After a burnt kickback coil is replaced, the new coil locks on the moment the left outlane switch is closed, taking out the driver transistor Q3 and resistor R17 on the playfield power board again.
Kickback locks on as soon as its switch is hit and blows Q3: coil diode backwards
Cause: The diode on the replacement coil was fitted the wrong way round.
Checks
- A coil that locks on only when its switch triggers, not at power-up, points to the coil or its diode rather than the logic upstream.
- Check the diode band goes to the lug with the power (daisy-chained) wires.
- Test Q24 and Q16 upstream of the driver, and fuse the circuit with a small breaker or the correct fuse while testing.
Fix
- Fit the diode the right way round (or use a correctly built coil), then replace Q3 (TIP36C) and R17.
Systems
Games
Related tips
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- A coil or flasher energizes as soon as the game is turned on
- Flipper energizes and stays up at power-on or game start
- CPU and driver board transistors by position
Source: Pinball Repair help group!! (Facebook group)