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Garage door control board

Discussion in 'Electronic Repair' started by Charles, Mar 6, 2013.

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  1. Charles

    Charles Guest

    No joy on finding a schematic for a LiftMaster control board. Thought I'd
    ask here.

    The remotes (4 of them) work flawlessly to open the door. They also work to
    close the door, but only after the built-in overhead light turns off. That
    takes about 2 minutes.

    Checked the obvious for the beam sensor: sensor obstruction, sensor wiring,
    sensor lenses, sensor alignment. The wall switch always works.

    Any ideas?

  2. tm

    tm Guest

    Are you using CFLs in the unit?
  3. Charles

    Charles Guest

    "tm" wrote in message

    Are you using CFLs in the unit?

    No, just an ordinary incandescent. I see your point ... high frequency
  4. tm

    tm Guest

    If you turn the light on before opening the door will it cause the same
    problem? How about if you remove the bulbs?
  5. Guest

    Any luck at or ? Liftmaster is the same
    as Chamberlain and Sears Craftsman, only with a one-piece overhead

    I found that the optical sensor can seem OK and its LED seems to
    glow steadily, but in reality it may be cutting in and out very
    rapidly because of a bad wiring connection from motor vibration,
    which also eventually cracks some of the solder, all over.

    If your wall button isn't lighted, it can cause problems with the
    optical sensor -- something about the lack of a pull-up or pull-down
    resistor. Chamberlain used to give out lighted wall consoles to
    fix this problem, but if you phone them, talk to an electronics
    tech instead of an installation tech.

    Could the driver for the relay of the overhead light be at fault? I
    had a protective diode across a relay coil blow and cause intermittent
    glitches with an opener.
  6. Guest

    Unscrew the overhead light and see what happens and let us know.
  7. Charles

    Charles Guest

    "" wrote in message

    Unscrew the overhead light and see what happens and let us know.

    No effect.
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