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Faint vertical streaks on new monitor

Discussion in 'Electronic Repair' started by Wizard of Ozz, Oct 24, 2004.

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  1. I just bought a Samsung Syncmaster 793s 17" monitor. I'm using a very
    old computer, with a very old video card, a SiS 6326 (Silicon
    Integrated Systems) from 1997. I'm using Windows 98.

    I installed the appropriate driver that came with the monitor CD.

    I have read the entire FAQ at and my problem didn't
    come up.

    When I had the display at 800*600 with 75 Hz refresh rate, there was a
    linearity problem. The 2 inches closest to the right and left of the
    screen were slightly compressed. Barely noticeable by the naked eye.
    By measuring the distances using a gif image with evenly spaced lines,
    I calculated the difference (from the center screen) to be between
    5-10 %. In the FAQ it says that cheap monitors can be expected to have
    up to a 2 % difference in linearity (I take this monitor to be on the
    cheapo side). But I solved this problem by changing the Hz rate. And
    that's where my real problem comes in.

    After reading the monitor CD manual to make sure I wasn't doint
    something I would regret, I manually changed the refresh rate to 85 Hz
    (always at 800*600). Perfect! Beautiful image. Except...

    There are these evenly spaced vertical lines, just noticeable, across
    the screen. Others might not complain about them. I'm a perfectionist
    (there's a bit about perfectionists in the FAQ). There's 7 of them.
    They weren't there at 75 Hz. Very evenly spaced, about 4.2 cm apart
    (1.65 inches). They are each 1 mm thick (0.04 inches). They seem to be
    slightly brighter than the sorrounding picture. On a black image they
    don't appear, but on a uniform image of white, red, blue, or green,
    they do. When viewing text, I can't notice them, though they still
    appear in the blank parts of the text screen. They stretch from top to
    bottom. The 2 closest to the left and right side of the screen are
    about 2 and 3 cm respectively from the edge of the screen.

    If I move the screen using the controls on the side of the monitor,
    the lines move with the screen.

    The image, otherwise, is absolutely perfect, beautiful, perfect
    linearity, colors absolutely perfect, no strange noises, no problem
    anywhere whatsoever.

    One possible factor I noticed in the FAQ which might apply: most video
    cards and monitors use 75 ohms, but older stuff might use 50 ohms, and
    this could cause an impedance mismatch. The video card is old, from

    Thanks in advance for any help.

    P.S.: one final off topic query while I'm at it. The specifications on
    the CD manual said the monitor had presert timing modes for vertical
    frequency of 75000 Hz at VESA 640*480, and 85000 Hz at VESA 800*600
    and VESA 1024*768. Sorry for the stupid question, but does this mean
    the monitor will blow up if I change the desktop screen resolution
    from 800*600 to 640*480 without first reducing the refresh rate to 75
    Hz? I read in the FAQ that modern monitors automatically block any
    signal which is incompatible with their hardwired specs. As I read
    this I couldn't help but wonder: what a brilliant tactical move,
    allowing your clients to live so they can shop again another day :) !
    Pure genius! And it only took them 20 years to think of this! [Irony
  2. Craig Hart

    Craig Hart Guest

    At a guess, your monitor simply has multiple faults in the power supply

    The faults simply mainfest differently at different refresh rates.

    Either junk it, or have it professionally fixed.

  3. Jeff Rigby

    Jeff Rigby Guest

    I had vert lines in my monitor using a video card (I can't remember the
    mfg.) It was the video card. Replacing it fixed the problem. Lines showed
    up with different symptoms at different refresh rates. I assumed it was a
    cap on the video card. Bad cap in the power supply (powering the video) in
    your monitor can cause the same problem. The regularity of the lines you
    describe make me think it's the video card not the monitor. vert lines from
    left to right should not be the same intensity or as sharp as you travel
    across the screen.

  4. Craig Hart

    Craig Hart Guest

    If it was the video card, it would have been obvious on the old monitor

    The original poster doesn't say, but implies that he just bought the MONITOR
    (not the whole computer); thus I am assuming he had a different monitor
    working OK previously.

    If this is so, a quick test by swaping back to the original monitor will
    verify. Apologies if I've misinterpreted.

  5. You think that's old? :)
    Well, at least one person in the Universe has done so!
    They probably didn't do much to optimze the design for a resolution
    and scan rate that no one uses anymore except you. Oops, sorry. ;-)
    So the lines stay with the picture? Are they aligned perfectly with
    the pixels?
    Not likely. 50 ohms has never been used recent times.

    You should check the monitor with another video card or PC as it may indeed
    be the video card as someone else suggested. Ignore that guy who didn't
    bother to pay attention to what you wrote and said to junk the monitor.
    Unlikely but no way to know for sure. It really shouldn't blow up.

    --- sam | Sci.Electronics.Repair FAQ Mirror:
    Repair | Main Table of Contents:
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    Note: These links are hopefully temporary until we can sort out the excessive
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    To contact me, please use the feedback form on the S.E.R FAQ Web sites.

    Unlikely but no way to know for sure. It really shouldn't blow up.
  6. Franc Zabkar

    Franc Zabkar Guest

    Do the lines move with the raster, or do they move with the video
    content? What happens if you display a black screen and max out the
    brightness and contrast?

    - Franc Zabkar
  7. I don't understand perfectly your question, but here goes: if I draw a
    vertical line in the screen with photoshop, they will be perfectly
    parallel to that line.
    I'm going to hook up the monitor with another computer to see what
    happens. Thanks for the help.
  8. They move with the raster. On a black screen (a black gif image
    engulfing the screen) the lines disappear completely. Changing the
    brightness or contrast doesn't affect this.
  9. Marlboro

    Marlboro Guest

    That's 1st problem
    That's 2nd problem
    That's main problem
  10. OH YEAH

    OH YEAH Guest

    Ok, I'm confused....

    Is this to say that THIS monitor is no good or just not for this particular
    use? I have one just like it with the same problem. Mine is a secondary unit
    and I have no use for it otherwise, but other than the faint vertical
    streaks as mentioned by the OP in theirs, mine has an otherwise good
    picture. Is it worth my while to sell it? IF this monitor is ok to use and
    anyone CAN use it, let me know. I'll make you a decent deal.

  11. I connected the monitor to another computer and the lines didn't
    appear (did lots of color tests to make sure). So it's the video card,
    after all, apparently. Thanks for helping. [I also tested the old
    computer with the bad video card by playing a Commodore 64 games
    emulator on full screen. This of course changes the screen to some DOS
    type view or something. While playing a game on the emulator in this
    DOS type screen, the vertical lines don't appear, even on a uniform
    colored background.]
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