One pop bumper has a history of firing on its own in bursts, and now its return spring keeps jumping off the coil plunger.
Pop bumper auto-fires and its spring jumps off: the metal yoke is missing
Cause: The metal yoke had been left out when the bumper was last rebuilt, leaving only the fibre link, which wore and let the rods and plunger run out of line.
Checks
- Compare the assembly with a neighbouring pop bumper; the stack should be washer, metal yoke, fibre yoke, then lock nut.
- Check the coil sleeve and plunger for wear, and the bumper's leaf switch gap (too close lets vibration trigger it).
Fix
- Fit a new metal yoke and fibre yoke, plus a new plunger, spring and coil sleeve, and regap the bumper's skirt switch.
Systems
Games
Related tips
- Pop bumper keeps firing until its coil smokes: skirt caught under playfield protector
- Pop bumpers do not show in switch test: pull the ring down to test them
Source: Pinball Repair help group!! (Facebook group)