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User profile for user: Celia78
Celia78 Author
User level: Level 1
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iMac keeps turning itself off - won't come back on again

I have an intel-based iMac that I've had for less that a year. Yesterday with no warning it turned itself off - the screen suddenly went black, as though someone had pulled the power cable out (which they hadn't, of course!) - and when I tried to turn it back on again it was unresponsive. I checked the electric sockets - they were fine.

Using my MacBook I went online and, following some advice I found there, reset the SMU. That seemed to work - the iMac started up again. But then twenty minutes later it 'died' for a second time. I left it for the afternoon, periodically seeing if I could turn it on using the power button. I couldn't. After about five hours I got it to start up again with no problems, long enough to run the Hardware Test. It found no problems. I restarted the computer - started up fine again. Then five minutes or so later died for a third time.

Following a suggestion in the manual, this morning I have reset the NVRAM. Once again, the iMac started up fine but died shortly afterwards.

Please, does anyone have any ideas? I haven't recently installed any new software or anything like that and I wasn't doing anything unusual when the problem first manifested. The cable is obviously OK, the wall sockets are fine. What else could it be?

iMac, Mac OS X (10.5.5)

Posted on Sep 30, 2008 2:35 AM

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18 replies
User profile for user: pogster
pogster
User level: Level 5
4,247 points

Sep 30, 2008 7:08 AM in response to Celia78

My first thought is it's a hardware problem maybe with the power supply. It could be a number of components. Is it overheating? Are the fans running normally? I'm not real familiar with the hardware test but from what I understand it only reads the machines current state rather than recording what it was doing when the machine shut down. It can be running normally and show no issues until a circuit opens due to whatever and quits after the test. How close are you to an Apple dealer? To have it die suddenly and not restart again doesn't sound like a software issue.
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User profile for user: Fortgal
Fortgal
User level: Level 1
0 points

Sep 30, 2008 4:02 PM in response to Celia78

Dear Celia78,
I have the exact same problem with my 4-month old machine, and have done all the same trouble shooting. My machine also goes into a restart loop: black screen, white screen, apple... then black screen and never starts up. The only thing I can do is unplug completely, wait awhile then reconnect all and start up with power button. I'm packing up the machine and headed to the Apple Store Genius Bar tomorrow eve., but my suspicion is that is is a power management problem or heat sensor problem in the system.

Any others having the same issues? Thank you.
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User profile for user: Fortgal
Fortgal
User level: Level 1
0 points

Sep 30, 2008 5:06 PM in response to pogster

Yes, I will let the group know the outcome. The problem began 10 days ago and has happened consistently. However, as the machine will be transported to the Apple Store completely powered down, I wonder if the problem will manifest itself to the technician. But I have my notes, an Apple Care case number, a 3-year Apple Care plan, and I will print out this discussion. Too bad I dream about this at night.
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User profile for user: abbysmom
abbysmom
User level: Level 1
8 points

Oct 12, 2008 6:15 AM in response to Fortgal

YUP! Mine is doing the same. Seems like the same timeframe as mine was turning itself off...took it in, they couldn't find a problem and it is still happening. After awhile I can turn it back on...and then I brace myself for the next time it will turn off out of the blue...

I am ready to toss this one and get a new one. It's an early 2006 iMac. If anyone has found the problem, please let us all know, and thanks in advance!
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User profile for user: Fortgal
Fortgal
User level: Level 1
0 points

Oct 12, 2008 10:28 AM in response to abbysmom

Cannot comment about the virus possibility, but I agree this problem is so weird. Another funky symptom my machine has is that if I shut down from the Apple menu, the machine will try to restart itself within about 2 minutes. However, it won't restart, and goes into a chime, black screen, white screen, loop without going to the log-in screen. I have to unplug the power cord to get it going again. And I get a warning box that a USB port is drawing too much power, when the only thing plugged in is the keyboard. Due to a schedule change I haven't gotten the machine in for service, but fear the same result you experienced: no evidence of a problem.

Grateful for any other suggestions from the community.
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User profile for user: augiecrazy8
augiecrazy8
User level: Level 1
8 points

Oct 12, 2008 7:34 PM in response to Fortgal

I just responded to another post that was having this same issue. Add me to the list. I've had my power supply replaced, I was told these models overheat because all of the hardware is stored in such a small space. I'm still having the same issues. It seems to be a fairly common issue... does Apple plan to address this or help in any other way than simply saying "reboot, press this and this and this, now it will work, replace the power supply, AGAIN"?
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User profile for user: Haziee
Haziee
User level: Level 1
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Oct 13, 2008 4:31 AM in response to augiecrazy8

I have an intel based mac which I bought in April, which has had similar problems, most notably a failure to power up at all, and have had the power supply replaced when it went in for repair in August. It started with a similar problem last week, and applecare arranged to have it picked up for repair again last thursday, spoke to the repair chap today, and he has it on test but of course it's working perfectly well for him, however, he said he would replace the logic board if nothing showed up as there is an 'interruption' somewhere. Having posted a query myself last week re: non start up I have been watching the discussion boards and there seem to be quite a few very similar problems with the intel imacs, which seems to suggest some kind of design fault?
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User profile for user: CoconutQueen
CoconutQueen
User level: Level 1
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Oct 13, 2008 6:09 PM in response to Haziee

I've had my imac for about 6 months and I'm a newbie. It shuts off in the middle of whatever I'm doing and sometimes won't come back on. I haven't tried all the stuff some of these folks have tried because I don't know how, but I'm getting very agitated at spending so much money on such a nice computer to have it do this to me. And of course, when I loose power on it then I have to go thru all the Keychain stuff again...and again...and again.....Any suggestions would be appreciated!!
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User profile for user: LynchMOB1
LynchMOB1
User level: Level 1
0 points

Oct 22, 2008 7:18 AM in response to Haziee

My Imac was bought in April as well... It has started shutting down randomly. So far it is only about once a month or so.... But it sounds like it will get worse. Apple wants me to take it in for repair. The closest Apple Store is almost 100mi away. The local authorized apple service shop is a HACK. I dont think they even have a certified tech on the payroll.
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User profile for user: Celia78
Celia78 Author
User level: Level 1
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Oct 23, 2008 2:34 AM in response to LynchMOB1

Thanks everyone for your replies to my question. Just to update: I took my iMac to the Apple Store where the power supply has been replaced. So far (two days and counting...) it's working perfectly. Though, as someone else here noted, with so many of them experiencing similar problems it does look like it might be a design fault... and perhaps one that might recur? Good luck anyone with similar problems anyway.
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User profile for user: alweston
alweston
User level: Level 1
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Nov 4, 2008 6:17 PM in response to Celia78

My 14-month old Intel iMac has the same problem, and has been in for repairs 4 times. So far they have replaced the power supply, video card, sound card and motherboard. Things were fine for a month or so, but now it's doing it again. The machine has spent over a month in the shop, and it seems as if Apple doesn't have a clue what the problem is. I'm sorry to hear there are others having similar issues. I'd sure love to know what the problem is.
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iMac keeps turning itself off - won't come back on again

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