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Strange LCD back light failure

Discussion in 'Electronic Repair' started by Andy Cuffe, Mar 6, 2004.

  1. Andy Cuffe

    Andy Cuffe Guest

    I have been repairing a number of older IBM laptops recently and I've
    encountered a very unusual problem with one on them that I thought
    would be interesting to share.

    The symptoms were a good picture on the LCD, but only red was visible.
    Brightness and contrast were normal considering that only one color
    was working. I expected to find either a bad video cable, or bad LCD
    driver. What I actually found was that the CCF tube was emitting RED
    light. It's bright, evenly lit and doesn't flicker. The phosphor
    coating is white and looks like any other CCF tube until you turn it
    on. It's a nice bright shade of red and really looks like it was made
    that way.

    I replaced the tube with one from a similar broken display, but I'm
    still curious about how this could have happened. My first thought
    was a gas leak, but I thought the phosphor determined the color. This
    tube has been stable over at least the 6 months since I first tested
    the computer. I took a picture which I can e-mail to anyone who want
    to see for yourself.
    Andy Cuffe
     
  2. Mike

    Mike Guest

    its a common failure of the tubes.

    the IBM600 was notorious for that.

    it would light red, and then eventually it would clear up to white.

    sometimes not, and the ccfl will shut down.
     
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