This video guide shows how to disassemble the iMac in order to remove and repair the video card, then reassemble and test. As shown in the video, it is highly recommended to label all connectors to make them easier to reconnect without error.

Video Instructions

Late 2009 iMac 27" Video Card Repair — ATI Radeon HD 4850

Late 2009 iMac 27" Video Card Repair — ATI Radeon HD 4850

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Not for the faint of heart and recommended only for someone who has a full day free and isn't afraid to tinker. Since the 2009 iMac is out of warranty and non-functional with a problematic video card, there isn't much to lose by attempting a video card repair. And while I cannot guarantee the "oven bake" method will work in every case, it did work in mine and in the case of many other people whose stories I have read online. Indeed those stories were inspiration for me to attempt the same repair. Even if one does not wish to repair the video card, this video still shows how to remove the logic board and video card and put them back in place.

11 other people completed this guide.

James Wages

Member since: 09/05/2016

504 Reputation

1 Guide authored

I've got a late 2009 27" iMac with the AMD Radeon HD 4850. About six months ago my iMac would occasionally not wake up from sleep mode and I'd have to do a hard reset. As time when on this started happening more often. Then the screen started blinking black and would finally stay black and I would need to do a hard reset to get the iMac working again. Finally, even with a restart the screen would remain black. The iMac was still running in the background but the screen was blank. In Googling the issue I found that it is a common issue with the late 2009 iMac with the AMD Radeon HD 4850. All my research pointed to the video card being the issue. In doing some more research I came across this repair guide by James and decided to give it a try as I really had nothing to lose. I took my time and worked through the video several times. Long story short, once I got the system back together and started it up I had video again. This repair guide was a life saver for me. Thank you James!!!

jcridge - Reply

It's wonderful to hear success stories like yours. I'm so happy to hear your Mac is back up and running again!

James Wages -

Same thing here, i have two imac 27" from 2009, one with i5 and one with i7. Both had a dead graphic Card so i baked one and put in an HD 6970 in the other one and it has finaly worked, both are back one live now!

Thank you very much for this video it helped me so much.

e-mail-patrick - Reply

Thank you for sharing your success story, Patrick! I'm so pleased to hear it!

James Wages -

Bin der Anleitung gefolgt, funktionierte auch bei meinem iMac:

iMac (27", Mitte 2011) A1312 mit GPU: AMD HD 6970

b.b. barnsi - Reply

Das ist schön zu hören. Danke, dass wir uns wissen lassen!

James Wages -

Hi, thank you for your excellent video. One question, how can I know if my GPU is dead? I have the EMC 2309 model. Today my iMac freezes the screen and never boot up again. It stucks in the Apple Logo only.

Thank you for your support.

Martín Vujović - Reply

Forget it, I deleted AMD drivers from Extensions library and the Mac startup normally. But can't use it because not using the GPU everything is extremely slow. I formatted for nothing :/

Thanks anyway for this great site!!!

Regards from Argentina.

Martín Vujović -

Glad you figured out how to solve your problem, and I wish my video card problem could have been solved your way! :-) But you will know when the video card fails because you will experience random freezes and sometimes you computer won't boot. You will also see strange blocks or other artifacts on screen. You Mac may also not wake from sleep. I experienced all these things and they went away when after I fixed the video card by oven-baking it. Best wishes!

James Wages -

Thank you for the video my mac is goosed the same as yours was so I have nothing to loose in chancing the repair .A couple of repair guys in my part of the planet say the repair only lasts months at best ,can I ask is your repair holding out.again thanks for the excellent video

Joe Doyle - Reply

Hi, Joe. I performed the repair in February this year. It is now June. No problems at all during those 3+ months. Keep in mind that I am not the only person who has performed this "oven bake" trick to restore their iMac's video card back to life. The following link is to the YouTuber who was the inspiration for me to try the trick, and he reported in Feb. 2017 that his iMac had been working fine for more than 17 months after his oven bake (which is precisely why I took the time and effort to try it):

James Wages -

Your explanations and the detail you cover in this video is superb. I followed your instructions and completed it last night. So far, so good! Our iMac is operational again so we're back in business. Here's hoping it lasts for a long while. I think I will be buying and storing a replacement video card for if/when it happens again. Hopefully the next time I do this I will get it under 4 hours.

Thank you, James, for this brilliant video!

