At power-on the game fires all its ball-hold kickers because it sees every ball switch closed. Switch test shows every switch in the game active (flippers, coin chutes and tilts too), and it stays that way with both switch matrix connectors unplugged from the CPU board.

Every switch shows active, even with the switch plugs removed: failed PIA at U38

Cause: The switch matrix PIA at U38 on the CPU board had failed.

Checks

• Unplug the switch row and column connectors at the bottom of the CPU board: with them off, no switch should show closed, so if they all do the fault is on the board.
• With a logic probe, the column outputs should pulse and the row inputs should sit high with the plugs removed.
• Check the column driver transistors and the SIP resistors on the switch lines, then the TTL chips and the PIA.

Fix

• Replace the PIA at U38.

Systems

• Williams System 11

Games

• High Speed

Related tips

• System 11 switch matrix: connectors and chips
• 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
• Random switch closures, random tilts or slam from bad resistor networks
• Switch matrix dead after an under-playfield adjustment with power on
• How the Williams switch matrix is scanned
• Testing the switch matrix with a logic probe

Source: Pinball Repair help group!! (Facebook group)