Testing the switch columns with a clip lead

Steps

• Take out the backglass and swing the display panel down so the CPU board is reachable.
• Turn the game on and select the Switch EDGE test.
• Unplug 1J8 and 1J10.
• Clip a test lead to 1J10 pin 9 (left-most pin facing the board).
• Optionally clip a 1N4004 on the other end, band away from the lead.
• Touch 1J8 pins 1 to 9 in turn (pin 1 is right-most; skip key pin 6). The display should show switch 1 first, then each number 8 higher (9, 17 and so on) up to 57.
• A missing switch, a switch closed with no lead, or several switches per pin points to the CPU board, usually a column 2N3904 at Q42-Q49.

Measurements are taken with the game on; keep clear of the line-voltage wiring and the high-voltage display supply.

Systems

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

Related tips

• Fixing a dead switch column on the CPU board
• Fixing a dead switch row on the CPU board
• Connector 1J8 switch column pins
• Row or column error: CPU board or playfield?
• A whole switch row or column is dead
• How the Williams switch matrix is scanned
• Testing the switch matrix with a logic probe
• System 11 switch matrix: connectors and chips

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