to System 7 Pinball 1977 to 1984,
by Cfh@provide.net (with help from Mark & Jerry)
12/15/16. Copyright 2002-2021. all rights reserved.
IMPORTANT: Before you Start!
If you aren't up to repairing pinball circuit boards yourself or need pinball parts or just want to buy a restored game, I recommend seeing the suggested parts & repair sources web page.
Table of Contents
2. Before Turning the Game On:
2g. Before Turning the Game On: CPU Board Upgrades.
System3, System4, System6, System7 CPU Board ROM Upgrades.
In the previous section, we talked about replacing circuit board sockets. But before doing that, please check this section out. It may give some good insight on some System3 and System4 CPU sockets that do *not* need to be replaced (because they won't be needed).
Remember, until the the CPU board is running properly, it is a good idea to remove the lamp and solenoid fuses F2 and F3 from power supply board. This will minimize any risks of burning coils or lamps.
System3 CPU Board ROM Upgrade.
In order to complete this modification, the chip selection circuit also needs to be modified. Here are the steps:
Most System 4, System6 and System7 CPU boards uses five ROM sockets: IC22, IC21, IC20, IC17 (from left to right), and sometimes IC26 (mounted above IC22). There is a sixth ROM socket at IC14 too. Again, just like in System3 CPU boards, IC14 can use a 2716 EPROM, which will eliminate the 3624 masked ROMs (512 bytes) at IC22, IC21 and also IC26! But in the case of System 4/6/7 CPU boards, the modification of IC15 discussed above is already done.
Again, since we have already discussed replacing all the CPU sockets, this trick will allow us to replace fewer sockets on a System 4/6/7 CPU boards too. That is, using a 2716 (2048 byte) game EPROM at IC14 will replace the *three* 3624 masked game ROMs (512 bytes each) at IC22,IC21,IC26. Doing this means the sockets at IC22,IC21,IC26 will not be used, and do *not* need to be replaced!
Since the chip selection circuit is already set to use IC14, it is just a matter of getting a new EPROM "burned" to replace IC22,IC21,IC26. There are lots of people that offer this service for around $10 to $15 for this chip. Williams' web site also has the binary ROM images for these EPROMs available for free.
System 6 CPU Board ROM Upgrade.
Firepower System 6 CPU Board ROM Upgrade.
Flipper ROMs at IC17 and IC20 (all System3-7 CPU Boards).
I highly recommend installing new EPROM versions of the flipper ROMs. The old ROMs often get "bit rot", and the silver legs tarnish and easily break. It's just a good idea to replace these old ROMs with new EPROMs.
Remember, there are different flipper ROMs for each system revision level. They are coded by color, one color for each system of games (more or less as they did overlap). Basically the colors decode like this:
The big exception to this rule was World Cup. This game used one unique white flipper EPROM, different than the standard white flipper ROM at IC17. Without this special flipper EPROM, World Cup will not boot.
Also remember the game ROM (IC14) *must* match the correct color flipper ROMs. And some games had a different game ROM for different flipper ROM colors. For example, Flash, which had a very long production, has a yellow flipper game ROM (system4), and a green flipper game ROM (System6). This happened because Flash's production was so long, some Flash games used System6 boards. Now it does not matter which game ROM is used. That is, a Green (system6) Flash game ROM can be used in a System4 CPU board (or vice versa). But the Green Flash game ROM *must* be used with Green flipper ROMs, and a Yellow Flash game ROM *must* be used with Yellow flipper ROMs!
System3 CPU Board Reset Modification.
Below is a diagram from Williams of this modification. The three red components are the ones to remove, and the blue component is the resistor to add.
On very early system7 CPU board, there was an unmarked 74125 chip located above IC33. This chip is not needed, and Williams removed it from the system7 design. If there is a 74125 installed above I33, it can go bad and lock up the CPU. If your CPU has this chip, it is suggested that you cut it off the board.
2h. Before Turning the Game On: CPU/Sound Board Jumpers, ROM software, Flipper ROMs, DIP Settings.
The "Flipper ROMs" Explained.
The flipper ROMs are identified by color: white, yellow, green and blue. A different color denotes a different version of the pinball's operating system. The color originally referred to the actual color of the label on the CPU ROM chips themselves, and was probably used when the games were manufactured for easy identification.
One color for each system of games (more or less as they did overlap for Flash), but basically white=system3, yellow=system4, green=system6, and blue=system7. The big exception to this rule was World Cup. This game used a unique flipper ROM2 at IC17, different than the other four color groups of flipper ROMs. Without this special flipper ROM, World Cup will not boot (also it should be noted that Flash has two versions of IC14 Game ROMs, one for yellow flipper ROMs and one for green Flipper ROMs, because Flash's production was so long it was made with system4 and later system6 CPU boards).
There were two flipper EPROMs on the CPU board at IC17 and IC20 (both 2716 EPROMs or 2316 masked ROMs, except on System7 which had one 2532 EPROM at IC17). Note in many System7 games IC20 was mislabeled (make sure the 2532 EPROM goes in IC17, and the 2716 EPROM in IC20).
THE CORRECT COLOR FLIPPERS ROMS MUST MATCH THE GAME ROM. As Williams pinballs evolved, so did the operating system Flipper ROMs. So a Firepower (a green Flipper ROM system6 game) can not use yellow (system4) Flipper ROMs! This is because as the games evolved, the bookkeeping and adjustments advanced and added new items. These new features led to a new version (color) of the Flipper ROMs (the operating system of the game).
Note some software included here may not be for the same system of CPU board installed in a game. For example, a Flash game may have a system4 CPU board, but "green" system6 software is included here. This does not matter. That is for example, all System3 CPU boards should have already been upgraded to System4/6 specs (as outlined in the CPU Upgrade section). This should be done so that a system3 CPU board can run system4 or system6 software (as discussed previously, system3 and system4 CPU boards are upward compatible to system6, except in the case of Firepower).
It is helpful to remember the following Flipper ROM color codes when dealing with game software: White = System3, Yellow = System4, Green = System6, Blue = System7. Flash spanned multiple systems when it was produced, being made with both system4 and system6 CPU boards. Therefore Williams had both yellow (system4) and green (system6) Flipper ROM game ROM versions at IC14 available for Flash. The newest version should always be used (in this case, Green Flipper ROMs). When it comes to game software, the general rule of thumb is, "newer is better". So make sure the CPU board used is upgraded as documented in the CPU Upgrade section. Also it should be noted that there were only two games made with yellow flipper ROMs: Stellar Wars and Flash (but the yellow Game ROM version of Flash is not included here, as the newer green flipper version is instead). Also Flipper ROM1 is at IC20, and Flipper ROM2 is at IC17.
Williams has System7 ROM software available at www.pinball.com/tech/sys7roms.html. These files appear to be good and correct. Star Light ROM files thanks to Clive Jones.
Psuedo 7 Digit scoring on 6 Digit displays.
Using the Above Firepower EPROMs Files.
Firepower was an unique System6 game in that it used the four ROM sockets at IC21, IC22, IC26, IC14 for holding game's software. Three of these ROM chips (all but IC14) were 512 byte 7641 chips, and IC14 was a 2716/2316 ROM. Using the additional ROMs allowed Firepower to have extra space for the game program (in addition to the 2716/2316 green Flipper ROMs at locations IC17, IC20). The original configuration of three 512 byte PROM chips at IC21, IC22, IC26 and a 2316/2716 at IC14 required that the System6 CPU board jumper J4 be installed, and J3 be removed (there were orange labels in the cabinet and on the CPU board noting this).
The three 512 byte PROMs used in Firepower at IC21, IC22, IC26 are troublesome. In addition their sockets may need to be replaced. A better solution is to use a single 2732 EPROM at U14, eliminating all the 512 byte ROMs and their sockets! The ROM data file documented here accomplishes this, but some System6 CPU board modifications must be made. Note this System6 modification was originally designed by Duncan Brown. Note a System6 CPU board modified in the described way will no longer work in any other games unless the modifications are "undone" (but the Leon test EPROM *will* work in a Firepower modified System6 CPU board!)
If Firepower is to be run in a System7 CPU board, please see the section below. Using the Firepower EPROMs in a System7 board requires no modifications to the System7 CPU board, but it does require a different set of EPROMs than the System6 version.
These instructions and version was created by Duncan Brown. Note there is also another version of this Firepower combo ROM concept out there called the "ZIG chip" (I believe developed by Tom Callahan). It is basically a slight hardware deviation of the same theme. The difference between the two methods is that the Brown method uses two diodes and a pull-up resistor, where the ZIG method just uses straight jumpers. Technically speaking, the ZIG method electronically should *not* work, but it does because of the nature of LS TTL chips. Most people use the ZIG Firepower method as it is simplier (though if the 74LS139 chip was replaced with a 74139, the ZIG method may no longer work!)
Steps to modify a System6 CPU board a single 2732 Firepower EPROM at IC14:
The Duncan Brown Method.
System6 CPU Board Jumpers.
System7 CPU Board Jumpers.
Note the following rules apply:
Using a 2732 EPROM in a System7 CPU board at U17.
Make sure to use the right w22 pad in step 4 above, otherwise it may short U17 pins 18 and 21. Also make sure to cut the trace clean in step 3, otherwise you may short 5 volts to ground.
By far the most versatile CPU board in the System3 to System7 era is the System7 CPU. It can run any System3, System4, System6 or System7 game firmware. It can also drive a six digit or seven digit master score display panel. So if there's one CPU board to have, it's the System7 board.
The only caveat to this is System3 to System6 game firmware needs a special Flipper ROMs for the System7 CPU board. The two White (system3), Yellow (system4), or Green (system6) 2716 Flipper EPROMs need to be combined into a single 2532 EPROM, which will plug into socket IC17 on the System7 CPU board (the existing system7 Blue Flipper ROMs will not work with the older system3 to system6 games).
