27-inch / 27" iMac Random Shut down

SPECS:____________________________________________________________________________
• 27" 2.8 GHz Intel Core i7 / 8gig / 1TB
• OS 10.6.3 (about to update to 10.6.4)
• All firmware updates have been applied according to software update
• 3 external drives: 1-320 gig 800fw / 1-TB USB 2.0 / 1-500gig USB 2.0

INFORMATION:____________________________________________________________________

I've been running with this configuration ( 3 extra drives) since approximately December with no issues. Out of the blue... only running Aperture and Safari - my iMac JUST SHUTS off- WITHOUTwarning. It acted as though I was running a MacBook and the battery going dead/asleep. That's how random and sudden it shut down - NO WARNING. I did have the iMac asleep for about three hours before coming back to it to start working again when it shut down, but it should have even been cool.

I only started reading around on the web to see of other incidents after this random shut down this evening, but I can't find anything specific. I've found A LOT of similar things - all seemingly related to "HEAT."

And heat seems to be a certain issue recently - in the last day or two. Today I noticed my top back side to be hot, which isn't uncommon, however, it became so hot I really wasn't able to keep my hand on the top back. I've also noticed A LOT of spinning beach balls, and lots of processor delay! Heat??

There are NO energy saver pref's set to automatically shut it down. The power was and is firmly set. There are no network settings, nor access to the iMac to have it shut down. It is not shared with anyone on the network.

SUMMARY:___________________________________________________________________________

• Today, I grabbed a couple temp / monitor widgets and am trying to watch the data. All components seem to be at/around/below 140 degrees F with ambient air at 77 degrees. I don't know numbers, but that all seems reasonable.
• Going to update to OS 10.6.4 (doubt that's it!!)
• I'm going to run the hardware test from my disc to see if ANYTHING. 8-p
• AND... I'm going to call Apple to set up a case. It's still full under warranty, and I have 2 more years of AppleCare on it. But there's been too many things pointing to hardware to call this a software issue.

I've dodged all the display issues with my iMac, but now.. I'm a bit hacked knowing how much I spent on this thing, with the initial DELAYS I went through, ordering it before it had even been released!

?? QUESTION ??_____________________________________________________________________

So, has anyone else been having this issue, heard of a solution, seen anything on Apple's website of known issues ??

Barry
( Grumbling bout my Mac)

Which one of twelve??, Mac OS X (10.5.6), ever hear Newton?!! ;-) One of those, too!

Posted on Jun 22, 2010 8:59 PM

534 replies

Feb 26, 2011 10:10 AM in response to Anthony Godin

I should have edited my response above. The ram modules are 2 x 4GB (Mushkin sku 976647A) , not 2 x 8GB. I installed two of these kits for 16GB of ram in total.

Tank9

Level 1

0 points

Feb 26, 2011 12:52 PM in response to peterwillem

I am using 16gb. In the review I did mention that it did shut down my computer. It happens randomly. It happened when I popped out a 1080p window on YouTube. It is certain that my computer isn't using all of the 16gb System Memory in my Activity Monitor. I tested my 16gb ram with memtest 4.22 in single user mode for hours and hours (I may as well check each stick at a time, but I shouldn't have to!), and there are no errors. I have come to no conclusions as to why the computer randomly shuts down.

Let me make it clear of what I am trying to say in the review. Even though my computer crashes every once in a while, I am quite happy it is not crashing every hour.

Mushkin is high quality. They make good ram to Apple specifications. I choose it over Corsair. Why is it not quite working 100% I don't know.

Satoneko

Level 1

15 points

Feb 26, 2011 2:26 PM in response to Tank9

@Tank9

If you don't mind that your computer is crashing once in a while, that's your preference. For me, a computer shutting down randomly any time is unacceptable. It probably hurts the hard disk, corrupts files, and messes up directories. I suggest you do disk check and repair permissions when the crash happen.

Tank9

Level 1

0 points

Feb 26, 2011 11:10 PM in response to Satoneko

Is your computer still randomly shutting down on Samsung Memory?

