iMac screen goes black, but system runs fine in background

Been watching this thread since my 2009 imac 27" started experiencing the dreaded "black screen". Screen blacks , external monitor is fine, faint icons and desktop on imac sceen. Resets with sleep and wake. SMC fan control first, reset all next, reinstall ox, all gave temporary fix but now its pretty constant. I am going to try the usb plan (disconnect all and if it improves add one by one). Will post results.

I have been a mac user since 1984 and still am pleased with the system and most of the hardware but the lack of addressing (admitting) an obvious error is indicative of many companies and individuals these days. Admit the mistake and fix the problem please. Apple makes enough to do the right thing. stay tuned!

ps.I do have a loaded 2012 imac arriving soon as I really need my machine for work. Would love the old one to work again so I can pass it on to my son.

well , no usb and still black screen :-(

Sorry to hear the usb fix didn't work.

It's been 4 days since I installed the SMC fan control and I have had no issues. Hopefully this will fix it, however, I still think the upgrader to Yosemite has caused this issue with a corrupt video driver that has somehow affected the video card to be less heat tolerant. I have done nothing different than before upgrading about 6 months ago. I have had the iMac since August 21010 with no hardware or software issues. It's been in the same environment in my house so there is no reason why it now requires additional cooling.

I hope this issue is permanently resolved by the SMC fan controller but I'm not holding my breath......................

What worked for me - first a background...

I have a 2009 Imac 27" which has been giving me the black screen of death since about Oct of 2014. It progressively got worse where we hardly used the computer last year (2015) trying to figure out what the problem was. I used these forums to try to come up with a solution. I replaced the LED back light board and that helped a bit, just didn't black out so frequently. Tried the SMC fan control, Owly app, everything mentioned here on the boards.

Five days ago the IMAC was blacking out as it usually does and I tried the following - I increased the display brightness from 80% to 100%. It hasn't blacked out since. So crossing my fingers and hope it is a permanent solution for me. My display is OK to read at 100%, doesn't present a problem for me.

I'll post an update in a couple of weeks.

Cheers

Frastrated beyond believe would be how I describe this issue. My screen begun going black back in the autumn and got progressively worse up until Christmas. I tried all of the things listed in this post and phoned support for their help. I couldn't get to my nearest Apple Store until the New Year due to all appointments being booked and it's a 90+ mile round trip. When I did get there I was told I needed a new Video card which I suspected. A week later I pick it up and when I get home, everything seemed fine until I came to access Safari and Mail etc. Although I was getting a wifi signal, nothing was loading. Occasionally a web page would load but thereafter nothing. I spent the next day on the phone to Apple, even taking the iMac to my parents to try their wifi. After 6 phone calls nothing was working so I connected to my wifi via Ethernet which worked but not convenien. However, after about 40 minutes my black screen problem started again and even though I put the machine to sleep and wake it back up again immediately it will go black again within seconds.

Now I need to return the iMac. I guess what I'm trying to say is replacing the video card does not seem to be the solution, certainly in my case.

Amy advice or similar experiences would be welcome.

Well, I couldn't solve the problem and all the independent repair guys said that the fix would be cost prohibitive. ($450 for an LED backlight board and then the labor) . Found a buyer for the imac as is for $ 350 and got a 2012 imac 27" loaded with 3tb fusion, 2gb video and i7 for $900 with original box, mouse and keyboard. I would have loved to save my old imac but the new owner will with a salvaged backlight board and his know how. While I know that these machines do have a lifespan, Apple should bear some responsibility in matters that are systemic. I have been using macs since 1984 (that great commercial era) when we finally could produce a newsletter, all in house , with a little se and a desk writter printer. My good buddy Mr. Grover was the voice over for that commercial and kicks himself for taking cash instead of stock for payment. Still , I am a confirmed Apple user and most likely will remain so but , Apple, please address these matters so you do not become merely another commercial choice based on only the bottom line.

