A pop bumper or slingshot fires on its own although its switch is clean, correctly gapped and open; or the game tilts during play for no reason.
Pop bumper or slingshot fires by itself; random tilts
Cause: The small ceramic disc capacitor Bally soldered across fast-acting switches (and the plumb-bob tilt) leaks with age and registers false closures.
Checks
- Clip one leg of the disc capacitor on that switch, taking care not to cut the small tubular diode next to it (the diode must stay).
- If the false firing stops, the capacitor was the cause (page 17).
Fix
- Replace the capacitor with a 0.047 uF, 50 V non-polarized ceramic disc (the originals were 0.05 or 0.047 uF, 16 V or more). Leaving it off also works on most switches.
- On the plumb-bob tilt, remove the capacitor and do not replace it.
Systems
Related tips
- Switch reads stuck closed, or a pop bumper chatters
- Tilt doesn't work and closing it fires a pop bumper: dirty slam tilt switch
- Pop bumper fires on its own when a flipper is used: replace its switch capacitor
- Flipping scores 10 points: a rebound switch squeezed closed by new rubber
- Hitting switches in one matrix row tilts the game: bad capacitor on the tilt bob
- Bank shot lane scores by itself now and then: replace the switch diode
- Slingshot switch causes a tilt, or PIA chips fail
- Several playfield switches drop out together: worn insulation shorting the start button
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)