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H/P LaserJet III "50 ERROR" After printing 3 pages

Discussion in 'Electronic Repair' started by Mark & Mary Ann Weiss, Apr 8, 2004.

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  1. I'm servicing a H/P LaserJet III laser printer that exhibits a '50 ERROR'
    after running for a while.

    I think the problem might be a temperature sensitive IC on the DC Controller
    board, because the fuser assembly IS heating up at startup. The printer will
    even print out a Font Test and do about 3-4 pages before the 50 ERROR

    Once the error occurs, opening and closing the printer will not result in
    the drive assembly rotating the rollers 1/4 turn as is usual for a normal
    working LJ-III. This further suggests that it's a DC controller issue.

    The question is which IC is most likely the problem. Anyone have experience
    with this printer from a factory service angle that has seen a statistical
    failure of certain ICs?

    Take care,

    Mark & Mary Ann Weiss

    Hear my Kurzweil Creations at:
    Business sites at:
  2. Nelson

    Nelson Guest

    You might try I found the guy very
    knowledgeable and helpful.
  3. Post here, too:


  4. My guess(tm) is that it's the power block. That directly under the
    upper fan in the back right corner.
    The delayed failure implies that something is getting hot when
    printing. My guess(tm) is that one of the electrolytic cazapitors in
    the power supply (there are two boards) is leaking or dying. There
    are about 4 or 5 small green electrolytics on one of the boards that
    my ESR tester often shows as gone. I replace them all.
  5. James Sweet

    James Sweet Guest

    I fixed a few Laserjet II printers a couple years ago, they each had a bad
    electrolytic capacitor on the board by the power supply.

  6. Thanks for the input, everyone.

    I hadn't thought of the capacitors before. These are on the AC controller,

    Most of the input I've gotten was that the AC controller (the board under
    the fan) was 90% the likely culprit.

    I did a little experiment today, which is still inconclusive:

    Apply heat to the DC controller board. Turn the printer back upright. Power
    up, wait for self test, request fonts printout. It never made it that far.
    If I don't heat up the DC controller, I usually get 3-4 pages out of the
    printer before it displays '50'. I'll have to repeat the test a couple of
    times to see if it's repeatable. Then I'll try the same thing with the AC
    power module.

    Take care,

    Mark & Mary Ann Weiss

    Hear my Kurzweil Creations at:
    Business sites at:
  7. joe devlin

    joe devlin Guest

    A 50 error is the fuser overheating. It could be the fuser itself or
    the AC power module.
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