Solved Game works on bench but not in cab

[big10p]

I think this Do! Run Run board hates me, or the cab it's in is possessed. As stated, the game works fine on the bench using a supergun, but in the cab I'm getting garbled sound and graphics with a "Bad communication!!!" error message. The board was working ok in the cab previously.

I've checked the voltages and they are solid.

Any ideas other than holy water?

 

[GadgetFreak]

Can you try disconnecting the audio pins from the connector, both positive and ground. I think from memory the communication error occurs with sound cpu issues.
It might be that you have a grounding issue in the cab.

 

[big10p]

Can you try disconnecting the audio pins from the connector, both positive and ground. I think from memory the communication error occurs with sound cpu issues.
It might be that you have a grounding issue in the cab.

I'll try that. I have been playing around with the cab wiring recently, so I'm sure you're on the right track. Thanks.

 

[GadgetFreak]

Another quick thought is that Universal boards commonly had some hacks to do with the coin counters, you could try disconnecting them as well

 

[big10p]

Another quick thought is that Universal boards commonly had some hacks to do with the coin counters, you could try disconnecting them as well

Yes, there's a pull-up resistor on the coin switch pin, as Universal boards use active low for coin-up, it seems. It was working in the cab before with this, and works on supergun, so not sure what's going on yet. Not had time to check the wiring yet, but will report back. Thanks.

 

[big10p]

Ok, I tried disconnecting the audio wires but was still getting the issue. I double checked all ground connections. Took resistance readings from all the edge connections and compared them to the ones when plugged into the supergun.

Something looked fishy about the power connections, but I'm not an expert. I was going to scope the +5v rail to get a more detailed look, despite always reading solid with a multimeter. Just decided to swap out the switcher instead, and that seems to have done the trick! Phew, what a pain this has been.

Cheers.