2011 iMac 27 graphics card problem?

For what it's worth, I have a Mid 2011 iMac with 6770M GPU, 3 1/2 years old. The GPU failed first with distorted blocks, and quickly deteriorated to vertical green bars at startup, to the point that the OS wouldn't boot.

I took it to my local authorized dealer and after diagnosing the issue and contacting Apple they said it was covered under the replacement program, even though it's a 6770M, and the GPU was replaced for free.

So it seems at least some 6770M GPUs are covered under the 6790M replacement program. It's worth it to take it in and let them diagnose the problem.

Since buying iMac 27" in jan 2011 I have had the same problems with random coloured pixels, flickering, lines etc

Anyone have a fix?

The fix for me was getting the graphics card replaced.

Thanks

This iMac has also been really slow since I purchased it, so could be related to the graphics card problem

How did you get the card replaced?

Assuming you bought it new in or around 2011 and it's been slow since the beginning, you may just need more RAM depending on the base amount of RAM at the time (2 or 4 GB probably). Also, make sure using the Activity Monitor app that you don't have a process constantly using CPU or Drive Activity. A bad background app could slow everything down. Other possibilities is too full of a hard drive. Things are smoother if you still have at least a couple hundred GB free, Worst case would be a failing hard drive which would entail making sure you have a backup and replace the drive.

For repairs you could take it in to an Apple store or a local certified Mac repair place that you trust and/or has good reviews which could be cheaper.

I started getting this issue earlier this year. iMac (27-inch, Mid 2011) 2.7ghz i5, AMD Radeon HD 6770M 512 MB, Mac os X 10.11.3. The screen artifacts seem to happen more often when the system is cold or if the screen is asleep for a long time. I took the system apart and re-applied thermal pads/grease to the GPU but it didn't help. Oddly enough, booting the Mac into save mode then rebooting seems to postpone the affects. Ran ASD/AHT, no problems found.

So I took in my 27" iMac i5 3.1 (mid 2011) with a similar issue, although it never really does the same thing twice. One time it looks like scrambled pay channels, one time it has screen tearing, this time its flashes to white, then back to the screen which is also torn.

I explain the issue over the phone, and the two apple reps I speak to are awesome. They say "just bring it in" and "they can replace the graphics card" under the "quality program" (I guess they don't want to use the word recall anywhere?). So I bring it in to the genius bar, they run a software test...it passes. The guy there was super nice, so he offers to "stress test" it by opening up like 9 Marvel movies at once. It cooks for 10 minutes then the screen gets pixelated, and torn. He reboots launches the software test again...and it passes.

He told me that there is something definitely wrong with the graphics card, but it isn't the particular issue under the "quality program"...seriously? This card fails in "different" ways its that bad?

The kicker is when they told me I could "recycle" the iMac to PowerOn, and put that money towards a new one. I then told them that THIS iMac is a "refurb" from poweron and its a day old...

He then looks up the history somehow and says, yup, it looks like the previous owner had it in for the same reason last month. Why would they let a known faulty computer be sold off as refurbished? This is so shady its not even funny. This video card can't cost more than $50 to make, from a computer that originally cost $2,000...this doesn't exactly motivate me to buy a new one.

I still have my fingers crossed because they were nice enough to keep it for a few days as an "extended check in" to see if they could get it to fail the software test. (I'm hoping its not just sitting in the back unplugged, but whatever). At least PowerOn is being cool and offering a full refund, even though what I really want is a working computer.

Here is a video of my video card that "Passed" the software test...

https://www.youtube.com/watch?v=iF7bcZ2gKSI

Just got the call...after 6 days of being with the genius bar they weren't able to "reproduce the problem". My guess is that I can take it home tonight and reproduce the problem in 15 minutes, but whatever. Its not like I expected them to stand behind their product anyway...but it sure would've been nice.

It's happening with mine when i play youtube videos since capitan upgrade

iMac (27-inch, Mid 2011)
Processor 2.7 GHz Intel Core i5
Memory 16 GB 1333 MHz DDR3
Graphics AMD Radeon HD 6770M 512 MB

i have this issue on my iMac 21.5 inch (build mid 2011, AMD Radeon HD 6750M 512 MB) after updateing from 10.8 to 10.10.5 Yosemite.

That happens after switching the desktops or tabs. mostly a few blocks, sometimes the complete screen is full rgb-colored and a complete freezing.

SMC Resett and NVRAM resett doesn't work well 😟

Follow up on my iMac repair. Apple store replaced the 6770 graphics card last July. It lasted a year and a few months- the artifacts have returned. I guess I'll be out another $150 if I want to repair it again. Thanks, Apple.

I also have 2011 iMac27 with failed graphics card.

I bought $10 toaster oven and baked the graphics card for 10 minutes @380F

fixed

Right now the iMac is cool but I can't boot it up. Progress bar gets half way and it reboots itself.

Run grapher to check if a video card problem

Sounds like it's the video card that has gone.