A coil does nothing though its fuse is good and voltage reaches it.
A coil has power but never fires
Cause: The driver transistor may have failed open, so the logic ahead of it works but the coil ground is never completed.
Checks
- Confirm the coil itself is good (resistance and the ground-lug test).
- Diode-test its driver transistor.
Fix
- Replace the open driver (and its pre-driver).
Systems
Related tips
- A coil or flasher comes on and stays on at power-up
- Flash lamp stuck on and melting plastics on L/R reversed games
- Quick test for shorted TIP122/TIP102 drivers
- Replace failed TIP122 drivers with TIP102
- Supercharger diverter dead even in test: open TIP102 at Q81 that tested good
- Fliptronics flipper coil wired wrongly
- One pop bumper weak and sluggish though coil and switches are fine: replace Q77
- A coil or flasher energizes as soon as the game is turned on
Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)