Coin door test buttons and special solenoid switches are outside the matrix
The coin door test buttons wire straight to the CPU board at 1J14 (the diagnostic button goes to the CPU NMI line), and the six special-solenoid switches use 1J18. Because of this, you can still enter diagnostics even when the switch matrix is shorted.
Systems
Related tips
- How the Williams switch matrix is scanned
- Testing the switch matrix with a logic probe
- Switch matrix resistor networks and their values
- Row or column error: CPU board or playfield?
- Matrix burned by the lane-change switch touching the flipper EOS switch
- Every switch shows active, even with the switch plugs removed: failed PIA at U38
- Playfield switches fire coils and switch columns misread: failed column driver Q44
- Switch matrix dead after an under-playfield adjustment with power on
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Three, Clay Harrell