Stepppy

Q: iMac 27" Screen goes black repeatedly, but then settles for a while?

Hi

 

I have searched and found numerous posts which sound similar to mine, but none seem to be so bad. Its a long post, but I want to make I have given as much information as possible

 

My Energy Saver settings are default 10 minutes for display & computer sleep, but I always find the screen will go black for a period of time before it goes to sleep and normally when I go back to it I press the keyboard or trackpad and the screen comes back to life. However, this time it didn't. I tried everything I could, but in the end I had to hold down the power button until it turned off. Once I restarted it was ok again.

 

I didn't think much of it, but I researched and found lots of people had similar issues, but were mainly on MacBooks. I did find a post where people had set a hot corner to turn the display off, so if the problem happened again they went into the hot corner and then came out of it and the display would come back on. This stops the need for having to force the computer off. I set up a hot corner, just in case it happened to me again and I'm glad I did.

 

In the last couple of weeks the display has been going off at random whilst I have been using it, nothing graphic intensive, just web browsing. Going into my hot corner and coming out of it bought the display back to life thankfully. It was yesterday that things got really bad, to the point that the display was staying on for about 3-4 seconds before going off. Again, going in & out of the hot corner worked, but then it didn't. Initially I thought it maybe some kind of software issue, but when I restarted the grey screen would only show for about 3 seconds and then go black, so I didn't even see the Apple logo. I could hear everything start and it would pause at the logon screen. Going in and out of the hot corner several times finally gave me enough time to login before it went off again.

 

After logging in I got it back only for it to go off again. I tired everything I could to get the screen to come back to life but it didn't want to play. All the time everything was working on the iMac, it wasn't frozen and didn't crash, just no display. I did some research on my iPad and this seems to be a common problem in one form or another, but no one that I could see had it as bad as mine. Some people were saying it was software related, other that it was logic boards, but as I said earlier I think the majority of posts related to MacBooks and not iMacs.

 

This was my first Apple purchase and I feel like a fish out of water as I have always had PC's before and if they went wrong I just fixed it myself, but I don't think this is going to be the case this time.

 

Very late last night I managed to get the display on long enough to run iBoostUp and let it give everything a spring clean. It kept going off whilst it was doing its things, but I did manage to get the display back for long enough to shut it down fully and I left it unplugged over night.

 

It started working fine this morning, but after more reading I have reset SMC and PRAM as that advice seems to be given a lot when people are having problems.

 

I have been using it for roughly a couple of hours and it has just this second gone off for the first time. I did my hot corner trick to get it back, then about 3 sends it went again. Now it seems to be ok again. The only program running is Safari.

 

I am running Lion 10.7.4 with all updates done and I am not running Boot camp for Windows 7 I thought about doing a clean install, but I am not convinced that is going to work and don't want to go through all the hassle of that only to find it still does it! Taking it to Apple worries me, because as its intermittent it may not do it whilst they have it and also I am worried about all my personal data I have on it. Would they wipe the hard drive and would they access my files? I have never had this worry before as any PC problems I just switched problem items myself. The machine will be a year old in a couple of months and I am already thinking the AppleCare Protection Plus is a very good deal and a must have at £139 for two extra years warranty.

 

Any suggestions great fully received.

 

Thank you.

iMac (27-inch Mid 2011), Mac OS X (10.7.4), 12GB RAM 1TB, AMD Radeon HD 6970M

Posted on Jun 24, 2012 5:44 AM

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Q: iMac 27" Screen goes black repeatedly, but then settles for a while?

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  • by Ulli Hesse,

    Ulli Hesse Ulli Hesse Feb 4, 2015 2:02 PM in response to jrthurm
    Level 1 (0 points)
    Feb 4, 2015 2:02 PM in response to jrthurm

    jrthurm,

     

    i never used boot camp and windows on my imac.

     

    But for both OS X and Windows, there is a so called EFI partition, loaded before the operating system (no matter OS X or Windows), that is rewritten by the clean install.

    EFI is something like a newer bios to control the hardware and their firmware.

    And the backlight is controlled by the SMC (system management controller), which is controlled and initialized by EFI.

     

    So, it could be the case, that the EFI partition is corrupted due to different versions installed by different versions of OS X.

     

    I bought my used Imac from the seller, that told me, he had just installed the OS X 10.6.2 from the dvd packed with the imac. Maybe, he did installed it without formatting the hd. Before the seller installed 10.6.2, there was of course a newer version of OS X. Then I installed the update to 10.6.8 without formatting, and then I went to 10.10.0 and 10.10.1.

     

    Then on the hd, there were many different Versions of the EFI partition. If the installation program of one or more Versions of OS X would not write EFI cleanly to the hd, then this error could occur.

     

    This is something, Windows PC user saw when using windows for a long time, upgrading to newer version of it without formatting the system. It leads often to problems with drivers and the stability of the system. In OS X, this could happen as well.

