With the coin door closed and no game started, the auto-plunger (shooter) coil locks on and heats up. Unplugging its driver connector stops it, but the drive transistors and pre-driver all test good.

Auto-plunger coil energized as soon as the coin door closes: coil shorted to its bracket

Cause: The metal tab on the coil's mounting bracket had been bent back and cut through the paper wrapper of the coil, touching the winding and connecting the coil to ground, which energized it without the driver.

Checks

• Switch off at once if a coil locks on.
• Test the driver and pre-driver transistors for that coil.
• Reseat the ribbon cables to the driver board.
• Inspect the coil's wrapper and bracket for a tab or burr cutting into the winding; check from the drive lug to ground with the connector unplugged.

Fix

• Straighten or replace the bracket tab and replace the coil if its winding is damaged.

Systems

• WPC DCS

Games

• Judge Dredd

Related tips

• A coil stays energized
• Driver transistor dies after fitting a coil that has a diode
• Why WPC coil diodes are on the driver board
• Coil pulls in as soon as the game is switched on
• Coil-not-working checklist
• Grounding test for WPC coils 1-8
• No 50 V coils work
• Checking the coil supply at TP6

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