Boot problem with 2011 27" iMac

Question

Boot problem with 2011 27" iMac

Hi There

My 2011 27" iMac had been slow for a while. And here the other day it stopped booting altogether.

When i press the power button i hear the chime and a white screen comes up. but it never shows the apple logo. eventually it will change to the grey screen and reboot.

What i've tried:
Inserted the install cd
SMC-reset
NVRAM-reset

Single-user boot
Safe-boot

Startup manager

Boot to the cd and usb

OSX recovery

unplugging all physical connections to the mac.

tried to unplug one RAM stick at a time

and some other desperate combinations without any results.

At first i suspected a harddrive failure. so i have taken the hdd out and is currently taking a full backup from it. The Harddrive seems to work fine, but it wont show anything different when booting without the harddisk.

My next plan is to try with another hdd and see if it goes through the hardware test and can maybe install with it and live with using a smc fan control bypasser.

It could also be due to a GPU failure, and i have thought about taking the GPU apart and baking it(hill mary attempt of fixing it), since that have worked on some of my other computers GPU's. And honestly, right now it is bricked and without warrenty, so i have nothing to loose.

Any suggestions on what can cause this issue.

Thank you very much

iMac, OS X Yosemite (10.10)

Posted on Aug 14, 2015 3:18 AM

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Answer 1

Linc Davis

Level 10

209,739 points

Aug 14, 2015 5:58 AM in response to LasseNoerskov

iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support

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Answer 2

Aug 16, 2015 2:55 AM in response to Linc Davis

Thank you for linking that page, unfortunately the iMac was over 4 years old (No give backsies!).

If anyone is interested i have an update.
I took it all apart, detached optical drive, power supply and logic board, since it seemed needed for removing the GPU from the logic board.
Detached the heatsink and removed the thermal paste from the GPU.
Then i placed it in my preheated oven for 10 minutes at 200 degrees Celcius with the chip facing down, and left it closed til it cooled down.
I put everything back together with new thermal compound, and it showed up with the "missing boot image" since there was no harddrive connected. I installed an SSD, and is currently installing OSX mavericks from a thumbdrive. So far everything seems to be working.

It is not an easy operation, but to postpone the need of a new iMac, it was definitely worth the hours put into it.

I hope this can help anyone else sitting with a 2000$ brick.

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