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Dell Ultrascan P780 ghosts and fades?

Discussion in 'Electronic Repair' started by GTO69RA4, Apr 19, 2004.

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  1. GTO69RA4

    GTO69RA4 Guest

    I ran across a Dell Ultrascan P780 a few days ago. Flat CRT, made 1999. When
    you first turn it on, lines on the screen (like window borders) ghost very
    slightly. After about 3 minutes it fades to black over a few seconds. Don't
    know about the ghosting, but thr fading out sounded like a loose joint going to
    the tube heater. I prodded around for a while with an insulated probe but
    couldn't jar anything into working again.

    What's the likely problem? Are the two defects related? Could the heating
    element be bad or is there something other than a bad solder joint that could
    cause it?

    Thanks

    GTO(John)
     
  2. John Gill

    John Gill Guest

    GTO(John):
    I just repaired one of these P780 a few days ago. It had real strong
    ghosting next to all the characters on the screen. I had an old junked
    chassis that had high-voltage problems. I took the CRT neck board from
    the junked one and put it one the one with the ghosting problem.
    Perfect picture.

    Most of the time, the ghosting problems are caused by bad capacitors on
    the neck board. Either the internal resistance (ESR) of the capacitors
    goes up in value reducing the action of the capacitor, or the capactance
    itself goes down. If you have no way of checking the capacitors, I would
    just replace all of them. There are not that many on this board.
    Especially replace the one near the video amp IC (the IC with the little
    heat sink on top of it).
    Hope this helps...
    John
     
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