I am working on a friends TZ and it has switch errors on 73,75,76,81,83, and clock is broken (keeps running). I suspect the opto 10 board since all these switches are opto switches. I have already reseated all ribbon cables in the backbox, reseated all 12v connectors, reseated connectors on the opto 10 board as well as the ball trough proximity sensor. 1 thing to note is the opto boards at first did not have 12v (led's not lit up), but reseating connectors brought 12v back. Any troubleshooting suggestions or guides on this?

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I did not measure the voltage on the boards. Since the led's were out I assumed it could be a faulty connection, and since they lit up afterwards I didn't think it was necessary

Thanks for your reply. The info you provided is helpful. Yes these switch errors as well as clock, show up in test mode. Also there is an issue with the ball trough (coil keeps firing). The game is at a friends house 45 minutes away each way so of course trying to minimize troubleshooting while there.

Thanks again for your input, I was pretty much thinking the same thing. I just found it strange that so many switches that are not on the same column/row on the switch matrix. This particular TZ the owner removed some mods but I think there are leftover wires on the pf...gonna look at all that and see if there is a short somewhere. I did perform a test on the cpu where I jumpered pins one at a time from j207-j209 and it tested good.