The flipper stays in the raised position.

Flipper stays up after the button is released

Cause: Electrical (a welded cabinet switch keeping it powered) or mechanical (a mushroomed plunger binding in the coil sleeve).

Checks

• Switch the game off. If the flipper drops, the fault is electrical; if it stays up, it is mechanical.
• For electrical faults, check the cabinet flipper switch contacts, which can weld together (page 73).

Fix

• Separate and file or replace welded cabinet switch blades.
• For a binding plunger, remove the coil stop, move the coil aside, loosen the two pawl set screws, take out the plunger and link, and file the mushroomed end smooth (page 74).

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35

Related tips

• Flipper machine-guns when the button is held
• One flipper dead with fuses good
• Solenoid fuse blows when a flipper is used: worn spacer in the EOS switch stack
• Check a flipper coil for heat damage by its sleeve
• Set flipper rest angle and end play
• Right flipper still dead after fitting a new coil: bad EOS switch
• Flipper sometimes ignores the first button press: replace the EOS switch
• GI dims whenever the left flipper button is held: upper left flipper EOS not opening

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)