Testing the switch rows with a clip lead

Steps

• With the game on in Switch EDGE test and 1J8/1J10 unplugged, clip the test lead to 1J8 pin 1 (right-most pin).
• Optionally clip a 1N4004 on the other end, band toward the lead.
• Touch 1J10 pins 1 to 9 in turn (skip key pin 4). Switches 1 through 8 should show one at a time.
• A missing switch, a switch closed with nothing connected, or several switches per pin 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

• Fixing a dead switch row on the CPU board
• Fixing a dead switch column on the CPU board
• Connector 1J10 switch row pins
• A bad SR14 can short switch rows on System 11A and later
• Row or column error: CPU board or playfield?
• A whole switch row or column is dead
• How the Williams switch matrix is scanned
• System 11 switch matrix: connectors and chips

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