27' iMac (2011) Screen turns off

Thanks for keeping the discussion alive David. My video blackout issue continues and I've never, ever used Filevault encryption.

After living and coping and adapting to the issue for months now, I'm confident my video blackouts are correlated with heat. The warmer our ambient weather the worse the issue seems to become. The brighter the display the quicker the video blackout. We had a big cool down here in OK for the last couple of weeks and the issue became stable running the screen at 6 clicks above minimum brightness. But then it warmed back up a few days ago and high temps outside were in high 80's. Problem cropped up again. We do not heat/cool our home when the temps are not extreme so the inside temps raised and lowered with the ambient. I've taken to using a fan to blow across the heat vent of the machine hoping that this would help a bit. I believe it does. If it truly IS heat correlated then that could indicate a component failure or board-trace failure (due to expansion & contraction).

Thanks again, but encryption isn't the issue with mine.

Mark

Unfortunately looks like the problem has returned after a month, started again intermittently, zapping the pram kept it trouble free for a few days and now it happens daily a few times, even at startup so it's not a heat issue.

I just started having the symptoms described in this thread after having made no updates or hardware changes to my system in quite a while.

Mine is not (only) a backlight problem since there's no image visible through the "flashlight test". In dual display mode, items can still be dragged to and from the desktop on the blank screen as though it's still on.

One unique thing I've been experiencing that I haven't seen anyone else mention is the fact that in addition to the main display, my external display (a third party HDMI monitor via thunderbolt adapter) is also randomly turning on and off while I have it mirroring mode. I haven't seen it do that while it's in secondary display mode. Clue toward video card failure?

I cracked it open and reseated the data, power, backlight, and v-sync cables, which didn't make a difference. It seems to behave for a little while after a fresh boot, but it starts shutting off after a while.

Unfortunately no. Eventually the internal display went totally dead, though the external monitor continued working. I ended up parting out the computer and selling the display, logic board, and GPU as-is. Wish I could be more help.

I had the same problem with my mid 2011 iMac. I bet the cause is the LED inverter board, since the LCD itself is alive, just without the back light and if I plug in a secondary mini display port monitor it works. The problem goes worse with higher led illumination.

I just ordered another inverter board and as soon as I have news I'll post here.

Hello, have you blown the dust out lately? Let it cool for an hour & see if you can get these...

Get Temperature Monitor to see if it's heat related...

http://www.macupdate.com/info.php/id/12381/temperature-monitor

iStat Menus...

http://bjango.com/mac/istatmenus/

And/or iStat Pro...

http://www.islayer.com/apps/istatpro/

Please can you add a bit more description to your post about fixing this problem.

Dust? What dust and what are you proposing?

Your links, these take me to third party product home pages with no suggestion or mention of fixing an iMac screen that randomly turn off.

The iMac contineus to randomly turn off, this has only happened since upgrading to the latest version of Lion.

Thank you

Hello Ashadur: My 27" iMac (Mid-2011), Mt. Lion 10.8.1, just started with this same issue a few days ago (today is 4SEP12). Here are the particulars for others affected.

1- Video suddenly goes black. Computer is still functioning, apps all running; its just like I invoked "sleep", but I didn't and keyboard or mouse will not "wake".

2- A hard restart (using the power button) will bring video back, but sometimes it goes black before machine is completely booted.

3 - Found that reducing screen brightness to 3 or 4 clicks above minimum brightness is, at least, a work-around. With display brightness reduced the panel has never gone black! If I turn up the brighness to normal (about 3 clicks from maximum) the panel will go black ususally withing 45 seconds.

4 - Found another user with this same issue that discovered that the keystroke combination Shift-Control-Eject coupled with some keyboard activity sometimes brings the video back. I've also found this to be true, but it usually blacks out almost immediately again.

5 - My machine is 1 year and 4 months old, with no AppleCare extended warranty. I spoke with AppleCare and the tech was not aware of this issue. He said, that so far, it was not a reported "Engineering Issue". He also said that IF it became an Engineering Issue, that any machine would be repaired by Apple regardless of warranty coverage.

6 - My only recourse is to make an appointment at a Genius Bar (100+ mile trip!!) and have them try to diagnose. Of course, I'll be out the repair costs, which I will not be able to afford since those reporting this same issue on both Apple Discussions and on other Mac Forums have reported that panel/backlighting replacments have solved the issue. That is probably a super-costly repair.

7- So... I'm likely stuck with using this machine until it quits at a much reduced display brightness. 😟 This is the first Mac I've purchased without AppleCare and I'm a charter Mac user (Jan 1984!). I let the one-year anniversary slip by and forgot! AppleCare will be in the cart on every purchase from here on out! Live and learn!

Hey Mebyard,

I took mine to the genius bar last week. I am confident the genius knew what he was talking about as he pointed out that something was not working properly. Bottom line, recomendation is to back up and reinstall the operating system. I have not done it yet, but plan on doing it this week.

Good luck

I am in a similar position - my imac is just over 1 year old and I meant to purcchase the extended apple warrantly but it was past the date when I called in 😟 so I am stuck with no warranty. I also live over 160 miles from an apple store but I did make the trip last weekend to the genius bar. The fella at the store had never heard of the problem - surprising considering the number of posts on here about it - and he did a system reset and just two days later the screen black-outs have continued. I have no idea what the next step is.

Did the system reinstall work for you DavidNY63??

Any other suggestions out there?

not done it yet

Thanks DavidNY63. Please let us know if the reimage helps. I cannot reimage at this time because I am in the middle of some contract work. But after the jobs are finished I can and will if you find it cured your issue. I have been curious to read that this issue seems to have started with the introduction of Lion (Mac OS 10.7). I never had the issue appear until after installing Mt. Lion (10.8.1). Thank you for keeping us up to date.

Mark

Dear lewaseven, et. al.,

I have read several posts (different thread) on this same issue and it was solved with a panel/backlight kit replacement. That is very likely a $900+ repair! So that is not an option for me.

I suppose it is possible that the issue could be a mixture of hardware and software, i.e., updated drivers that are pushing the video card too hard too hard or something like that. But the bottom line is that those of us in the boat with no AppleCare are going to have to either settle with the workaround of running the monitor on a dim setting OR hope that someone finds a software workaround (such as a re-image, or a driver update, etc.).

Thanks for all on the thread for their input. DavidNY63... we will standby to hear the results of your reimage.

Regards,

Mark

Ponca City, OK USA

Hi DavidNYC63: DId you ever try the re-image?

Thanks,

Mark