With the magnet holding a ball, pressing the upper right flipper button only makes the flipper vibrate and buzz; it flips normally once the magnet lets go, and works fine whenever the magnet is off.
Upper right flipper only buzzes while the magnet holds the ball: failed opto-isolator
Cause: The game should switch the magnet off when that flipper is pressed so the flipper can sweep the ball away. The 4N25 opto-isolator on the interconnect board that does this (U3 for the right flipper circuit here) had failed.
Checks
- Hold the ball on the magnet and press the flipper: the magnet should release at once.
- Check the opto-isolators on the interconnect board for the flipper circuit concerned.
Fix
- Replace the failed opto-isolator.
- While there, set the magnet core height correctly: a core sitting too low wears the playfield.
Systems
Games
Related tips
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- Phantom switch closure that survives a new CPU board: bad 4N25 on the driver board
- WPC: phantom switch closures traced to a 4N25 on the -1 driver board
- Row or column "ground short" errors
- Rollergames upper flipper too weak to make the ramp off the magnet: wrong plunger
Source: Pinball Repair help group!! (Facebook group)