After work in the backbox or on the clock, the game reports to check fuses F115, F116, J112 and the opto power supply. The fuses are good but the optos under the playfield do not work.
Check opto power supply message with good fuses: reseat the opto board plug
Cause: A bad connection at the plug feeding the opto board.
Checks
- Check every connector you unplugged during the earlier work is back on the right header.
- Measure the 12 V supplies on the power driver board and check C2 there for leakage.
- Check the opto board's own capacitor and power LED.
Fix
- Reseat or repin the connector at the opto board.
Systems
Games
Related tips
- Eddy sensors: electronic ball switches under the playfield
- Clock minute optos miss now and then: repin the plug at the 10-opto board
- New lock optos fitted: those and other optos on the same plug stop working
- Gumball enter opto (switch 87) never registers: replace the LM339
- Checking an under-playfield opto board for bad LM339s
- Optos all read closed at power-on: blown opto supply fuse
- F116 blows a few seconds after power-up with a new clock board: uncut header pins
- Twilight Zone: "clock is broken" error
Source: Pinball Repair help group!! (Facebook group)