The stock System3 to System6 2716 Game ROM (IC14) can be used on the System7 CPU board at IC14 (the only except to this statement applies to Firepower, see below). All other EPROMs should be removed from the System7 CPU board. The best part is no System7 CPU jumpers need to be changed for this configuration (assuming the System7 CPU board is set for any game other than Hyperball/Defender).
For example, to combine the two "Green" 2716 Flipper EPROMs into a single 2532, the following MS-DOS command can be executed:
copy /b grn1ic20.716 + grn2ic17.716 grn_ic17.532This MS-DOS command does a binary copy of the Green1 (IC20) Flipper ROM, adding to the back of it the Green2 (IC17) Flipper ROM, and putting the two separate 2716 files into a new combined 2532 file. The same thing can be done for the White and Yellow flipper ROMs, and for the special World Cup Flipper ROMs. If preferred, these files have already been copied and can be downloaded by clicking here: System3 to System6 Flipper ROMs for the System7 CPU. Again remember, the stock System3 to System6 2716 Game ROM (IC14) can be used on the System7 CPU board at IC14 (the only except to this statement applies to Firepower, see below).
Using the Firepower EPROMs in a System7 CPU Board.
For the technically oriented, the System7 EPROM configuration uses the original 2716 System6 IC14 Firepower EPROM on the System7 CPU at IC20. The new System7 2716 IC14 EPROM is a binary copy of the three original 512 byte PROMs (that lived at IC21+IC22+IC26 on the System6 CPU board). And of course the 2532 Flipper EPROM at System7's IC17 is a binary copy of the two original "green" Flipper EPROMs, as described above.
System6 and System7 Sound and Speech Board Jumpers.
* Hyperball sound board note: The above information
is different than the information which came from Williams.
But the above jumpers have been confirmed as correct!
Note a 6802 sound board processor can be installed and the old 6808
and 6810 RAM (IC11) removed. To do this,
a trace must be cut on the back of
the board below R30. It looks like Williams had a bit of a conflict of
interest here because the pull-up resistor is in place for the processor
swap but the resistor is permanently grounded until the trace is cut.
System3/4 Sound Board Jumpers.
CPU Board DIP Switches - Reseting Audits and Factory Settings.
If running a system3 game on a later system7 CPU board,
DIP switches are still used (as the software is written
for DIP switches). This is important to keep in mind since
many system7 CPU boards do NOT have the DIP switches installed
(though the user could install them on the board).
If running any system4 to system7 game on any CPU board,
all 16 DIP switches
on the CPU board should be set to OFF (right most position).
The game isn't using these anyway, but it's just a good
idea to set them all to 'off'.
System3 to System7 games did use the three upper switches
of the 16 DIP switches
(switches 8,7,6 on the upper DIP switch bank).
These were used for zeroing the audit totals, restoring
factory settings, and auto-cycling mode (frankly zeroing
audits and restoring factory setting can be done easier by
just removing the AA batteries in the battery
holder for 10 seconds).
Here are the system3 to system7 DIP switch reset/auto-cycle
options. All upper bank CPU DIP switches
assumed to be OFF (or to the standard game settings on system3),
except as noted below. Again, I don't find this particularly
useful (or easy to use!), but here it is:
To activate any of the above, follow these steps:
This information applies to all system3 to system7 driver boards
(with the exception of Hyperball, which used a unique driver board).
Lamp Matrix Power Resistors.
The other problem of the 27 ohm resistors relates to CPU lock ups.
If the CPU board locks up (Scanbe sockets strike again!), the lamp matrix
voltage will no longer strobe. This will definately heat up those resistors enough
to desolder them from the driver board.
Yet another option to fix the burnt resistors is an idea documented by C.Eddy.
He replaces the eight TIP42 lamp matrix transistors (Q63, Q65, Q67, Q69, Q71, Q73, Q75, Q77)
with IRF9z34N or FQP17P06 mosfets (the FQP17P06 are more robust and generally cheaper.)
The MOS-FETs are installed oriented
just like the TIP42 transistors. And the mosfets only need a tiny amount of
current to drive them (compared to the TIP42 transistor),
hence the large power resistors at R149-R156 never get hot. Because
of this there is no need to replace the large resistors (the old burnt ones
can be left installed, unless they are open). Heck if the TIP42s are replaced with
Irf9z34n or FQP17P06 mosfets the power resistors R149-156 can even be replaced with jumper wires
or zero ohm resistors.
The decrease in these switch matrix resistor ohms was done to increase
the current drive through the switch matrix.
For example, if a switch or connector was dirty and had slight
resistance, the switch could still be sensed by the CPU/Driver board.
There is a rumor that using a jumpered system7 style driver board in a System6 or earlier
game may result in random switch closures during game play. This does not
seem to be the case (but keep it in mind if having random switch closure problems).
One thing for sure though is using
a non-jumperd System3 to system6 driver board game in a System7 game
will definately result in switch closures being missed.
Part of the problem Williams was having with switches was due to
an assembly mistake, which started in the mid-1970s (pre-solidstate).
It turns out Williams was assembling one of the pair of leaf blades
backwards. This was not a huge deal with Electro-Mechanical (EM) games,
but with solidstate games, it was a BIG problem. Because solidstate
games use low voltage (5 volt) switches (unlike EM games in which all
switches were high voltage 28 volts), the contact rivets are gold
plated to help keep them clean (gold is a non-corrosive metal).
But because one of the switch blades
was reversed, a gold plated switch rivet made contact with a gnarley rough
non-gold plated switch rivet. Problems occurred mainly with any switch
where a ball "sat", like the ball trough, lock or kickout hole.
This mistake was not realized until the Firepower
era, and Williams offered retrofit kits for Firepower and Black Knight
ball troughs using microswitches to fix the problem.
Replace the Driver Board Female Interconnector Pins.
Resolder the Header Pins.
Driver Board Transistors.
Important Note: Testing transistors (or chips) using the methods below
does not give 100% proof that the component is good or bad!
It's probably about 95% accurate, but it is not 100% accurate.
All transistors are tested using the diode function of a DMM
(Digital Multi Meter).
Testing the TIP120 (or TIP102).
Testing the 2N4401.
Testing the 2N6122 or TIP41 (TIP41 is a sub for the 2N6122).
Testing the TIP42.
Testing the 2N6427 (or MPSA14 or NTE46).
Testing the 2N5060.
The Coil Diodes and Why they are Important.
Since you spent the time to test/replace the bad driver
board transistors, it only makes sense to also check for
bad coil diodes. Since these 1N4004 diodes are mounted
right to the coils under the playfield, vibration can crack
or damage them.
The best way to test a coil diode is to just grab the diode by
its body with the forefinger and thumb, and gently give
it a pull. If the diode has a cracked body or broken
lead, it should be pretty easy to see.
In all situations, remember to mounted the new diode correctly.
For example, on coils, install the diode with the
diode's band on the power lug of the coil. It usually pretty easy
to tell which is the power lug of a coil. The power wire, which daisy
chains from coil to coil, is usually the thicker wire on a coil
lug. The banded lead of the 1N4004 diode should be connected to the
coil lug with this thicker daisy chained power wire attached.
The non-banded end of the diode attaches
to the coil lug with the thinner wire, which leads to the driver board transistor,
and ultimately ground.
Burnt General Illumination (GI) Connectors on System3 and System7.
To fix burnt GI connectors, they must be replaced completely.
That means both the circuit board mounted connectors AND the
wire mounted connectors. The output GI connector, a straight .156" header, is no
problem (part number listed above in the non inter-board connector section).
Just make sure to use
Trifurcon pins for the wire mounted connector
(they have greater surface area, and last longer than standard pins),
and a new square 9 pin .156" header for the circuit board.
Note on system7 games
there is often a connector the breaks the GI playfield wiring harness for removal
of the backbox. This connector will usually have 6.3 volt AC
yellow and purple wires, and white wires with yellow and purple traces.
Also sometimes this connector will have
12 volts DC too - this powers any under-playfield GI relays (if the game uses them).
The Single Pin Cabinet/Backbox G.I. Connector.
To summarize, get these parts to repair the GI connectors on Hot Tip/Lucky
Seven and System7 power supply board:
G.I. Relay Replacement.
System3/4 Sound Board Jumpers.
CPU Board DIP Switches - Reseting Audits and Factory Settings.
If running a system3 game on a later system7 CPU board, DIP switches are still used (as the software is written for DIP switches). This is important to keep in mind since many system7 CPU boards do NOT have the DIP switches installed (though the user could install them on the board).
If running any system4 to system7 game on any CPU board, all 16 DIP switches on the CPU board should be set to OFF (right most position). The game isn't using these anyway, but it's just a good idea to set them all to 'off'.
System3 to System7 games did use the three upper switches of the 16 DIP switches (switches 8,7,6 on the upper DIP switch bank). These were used for zeroing the audit totals, restoring factory settings, and auto-cycling mode (frankly zeroing audits and restoring factory setting can be done easier by just removing the AA batteries in the battery holder for 10 seconds).
Here are the system3 to system7 DIP switch reset/auto-cycle options. All upper bank CPU DIP switches assumed to be OFF (or to the standard game settings on system3), except as noted below. Again, I don't find this particularly useful (or easy to use!), but here it is:
To activate any of the above, follow these steps:
This information applies to all system3 to system7 driver boards (with the exception of Hyperball, which used a unique driver board).
Lamp Matrix Power Resistors.
The other problem of the 27 ohm resistors relates to CPU lock ups. If the CPU board locks up (Scanbe sockets strike again!), the lamp matrix voltage will no longer strobe. This will definately heat up those resistors enough to desolder them from the driver board.
