Quoted from spblat:Problem 2: with the playfield harness disconnected, 1J18-2 is shorted to ground. This is what comes back from the switch under the jet bumper. I think this means that if I replace Q73, I'll just blow out the replacement.
Are you saying the board connector 1J18 pin 2 is shorted to ground or is the wiring connector pin 2 shorted to ground? If the short is on the cpu board then replace ZR3, Q-72, Q-73 and the coil diode as a set. Retest for the short before connecting 1J18 on the cpu board.
If the short is on the wiring connector then make sure the switch contacts are set correctly and replace the cap on the switch. Then replace Q-72, Q-73 and the coil diode. Retest for the short and reconnect 1J18.
Kingston, OK
