So I have a South Park that was working perfectly. I've done nothing but play the game recently. Today, the Kenny opto stops working. Once in awhile it does register a hit

The transmitter LED is on and positioned correctly. When I break the beam, the red LED on the bottom of the receiver board lights up so the board must know the beam was broken. It doesn't register in switch test.

Here's what I have tried:
-- Reflow solder on all the components.
-- Replaced the IDC connectors with molex.
-- Swapped the opto LEDs with known good ones.

I'm stumped. I don't want to drop the cash for a new receiver board of this is something simple.

Thanks!

I jumped the switch matrix wires in the new molex connector with a diode and the machine recognized the switch closure. I've determined something is wrong on the opto board.

I swapped our the 2N3904 transistor on the receiver board and its working perfectly again.
I hope this helps someone else with trouble shooting these long throw opto boards.