A seemingly random group of coils won't fire in a game or in test. They have voltage and fire when their drive side is grounded; fuses, switches and the MPU check out.
A group of coils won't fire but fire when grounded: wire off the flipper board connector
Cause: The return wire for that group (through relays on the flipper board side) had come out of its connector on the flipper board. The manual shows this wire as black, but on this game it was white-red, on pin 3 of the ground connector.
Checks
- Find what the dead coils have in common on the schematic.
- Check the connectors on the flipper board for a loose or pulled-out wire.
- Don't rely only on the manual's wire colours.
Fix
- Re-seat or re-pin the dislodged wire in the flipper board connector.
Systems
Games
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Source: Pinball Repair help group!! (Facebook group)