I'm looking for some advice on troubleshooting/fixing the obstruction beam sensor assembly (part #49522) on a Stanley Quite-Glide garage door opener (model UT605-F09).
The red LED on the sensor used to be on all the time and the beeper would only sound when the beam was broken. Now, the red LED is off all the time and the beeper sounds every few seconds. I tried cleaning the optics and setting the sensor/emitter up on my workbench, independent of the motor unit, with a separate 12 VDC power supply. Even with the sensor and emitter lined up a few centimeters away from each other, the red LED won't light up and the beeper sounds. I can hear a faint buzz from the sensor board when the emitter is pointed at the detector. The buzz goes away when I hide the emitter.
The resistors and capacitors on the sensor's circuit board look to be in good shape (nothing is burned out or leaking), so I suspect either the phototransistor, the IR LED, or one of the other semiconductor components is shot. I'd like to try replacing them all before giving up on the unit. The transistors and diodes are labelled clearly enough, but I'm not sure what parts to buy to replace the optoelectronics and the 8-pin chip (labelled P7104 I 7507807 µEM810G). Can anyone help me identify them?
Thanks in advance for your help.