Yet another option to fix the burnt resistors is an idea documented by C.Eddy. He replaces the eight TIP42 lamp matrix transistors (Q63, Q65, Q67, Q69, Q71, Q73, Q75, Q77) with IRF9z34N or FQP17P06 mosfets (the FQP17P06 are more robust and generally cheaper.) The MOS-FETs are installed oriented just like the TIP42 transistors. And the mosfets only need a tiny amount of current to drive them (compared to the TIP42 transistor), hence the large power resistors at R149-R156 never get hot. Because of this there is no need to replace the large resistors (the old burnt ones can be left installed, unless they are open). Heck if the TIP42s are replaced with Irf9z34n or FQP17P06 mosfets the power resistors R149-156 can even be replaced with jumper wires or zero ohm resistors.
The decrease in these switch matrix resistor ohms was done to increase the current drive through the switch matrix. For example, if a switch or connector was dirty and had slight resistance, the switch could still be sensed by the CPU/Driver board.
There is a rumor that using a jumpered system7 style driver board in a System6 or earlier game may result in random switch closures during game play. This does not seem to be the case (but keep it in mind if having random switch closure problems). One thing for sure though is using a non-jumperd System3 to system6 driver board game in a System7 game will definately result in switch closures being missed.
Part of the problem Williams was having with switches was due to an assembly mistake, which started in the mid-1970s (pre-solidstate). It turns out Williams was assembling one of the pair of leaf blades backwards. This was not a huge deal with Electro-Mechanical (EM) games, but with solidstate games, it was a BIG problem. Because solidstate games use low voltage (5 volt) switches (unlike EM games in which all switches were high voltage 28 volts), the contact rivets are gold plated to help keep them clean (gold is a non-corrosive metal). But because one of the switch blades was reversed, a gold plated switch rivet made contact with a gnarley rough non-gold plated switch rivet. Problems occurred mainly with any switch where a ball "sat", like the ball trough, lock or kickout hole. This mistake was not realized until the Firepower era, and Williams offered retrofit kits for Firepower and Black Knight ball troughs using microswitches to fix the problem.
Replace the Driver Board Female Interconnector Pins.
Resolder the Header Pins.
Driver Board Transistors.
Important Note: Testing transistors (or chips) using the methods below does not give 100% proof that the component is good or bad! It's probably about 95% accurate, but it is not 100% accurate.
All transistors are tested using the diode function of a DMM (Digital Multi Meter).
Testing the TIP120 (or TIP102).
Testing the 2N4401.
Testing the 2N6122 or TIP41 (TIP41 is a sub for the 2N6122).
Testing the TIP42.
Testing the 2N6427 (or MPSA14 or NTE46).
Testing the 2N5060.
The Coil Diodes and Why they are Important.
Since you spent the time to test/replace the bad driver board transistors, it only makes sense to also check for bad coil diodes. Since these 1N4004 diodes are mounted right to the coils under the playfield, vibration can crack or damage them.
The best way to test a coil diode is to just grab the diode by its body with the forefinger and thumb, and gently give it a pull. If the diode has a cracked body or broken lead, it should be pretty easy to see.
In all situations, remember to mounted the new diode correctly. For example, on coils, install the diode with the diode's band on the power lug of the coil. It usually pretty easy to tell which is the power lug of a coil. The power wire, which daisy chains from coil to coil, is usually the thicker wire on a coil lug. The banded lead of the 1N4004 diode should be connected to the coil lug with this thicker daisy chained power wire attached. The non-banded end of the diode attaches to the coil lug with the thinner wire, which leads to the driver board transistor, and ultimately ground.
Burnt General Illumination (GI) Connectors on System3 and System7.
To fix burnt GI connectors, they must be replaced completely. That means both the circuit board mounted connectors AND the wire mounted connectors. The output GI connector, a straight .156" header, is no problem (part number listed above in the non inter-board connector section). Just make sure to use Trifurcon pins for the wire mounted connector (they have greater surface area, and last longer than standard pins), and a new square 9 pin .156" header for the circuit board.
Note on system7 games there is often a connector the breaks the GI playfield wiring harness for removal of the backbox. This connector will usually have 6.3 volt AC yellow and purple wires, and white wires with yellow and purple traces. Also sometimes this connector will have 12 volts DC too - this powers any under-playfield GI relays (if the game uses them).
The Single Pin Cabinet/Backbox G.I. Connector.
To summarize, get these parts to repair the GI connectors on Hot Tip/Lucky Seven and System7 power supply board:
G.I. Relay Replacement.
3a. When Things Don't Work: Power On, Funky Score Display Numbers (Battery/5101 RAM Problems)
Dead batteries (or worse, dead corroded batteries) will cause problems getting a system4 to system7 game to power-up properly. On these games, if the batteries are dead, the game can still boot, but will come up in "audit" mode (system3 games do not have this boot-up audit mode). To get to attract mode, turn the game off and on again quickly. If done fast enough, the game should come up in attract mode. Note on System6 and System7 games, the coin door *must* be open for this to work (memory protection switch open).
If the game still doesn't come up in attract mode, even with the "turn it off and on quickly" trick, the CMOS 5101 RAM chip at IC19 is probably bad.
Please refer back to the Batteries and Battery Holders section for more information on this subject, including how to test the batteries, blocking diode D17, and the CMOS 5101 RAM at IC19.
Booting into Audit Mode Explained.
These software identification numbers made it easy to see if the wrong Game and/or Flipper ROM software was installed in the machine.
Note the lack of a code for White flipper ROMs (system3). This is because the boot-up "software versions" was not implemented until System4 and the Yellow flipper ROMs, when adjustment were also stored in memory (system3 used DIP switches for the adjustments). Williams did the audit mode routine to show instantly upon power-on that the game's adjustments/audits were lost, and that the batteries needed to be replaced. The main reason this was done was to protect the game from having garbage in an adjustment that may put the game into free play (or some other equally accidental bad mode), since now all the game's adjustments were store in memory instead of being "hardcoded" with DIP switches. With system6 and its memory protection circuit/coin door switch, it also keep miscreants from drilling through the bottom of the game and activating the switches to change the settings (like one quarter equals 25 credits!), since the coin door now had to be open to change an adjustment/audits.
3b. When Things Don't Work: Fixing a Dead CPU (LED code, Test EPROM, Blanking)
For info on the Blanking signal, chick
here to jump down to that section.
Introduction to CPU/Driver Board Repair.
System3 to System7 games were designed so that a field tech would only have to swap out a failed board, and then send the board to the distributor for repair. The boards were not designed to be diagnosed and fixed on location. Looking at the Williams "repair" manuals, the instructions tell pretty much only how to pinpoint which board is bad. The final "fix" of most repair steps in a Williams manual is to "replace the board". Unlike more recent games which report many problems, early Williams board provided little diagnostic help. This was unlike the approach Bally took with their famous "seven flashes" diagnostic system (which makes component level repair pretty easy).
Where Bally took the approach that the boot-up diagnostics were very important and game diagnostics were not, Williams took the opposite approach that boot-up diagnostics were *not* important but game diagnostics were! Hence 1977-1985 Bally games have the famous power-on seven flash test, but don't really have a lamp, display, coil or switch test. Williams system3 to system7 games have basically no significant power-on test indicator, but do have good versions of lamp, display, coil and switch tests (assuming that the Williams game in question will boot up properly!)
Initially, when these games were new, Williams pinballs were dependable, about as good as Bally games (and better than Gottlieb' system80). But after a few years, as the Scanbe sockets got old and the 40 pin interconnector wore, dependability of these games made them way worse than Bally (and probably on par with Gottlieb). And with no power-on indicator system like Bally had, operators didn't even know where to start with a Williams repair.
It's not that the Williams system is "hard" to fix, it's just time consuming. Where the Achilles' heel of the Bally system is battery corrosion and Gottlieb had board connector and ground issues, Williams System3 to System7's Achilles' heel is the design of the boards themselves. Passing address and data lines over a 40 pin .156" Molex interconnector is a bad idea. If *any* address or data line drops out for even a millisecond, the whole game locks up. Same thing with the Scanbe sockets; if a single pin become intermittent on any Scanbe socket, the game locks up. Add vibration to the mix, and things only get worse. Having some PIAs on the CPU board and some PIAs on the driver board forced the address and data lines to cross the two boards at this Achilles' heel (the 40 pin interboard connector). And if the game locks up when a coil is energized, that can take out more components on the driver board, making the repair even worse.
Also some components on the Williams System3 to System7 boards are obsolete and unavailable. For example, the System3/4 clock chip (MC6875) is obsolete and impossible to find. This is the companion clock chip to the 6800 CPU processor. Luckily, the MC6875 doesn't fail too often. Also the 8T28 and 8T97 chips are discontinued (there is a work arounds for most of those). But this is why many repair facilities will not repair Williams System3 or System4 CPU boards.
To make matters even worse, the software contained in the "flipper ROMs" (essentially the operating system) adds to the problems. If any of the PIAs can not be found in the exact state the software expects, this locks up the software, and hence the entire game. So say the solenoid PIA is partially dead (common, because of a locked-on driver transistor which cascaded back to the PIA and damaged it). This may make a coil or two not function. That's fine; the game maybe could still be operated and played without a bumper or two. But instead, the whole game locks up and becomes useless. And because the CPU is locked up, diagnosing the problem becomes very difficult too.
To add insult to injury, the driver board is an integral part of the CPU board. That is, the CPU board will *not* run without a functioning driver board attached! (Unless a special test EPROM is used, which has only recently became available.) So the whole theory of spliting the system into smaller components (a separate CPU and separate driver board) for easier diagnostics is missed*. The two boards need each other, and are linked together through the incredibly stupid and troublesome .156" 40 pin interconnector. This is unlike Bally and Gottlieb, where their CPU boards can be run independently of the driver board, making diagnosing problems much easier, since the system can be broken down into smaller, more managable pieces.