Feb 27, 2011 2:12 AM in response to Anthony Godin

@Anthony Godin

Reading Tank9 posts it seems that he does have the random shutdowns with the Mushkin 976647A ram.
How about you, do you have these shutdowns?

peterwillem

Feb 27, 2011 2:22 AM in response to Tank9

@Tank9

I agree with Satoneko it is unwise to let these shutdowns happen. My own and a lot of others experience is that once they start they will occur more frequently.
Imagine your iMac is installing new software or software updates and it suddenly decides to shut down.
You will have a lot of mixed up software/files etc. Likely you end up having to do a complete new system install. Not to mention the possible loss of data.
So my advise is to reduce the 16 G ram to 12, that is likely to help.

peterwillem

Message was edited by: peterwillem

Satoneko

Level 1

15 points

Feb 27, 2011 5:00 AM in response to Tank9

@Tank9

No shutdowns at all with the Samsung RAMs. I've switched the RAMS in December. Before that, I had about two to three shutdowns a week. Earlier this month, I added another 8GB, so now I have total 16GB of Samsung. No shutdown, slow down, beach ball, or freeze. I use Photoshop and Aperture which is a memory hog, and I also use Power Point which also eats memories. Fortunately, I live in the part of the world where Samsung RAM can be bought relatively inexpensively.

Tank9

Level 1

0 points

Feb 27, 2011 11:42 AM in response to Satoneko

Thanks Satoneko. I will speak with Mushkin. And report back here.

Tank9

Level 1

0 points

Feb 27, 2011 12:16 PM in response to peterwillem

Thanks peterwillem. If the problem didn't varied from one iMac with 16gb ram to the next we would all know what the solution is. I want to try 16gb Samsung ram as seen here.

http://www.newegg.com/Product/Product.aspx?Item=N82E16820147068

That is if the RMA get's through from Mushkin.

toolman

Level 2

381 points

Feb 28, 2011 2:00 PM in response to Satoneko

well my shut down issues persist. 12gb of samsung ram did nothing to help my shut down issue. After trying a long list of possible cures from the Apple tech's on the phone (6-8 different calls) it went in to the shop today to see if they can figure it out. Mine almost acts like it is usb related. I have had several times after a restart where all I get is a blank blue screen. I unplug a couple of the usb cords I have plugged in and instantly have my desktop back. It doesn't matter which usb items I unplug or in what order, it seems to be the second or third item unplugged will bring my desktop back but it's not every time that this happens. Most of the time it will restart just fine.

JANSJE

Level 1

0 points

Mar 2, 2011 8:25 AM in response to Berry with an A

I had the same trouble, unexpected shut downs, but iCentre, Uitgeest, The Netherlands, found that the display of my brand new iMac 27" i5 was the cause. I just have him back after 5 weeks ⚠ and hope the new display is really better? I have 16 MB RAM KINGSTON. That could not be the cause, they said to me.

JANSJE (3th of March 2011)

Tank9

Level 1

0 points

Mar 2, 2011 12:44 PM in response to Berry with an A

Mushkin Ram Update: RMA went through with Mushkin. They said they are replacing their chips on their ram soon. I will have to pay to ship the ram back to them after they notify me the new ram is available.

Tank9

Level 1

0 points

Mar 2, 2011 8:30 PM in response to peterwillem

I am forced to reduce the ram to 12gb. The crashes are occurring frequently within an hour. Four times so far. Thanks for your help.

Mar 3, 2011 12:57 AM in response to JANSJE

@ jansje

If you read thru all the posts/threads about this issue you will notice that world wide the Apple Cares,repair shops and the like have done everything from new logicboards , PSU even brand new iMacs to fix the problem. So far none of it helped solving the problem, so I am curious if changing the display will solve it. I have my doubts but you never know.
Keep us informed about it. BTW reducing the gigs to 12 will probably help.

peterwillem.

JANSJE

Level 1

0 points

Mar 3, 2011 5:08 AM in response to peterwillem

The engineer of iCentre tested my iMac for more than 3 weeks. He found out that it was the video card. They placed a new video card, but that was not the cause, so he replaced my own videocard. After that he found out that it was the display. A new display took another week. I was desperate! This is the second day after the repair and I try to work with all the programs. I shall keep you informed if this diagnosis is right. I asked them – when I brought this iMac 27" to iCentre – that I found out on Apple Discussions that my 16 MB RAM is the cause. He said: You must not believe everything they say on internet. It is bad that Apple does not give any response...
By the way: two months ago my MacBook Pro – nearly 3 years – stayed black: it was the videocard! After repair under guarantee they replaced a refurbished video card (this is the policy of Apple). After 3 weeks I got the same problem, so iCentre replaced a new second hand video card... I love my macs, but I don't love Apple anymore!

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27-inch / 27" iMac Random Shut down