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Vertical lines on laptop LCD display

Discussion in 'Electronic Repair' started by Derek, Sep 22, 2003.

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  1. Derek

    Derek Guest

    Hello everyone,

    I have a dell inspiron 8100 laptop, with a 15 in. active matrix TFT
    display ("UXGA" or ultra xga, capable of 1600x1200 resolution). About
    6 months ago, the Sharp LCD on this laptop started displaying a
    vertical blue line (single pixel width) about an inch and a half from
    the right edge of the screen. Since the laptop was no longer under
    warranty, I did a little web research, and discovered that the "flex
    cable", which presumably carries the data bus, reset lines and so on
    (there's a separate power cable), had a tendency to malfunction, since
    it had a 90 degree "twist". Unfortunately, reseating this cable, and
    replacing it did not help. However, I did discover that applying
    pressure to one of the dark plastic (it almost looks like film) areas
    on top of the lcd, near the always-on line of pixel, tended to fix the
    problem. These film-like plastic sheaths seem to be adhered to PCBs on
    the rear of the LCD, but they seem to be non-conducting, and I'm
    unclear as to what their purpose is - there is an elliptical metallic
    area at the centre, and there are sever. They're labeled STAB0, STAB1
    (through stab 12 or so - there are horizontal versions as well,
    leading me to believe that they're associated with the row/column
    control lines for the TFTs) and so on. I cannot find a schematic for
    this LCD on the web, unfortunately. I've used LCDs with attached
    controllers (the HD44780 for instance) for microcontroller projects,
    but those tended to be relatively simple, with an 8 bit data bus and a
    few other lines such as register select, r/w and so on, so I'm rather
    lost when it comes to this sort of display :) Since the problem first
    appeared, it has worsened, and there are now 10-12 lines which are
    "always on". I don't believe the actual transistors are dead, or that
    there's a problem with the display itself, but it seems to be a loose
    contact of some sort. Any thoughts or anecdotes of how this sort of
    problem can be fixed would be appreciated!
     
  2. Andre

    Andre Guest

    <snip>

    I'm afraid that this means the display driver chip for that area is
    fried . The good news is that sometimes they can be repaired . Try
    www.man-machine.com

    If it is FUBAR then they may be able to find a replacement display for
    you, for less than a new one would cost .

    -A
     
  3. Derek

    Derek Guest

    I can buy a replacement LCD on ebay for ~$150, and I'll do that if I
    can't fix the problem. I suspected the control logic for the display
    as well, but given that pressing down on various areas of the control
    lines fixes the problem, I don't see how replacing the chip would
    resolve the issue - seems more like a wiring issue from my
    perspective. Thanks for the response :)
     
  4. Andy Cuffe

    Andy Cuffe Guest

    Derek wrote:
    However, I did discover that applying

    It sounds like you're describing the flex cables that connect the glass
    LCD panel to the driver board. I've seen a lot of these crack, or start
    to make bad contact at one end causing single rows of pixels to stay
    on. When you press on it, it temporarily restores the connection.
    There's no way to repair this type of problem yourself, but I believe
    there are companies that do repair this type of LCD problem. I'm not
    sure if it would be cheaper than an LCD from ebay.
     
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