I have had the same problem with my screen turning off randomly, the only difference is that I have to do a hard rest to have the screen turn back on.
I HATE to do this (had to do it 3 times.
When this does happen I'm not doing anything that is demanding at all, listening to music and surfing the internet.
I have the latest firmware for the 27"...before the updated I had no issuses.
Temperatures do concern me, although it appears that all temps are with in safe thresholds.
If temp is not responsible what is? My iMac is 6 months old!!!
I am still having the same problem. My iMac has been in for repair twice & had a new logic board but when it came home the screen turned off again within 2 days. it's very frustrating as Apple don't know what's wrong & it has to go for repair again. This time I am to try a new mouse & keyboard to see if that solves the problem. Has anyone else got a solution.
I have this same problem, as of today. As others indicated, it appears the monitor goes to sleep even though I am using it.
27" iMac purchased in November 2009. No problems of any sort until now.
I had not yet installed the display firmware updates, as there was no problem and some had reported installing them on perfectly functioning systems could cause the problems to appear. I did install them earlier today however, once the problem appeared. The display has shutoff once since the updates were applied.
The problem has so far only appeared while OSX is running. I have 64 bit Windows 7 Ultimate in Boot Camp which I am typing on now, which is not experiencing the issue at least not yet. I had been using Windows 7 more than usual the last few days, including playing some 3D games. I had booted into Windows directly which I had rarely done before, and had hooked up a USB mouse. So it may be related to using Windows recently, but at least Windows isn't shutting the monitor off. The display is significantly brighter in Windows as well, even at the lowest setting.
Not sure what to do next, other than monitor this thread, and get AppleCare extended coverage paid for soon.
Update: The monitor (27" iMac) will now shut off within 10 minutes of booting into OSX. Sometimes it flickers on and off once before shutting off for good. The only way to get the monitor to come back on (that I know of) is to hold down the power button until the entire system shuts off, then power back on as usual. I have not yet tried to VNC into the system once the monitor shuts off to see if the CPU/network etc is still active, but as the lights to external USB devices remain on, I suspect it is only the monitor that is failing.
Thankfully the 64 bit Windows 7 Ultimate installed on Boot Camp will still boot, and the monitor doesn't ever die as it does in OSX, but I have a couple of issues there as well. First is whenever the monitor has failed in OSX, when I then boot into Windows 7 it goes into a CHKDSK process. It had never done this before, and now only does it if the monitor failed in OSX. The other problem is I don't see the option to set booting into Windows as the default, so I have to hold down the option key each time I'm booting to select Windows.
Based on these results it appears to be a software problem within OSX, as it will fail within 10 minutes of use, but Windows hasn't failed yet after several hours of use. As I still want OSX to function on here I guess I'll have to ship it off for repairs, or drive to the closest Apple store 3 hours away, unless someone else has any suggestions. Thanks.
i27, pretty much happened the same way. I didn't touch the firmware updates until after all this started. But question for you... Did this start after you updated the graphic drivers? It did with me.
I had an extra external, so I installed the OS and ran all updates except the drivers update. I had been running my machine off the external now for 48 hours without issue. I switched back to my internal and it happened twice after an hour. I am guessing something changed somewhere and when I installed the new system in the drive it retained that setting (I had done an archive & install.)
Tomorrow I'm going back to working off my external for a bit to confirm all is ok and if so I will wipe the internal drive, install a new system and pull my folders out of my Time Machine drive. Hope it does the trick.
/nick asked "Did this start after you updated the graphic drivers? It did with me."
Not that I know of. On the OSX side, in Software Update I had been unchecking any display driver updates, while letting other updatess be installed. For example, the last thing I had installed was the iTunes update which included an upgrade for iPhone, which I did early in the week, but when I let that install I had manualy unchecked the display driver updates. From what I recall, there were 3 firmware or driver updates, and one other large upgrade for imaging. Is there a log that you know of that would tell exactly what was installed and when?
On Windows 7/64 side, I have left the original video driver that was first installed on there, and had not installed the Boot Camp 3.1 upgrade either. The reason being, before I activated my Windows license, I ran several tests of various configurations, and whenever you install BC 3.1 it puts on a 16 bit driver that has to be manually replaced, and even then the quality doesn't seem to be good. I've considered installing BC 3.1 now to see if it fixes the problem in OSX, but since that is a Windows upgrade, and the problem is so far contained in OSX, I really don't want to risk messing up my Windows now.
Yes there is a way to check what updates have been installed. Within your System Preferences, under the System subheading, you'll see a Software Update button. Once selected the "Scheduled Check" pane will show. There's a tab for "Installed Software" which will list what was installed via the Software Update and the date it was installed...
/nick said "I had an extra external, so I installed the OS and ran all updates except the drivers update. I had been running my machine off the external now for 48 hours without issue. I switched back to my internal and it happened twice after an hour."
This is further evidence the problem seems to be software. I can boot up and run Windows for hours, but as soon as I boot OSX now the screen shuts off within 60 seconds. What's really interesting is, if I boot OSX and it fails, then when I boot Windows the system goes into CHKDSK, a Windows utility that feels something improper happened to the Windows disk. When I just reboot Windows and go back into Windows, it doesn't happen. I found an article where you can hold down the Control key when selecting to boot Windows, and so far that is working. I don't really plan to even try OSX again unless someone here thinks they know what the problem is, or I finally decide to call Apple.
/nick said "Yes there is a way to check what updates have been installed."
Great, what is the name of that "graphic driver" you were asking about and I can tell you if/when it was installed, if I can keep OSX up long enough without the monitor crashing. If monitor won't stay up I'll try to VNC into it. Thanks.
Thanks, it shows the following were all installed yesterday after the problem appeared:
27-inch iMac SMC Firmware Update 1.0
27-inch iMac Display Update 1.0
27-inch iMac Graphics Firmware Update 1.0
Snow Leapard Graphics Update 1.0
Then it shows the following was installed a second time this morning, after the screen died again and I ran Software Update again:
27-inch iMac Display Update 1.0
I had to reboot it twice just to write this down as the screen dies within 60 seconds now.