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Only "red" color partially broken on LCD Monitor?

Discussion in 'Electronic Repair' started by Al Fei, Sep 25, 2006.

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  1. Al Fei

    Al Fei Guest

    I searched around and didn't see a problem like this one described.

    The colors on my Norwood 17" LCD monitor started looking strange and
    when I ran the "Color Gradients" test of the CHECKMON program (which I
    got at it was
    obvious that there was a problem with just the color RED (and colors
    made up of combinations with RED). The BLUE and GREEN colors were
    perfect! It's as if the monitor was having trouble showing more than 8
    shades of red correctly when it should handle 256. After the top 3
    rows, instead of a smooth, increasingly fine gradient from dark to
    light, there are just 3 main bands/shades of red color and the
    boundaries between the bands are "jittery". I tested the monitor on a
    completely different PC - same result so it's definitely the monitor.

    When displaying the desktop or most anything but pictures, the problem
    is hardly noticeable but most pictures show annoying and strange color
    splotches. They say the most expensive part of lcd monitors is the
    glass and the glass seems fine so I'm up for trying a repair, but is
    it a bad cap? A bad circuit board or IC? Any ideas?
  2. Try the LCD monitor on another PC and/or try another monitor on this PC.

    The problem could be in your video card or how its color pallette/lookup
    tables are set up.

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  3. Al Fei

    Al Fei Guest

    I've tried both and it's definitely a problem in the monitor.
  4. JW

    JW Guest

    Are you sure what you are seeing as red is actually red?
    On a totally red display, is there any red at all, or is it black?
    With a DVM, verify continuity of pin 1 on the VGA cable, making sure it
    gets all the way to the LCD controller board.
  5. Al Fei

    Al Fei Guest

    CHECKMON also has a "Solid Colors" test - red is red and
    black is black. No problems apparent with this test at all.
    I used different cables on different PCs with the same result.
    I suppose there could still be a pin 1 break between the jack on the
    monitor and the electronics inside the monitor but I think that would
    show more obvious symptoms, not the ones I've described.
  6. Al Fei

    Al Fei Guest

    It looked pretty grim for a while. The "green" color started
    to go just like the red, and then pure black screens started
    having a greenish tinge. I opened up the monitor (it was
    tricky figuring out how to do that without damaging the
    case too much) and nothing looked burnt / broken so I
    ended up buying a new one and using this one with a
    "spare" pc. Today, it wouldn't even hold the sync for a
    viewable picture! So what did I have to lose? I opened
    it up again to do a more complete disassembly and found
    the wire bundle from the logic board to the glass was
    connected through a special plug/jack that was held
    together with 2 dabs of glue. Masking tape was also
    used to hold/stableize the cable to the back of the glass
    near the connector. The plug had started to unseat a bit
    on one side so I re-seated it. That was just part of a more
    thorough inspection of the cards, caps, etc. so I didn't
    think much of it. I still couldn't find anything that looked
    really wrong. But lo, on the first retest EVERTHING

    The way the mounting was, the plug/cable plugged UP
    into the jack and despite the glue and tape, the plug
    had apparently worked it's way loose over time due to
    gravity and movement.
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