Seattle, WA
You say these are optos? Most of the time the issue is that the transmitter LED is burnt out. Rarely is it the receiver LED. Order either replacement assemblies or just the IR LEDs and replace them. I bet you’ll be back up and running. Or, desolder a working opto pair from another location and use them to test with the two bad pairs before placing your order. Make sure to take pictures of what wires connect where because if you reverse them the LEDS won’t work. LEDs are a one-way electrical path.
(Topic ID: 292972)
