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t0mp4
Nov 2, 2008, 05:18 PM
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?



Eidorian
Nov 2, 2008, 05:26 PM
That still looks like a logicboard video problem.

t0mp4
Nov 3, 2008, 08:19 AM
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 thatís 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?

tonyl
Nov 3, 2008, 04:15 PM
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 thatís 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?
It looks like a GPU problem. You can try to decrease resolution.

t0mp4
Nov 3, 2008, 04:19 PM
Well, I've done that, tried all kind of screen resolution, doesnít matter, still the same. The picture is taken with 256 colors, which actually gives the most ďreadableď display.

Berlepsch
Nov 3, 2008, 06:33 PM
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.

t0mp4
Nov 5, 2008, 11:47 AM
Screenshot looks the same :-(

Arne
Nov 5, 2008, 01:11 PM
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...

simonhead666
Jan 15, 2010, 10:20 PM
Hi
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

rtrt
Jan 16, 2010, 08:19 AM
Hi
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

Not familiar with some of the terms you use here......

shim
reballed

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