Find a shorted coil circuit by plugging SDB connectors one at a time
Steps
- Unplug the playfield solenoid connectors J1, J4 and J5 from the solenoid driver board (left side and lower right).
- Fit good fuses and power up, then switch off and plug in one connector at a time, powering up after each.
- When a fuse blows, watch for a spark at a connector pin; look up which coil that pin feeds.
- Check that coil reads at least 2.5 ohms, and check its diode and its driver transistor (page 19).
Systems
Related tips
- How Bally coils are switched
- Test the coils behind the solenoid expander
- No coils work at all
- Flippers and some coils work, others are dead
- Solenoid select lines: MPU PIA U11 to SDB 74154 pin map
- Wrong coil fires or a coil never fires
- Solenoid selection: four MPU lines decoded by a 74154
- Baby Pac-Man solenoid board select lines
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)