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

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How to be sure PSU or Main logic is dead?

iMac 21.5 A1311 Late 2011 2.5 QC 2x2GB 500GB 6750M 2.5GHz

I'd like to know how to be sure witch part of me iMac is dead.

But the experiences lived on the same observation does not lead to the same


My iMac does not respond, nothing happens when a press power button.

None of the diagnostic LEDs are on.

My PSU generates a little noise and i can't test pinout without the normals values.

I already try the basic operations.

I would like to be sure of my purchase, if i buy a new PSU.

Thank you.

Answered! View the answer I have this problem too

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I have exactly the same probelem that over here.

No lights on the motherboard .

PSU measure the same values ​​over here. Only 3.6V and 12V and one at 0,06V .

I also ordered a new psu from IFIXIT that I read exactly the same values from.

Is it the motherboard is dead ?

Thanks in advanced!


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1 Answer

Chosen Solution

You have to get power to the logic board to know if it is good and it appears you have no power. Use a multimeter to test the leads into the power supply to make sure the power supply is receiving juice: iMac Intel 21.5" EMC 2428 Power Supply Replacement

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PSU is receving juice..

But the LEDs n°1 won't turn on. Nothing going on..


Same here. I have 230v inn to the psu but no light on logic board.


Same with my 2011 21.5 2.7ghz Quad core iMac as well. No LED's on the logic board and a good PSU with verified power going into the PSU. Where can I use my multimeter to check the board?


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