Q: Why does my iMac 27" (late Dec 2012) keep shutting down unexpectedly?

Do you have any kernel panic reports? If so, post.

OS X: About Kernel Panics

Resetting the System Management Controller (SMC) - Support - Apple

Try and reset the SMC. See if the issue persists.

I have the same issue with my iMac 27"!

It happened only recently, like 2 weeks ago. Not sure if it is a software issue or a hardware malfunction.

It is weird that you can't power on immediately. A SMC reset seems to be needed, but sometimes I need to wait like 1 minute before it can power back on. Frustrating.

I seems to encounter this shutdown when I perform some tasks that use access the data a lot eg. forwarding a video in VLC, going to sleep mode.

Where you able to resolve this? I'm having the same issue on a system I bought in January.

Today my iMac 27" 2013 power off twice at 9:23am and at 9:41am, both times unexpectedly.  I had to unplugged it from the battery backup both time, wait a few seconds to plugg it back.  Battery backup working perfectly.  This happend last week but I am starting to get scare.

I was hoping it is a OS issue.. But it's not.

I updated to Mavericks today, and still getting random shutdowns.

I have kind of the same problem.. Can you help me out? I do have the kernal reports...

https://discussions.apple.com/message/23682907#23682907

Pleas help me!

- Alexander

Anyway, I sent the iMac for repair, and they replaced the logic board.

Unfortunately this is a hardware issue.

After they replaced the logic board, everything works good - no more crashes.

But OMG.

After 1 month, the problem came back..

I am having exactly the same problem. First repair, I suggested it could be the power supply, they changed the logic board. Just as with Samwize, the problem came back, luckily with the 3 months of warranty. Next repair, they did not fix anything, just wiped the machine and did a clean install claiming it is a software error.

This seems to be clearly a hard ware problem (you can't restart it unless you unplugged the computer for a while, the longer you computer stays unplugged, the longer it will run), yet it seems to occure mainly while using FCP X.

I gave my daughter the task to beta test the problem while I am work, now she is allowed to play Sims on this computer, strangely she does not encounter the crashes. Then I had to export a few stills from some movies, to use as thumbs on YouTube, crashed on me twice while doing that.

Any more insights or ideas? Did anybody solve this? Is this somehow tied with FCP X, or was it just the statistical probablity as I usually use it most. Did not crash on me while typing this

I keep working on my theory that somehow FCP might cause the system shutdown...

here the logs of the last 2 shutdowns, the firstline is spammed maybe 50 times, then the next 4 lines and power goes off...

5/12/14 7:20:58.216 PM WindowServer[84]: CGXSetWindowListAlpha: Operation on a window 0xb8 requiring rights kCGSWindowRightPresenter by caller Final Cut Pro

5/12/14 7:22:36.241 PM Final Cut Pro[525]: AVF error: Perf capability check failed: 0xe00002be

5/12/14 7:22:36.241 PM Final Cut Pro[525]: AVF error: Branch_QT0::pushBits, Context Creation Failed.

5/12/14 7:22:36.328 PM Final Cut Pro[525]: AVF error: Perf capability check failed: 0xe00002be

5/12/14 7:22:36.328 PM Final Cut Pro[525]: AVF error: Branch_QT0::pushBits, Context Creation Failed.

5/12/14 8:19:30.662 PM Final Cut Pro[437]: error: FigTimeGetSampleNumber t.timescale == 0 || Non-Numeric(t) || Invalid(t) || sampleDuration.timescale == 0 || sampleDuration.value == 0 (t=-inf, sd=0.033333(100/3000))

5/12/14 8:19:30.848 PM Final Cut Pro[437]: AVF error: Perf capability check failed: 0xe00002be

5/12/14 8:19:30.848 PM Final Cut Pro[437]: AVF error: Branch_QT0::pushBits, Context Creation Failed.

5/12/14 8:19:31.508 PM Final Cut Pro[437]: AVF error: Perf capability check failed: 0xe00002be

5/12/14 8:19:31.508 PM Final Cut Pro[437]: AVF error: Branch_QT0::pushBits, Context Creation Failed.

I'm having the same problem. Sometimes the computer works 1 day or 1 hour and than shuts down like it has no electricity. It then don't startup anymore until I unplug the powercord and replug. I tried another powercord. Tried in another room. Nothing works. I will try to test the RAM but it worked 2 years until now. I didn't take the AppleCare though it will be a costly repair if its the powerunit or the motherboard.

If someone has the answer to this problem could you please send it?

Thanks

It happens to me too. I took it TWICE to the Genius bar and no action was taken as the hardware tests were OK so they pointed to one of the external devices connected. They refused to do anything else.

I have several USB disks, a hub and one Thunderbolt SSD disk wwhere the OS X (Yosemite) exists.

I started to work without them but still shuts down. Sometimes once a day. Sometimes three times a day.

The thing is that many of report that after logic board and PMU is replaced, this still happens so I don't know what else it could be.

Regards,