iMac 27" Black Screen?

I got same issue last week, 21'' model bought in 2012. It turns to same issue even into recovery mode.

I'm using a mini dvi adapter connecting another display as termporary solution to keep mac running.

I would follow to see how this issue walk out, but don't expect support says exchange your computer with new model, as it is not like a isolate problem at all.

I have a 27 inch Imac that I bought used with the same problem. I have read a lot of posts over the last few days. Some people have suggested running Apple Hardware Test Extended three times from Disk 2 of your original disks, which I am doing. One thing I noticed that I thought was significant was the fact that during the test, the screen remains bright and works fine. Which to me suggests that it is NOT a hardware problem, unless the test mode bypasses some hardare?.

I have mavericks on the computer, and the only thing that seems to work for me is to keep the brightness slider low. If I raise it up, it instantly black screens.

I have the same problem with my iMac 27" Late 2009, the only way to keep the screen on is to reduce the brightness to a minimum level, two days ago I tried to reinstall the combo update of El Capitan 10.11.1, At the moment I don't have any black screen with the brightness at maximum level, in my humble opinion this means that the black screen problem is not an hardware problem but a software bug, if someone want to try my solution and share the experience this could be useful.

I have a 2010 mid-year 27" iMac that started having the intermittent sudden "black screen" after upgrading to El Cap. I too thought the computer was shutting off but discovered quickly that the screen only was shutting down. I was watching some YouTube vid's and the sound was still coming through my headsets. Also discovered that holding down "Option" then "Command" and releasing would bring the monitor back up. Installed SmcFanControl and sped things up but that didn't seem to help.

I am using a wired, full size keyboard and BT Trackpad and Apple mouse. I have not tried a new/different keyboard but will give that a go and see what happens. I will also open her up and unplug and reattach all connectors.

I have a late 2009 27 iMac with the black screen problem. I tried everything, even a local repairman (I'm in Korea) to fix it for 6 months. I fought with it for over a year. New OS did not help, keyboards, settings, nothing. Installed fan application in computer, and put an 8 inch external fan directly on it. Nothing.

It appears to be heat related, and the only fix is another Mac.

I had hopes of a solution, (and for what t's worth) but ended up wasting a year of productivity.

The only solution I read in that whole year was some guy found a tech guy to open the Mac and disconnect and reconnect all the wires.

I have the issue with 'Black Screen' on my late 2010 27-inch iMac. Boots up fine, but then screen randomly goes black. The iMac is still alive as I can still hear things playing. Someone suggested I try putting the iMac to sleep using the cmd/alt/eject key commands. Well I tried this, then touching any key afterwards, the screen came back on. It did however go off again after a couple of minutes, but used the same tactics again and it worked again. Still a pain, but a solution.

I don't know if this is all too late but I'll share this with you for what its worth. I have an iMac early 2010 that is running mountain Lion and I have the dark screen on one side issue. The computer still works and I can see the screen ok so i haven't bothered with that too much. But after a time it started going black although it was clear the machine was still working. After a lot of fuss and bother and asking around apple techs who suggested graphic card power supply and all the things everyone here has gone through. None of them would guarantee anything except a large invoice! So being a bit of a tech I decided to investigate the internal workings of the machine. Instructional videos of how to dismantle these machines proliferate the net. So armed with a torque screwdriver set I set about removing the screen. Much easier than you might expect.Laying the machine on its back and looking in from the top of the machine on your right hand side there is a delicate four pin plug that is the power feed to the screen. If you do open the machine be very very careful as everything is extremely fine and delicate. Make sure this plug is making good contact by very gently applying a little pressure to the plug. if you are brave have the machine running while you do this. When I did this the screen sprung to life and has been working fine ever since1 I hope this helps someone.

