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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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Won't Power On - Even after power supply replacement

I have swapped the power supply on this iMac with one bought from iFixit. It still will not power on. No fans move, no LEDs on the mainboard.

I have checked the input voltage to the power supply and confirmed 118v at board headers. I also measured the output of the power supply and confirmed 3.8 and 12v rails give voltage. The computer still will not power on.

Should I immediately suspect a bad mainboard, or is it possible for the power button to fail? Where is the header for the power button so I can short it manually?


I found the power header and tried shorting it...still no luck

I also tried swapping RAM

Answer this question I have this problem too

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Can you give us some background info on what happened. Do you have a surge suppressor or UPS? Did you get hit by lightning or have a power failure?


Negative on all.

User did not comment on exactly what happened at the time of the failure.


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1 Answer

How does the logic board look - any burn marks or swollen components?

That the customer said nothing and the poor result of replacing a blown power supply says to me voltage overload... perhaps a lightening strike?

I'd contact the customer for some more details.

If this answer is acceptable please remember to return and mark it accepted.

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Brian will be eternally grateful.
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