(Topic ID: 210461)

WPC95 will not boot with sound card ribbon cable connected. Solved.

By SteveNZ

6 years ago


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  • 15 posts
  • 6 Pinsiders participating
  • Latest reply 6 years ago by SteveNZ
  • Topic is favorited by 2 Pinsiders

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    #1 6 years ago

    The MPU on my Scared Stiff will not boot while the ribbon cable that is labeled io sound is connected.

    Would this be more likely to be a MPU or a A/V board problem. Clay's guide says to suspect the TTL chips near the top of the MPU but it seems more likely to me that it is a AV board problem.

    most of the time the A/V board boots with 1 bong. but on some occasions it has 2 bongs which suggests a ROM failure.

    any ideas where to start looking for the cause?

    #2 6 years ago

    Another clue. when the ribbon cable is plugged in the A/V board the led on the A/V board flashes 20 times then stops flashing and then starts flashing again repeating this pattern continually.

    with the ribbon cable unplugged the led on the A/V board flashes without any pauses.

    has anyone had experience with the MPU TTL chips going bad?

    #5 6 years ago

    cable double checked and a new cable installed and checked. it is easy to be a row off but in this case the cable is fine.

    #7 6 years ago

    Good thinking, I'll get the probe out and start checking.

    #10 6 years ago

    I checked (with a logic probe) all the address and data lines on the CPU, I checked on both sides of the buffer chips with the ribbon cable connected and not connected.

    Should I be checking all the address and data lines on the A/V board?

    It would be great to isolate if the problem is with the A/V board or the CPU, but I don't have any other games to borrow boards from. I do have a WhiteWater and I have a Pinsound board. Can I use the DMD driver board from the Whitewater and the Pinsound board to replace the A/V board? My thinking is that if this works then the problem is on the A/V board but if it doesn't then the problem is on the CPU.

    #12 6 years ago

    I had activity (pulses) on all the data and address lines.

    I'll do some more research on using a Pinsound board to replace the A/V board.

    #14 6 years ago
    Quoted from Turtle:

    My random thoughts:
    1) Any corrosion on the CPU board? Specifically around U5 (chip directly below the battery holder). According to the schematics the CPU reset line is tied to this chip. This is pin 33 on connector J202.
    2) Have you tried resetting the ROM chip on the A/V board?
    3) Have you check the voltage 5V and 12V on the A/V board at connector J606? Most likely okay since the CPU uses them too. But I recently had a pin with what I thought was an A/V problem but turned out to be a driver board issue.

    Not sure about corrosion, the batteries were moved off the board before I got it and there is no battery holder on the board. It's quite likely batteries leaked in the past so I will take a good look. Only thing though, is the CPU boots every time as long as the A/V board is not connected, could it still be the CPU reset line? wouldn't that stop the CPU booting at any time?

    Resetting the ROM chip? did you mean reseating? I haven't tried reseating these yet, I will give it a go.

    5v and 12v are both good.

    #15 6 years ago

    Thanks for all the help. It is now booting again.

    I figured out a couple of things. You can use a DMD board form an older WPC game in place of A/V board - no sound of course. You can add a Pinsound board to get the sound. For testing I just removed the AV Board and installed the older DMD board. Fortunately I had a splitter from Pinsound for one of the Molex plugs or it might have been a bit trickier.

    With the older DMD board connected the CPU board still didn't boot. So I was pretty sure the problem was with the CPU board and not the DMD board.

    So I removed the CPU board and took a good look at it, there was no corrosion damage. The wire for the remote battery holder was not nicely soldered, so in case it was shorting something I resoldered it. Tested the CPU still no boot with the AV board connected.

    I was considering removing the TTL chips and replacing them, then I though I'll just try reseating all the socketed chips on the CPU. Reseated the chips and tested the CPU and it boots.

    I've played a few games and it seems solid. If it happens again I'll reset the chips and test 1 at a time to see which chip is causing the problem and then replace that socket.

    Not sure why it would boot under these circumstances without the AV board and not boot with the AV board. Perhaps there was a pin only just making contact and the extra draw from the AV board tipped it into the non-working condition.

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