Nothing driven by the auxiliary driver board in the backbox (backbox and apron lamps, headlights, light bars) responds in test, though the lamps light if a transistor tab is grounded by hand. Several switches also read shorted.
Nothing on the aux driver board works and switches show shorted: pulled-out ground pin
Cause: A ground wire had pulled out of its pin position in an under-playfield connector, breaking a ground the aux board's logic and some switches relied on.
Checks
- Before replacing more chips, go through the under-playfield connectors and gently tug each wire; look for a pin pushed back out of its housing.
- With a logic probe, check the input chip on the aux board; a floating signal points to a missing ground or a bad decoder upstream.
Fix
- Push the loose pin back until it latches (or repin it), then retest the aux board and the switches.
Games
Source: Pinball Repair help group!! (Facebook group)