iMac Intel 27". EMC 2309 (Late 2009, Core 2 Duo 3.06 or 3.33 GHz), EMC 2374 (Late 2009, Core i5 2.66 GHz or Core i7 2.8 GHz)

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Display shows vertical stribes - what have failed?

I´ve read hours worth of forum posts regarding this and similar issues with the display but still not sure how to proceed.

It shows 5 vertical stribes immediately and after Apple logo it stalls at a white/grey screen.

Can boot in safe mode - stribes still there and depending on the background they can appear green and other colors.

Screenshot does NOT show stribes!

External display WILL show stribes.

iMac used as a display - NO errors on screen.

Those green diagnose led lamps (through vent holes) seems to turn on all 4 of them even though I´m having a hard time being 100% sure of the no 4 led.

Boot from a clean 10.10.2 external HD makes no difference to the above mentioned.

Have pulled out the graphics card and sav a little smudge on the connector pin - cleaned it (with clean air) and reaseambled. Still same problem.

I where preparing my self to put my graphics card in the oven or buy a new/replacement one but I´m not sure that it is with the graphics card alone or something else might be causing this. I´m understanding it as my screen shoot should show the error stribes as well, should this be a graphics card failure.

Any suggestions?

Answered! View the answer I have this problem too

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Please give us the last four figures of your serial number so I can check it on the recall list.

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L5RU and I can give you more digits if needed.

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this system doesn't qualify for the graphics card recall. The recalls were for mid-2011 core i5 and i7 iMacs with AMD Radeon HD 6970M graphics cards.

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What you've described indicates a bad graphics board. On these models the video RAM is on the graphics board not shared with the system RAM. Glitches from a graphics card will not show up in a screen shot. You can try the oven fix as a last ditch effort, but that would only fix it if it is a solder joint issue.

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Thank you for clearing up the screen shot element as this was making me unsure what to make of my errors. Would you happen to know a link to a oven fix (in case it would be a solder issue)? I read about it but fail to find it again at the moment. And I also didn't understand how to take apart the graphics board from the cooling plate - incase anyone has a link regarding this particular thing.

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If you google graphics chip oven solder reflow there are several sites out there with instructions. Since reflowing solder in an oven isn't really the right way to do it, I can't say that any one instruction is better than another.

This guide covers the removal of the graphics card and heatsink. There are 4 spring loaded screws that sandwich the graphics card between the heatsink and backingplate. In step 10 you can see the screws on the heatsink, 2 on either side off the heatpipes.

Graphics Card

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Kennet will be eternally grateful.
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