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Dell M992 Monitor H.O.T. Replacement issue

Discussion in 'Electronic Repair' started by Bicycle6228, Mar 29, 2007.

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  1. Bicycle6228

    Bicycle6228 Guest

    tick - tick - tick
    The horizontal output FET was dead shorted.
    The original is a P9NC60, a TO-220 case deal, which has scant info on the
    The best resolution datasheet I found is 90% illegible:

    No matter:
    Schematic actually indicates Q504 is a more familiar 2SK2761:
    Side note however: There are some slight differences between the M992 I have
    and that shown in the schematic; but the horizontal output section seems to
    be indentical.
    I got a 2SK2761 and put it in.
    Power up.
    The 2nd anode HV came up OK, but not for long: I heard normal dust crackling
    sounds for about 3 seconds, then no HV, no raster, and the SMPS goes into
    ticking again.
    Yes the new 2SK2761 is now dead shorted.

    The P9NC60 is a metal tab style TO-220, and it had one of those grey
    flexible style insulators at the heat sink.
    The 2SK2761 is a plastic case / tab TO-220, so I used the usual thin layer
    of heat sink compound and left out the insulator.

    The P9NC60 data sheet [ P9NC60.gif ] isn't legible, and I don't know how to
    evaluate the schematic to determine requirements for a good substitute for
    the P9NC60.
    Availability of an actual P9NC60 looks pretty poor (unless I want to order
    1000 of them)
    Are there cases where excessive load downstream results in failure of the
    horizontal output transistor? A shorted horizontal output transformer?
    None of the diodes in this area appear to be shorted.
    Looking for suggestions.
  2. Did you check the two drivers Q502 and Q503 and IC501?
    You'll have to come up with a theory why the first failure occurred,
    and then, wether that may have taken other components with it.

  3. Meat Plow

    Meat Plow Guest

    I would suspect something in the H-drive took the original HOT out. You
    should be using a bit more sophistication in your troubleshooting
    techniques for this circuit.

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  4. Ian French

    Ian French Guest

    This transistor is likely to be made by SGS Thomson and is actually a
    If you do a google search for this you will gets many hits and the first one
    is a downloadable PDF data sheet, and is perfectly readable. Try it !
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