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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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Power supply works when logic board is disconnected.

iMac is dead.
I tested the power supply separately from the logic board and all the pins match the expected amounts. When I attach it to the logic board, all the pins are dead, zero volts everywhere.

Q: Does this mean there’s a short on the logic board? Wouldn’t the pins still show a voltage since the short is drawing power?

Q: Do I need to supply voltage to the board to find the short?

Answer this question I have this problem too

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1 Answer

Yes, you have a short within the logic board, often it’s the MXM GPU board that fails.

Time to pullout the DVM and check the power rails for a short (without the power supply connected). You’ll need the board-views and schematics for the system.

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3 Comments:

DVM? Digital voltmeter, right? (Just checking) ;)

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Also, can I assume that the power supply is prob OK?

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@Paul Spinelli - Likely, you really need to test the logic board power rails for a short

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Paul Spinelli will be eternally grateful.
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