The lower 5-bank drop target reset coil never fires, in test or in play. The coil has voltage on both sides, grounding its lug fires it, the MPU signal toggles, and jumpering the driver connector pins also fires it.

Drop bank reset coil dead everywhere: driver ground wire moved to the wrong J4 pin

Cause: At some point the driver's ground wire had been moved to J4 pin 14, where the schematic labels it, but the driver transistor for this coil actually grounds through pin 10.

Checks

• Check the driver transistor's ground path with a meter, not only the wire colours and the schematic label.
• Swap the coil's drive pin with another coil from the same group at the board connector and run the test again.

Fix

• Move the ground wire to the pin the transistor really uses (pin 10 here) and retest.

Systems

• Gottlieb System 80B

Games

• Rock

Related tips

• Use heavy wire for the optional driver board ground jumpers
• Ground mod step 5: direct ground wire to the driver board
• Optional ground mod steps 2 to 9: driver board ground jumpers
• Coils lock on and burn because of the Gottlieb ground fault
• Test the driver transistors while the board is out for the ground mod
• Test driver board outputs by grounding transistor tabs
• First power-up, step 5: add the driver board, then coil power
• Optional ground mod step 1: ground the 2N3055 cases on the driver board

Source: Pinball Repair help group!! (Facebook group)