Williams System 3 - 7

Note: This page is a work in progress. Please help get it to a completed state by adding any useful information to it.

1 Introduction

Williams entered the SS (Solid State) era with a conversion of a 1976 Williams EM (Electro Mechanical] pinball game called Grand Prix.

It is thought that 4-5 games were converted to solid state prototypes using the new WMS System 1 MPU and digital displays.

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Next was a 10 unit run of another 1976 EM game called Aztec. The SS version of Aztec is considered to be WMS System 2 and is also very rare. Both System 1 & 2 happened right at the end of 1976. It was a hybrid machine still retaining the EM chime unit in the cabinet for sound and a credit window and EM numbered reel behind that on the backglass. The player scoring was digital.

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System 3 games were the first Williams SS production games, starting with Hot Tip in Nov. '77 and ending with Disco Fever in Aug '78. There were based on the Motorola 6800 8-bit CPU and using a Motorola 6820 PIA (Peripheral Interface Adaptor) to handle the Display I/O from the MPU board. They also had three other 6820 PIAs (the same type) on the Driver Board for the Switch inputs and the Lamp and Solenoid outputs. Solenoid drives were mainly for the Coils at this point, a few triggered sound calls or the 'start of game' tunes.

During System 3 (Phoenix, Disco Fever) a memory protect circuit modification was added as to help protect CMOS RAM data during power up and power down of the game. DIP switches were being used to set game settings (such as # of balls per game, high score replays).

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System 4 games ran from Pokerino in Nov '78 through to Stellar Wars in Mar '79. A notable game just before Stellar Wars was Flash (another Steve Ritchie designed game and one that outsold all of the other System 4 games combined with a production run of 19,505. During System 4, Williams moved from using DIP switches to change game settings to having the game settings changed from the coin door switches. The settings were still stored in battery protected CMOS RAM. [ed Note: Citation needed ? - I'm fairly sure this is accurate] A coin door interlock switch enforced that CMOS memory could not be modified unless the coin door had been opened by the operator. Some of the game audits (coins accepted, total number of games played, etc.) still could not be changed without access to the MPU board behind the backglass.

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System 6 games ran from Tri-Zone in Jul '79 to Scorpion in Jul '80. Two notable games from this era were from the end of '79 and the beginning of '80 Gorgar and Firepower. Gorgar (14,000 produced) was the first talking pinball, and Firepower (17,410 produced) both talked and introduced the 'Lane Change' and 'Multiball (tm)' features to SS games. Note that there had been Multiball play available in EM games, it just wasn't called Multiball (tm) until Firepower. and this is a common misunderstanding. The features these games introduced became standards for almost all pinball games produced right up until today.

System 6a deserves to be mentioned here as it marked a transition to System 7. The game Alien Poker from Oct '80 used the Syatem 6a MPU board (which was not very different from System 6). But it supported 7 digit scoring displays and a redesigned Master Display Driver board, located behind the backglass on the back of the 'Lamp Board'. It also used a special 4 digit "credit/match" display in the approximate position where the System 6 Master Display Driver had been showing the same information (on a 6 digit display, with 2 of the digits unused). This new 7 digit scoring displays with a 4 digit credit/match display were then used in all the System 7 games (and System 9).

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System 7 games ran from Black Knight in Nov '80 through to Star Light in Jun '84. Complete System 7 Game list

Black Knight (13,075 produced) introduced a two level playing field and Magna-Save (tm) where the ball could be stopped from draining down the sides by pressing a cabinet button that activated an electromagnet. Star Light (100 produced) was a 'botique' game by Williams' prduction standards as the focus was then on System 9 and the production line for Space Shuttle (7,000 units). At least one Star Light game was used as the Prototype for System 9.

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System 8 was used on a single game Pennant Fever in May '84. This was a 2 player 'Pitch and Bat' game with men running round bases. It was the first solid state 'Pitch and Bat' that Williams produced. System 8 was never used for pinball games.