BLACK SCREEN PROBLEM EASILY SOLVED

Buy a cheap monitor and put that expensive computer on the floor with its screen facing the wall in disgust at Apple's obvious indifference and feigned ignorance of the fact that this is a recurring problem on their iMacs

4 years ago i was suddenly blacked out whilst leading in a £2000 poker tournament only to hear my chips being sucked away ast I stared at my very expensive blank screen. The computer languished at one of Apples authorised repair centres where after 6 months I picked it up only to be told they could not find any fault with it. I turned it on and within 20 minutes it went blank again. I have tried most of the suggested remedies on this forum but I decided not to throw good money after bad so for 4 years the computer now sits under my desk with the screen going on and off as it pleases making no difference to my viewing on my cheap Samsung monitor. I will never buy another iMac

Just had this happen for the first time, late 2009 27". Sounds like it's a different problem than the heat-related one many people in this thread are describing, it only seems to happen when trying to wake from screen-saver.

For the record, the CTRL-SHIFT-Eject trick worked for me. It's bizarre that SMC and PRAM resets didn't, but whatever. And just for fun, I did the suggestion at the top of page 3 of this thread, unchecking the box in Bluetooth settings about allowing Bluetooth devices to wake it. I have no idea if this will help, but I could see Bluetooth being a culprit.

Obviously that's not a great option if both your keyboard and mouse are Bluetooth, because then you wouldn't be able to wake it at all, but my mouse is USB (I hate Magic Mouse).

I have been suffering with this for a couple of years off and on. I tried re-installing and everything else on here, but it never worked for long. This is how I solved it.

Put computer on low brightness

Unplug all usb

Put computer to sleep

Plug in a USB external drive

Wake up computer

Unplug USB

Increase brightness to what you want (do not reduce brightness again or you will have to start at the beginning)

It works, my mac is on full brightness as I type.

Hope it helps.

I have been suffering with this for a couple of years off and on. I tried re-installing and everything else on here, but it never worked for long. This is how I solved it.

Put computer on low brightness

Unplug all usb

Put computer to sleep

Plug in a USB external drive

Wake up computer

Unplug USB

Increase brightness to what you want (do not reduce brightness again or you will have to start at the beginning)

It works, my mac is on full brightness as I type.

Hope it helps.

Wow! kazbluesky, that really works!!!! THANK YOU!! How did you figure that out? My imac has been on full bright for about a 5 days after weeks of the black screen issue!!

I did the same and everything works great... No more black screen and no high sound or flicker... :-)

Well, this worked for about a week or 2 and now the issue is back!!! I tried kazbluesky fix again and it only worked for about 2 hours then black out. I can only work on 4 bars of brightness. As soon as i go brighter the screen goes black. kazbluesky, have you had better luck???

Ive been having this issue recently too. Nothing seems to fix this problem. Im assuming that this problem is happening because my iMac is getting old. My iMac is a 27-inch, Mid 2010 model. Will Mac offer some solution to this problem? If not then i will have no choice but to buy a new computer.

I wanted to weigh in on this thread because it seems like many people are having this problem. I have a 27 in iMac (2009) that ran well until 2015 when the screen started going blank out of nowhere. As others have described, the computer was still running, just the monitor was black. I research and tried everything described above and finally took it to an Apple licensed independent tech. He found a problem with the hard drive. We tuned up the RAM and with the new hard drive things ran fine. He also installed the SMC fan program.

I thought I was out of the woods until a few months after it came back from the shop, the dreaded black screen started again. I found this thread, ran all the diagnostics and restarts, PRAM, etc. I double-checked the fan settings and could not stop it from happening. Thought about tossing it across the room but it's pretty heavy.

Finally, after CTRL-OPTION-EJECT'ing every few minutes, in desperation -- I lowered the brightness (again, a tip from this thread) down to 3 and it has not went to that black screen since. This is a really crappy fix -- having such a dim monitor, but at least I can use it now. I will continue to research and see if I can find a permanent solution. I did want to thank everyone who posted -- good luck everyone!