Major imac Video issue

Hi Klaus1,
I'm sorry if my post did any confusing with the original post, but in fact my issue was exactly the same:
as my problem is now solved (so far…) I'm not gonna open a new thread and here is the English summary of the discussion in French, if it can help someone.

I have a late 2009 iMac (2,8 GHz Intel Core i7, 12 Go RAM ans a 256Go SSD replacing the superdrive in addition to the 1To Hard Drive), which worked perfectly until a Graphic Unit issue:

after suddenly having some video artefacts, the iMac simply didn't want to boot, I was stuck with the Apple logo and horizontal lines covering the display…

I first boot in "safe mode" (shift key down) to make the Mac working again, then I found the GC extensions and removed it from the Extentions folder.

This way, you can use your iMac nearly the same as usual even if the display is slow (no more artefacts or freeze : )

As the iMac is declared "Obsolete" by Apple, they don't sell any spare pieces and you cannot find a new compatible GPU anymore, except some very expensive refurbished units…

After searching the web, I finally decided myself to try to "bake" my GC… and it worked!

The process is a bit "touchy" but not very hard:

- unplug the iMac and then, push the start button for 10 seconds,

- remove the front glass (with suction cups, or even your nails!): 20 seconds

- unscrew the display: 8 screws, 1 minute

- carefully unplug all the wires (5?) between the display and the motherboard etc (and don't forget to replug them when you're finished!): 5 to 10 minutes if it's your 1st time and you are a bit anxious…

- remove the display

- find the small wire between the GC and the motherboard and unplug it from the motherboard (don't forget to look how it is plugged: it is very small and difficult to replug because it is located beneath the motherboard.

This way, you don't have to remove the motherboard but it took me 20 to 30 minutes to replug this fu…ing wire!
- unplug the GC, remove the radiator, remove the thermal paste, stickers, and the black foam from the card (everything that could burn): 5 to 10mn

Now you can put your GC in your oven:
I've preheated it at 210° (10mn) and then put the GC on an aluminium sheet ± 10mn

In the meantime, you should clean all the dust accumulated inside the iMac:

I personally carefully use an aspirator and a soft brush to clean everything I can (and it took me nearly an hour do do it!)

When the GC has cooled down, carefully put back a new thermal paste (Arctic Silver is a good one) where you have removed it, and the original foam and put everything back as it was.

Don't forget any wire:

I personally forgot one and my display stayed dark at the 1st attempt… I had to open it again to replug the one I had forgot!

Depending on your skill, it can take 15mn… to 1 hour if you have some trouble to replug one…

Another thing which can be time consuming is to perfectly remove all the dust between the display and the covering glass and I had to do it again several time : (

- When it's done, replug the iMac and boot:

if you've removed the GC extensions from the Extentions folder, you have to put them back where there was.

- To make it work, I had to reboot 1 time in "safe mode" (Shift key down), and then reboot normally, and then…

Ta Daaa: it works!!!

Just in case, I've installed "Macs Fan Control" to be sure that the iMac doesn't go too hot, and I cross my fingers:

it's been working flawlessly for 2 weeks now : )

I hope it my experience can help, but I was sooo upset about the Apple politic considering any product "obsolete" within 5 years that I've launched a Change.org petition (in French for now) to try to make them change this "obsolescence philosophy ", and you can easily find it if you search "Apple : Stop à l’Obsolescence Programmée !".
If you feel like to sign it…

Hello iMacGiverParis (and PhilSurMac also),

Many thanks for the various posts up to this last one summarizing all the activities to be done.

I was exactly in the same case as you, MacGiver (same iMac late 2009, same symptoms, same answers from Apple).

I went through the repair as you explained it.

Same difficulty with the the small wire between the GC and the motherboard: it took less than 1 minute to remove and 30' to plug it again (using my wife's little fingers!).

I unfortunately broke the vertical sync ribbon cable tip when cleaning dust. I checked on some internet posts that it was possible not to mount it, with a very low noise as a consequence.

At the end, the iMac is working fine since 10 days. I hope it will continue a long time!

So thanks again for your efforts and your will to share it with others.

Hi Caribouj,

I'm glad if it helped : )

I don't see the "vertical sync ribbon cable tip" and I hope it will not lead to an issue.

For now, my iMac still works like a charm after 5 weeks and I cross my fingers…

Hi everyone,
Just a quick update of the fix experience (1st replie):
after nearly a year, my iMac is still working without a single problem, and I still cross my fingers… which become a bit painful ;-)