So after reading pages and pages of 'solutions' and trying many (and thanks everyone for their efforts) only to see later on that those miraculous 'solutions' only lasted a while, and people, including me, are back to square one,I've discovered that doing nothing but simply unplugging and replugging also 'solves' it for a while. A week and a half ago, I simply unplugged, rebooted, and there was no problem again until today, when again it blacked out every two seconds (for which option command esc, press the mouse, will only work so many times, before it won't at all). Shutting it down, unplugging it, rebooting, as it often does, has got it working for me again for the last few hours (until next time) so I am reluctant to say that any of these things we're all trying are what makes it work again for a while.The only thing I am trying now is a lowered brightness, because I didn't yet - but, like I say, by doing nothing on my 2009 model, it will work for well over a week, and then go out consistently until I start the process all over again. I think its the latest OS's responsible, and was hoping with the latest update from El Capitan, it would address the issue. Apparently not. I may just get an external screen instead of buying a new 27inch, given that I have read even newer models are suffering the black screen of death.

I have a 2011 27" iMac, the base one at that time.

The screen will go black, push and push on the power button sometimes it comes back on, sometimes not

It get's real how on the upper back left side (when looking at it)

I replaced the 1TB spinning drive with a 1TB SSD (Munchkin Amazon now like $239 for 1 TERABYTE ok......I mean who would not do this), also the memory is at 16GB I got too (a while back)

I bought the unit brand new from Amazon, Apple care....loved it

Now it's 2016, so it's "antique" as far as Apple is concerned.

Well I don't have a tree in the back yard of my townhouse that grows money, and we need this to work.

I made a appointment at the Genius bar at The Falls here in Miami

The kid (younger than me by like 16 years, so for me, a kid) plugged it in, booted it up from their servers and ran diagnostics

Said a sensor was failing.....ok. So a new motherboard (well refurbished) was order

I have not paid for it yet, but the total cost is $583 + tax......still cheaper than even a refurbished one @ $1500 form Apple.com

Well they called and said the board was here, I took it today and then I started to think, failing sensor.......uh yeah.....the SSD does NOT have a thermal sensor on it and I didn't have the wire plugged back in and shorted out.

We use a program to adjust the fans, Macs Fan Control, 1.4.0 and keep the fans at a constant speed, the temps have aways been less than 140 F on the power supply.

So I told the kid at the Apple store (who said he had not dealt much with that year/model a.k.a VINTAGE) units before, to check the backlight board, put a external display to it, check the power supply.....I mean the PSU does not have just ONE connector on it, and my being a electronics/electrical guy (I am IBEW and before was IT/telecomm, so I have a diverse background but I don't have the stuff to pull my iMac part like suction cups,etc even thou it's only magnets that hold the glass on), anyway, I would tack my multimeter and check the output of the power supply. Check the points on the motherboard, and I getting +5 VDC here or -5 VDC there, you know.......ACTUALLY do some technician things (which I have done over and over over the years and no, I didn't graduate from ITT Technical, what a rip for a school)....but have to wait and see.

I have read MANY MANY posts,and my unit with the basic GPU doesn't fall under the warranty thing to swap them out.

It could be the LCD display itself, BUT I doubt that or it would have exhibited things like part of it being grayed/blacked out....the stuff you learn when you actually DO do electronics and not follow a procedure written by a engineer to find the problem, BUT they won't do that.

It is past it's prime, I hope it's not the motherboard and just something like the backlight board, which would be cheaper.

Just debating if I go in the hole for a total of $1800 for a 27" 5K iMac would it be worth it (that's the about the total with the Apple care 3 years,tax,etc)

For me, where money is not flowing like water in the Amazon river, $583 is a big thing and $1800 is like a death blow to trying to be out of the credit card debt ****.....

If anyone has any input on this, as what is a LIKELY culprit then chime in.

It is on OS X 10.11.4 BUT it was going black on and off here and there, a second or two, like last year when I was on 10.8/10.9/10/10

If I unplug it and it sits and the capacitors on the PSU and mother board dissipate plug it back in (which should also be clearing the SMC) and I have tried over and over again on the PRAM, it sometimes stays on and you would never think it had a problem.

Then again, the other day I went and did CMD-R and went to the recovery partition and had it do a re-install, the screen went blank in the re-install part, so that kinda rules out software....

Others let me know, say something if you have had a solution come about or are still having the same problem.

philmiami

please use basic punctuation and paragraph breaks if you want anyone to read it.

