A coil does not fire in play, or it is stuck on (hot, smoking, smelling).
Coil dead or locked on: quick checklist
Cause: Locked on: usually a shorted driver transistor. Dead: wires off the lugs, a broken winding, no power (fuse or a break in the daisy-chained supply wire), a wiring fault to the CPU board, or a bad driver.
Checks
- If the coil is hot, turn the game off and test its driver transistor.
- Check the coil wires and windings at the lugs.
- Check for power at the coil and its fuse; see whether other coils sharing the same wire colour also fail.
- With continuity mode, confirm the coil reaches the correct CPU connector pin.
- Test the driver transistor; it usually fails shorted, but not always.
Fix
- Replace the failed driver (TIP102) and its pre-driver.
- Repair the wire, winding or fuse found.
Systems
Related tips
- 50 V coil dead on an early System 11 game
- Fuse blows, pops and slings dead: slingshot switch stuck shut cooked coil and Q11
- Whole A or C bank of coils dead
- Whole groups of coils or all flashers dead: A/C select relay stuck
- A solenoid does not fire in the diagnostic test
- Wrong coils fire together (A/C bank game)
- Ball sits in the pit and nothing kicks it out: broken coil wire
- Outhole kicker dead after moving the game: broken wire at the coil diode board
Source: Repairing Williams System 11 Pinball 1986 to 1990, Deel 1, Clay Harrell (pinrepair.com)