Red and green square dots?

Ratsandwich wrote:

You are all right and wrong.

You are all lucky I will waste some time to settle this.

None of you know how things work, this is why the thread is hundreds of posts long, for a Thermal Failure Issue.

The graphics cards are failing due to inadequate cooling. This is not due to Radeon or AMDs designs it is the heatsink that is directly responsible.

It's not a heat problem. My GPU wasn't running hot when it started failing, and it is running at the same temperatures after baking.

By the way, mine is still working perfectly, as in a full 100% absence of problems since the oven treatment.

So I purchased a new graphics card for my 2011 21.5 in 2.7 GHz imac. The card came with the heat sink connected to it. I followed directions to the letter to replace it (ifixit.com). The imac does not power on now. Checked everything twice, even reinstalled the old graphics card and nothing. when I push the power button on the back of the imac nothing happens, no optical drive or hard drive movement, nothing. I checked the AC cable coming into the power supply and I have voltage. I am at a loss! Does anybody have any help they could offer?

It could be a bad card. Have you attempted to go back to the original?

Yes, I stated that in my post.

After a google search about my issue is has been suggested that the logic board went bad. I don't see how that could have happened? My other dilemma is that the computer has all my info on the hard drive so I cannot just give it to somebody to repair. I don't know what to do at this point?

There may be something inside shorting out or not connecting. You can always mount a drive externally. I'd check to make sure no connections are loose. Never ran into thisissue though.

Can’t mount to external drive when imac will not power on.

They sell USB connectors for SATA drives. They're a few dollars on amazon.com.

Are you messing with me? All 3 of your replies are questions that I have already stated in my post!

Stated: “Checked everything twice, even reinstalled the old graphics card and nothing.“

Your Answer: “It could be a bad card. Have you attempted to go back to the original?

Stated: “When I push the power button on the back of the imac nothing happens.”

You: “You can always mount a drive externally. “

Me: “Can’t mount to external drive when imac will not power on.“

You: “They sell USB connectors for SATA drives. They're a few dollars on amazon.com.“

No. You stated you had a concern on getting your data. I'm telling you how to do it. (ON a different computer).

That said, somewhere along the process of pulling you're card you've either left something disconnected or you shorted it out. Taking the HD out may be the only way to recover what you need, without a logic board replacement.

You may have to contact an authorized Apple service provider and pay to have a full

diagnostic test sequence run on the computer in question. The problem may be involved

& require a new logic board or other components; that may totally cost more than you'd like.

• Find an Apple Authorized Service Provider

Sorry to not have an exacting answer for you to try; as I'm subscribed to this thread, I still

see replies even though the topic began in 2012 and not all of the content is relevant.

Good luck...! 😐

Dudes, I created a support account just to thank RichLove for his tips. I finished a GPU bake last night and I have my iMac back! I'm running a late-2009 27" i7 iMac. Thanks for the good stuff! For everyone on the fence, just go to page 29 of this thread and follow the instructions from RichLove. Oh, and as mentioned elsewhere in this thread, the following link is great for taking the computer apart and putting it back together correctly: https://www.ifixit.com/Guide/iMac+Intel+27-Inch+EMC+2309+or+2374+Graphics+Card+R eplacement/9553

Hi Guys, before baking or doing anything please

try this fix...hope this helps!

2010 iMac with 10.10 Yosemite and Pixels

For months I’ve had a problem with my mid 2010 iMac after I upgraded to Yosemite. I would see pink and green/multicolored squares on my screen.

I thought “oh no, here’s a dreaded GPU issue after 4 years on my Mac hardware”. (I wasn’t that surprised, since after five years I had issues with my first gen Macbook Pro’s GPU.) For a while I dealt with my iMac pixel issue, puzzled why it didn’t happen all the time.

Reducing transparency did the trick. I’m guessing there is an issue with older model iMacs and the newer transparency feature of Yosemite. If you run into this issue after upgrading to 10.10 Yosemite, do the following:

1. Go to System Preferences, the Accessibility:

2. Click on Accessibility

3. Select "Reduce Transparency"

4. Restart Computer

I now have my iMac back to awesome working order and couldn’t be happier! Hope this helps you..Cheers!

I do not want to play bad omen, but this trick was already mentioned on forums, so I tested it, it seems to give results for a while, but the problem does not disappear.

I wish that it works for you :-)

Even if the problem appears after updating, there is no necessarily a relation of causality. In my case this problem appeared after the replacement of the hard drive, I sought solutions, then I reinstall the disc of origin, to note that the problem was always there :-( It's the samefFor users under Yosemite, Capitan… If it's really an AMD Radeon card flaw, and it's seems to be, there is not a lot of software adjustments to make to solve it...

Alex.

iMac 21,5 in mi-2011, AMD Radeon HD 6750M 512 MB, 2,5 GHz Intel Core i5, memory 10 GB,

I know its a late reply but I have solved my iMac 27" 2010 with Radeon 5750 video card.

I had a kernel leak or something due to an error/fault in both Sophos (anti-virus) and also Little snitch (free). I deleted sophos and it was better. I still had green and purple squares on my screen and then i downloaded the little snitch installer/uninstaller and removed it. After my next full power cycle/restart it was cleared.

I had to remember what the last few programs I had altered or installed. I had both these programs installed for over 5 months. So, it took 6 months to fail on my computer.

If you think you have some kind of junk/spam/virus/firewall programs that control a lot of behind the scenes stuff, please erase it and re-install it or use something else.

12 hours in and still no more green and purple squares! The squares ended up being permanently there and changed when i vigorously waved my mouse or adjusted the screen brightness. it would eventually crash my imacs video card and everything else would still work in the background (plex, media server - music, itunes - etc)