iMac 27" Late 2013 - Random Shutdown

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iMac 27" Late 2013 - Random Shutdown

My iMac 27" Late 2013 - Have this random shutdown issue, like power chord is pulled out..randomly. I can only start it by plugging out the power cable and waiting for 5 mins and then restarting it.

When I explored the forum it seems the problem dates back all the way to 2010, it is a shame that the problem still persists on such an expensive iMac after all these years and apple is unable to provide a definitive solution.

My machine is less than a year old, still under warranty, also under Apple Care, took it twice to the service centre, here are the sequence of events:

- They have reset the SMC, PRAM, re-installed OS during first visit, problem persisted

- Spent an hour on phone support, again did a web-install of the OS, moved from ElCapitan to Yosemite, problem persisted

- Took it again, they replaced the Main Logic Board...the problem is still persisting

I read a lot of theories online but no definitive solution. Here are some of the theories I came across:
- RAM 16 GB causing the problem...but mine is 8 GB

- All slots of RAM is filled...but mine has only 2 slots filled

- It happens only on i7...but mine is a i5 machine

- Could be because of the UPS, not having a good sine wave....wonder how to test it though !!

Has anyone come across this problem and solved it definitively...please help, as I am losing trust with Apple engineer's ability to solve it...wow! it sounds strange isn't it, world most innovative and valued company is unable to fix such a common problem that numerous customers are facing...and we are losing trust with them.

I am in Bangalore India, need to check on the consumer rights on this, any inputs on this will also help as I believe I deserve a replacement for this defective product. If it was the US, if it is a lemon (take it to fix the same problem 3 times)...even cars get replaced. Wonder how it works here. Any lawyers on this forum?

Dear fellow Apple admirers and lovers of mac (I am one too!) please help.

iMac (27-inch, Late 2013), OS X Yosemite (10.10.5)

Posted on Mar 12, 2016 4:22 AM

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Answer 1

SeaPapp

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Mar 12, 2016 4:46 AM in response to rajesh_kr

Eliminate the UPS and test.

Is your iMac having kernel panics? OS X: When your computer spontaneously restarts or displays "Your computer restarted because of a problem." - Apple Supp…

If so post a recent panic log, they're often helpful Mac OS X: How to log a kernel panic - Apple Support

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Answer 2

rajesh_kr Author

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Mar 12, 2016 10:22 AM in response to SeaPapp

Hello Mike, thanks for your response. There is absolutely no Panics. It is exactly like you pulled out the power chord, just that the power button wouldn't respond after that. I have to plug the cable out and wait for few minutes, plug it back and the powee button will work again. I guess this is what is SMC reset...right?

Rad this old post, exact same problem :

27-inch / 27" iMac Random Shut down

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Answer 3

SeaPapp

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26,492 points

Mar 12, 2016 11:28 AM in response to rajesh_kr

Eliminate the UPS and test. Are you also running software for the UPS? If so uninstall it per the developers instructions. Do you have any other third party perhiperals connected?

Resetting the SMC is done by;

Shut down the Mac.
Unplug the power cord.
Wait 15 seconds.
Plug the power cord back in.
Wait 5 seconds, then press the power button to turn on the Mac.

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Answer 4

rajesh_kr Author

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Mar 12, 2016 8:09 PM in response to SeaPapp

I am not running any UPS software. I have done SMC reset as you suggested. When I am on UPS (Uninterrupted Power Supply) I do hear a buzzing sound from the iMac...does that mean something not good with the UPS power output that could be causing the problem?

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Answer 5

SeaPapp

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Mar 13, 2016 4:28 AM in response to rajesh_kr

Have you eliminated the UPS to test?

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Answer 6

rajesh_kr Author

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Mar 13, 2016 11:51 PM in response to SeaPapp

I used the mac for 2 Hrs on normal power without UPS, it ran fine. So I am starting to suspect it could be the UPS that is causing the problem. When I was trying to test another UPS (which did not have a fast enough switch over time), when it got powered off, encountered the same issue, I had to do an SMC reset to boot it up again.

So here is my assessment so far: iMac is not able to handle the power output from the UPS and on UPS after some time even if the Mac is sleeping (or even shutdown, but powered in) it just gives up and goes dead only way to bring it back is to do an SMC reset.

I can hear a buzzing sound from the Mac when on UPS...perhaps it confirms my theory that UPS power source is the root cause.

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Answer 7

SeaPapp

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Mar 14, 2016 2:54 AM in response to rajesh_kr

I agree that it seems the UPS is the problem. The buzzing you're hearing is likely the iMac power supply and you could be damaging it by continuing to use the UPS.

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Answer 8

rajesh_kr Author

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Mar 14, 2016 10:55 PM in response to SeaPapp

Sorry to say Mike...the UPS theory is busted. Even with no UPS the system went down, and does not boot up without a SMC reset.

Today on mains power I booted up the Mac in Safe Boot mode, when I tried to login .... it went down with some strange graphics that looked like blinds. Then the power buttons stoped to respond.

I think I got a lemon...no doubt...it is just a defective piece.

Getting on with Apple support to see how they are able to address it. If I get it back to the service center it will be the 3rd time 😟

Thanks for your support.

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Answer 9

SeaPapp

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Mar 15, 2016 3:12 AM in response to rajesh_kr

Taking it in is the best course of action right now. Is the service center an Authorized Apple Service Provider?

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Answer 10

rajesh_kr Author

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Mar 18, 2016 7:28 PM in response to SeaPapp

Since my iMac was under warranty as well as under Apple care, the service engineer visited home and changed the power supply board (I believe it is also called the SMC Logic Board...not sure) at home itself...finally I the problem is addressed 🙂

Thanks Mike !

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Answer 11

SeaPapp

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Mar 18, 2016 7:37 PM in response to rajesh_kr

You're very welcome. I'm glad you've got it fixed now.

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