     

    The Imac is an all in one computer with build in display and backlight. The backlight is controlled by the smc, not the monitor itself. So the imac is a very seldom desktop system, where a backlight error can be caused by the EFI or Software in the computer in general, that can be corrupted.

     

    Maybe this can explain, why a clean install can solve the backlight issue in both operating systems

  • by markb59,

    markb59 markb59 Feb 7, 2015 11:09 AM in response to Stepppy
    Level 1 (0 points)
    Feb 7, 2015 11:09 AM in response to Stepppy

    ive had the same prob with mine i installed caffine it stop the screen shutting down i have since found out that as soon as i install flash player it shuts the screen down so now i do not use flash player hope this helps

  • by Ulli Hesse,

    Ulli Hesse Ulli Hesse Feb 7, 2015 1:05 PM in response to markb59
    Level 1 (0 points)
    Feb 7, 2015 1:05 PM in response to markb59

    Imac just running fine without any error or screen blackout since the clean install.

    No need of doing anything against the blackouts any more. No caffeine, no temperature / fan control or opening the memory slot for more air. The Flash players is installed und no problem. No active edges for the monitor standby and wakeup. Just nothing and it works.

     

    My Imac is used very often and long. Display brightness at about 80%, it is the brightness level, where I got very often a blackout before the clean install.

  • by jdvelasquez,

    jdvelasquez jdvelasquez Feb 17, 2015 8:23 AM in response to Ulli Hesse
    Level 1 (0 points)
    Feb 17, 2015 8:23 AM in response to Ulli Hesse

    Same issue here. iMac late 2009. Did a clean install of Yosemite yesterday, hoping that would do it, but it didn't work. Changing brightness is the only way I can keep the screen on or reproduce the issue. Change brightness to be > 50% and it goes black. At 20%-30%, it stays on (2+ hours so far).

  • by Ulli Hesse,

    Ulli Hesse Ulli Hesse Feb 17, 2015 10:53 AM in response to jdvelasquez
    Level 1 (0 points)
    Feb 17, 2015 10:53 AM in response to jdvelasquez

    Hello jdvelasquez,

     

    sorry to hear that.

    My Imac still is perfect after the clean install with USB stick after formatting the whole hardisk (important to format not just one partition).

    So in may case, maybe because of the replacement of the backlight driver board or the v-sync cable in combination with the clean install the issue was solved.

    The replacement of the parts without the clean install didn't work, too.

     

    Did you really format the whole harddisk (the first entry in the disk utility)?

  • by jdvelasquez,

    jdvelasquez jdvelasquez Feb 18, 2015 7:30 PM in response to Ulli Hesse
    Level 1 (0 points)
    Feb 18, 2015 7:30 PM in response to Ulli Hesse

    Thanks, Ulli. Yes. I formatted the entire disk. Just went through the same painful process again (with a flashlight on my screen), just to make sure. 

    Same issue, unfortunately. It works ok with low brightness (25% at most), but goes black above that. Glad to hear yours is still running well! Next try might be the backlight driver board. But it drives me crazy, as I suspect this is really a software issue.

  • by Ulli Hesse,

    Ulli Hesse Ulli Hesse Feb 19, 2015 12:56 PM in response to jdvelasquez
    Level 1 (0 points)
    Feb 19, 2015 12:56 PM in response to jdvelasquez

    Hi jdvelasquez,


    yes, this issues has driven me crazy as well. And after all, I can´t say exactly, if it was a hard- or software or a combination. I just did everything, that could help and in the end, it works until now. So, i really would like to help if I could, but at least i have my freedom with my Imac. Before the issue was solved, it would have been a pleasuare to throw the Imac out of the window.  I just was one minute to go to a repair company when I thought, I have to format the whole harddisk because of my privat data on it.  The fresh installation saved time and money for something, even the repair company probably would´t have solved. Good luck!!

  • by jdvelasquez,

    jdvelasquez jdvelasquez Feb 19, 2015 9:12 PM in response to Ulli Hesse
    Level 1 (0 points)
    Feb 19, 2015 9:12 PM in response to Ulli Hesse

    Thanks, Ulli. Please don't feel obligated to respond. Just posting here as I continue testing things in an effort to understand what's going on.

     

    One more reason I think this is primarily software related: Last night I did a clean install of the old Snow Leopard (10.6) and the screen works beautifully. Left it on at full brightness, w/o going to sleep, for almost 24 hours now, and no problems. Oddly, the brightness control slider (which existed in 10.5) is missing from the Display system prefs, and the brightness control keys on my keyboard didn't work either. Upgrading to 10.6.8 fixes these and all come back.

     

    I just attempted to do a clean install of Yosemite again, now with a bright screen that was working with Snow Leopard. After loading the Yosemite image, just about to do the formatting of the disk, the screen went dark. Same issue. Is it a problem with kext files? What is loaded by the OS X installer at pre-install that could do this?

  • by davidpak,

    davidpak davidpak Feb 28, 2015 1:50 AM in response to Stepppy
    Level 1 (0 points)
    Feb 28, 2015 1:50 AM in response to Stepppy

    Hey guys,

     

    *This Might Work*

    I have the Late 2009 model.