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I have the same issue as all of you above. In my case, a 27 inch Late 2009 iMac with i7, currently running on El Capitan. My videochip has been replaced, my power supply aswell, it all only worked temporary. And still I have not found the cause and the solution. I had my iMac working for half a year without problems, sometimes a month, but lately only a few minutes max. I am 90% sure it has to do something with the bluetooth connection, as I have solved my problem a couple of times by going to brightness level 4 (at this brightness, the screen almost never shuts itself down), simply turning off the Keyboard, replacing the battery and once reconnected back to maximum brightness. I have solved the issue at least 10 times with it, giving me another day or week without issues.

but you have guessed it, that also stopped working. Something in the software is telling the screen to shut down, simply turning off bluetooth does not help. The fault seems to 'reset' itself after some action, but the fault itself never gets removed from the system. So the endresult is always another black screen.

Now, since I can not afford a new iMac right now, I have simply started to try things out. Wired keyboard and mouse, no luck, unplugging the iMac for a few days, only minor result. But then I started playing with the brightness buttons. I eventually noticed that the normal screen comes back for quiet a while (sometimes a week) after I get the screen to flicker, basicly what you see is a reset of the backlight, however, I could not mimic it on demand. But I now have found a way (in my case) to actually get the screen to flicker, go to full brightness and at least enjoy 3 days (including shutting off and in the iMac) Of screen time without issues. Here is how.

First: Turn of sleepmode completely. Yes, in order to get as much screentime as possible, sleepmode needs to be turned off, as it triggers your iMac faster into a blackscreen.

2nd: Go to full brightness and wait for the screen to go black.

3rd: Use the 'lower brightness' button to put your screen on the lowest brightness possible. Yes, you can not see this, but it is important you do this when the screen is still black.

4th: press the infamous CTRL-Shift-Eject combo and wake you iMac up with your 'brightness up' button. Rapidly tap (and tapping is important, holding in any way does not work) on the 'brightness' up button untill maximum brightness. On my screen about 50% of the time, the screen will flicker, and 25% of the time, that flicker will reset the auto screen turn off and you will have another few days or week without a problem.

5th: If step 4 did not cause a flicker, go back to step 2.

It is important you start at full brightness when the screen goes black. Why? I believe the flicker is due to your iMac thinking it is still on full brightness, as that was the case when the screen turned off. But you have just set it to the lowest brightness. Once you start tapping that brightness up button like a maniac, the iMac becomes confused because the brightness levels aren't consistent with the setting it has got. So the iMac gets confused, the flickering is a reset and voila, that reset just gave you at least a couple of days screentime.

Again, this is NOT a sollution, nor do I excatly know the cause, and it may not work for everyone, but it is a quick to fix work arround. You may have to repeat it a couple of times, but I have my iMac up and running again within 1 minute now. I'm very happy with the result, as working on my iMac when the brightness is on level 4 is almost impossible with daylight. My iMac started going black 3 years ago, this is the best sollution I have found and has kept my iMac again useable for 4 months now. Yes, I get a black screen after a few days or week, but then I just solve it again.

I hope this post is useful to anyone, even if it would only be one person, as I know how frustrating this issue is.

I took my iMac 27" 2011 to the Apple Store

They tested it and said it was the logic board. $583+tax +$39 install/replace

So I said ok, order it.

I took my mac home and waited until the store (at The Falls here in Miami) called, like 5 days later and I took it to them.

Now this was going by what one of their Genius techs said was wrong.

To pay $600 for a new logic board and get another 3+ years use out of it I was ok with it because $2k for a new one, well that's a different story.

Took a week and they fixed it AND GAVE a 90 DAY WARRANTY in case something happened.

I am ok with that

BUT

SOMETHING did happen.

It went back to the black screen again and I was away, wife was calling.....ah...ok. We have a 90 day warranty to fix it.

When I got back I called the support #. Told the guy what was going on, he said to take it to the Apple store again, no need to make a appointment.

When I showed up draggin the iMac on a cart behind me they were like do you have a appointment?

no

Took them a while to get someone out from the back to test it with me sitting there....and the guy did, and it would not go black screen again.

