Williams System 6 MPU LED's Flash 2x Only

mantaramian

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Williams System 6 MPU

I am looking for some guidance on a three Williams System 6 MPU boards.

The symptoms are the following on all three MPU's;

Both LED's flash twice. That is it!!!

I have read all that I could online. I took the fist set of advice and replaced the original sockets (Scanbe sockets)

The EPROM's are good. (I have an EPROM programmer and verified the ROMs are good for three of the games. (Blackout, Firepower and Time Warp) all good checksums.

There is no battery corrosion on any of the MPU boards.

My soldering and de-soldering skills are above average (use to solder circuit boards during high school) I was given a PACE de-soldering station in the 90's.

However my skills on the logic side of these boards need a lot of improvement……

I have verified the 5101 is good, (purchased a couple from Marco Specialties)

I have a logic probe, but not sure what I am looking for….

I downloaded Leon's Test Chip, and get the repetave flashes per the instruction, so from what I have read the boards are working, but only to a certain level…..

Is there any advice to my problems……

Oh yea, here are some pictures of one the board's I am refering to.... All three arein the same condition....

Thanks,
Mike
 

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You may be confusing these boards with the Bally boards, which go through a sequence of flashes as part of the boot process; unlike those boards, the LED's on these boards are borderline useless.

If everything is checking out with Leon's installed, and you've confirmed the game ROM's all check out, it's time to install the boards in a game and verify whether they come up - assuming you've got a known-good driver board and power supply board in the game.
 
I downloaded Leon's Test Chip, and get the repetave flashes per the instruction, so from what I have read the boards are working, but only to a certain level…..


Actually no, that doesn't mean the boards are working, only that the CPU is able to run the test code. Running the test code requires minimal hardware support, at this point all you can know for sure is that the CPU runs, the clock, reset, address, data, and a few other things, are working enough and probably ok.

Did you run the memory test routine?

Do you still get the LEDs flashing when the driver board is connected?

With the test rom, you really need to step thru the test procedure from first step to last, most problems will be uncovered if you follow Leon's guide for using the test rom.

If everything seems to run good, memory test passes, but the board doesn't work in the game, then one of the PIA IC's is probably bad. There is no way for test code to fully test the PIA's directly on it's own, however Leon's code does run a PIA test that toggles the PIA output states so you can check the outputs with a simple "LED tester". Testing the PIA's pretty well explained in his repair guide and should help you get through it.
 
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