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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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2011 21.5" iMac Logic Board Repair Help!

Hey guys!

So I just picked up a 2011 21.5” imac. Previous owner said it wouldn't turn in, put in a replacement powersupply, and still wouldn't turn on. Upon further inspection, only the 4th LED lights up (technically LED #1) and nothing else lights up. I tried using the spare PSU I was given, and a 27” PSU I had laying around. Still nothing, so I assumed it's a logic board issue.

I don't see any damage or corrosion on the board at all, is there a common failure point in these boards I could attempt to pinpoint and fix? I really don't want to spend money on a logic board.

Answer this question I have this problem too

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The most common issue is the MXM GPU board fails.

If the system had been sitting awhile unplugged you likely need a fresh PRAM battery as well.

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5 Comments:

Would the bad GPU cause the system to not boot, and the other diagnostic LEDs not light up?

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Yes, a short can do that. I've seen a few that had a bad cap.

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@danj if I remove the GPU, could I attempt to power it on with it removed? I know I won't get any display image, but hoping to see more diagnostics LEDs light up

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In its self it won't offer enough information diagnostically. I mostly use a DVM to test the power rails and VRM's

I have a few spare GPU boards which I could use to test things. Rarely have I needed to do that. But thats me not someone who is a DIY fixer.

Do you have access to a second known working iMac or the same series which you could borrow the GPU board.

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@danj I don't, but I ordered a barebones logic board for $40

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