The guy said they would keep it and stress test it, and asked did I have it the way I have it at home?

NO, forgot the external firewire RAID setup for Time Machine.

Came back and brought that along with the original power cord (he said the RAID setup, even thou hardware on the Firewire enclosure can cause a Kernel panic sometimes and the machine would go into a Safe Mode) or the power cord, it make be broke inside.

I left everything there and two days later they called.

It was the Video driver board, not the logic board.

So they are replacing that at $140+tax

The person that called me told me that even thou the screen is black and the machine goes into a standby/safe mode.....they could see images on the screen using a flashlight, barely, but they could see them.

So for about $750 the machine is "almost" new again and I should get at least 4+ more years out of it, BUT they may refund me the original "diagnostic repair/replace" cost of the logic board, since it probably was not anything that needed to be replaced.

IF anyone is having this problem FIRST try to see if there are icons on the screen using a really bright LED flashlight.

I would also suggest getting the Apple store to do it, not some fly-by-night repair place in a strip mall or one of those "come to your house" kinda guys.

Because at least they (the Apple Store) gives the warranty for 90 days, which I will surely use.

I suffered the same thing. This is what worked for me:

I put the brightness all the way up. Heat goes up, but I have my fans working quite high with smc Fan Control. I have to say I was stocked in one of those moments when the screen goes black all time time, half second after I woke up the computer after I sent it to sleep with the keyboard combination key, and this has been happening three days in a row. Not giving me a break at all. I was going to go to Genius Bar (again). However, as simple as putting brightness all the way up has fixed it.

In terms of diagnostics, for me the black screen was starting to happen after two things that broke routine and could me the trigger here:

- About two weeks before first black screen, I dropped a glass of water over my magic keyboard and replaced it with a usb keyboard.

-About one week (maybe less) before first black screen, I moved to a new apartment. Actually this might be a thing, since in Genius Bar they told me that the black screen thing happened to a lot of people and when they bring their computer to the store, it works well there, but not at home. They call is "Poltergeist". This might be true, as I think there should be something going one with this apartment´s electrical installation. For example, if I turn the oven on and also turn on the heat, all at the same time, all the house lights and electricity goes off.

What didn´t work for me: buying a new magic (not usb) keyboard, changing to a new graphic card, smc and pram resets, four and three bar brightness, Owly App, uncheck boxes in Display and Bluetooth preferences. Nothing.

Had the logic board replaced @ the Apple store

NOT the cause of the problem.....

Then they changed the video back light board and that still did not cure the problem

So they replaced the LCD screen with a new/reman one...

They called me today....

It has passed all testing.

SO.....for the logic board ($589), they will refund me that because their "genius" people said that was the problem but it wasn't.

BUT, the cost of the new display is like $500, so basically they have replaced everything except the power supply and the super drive and for $500 I got a "almost new" machine. So it lasted not quit 5 years before the black screen and now with the "new" parts, I hope it lasts at least another 5 or so years.

Because honestly I can't drop another two grand, but 25% of that, I can (with plastic) {and now I drop the mic to the floor...........}

Short Answer.

Unplug the V-Sync cable going into the Backlight Board.

Long Solution:

I tried changing the V-Sync cable as Apple's troubleshooting suggested, but the problem remained. I have a second Mid-2011 that works fine and began using it as a parts machine to troubleshoot the bad one. Even though they are both Mid-2011's they use different backlight boards, I placed the incorrect backlight board in the iMac and the V-sync cable wouldn't fit, so I just left it unplugged. I had it run for hours on a youtube loop, and with my manually adjusting the brightness and no issue. So I assumed my backlight board was bad. I ordered a new one. Apple even sells them in a kit (part 923-0047) sending both types. I replaced my backlight board with the correct style and hooked up the V-sync cable. I then still experienced the black screen issue. Beyond frustrated I went to put in the new part of the wrong style because the other had worked. Then I remembered that when I did that, I had to leave the V-sync unplugged. I left the correct style of Backlight board, but unplugged the v-sync cable, and tada! No more issue. I can change the display brightness up and down without issue, and it hasn't even shut down on me.