Lamps glow dim, flicker or work only when the bulb is wiggled.

Dim or flickering lamp sockets

Cause: The fiber insulator inside the socket shrinks with age, loosening the parts so moisture gets in and corrodes them.

Checks

• Wiggle the bulb and socket while lit.
• Check whether the socket parts are loose.

Fix

• Repair playfield sockets by soldering (see the socket repair procedure).
• Replace backbox sockets, which rarely repair well.
• To clean the inside, spin a rubber socket cleaning pencil in a cordless drill for a few seconds. Some people use DC4 silicone grease to keep air out, though the real fault is mechanical.

Systems

• Electro-mechanical

Related tips

• Lamp flickers or is out with a good bulb
• Bally lamp sockets are the weakest
• Playfield lamp fuse blows when one pop bumper fires: lamp socket shorting
• Change pop bumper lamp sockets from wedge to #47 bayonet
• Single lamp out, dim or flickering
• Use #47 bulbs, not #44, in EM games
• Gottlieb feature lamps burn too bright (28 V through a resistor)
• Wedge sockets in older wide-body pop bumpers: the bulb may not clear the cap

Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part One, Clay Harrell (pinrepair.com)