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Completely bizarre monitor problem.

Discussion in 'Electronic Repair' started by CHoaglin, Oct 12, 2003.

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  1. CHoaglin

    CHoaglin Guest

    Folks, I have a CRT which is doing something truly strange.

    Some text is displayed on the screen.

    The top 2/3 or so is displayed pretty much correctly, though somewhat

    The bottom 1/3 or so is displayed upside down and backwards. In fact it looks
    as if the text at the bottom of the screen actually belongs at the top.

    I've checked that the yoke is plugged in correctly already. The connector is
    keyed and only goes in one way.

    If it was a regular monitor I'd just toss it, but it is a 4 or 5 inch CRT
    embedded in a piece of process control equipment.

    Any ideas what might be causing this sort of behavior? I can take a screenshot
    and forward it to interested parties. Does this sound like some sort of bad
    deflection IC, or is it likely to be a passive issue (ie: cap job)

    Thanks in advance.
  2. Not having seen what you are describing, my first inclination would be a
    bad cap in the vertical deflection output - i.e., a peculiar case of foldover.

    Have you actually looked at the deflection current waveform?
    Does it change with warmup?

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