2 Games

2.1 System 3

• Contact
• Disco Fever
• Hot Tip
• Lucky Seven
• World Cup

2.2 System 4

• Flash (Later run were System 6)
• Phoenix
• Pokerino
• Stellar Wars

2.3 System 6

• Blackout
• Firepower
• Gorgar
• Laser Ball
• Scorpion
• Time Warp
• Tri Zone

2.3.1 System 6A

• Algar
• Alien Poker

2.4 System 7

• Barracora
• Black Knight
• Cosmic Gunfight
• Defender
• Firepower II
• Hyperball
• Joust
• Jungle Lord
• Laser Cue
• Pharaoh
• Solar Fire
• Star Light
• Time Fantasy
• Varkon
• Warlok

3 Technical Info

3.1 System 3 Architecture

System 3 Technical information goes here.

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3.2 System 4 Architecture

System 4 Technical information goes here.

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3.3 System 6 Architecture

System 6 was an upgrade to the System 4 design, they took advantage of the internal clock in the 6808 CPU, and removed the need for the 6875 clock generator (a companion chip to the 6800 and now obsolete and impossible to find).

This also changed the way the 'watchdog' circuit functioned. The watchdog monitors the CPU (IRQ signal), and will blank the displays and lamps as well as stopping the solenoids from firing. When something goes wrong, perhaps the MPU board has locked up, 'blanking' should prevent further damage to the game by 'locked on' coils and other output components driven from PIAs on the MPU/Driver boards.

More ROM memory could be addressed, and this was used to hold increased game code. As an example, Firepower used a 2716 2K Game ROM (which was standard for IC14) plus 3 x Harris Bipolar Proms (512 bytes each) giving a total game code size of 3,584 bytes. Having just 3K of code space is nothing by today's standards. Programmers had to work hard to get good game code in such a small space.

During early System 6 revisions the transceiver chips, 8T28 ICs at IC9 and IC10 were found to not be needed. They were eliminated from the design, as they didn't need to amplify signals to and from the Data bus with modern ROMs. If the ICs are working, then leave them alone. But if not, these buffers are obsolete and can be removed and bypassed, in effect by jumpering the Data Bus pins of the CPU directly to the Data Bus. On Firepower alone you must do the 'Combo ROM' modification, to allow the use of a 2732 Eprom as the Game ROM at IC14. This replaces the Firepower game code found in 4 ROMs as described above, and is an excellent idea. Less chips to worry about, less sockets to replace. All other System 3-6 games will use one 2716 2K Game ROM (or Eprom) in IC14.

Williams also moved to using the updated 6821 PIAs and the 6802 CPU during System 6. [ed note: A citation is needed for exactly when this happened, perhaps with verification from an original owner's game board?]

The 6802 processor was the same architecture and "backwards compatible" with the 6808, but had internal RAM, instead of the 128 x 8 bit MC6810 which must be used with the 6808 CPU. Pin 36 is usually grounded on the 6808, and you can therefore use a 6802 on older boards and it will work, provided the external 6810 RAM is good. If you set Pin 36 of the 6802 "high" (usually through a 4.7K "pull up" resistor to the +5v logic rail) then the internal RAM is enabled. The 6810 (if not socketed) can usually be left in place.

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3.4 System 7 Architecture

System 7 was considered a major step change. It had a redesigned MPU board, now supporting a single 7-segment LED display for indicating improved diagnostic information, instead of the original 2 LEDs that System 3-6a MPU boards had used. It also added commas to the player scoring displays and moved the sound select support to the MPU board. An extra 6821 PIA supported both the sound/speech selects and the display of commas. An extra 12-pin header at 1J8 was added to provide connections for the new Sound and Commas support. This freed up five solenoid drives at positions #9-13 on the Driver board, which had been sound/speech selects. They were then available to drive extra game Coils or Flash Lamps.

The MPU used two 2114 Static RAMs, these 1024 x 4 bit RAMs replaced the use of 6810 RAMs mentioned above. There was extended memory addressing, support for multiple 2732 ROMs (or EPROMS) as standard and a huge number of jumper selections available. The jumpers support various memory addressing schemes and ROM sizes, making the System 7 board MPU "backwards compatible" and able to emulateany of the previous System 4-6a games. Provided, of course the correct Jumper Settings and EPROMS are installed.

