A coil remains energized even after the TIP122, its pre-driver, the 7408 and the 6821 PIA were replaced.
Coil stays on after the CPU-side driver parts were replaced
Cause: Some 50 V coils are switched by a TIP36 on the auxiliary power driver board; a shorted TIP36 holds the coil on regardless.
Fix
- Test and replace the TIP36 for that coil on the auxiliary power driver board.
Systems
Related tips
- Addams Family: fusing the magnets to protect the playfield
- CPU and driver board transistors by position
- When a driver fails, replace its pre-driver as well
- Circuit dead through the auxiliary power driver board: open zero-ohm jumpers
- What the System 11 auxiliary power driver board does
- What the auxiliary power driver board holds
- Testing driver transistors in diode mode (board out of game)
- A-bank coil not working
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell