One position on the crane opto board never shows in switch test. Moving the opto to another position works there, and a known-good opto moved into the bad position fails too.
One crane opto position never registers: failed transistor on the opto board
Cause: A surface-mount transistor in that position's circuit on the opto board had failed (Q6 for opto 6 here). Each opto position has its own small resistor, diode and transistor.
Checks
- Swap optos between positions to prove the fault stays with the board position, not the opto.
- Check continuity from the opto board connector to the switch return on the CPU board.
- Test the diode and resistors for that position, then the transistor.
Fix
- Replace the failed surface-mount transistor (or the board). The slotted optos are listed as QVE11233; another slotted opto with matching spacing also worked.
Systems
Games
Source: Pinball Repair help group!! (Facebook group)