The Sound and Speech boards were unchanged for System 7, both sound and speech boards remained compatible from their introduced for Gorgar. In some cases the System 7 game had no 0.100" 40-way IDC header for the speech board connection, as this was a cost saving measure made by WMS for games produced without speech. This connector is cheap and available today, as it is still used for PC IDE hard drives, and modern PCB connections. Adding this connector back to the sound board allows it to support a speech 'daughter board' by removing the Jumper at W1.

The separate Driver Board remained almost completely unchanged from System 3 right through to System 7. One small change was made to the Driver Board during System 7. Eight resistors were changed to zero-ohm jumpers in the switch matrix inputs, apparently to increase sensitivity.

The Driver Board mates with the MPU board using 40 x 0.156" header pins on the MPU and female sockets on the Driver Board. This is a continual source of repair problems for this era of Williams machines. To solve this, when designing System 9 Williams combined the MPU and Driver Boards (and the Sound Board) on to a single PCB (Printed Circuit Board), and removed the problems associated with the now infamous Williams "40-way" connector. Only the speech board remained separate, as digital speech was considered an optional feature.

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3.5 Flipper ROMs

The OS (Operating System) for a Williams pinball game is called the Flipper ROM. Flipper ROMs with the same color label can be considered generic, although there is at least one exception where a 'custom' White Flipper ROM was used World Cup Soccer.

The Game ROM can be considered the 'personality' ROM, it provides the rules and objectives that are specific to that game's playfield layout. It also maps the Lamps, Solenoid and Switch Matrix to their specific purpose for that game and controls how they are sequenced and timed. Examples would be the 'attract mode' lamp sequence or when sound / speech select calls are made.

Because of the large game production runs, Williams bought batches of Masked ROMs (fixed and not erasable) for the games. This was cheaper at the time than using Eproms (UV erasable, with a small window) as Eproms were still fairly expensive in the 80's. They used the same method for producing most of their Flipper, Game and Sound ROMs.

You may want to replace Masked ROMs with Eproms of the correct type as the original ROMs are 30+ years old. As the legs blacken and tarnish they will weaken and fall off. For a similar reason, many of the ROM sockets on the MPU boards will need to be replaced, especially any sockets bearing the words 'Scanbe', which are poor quality. Masked ROMs are very stable as they start life as all 1's and then the information is programmed by "burning" each selected bit open, like blowing a tiny fuse. So they will rarely will lose their programming over time. If you ever wonder about why we 'burn' our CDs and Eproms, that may be the source of the term.

3.5.1 Flipper ROM Colors

Williams used standard ROM files for System 3-7. These two Flipper ROMs are located at IC17 and IC20. Systems 3-6 use two 2716 or 2316 Eproms, while system 7 used a 2716 in IC20 and a 2532 in IC17.

3.5.2 White Flipper ROMs

Mainly for System 3 games.

3.5.2.1 Exceptions

Pokerino (Nov '78) and Phoenix (Jan '79): Both System 4 games, but use standard White Flipper ROMS. World Cup Soccer: Uses White Flipper ROMs, but the ROM in IC17 is unique - the MPU will not boot and run with the standard White ROM.

3.5.3 Yellow Flipper ROMs

Used in System 4 games.

3.5.3.1 Exceptions

Flash (Jan '79): Earlier version used Yellow, a later version used Green Flipper ROMs (Green is preferred). As always, the Game ROM used must match the Flipper ROM color that it was written for.

3.5.4 Green Flipper ROMs

Used in System 6 / 6a games. Tri Zone (Jul '79) to Alien Poker (Oct '80)

3.5.5 Blue Flipper ROMs

Used in System 7 games. Black Knight (Dec '80) and later.

3.5.5.1 Exceptions

Star Light (June '84, 100 produced) which was the last System 7, appears to have non-standard Blue Flipper ROMs. For very small production runs, games were supplied from the factory with Eproms. Both my Flipper ROMs 1 & 2 are not standard Blue ROMs (checksums differ).

