Switch matrix errors continue although the CPU board tests good.
Matrix fault remains with a good CPU board
Cause: Shorts in the playfield or cabinet: two rows or columns touching, or a row or column touching ground.
Checks
- Unplug the coin door connectors and the opto boards and see if the fault clears.
- If not, trace the row and column wiring involved.
Fix
- Repair the shorted or pinched wiring.
Systems
- Williams System 11
- Williams System 11A
- Williams System 11B
- Williams System 11C
- WPC Alpha-Numeric
- WPC Dot Matrix
- WPC Fliptronics
- WPC DCS
- WPC-Security (WPC-S)
- WPC-95
Related tips
- Narrowing a switch matrix fault to the CPU board, wiring or opto boards
- Switch matrix chips on the CPU board
- Row or column error: CPU board or playfield?
- Telling a playfield switch short from a CPU board fault
- Eight switch matrix fault patterns and what they mean
- Using the System 11 switch tests
- How the switch matrix reads a switch
- WPC: phantom switch closures traced to a 4N25 on the -1 driver board
Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer