I don't know the history of this Grand Prix except it's been in a warehouse for the past ten years. It's looks to be in pretty decent shape, but it's missing the tilt unit and the play counter.
Currently the playfield is out of the machine. I've cleaned the stepper units, and examined the switch contacts on the bottom board. I replaced the fuses with new ones and tried to power it up, but I didn't get very far.
The credit unit decreases a step, the motor runs for a moment, I get a big spark from the coin relay's 3rd switch, and the 15 amp fuse blows. That's it. The score reels don't attempt to reset. I've cleaned and gapped that switch a few times, but the machine is eating fuses like popcorn. I've got a circuit breaker on order, but it won't be here until Tuesday.
I've checked the coin relay's resistances (I checked all of the coils, actually), and it seems to check out.
Should I keep my focus on the sparking switch, or should I look somewhere else? I can't see any wires or solder contacts that are not supposed to be touching.
Any advice is greatly appreciated.