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27" Core i7 iMac blacks out then restarts itself for no reason...

I've had this new iMac since late November and everything has been perfect. However it has twice now just randomly blacked out the screen and then the computer restarted itself. What could do this? I was just reading a webpage each time. I have never seen a computer do this before... The back of the iMac does not feel hot each time it restarts. I have added for 4GB of RAM to make it 8GB, but would that be an issue. This is very troubling...

Does anyone else have this problem? Or any suggestions?

iMac 2.8ghz Quad, Mac OS X (10.6.2)

Posted on Dec 7, 2009 4:23 PM

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81 replies

Dec 7, 2009 4:46 PM in response to Chris Aynesworth

Since it is related to power, I would first reset PRAM

http://support.apple.com/kb/HT1379

and then reset SMC (power management)

http://support.apple.com/kb/HT1543

which is basically disconnecting ALL cables and power, then reconnecting using a precise procedure. When you reconnect the power cord, if you have been using a crowded or old power strip (surge suppressor), try connecting it directly to the wall outlet, at least initially. Power it up with nothing connected, except the power cord. Then add just keyboard/mouse. This does not seem like a frequent problem, so I realize it may be difficult to know if there is still a problem or not, but if possible, use it that way long enough so that you are satisfied. If all seems well, add back your peripheral devices. If the problem recurs after doing so, you may want to see if one of the devices is causing this problem, through a process of elimination. USB and FireWire devices can become faulty or otherwise interfere with the iMac's sleep, wake, shutdown, and startup.

If the problem still recurs after the SMC reset with only your keyboard/mouse connected, I would have it looked at by a technician at an Apple Store or Apple-certified repair shop.

Dec 7, 2009 4:53 PM in response to Kenichi Watanabe

Thank you so much for replying. To add to this, there is indeed an older Kensington USB hub attached, as well as a riser with an integrated USB hub as well. So I HOPE it is just this. My keyboard is attached to the riser/USB hub so maybe it is finicky with these devices? I also have attached a firewire 800 hard drive from Western Digital and a Wacom tablet. I'll go through these fixes you mention and hope it is OK.

If anyone has any sort of experience with this and fixed it, let me know!

Dec 7, 2009 5:02 PM in response to Chris Aynesworth

Chris Aynesworth wrote:
I've had this new iMac since late November and everything has been perfect. However it has twice now just randomly blacked out the screen and then the computer restarted itself. What could do this? I was just reading a webpage each time. I have never seen a computer do this before... The back of the iMac does not feel hot each time it restarts. I have added for 4GB of RAM to make it 8GB, but would that be an issue. This is very troubling...

Does anyone else have this problem? Or any suggestions?


I had the same issue. As suggested reset PRAM. Use a wired keyboard otherwise it may not reset PRAM properly.

User uploaded file

Dec 13, 2009 3:06 PM in response to Ravenwood61

I have a similar issue with the black out and restarts. It started in imovie and then happened in lightroom and then i was able to replicate the issue over and over again in Final Cut Pro. I started pulling ram (8 gigs). I ran memtest and rember both reported no errors. Oddly enough I tried every combination of ram and the problem only happens when I have all 8 gigs installed. It works fine with 6, 4, 2 gigs. I even tested each chip individually with no errors. I zapped PRAM and reset the smc. The only thing that works for me is to pull 1 ram chip (6gig of RAM). The additional Ram I purchased is Crucial. I am thinking of buying another 2 chips to see if I can figure out which set of RAM is faulty. This problem really has me baffled.

Dec 14, 2009 4:35 AM in response to Chris Aynesworth

Had the same problem-I had added 2- 2gig sticks of Crucial memory purchased from Amazon. It wouldn't wake from sleep. I unplugged it and then replugged it into the wall and then it was fine-going on 3 days. Also removed a thumb drive. I still have an Iomega backup drive attached.
Two other things I noted. On start, it is on the white screen for over a minute. When adding the ram, it was hard inserting it into the upper right slot (with the screen positioned down).
Hope this helps get to the cause of the problem,
Joel

Dec 14, 2009 11:29 AM in response to Ravenwood61

Hey thanks for sharing your issues on this thread. I've zapped the PRAM and also I removed a new USB 2.0 hub that came with this Slimkey V2 Stand I had bought for the new iMac. So far I have NOT had the weird black out/restart issue in at least a week (and this is a graphics/web production machine). I have 8GB of RAM - a 4GB kit I bought at OWC (www.macsales.com). The fact that two people here may have had issues with Crucial RAM may or may not explain how I've not seen the restarts. I haven't pushed my computer too hard since the last restart.

Which leads me to the point of asking: how can I test my RAM to see if it is a contributing culprit? I have loaded in 30 programs a while back to "fill it up" and there wasn't a restart issue...

I can also say though that I had trouble adding the RAM I bought. I had to push it in pretty hard and I remember being a little worried about having to use so much force. So I pulled out the Apple RAM and reinserted it, noting how hard I had to push to seat it and then tried it with the OWC RAM in the remaining slots. I noticed that the slot itself for some reason is a little finicky with how you start the insertion. Since the computer has to lay down, inserting it at a sideways angle presented a problem I guess.

Please let us know how things are going with the iMac - if I find any other problems I'll post here again. I haven't had the flickering display or overheating issues that have been going around the Mac press sites, so hopefully things have settled with my computer!

Dec 14, 2009 2:31 PM in response to Chris Aynesworth

Apple, Crucial, OWC, and other vendors probably buy RAM modules from the same suppliers in Asia, so as long as you bought the correct specification (pretty hard to buy the wrong ones on OWC's web site), it should be fine. If you have the RAM out again, you may want to double-check the label (on the RAM module) to make sure they sent you the correct ones; if it has two labels, check the manufacturer's label (if possible), not the vendor's label.

Dec 15, 2009 3:45 AM in response to jaegersilver

I bought CT2KIT25664BC1067 from Amazon which I verified with Crucial Customer Support was an exact duplicate of CT1115264. To quote Crucial's Support: "When you order by advanced search or by motherboard/system information online, you are shown the “external” part number CT1115264. The part number that you see on your module is the actual module base part number CT2KIT25664BC1067. If you order by advanced search or motherboard/system information, the external part number is included in the packing list with your memory module. The parts are exactly the same. I apologize for any confusion."

27" Core i7 iMac blacks out then restarts itself for no reason...

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