Dean Bolton - Reply

Thank you for your kind words, Dean. I'm very pleased to hear the video card bake worked for you. Buying a new card would probably last longer than the "bake fix" but in my personal experience, it lasts 3 years. Three years after buying my late 2009 iMac, it developed the video card problem. Apple replaced the video card with a new card, but 3 years later the same thing happened. I would assume the same would be true of any new replacement card of the same model. Whether a different model card would fair better is anyone's guess, but keep in mind they may not fit perfectly if you try them, and there could be thermal issues as well if they run hotter than the stock card. Best wishes!

James Wages -

Hi, my story is in away similar. I am still not sure if the GPU is the issue. Here is what happened:

Yesterday when copying a large video file the estimated time begun to increase. I left my computer for some time. After returning the screen was black with a white spinning wheel.

After some time I shut down the computer pressing the power button. When starting again I could hear the chime then the screen went white and stayed empty.

I connected a USB keyboard and tried various combinations:

Command-R for recovery

D for diagnostics

Then I connected and external bootable drive and pressed Option at start. The same then with a bootable USB stick.

Finally I pressed T to go into the Target mode.

Each time I could hear a chime and then the screen went white and stayed like that.

I haven't ever seen any artifacts.

What is your opinion? Is it a faulty graphic card and it makes sense to replace it or not.


Pawel - Reply

I've read many different reports from people who say their Mac exhibited different things on screen, either artifacts, or totally white or totally black, and sometimes with vertical or horizontal lines. Sometimes there are no screen anomalies but the machine just freezes. In almost every case the culprit is that silly video card. The design of that card is faulty. It would be nice if we could just swap it out for a different card, but the cards that don't appear to have the same fault won't physically fit in the iMac. So we either do the bake resurrection trick or get rid of the Mac and buy a 2015 or later edition. (I have a late 2015 edition 27" 5K iMac at the office and it's very well made -- never had a problem with it -- and it runs cool too.) So even if you "replace" your video card, the same problem will occur 3 or so years down the line. Apple replaced my card 3 years after I had purchased my Mac due to the video card fault, but 3 years later it had the same problem, which is why used the bake.

James Wages -

The best way to recover a broken graphic card is to perform a reballing. I did it a year ago and still working perfectly. The main problem is that contacts between pcb and graphic chip don't work properly, because heat degrades it.

Keibert Falcon - Reply

Keibert, thank you for your comment. I agree that paying someone to reball the GPU chip would probably last a bit longer than the oven bake shown in my video; however, I know from experience that even a brand new replacement video card only lasts about 3 years due to some defect in the design of the card itself. So basically you get 3 years out of a new card, perhaps less out of a reball and a little less, perhaps, with an oven bake. But the cheapest overall solution (costing you nothing but time) is the oven bake. Some people have reported going more than 17 months on the oven bake, so it's not a bad solution for those who want to avoid paying anything.

James Wages -

Having the same problem with my iMac 11,1 (27" i7 2.8 GHz late 2009), I will try this soon. But if this doesn't work, I surely need a replacement card. Which video cards are compatible to a ATI Radeon HD 4850 512 MB? Just in case, no 4850 is available.

Reiner Kief - Reply

Reiner, thank you for your comment and question. I have no experience testing a different video card, but I have read that some newer cards from 2010 and 2011 iMacs will function properly in the 2009 iMac. HOWEVER, I have also read that the physical size of those newer cards is not 100% the same as the stock 2009 video card, which means you may need to do a little cutting if you want to put a newer card in your iMac. Another potential downfall is the fact that those newer cards are faster but draw more power and generate more heat as a result. As such, I can only advise replacement with the same video card. And if ever you decide to get a new iMac, the late 2015 and newer 5K models are great. I have a late 2015 5K at the office. It runs cool and fast, with no video card issues to date. Best wishes.

James Wages -

Hi, I just wondered if the problem doesn’t lay in the thermal paste that’s too old and dried, because of the over heating ?

My son got a old PC from his cousin and we cleaned it from the inside dust, and therefore, I removed the heatsink of the CPU, but when putting it back, I didn’t bother of putting some new thermal paste. So the computer would just work for a few seconds and stop.

Same thing is happening with my iMac, it works, but the screen goes black in just a few minutes, often before the startup has ended.

