Testing the switch matrix with a logic probe

Steps

• Game on, Switch EDGE test, 1J8 and 1J10 unplugged.
• Power the logic probe from the board.
• Probe 1J8 pins 1-9 (columns): each should show PULSE.
• Probe 1J10 pins 1-9 (rows): each should show HIGH.
• Any pin without the expected signal means a CPU board fault.

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

• How the Williams switch matrix is scanned
• Fixing a dead switch row on the CPU board
• System 11 switch matrix: connectors and chips
• Switch matrix resistor networks and their values
• Coin door test buttons and special solenoid switches are outside the matrix
• Row or column error: CPU board or playfield?
• Matrix burned by the lane-change switch touching the flipper EOS switch
• Testing the switch columns with a clip lead

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