(Topic ID: 213165)

WPC Switch Matrix - Verify My Troubleshooting Conclusion


By Allibaster

1 year ago



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  • 8 posts
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  • Latest reply 1 year ago by pinmike
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#1 1 year ago

This weekend, I was helping my dad with his Getaway. We replaced a bunch of bulbs, replaced some coil sleeves, then cleaned it up. When it was finished, we had a switch matrix issue. One whole column of switches would ground short the entire respective row when closed. This was only for one column. The matrix appeared normal when no switches where closed.

We spent about an hour isolating switches and closely examining for shorts or pinched wires. No luck. On the CPU board, we unplugged J209 (rows) and J207 (columns) and manually closed the switches with a jumper. Sure enough, it was still grounding the whole row for the switches in that one column.

So, it appears to be on the CPU board. As for repairs, I am planning on replacing U20.

Is this the next logical step? Are there any other electrical components that I should order in anticipation of repairing that could also be causing this issue?

Final question: Is there a way to bench test this? My dad and his game are 100 miles away. I have his CPU board. I do have a Fish Tales available. Can I install this board in there to verify, or would that cause issues?

Screen Shot 2018-03-26 at 10.05.05 AM (resized).png

#2 1 year ago

sounds right, I would also check to see what might of caused the short that took out u20.
disconnect both switch plugs at mpu and test to see if there's any voltage feeding into one of the wires.

#3 1 year ago
Quoted from wdennie:

sounds right, I would also check to see what might of caused the short that took out u20.
disconnect both switch plugs at mpu and test to see if there's any voltage feeding into one of the wires.

Thanks. I think we may have accidentally shorted the GI circuit to a switch contact while swapping out bulbs. Just a guess. Should've had the game off.

#4 1 year ago

You can test this in your Fishtales. Just move the PROM from the fishtales board to the Getaway board, and you're good to go. If this problem didn't exist before you changed the bulbs and such, it's very likely to be your u20. It's a classic chip to die when you accidentally short the switches with the lamps. Been there, done that.

#5 1 year ago

Was the game on while you were changing the bulbs?If yes then 95% chance you blew out u20 on the cpu.Like Cadillacmusic said it wouldn't hurt anything if you tried the board in your fishtails.

#6 1 year ago
Quoted from Allibaster:

Final question: Is there a way to bench test this? My dad and his game are 100 miles away. I have his CPU board. I do have a Fish Tales available. Can I install this board in there to verify, or would that cause issues?

Yes, you can bench test this; all you need is a power supply that produces +5V and +12V and a logic probe. You can also just connect your logic probe to U20-16 with the processor in the machine and see if providing low going pulses.

1 week later
#7 1 year ago

Just an update. The switch matrix IC U20 was the culprit. It tested out fine in my Fish Tales before giving it back to my dad. After he installed it, his opto switches all showed closed. He performed a factory reset, and everything worked normal again.

Thanks for the help and tips.

#8 1 year ago

Sounds great,Your welcome

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