So there could be a overheating problem in the GPU simply because the thermal paste is out of use ?

It seems too simple ;-)

mraj - Reply

No. I actually did 2 bakes of my video card. After my 1st bake I replaced the thermal paste, but the video card exhibited the same problem 4 months later. If it was the paste, as you surmise, the problem would not have recurred after 4 months. And by the way, after my 2nd bake, the machine is still going strong. I’m into my 5th month of use now. If you open my video in YouTube you will see a link in the description to my 2nd Bake video. Best wishes.

James Wages -

Hi James, thanks for the great video - especially for the detailed instructions! Your video encouraged me trying something I’d never thought of doing myself as a complete layman. The history of my iMac is about the same as yours - I had my graphics card replaced in 2014 and it lasted until 3 weeks ago.

I followed all your steps carefully, applied Arctic Silver 5 to the GPU and MX-2 to the chips, using about 3 grams of the latter. I must admit that while reassembling I damaged some of the contacts of the v-sync-ribbon-cable in the top left corner – the one that broke off in your second bake.

The reason why I’m telling you all this is because since the first reboot the display looks perfect, but the fans or at least one of them is running at full speed. The main noise is coming from the upper right – graphics card corner. I did the SMC-reset as suggested by Apple itself, but that doesn’t help. Would you have any suggestions?

Thanks a lot,


Apfelgarten - Reply

The v-sync ribbon cable you mentioned damaging would not affect the fan speed, so it’s clearly something else. If you forgot to insert any one of the many connectors, or if you inserted one improperly during your reassembly, such could very well cause fans to ramp up. But it would have had to have been one of the connectors pertaining to a temperature sensor. If re-opening your iMac is troublesome (and you and I both know it is), you could opt to just use a software solution to control fan speed. There’s an app named “smcFanControl” which works fairly well. “Macs Fan Control” is yet another app you could consider. But if you simply cannot rest until the root problem is solved, then you will have no choice but to re-open your iMac and check the tiny connectors (those leading to temperature sensors).

James Wages -

Gee - this is somewhat embarrassing! I had actually taken the shortcut and disassembled the graphics card while leaving the logicboard at its place, so there was no need for unpluggimg all those connectors. Now I opened it up again and found no connector attached to the “HDD Temp” socket! And - what’s even worse - I simply can’t find any surplus cable. What’s going on… I guess I’ll have to take the long ride now.

Apfelgarten - Reply

You say you cannot see any connector attached to “HDD Temp.” Simply locate your hard drive (upper middle area) and you should then find a pair of wires attached somewhere on the hard drive, which is the temperature sensor. Following that wire pair until you see the disconnected connector dangling somewhere, then reconnect it.

James Wages -


believe it or not - I do not have a hard drive temperature sensor cable! Is it because of the model (late 2009 - 2374) or the HDD-manufacturer or because I had given the iMac away for a repair cost estimate before I started my own repair attempt - I don’t know. I think it is virtually unthinkable that I could have disconnected such a twisted cable unintentionally on both ends. I thoroughly checked the inside, tilted the logicboard, used a torch and a buddy for help, I watched several videos and read through plenty of repair guides … no chance.

Apfelgarten - Reply

All 2009 iMacs have the temperature/thermal sensor cable attached to the stock HDD. You can see that connector in Step-10 here:

iMac Intel 27" EMC 2309 and 2374 Hard Drive Replacement

James Wages -

Thanks for the nice tutorial! Had the same issue with black boxes appearing on screen, and finally it wouldnt even boot up, but hangs on apple logo. Did the bake, reassembled, but no picture at all appears on the screen. There is no chime upon boot, but the system appears to boot quite far otherwise. The backlight brightness can be adjusted from the keyboard for example. Rechecked all connections twice… Any ideas what to try?

Mikko Parry - Reply

Mikko, I’m sorry you are having problems after your bake. Because of the complexity of the procedure, any number of things could have gone wrong. For example, it could be that you simply neglected to connect a single connector. Or it could be the video card itself wasn’t secured well enough into it’s socket after your bake. You probably would have noticed if you broke a cable (especially those thin ribbon cables) when you opened the iMac, so it’s probably not that but breaking the ribbon cables can cause a black screen. It’s probably just a loose or missing connection. But the bad news is that you’ll need to remove the display again in order to verify.

James Wages -

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