General illumination flickers or is out; the GI connectors at the power supply are browned or burnt.

Burnt GI connectors on the power supply (System 7, Hot Tip, Lucky Seven)

Cause: System 7 runs the GI from the transformer through a round two-pin connector into the power supply board and out through a .156 inch header; Hot Tip and Lucky Seven use .156 inch headers for GI. These connectors overheat early.

Checks

• Look at the two-pin GI input plug and the nine-pin .156 inch output plug at the lower right of the power supply board.

Fix

• Replace both halves of each burnt connector: the board-mounted header and the wire-side housing and pins.
• Use a new square 9-pin .156 inch header with Trifurcon crimp pins in the wire housing.
• For the System 7 two-pin input, replace the solid-pin PCB header and the matching housing and .093 inch pins.

Systems

• Williams System 7
• Williams System 3

Related tips

• Replace CPU board power connector 1J2
• Replace the 3J6 logic power connector
• Burnt +5 V output connector on the 80B power supply
• Burnt GI plugs on the power supply board
• Connector stock for burnt-connector repairs
• Ground mod step 2: repin the power supply to CPU power cable
• Use crimp-on pins, ideally trifurcon, when re-pinning connectors
• Molex crimp pin part numbers

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