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Thread: Noise in VGA signal while laptop plugged in

  1. #1
    Maximum Bitrate
    Join Date
    Jul 2006

    Noise in VGA signal while laptop plugged in

    I have recently been getting noise in the form of horizontal light gray lines that bounce around and travel up and down my screen (Xenarc 700TSV).

    -I know it is not a screen issue because I plugged the screen and same cable into another laptop and it works fine.
    -I know its not a cable issue because I tried it on a CRT monitor with a built-in cable and the same thing happened.

    So it must be something with my laptop mobo. The interesting thing is when I unplug it from power and let it run on battery, the noise disappears altogether.

    If I let it run on battery and then plug it back after the battery has lost some charge, the noise is gone until the battery is recharged. So I know its an issue with interference from the power source and the charging circuit eliminates it.

    It happens both when plugged into the original a/c adapter as well as when hooked into the output of my CNX-P2140 which is very clean and stable.

    Does anyone know of a way I can reground or shield something to prevent this? The laptop is a compaq presario 2800t, p4 1.6ghz. Thanks!

  2. #2
    Maximum Bitrate
    Join Date
    Jul 2006

  3. #3
    Maximum Bitrate Borte's Avatar
    Join Date
    Jan 2006
    Make sure that you use the SAME ground point for both the screen and the laptop.
    That helped for me.
    Failure is not an option...
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  4. #4
    Maximum Bitrate
    Join Date
    Jul 2006
    theyre both grounded directly back to my power supply.

  5. #5
    Join Date
    Jun 2005
    Could this be a ground loop ? Check that there is no small voltage between your ground source to battery ground.

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