The flipper flips but drops or flutters when the button is held.

Fliptronics: flipper will not hold up (flutters)

Cause: A broken hold winding (thin wire off its lug) or a bad hold TIP102, 2N4403 pre-driver or 1N4004 diode on the Fliptronics board; also a blown hold fuse or a bad cabinet opto.

Checks

• Test the coil first.
• Check the hold-circuit fuse.
• Swap the left and right flipper opto boards and see if the fault follows.

Fix

• Repair or replace the coil, or replace the hold TIP102, 2N4403 and 1N4004 as a set.

Systems

• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Fliptronics flipper coil wired wrongly
• Fliptronics II board components
• Replace SE9302 drivers with TIP102, and renew the parts around them
• Electronic spares worth keeping for System 11 boards
• Which transistor drives which WPC solenoid and lamp circuits
• STNG: under-playfield diverter coils lock on during play
• Fliptronics flutter that new transistors did not cure: check the 1N4004
• STNG: diverter coils lock on during play

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Two, Clay Harrell (pinrepair.com)