iMac Will Not Turn On

Question

iMac Intel 21.5" Ende 2012

Modell A1418 / Ende 2012 / 2,7 & 2,9 GHz Core i5 oder 3,1 GHz Core i7 Prozessor

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steharmon @igoinggray

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Veröffentlicht: 20. Jan 2017

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iMac Will Not Turn On

I have a late 2012 iMac 21.5" that will not turn on. Black screen, no gong, nothing...

I've disassembled the iMac and looked at the diagnostic LED's and found that only LED #1 (at least I believe it is #1) is the only one that turns on. I then tested the power coming from the power supply which is giving me 11.79 volts on the following Pinout.

0 - ground

0 - 11.79 vdc

From what I read this is pointing to the logic board but I wanted to make sure from the Pro's out there in this forum. Shouldn't I at least be getting 12 vdc and not under that? I've watched it drop from 11.84 vdc to 11.79. Please see the following pictures to understand what I described above.

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Did you end up fixing it? i have the same problem with mine

3. Jun 2017 von Ryan

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Gewählte Lösung

Jon Ridley @thebookyard

Rep: 6 Tsd.

The Bookyard

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Veröffentlicht: 11. Jul 2017

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I see this question is backdated a bit and hasn't been replied to. I dont know if you still need input on this one or if its too late.

LED one indicates that the logic board is receiving a trickle charge from the PSU. when you push the power button, the second LED should come on, indicating that full power has been received, then the 3rd indicates the GPU initialising, and the 4th indicates the LCD is connected and enabled.

if you get no second LED, then i'd initially check that the power button hasn't been damaged.

You can start by unplugging it and shorting out the power pins.

If you still get no response, then it could be PSU or logic board, but its hard to trace without a process of elimination of some kind.

I hope this helps.

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Hi Jon

I also have a problem with mine.

It is a EMC 2544 Imac I believe a 2.7ghz

I has seen little use since it was purchased, and isn't left running when not in use.

Anyway it wont power on at all.

I haven't yet dis assembled it. This happened a few weeks ago, and after a couple of tries I was able to get it to boot.

I have tried the power on for 10 sec then again trick. I have also checked and tried different power cords.

I haven't contacted apple yet to get a quote on a power supply replacement.

I have seen the part online for around $130.00 any other tricks to try before I tear into this thing?

Thanks

Daren

19. Jun 2018 von Daren Fentiman

Opening is the part you want to be careful with. We recommend using the correct cutting wheel and tools for it. Apple made one, but so did iFixit, which is a great tool for getting the LCDs off. You'll also need replacement tape for when you rebuild it.

Diagnostics of a power fault, start with the diagnostics LEDs on the logic board. They are there to see how far the power is getting through the board.

But once you know the fuse is OK in the mains cable, and you've had intermittent boots recently, there isn't much else you can test without opening the machine up unfortunately.

20. Jun 2018 von Jon Ridley

where I can buy online in Australia , logic board EMC 2544 imac 21,5”

31. Okt 2018 von tatiana

Not sure of any operators in Australia, but we ship to Australia from the UK.

www.thebookyard.com

15. Apr 2019 von Jon Ridley

Hello Jon, I have a similar issue. Only the bottom LED stays green and nothing else happens. What can I do to see it is a faulty power supply unit? Thanks

16. Jun 2020 von Sergio Manrique

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Hi Jon

I also have a problem with mine.

It is a EMC 2544 Imac I believe a 2.7ghz

I has seen little use since it was purchased, and isn't left running when not in use.

Anyway it wont power on at all.

I haven't yet dis assembled it. This happened a few weeks ago, and after a couple of tries I was able to get it to boot.

I have tried the power on for 10 sec then again trick. I have also checked and tried different power cords.

I haven't contacted apple yet to get a quote on a power supply replacement.

I have seen the part online for around $130.00 any other tricks to try before I tear into this thing?

Thanks

Daren — Daren Fentiman
Opening is the part you want to be careful with. We recommend using the correct cutting wheel and tools for it. Apple made one, but so did iFixit, which is a great tool for getting the LCDs off. You'll also need replacement tape for when you rebuild it.

Diagnostics of a power fault, start with the diagnostics LEDs on the logic board. They are there to see how far the power is getting through the board.

But once you know the fuse is OK in the mains cable, and you've had intermittent boots recently, there isn't much else you can test without opening the machine up unfortunately. — Jon Ridley
where I can buy online in Australia , logic board EMC 2544 imac 21,5” — tatiana
Not sure of any operators in Australia, but we ship to Australia from the UK.

www.thebookyard.com — Jon Ridley
Hello Jon, I have a similar issue. Only the bottom LED stays green and nothing else happens. What can I do to see it is a faulty power supply unit? Thanks — Sergio Manrique

iMac Intel 21.5" Ende 2012

iMac Will Not Turn On

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