* Note there is a trick that allows the Williams CPU board to (semi) boot without the driver board. The driver board can be completely removed from the game, and the CPU board booted. If the CPU board is OK (trying to run), the two CPU LEDs will blink on, then go off, and then come on steady (since the CPU board is looking for the Driver Board). If installing the Driver Board locks the CPU (LEDs steady on, no blinking at bootup), then the CPU board is probably Ok (and there's problems on the Driver Board.) On a system7 CPU board, if the CPU were OK (or trying to run) the Numeric Led would blink �0�, go off and come on steady (looking for the Driver Board). If putting the Driver Board back in locks up the game ("0" steady on), then there are some problems on the Driver Board
The Internal System3-System7 Diagnostic Firmware.
To make matters even worse, the diagnostic SW1 test, even on a working CPU board, can confuse even a veteran user. The diagnostics are a memory test only, and tests the CMOS RAM IC19 (5101) and the two static RAM chips (IC13/IC16). But the static RAMs IC13/IC16 rarely die. And the user will already know if the CMOS 5101 RAM is dead well before the diagnostics are run. If the game boots into "audits" mode, and the CPU batteries are good, it's 99% for sure the 5101 RAM is dead.
Also, even if the CPU board has seemingly "booted correctly", the flipper ROMs IC17 and IC20 can still have problems. These two ROMs hold the diagnostic code, and if one of these ROMs has a problem, false indications can result from the SW1 diagnostic switch (but usually the CPU board didn't boot anyway and the LEDs are indicating a locked-up board, and these two ROMs don't even get a chance to start working).
To make matters worse, the diagnostic LEDs just tend to confuse the newbie repair person. For example, the CPU board does not boot, but the user presses the diagnostic switch SW1 anyway. The LED reports back the suspected failed component. But that's the problem... since the CPU board never booted properly, the output from the diagnostic test CAN NOT be trusted! What ever the test indicates is surely incorrect, and the newbie is replacing good CPU board components, based on the failed/incorrect test results (I believe this is called, "chasing one's tail"). This is especially a problem if the newbie came from "Bally world", where Bally's LED actually has good boot-up component diagnostic results.
The bottom line is this: if the Williams System3-System6 CPU board's LEDs lock-on at power up, the CPU board is not working! Likewise for System7, if "0" comes on immediately at power-up, the CPU board is not working. Why that is happening, well, you're on your own to figure it out! Because the Williams diagnostic firmware is *not* going to help.
OK, So That's the Bad News. What's the Good News?
Again, use the simple test to trick the Williams CPU board to (semi) boot without the driver board. The driver board can be completely removed from the game, and the CPU board booted. If the CPU board alone comes on with both LEDs on (no blinking), then the CPU board is faulty. If the CPU board is OK (trying to run), the two CPU LEDs will blink on, then go off, and then come on steady (since the CPU board is looking for the Driver Board). If installing the Driver Board locks the CPU (LEDs steady on, no blinking at bootup), then the CPU board is probably Ok (and there's problems on the Driver Board.) On a system7 CPU board, if the CPU were OK (or trying to run) the Numeric Led would blink �0�, go off and come on steady (looking for the Driver Board). If putting the Driver Board back in locks up the game ("0" steady on), then there are some problems on the Driver Board
Before removing any boards from the game, and assuming the power supply is working, it's time to do some preliminary diagnostics. Remove the game's backglass, so the CPU board's LED(s) can be seen (if the CPU board in question is not in the game, it can be powered up "on the bench" with an external +5 volt power supply, those details are below). Right now, before doing anything, remove fuse F2 (solenoid power) and fuse F3 (lamp matrix power) from the power supply board. Now go ahead and power the game on, keeping an eye on the LED(s) on the CPU board. Here's a list of what could happen:
Get Leon's CPU Test EPROM.
EPROM Tip: If getting an EPROM burned is really a big deal, the System3 to System6 version of Leon's test EPROM can be "doubled up", burned into a 2532, and used in *any* System3 to System7 CPU board. Yes the 2532 is twice the size of the expected 2716 at IC17 on a System3 to System6 CPU board. But because of the way a 2532 EPROM is addressed, the added address space of the 2532 will just be ignored by the System3 to System6 CPU board. But there is a downside to this; Leon's memory test will *not* work in a system7 CPU board. This is because memory for System3 to System6 is at locations $0080 to $0100, and in System7 memory is located from $0000 to $0100 (but the basic part of Leon's test ROM will work, but the memory test will not). This works in a pinch if the correct EPROM is not available.
After the above EPROM code is downloaded and burned into the appropriate EPROM, remove all the existing ROM/EPROM chips from locations IC17, IC20, IC14 (and IC21, IC22, IC26, but there should not be any chips in those locations anyway if the CPU board was converted to EPROMs and new sockets installed). Now installed Leon's test EPROM into the flipper ROM socket at IC17.
Note: Leon's chip will work with the other ROM chips installed. This happens because Leon's test program starts at the "boot up" memory location, and it does not access the other ROM chips. So basically the other ROM chips get ignored, as Leon's chip is accessed first at power-on, after the CPU board resets. BUT I highly recommend removing ALL the other ROM chips! If one of the other ROMs is bad (shorted), it could "lock up" the CPU board. By removing them, it's just one less thing to go wrong.
Separate the CPU board from the Driver Board.
Booting the CPU board on the "Bench" with an External Power Supply.
The next trick to fixing a CPU/driver board is to move the boards from the game and to the work bench. In order to do this, an old AT style computer power supply that outputs +5 volts DC (and +12 volts) is needed. These are pretty easy to come by, any computer store should have one for free to $20 dollars (heck new AT computer power supplies can be purchased too for less than $30). An old video game switching power supply can also be used.
Newer ATX power supplies can also be used, but these do not have a physical power switch. Instead they get a signal from the computer's motherboard connector to turn the power supply off. But these power supplies can be fooled to turn on when their power cord is plugged in. Just tie the green /PS-ON wire (power supply on, active low, normally pin 14 on the motherboard connector) to the black COM ground wire. (a diagram of the 20-pin ATX connector can be found at wired.hard.ru/data/atxpower.shtml).
After the power supply is obtained, power it up and figure out which wires are the ground COM (usually black), +5 volts DC (usually red), and +12 volts DC (optional, but usually yellow). Use a DMM to test the voltages. Turn the power supply off. Now get three alligator clip test leads, and hook up the power supply to the CPU board's connector 1J2 as follows:
* Is the Unregulated +5 Volts Needed?
To get around not connecting power to the unregulated +5 volt power pin on System6 to System7 CPU boards, try the board first without the unregulated +5 volts. If it doesn work, use an alligator jumper clip and do this: Connect the power supply's +5 volts (the electroylic cap C23's positive lead) to resistor R27 (see which side of R27 in the bullet points below). Because the layout of System6 and System7 is different, pay particular attention to the instructions below. Because one side of R27 is ground, and connecting +5 directly to ground would cause the power supply to short. So be careful which side of R27 is used! In all cases, cap C23 and resistor R27 are just to the right of connector 1J2 on the CPU board.
At Power-Up, the LEDs or 7-Segment Display Does not Come On.
If there's no +5 volts at the CPU chip, then trace back through the power circuit to see where it's losing power. Check to make sure there isn't a short to ground. There are capacitors (.01 mfd non-polarized) at the Vcc (+5 volt) connection of each chip on the board to ground. Check each one of these for a short. Also check the board very carefully for solder splashes. Remember a prior repair may have gone bad and the board was junked for this reason.
On System3 to system6 boards, check for +5 volts at IC2 pins 2,5,16 (the 8T28 that drives the LEDs). Also remember both LEDs could be bad! The LEDs will always come on at power-up unless turned off by an executing program on the CPU board. If there is proper voltages on the board, but no voltage at pins 2 and 5 of IC2, check for a running CPU chip (see below). If there is CPU activity on the address and data lines, then the problem is most likely IC2 (8T28) on system3 to system6 boards.
On System7 CPU boards, if there is no activity on the 7-segment display, it is common for IC34 (7447) segment driver chip to fail. This will give a false indication that the board is completely dead or that there's no power. Using a logic probe, test for pulsing at IC1 pin 15 of the CPU chip. If there is activity there, then the problem is most likely IC34 or the segment LED itself. Also if the LED comes on and stays on (even though the game is seemingly working fine), often IC2 (74125) has shorted internally.
Note two test LEDs (like on system3-6 CPU boards) can be added to the System 7 CPU board. This will allow testing to the board before replacing IC34 and/or segment LED. All that is needed is two LEDs and two 100 ohm 1/4 watt resistors. Solder the two resistors into the board, just to the left of test point TP9. The LEDs then should be soldered into the two top pads pairs next to the segment LED, with the flat side of the LEDs towards the 7-segment LED. With the two LEDs installed, they will "flash" just as the LEDs flash on system3 to system6 CPU boards.
Ok, so the CPU board is all ready, with the test EPROM installed, power supply connected, and the driver board removed. Now we can power on the CPU board. But first, it would be helpful to know what is happening, and how to check it.
Here are the steps involved in a correctly booting CPU board. In the case of a dead CPU board, each step can be diagnosed with a DMM and/or logic probe.
How to Tell if a CPU Board is Locked-up or Good.
For System3 to System6 CPU boards with game software installed, a good working and fully booted CPU board will, at power-on, flash both LEDs for a moment, and then turn both LEDs off. A locked-up System3 to System6 CPU board will have either or both of the LEDs turned on and stay on when the CPU board is powered on.
