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Model A1311 / Mid 2011 / 2.5 & 2.7 GHz Core i5 or 2.8 GHz Core i7 Processor

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LCD screen flickering on my iMac 2011

imac 21.5 mid 2011

I was instaling SSD drive into my mac and my LCD start flickering since than. I also replaced thermal paste on CPU and graphic card and add some more RAM during this upgrade.

I tried to replace ram and cpu (I have a spare one) led driver board (doesnt help) and v sync cable (was damaged so I order new one- does not help at all). I also try to remove SSD and the problem is still here. On external monitor is everything just fine. I am not able to find any damaged part on my logic board or PSU. Everything else is working ok.

What do you think? Do I need a new LCD?

Update (05/04/2017)

New update. When it goes black I am still able to see desktop with flashlight.

Update (05/04/2017)

I perform apple hardware test with my flashlight and it gives me code 4SNS/1/40000001 : VGOR - 10.344

Does anybody knows what does it mean?

Update (05/04/2017)

Another hardware test. Code 4SNS/1/40000001 : VGOR - 10.382

Update (05/05/2017)

New update. LCD completely stops flickering and when I turn on my imac it boots and after a few seconds it restarts itself very quickly and keep restarting again and again so i unplug whole LCD and now it works normally with external monitor. Does this mean my LCD is gone or maybe my power source?

Update (05/05/2017)

Now it is not able to start at all it just spins wents and shuts off.

Answer this question I have this problem too

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1 Comment:

i think your graphic card is broken men.


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1 Answer

when it flickers press f3 and it fixes the issue temporary.

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No this not solve the issue.


its a graphic issue! you have to find out whats triggering it. mines starts when I google images. then I hit f3 and it goes away. last year I had the issue and I wasn't sure what was causing it, I took it to apple store and they couldn't figure out either so I deleted all the games and apps then it went away for a year...


No this is not helping. Imac is not able to start at all now. It looks like cascade issue.


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Petr Jaroň will be eternally grateful.
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