Imac 27 mid 2011 not power on

[Bigsergio]

Hi all firstly sorry about my english. I have a problem with my imac mid 2011 27 i5. Two months ago suddenly lines and buzzes appeared on the desktop and restarted itself. But never boot again, just white screen after apple logo. I tried everything whats writing on the web about this problem. Safe mods, ram resets, recovery modes, linux software etc. but always white screen. I changed my ssd and hdd also but still same. Power on, chime, apple logo and progress bar and just white screen. And for the last option i decided to bake my gpu. Disassembled everything, cleaned fans , baked gpu in owen , made new termal paste on gpu and cpu and assembled again. But now imac not power on pressing start button, fans are starting just for 2 seconds and power gone. Just diagnostic led 1 is on
I try different ways, pull out hdd ssd power cables, and put 1 ram to the slots. But nothing changed. Attached a video to show whats happening when push the power button. Waiting for your opinions thanks for read!

 

[unclemiltie]

Your GPU likely failed and the baking didn't help it. there are options to replace the with a better one, you can read about it in this thread.

2011 iMac Graphics Card Upgrade

iMac 2009 to 2011 MXM3 graphics card upgrade (Lastest update 10/13/2023 - this is the official documentation page - you found it finally!) This is the single and only documentation post. During the last years we constantly updated this post to reflect the lastet development of vBIOS and OCLP...

forums.macrumors.com

Given that you've already figured out how to take the GPU out you can surely do the swap. There are a couple of people on eBay that sell pre-flashed GPUs for Mac that make the process easy.

I tried to re-do my 6970M in my 2011 iMac. Baked it and it lasted a couple of months and then failed again. Sent it off to get the chip re-balled and after about 6 months failed again. The guy who did it told me that the real issue is the solder balls inside the GPU chip package (the chip is flip chip mounted) and the only real way to fix it is to replace the GPU chip, of which there are none available. So I upgraded to a K3100M that I bought on ebay pre-flashed. I'm going to do it again on another iMAc and will probably just build the Linux USB and flash it myself.

In that thread there are discussions of the possible hardware failures and links to service documents that can tell you what to look for and what the LEDs mean.

 

[Bigsergio]

Your GPU likely failed and the baking didn't help it. there are options to replace the with a better one, you can read about it in this thread.

2011 iMac Graphics Card Upgrade

iMac 2009 to 2011 MXM3 graphics card upgrade (Lastest update 10/13/2023 - this is the official documentation page - you found it finally!) This is the single and only documentation post. During the last years we constantly updated this post to reflect the lastet development of vBIOS and OCLP...

forums.macrumors.com

Given that you've already figured out how to take the GPU out you can surely do the swap. There are a couple of people on eBay that sell pre-flashed GPUs for Mac that make the process easy.

I tried to re-do my 6970M in my 2011 iMac. Baked it and it lasted a couple of months and then failed again. Sent it off to get the chip re-balled and after about 6 months failed again. The guy who did it told me that the real issue is the solder balls inside the GPU chip package (the chip is flip chip mounted) and the only real way to fix it is to replace the GPU chip, of which there are none available. So I upgraded to a K3100M that I bought on ebay pre-flashed. I'm going to do it again on another iMAc and will probably just build the Linux USB and flash it myself.

In that thread there are discussions of the possible hardware failures and links to service documents that can tell you what to look for and what the LEDs mean.

Okey thanks very much. Maybe its the only option i have. I'll look at that suitable gpu's

 

[Nguyen Duc Hieu]

I bought a late 2009 27" iMac with a half-dead HD4850.
Tried baking it on a professional reflow station, but it didn't work. (I brought the card to laptop repair shop for this fix)
Gotta buy a Quadro K1100m and everything is working now.

 

[Bigsergio]

I bought a late 2009 27" iMac with a half-dead HD4850.
Tried baking it on a professional reflow station, but it didn't work. (I brought the card to laptop repair shop for this fix)
Gotta buy a Quadro K1100m and everything is working now.

Hi do u know is Quadro k1100m all suitable with mid 2011 27" ? I'll just plug it and nothing do extra?

 

[unclemiltie]

Read the post I linked, it'll tell you everything you need to know about which GPU's will work and what you have to do to make them work (e.g. kext changes, OpenCore, etc)

 

[Nguyen Duc Hieu]

Hi do u know is Quadro k1100m all suitable with mid 2011 27" ? I'll just plug it and nothing do extra?

I speculated that it would work after reading more than a hundred pages of this forum.
But in reality, I don't even know if the K1100m I bought was a defective one or not.
It's kind of hit and miss purchase.
And no, you can't just plug it and do nothing extra. That doesn't work.
You need to do several steps before getting any image shown on your iMac screen.