4 Problems and Fixes

4.1 Wiring Connector Issues

Williams made a poor wiring harness decision with this series of games that will allow you to incorrectly connect the cabinet harness to the head harness. Always be sure to double check not just connector pin counts and colors, but most importantly, wire colors. Not mating these connectors correctly will allow the 28V solenoid circuit to fry the 5V logic circuit and can cause extensive damage.

4.2 System 7 MPU Board Issues

Diagnostics, and 'my System 7 MPU Board won't boot'.

Forget about getting anything at all on the Player Displays without having working ROMs in place and a good MPU board. Blanking has to go 'high' before the displays will work. So coin door game diagnostics are useless until the MPU board runs correctly.

But help is at hand on the System 7 MPU, Williams added a single 7 segment LED display to the board To get anything at all on the 7 segment display LED on the MPU you need: The 74LS47 Display Driver IC34 to be working. The 6821 PIA (at IC18) on the MPU responsible for driving the score displays to be working. The logic +5v to be good.

Normally when a working board boots, the LED flashes "0" briefly and the OS turns off the LED display. The game, if attached would then be in attract mode if everything was perfect. Pressing diagnostics should show a "0" and then return to attract mode with the LED display blank. [ed Note: Correct me if that is wrong]

Once you have that the above chips installed and working and sockets replaced or tested good: With no ROMs installed, a board with a fault or a ROM fault if they are installed, the "top two" LEDs (if there) would be lit and the LED dislpay would show "0". The MPU board is 'locked up', in that condition. Display Driver PIA IC PA4 - PA7 will be high. Pressing the Diagnostic switch will not change things.

Then you need an OS, which is the 'Flipper Roms' in pinball. When they 'Boot' (provide a set of instructions to the CPU)- even with the Game ROM removed, the fist thing they do is to "turn off" the LEDs 1+2 and so the onboard LED display (7447) would then go blank.

In fact, you should see "0" flash once and go blank. That means the board is not locked and at least Booted the OS.

Anding in a good Game ROM after that may get you to the point of running diagnostics. Pressing the diagnostic switch would then provide a (hopefully) valid indication of what component is stopping the (pinball or whatever) from running. Here are the key indications (for System 7, SYs 8&9 may be similar):

You can get these results with error conditions by using your FLipper and Game ROMs, or the 2532 WMS Test ROM in IC17 (on Sys 7 boards): If all the support chips are good, and you can get one "0" flash and then it goes blank, then you can trust the on-board display, Press the diagnostic button, the numbers are:

0 - Test Passed 1 - IC13 RAM Faulty 2 - IC16 RAM Faulty 3 - IC17 ROM 2 Faulty 4 - IC17 ROM 2 Faulty 5 - IC20 ROM I Faulty 6 - IC14 Game ROM 1 Faulty 7 - IC26 Game ROM 0 Faulty 8 - IC19 CMOS RAM or memory protect circuit faulty 9 - Coin-door closed, memory protect circuit faulty, or IC19 CMOS RAM Faulty.

Getting an 8 or 9 is *good* to see - you're almost there! Here are some further tips about those conditions:

8 - MPU board may be good. Is it looking for the Driver board? Make sure it's there and the "40-way" interconnect is perfect. Test again. The interconnect isn't there for System 8 onwards... by System 9 MPU and Driverboard (and Sound!) are all one PCB.

Then suspect that IC19 RAM is faulty or finally a memory protect fault.

9 - First check for coin door closed (or pin 1J4-1 or 1J3-1 is being grounded), then is IC7 faulty? Finally is IC19 RAM faulty?

If you get a "9" - I'm always tempted to install in a game open the coin door and try and boot up. But this is wrong, as you still have something not right. Your IC19 5101 CMOS Ram is faulty, or another memory protect component is faulty.

Remember to do the "switch on, off and back on again quick" trick to see if you can get attract mode when reinstalling in a game after taking an MPU out. That's a classic Fonzarelli move, a "golden oldie" of the pinball world. Because lots of times that does the trick.

