One opto switch (here the gumball popper, switch 74) never registers after fitting a new transmitter and receiver, while every other switch tests fine.
Opto still dead after replacing both sides: the new transmitter can be bad
Cause: The new transmitter LED was faulty out of the box.
Checks
- Look at the transmitter with a phone camera to see whether it emits infrared.
- Trigger the receiver with a TV remote while watching switch test.
- Check for voltage at the transmitter and continuity from the receiver to the opto board.
Fix
- Replace the transmitter with another new one and re-test.
Systems
Games
Related tips
- Gumball enter opto (switch 87) never registers: replace the LM339
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- Eddy sensors: electronic ball switches under the playfield
- Opto does not work: check 12 V at the transmitter connector
- Egg target optos dead after fitting replacement opto boards: refit original receiver
- Telling an opto transmitter from a receiver
Source: Pinball Repair help group!! (Facebook group)