The game reports a switch matrix row or column problem.

Row or column error: CPU board or playfield?

Cause: Either a playfield wiring fault or a CPU board fault; most shorted columns are a bad 2N3904 at Q42-Q49.

Checks

• Enter switch level test, then unplug 1J8 and 1J10.
• If the switch reports go away, the fault is in the playfield wiring; if they remain, look at the CPU board.

Fix

• For a CPU fault, start with the column transistor for the affected column.

Systems

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

Related tips

• Switch matrix dead after an under-playfield adjustment with power on
• Fixing a dead switch column on the CPU board
• Switch row or column error: CPU board or playfield?
• System 11 switch matrix: connectors and chips
• Inlane, outlane and drain switches all dead: blown switch transistor Q49
• Flipper button resets the game or a slingshot tilts it
• Switch column (drive) circuit on the CPU board
• Lamp and switch matrix transistor positions on the CPU board

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