Video signal sent over twisted pair from controller board to LCD panel

Discussion in 'General Electronics Chat' started by RogueRose, Jun 19, 2015.

  1. RogueRose

    Thread Starter Member

    Oct 10, 2014
    188
    4
    I have an LCD monitor. There is a process/control board which has a harness with 26 wires running to the LCD panel. The wires are twisted pair (at least I think ~20 of them are..). one cable got cut and I had to solder the wire back together. I cut both wires in the pair and it shortened the wire by a tiny amount(maybe 4-5mm shorter total, each wire. I heat shrinked them separately and put the monitor back together. Now I get no picture at all except some strange artifacts racing across a black screen - the artifacts (small rectangles) are all the same color. Could this be the result of shortening the wire and the twisting not being as exact as it once was?


    Is there any way to extend wires such as these?
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,515
    1,246
    Telepathic viewing console is down for repairs... Make/model of monitor? Photo of cable/monitor/process control board? Operating system? Nature of the displayed image (text only, full motion color video, etc.)?

    ak
     
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  3. Randy 7140

    Member

    Jun 17, 2015
    32
    6
    I doubt that the wire being 4-5mm shorter is the issue. If it was twisted originally, It would need to remain twisted(it shouldn't have to be twisted EXACTLY like it was). Double check your connections and make sure you didn't cross the two wires or disconnect any other connectors while working on it. Check for anything else that would have or could have changed from the time it was working. Also just to be safe, double check and make sure you have a good input signal and cable.
     
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  4. RogueRose

    Thread Starter Member

    Oct 10, 2014
    188
    4
    Thanks for the replies. I guess the main part of my question is whether the difference in cable length could make the image out of sync with the rest of the signal on the other wires, arriving before (or maybe after if the solder connection slows it down). I really didn't think the make/model was necessary with this type of issue. I'll check everything again and take some pics.
     
  5. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    631
    In theory yes, but you would have to be taking a few cm or more depending upon the display.
     
  6. Randy 7140

    Member

    Jun 17, 2015
    32
    6
    Yes, it's possible. As Dick said, it would probably have to more than a few cm to actually make a difference. Most likely another connection was compromised while you were working on the unit.
     
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