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Broken LCD monitor -- Fades out with green tint

Discussion in 'Electronic Repair' started by Antony, Feb 3, 2007.

  1. Antony

    Antony Guest


    My LCD stopped working a while ago and I haven't been able to figure
    out what exactly failed on it.
    This is what it does:

    1) I turn it on, it displays the signal/picture
    2) Several seconds later it fades out with a green tint and then goes
    3) I need to unplug it and leave it for about a minute before I can
    turn it on again.

    Every time I turn it on in this state, it stays on for less and less
    time. I guessed that maybe the CCFL is dead, but don't they usually
    last a long time?

    I have taken it apart and I can't see anything that is obviously burnt
    out/loose/ or just plain wrong.

    Any clue as to what this might be? Or what I should replace?
  2. Meat Plow

    Meat Plow Guest

    If you're interested in repair a good start would be to post the
    manufacturer and model number. As far as the ccfl and circuit, nothing is
    certain when it comes to longevity.
  3. Antony

    Antony Guest

    The LCD Monitor is a

    BenQ FP731 17".

    Not much information available (bought it because it was cheap a few
    years ago).

    I have opened it up and haven't been able to find any bad caps or
    other component damage.

    The ccfl are a pair of dual ccfl at the top and bottom and they are
    about 3mm in diameter.

    Also there is some black deposits on both ends of the lights. These
    deposits for a ring about 1mm thick.
  4. I had a sony with a bad inverter board doing exactly that.
    Try powering the bulbs one by one using an inverter board from an old
    If the picture stays, you have a bad inverter, if it fades, bulb in question
    is bad.
    Most monitors have more then one lamp.

    Bart Bervoets
  5. Antony

    Antony Guest

    I have more than one bulb, 4 to be exact - 2 in the top and 2 in the

    I have taken the entire monitor apart and like I said before, I can't
    find any faults with the inverter circuitry.

    Is it normal to have dark deposits on the ends of the CCFL tube? That
    is what I have and I don't know if that indicates that my tubes are

  6. Jerry G.

    Jerry G. Guest

    The fault you are describing is normaly from a bad inverter board, and
    or the lamps are going bad. Normaly the inverter board and the lamps
    are changed all together at the same time.

    Some LCD panels are not serviceable, while some models are. You would
    have to find out the type of lamps and inverter that is required for
    your particular model, and then shop around to get them.

    The best way to have the parts, is to contact the manufacture service
    rep for your monitor and see if they will sell the parts to you.
    Normaly, the manufactures will not sell service type parts to the end
    user. In this case, you can find out what they will charge you to
    service the monitor themselves. At least, if they service it for you,
    there will be some type of warranty for the work done.

    Considering that the new LCD monitors coming out are far improved, it
    may be worth to buy a new one. I am seeing them with 2000:1 contrast
    ratios, with speeds as fast as 2 ms. The viewing angels, and accuracy
    of colour tracking are also far improved. The prices have also dropped
    by a very high percentage.

    Jerry G.
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