Attention all of you Indiana Jones/WPC89 guru's. I am working on a gamefor a friend and here are the symptoms:

1) left pop bumper is staying engaged, obviously over heating the coil. Other pop bumpers and kickers on the circuit acting eradically.
2) with coil disconnected (wire clipped at pop bumper coil) blows fuse F104 after some time.

Things I've done:
Replaced melted coil. Found shorted Q58 and replaced. Replaced U4, which routes all signals from the data bus and decodes. Seemed to work for a few minutes then fully engaged again. Transistor is not shorted to ground. Wires are fine and not shorted to ground. Connector from MPU board is correct and the MPU is a new Rottendog board. Performs the same with the original board. I'm baffled. Any ideas?

#Indianajones

Thanks

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Yes. I replaced the set.