iMac screen goes black, but system runs fine in background

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.

You did reply gomoweb. Thanks.

I'm just a little reluctant to bite the bullet right now. I can't face the thought of reinstalling all the apps and getting them back to where I like them.

I guess it'll happen one day when I'm at my weakest and the tears are flowing down my cheeks.

It's just frustrating that even though myself and I'm sure many others have submitted reports to Apple and we're not seeing any response. Feeling abandoned. 😟

Still confused gomoweb, but if it's software related as you say, then it has to be something related to the system management of the mother board or similar, not related to the macOS version installed, because after some more tests that I've done today I can confirm that affects also when the macOS system is not launched yet.

My problem was going worst everyday... yesterday and this morning, my iMac screen remains on just for few seconds after start the computer, and practically instantly goes black. When I try to select with which partition I want to start the computer pressing the ALT key of the keyboard after the chime sound, also the screen goes black after few seconds and I can't see the drives to select. Also, after read your message, I've tried to create a Bootcamp partition and install Windows 7 on it. The problem still persist, even while I was installing Windows, the progress bar and the message "Windows is installing" was showed, but the screen of the iMac went black and I had to continue installing through the second display that I have.

So, perhaps here there are a lot of people talking about a similar problem, but while for some of them perhaps it's software related, I think for others can be perfectly hardware related. In my case, it's obvious is not only related to software, or at least not related to my macOS version, because the screen goes black also when installing Windows on Bootcamp, when starting the system from a recovery partition, or even in the disk startup selection option, etc.

But well... you're right in one thing: certainly there's something that affects the stability of the issue, and when we play with the system doing changes, somedays the issue seems to disappear or appear less time. An example:

Some hours ago, just after try to install Windows on bootcamp and see that my problem still persists even when installing Windows, I have done 3 SMC resets, 2 PRAM resets, tried again to start from a recovery partition (it asked me to pair again the magic mouse and apple keyboard with bluetooth) and finally deleted again the Bootcamp partition. Well, it's strange but since then, now I'm using macOS normally and the iMac screen remains on for more than one hour... Sure it will become black again later, but now it's more stable than before doing all of this things, because this morning the screen was going off constantly, just after 5 seconds.

So... yes, really there's something that affects the leds management, I don't know what is, but something seems to have some incidence on it. In PCs, I remember that exists something called the "BIOS" that manage the hardware when the system (Windows) is not installed or launched yet. Perhaps there's something similar in Apple computers (not only EMC or PRAM) that becomes corrupted and causes this problem... And perhaps a new fresh installation like you did, can help and change something.

Thank you for sharing your experience. I took my iMac (mid 2010) into the Apple authorized independent repair shop, and he said he would need to keep it for a few days and run some of the same diagnostics that Apple did. He says Apple just want us to buy new computers.

I couldn't leave it and lose that many work days. Still working fine with external monitor, but at 1920 width. I definitely am not going to invest in a new display screen.

Maybe a clean install.

Hi ChoPraTs Yes you could have the screen going black during installation of windows because it is being installed through the OS as boot camp is part of OS. I think the difference between our two systems is I had windows installed before I started having the black screen problems. Unfortunately, you're trying to install it on a corrupt system. I take it you use timemachine and have a backup of your current system if so download the latest version of the os there is a good article on livewire about the steps to take see the link below. I would bet a pound to a penny that your problem is software related. and there is nothing wrong with your hardware My Mac has now been running nearly 8 or9 weeks the last 7 days now with continuously and the screen has not blacked out once. There is something similar to the Bios on a Mac as Macs run on the Unix system. Once the Apple logo appears on the screen that is when the OS takes over. Good luck I hope you fix your problem I hope some of what I have said helps How to Perform a Clean Install of macOS Sierra

Gomoweb,

I think I'm going to do a clean install on my iMac to see if it helps. I upgraded to Sierra about 5 months ago. I believe that's when the dark screen started happening. You don't suggest going back to a prior system like Yosemite or Mavericks?

Hi, Michael I didn't I'm Running Sierra 10.12.5 if you click o the link I gave ChoPrats tit will give you one of the best set of instructions on the how to do a clean install. also be for you start I would suggest printing out the instructions and reading them through a couple of times to get your head around them. I'll let you into a little secret "Most people don't read instruction manuals and that's why I make a good living out of fixing Computers" Also you'll need a 16GB usb stick. Good luck and let me know how it goes.