Leon Borre WMS System 7 Repair
Repair cpu boards Williams type 7.
Introduction.
At first I used on this board the tests for type 3/6, but there are some important differences. At first there is an extra PIA at the CPU board, and also the test EPROM can not just be plugged in (2716 type) because the type 7 board works with a 2532 type game rom. Furthermore there are several jumpers which are different (according to the type of machine in witch the CPU was used). And the memory chips are other type , covering almost the same addressing , but the two memory chips take each half of the data bits.. All these differences made me change these tests into a separate part, otherwise it would become too complex. Fortunately type 7 boards use the same driver so this at least stays the same.
Type 7 CPU boards has space for 6 ROMs (EPROMs).. three memory chips and two PIA's. This test will check the PIA outputs and three memory chips. This will imply that the CPU chip is also ok, as well as the selection circuits. If the tests are ok then it's virtually guaranteed your pinball machine will start.
This is the Williams type 7 CPU board with battery holder at the bottom left.
As usual I use a test EPROM which allows me to test all parts I just mentioned. Let's start with the setup.
Test EPROM:
The test EPROM is a type 2532, which you can downloaded here .......... 
( version 3 ) This EPROM fits without changes into the socket of IC17. Take care that jumper W11 is connected. If it's on W12 then you will have to move it.. ATTENTION since October 2003 there is a the new version of the memory-test . The test is more complete and there is an indication which memory IC is tested visible on the "on-board" display . ( see memory test)
Start.
The only power we need to use the board is 5 volts. 5 volts needs to be brought to pin 4, and ground to pin 3, of connector 1J2. Also a temporary connection between C23 (bottom) and R3 (bottom) is necessary to start.
The test EPROM, a 2532 type EPROM you can plug in IC17.
To check how the test program works, we have to hook the control led to pin 15 of the CPU chip (IC1) and the other side of this control led to 5 volt.
Again how the control led is made: a led with a resistance of 1000 ohm in series with 2 little hooks. The 5volt, (bottom of condenser C23 left at the CPU board, and the green hook at pin 15 of the CPU chip IC1. To know it's connected well, at first use, put the green hook to ground, the led should light, if not then switch the wires at the led..
Usage:
Now you can start the tests. So what does the test program do ? It switches outputs PA 0 to PA 7 and PB 0 to PB 7 of PIA chips IC18 and IC 36 on the CPU board, and of PIA chips IC11, IC10 and IC5 on the driver board to high and then again to low. This all the time in rhythm. The program is non-blocking, which means it will continue, even if one if the outputs is broken and does not follow. This way with a DMM, logic probe, or even a regular led (in series with a 2k ohm resistor) you can measure all outputs and see if everything works. The same test -control you have with the 2 LEDs on the CPU boards, these are connected to CA2 of IC18 on the CPU board, if this PIA (IC18) works, these LEDs will also light in rhythm. The display will also show a blinking 0 . The test really only checks the CPU 6808 (IC1) and the 6820/21 chips and is not dependent of the memory-chips (IC13 IC16 IC19) and certainly not dependent of the program EPROMs (IC26 IC22 IC21 IC20 IC17 or IC14). The selection chip IC15 and buffers of the address and data lines are also checked.
I just want to add that the PIA's are these chips which drive all pinball-functionalities, like coils, lights, displays, ...
At the same time this means when the program does not work well, only a few components can be responsible for this.
Manual
The whole setup. You see the control led connected to pin 15 of IC1 and 5 volt (C23 bottom) The 5 volt is also connected to R3 (bottom) using a temporary jumper.
If the control led lights in rhythm you're lucky and you can check the outputs of IC18 and IC36. If it doesn't light, then first try a new 6808. Still no luck ? Try a manual reset by connecting pin 40 of the 6808 to ground. Then check if there is permanent 4,5 volt present on this pin 40. It not, look for the source of your problem in the reset-circuit. For type 7 the reset circuit is made by transistors Q 1/2/3/4/6/7/8 and 9. The output PA7 of IC36 will not move, as it's connected by W25 to ground...
The next step when it doesn't work is check the signals on the 6808 (IC1), the clock-signal on IC1 pin 38 and 39. (clock signal is about 1,5 volt). Next thing to check is the signal at 6808 (IC1) pin 2 and 3 should be 5 volt. Finally check pin 5 which should have about 3 volt. Also check if the buffers of the address and data lines work, these are chips IC4, 3 and 8 for the address lines and IC9 for the data lines. On the schematics you can clearly see the inputs and outputs, which are drawn opposite of each other. I.e. A0 is pin2 IN and pin 3 Out. A1 is pin14 in and pin 13 out, etc. The signal which goes in should be the same as the one which comes out ! If the 6808 has been replaced and is now ok, then one if these signals should be bad. Just trace it to it's source and you should find where it's missing.. A last possibility is that the selection of IC18/IC36 doesn't work, check if you get signals at the address lines of IC17, and selection signals on IC18/IC36 (pin 35, 36, 23, 24, 22 and 25). Now should all (or some) outputs of IC18 /IC36 go up and down. If there is somewhere an output on chip IC18 / IC36 which does not go up and down, then connect it to the one next it it. If this also falls away, then you have a short on that output, trace it first, if both outputs go up and down, then you can be sure the chip is broken. A last test is to put the program chips back into their sockets except for IC17. Their presence should not interfere with the working of the tests. If one if them does, it's bad. Conclusion: if all the outputs work then you can test your memory-chips.