On System7 with game software installed, a good fully working and booted CPU board should flash the 7-segment LED or the two small LEDs next to the 7-segment, seeing a "0" briefly on the 7-segment display. Then the LED(s) go out and should *not* come back on. If there is a "0" from the instant the power is turned on, with no flicker or activity, then the System7 CPU board is locked up.
In addition, if the CPU board is up and running, the blanking signal will be high (around 4 volts). This is pin 37 of the 40 pin interconnector, or CPU connector IJ3 pin 4. The blanking signal can be fooled into being high on a non-working CPU board, or it can never go high on an otherwise working CPU. But for the most part, a working CPU board will have a high blanking signal.
Running Leon's EPROM "bare bones."
How to Tell if Leon's Test EPROM is Running.
The LEDs Come On & Stay On (or 7-segment display shows "0").
The Leon test ROM and the game program do this by setting the output ports PA6 through PA10 on CPU IC18 (the 6821 display PIA) low. If the test or game program isn't running, these ports remain high, and the LEDs/segments stay on.
When the MPU board is powered on, the CPU chip attempts to read addresses $FFFE and $FFFF in EPROM chip IC17 (the test ROM or flipper ROM 2) to obtain the jump address for the program to execute. This program then takes over and controls the LEDs. If the program is not able to start reading IC17, then the LEDs stay locked on.
The standard game software in IC17 then tries to read and write to the RAM chips IC19, IC16, IC13, and to all the PIAs on both the CPU and driver board (this of course assumes that the boot up process got far enough to run the program in EPROM IC17!) If there is any problem encountered, the program will lock up and not turn off the LEDs. The Leon test ROM however will run even if the PIAs or RAM chips are bad (or missing for the most part), so this narrows down the areas to check if the test ROM doesn't start its alternating LED on and off rythmic flash pattern.
Good Reset and Clock but No 'Leon' Alternating LED Flashes.
Some of the above chips can be just removed from the CPU board with Leon's test EPROM. For example, the CMOS RAM at IC19 (5101) can be removed. Also the static RAMs at IC13/IC16 can also be removed. Removing these chips on a dead CPU board with Leon's test EPROM is a good idea. If these chips have a short, removing them may allow the CPU board to boot. This especially applies to the 5101 chip at IC19.
If the CPU board PIA at IC18 is bad, it may prevent Leon's program from flashing the LEDs. Using a test LED (as decribed below) and *not* a logic probe, connect the non-resistor end to +5 volts, and touch the other resistor lead of the LED to the CPU IC1 pin 15. If the test LED flashes on and off about once a second, then the test program is running, and the CPU board PIA at IC18 needs to be replaced.
The next thing to check now is if the CPU chip is running the program in the test EPROM. Use a logic probe and test CPU IC1 for pulsing activity on the address lines A0-A7 (pins 9-16), data lines D0-D7 (pins 33-26) (and perhaps address lines A8-A10 pins 17-19). If the CPU is running a program, there should be some pulsing on these pins. If even one of the A0-A7 or D0-D7 pins is low or high (not pulsing), then the CPU can not do its job and properly run the program in IC17. If there are pulsing signals on just some of these pins, then the CPU is trying to run, but the test program can't run correctly.
For both the address and data bus lines, use a DMM and check the continuity between lines. There should be no shorts between any of the data and address lines! Use a DMM and start with address line A0, checking continuity between IC1 address lines A1 through A15 (IC1 pins 9-20, 22-25), and data lines D0 through D7 (IC1 pins 33-26).
Solder splashes and solder bridges are quite common, especially if chip sockets have been replaced during previous repairs. If a socket was replaced, or testing a board that never worked, a previous repair attempt may have resulted in a short between lines.
While testing the address/data lines, its a good idea to test address and data line continuity between chips. That is, does address line A0 go from IC14, to IC17, to IC20 (and to IC26 on System7 boards), and finally back to the data and address buffer/amplifier chips (except on system6a CPU boards) and the CPU chip IC1 (more on these buffer/amplifier chips below).
Address Bus Signals.
Luckily these chips IC3/IC4/IC8 are easy to check using a logic probe. The CPU chip IC1 is connected to IC3/IC4/IC8's input even numbered pins 2-6,10-14, and the rest of the address bus is connected to the ouput odd numbered pins 3-13. For example, the address signals should be identical on both pin pair (input and output):
Finally IC8 handles address lines plus the R/W (Read/Write) and VMA (Valid Memory Address) lines. If identical signals are not seen on each pin pair shown above, then replace the offending 8T97. The part number is obsolete, but can be replaced by a 74LS367 or 74LS365.
Also if an address line is missing, use the appropriate IC3, IC4, or IC8 chip as an "anchor point" for your DMM set to continuity. This way continuity can be check for the missing address line between the ICx chip and the PIA, ROM and RAM chips.
Diagnosing & Removing Data Bus Chip IC9/IC10 (Prior to System6A).
The data bus was originally designed in the same manor as the address bus with two data buffer transceivers chips. The are transceivers since signals go both way on the data bus, and are used to amplify the data signals. On System3-6 CPU boards these are the obsolete 8T28 chips. On the System7 CPU boards one (avialable!) 74LS245 is used at IC9. System 6A boards eliminated the data buffers entirely.
I personally don't recommend removing these chips unless they are known to have a problem. There is some risk involved (see below).
How does someone know if IC9/IC10 are bad? (Remember, all this only applies to System3 to System6 CPU boards.) This is done in the same manner as the address buffer 8T97 chips mentioned above. Using a logic probe, look at the input signals to the IC9/IC10 chips. The output signals should look identical (pulsing). If they are not, there's a good chance the chip is bad. Data lines D0-D3 are connected to IC10, and data lines D4-D7 are connected to IC9. The CPU data lines are connected to pins 2/4, 5/7, 9/11 and 12/14 of IC9 and IC10. The data bus is connected to pins 3,6,10,13. The same pulsing waveforms should be seen on the pins 2/4-3 combination, 5/7-6, 9/11-10 and 12/14-13. If not getting the same readings on both input and out sides, then the chip is bad.
If all went well above, repeat steps 5 through 9, but with IC10. After the board is up and running, replace the 5101 RAM at location IC19. The reason this chip was removed is simple. If a mistake was made in the above procedure, it will FRY the 5101 RAM! These chips are hard to get and somewhat expensive now, so it's a good preventitive measure to remove the chip while testing this procedure. If the board won't boot, and the two LEDs are locked on, either there are other problems with the board or some mistake was made in the above installation.
The Read/Write lines.
The Valid Memory Address line. The 6800 series of microprocessors do not always place a valid memory address on the address bus, so a VMA signal is required to verify a valid memory address. The VMA line is high whenever a valid address is placed on the address bus, and is used as part of the chip selection circuits. If the VMA line never goes high, then a memory address will never be selected. The VMA line originates on the IC1 pin 5 CPU chip, and passes through the data buffer chip IC8 pins 13,14 (System 3/4 CPU boards have some additional logic chips on the CPU side of the VMA line, including IC7, IC11, IC12). Check the VMA at the IC1 pin 5 CPU chip and IC8 pin 14, as these pins should be high.
CPU Chips Not Needed to Run Leon's Test ROM.
On system7 CPU board, the list is a bit different, as there are a lot more chips not needed by Leon's test ROM. System7 CPU chips not needed to run Leon's test ROM include IC5 (74LS02), IC6 (74154), IC10 (4071), IC11 (74LS10), IC12 (7408), IC13/IC16 (2114 RAM), IC19 (5101 RAM), IC25 (4020), IC35 (sound PIA) and the ROMs at IC14/IC20/IC26.
Leon's Test Chip is Running, Now What?
What his test program is doing is testing all the PIA chip(s) on the CPU board and driver board (if attached, which it's *not* right now!) PIA inputs are tested as outputs by Leon's test program; this puts the inputs (and hence then the outputs) of PIA chip(s) PA0-PA7 high, then low, high, then low, over and over again. While Leon's program is doing this, the PIA's pins can be easily viewed alternating high and low using a tester LED or a logic probe. Though this isn't the perfect test method, any repair person will say they never see a PIA working in output that did not work at input. The structure of the PIA chip is complex and any damage to the output pins (and inner structure) by over voltage or over current always affects the whole PIA's input/output at that particular pin.
At this point a logic probe and a "tester LED" is needed. If a logic probe is not available, go to Radio Shack and buy one for $20.
The "tester LED" needs to be contructed using a LED and a 150 ohm resistor. Solder the resistor to the FLAT SIDE of the LED. A wire can be soldered to the non-resistor leg of the LED (or just connected an alligator test lead). The wire or alligator test lead will then (normally) be connected to +5 volts. Use the resistor lead on the LED as a test probe lead. I personally have found it easier to probe with the resistor side of the LED, hence the tester is assembled in this manner.
Now use the tester LED or the logic probe to check each of the PIA's outputs. Personally I prefer using the tester LED for this, as the tester LED indications are very clear (a logic probe can show noise, and is often confusing). Connect the non-resistor lead of the tester LED to +5 volts (TP9 on system6/7 CPU boards, or interconnector pin 1 on the far right). Use the resistor end of the tester LED to probe each PIA pin desired. If being tested in the game, be sure to remove power supply fuses F1 (H.V.), F2 (coils) and F3 (lamps) before powering on.
If one of the PIA pin specified below is not alternating high then low on the tester LED, that PIA chip is proabably bad. Leon's program moves the PIA's outputs high and low once a second, so it's real easy to see this with the tester LED (the LED blinks on and off about once a second). This is very cool, as PIA chips are normally hard to diagnose any other way, even with a logic probe.
Here are the CPU board's IC18 PIA pins to check for the alternating high and low signal on the CPU board:
If any IC18 pin 2-17 are not alternating high then low, then the PIA is bad. Remove the chip, install a socket and a new PIA 6821 chip.
