Find the short before refitting a repaired CPU
A switch input circuit that has failed was often killed by a switch wire touching a power wire in the playfield (coil voltage, lamp matrix or GI). Find and clear that short, or the repaired board will fail again.
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
- Telling a playfield switch short from a CPU board fault
- Why CPU U20 fails and how to replace it
- Switch matrix chips on the CPU board
- Testing CPU switch columns with the switch levels test
- Testing CPU switch rows with the switch levels test
- Early System 11 CPU connector 1J9 was never used
- Decide whether a phantom switch is in the playfield or the CPU board
- Bussed versus isolated resistor networks on the CPU board
Source: Pinball Machines: How They Work & Troubleshooting, Norbert Snicer