Parts: The 7-Segment display can be replaced with a KINGBRIGHT SA03-12HDB LED 0.3" RED DISPLAY. 5101 CMOS RAM. 5101-1 The low power version is needed, as it needs battery backup to hold RAM contents when the game is powered off. A 6821 PIA is a standard part. MC6821 MC68B21 are common. xx6821, xx68A21, xx68B21, where xx can be MC (Motorola) or HD (Hitachi Data) will all work. I forget what A means without looking it up in a datasheet, the B means up to a 2Mhz clock, without any letter to 1MHz.

4.3 Reset Issues

4.3.1 Voltages

The MPU board needs two voltages to boot: +12v which only the MPU uses for the reset circuit, and +5v (logic power) for the MPU and Driverboard IC chips.

If the game goes dead, but the sound board continues to work then you may have a fault with the PSU, power connections to the MPU, blanking or the reset circuit.

You check for sounds by pressing the sound board diagnostic test. You need to switch off & back on to cancel the looping sound test. The sound board has its own PSU. It takes 18v AC directly from the transformer and makes +12v (reset) +5v ( logic) and also -12v (Speech and mixers). It's probably OK to assume the +5v and +12v going to the MPU (and Driver Board) are OK from the PSU if the sound board boots and runs. it's like a mini MPU, with the same CPU and one PIA chip.

The main PSU board only needs to make the first two, +12v and +5v (no -12v) for the MPU and Driverboard. But it also generates DC power for the flippers and the solenoids (+28v DC or so).

4.3.2 Connectors, connectors and connectors

With this era of game, most of them 30+ years old now, you will have problems with connectors. If your game starts to reset for no reason during play, it may be worth first re-pinning the connectors at 1J2 on the MPU Board and at the outputs from the PSU. This is always a good step, even it it does not fix the immediate issue. It avoids power problems later on.

This involves replacing the header pins on the board and the female connectors on the cables. The pins are .156" (and I prefer square pins) although round are still available, phosphor bronze. On the female side, crimp pins of the trifuricon type are best. Second prize goes to just replacing the female IDC connectors with new ones. But in that case rather than a crimper, you must buy a .156" 'punch-down' tool, which is a specific part for this replacement to work correctly. Don't buy the tool, and you will damage the IDC housing and pins, and the wires just don't seat correctly.

Again, the connector is a .156" 9-way connector at 1J2. There is also a 'key' pin where the hole is blanked off on the connectors and the pin cut off flush with the board. This prevents plugging the power in to say the switch matrix or swapping two connectors over. It's easiest to just buy a bag of these for blanking off the 'key' positions, rather than try to re-use old ones.

4.3.3 Reset Circuit

An MPU unable to boot may mean that its reset circuit is faulty. A +12v line comes in from the PSU board to the MPU on pin 9 of 1J2. That's the top pin, you can also measure the +12v at TP1 on a System 7 MPU. Don’t get hung up on it being exactly +12v, it's not that regulated, but it can’t drop too much lower than 11.5v or the reset circuit may have a problem generating enough voltage to keep reset “up” to the CPU. But 11.5v to 14v is not unusual and can still work.

That +12v for reset goes into a circuit that waits (for about a 1 sec. delay) for the +5v to stabilize before it lets the CPU boot. If the +12v (or output from the reset circuit) drops, the reset halts the CPU, PIA(s) and the 5101 CMOS RAM chips before the +5v to them dies. A shutdown of the CPU will also pull blanking low and halts solenoids, lamps and displays to protect them from further damage (coils firing, memory glitching) during the power down. So spikes or drops to the +12v line may halt the CPU at the wrong time.

You can measure reset’s condition at TP8. That’s the far right test point on the bottom of the MPU just above the 40-way connector. Should be marked as TP8 on the PCB mask. When booting the game and watching reset, it stays low for a heartbeat after power on and then hit +5v. 4.75v or around that is fine. Don't get hung up too much on the voltages being exact for the reset circuit either.

If we find that the +12v is looking OK when we measure it, and the sound board is always booting and working... I’d believe the +12v at the PSU to be stable.

A good trick to 'inject' a reset, is to try connecting +5v for a second or two to the reset test point at TP8. If the CPU boots (reset must be a logic high now on pin 40 of IC1), then you will need to rebuild the reset circuit on the MPU.

So that involves running a jumper lead from TP8 and briefly touching TP9 (+5v). TP9 is at the top right the battery holder (but you should have removed that old holder and added a 'remote battery' holder), so it's top right of where the original used to be.

4.3.4 Divide and conquer

The reset circuit is in two halves. For a System 7 MPU board, you can apply +5v directly to the top of resistor R12. If the board boots and stays stable, you know that the problem is on the 'right hand' side of the circuit. (On System 6, you do the save trick using R32. And different parts are needed to rebuild a System 6 reset circuit, but it's similar).

There are 12 active components that make up the reset circuit, 8 of them transistors.

4.3.5 Step One

The Right Hand Side. Start by replacing transistors Q6 – Q9 (all 2n4401 NPN) get 10 or more of them, they’re cheap to buy and you will need them lots of times. They are used as pre-drivers for the solenoid power transistors on the Driverboards for System 3-7). Test the board for your booting problem. If still there, replace the two zener diodes: ZR1 is a 6.8v Zener (1n5996) and ZR2 is a 3.9v Zener (1n5990) - you can't replace these components with anything else to my knowledge. These are critical values. And put the orientation of the band of the diode the same way as the ones you remove. Taking a digital picture of how the circuit in the top left of the board looked before you started is a good ides. Or replace components one at a time. You could of course test for boot on the bench each time you replace something, that may slow things down but you won't replace too many components you didn't have to. It should be booting now, if not attack the other half.

4.3.6 Step Two

The Left Hand Side. Start by replacing transistor Q2. Q2 is a 2n4403 PNP transistor, cheap as well but you won’t need as many for pinball repairs. then replace Q3-Q5 with the 2n4401 's like before. I would replace D19 (a 1n4148 fast switching diode) you could test it with the diode setting of your DMM, but I don't trust testing diodes in circuit, and if I’m soldering in that section, I just cut it out and replace it. Cost will be pennies, and most pinball people should have new ones on hand. Again, be sure and notice the direction of the band on the old diode, and put the new one back the same way. Same thing goes for the orientation of the flat side of the transistors. Don’t get them wrong when replacing. The last component to replace would be the capacitor at C27 (10 uF @10v is the original part –look on the side of the cap). Replace it with a tantalum 10 uF @ 16v, if you can find it. You can go up in voltage even to 20v or more, but don’t change the value of the capacitance. Note that some caps have markings showing a (-) side, usually running down the side of the capacitor. If it shows a polarity, the (-) side of C27 points down on the PCB, towards the 40-way interconnect.

4.3.7 Step Done

That’s it. Usually fixed by step one. Or down to one (or more) of those 8 transistors. I have seen a zener or the 4148 diode at D19 be the problem before. For me, the cap C27 has always been good. Maybe test it for a dead short with the power off and replace it if it's shorted to ground.

4.3.8 Kudos

Thanks goes out to Cody Laux, who owns a game that was resetting (going dead and blanking) when all four flippers were fired. He approached me a question about his out his Black Knight (an excellent Steve Ritchie design). This prompted me to explain the reset circuit repair to him in my own words. I've mentioned connectors above for completeness, which he was already aware of and had replaced Bridge Rectifiers and rebuilt the 40-way connector. Here's hoping he fixes his BK, and if so I'll post back a solution here, or move the solution to the correct area. The above step-by-step repair guide of the reset circuit will be no less valid for others to use with MPU problems.

4.5 Display Driver Board Issues

4.5.1 System 3 to 6a

The Master Display Driver Boards came in two versions, discrete and IC based. Williams designed the discrete version when the UDN7180 and other specific Gas Plasma Display Driver ICs became scarce (or expensive even then There are also some logic chips that decode the BCD data for the 7 display segments (MC15453) and to buffer and invert the display strobe lines for the digits (MC14069) which are common to both board versions.

4.5.1.1 Discrete version Display Driver

The D8168 board uses MPSA92 (PNP in a TO-92 package) and MPSA42 (NPN also TO-92) transistors to drive the Master (Credit/ Match) and player scoring displays. These gas plasma display driver transistors are available today and still very cheap to buy. Unfortunately, this style of board is less common to find in the wild, but actually easier to maintain. At least no one can try to charge you $20+ for an obsolete driver IC.