* Note Leon's chip also tests pins 19 and 39 on the PIAs. These are the CA2 and CB2 ports. Each 6821 has these two "special" ports (in addition to the eight ports at PA0-PA7/PB0-PB7), which are used mostly for the Special Solenoids. If CA2 or CB2 is labeled as a "STx" port on the schematics, that means it controls a Special solenoid when the game is in diagnostics. Keep that in mind.
On system7 CPU boards, the sound PIA at IC36 can also be tested with a logic probe, as Leon's test program is triggering this PIA too. Test all the IC36 pins listed above, with exception, IC36 pin 9 (PA7). This pin will be either high or low (depending on a CPU board jumper setting), and will not be alternating. Note this PIA does not use the CA2/CB2 ports to my knowledge.
Leon's test chip also alternates high and low the Blanking signal on the CPU board. This can be easily seen on pin 37 (fourth pin from the left) of the inter-connector.
Tester LED not Flashing, but PIA is Good?
On the CPU PIA pin 4, it goes to two other chips (IC6 pin 21 and IC7 pin 11). IC6 is the 74154 BCD decoder, which takes four signals from the PIA and turns it into a bunch of output strobes for the score displays. IC7 is a 7404 inverter support chip for the 556 timer. All these chips were soldered in place. So what I did was cut the IC6 pin 21 leg at the board, and bend it up a bit. Powered back on, and the Tester LED on CPU PIA pin 4 was still locked on. Power off and resoldered the cut and bent IC6 chip leg. Then I cut and bent IC7 pin 11's chip leg. Rebooted, and now the PIA pin 4 pulsed on and off with the Tester LED, just like it should.
So the bottom line was that even though Leon's test chip indicated the CPU PIA was bad, it really wasn't (IC7 7404 was bad). Replacing IC7 with a new 7404 fixed the problem, and now the CPU board booted and worked fine.
So here's a list of CPU PIA output pins that go to other chips. These PIA output could test "bad" by the Leon Tester LED, yet the PIA could still be good. (The chip the outputs goes too could be holding the signal high or low.)
Another example of this was on the PIA ic18 pin 9. Again, not flashing with Leon's test ROM, but the problem wasn't the PIA. Instead it was the 8t28 which connected to ic18 pin 9. Pulling the 8t28 chip allowed the PIA ic18 pin 9 to start flashing again, meaning the 8t28 had a problem.
Leon's Memory Test.
Leon's memory test NO LONGER requires the "Test LED" as a test indicator. Everything is done with the on-board CPU LEDs (thanks Leon for making this change). The old method using his Test LED can still be used though (but note a logic probe can *not* be used for this). Very thin/small pulses can occur on this test, and these are too tiny for the LED indicator to see. But with the logic probe of course these pulses are detected. Hence a logic probe will give confusing and contridicting results.
The "New" Leon Memory Test (11/01/03 and later):
System 3 to 6 CPU boards Leon Mem Test:
System 7 boards Leon Mem Test:
The "Old" Leon Memory Test (prior to 11/01/03).
To activate the memory test, keep the tester LED connected to +5 volts and U1 pin 15, and while the CPU mounted LED(s) are blinking on and off, press the SW1 diagnostic switch on the CPU board. The CPU board mounted LEDs (or the 7-segment LED on system7) will stay on or off for a second (depending on what state they were in when the SW1 button was pressed). The tester LED on U1 pin 15 will now indicate the memory test results:
As a test, if IC13, IC19, IC16 are socketed, remove these chips one at a time and run Leon's memory test. This will give some idea of what to expect if any of these are bad. I find personally that if the tester LED gives a result *not* listed above (like the Tester LED flashes once and goes off!), than the problem is usually the IC19 (5101) RAM.
Now that the CPU board is working with Leon's test EPROM, it's time to install the driver board and diagnose it. Remember, the driver board is really just an extension of the CPU board. If the driver board does not work, it can lock up the CPU board, and prevent everything from working.
With the CPU and driver boards connected together, Leon's test EPROM installed, and the external +5 volts and 12 volt power supply turned on, the LEDs should again flash in unison about once per second (just as they did when the driver board was not connected). Also the flipper relay mounted on the driver board should click on and off (in some cases it may not, if the relay is slow to energize). If the relay does not click, this may be an indication that the "blanking" signal from the CPU is either missing or is too short in duration for the relay to energize. If the relay is not clicking on the driver board, this does not necessarily mean there is a problem with the CPU board (especially on System3 and System4 CPU boards, which seem to not always "click" the relay with Leon's test ROM). During normal game operation, the blanking signal is always on (high). Once the boards are installed in the game and the solenoids will not energize, the blanking circuit is the first place that should be examined. Leon's test chip also alternates high and low the Blanking signal on the CPU board, but the pulse length may not be long enough for the relay to "click". The blank though can be easily seen on pin 37 (fourth pin from the left) of the inter-connector using the tester LED.
* NOTE: When testing the IC11 pins 2-9 on the driver board (switch matrix), a slight modification is needed to the driver board. On driver board connector 2J3, short to ground *all* these connector pins when testing IC11 pins 2-9 (PIA outputs PA0 to PA7). If this is not done, IC11 pins 2-9 will not alternate on and off.
** Leon's chip also tests pins 19 and 39 on the PIAs. These are the CA2 and CB2 ports. Each 6821 has these two "special" ports (in addition to the eight ports at PA0-PA7/PB0-PB7), which are used mostly for the Special Solenoids. If CA2 or CB2 is labeled as a "STx" port on the schematics, that means it controls a Special solenoid when the game is in diagnostics, and these may not alternate on and off (as the PA/PB ports do). Keep that in mind.
If any pin 2-17 are not alternating high then low, then the PIA is bad. Remove the bad PIA chip, install a socket and a new PIA 6821 chip. Also check the interconnector pin 37 (blanking), as this should be high (LED on).
CPU board Locked Up with Driver Board Installed and Leon's Test Chip.
The most common PIA to lock up the CPU is driver board IC11, the switch matrix PIA. Go ahead and desolder this chip, install a socket and a new 6821 chip. The other two PIAs (solenoids and lamp matrix) can also fail, but they do not tend to lock up the CPU board like a failed switch matrix IC11 chip. If the CPU board is still locked up after replacing IC11, replace the driver board IC5 PIA (solenods) next. Still locked up, finally replace the driver board IC10 PIA (lamp matrix).
In real life, the driver board's IC5 solenoid PIA may fail the most of the PIAs, due to locked on coils from shorted driver transistors. These shorted driver transistors can take out the 7408 chip which drive them, and the IC5 solenoid PIA which drives the 7408.
But the driver board IC11 switch matrix PIA is a close second in failure. The driver board's switch matrix IC11 PIA, like the solenoid PIA, only has a single TTL chip in front of it for protection. So when someone shorts a solenoid or lamp voltage across the switch wiring under the playfield, it usually takes out the 7406 or 4049 chips and the IC11 switch matrix PIA.
The driver board lamp matrix PIA rarely seems to fail, in comparison to the switch matrix and solenoid PIAs.
Most people will be asking, "what is this Williams 'Blanking' Signal I hear so much about?" The blanking signal is a flag between the CPU and driver board that says, "Hey, the driver board PIAs chips are OK, the CPU ROM chips are good, we're booted and running, all is A-OK". So once the CPU ROM program thinks everything is good, it sets the blanking signal high. This in turn allows the rest of the game to "come to life". If the blanking signal never goes high, the solenoid, CPU control lamps, and/or the score displays won't work. The game will seem like it's trying to boot up and function, but the blanking signal keeps the game from coming to life at the last second. This is a protection device to prevent the game from destroying itself if the CPU thinks there is a problem.
The reason the Blanking signal gets so much (bad) press, is if the game is not working, the Blanking gets blamed (though in most cases, no blanking signal is the symptom, not the cause of the problems). So again, it should be stated right up front that most "blanking signal problems" are not related to the blanking circuit itself! If the blanking signal never goes "high", usually the problem is bad chip sockets (Scanbe), bad PIAs, or bad 40 pin interconnector. But if all the tests have checked out Ok with Leon's test chip, and the blanking signal is still low, there is good reason to suspect the blanking circuit itself.
As Mark says, "blanking will always be zero (low) unless the board has successfully booted with the game ROMs". The purpose of the blanking signal is to shut down the displays, solenoids and lamps in case of a software or hardware problem. This prevents possible damage to the game if there is a problem.
The symptoms of a low blanking signal are dead score displays and no CPU controlled lamps (which also happens to be the symptoms of almost every other MPU board problem!) If the board seems to be booting with the game ROMs and it passes the self test (both LEDs flash and then go off), check the Blanking signal at pin 37 of the interconnector; It should be 4 to 5 volts.
As R.Cole describes the blanking is a hardware generated signal where all of the PIA outputs on the driver board are ANDed together (that is, PIAx must be high AND PIAy must be high, etc, to get a final high blanking signal). When the blanking signal is low, all of the controls to the transistors are low and hence there are no switched lights and no solenoids (this is a protection trigger so coils/lights don't burn up if there a problem with a PIA). With the blanking system low, the displays do not turn on either. When the CPU board's blanking circuit sees driver board PIAs ANDed together, the PIA outputs are enabled and the blanking signal is high, allowing the solenoids and lamp matrix to work.
