DIYbanter - View Single Post - Stanley Garage Door Opener Beam Sensor Components

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wrote:

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?

Ask in sci.electronics.repair. If the chip is a microprocessor and
it's bad, you're screwed, but I think it's a generic part, maybe a
comparator, and I don't think it's failed. The most common problems
with garage door sensors are cracked solder joints and broken wiring,
and wires can break inside the insulation (usually where they pass
through the hole in the box) but look fine from the outside.