Good day.

I am finishing the restoration of a Stern Hot Hand pinball machine and have run into a weird problem. On power on, the Extra Ball out coil is repeatedly firing at about 8 fires per 10 seconds. If the credit button is hit, it drops to 5 fires per 10 seconds. I tested a different driver board with no difference. The wiring looks correct and the coil is testing as working.

Just wondering if anyone has an idea of what to test to troubleshoot this issue.

Thanks,
Justin

I did check the switch and it makes no difference opened or closed. I am wondering if maybe power on ground could cause the issue but that wouldn't trigger a fire. I suppose it is also possible the switch is bad but it shouldn't fire when the game isn't being player.