I did a full restore on mine a couple years ago. It's been rock solid ever since.

If you can find Clays guide for system 80 games, it tells you how to stabilize it. It's well worth tracking down. The main things are the large capacitor in the cabinet, a few easy ground mods, and making sure your board connectors are good.

The mechanics look intimidating since things are packed so densely to accommodate the playfield window but it's really not that bad.

It's a great machine, well worth owning. Also pretty easy to sell later if you need to.

Does it boot and start a game if you remove the ball from extra ball kickout hole? Does it fire in solenoid test? I'd test coil resistance and go from there.

Oh I see. Mine had a similar "fix"... PVC pipe stuck in the kicker to the upper playfield. Tracked that down to be an out of spec resistor on the driver board.

I would disconnect connectors from the MPU and/or driver board and see if that gets it to boot. May help isolate what's failing. Then start diagnosing that circuit.

Did you do any of the common bulletproofing on it? They're notorious for ground issues, failed capacitor in the lower cab, and poor connections due to the edge connectors on those Rockwell boards. I think the best thing I did to mine was rebuild all connectors with with new Trifurcon pins.