Viewsonic VX2000 video noise issue identified

By fw2004
Feb 15, 2010
  1. Hello;
    For several month, I have posted several times about this odd problem I have been having with my Viewsonic VX2000 on the BFG NVidia GeForce 9800 GTX+ 512.
    The symptom is that after the monitor has been running for a while in its native resolution of 1600 X 1200 @ 60Hz, on the DVI input, video noise begins to appear on the screen, mainly in the margins. When I have the monitor set to a lower resolution; 1280 X 1024 @ 75HZ, there is no noise. But if I set it to 1280 X 1024 @ 60Hz, I do get noise.

    This noise starts out as tiny specs barely visible in the margins, and progresses to horizontal lines made up of many scattered bits of white or green seen against a black screen.
    When at its worst, the screen will occasionally (and then more frequently) blank for 100ms or so, reset (the Digital icon appears in the lower right when the screen resets).

    If the monitor is shut off for a while, then turned back on, it takes another 5-10 minutes before the noise begins to appear again, and then it starts out once more as tiny specs.

    Troubleshooting a problem like this can be very difficult if you do not have another computer with the correct output, or another monitor with the correct input to make comparisons, and isolate the source of the problem to the monitor or the video card.

    Just a few minutes ago, I ran a very simple "test" to determine that the problem is indeed the monitor.
    I noticed that the noise had a green tint to it. This lead me to think that perhaps this was something related specifically to the green pixel circuitry. DVI sends out three channels of color; Red, Blue, and Green, so the monitor must process each signal with separate circuitry.

    For my test, I selected the color adjust on the monitor's controls, and User Color.
    I was able to vary the intensity of each color individually in this mode.
    When I moved the green slider all the way to 0, the video noise disappeared completely.
    If I moved either the red or the blue sliders to 0, the noise remained.

    This test appears to conclude that the problem is the monitor, and specifically the green circuitry.
    Of course, there could still be a problem with the video card's green output, but from the other symptoms, specifically that turning the monitor off for a while resolves the problem for several minutes seems to indicate that there is a component in the monitor that goes slightly out of spec as it warms up.

    The only way to absolutely identify the source of the problem as the green circuit of the monitor would be to install a break-out box into the DVI cable, and swap the green with either the red of the blue wires. If the noise shows up on the same color as before, then it is the monitor. If it shows up on the swapped color, then it is the video card.

    I don't own a breakout box, bout it would be easy enough to build one if I had another DVI cable I could cut to make it. Unfortunately, I don't have this cable, so I will just have to assume it is the monitor for now.

    I have just ordered a new Samsung 2494HM 24" wide-screen monitor, so when I connect the new monitor to the same video card, I will be able to make the definitive identification. It will be interesting to find whether my "blind" troubleshooting was correct.

    Of course, if I had a good oscilloscope, I could probe the signals on the DVI cable (with the breakout box) and know whether there is anything amiss with the video signal. But I do not own an oscilloscope, let alone a good one.

    For those who are interested, I will post the final results later this week after I receive my new monitor.

    The Viewsonic will be moved to another computer, and only its analog input will be used, so I do not expect any trouble from it again.

  2. fw2004

    fw2004 TS Booster Topic Starter Posts: 152

    Image of the noise

    Here is an image of the noise on the screen. Exposure time was about 2 sec.

  3. fw2004

    fw2004 TS Booster Topic Starter Posts: 152


    I received my new Samsung 2494HM yesterday, and set it up on my BFG NVidia GeForce 9800 GTX+, running at its native resolution of 1920 X 1080. I have observed absolutely no video noise on a completely black screen.

    This has finally concluded my ongoing investigation on this noise issue.
    I am happy that I don't have to buy a new video card.

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