iMac mid 2011 will not boot, go to recovery mode or boot from macOS us

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iMac Intel 27" EMC 2429

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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Mathias @pepstdk

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发帖于: 2020年9月19日

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iMac mid 2011 will not boot, go to recovery mode or boot from macOS us

Hi,

My Mac suddenly crashed just when I was full screening a magazine online. Since then the iMac has not been able to boot, boot from macOS USB or go to recovery mode. It just shows a white screen (as in 1st picture)

after eg choosing WiFi for recovery mode (2nd picture). The bar loads, the Apple logo comes on it loads half ways and go to white screen

I can run the apple hardware test (AHT) however it finds no errors...

I have tried swapping the HDD (AHT gives warning of missing sensor) - it doesn't work

I have running off of one ram stick (trying different modules) - it doesn't work

Is it the graphics card? Or maybe something completely different

All help is appreciated

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Dan @danj 声誉积分: 479.4千 Self employed contract worker 35 329 971 · Answer 1 · 2020-09-19T18:28:10-07:00

Dan @danj

声誉积分: 479.4千

Self employed contract worker

35

329

971

发帖于: 2020年9月19日

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Sadly your discreet GPU board has failed you ;-{

The first thing is to fully clean out the dust as a common issue is overheating of the GPU.

You’ll need to remove the the GPU board clean off the thermal paste and pads. We don’t have a 27” guide but the 21.5” will get you there! iMac Intel 21.5" EMC 2428 GPU Card Replacement

Then you have two choices here, the first is baking your board to revive it or you could replace it with anther board (better one)

The last option is to bypass the dedicated GPU and instead leverage the intergraded graphics services within the CPU.

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After getting your system up and running you should install a good thermal monitoring app like TG Pro

由 Dan 完成的 2020年9月19日

That was what I feared :( but thanks for the answer.

I think it may be good to find a new card. Do you have any recommendations for a replacement card?

Also how do I bypass the GPU when the machine is not working?

由 Mathias 完成的 2020年9月19日

You really need to stick with one of the Apple boards as they have custom firmware. They are getting hard to find as others likewise needed to replace theirs as well.

661-5967 - AMD Radeon HD 6770, 512MB

661-5967 - AMD Radeon HD 6970, 1GB

661-5967 - AMD Radeon HD 6970, 2GB

There are a few other choices as well but I would stick with one of these.

由 Dan 完成的 2020年9月20日

Thanks Dan.

So I need to stick with a GPU pulled from a apple machine due to firmware, or can I use any eg 6970?

由 Mathias 完成的 2020年9月20日

The firmware can be re-programed but its a bit tricky! Using one that's not programed creates issues with sleep mode and brightness control.

由 Dan 完成的 2020年9月20日

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iMac Intel 27" EMC 2429

iMac mid 2011 will not boot, go to recovery mode or boot from macOS us

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