OSX Lion + 2011 iMac 27'' + Video = Freeze

Well, I'm happy to report that it's been more than a year since I had my ATI card changed and have not put it on sleep mode since then... AND I've had no problems eversince. I just use a screensaver that's completely black and dim down the screen using an app called Brightness Control and everything's perfect.

Don't you all waste your time doing all these installs and uninstalls and tweaking the GPU speeds and voltage and fans here and there... we've done it all in this thread and it all comes down to one path... you need to replace your GPU eventually!

In 3 words: Thanks! Thanks! Thanks!

Adjusting the voltage to 0.98 did it, and I'm working again at last.

Once more, now in portuguese: Obrigado! Obrigado! Obrigado!

I'm going to bet that within days,weeks, or months your problem will, unfortunately, return. I tried all of the suggestions and ultimately the only thing that seems to have resolved the issue was to replace the GPU.

Yep. Now is the perfect time to backup your hard drive and wait for the inevitable... while you can still see what's on your screen.

Yeap, you were right... the black screen came back to my mid 2010 27" i7 iMac!

Nevertheless there's something bugging me:

1. If I connect the iMac to an external monitor, the external monitor displays the image perfectly for days
2. If I boot with other OS via bootcamp, the iMac works and no black screens
3. If I disconnect every cable, remove ram, do all resets and wait 10 minutes with the iMac unpluged from electrical power, it comes back to life until next random black screen; unpluging is crucial!

Which made me think that:

1. External monitor works - no GPU problem
2. LCD works with other OS - no LCD problem
3. Firmware / static / power issue?

I'll try the "you-bet-this-is-a-true-grounded-plug" solution tomorrow as well as one RAM module at a time before even considering spending cash on replacing hardware.

Just to let you know:

I've changed the iMac connection to a new one which does have ground.

Did a ram removal and left it unplugged for 1 hour.

PRAM reset.

It's been two weeks and it's working flawesly.

Hope this info is useful.

You can add another to the list of faulty Mid 2010 iMac's. Mine has been playing up for the past few months and I've just come across this thread.

Exact same issue as everyone elses on here with artifacts and freezing.

Does anyone know what Apple charge for a GPU replacement?

Scott Bedford,

I paid about $175 for a GPU replacement.

Spoke to my local Apple approved repairer today and was quoted $600 AUD to get it replaced. Quite an Australia tax!

The iMac was nearly unusable today with freezing and crashes so need to get something done. Will make the 1hr 30min trek to the Sydney Apple Store tomorrow and see what they say.

I use SMC Fan Control app to set the minimum fanspeeds higher. This keeps the iMac cooler and helps avert heat-related crashes.

My GPU froze nearly every day. After increasing the fanspeeds, I've gone 2 months with only one freeze (which prompted me to raise the fans a bit more).

It seems to make a difference and is a solution that costs no money.

I'm having to do the same thing on my early 2008 MBP.

Studio K wrote:

I use SMC Fan Control app to set the minimum fanspeeds higher. This keeps the iMac cooler and helps avert heat-related crashes.

My GPU froze nearly every day. After increasing the fanspeeds, I've gone 2 months with only one freeze (which prompted me to raise the fans a bit more).

It seems to make a difference and is a solution that costs no money.

I did that too... as well as a load of other things... it lastes a few months until I had no choice but to change the GPU. There's no other way around it... as this thread proves.

My MBP had the notorious "flickering" screen that Apple had a 4 year extended (12-12-12) GPU replacement warranty on it. Too bad the person that owned this before me didn't know about it and had it fixed. I have been told that it'll cost $400 to fix it. I got an extended warranty when I bought this just in case. Good thing. So next week I'm filing for repair. But I think it will also fix the dropping WiFi. It's been said that a component that is failing and taking the WiFi with it is on the GPU board that will be replaced. Fingers crossed. One thing though, when it fails the deck above the F keys gets so hot it's difficult to touch. That's why I keep the fans running so high. Strange what fails in Apple gear?

Thanks for you posting paulmcg123,

My 2009 iMac 27 would only boot in safe mode leaving me to struggle to figure out the problem. I also had no sound device and video would not play. I replaced Hard Drive (went bigger). Problems remained. That left me to consider whether logic board, graphics card or both were bad.

Seeing your post I removed the ATI2000 extensions. The machine completed start up, sound device (and sound) was back and video played. The video still shows choppiness when videos played. I will continue to figure out. But thanks to your discovery and post my machine is back.

Thanks

We wanna a recall!!!

Some time ago, they call recall for the i7 models from 2011, mine is a i5 from mid 2011.

After 3 years of normal use, My machine start to get worst every day. But isn't only the squares pipocating on screen, it lock and freezes, and the only way to use again, is with physical restart.

I call for phone support on Brasil, and the operator checked my serial and told me that mine isn't on recall.

Sad, because this is a malfunction, and need to be replaced.

Apple before Steve jobs, was more serious then now.

I wanna my money back. Or a new machine without bug.

3 years is a young machine. In the past, mac works for life. I see a lot of power pc still on function.

This is not a user caused problem. A lot of people complain about the same defect.

This is not a cheap machine!

We need to be heard! Where is that Apple from Steve?

Where is my recall, APPLE????

Shame on you!