iMac G5 strange vertical lines of squares

Discussion in 'PowerPC Macs' started by t0mp4, Nov 2, 2008.

  1. t0mp4 macrumors newbie

    Nov 2, 2008
    I have a problem with the display of an iMac G5 20". It shows up as vertical lines of small squares.

    If I change screen resolution, the display will look ok for about half a second, and then it comes back again. Anyone had seen this before? (This is does not look like the usual problem with iMac and thin vertical lines.)

    Any ideas?

    Attached Files:

  2. Eidorian macrumors Penryn


    Mar 23, 2005
    That still looks like a logicboard video problem.
  3. t0mp4 thread starter macrumors newbie

    Nov 2, 2008
    Is there anyone who has seen this kind of pattern like the attached image? Actually I've replaced all 1800uF capacitors cause one looked suspect, but still the same pattern.Might it be the GPU that’s broken or any other part? The computer works fine besides the strange graphics pattern.

    Checked with a VGA Adapter to external monitor today, the same pattern shows up... :-(

    Probably GPU then... or might it still be some other component?
  4. tonyl macrumors 6502

    Jan 18, 2006
    It looks like a GPU problem. You can try to decrease resolution.
  5. t0mp4 thread starter macrumors newbie

    Nov 2, 2008
    Well, I've done that, tried all kind of screen resolution, doesn’t matter, still the same. The picture is taken with 256 colors, which actually gives the most “readable“ display.
  6. Berlepsch macrumors 6502


    Oct 22, 2007
    You can make a screenshot of the desktop using Command-Shift-3. When the stripes are also in the screenshot pic, it is definitely GPU related.
  7. t0mp4 thread starter macrumors newbie

    Nov 2, 2008
    Screenshot looks the same :-(

    Attached Files:

  8. Arne macrumors regular

    May 14, 2006
    you could try to boot a Linux PowerPC-Live-CD link older versions of Ubuntu. The fact that the problem is also in the screenshot hints at a software related problem. If in ubuntu the problem doesn't show, you iMac is OK, but you might have to reinstall OS X.

    PS: You could also try to inster the Mac OS X install disc, if the installation launches and the sqares won't appear, it's software...
  9. simonhead666 macrumors newbie


    Sep 28, 2008
    Uxbridge Ontario
    It's the GPU
    I made a 'quick and dirty' shim.. Taped some pennies (About 6 or 7) to the heat sync right above the g5 Logo.. Works great.. I know it's not a permanent fix.. But it's better than nothing!!

    I'm not sure if it's the CPU I'm shimming or the GPU

    you know you have it at the right thickness of shim when there is a 1/4" gap created when you are closing the lid.. just press down and tighten the Phillips screw.
    eventually I will get the Chip reballed, but if this works for the natural life of the machine.. Why bother!!

    Hope this helps
  10. rtrt macrumors 6502a

    Jan 19, 2008
    Not familiar with some of the terms you use here......


    Also you mention a 1/4" gap - this between the inside of the case and the pennies or something else?

    Can you explain a little more please? Pics would be great too :D

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