Since the blanking signal is ANDed with the output of the driver board PIAs, the driver transistors won't ground (energize) a coil unless a high signal comes from both the PIA and the blanking circuit. That is, both the blanking signal and the PIA output must be high to fire a coil. So how can the blanking signal cause all the coils or lamps to lock-on at power on? A high blanking signal will not cause the solenoids or lamps to lock-on, as this is normal in-game operation. However if the blanking signal is lost from the CPU to driver board through a broken 40 pin inter-connector, this will cause the solenoids and/or lamps to latch 'on'. Because now the blanking input to the AND gates will be left floating (undefined) with no clear logic level. You can easily correct this by making sure that 40 pin interconnector has been replaced. In addition, all PIAs come out of reset at power-on with their ports configured as inputs, until reprogrammed by the CPU. If the CPU board does not run because it's faulty, and the blanking signal is missing on the driver board, you have a mix that can cause the AND gates to possibly switch to an 'on' state (documented by Clive). This can cause all the game's coils and lamps to lock on.
Blanking and Leon's Test ROM.
Also keep in mind if testing the boards using Leon's test chip, the blanking signal may or may not be present. This is due to the fact that the test chip pulses port PA2 on IC18 pin4 only about twice a second, which may or may not be fast enough to reset the timer circuit. Because of this, disregard the blanking signal with Leon's test chip installed. Unfortunately the Blanking signal can only be tested once the boardset is running properly with the game ROMs installed.
That said though, I have found the Leon test chip helpful as it does pulse once a second the blanking signal from PIA ic18 pin4. This goes to ic7 pin 5, which should also be pulsing once a second. Then this 7404 inverts the signal and puts it out to pin6 (which should be pulsing once a second, but in opposite order of pin5 and with a very slightly longer high tone.) Then the signal goes to the top leg of cap C31 (upper left of CPU board.) The lower leg of cap c31 and middle leg of Q5 should be about 3.2 volts. The lower leg of Q5 should be moving once a second between 3.7 and 3.5 volts. The upper leg of Q5 should show no voltage (ground). The TP4 (blanking) will pulse once a second between 0 and 1 volt (hence Leon's chip doesn't give a good blanking signal indicator as 1 volt isn't exactly a high signal.)
Likely Blanking Signal Problem Parts.
Testing for the Blanking Signal.
To make sure the problem is not the interconnector, check the blanking signal on the CPU board at connector 1J3 pin 4. If the blanking signal is Ok at 1J3 pin 4 but not on the driver board's interconnector pin 37, the interconnector is bad. If the blanking signal is missing at 1J3 pin 4 also, the interconnector is probably Ok, but the parts generating the blanking signal are bad.
If the problem is the blanking circuit itself (all the rest of of the CPU/Driver board is really Ok), with the game ROMs installed the CPU LEDs will act "normally". That is, at power on a system3-system6 game will flash both LEDs on then off. On system7, the "0" will flash and turn off. But the score displays and CPU lamps won't come on. If the self-test switch is then pressed on the CPU board, the CPU memory test will be run (system3-6, both LEDs should flash twice if everything tests correctly). If all this checks out (and all fuses for the score displays and CPU lamps are good), there is a good chance everything is Ok except for the Blanking circuit itself.
A Cheat to Determine if the Problem is the Blanking Circuit.
Checking the Blanking Circuit Components.
First check capacitor C32 on system3-6 CPU boards or C84 on system7 (.047 mfd, 50 volts). The picture above shows an oscilliscope connected to each leg of capacitor C32. The picture on the left is the signal going out of the left lead of capacitor C32. If this signal is missing then the blanking signal will not be high on interconnector pin 37 or CPU connector 1J3 pin 4. The picture on the right shows the signal going into the the right leg of capacitor C32 (or C84 on system7). If this input signal is missing then the problem is most likely chip IC7 (7404, all system3-7 CPU boards).
Now back up and start at PIA IC18 port PA2 pin4. There should be about 2.5 volts DC of waveform there. This goes to IC7 inverter 7404 pin5, and out of pin6. The signal should still be a good 2.5 volt waveform. I have seen a bad PIA where the signal looked good coming into the 7404, but was flat coming out of the 7404. This would make you think the 7404 was the problem, but in fact it was the PIA.
Now the signal goes to the timer chip. In system3 and system4 boards, the 556 chip is used to generate the Blanking and IRQ signals. On System 6 boards the 556 is only used for blanking. On system 7 the 555 chip is also only used for the blanking signal.
Next check transistor Q5 (or Q1 on system7), a 2N4403, which can be tested with a DMM set to the diode function. If both transistor Q5 (or Q1 on sys7) and cap C32 (or C84 on sys7) test good, as does chip IC7, next suspect the timing chip IC23 (a 556 chip on system3-6, or a 555 chip on system7).
I have found the Leon test chip somewhat helpful with blanking as it does pulse once a second the blanking signal from PIA ic18 pin4. This goes to ic7 pin 5, which should also be pulsing once a second. Then this 7404 inverts the signal and puts it out to pin6 (which should be pulsing once a second, but in opposite order of pin5 and with a very slightly longer high tone.) Then the signal goes to the top leg of cap C31 (upper left of CPU board.) The lower leg of cap c31 and middle leg of Q5 should be about 3.2 volts. The lower leg of Q5 should be moving once a second between 3.7 and 3.5 volts. The upper leg of Q5 should show no voltage (ground). The TP4 (blanking) will pulse once a second between 0 and 1 volt (hence Leon's chip doesn't give a good blanking signal indicator as 1 volt isn't exactly a high signal.)
As R.Cole describes, the IC23 timer in the blanking circuit is set up as a resetable one-shot. The signal from one of the PIAs resets the timer periodically. This is a watchdog type of circuit. If the CPU locks up and the IC23 timer chip does not get reset, then the blanking signal goes low and the switched lights and the solenoids are disabled. There is one transistor in the blanking circuit (Q5 or Q1 on system7) and if shorted, it can take out a capacitor C32 (C84 on sys7) in the process.
This is a neat trick that Jerry came up with. He adds a blanking signal LED to the driver board on his test fixture. This way the blanking signal can be seen at a quick glance. Certainly this isn't needed on every driver board, but if you have one working "test" driver board, this is a neat addition. Personally, I add this LED to every driver board (but hey, I like LEDs and I'm easily amused).
To add the LED, just solder the interconnector's pin 37 to the round side lead of an LED. Then connect the flat side lead of the LED to a 150 ohm 1/4 watt resistor. Finally connect the other side of the resistor to ground (the big fat trace going around the edge of the driver board). Now when the CPU board is powered on, the LED will be off for just a moment, and then turn on and stay on, indicating a good blanking signal is getting to the driver board from the CPU.
Now that driver board *and* CPU board are seemingly working together, it's time to try some other driver board tests using Leon's test chip. For all these tests, the "tester LED" is required!
Note since the PIA chips are already tested, the tests below try and check the system from the PIA to the driver board connector. In many situations, it is just easier to test the transistors and support chips without power, just using a DMM. This is described in Lamp matrix, switch matrix, and Non-work/Locked on coils sections. But to be complete, the tests below can be used too.
Switch Matrix "Drive" (Column) Test (Connector 2J2).
To verify which input chip IC17 or IC18 is bad, check the input pins of these chips. Put the resistor lead of the tester LED on IC17 and IC18 pins 1,5,9,13. These pins feed from the PIA (which was tested earlier). Now put the resistor lead of the tester LED on IC17 and IC18 pins 2,6,8,12. If these output pins are not alternating but the input pins are alternating, the chip in question is bad.
Leon Testing Switch Matrix "Inputs" (Row) Test (2J3).
Lamp Matrix Strobe (Column) Test (Connector 2J5).
In addition, the connectors at both 2J5 and 2J7 need to be attached from the game. If testing "on the bench", an alternative method can be used (see below).
Now connect the tester LED's non-resistor lead to +5 volts. Using the resistor lead of the tester LED, touch each pin of driver board connector 2J5. The tester LED should alternate on and off, in unison with the blinking LEDs on the CPU board.
If the CPU/driver board combo is on a bench with no access to the playfield connectors 2J5 and 2J7, another method must be used. With the tester LED's non-resistor end connected to +5 volts, touch the tester LED's resistor end to the left most leg of each transistor Q62, Q64, Q66, Q68, Q70, Q72, Q74 and Q76 (the small transistors along the right edge of the driver board). The tester LED should alternate on and off, in unison with the blinking LEDs on the CPU board (the tester LED will not work directly on connector 2J5 without the playfield connectors 2J5/2J7).
If the alternating signal is missing, yet all the IC10 lamp PIA signals are present, check the inputs of IC13 or IC14 (7408) on the driver board (pins 1,2,4,5,9,10,12,13 of IC13 and IC14). If there is no input signal, there is a bad TIP42 (Q63,Q65,Q67,Q69, Q71,Q73,Q75,Q77) driver transistor or 2N6472 (Q62,64,66,68, 70,72,74,76) pre-driver transistor feeding the chip. Then check the output signals of IC13 and IC14 (pins 3,6,8,11). If the input signal is turning on and off, but there is no output signal, the chip is bad. Note the output signal from the chip may be very short.
Lamp Matrix Row Test (Connector 2J7).
In addition, this test also requires a ground connection to any pin of driver board connector 2J6 (if the boards are installed in the game, just have the game connector attached at 2J6).
Once power and ground are applied to the lamp matrix, now connect the tester LED's non-resistor lead to +5 volts. Using the resistor lead of the tester LED, probe on each pin of driver board connector 2J7. The tester LED should alternate on and off, in unison with the blinking LEDs on the CPU board.
If the alternating signal is missing on any connector 2J7 pin, yet all the IC10 PIA signals are present, check the outputs of IC19 or IC12 (7406) on the driver board (pins 2,4,6,8,10,12 of IC19 and pins 2,4 of IC12). If there is no output signal, the chip is bad. If the output is good, there is a bad 2N5060, 2N6427 or 2N6122 transistor.
Solenoid Driver Test (Connectors 2J9,2J11).
