The flipper buzzes or flutters instead of holding steady at the top.

Flipper flutters when held up

Cause: A broken hold (thin) winding, often broken off at a lug; too little EOS blade tension; dirty or weak cabinet switches; or a badly worn coil stop.

Checks

• Look for the thin wire broken from its lug (the middle lug should have both wires).
• Measure the coil.

Fix

• Resolder or replace the coil.
• Adjust EOS tension, ideally with the game on and the button held, keeping clear of the lane change switch.
• Clean the cabinet switches; replace the coil stop.

Adjusting the EOS live risks shorting it to the low-voltage lane change switch.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• Flipper flutters and is weak: end-of-stroke switch and binding bracket
• Right flipper chatters when held up: plunger not bottoming on the coil stop
• Flipper buzzes when held up
• Flipper coil gets very hot
• Flippers dead, flipper relay only buzzes faintly: replace the relay's diode D1
• Flipper fuse blows
• Where flipper power comes from
• Right flipper too weak for the top lock after a rebuild: lighter return spring

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Three, Clay Harrell (pinrepair.com)