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Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac12,2

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27 "iMac (2011) stops booting with Gray Screen

Hello everybody

I have a gray screen problem with a second-hand iMac and I needs your help. The Mac loading bar will remain at about 2/3, shortly thereafter, the screen is light gray. When booting in safe mode, the loading bar fills up to about 4/5 until the gray screen pops up. The classic "first-aid" tips I have already through, ie I have already tried the following without success:

  1. External peripherals suspended
  2. Safe boat
  3. Reset VRAM (PRAM)
  4. Reset SMC
  5. RAM swapped
  6. Diagnostics performed (only displayed the fan error)
  7. OS Repair over LAN
  8. HDD exchanged (just for fun, then point 5 repeated)
  9. Boot up from external HDD with an installation of High Sierra

My assumption is I'm facing a hardware defect since even a boat from the external Hard disk was unsuccessful.

What would be sensational would be a further tip, if there is still a possibility of a software problem, or a limiting tip, when it comes to a hardware component to exchange.

Answer this question I have this problem too

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The fact you can get into Safe mode as well as Diags tells me the dedicated GPU has failed.

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Follow this IFIXIT guide to Step32 and continue to remove the logic board fully out Installing iMac Intel 27" EMC 2429 Dual Drive Kit (HDD or SSD). Then pick up the process here at Step10: iMac Intel 27" (Late 2009 or Mid 2010) Graphics Card Replacement.

Here are your choices for replacement cards:

  • AMD Radeon HD 6770 with onboard 512 MB RAM - Apple P/N 661-5967
  • AMD Radeon HD 6970 with onboard 1 TB RAM - Apple P/N 661-5968
  • AMD Radeon HD 6970 with onboard 2 TB RAM - Apple P/N 661-5969

I recommend replacing the GPU card Vs cooking it as cooking doesn't really fix the problem.

You'll also need to clean off the old thermal paste and apply a fresh coat on the GPU and you should use thermal pads on the RAM chips when putting on the heat sink.

iMac Intel 27" EMC 2429 Dual Drive Kit Image

Guide

Installing iMac Intel 27" EMC 2429 Dual Drive Kit (HDD or SSD)

Difficulty:

Difficult

—

1 - 3 hours
iMac Intel 27" EMC 2390 Graphics Card Image

Guide

iMac Intel 27" (Late 2009 or Mid 2010) Graphics Card Replacement

Difficulty:

Difficult

—

1 - 2 hours

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