4.5.1.2 IC version Display Driver

The D8000 IC version board is composed of ICs that implement the transistor arrays. Usual chips are the UDN-7180 and the UDN6118A-1.

UDN-7180 IC chips are still fairly easy to find. Cost should be reasonable, if you shop around.

The Sprague UDN6118A's (or uPA6118C) which are usually available have a lower breakdown voltage (~85v DC) than original part. The displays run at +/-100v DC as standard and need the higher rated original part which is the the UDN6118A-1 (note we have -1 at the end). The UDN6118A-1 is rare and also becoming very expensive, as much as $20+ for an IC chip. Wow!

Remember to compare the costs and trouble involved of repairs with buying a replacement Display Driver board. You can pick up a complete and working original board if you look around. Another option is to buy a reproduction board. James Kohout does a nice repro board for $75 (at the time of writing). It's engineered as a discrete version using MPSA92 and MPSA42 transistors, but with the System 7 connectors. to my knowledge, not transistor versions were ever made for System 7. Usable in Algar / Alien Poker (both Sys 6a games that had 7 digit scoring), all System 7 games and Space Shuttle / Sorcerer (System 9). [PinballPCB.com] Really excellent quality for the price, and no expensive replacement ICs. Ever. --Firepower 22:13, 27 April 2011 (BST)

4.5.2 Repairing the Master Display Driver (System 3 - 6 with 6 digit displays only)

Firstly, a ***Warning*** With the game on you are dealing with +100 and -100v HV DC (High Voltage) going to the displays. That's a potential 200v difference and you only need to feel that once to know it. Wear tennis shoes (trainers or any rubber soled shoe) when working on Diplays with the backbox open. This is a shock hazard! If you are not capable or happy with measuring these voltages with a steady hand, then get someone else to help you or be there to 'spot' you. Always a good idea and more fun than working on your own.

Sometimes displays go blank and it is in the wiring harness from backbox to the Master display, and not the Display Driver PCB at all. If you can swap a working Master Display driver board from a System 3-6a game with displays that are stable, then do that first. You can quickly determine if the fault is cabing / display PIA on the MPU (so in the backbox) OR the Master Display driver PCB on the front of the light board.

4.5.2.1 Segment failures

Segment failures on a single display could be that display failing. Same issue if just one display is blank. Swap that display with another (power off first) and see if the problem moves with that display. If it moves, it's that display glass or its board. If it doesn't move and stays at the same player location, see below for the possible suspects.

Segment failures on multiple displays and probable cause:

Players 1 & 2 Segments and master display Segments are out:

• BCD inputs are A1 B1 C1 D1 from the MPU board
• MC14543 BCD to 7-Seg. Decoder IC5
• UDN7180 Display Driver IC9
• Resistors R1-R7

Players 3 & 4 Segments

• BCD inputs are A2 B2 C2 D2 from the MPU board
• MC14543 BCD to 7-Seg. Decoder IC8
• UDN7180 Display Driver IC10
• Resistors R8-R14

Start out by measuring all the resistors on the master display board with the power off. R1-R14 should be around 10K ohms. Any that are not within about 10% (say a range between 9.6K to 10.4K ohms) need to be replaced. Also look and see if any look "toasted".

Those resistors get cooked on the Master display boards and usually will then cause single segments to fail on both the player 1&2 or 3&4 displays together, as they are linked. Te resistors need to be replaced with the same value: 10K but at 1/2 Watt. Some of the modern 'metal film' resistors are rated at 0.6W which is perfect and they fit nicely in that location. Older 0.5W (1/2W) resistors are larger, but are fine. Mount them slightly off the PCB so they get good airflow all around the resistor body.

Do the above steps anyway, no matter what the display problem is although it's probably not going to be the whole story. Replacement resistors are cheap and will prolong the life of your displays. Reducing the voltage going to the displays when rebuilding the HV section of the PSU is a good step to take and will help as well. You only need to replace two Zener diodes to achieve this.

