The displays went strange during play, then died; a game can be started, yet the flippers and the ball eject are dead.

Displays out, flippers and ball eject dead after display glitches

Cause: Flux shorting pins 14 and 15 of U11 (4050 buffer) on the display board, which killed the PIA at U51 on the CPU board.

Checks

• Inspect the display board for flux globs or bridges.
• Trace the shorted pins back to the CPU board with the schematic.

Fix

• Clean the display board short.
• Socket and replace the damaged 6821 PIA at U51.

Systems

• Williams System 11
• Williams System 11A
• Williams System 11B
• Williams System 11C

Related tips

• F-14 Tomcat: left credit-display character scrambled
• Fixing a dead switch column on the CPU board
• Fixing a dead switch row on the CPU board
• Switch matrix dead after an under-playfield adjustment with power on
• System 11 switch matrix: connectors and chips
• Four flashes only: U11 PIA, R134 or a bad display
• No sound effects in play though speech works: check the sound board PIA
• Damage after the black and white plugs were swapped

Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell