slingshots), you need to look at the driving components. There are some other smaller (and easily damaged!) components that can fail too for the special solenoids. Check capacitors C70 to C75 (.01 mfd), and resistor network SR20 (4.7k). If these become damaged, a special solenoid can "stick on". Even if your game is Big Guns or later (CPU controlled special solenoids), damage to these components can cause special solenoid problems.

There are more components that needs to be tested or replaced too, if the transistors themselves are good. This is the hardware logic chips that drive the pair of TIP102/2N4401 transistors:

• Q2/Q6, Q3/Q7, Q10/Q14, Q11/Q15: 7408 at U17, 6810 PIA at Uxx.
• Q4/Q8, Q5/Q9, Q12/Q16, Q13/Q17: 7408 at U18, 6810 PIA at Uxx.
• Q18/Q22, Q19/Q23, Q26/Q30, Q27/Q31: 7408 at U19, 74LS374 at U28, 6810 PIA at U54 or U38.
• Q20/Q24, Q21/Q25, Q28/Q32, Q29/Q33: 7408 at U20, 74LS374 at U28, 6810 PIA at U54 or U38.
• Q68/Q69, Q70/Q71, Q72/Q73, Q74/Q75: 7402 at U45 (special solenoids).
• Q76/77, Q78/Q79: 7402 at U50 (special solenoids).
• Q80, Q81, Q82 TIP122/102 lamp row drivers: 7406 at U55, 6810 PIA at U54.
• Q83, Q84, Q85, Q86, Q87 TIP122/102 lamp row drivers: 7406 at U56, 6810 PIA at U54.

Turning on Relay A/C to test both coils/flashers that driver
transistors Q22-Q25 and Q30-Q33 control. On Big Guns and later,
transistor Q8's metal tab is grounded with an alligator clip.
On pre-Big Guns (games with no Auxiliary power driver board),
transistor Q7's metal tab is grounded instead.

Installing a New Transistor.
If you have determined a coil's transistor is bad, there are a few things to keep in mind. Most TIP122/102 transistors also have a "pre-driver" transistor (2N4401 or NTE123AP).

If you replace a coil's TIP122/102 transistor, it's a good idea to also replace its corresponding pre-driver. It will be located near the TIP transistor. See the schematics to determine the specific pre-driver transistor(s).

Game with an Auxiliary power driver board (Big Guns and later), use a bigger TIP36c driver transistor for high voltage devices. These TIP36c transistors have TWO pre-drivers: a TIP122/102 and a 2N4401 transistor. Again, if the TIP36c has failed, it's a good idea to replace both corresponding pre-driver transistors.

Replacing the pre-driver transistors is optional (if they test Ok). You can always test these pre-drivers instead of just replacing them. But if the driver transistor has failed, the pre-driver was probably over-stressed too. It is a good idea to replace the pre-driver transistor(s) too.

Replace TIP122 transistors with TIP102?
This is a very common question. The TIP102 is a more "hardy" transistor than the TIP122, but works exactly the same. So why not replace a bad TIP122 with a TIP102? Well, actually I recommend doing this. Some people will argue with this, claiming the TIP102 will not go bad as quickly, and therefore can cause more heat and damage the circuit board before or while it fails. But if the transistor is already shorted, it really doesn't matter if it's a TIP122 or TIP102. It's still shorted, and will still cause the same heat and damage. So my recommendation is to replace all bad TIP122 transistors with the more robust TIP102. After all, this is what Williams started using on their next generation of pinball boards (WPC) after system 11.

Coil Diodes.
On all electronic pinball games, each and every CPU controlled coil must have a coil diode. This diode is VERY important. When a coil is energized, it produces a magnetic field. As the coil's magnetic field collapses (when the power shuts off to the coil), a surge of power as much as twice the energizing voltage spikes backwards through the coil. The coil diode prevents this surge from going back to the circuit board and damaging components, or causing the CPU to get confused (which often results in a game reboot).

If the coil diode is bad or missing, it can cause several problems. If the diode is shorted on, coil fuse(s) will blow. If the diode is open or missing, strange game play will result (because the CPU board is trying to absorb the return voltage from the coil's magnetic field collapsing). At worst a missing or open diode can cause the driver transistor or other components to fail.

When Replacing a Coil Diode...
Remember to always install a coil diode with the banded end of the diode to the power wire coil lug! The power lug is the the one with the thicker red or purple wire connected to it. This is usually the lug with TWO wires connected to it (because the power wires "daisy chain" from coil to coil). If you install a diode in reverse, it will instantly short and be ruined when power is applied.

Diodes Mounted on the Coil.
Sometimes a diode lead breaks on the coil from vibration. When replacing a coil, the repair person can install the coil wires incorrectly (the power wire should always be attached to the coil's lug with the banded side of the diode). To prevent this, Williams moved the coil diodes off the coils and onto the Auxiliary power driver board starting with Big Guns. This isolates the coil diode from vibration and eliminates the possibility of installing the coil's wires in reverse. This was done on most coils except the flipper coils.