4.5.2.2 Digit Failures

Strobe inputs for the display digits come in to three 14069 hex inverters on the driver board. IC1, IC2 and IC3.

• IC1 is dedicated to the Master Display 'Credit/Match'.
  • Strobes are: 15,16,7,8 left to right, for the 4 digits used.
• IC2 and IC3 strobe inputs are more complicated, to see the distribution on these IC chips, refer to a display diagram.

Strobe (or strobe input) failures are likely to show up in these pairings:

• Strobes 1-6: shared for players 1 & 3
• Strobes 9-14: shared for players 2 & 4

4.5.2.3 All Displays are Blank

This could be that the +100v or the -100v HV are missing from the PSU board. Both have to be there, so check that the output from the PSU and that the voltages (HV) are good first, and getting to the Master display driver to be relayed to the player displays.

There are also 5 x 3 Mega ohm resistors, at R15-R19, These are for the cathode "keep alives" and again should be near that value. If the 3 Meg resistors don't look cooked and are within spec, check that you can see an "orange glow" in the displays when the lights in the room are dim or off. If you see a faint glow (some describe it as an 'orange neon dot'), then look elsewhere for the fault.

If you don't see the display glow, check the wiring to the connectors carefully looking for a burnt wire at pins 4J7-1 -2 and -6 on the master display. Do this with the power off, as you are dealing with 100v and -100v DC. If you find a cooked wire, sometimes just cutting the wire back a bit to expose clean metal and then reinserting it firmly in the IDC connector will repair the problem with a bad connection for one of the HV lines. Remove and reseat all the edge connectors on the master display board and especially examine the ones that go to the backbox. You can clean the copper contacts on the edge connectors gently with an eraser to shine up the copper if it's dull or has "dead spots" worn on it. Check any inline connectors as well.

I also recommend disconnecting all the player displays 1-4 at the Master display. Get it working with the just the credit/match and then with one other display attached, like player 1. Then add back the player 2-4 displays one at a time (you need to power off each time you add or swap a display), tesing for correct function each time. You can also swap the player displays as a diagnostic step and carefullt observe if the fault(s) stay with the Display in question or move to the new location. Use the "display test" on the diagnostics for this. After the above is checked, perhaps you do have to suspect the IC chips (or for the discrete version the transistors). Depending on whether the Segments or Digits are out, it will point you at a specific IC (or transistor array). Knowing which displays are out helps reduce the fault domain down to one chip. You need be like a detective, following the clues. Having a Master Display Assembly drawing and a schematic on hand will help with this process.

4.5.2.4 Testing the ICs

Using the diode mode on a DMM it is possible to help determine if the ICs appear to be OK. This is not a conclusive test as they can pass the test and still "flicker" displays or fail under load.

[ed Note: Need tips on testing the ICs on the master board with the power off here.] Don't just copy it from "somewhere else" verbatim.

Here's hoping that it isn't one of the IC chips that's faulty.

4.6 Sound / Speech Board Issues

The sound board is actually a "mini-MPU" board running a 6808 CPU and 6821 PIA. It has it's own PSU and takes 13v AC voltage directly from the Transformer and rectifies it to provide the +5v logic and +12v reset circuits. I believe this design was for ground isolation and noise reduction.

I have a whole section hosted temporarily here: http://homepage.ntlworld.com/alienpoker/FP-Parts-Snd.html It is discussing the Sound/Speech architecture and repairs for this era of games. It is my own work, and some of it was copied into the pinrepair manuals, if you see similarities, it is *not* because I copied Clay.

I looked into converting it to wiki with a MS word plugin, but had problems with the conversion crashing. If someone more knowledgeable about the 'ways of the Wiki' wants to take a stab at converting it, I will edit it to fit better in this space. The links to my sites (and diagrams) will need to disappear and be replaced by links to IPDB manuals or other places. I don't mind if the facts and information in tables are presented verbatim as they are my designs and invention. -Cheers.

5 Game Specific Problems and Fixes

Example would be servo controller on Independence Day pinball

6 Repair Logs

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