If the alternating signal is missing on any connector pin of 2J9 or 2J11, yet all the IC5 PIA signals are present, check the output of chips IC1,IC2,IC3,IC4 (7408 pins 1,2,4,5,9,10,12,13). if any are missing, the chip as failed. If all alternating signal is present, there is a failed predriver 2N4401 (Q14,Q16,Q18,Q20,Q22, Q24,Q26,Q28,Q30,Q32, Q34,Q36,Q38,Q40,Q42,Q44) or driver TIP120/TIP102 transistor (Q15,Q17,Q19,Q21,Q23, Q25,Q27,Q29,Q31,Q33,Q35, Q37,Q39,Q41,Q43,Q45).
Special Solenoids Trigger Test (Connector 2J12).
Also selected connector 2J13 (switch inputs) pins will need to be grounded for this test. Then connect the tester LED's non-resistor lead to +5 volts. Using the resistor lead of the tester LED, touch connector 2J12 pins specified below (note that 2J12 pin 2 is not tested, as this is the flipper coil ground return).
The tester LED should flash on and off for each 2J12 pin listed above. If the tester LED is locked on or off, the ground connection to connector 2J13 can be moved backwards through the circuit to find the faulty component (the tester LED should *not* be moved). For example:
If the tester LED now flashes when ground is moved from 2J13 to the appropriate IC6/IC7 pin, then IC6 or IC7 is bad. If the tester LED is still not flashing, move ground again through the circuit:
Again if the tester LED now flashes when ground is moved from IC6/IC7 to the appropriate IC8/IC9 pin, then IC8 or IC9 is bad. If the tester LED is still not flashing, a 2N4401 pre-driver (Q1,Q3,Q5,Q7,Q9,Q11) or TIP120/102 driver transistor (Q2,Q4,Q6,Q8,Q10,Q12) has failed.
Summary of Driver Board Tests.
The flipper ROMs also contain some built-in factory diagnostics. For this to work, the standard game ROM and Flipper ROMs must be installed, and the driver board connected to the CPU board. System3 to System6 CPU boards have two red LEDs (Light Emitting Diodes) which provide some limited diagnostic information. If the CPU board successfully boots, both LEDs will blink together once, and then turn off. If one of both LEDs locks on, this is an indication of a problem. But the main problem with this diagnostic system is this: the game must have booted correctly, and be in attract mode, for any LED indication to be valid!
Now how much sense does that make? If the CPU board boots, and the game goes into game over (attract) mode, chances are pretty good that the CPU board is working! (This is unlike Bally's 1977 to 1985 system, where the LED flashes as the game boots, testing each major CPU component in the process, and giving a big clue as to what it thinks is wrong).
What most people miss is this: if either or both LEDs (or the 7-segment LED on system7) are locked on at power-up, the CPU board has not booted properly. Basically it's the software contained in the EPROMs that turns off the LEDs. If the LEDs never turn off, the software is probably not executing. There there is a problem, and it must be fixed before the LEDs can be trusted for any diagnostic help. And if the game comes up in "audit" mode, and the CPU batteries are good, the IC19 CMOS 5101 RAM is bad. So why do we need the Williams' diagnostics?
If there is a problem with the Flipper ROMs or game ROM, at power-up both LEDs will flicker, then both LEDs will come back on and stay on. Compare this to powering-on the CPU board, and both LEDs come on and stay on with no flicker (this indicates a locked-up CPU board).
On system3 to system6 CPU boards, when the board starts correctly, the LEDs flash once and then go out. Now push the CPU board's diagnostic switch SW1 (the lower button) once. IMPORTANT: on System6/7 games, the coin door must be open (memory protect switch open). If all diagnostics pass, both LEDs will flash briefly *twice*, and turn off. The game will not return to attract mode.
Turn the game off, and repeat the test three or four times. If the same result is received every time, the results of the test can be considered "valid". If different results are seen, NONE of the results can be trusted!
If different results are seen between multiple tests, the first thing to suspect is chip IC19 (5101 CMOS RAM), and then chips IC13/IC16 (6810 or 2114 RAM). If any of these are in sockets, suspect the socket too.
What the diagnostic software is trying to do is this: The Flipper ROM software reads a few bits from IC20 (the Flipper ROM), and then attempts to write that to IC13/IC16 (6810 or 2114 RAM) and IC19 (5101 RAM). If the results don't equal what's in the Flipper ROM, then the LED locks on. 99.9% of the time the problem is IC19 (the 5101). The two static 6810 or 2114 RAMs (IC13/IC16) are rarely bad. While flipper ROM IC20 could be bad, the game usually won't boot for the user to even run the diagnostic test if thats the case.
Once the CPU/driver board is booted and the game is in attract mode, press the CPU board's SW1 diagnostic switch (the lower switch). Remember on System6 games, the coin door needs to be open. If the SW1 diagnostic switch causes both LEDs to flash twice and go out, the CPU board is probably OK. It might still have display problems, if that happens check CPU board PIA IC18 (score display PIA). Most other components are OK if two flashes are seen. After the two flashes, the game will need to be turned off and on to exit the test (and go back to attract mode).
If either or both LEDs remain lit, the test program has found a problem:
Try the test three or four times. If the same result is received every time, the results of the test can be considered "valid". If different results are seen, NONE of the results can be trusted! Again, if different results are seen between multiple tests, the first thing to suspect are chip IC19 (5101 CMOS RAM), and chips IC13/IC16 (6810 RAM). If any of these are in sockets, suspect the socket too.
The System7 diagnostic tests and codes aren't quite as dumb and unreliable as the above mentioned System3-6 codes. But all the same rules apply here. That is, the CPU board must boot correctly to trust the diagnostic codes. IMPORTANT: the coin door *must* be open to run the diagnostic test! (That is, the memory protection switch must be open.)
With the coin door open, switch SW1 (the lower button on the CPU board) can be pressed once to run the diagnostic test. The LED display should show "zero" for a second. If everything is Ok, the display will go blank for another second, and the game will return to attract mode. If there is a problem, the error code will display the error number in the LED, and the number will stay displayed. The game will *not* go to attract mode.
The System7 test diagnostic LED values are listed below*:
Again, try the test three or four times. If the same result is received every time, the results of the test can be considered "valid". If different results are seen, NONE of the results can be trusted! Again, if different results are seen between multiple tests, the first thing to suspect are chip IC19 (5101 CMOS RAM), and chips IC13/IC16 (2114 RAM). If any of these are in sockets, suspect the socket too.
* NOTE: If using System3 to System6 firmware EPROMs in a System7 CPU board, the LED diagnostic display will not function as described above! System3 to System6 software does not support the seven segment LED that is used on the System7 CPU board. In this case, if CPU board diagnostic switch SW1 is pressed, the upper segments of the LED will flash a "u" twice if the test passes (the "u" is essentially the equivalent of both LEDs on a system3-6 CPU board flashing). The game will not return to attract mode. Not much can be diagnosed here, unless System7 EPROMs are installed back into the system7 CPU board, and the test rerun. It's not a bad idea to install the two LEDs and two resistors back into the system7 CPU board, as described above.
Some Real Life System7 Test Numbers.
If running system7 software, what the System7 diagnostic software is trying to do is almost the same as the System3 to System6 software. But since there's a seven segment LED, the output report is more specific to the exact problem chip suspected. The Flipper ROM software reads a few bits from IC20 (the Flipper ROM), and then attempts to write that to IC13/IC16 (2114 RAM) and IC19 (5101 RAM). If the results don't equal what's in the Flipper ROM, then the LED locks on. 99.9% of the time the problem is IC19 (the 5101). The two static 2114 RAMs (IC13/IC16) are rarely bad. While flipper ROM IC20 could be bad, the game usually won't boot for the user to even run the diagnostic test if that's the case.
Other Notes: System7 codes 3, 4, 6 and 7: These error codes usually indicate a bad ROM chip. As described in the ROM chip section and socket sections, the original black ROM chips should have been replaced with new EPROMs. If one of these ROM chips is bad, replacing all of the CPU ROMs chips too. If both LEDs remains on after flashing (System7 codes 8 and 9), often the memory protect circuit could also be bad (this circuit prevents adjustments from being changed unless the coin door is open). But chances are really good the problem is really the IC19 RAM 5101 is bad.
Using a Williams test EPROM can help simplify start up problems, and maybe help the CPU board boot. But even with this chip, the LED fault indications are again not valid unless the CPU board boots first. The bottom line is don't use this Williams test EPROM with a boot-up problem, use Leon's test EPROM instead. But the Williams test EPROM and instructions can be downloaded by clicking here.
Andre Boot has also created a test ROM for system3 to system7 boardsets. His works differently than Leons, and is a bit more "automatic". You can download his test ROM, disassembly 6802 code, and instructions here.
Andre's test ROM causes the LEDS on the MPU to flash five times for a stanalone MPU board, and nine times if the driverboard is connected. Every flash is an IC test. Here are the LED flash codes:
Andre Boot Test ROM Installation Instructions.
With Driver board connected it should flash nine times (ten times for system7). With driver board disconnected is should flash five times.
All Done with the CPU/Driver Board Tests!
It should be noted that just because everything checked out with Leon's test EPROM and Williams' built-in tests, does not 100% guarentee the CPU/driver boards will work in the game! It's a pretty good chance they will, but these tests are not perfect, and can overlook some problems. Just keep that in mind.
If the game boots and works, turn the power off and add fuse F3 (lamp matrix) first. Power back on and see if the game's attract mode lamps are working. If successful, power off and add fuse F2 (solenoids). Power back on and hopefully no coils lock on. If any coil(s) do lock on, check the driver board for shorted solenoid driver transistors.
* Return to the Pin Fix-It Index
* Go to Part One System3-7 Repair Guide
* Go to Part Three System3-7 Repair Guide