iMac 2012 27" possible power supply issues

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Level 1

35 points

iMac 2012 27" possible power supply issues

Hi all

I'm supporting someone who is experiencing some very odd behaviour that is pointing me towards an issue with a power supply, but the symptoms are confusing.

The symptoms are:

iMac can 'crash' (return to black screen) at ay time during start-up, immediately following start-up chime, sometimes before then, during OS load, after log-in and whilst using the system.
Each attempt to log-on the system gets a little further along before dying again.
Eventually, once stable the system will continue to operate with no issues for hours and hours.

I have attempted PRAM and NVRAM resets - initially this did the trick but then symptoms started to occur again.

I then reinstalled the OS (High Sierria). Initially, after repeated crashes the system was stable as soon as I took the machine into recovery mode, took the new OS and behaved impeccably after that. This appeared to confirm that it was an OS issue.

I hadn't, however, ever disconnected the power supply cable. When the machine was taken home it then started playing up again.

So, this to me points to a power supply issue of some kind, but what is a mystery. Power supplies either fail or work, not start working after sometime to warm up, or something.

If anyone is able to provide guidance on what the issue could be, to either confirm that it is the power supply module that needs to be replaced, or some other fix, that would be much appreciated.

Steve

Bristol, UK.

Posted on Nov 29, 2022 2:16 AM

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Answer 1

steve626

Level 6

15,083 points

Nov 29, 2022 8:22 PM in response to Wackers

Replacing the power supply on that old a Mac will probably cost more than a new iMac, and that's assuming you can find the right part(s), which will almost certainly be used parts from some reseller or eBay.

You could try to do such a repair yourself, but it is not a straightforward task on that iMac.

The symptoms you describe seem like a hardware fault with a poor connection (solder joint or other) that when cold is intermittently open (fails) but when warmed the metal swells or expands and marginally closes the joint so the circuit works again, but not very reliably, obviously.

You have a 2012 Mac, which is long past its expected useful life. Personally, I like to keep older computers running when I can: I have a 2010 MacBook Air, a 2013 MacBook Air, and a 2015 iMac. Plus newer (2019, 2022) Macs. The 2013 MacBook Air eventually had a failed internal SSD which was replaced. But when the computer stops working well, we recycle it -- as with a 2008 iMac which we sadly recently had to part with (power supply failed).

To truly diagnose your problem would take a trained technician with the right tools and diagnostic software, which might not be available any longer for such an old computer. You would need to pay for this diagnosis and there are no guarantees that there would be a reasonable solution for your situation. I think it might be time for a replacement Mac.

If cost is an issue, Apple and OWC are reliable vendors for used Macs that have been refurbished, often offered with a warranty. There are black Friday sales going on now, in fact.

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iMac 2012 27" possible power supply issues

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