iMac screen goes black, but system runs fine in background

Hi Michael, i've been following this thread for many months since i've been dealing with the same issues for as long.
I'm replying to you because i've been tempted to do the same: take my machine in to have the video card checked out.

I use Mid-2011 27" iMac for a second display and it suffers from the blackout screen thing. Since i use it as my second monitor, its not 'critical' per se - but it severely hinders my workflow. ... a few months back the HD started making a clicking sound, so i took it in to the genius bar to diagnose and my hard drive had failed. ...and even though i brought up the screen issues, his diagnostic test didn't show anything.

So now after investing in a new hard-drive i've found myself doubled-down on this machine. Though i'm tempted to bail on it, and just buy a different used one (i'm on a budget & its only used for a second display) if the cost to replace the video card is above $600.

Please do follow up on this thread after your appointment and let us know what transcends. Good Luck, and Thanks!

Hi Folks

I've reported on this same issue back in the fall of 2016 on my 2011 27" and also assumed it was software related as it was intermittent and a reboot or zapping the pram quite often solved the problem. When that failed to work an initial visit to an Apple repair depot oddly showed no apparent problems on the bench...of coarse : ( ... but the issue continued shortly after and was alleviated by having the brightness set to full.

It has been fine since December but recently the screen did not come on at all and the Imac gave one chime at start-up and shut down.

Thought it may be the power supply but all indicator lights showed it was fine and disconnecting the display the Imac booted without problem so a return to the Apple service center had them swap out from a working Imac, the display (mine was replaced under warranty in 2013) and the video card ... problem persisted, the tech finally did an exchange of the backlight which solved the problem so a new one was ordered in and my Imac has been working trouble free without any issues for the last few weeks, Cost was $180 Canadian plus install.

Hope this helps but may not not be the solution for all.

I've been having this issue for well over a year now and have tried just about everything anyone has suggested, except for spending money on hardware (I just can't justify throwing good money after bad).

The Ctrl-Shift-Eject [pause-2-secs] Shift-Key wakeup method always works for me.

I had a bout of about 10 blanks in a row just before starting this reply - soo frustrating! I turned off the auto-brightness adjustment, which seemed to work... but alas - it just blanked again while I'm typing this.

I noticed that my keyboard brightness controls also stopped working there for a few minutes (volume controls still worked fine). It's sorted itself out now. I'm not sure what that was about - it could be related? Who knows...

Could this just be an OS bug? One which crept into the OS a few years ago and is only prominent on non-latest-gen hardware? Would this still happen if we were running the OS version that originally came with the machine? I rebuilt the machine from scratch last xmas, to no avail, but I reinstalled the current macOS at the time...

I have a 27" iMac (mid 2011). Can't remember what OS version it came with at the time. Is anyone still running the original OS on their 6 year old iMac, though? If I put on my cynical hat I'd say this issue is known to Apple and they have 2 options. Option 1, spend debugging/development resources on finding this *nasty* bug in macOS (and probably earlier versions) to make our ageing iMacs perfect again OR - Option 2, get us to buy the new iMac (when the old one is still perfectly up to the task).

PS: Take note Apple - this has been a 31-screen-blank reply for me - Oops, make that 32 :-)

Hi croozey,

My 27" is a mid 2010 if that's any help and came with Snow Leopard. Not sure how long it was before I upgraded to the next OS, but I do know it's only been since the last 2 upgrades I've had the issue. Yosemite seemed fine but my blank-outs began well into El Capitan, so I'm inclined to think it was an update applied to El Capitan.

Thank you SO MUCH for the Ctrl-Shift-Eject [pause-2-secs] tip. Man, my biggest frustration has been waiting for the "sleep" to kick in so I could wake it up again. There's only so much stuff you can do on a smart phone.

I called an authorised Apple Service Centre here in New Zealand and he reckoned it was either a Graphic Adaptor issue or more likely an LCD screen issue. Biggest problem with that, he said, is there aren't parts around any more and I'd be unlikely to find a screen. My only remaining option? Replacement! Not entirely convinced about that but it will depend how much the frustration levels escalate.

I struggled for ages trying to work out how to avoid this nightmare. After I got blacked out playing on a final table in a poker tournament which cost me the equivalent of £1000 I decided to buy and connect to the iMac a cheap monitor for about £50 and put my £1800 iMac dream machine under the table where it languished contently serving out the remainder of its life. I virtually gave it away as I was so disgusted with it. I will never ever buy an iMac again

I have the whole suite: iMac, iPhone, iPad, MacBook Pro & Apple Watch and I do love how well they all work together.

I just cannot bear the thought of contributing this ageing but still near-perfect iMac to land-fill on the back of just this issue, especially since it could turn out to be a software-only issue. But it has now persisted for well over 12 months and it is slowly sapping my trust in Apple's ability or willingness to deliver products that last longer, in favour of the next sale.

We pay a premium for quality products which are expected to last longer. In this throw-away society, if I cannot expect more than just the warranty years, why continue to pay a premium?

I bit the bullet and did a complete reinstall of the os now 6 weeks in and not a hiccup. I knew it had to be software related because of the following.

1. Even with a black screen the mac still operated in the background.

2. Couldn't be the video card if the mac could run a second monitor.

3. Other weird little things would also happen,

a, like I could log back in even a day later without putting my password in.

b, extra windows I'd created would disappear.

c, I run windows using parallels it would never black out in full-screen mode only in co-exist.

d. I set up windows in a dual boot mode and if it backed out when using the mac and kept blacking out I switched to windows and had no blackout problem.

