1) Voltages
It's generally a good idea to start with this, to make sure you're not chasing a phantom problem. You may need to do this over time to see if the voltages are fluctuating, or dropping over time. I expect your voltages to be ok, otherwise you would probably see more weird stuff (like Random resets, etc..).
2) Connectors
You could have a connector that isn't making very good contact. You could start by disconnecting all the connectors and reconnect them. If the problem goes away, chances are you have a connector that wasn't making very good contact and it should be replaced.
3) Wiring
Make sure you don't have any lose wires. If the harness is hacked up, or someones "repaired" it, maybe it's making an intermittent connection that causes the game to coin up.
If all those check out, it could be a PCB issue, in which case you'll need to break out the Schematics and Logic probe...
I had the same problem with Spy Hunter. Actually, I've had a million problems with Spy Hunter. The coin switch was bad. Every time someone walked by the thing it'd give a credit and sometimes randomly it'd do it it's self.
I had the same problem with Spy Hunter. Actually, I've had a million problems with Spy Hunter. The coin switch was bad. Every time someone walked by the thing it'd give a credit and sometimes randomly it'd do it it's self.
I agree with the previous posts, it is probably the coin switch or wire. Look close at the wires in the coin door and any that might get pinched when the coin door closes. One of my games likes to pinch wires when you close the coin door.