Won’t start after electrical problems

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iMac Intel 27" EMC 2546

Modelli A1419 / Fine 2012 / Processori 2.9 & 3.2 GHz Core i5 o 3.4 GHz Core i7, ID iMac13,2

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Nathalie Spoor @eaglepanther

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Postato: 14 dic 2017

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Won’t start after electrical problems

Hi,

I’ve got an iMac 27” late 2012 which came to me after a company messed with the electric in my clients home. He blew the circuits and after that the iMac is really dead. They got another and I would like to try to bring the old one alive again for my own personal use.

Can anyone tell me if there is a possibility that there is more broken then just the PSU?

I know with pc’s that even the CPU can blow out with electrical peaks. Is this the same with Apple products or are they better protected?

I don’t want to buy a new PSU and then find out that things like the CPU or screen are also broken.

Anyone an idea about this? Even if you say: get rid of that iMac, is an answer for me if you can give me a good reason why.

Thanks in advance

Nathalie

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What are the diagnostic LEDs telling you?

14 dic 2017 da mayer

Which diagnostics LEDs? I’ve never seen any in an iMac. Did see them on a mainboard for a pc but never in a Mac.

14 dic 2017 da Nathalie Spoor

From 2008/2009 onward iMac’s have had them. The 2011 and older systems have them located just to the right of the memory slots. Sometimes covered with tape or just below the lip of the frame.

With the newer ‘Thin Series’ they are located at the bottom left edge of the logic board near the power supply.

14 dic 2017 da Dan

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Which diagnostics LEDs? I’ve never seen any in an iMac. Did see them on a mainboard for a pc but never in a Mac. — Nathalie Spoor
From 2008/2009 onward iMac’s have had them. The 2011 and older systems have them located just to the right of the memory slots. Sometimes covered with tape or just below the lip of the frame.

With the newer ‘Thin Series’ they are located at the bottom left edge of the logic board near the power supply. — Dan

Augustine @salmonjapan Rep: 16,3k 11 17 19 · Answer 1 · 2017-12-14T08:38:24-07:00

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Augustine @salmonjapan

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Postato: 14 dic 2017

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Hi @eaglepanther, well, IMO it is about luck, sometimes, during this case, couple of things can fail.

e.g. hard disk, mainboard, etc

rarely heard about cpu, rams but as mentioned, unless you have another set / close system, which you can test the other components out.

if you have some electronics background..... you can take out the power supply and measure the output voltages. confirm with the part number of the power supply, and google for the pin out schematics. e.g. 12V, 5V, etc

there are several youtube video tutorials, showing on how it can be done to check the power supply.

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I’ve put another HDD in (the old one is in use by the old owner so that didn’t break down).

After the electrical peak the iMac worked a little bit before dying completely.

I’ll try to test the PSU but I’m pretty sure it’s fried.

Do you know if I can test the other components without putting parts in another iMac (which I don’t have, not that type, only older).

14 dic 2017 da Nathalie Spoor

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Thaddeus Lee @thadlee Rep: 55 Experimac Central Mobile 4 1 1 · Answer 2 · 2017-12-14T09:12:58-07:00

Thaddeus Lee @thadlee

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Postato: 14 dic 2017

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I would say follow the basics like resetting the SMC.

https://support.apple.com/en-us/HT201295

On older models there used to be LEDS on the Main Board the showed if it was getting power and such but you probably want to give it a visual inspection to make sure there are no obvious faults like burnt spots.

Unfortunately you will probably need a Multimeter, the Schematics for the iMac and knowledge of how to read Schematics. Worst case scenario is the that the CPU or Graphics card. If its the PSU then that is a relatively easy swap but if there is a component on the Main Logic board that died then you would more than likely need good Microsoldering skills as component level repair is not so easy.

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Sadly I can’t reset the SMC because the iMac won’t start at all. It’s really dead.

I do have a multimeter but never used it but I will try.

14 dic 2017 da Nathalie Spoor

Resetting the SMC is as simple as

Unplug the power cord.

Wait 15 seconds.

Plug the power cord back in.

Wait five seconds, then press the power button to turn on your Mac.