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Model A1419 / Late 2012 / 2.9 & 3.2 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac13,2

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iMac 27" 2012 does not start, LED#1 on

my iMac went off by itself and now it does not start again. When I activate the power switch the HDD starts spinning up and the USB ports are powered, but there is no chime and the iMac does not boot. Only diagnostic LED #1 is on permanently.

I certainly tried the typical things, change RAM, resetting SMC and checking all connections, but without any success.

I tested the output of the power supply with a DVM. It constantly shows 12V (as long AC is connected), even if the HDD stopped. Also LED#1 is constantly on.

From the fact that LED#2 does not come on I assumed the power supply needs replacing, but the 12V is present at the main power output from the PSU to the logic board, so it seems to work.

I am not sure what else I can test to determine if this is caused by the PSU or the Logic Board.

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Unfortunately replacing the power supply did not solve the problem which was a bit disappointing. I had to replace the Logic Board to get the iMac starting again and the original Power Supply turned out to be fine.

The power supply in the iMac only provides a single voltage (12V 25A), all other voltages are produced on the Logic Board.


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Выбранное решение

You have correctly diagnosed the problem. Power supplies can have partial failures.

Replace it. If by some wild thing it is not the problem you can always return the part. iMac Intel 27" (Late 2012-2020) Power Supply

Here’s how:

iMac Intel 27" EMC 2546 Power Supply Replacement

iMac Intel 27" (Late 2012-2020) Power Supply Изображение


iMac Intel 27" (Late 2012-2020) Power Supply


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Kurt Hardie будет вечно благодарен.
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