SPECIAL REMARQUE:
If by a misfunction the selection of the memory chips IC13 and IC16 (tied together) stay low ( 0 volt) the test will not start...Because if the selection on pin 8 of these two chips is broken and the pin stays low the chips are selected and the memory data will corrupt the normal data on the data bus. So whenever the test don't start up always measure pin 8 of Chips IC13 and IC16 they MUST be 5 volts at start-up!!
If you also want to check the PIA's of the driver board then connect the driver board to the CPU board, put the test chip back into IC17 and power the board up. The LEDs on the CPU board will start to blink again.
Check if the outputs of the 3 PIA's go up and down. Remark: output of PIA IC11 , PA0 to PA7 are always forced low. You can solve this by connecting ALL pins of connector 2J3 to ground (7 pins, connect to ground) and then these outputs will also 'dance' like the others do.....
Once again, if there are PIA's which do not work completely, then check the selection of the PIA on its selection pins: 35, 36, 23, 24, 22, and check if pin 25 has 2,5 volt. If one of them is missing, then trace it to it's source, using the schematics, and a logic probe or o-scope. If only a few outputs don't work, again connect it to one next to it, if both don't work you have a short on the output, if they do then the PIA is broken...
Here you see the setup to test the driver board. Connected to the CPU, which has the test EPROM in IC17.
Connector 2J3 on the driver board is connected to ground with all its pins..
Conclusion:
Once you're sure the outputs of the PIA's work, you can use the pinball's own coil and lamp tests.....Or use the repair method for the driver board on my site, to test that board completely.
Memory test.
Once the PIA test is successful, you can test the memory chips, by pressing the button " diagnostics" once. This starts another part of my test program. Be careful, I once had a board on which the button did not work ! Then you can connect pin 6 of the CPU chip to ground (for a short time). Both LEDs on the CPU board will stop flashing (if they are on or off doesn't matter). (the display stops flashing to) Now check the control led connected to address line 6. This will stay off (timing) and then give you a few flashes. The first is for IC 13, the second for IC19 and the third for IC16. If all three appear then the test will come back on the regular PIA test and everything will start to flash in rhythm. If a selection or a memory chip is bad, none, one or two flashes will appear. None means IC13 is bad, one = IC19 bad, and two = IC16 bad. Important: a "flash" means that the led clearly lights and goes off again. Faint lighting does not count as a flash.
In version 3, the "on-board" display will show:
- 1 during test of memory chip IC13,
- 2 during the test of IC19, and
- 3 during test of IC16.
When the test of one of these IC chips fails, the corresponding test number will remain on the 7-segment display as the program continues to test that IC over and over.
Depending on the diagnosis it is best to just replace the memory chip. Also put in a socket so it's easier to change it in the future. If the test marks the same chip as bad, you'll have to trace the selection of that chip..
When a memory chip is bad, the test will continue to test that same memory chip, allowing you trace the chip select signals easy with a logic probe or DMM.
I hope this detailed explanation will help you and wish you a lot of success !!
Important remark.
If you have already my test EPROM of the Williams 3/6 cpu board then you can use it to test a type 7 cpu board, but you'll need to do a little modification. Read all about it on this page ..........
Addendum - User Remarks
Leon's System 7 test program and procedure have been verified to work perfectly. A few notes are in order.
Williams System 7 MPUs shipped with 2332 ROMs. A 2532 is pin compatible with the 2332 and can be used easily. If you can burn the test image into a 2532, you simply insert the test ROM into position IC17 (right column of ROMs, middle ROM). A 2732 can also be used, which requires one jumper move, one additional jumper, and one cut, as detailed below.
- W22 must be removed
- W23 must be in place
- Cut the fat trace leading to IC17, pin 21 right where it joins the pin. Your intent is to isolate ONLY pin 21 from the circuit
- Add a jumper from the side of W22 that is NOT connected to W23 to the now isolated pad at IC17, pin 21
Leon's memory test order is different from the stock Williams test. The 7 segment window shows...
- 1 - tests the low nybble at IC13 (a 2114)
- 2 - tests IC19 (a 5101)
- 3 - tests the high nybble at IC16 (a 2114)
A video showing Leon's test ROM working in a fully functional System 7 MPU can be found here.
An image of one user's System 7 test setup, using Leon's ROM, is shown at left. The top connectors on the MPU are connected to a display tester. Switch matrix test connectors are along the right side of the driver board. Lamp matrix test connectors are along the bottom of the driver board. Solenoid test connectors (bar style LEDs) are along the left side of the driver board and are powered by the jumper from the lower right corner of the driver board. A logic probe is connected to test points 9 (+5VDC) and 10 (Ground) on the MPU. A test switch is connected at the top of the MPU (just left of the display tester connectors) which allows easy entry into game diagnostics.