Inspect earlier repair work first
On a newly acquired dead game, look at the back of the CPU board for flux residue that marks replaced parts. With the schematic, buzz out every trace from any new socket or part to the parts it connects to; earlier botched work is often the only fault.
Systems
Related tips
- Blanking LED wrong, or all solenoids pulse and blow a fuse at power-on
- System 11 CPU board won't boot after cleaning: worn ROM socket contacts
- System 11 NVRAM upgrade not working: fit it at U25, not U23 (sound RAM)
- Right sling locks on at power-up and a pop is dead: bad 7402 at U45
- Wrong coils fire and drop target dead: bad PIAs, shorted coil diode and Q14
- Which System 11 CPU boards fit which games
- "Checksum Error" at power-on
- Which System 11 CPU boards swap between generations
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Two, Clay Harrell (pinrepair.com)