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Model A1312 / Mid 2010 / 3.2 GHz Core i3 or 2.8 & 3.6 GHz Core i5 or 2.93 GHz Core i7, ID iMac11,3

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Diagnostic LED 1 blinks once

so i’ve recently been given a Mid 2010 27” iMac that wasn’t powering on. Initially i thought i must most probably be the Power supply that had croaked it and needed to be replaced because when i plug in the power the diagnostic LED 1 flashes once then once again but not as bright that second time, as if it was loosing power. No other LEDs are lit.

I have replaced the PSU with a known working unit but still getting the same thing.

im hoping its not the logic board that has an issue or a short on it,

is there any chance it would be the jack/EMI unit where the power goes into the imac?

Answer this question I have this problem too

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1 Answer

You have a short within the logic board and/or the MXM video board.

My money is on the video board! Do you have the correct one to test things?

Otherwise its following the power rails with a DVM and a set of schematics and boardview drawings.

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2 Comments:

Thanks! But darn was really hoping for the video board being the issue. Removed it but am still getting the same problem.

Must be a short on the logic board then.

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@ahkoo - Follow the yellow brick road ;-}

Get a DVM and a set of schematics and boardview drawings following the power rails and check the caps.

You might want to find someone with the deeper skills to help you.

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Ahkoo will be eternally grateful.
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