The other thing that convinced me it was not the screen or the video card was the fact that when it initially started it was ok until after the apple timer finished. That's when the operating system kicks in in the initial boot-up it's not using the OS. and if you can see the apple then it can't be the screen or video card.

It's a pain in the arse but downloading the os and doing a completely clean install has so far seemed to have fixed the problem. My iMac is 2009 27" which I have upgraded with a 1TB SSD and added 32meg memory I know the specs say max of 16 mb but it can handle 32.

Hope that can be of some help

Hi gomoweb,

Can you please let us know if you experience an issue going forward? I also upgraded to the latest OS, but not a clean install as you've done, and mine went fine for about 6 weeks and then the blank-outs returned.

Sure no problem. I will mention that I am a heavy user I work for my self in the video and audio restoration area as well as website design so my mac can be working 14 hours a day also if I'm doing a big video job I will let it render overnight so it's not unusual for it to be running for a 48 hour period. So my six weeks is probably a normal users 12 weeks.

Sorry it took so long to respond. I forgot my promise. I took my mid 2010 iMac 27" to Apple Store; they ran diagnosis tests over 2 days and said it was a power supply issue. It cost $152.08 including $79 labor, which is cheaper than a new display or a video card. It has been working fine with no black screen (although I have to set brightness much higher compared to before). Also the fan doesn't run on and on, making a racket anymore.

But today, two weeks since repair, it went black twice. It comes back right away with the Control + Shift + Eject buttons and then I hit any key to wake up.

I'm hoping Apple releases new new 27" iMacs in the fall. 6-1/2 years is the longest I've ever kept a Mac.

Here's an update on my problem with 27" iMac (mid 2010). When I went in to Apple for my appointment the tech guy said it was a mistake to replace power supply and they wanted to replace video card. It worked with an external monitor for about a week, so I could take it in on June 9. They fixed over the weekend. Just picked up today at 5:00pm; they deducted cost of first repair from this total. Now I've spent $305.

I brought it home, plugged it in and it only ran about 15 minutes before the screen went dark again. Apple covers repairs for 90 days, but they are going to send me to an independent service provider because it's so old.

I'm guessing you expected this huh?

I get the impression most techs don't even take in, or believe, the scenario we present to them. The first thing they come up with is heat & fans even though the description of the fault clearly suggests heat is not an issue. Then it's graphics adaptor even though it works fine on another screen. I'm thinking when you finally get them on the right track they don't have a clue what's wrong or what to do about it so the computer suddenly becomes too old. I paid too much for this thing to accept that. 😠

Switched back to Snow Leopard = no more black screen. Dollars to donuts that it's software related.

Disenfranchised with Apple as of lately. Even our new iMac with Sierra is sluggish and my brand new iPod Touch cracked at only 3 mos - $129 fix. Yet I still have my original iPod Touch and iPad first gen (and they still run like champs).

They just don't make em like they used to so looks like I'm leaving the Church of Apple. :( bummer

I've also this problem. Since some months ago, the screen of my iMac 27" Mid 2010 started to go black (off) randomly. I know the system is running without problems because I can put my computer in sleep mode (control+shift+eject), and after press a key to awake the computer, the image comes again always. After doing this, sometimes it remains on for hours, sometimes just for few seconds.

I can also work perfectly with another display attached, when the iMac screen goes black, the second display remains on and working. So, I can absolutely discard a graphic related problem.

I don't think it's software related either... because I've tried to start the computer with the Recovery partition, to reinstall the latest Sierra version several times (with the COMBO Update) and always I had the same problem. I've not tried to restore an old version of macOS, but I think it's not necessary... it should work fine with Sierra without problem.

One more thing... and this is curious: you can try to use the flash light of the iPhone very close to the iMac screen and look what happens! In my case I can see all the info there! It's difficult, but if you have a enough power light and you put it very very near to the screen, you should be able to see the icons, the windows, the images, the texts and everything of your desktop or your system running is there, but with the backlight switched off. You can test your computer to see if the same happens to you. In my case, I think it's simple: the problem is that the light of the screen (LEDS) is switched off.

So, I'm 90% sure it's a problem related to the LED DRIVER BOARD, also called the inverter... and sure it should be replaced. But any case, Apple should say something, because although all of our iMacs are out of warranty, I think it's not normal that so many iMacs having the exact same problem. Perhaps this models, after some years of use, start all of them having the same problem with this piece of hardware.

Respectfully ChoPrats I really don't believe the LED Driver Board is the problem in 99% of the cases here all my tests have proven to me that this is a software related problem. Here's the main reason I believe that the LED Driver board has nothing to do with it if you boot into windows the screen never goes black. If it was the LED driver board then it would have the same effect on a window installation also it can't be heat related because it can happen within a few minutes of turning on your PC to happening after a couple of hours. and lastly it only ever happens after the Apple logo has appeared on the Mac from startup. indicating that it's only when the OS is initiated does the problem appear also it can happen on power books and iMacs and I believe the LED power board is different on said products. forget the recovery position because you are not removing the problem do a clean fresh install from scratch and the problem goes away. take a look at my previous posts I have not had a black screen since I did the fresh install and just to add I have now run my iMac for 5 days straight without going into sleep mode just letting it continually run and it has not missed a beat. I have been an IT tech now since 1983 and I have found most of the Apple techs I have spoken with especially in the apple stores around me well let's say I have forgotten more than what they know. Also, they tell me that the 27" 2009 model cannot use more than 16GB ram I run mine with 32GB which tells me they haven't a clue about their own products capabilities.