    I been having the same issues with screen going black for about 3 months now. I tried many fixes but noting seemed to work. The only way it would work if I had it set at the lowest brightness. Once I start adjusting the brightness, BLACK SCREEN! So I ordered the LED Driver board - installed it - and still the

     

    black screen! Finally I tried to unplug the V-Sync cable (see below) and start up my Imac. BAM! no black screen, although there will be a high pitched whining noise if your brightness is set >50%. So my problems seems to be with a bad V-Sync cable. It works for now, I can deal with the noise until my new cable arrives.

     

    Screen Shot 2015-02-28 at 3.48.37 AM.png

  • by jdvelasquez,

    jdvelasquez jdvelasquez Mar 8, 2015 7:49 PM in response to davidpak
    Level 1 (0 points)
    Mar 8, 2015 7:49 PM in response to davidpak

    Thanks, davidpak. Decided to take the plunge and do it. Ordered a new v-sync cable. The old one wasn't bad at all, actually, but replaced it nonetheless. Reinstalled yosemite from scratch, again. Had a brief hour or so, where I could have the brightness at a high level, but then it went black again. So no solution on the v-sync cable, at least for me.

  • by villasboascico,

    villasboascico villasboascico Apr 10, 2015 8:08 AM in response to yvettegri
    Level 1 (0 points)
    Apr 10, 2015 8:08 AM in response to yvettegri

    Hey yvettegri, how I can reach you?

     

    About the thread still running on Apples's forum, I trusted ur point of view abou the HDD Fun Control, I bought it and yeah, we came through the same way in this issue (having the screen turning to black constantly while the system still goes on, like iTunes keep playing  music, etc). I replaced my HD and I do believe the screen goes black due to a misscontrol of something related to that.

     

    Can you help me with HDD Fun Control setups? I'm running a iMac 2,66 i5 with the 10.9.4 osx.

     

    Thanks in advance,

     

    Cicero

  • by cumartesi,

    cumartesi cumartesi May 3, 2015 12:34 AM in response to Stepppy
    Level 1 (0 points)
    May 3, 2015 12:34 AM in response to Stepppy

    SOLUTUION FOR ME!! (maybe for everyone)

    i had this problem like a curse for a year. apple services couldnt detect anything. i used to use extentional power supply to protect my imac from power outage harms. i dont use that anymore and i replaced power cord cable with very regular power cord. its not an apple's product even. NO MORE BLACK SCREEN. i know it can be seems irrevelant with screen thing but i dont know. it is working for me. i waited 2 months for testing and observing my imac before write here. everything is just fine. full brightness of course..  i wish a salvation from this blody curse for all of us. byez.

  • by AutoCanuck,

    AutoCanuck AutoCanuck May 25, 2015 11:51 AM in response to Stepppy
    Level 1 (0 points)
    May 25, 2015 11:51 AM in response to Stepppy

    Thanks to the help of other users of this forum I got my problem solved, at least for now (fingers crossed).

    My 27-inch late-2009 iMac was working fine since I bought it new until yesterday, when the screen just went black. The day before I watched youtube for a couple hours which I rarely do. My guess is that this caused the iMac to overheat. It started normally, but then the screen went black, although everything else was seem to be working. Tuned off and on a few times, the screen blinked couple of times, but otherwise stayed black. I got the Apple Mini DisplayPort to HDMI adaptor and connect the TV as an external monitor. The external monitor was working, so it wasn't the Power Supply module or the Logic board. I went through many posts on this forum and many suggest to use the flashlight to see if there is image on the screen with no backlight or there is no image at all. In my case, there was no image at all, so it wasn't just missing backlight. I disconnected the power cord and took the glass off then the display itself (there is a youtube video on how to do it).  Actually the glass came off without using the suction cups, I just pulled the top edges gently with my fingers. I disconnected all 4 cables and removed the display. Vacuumed all the dust out (there was a lot, no wonder it overheats) from the fans, heat sinks and the bottom screen using the vacuum brush adaptor. One thing that I noticed was the display data cable connector plug  (photo from Ifixit website) that connects the display to the Logic board came off very easy, like it wasn't holding well. I tried to connect it disconnect it, it clearly wasn't holding well; it felt loose. I looked with the magnifying glass and it looked like the connector (again, photo from Ifixit website) on the Logic board was a bit curved up in the middle, although everything else including the soldering looked OK. Using my nail I gently pushed the middle of the connector towards the Logic Board to make it parallel to the Logic Board. Then I used the Electrical Contact Cleaner Spray to clean the connector and the display data cable end plug. I tried to connect the display data cable and it was holding much better now. Everything is back together and it worked! No black display and now even the fans don't  come on at high speed anymore, I guess the dust was blocking the cooling air flow. I'll update later if it's still working, but I strongly believe that the warped display data cable connector at the Logic Board was the culprit in my case.

    Hope this helps!

    GL!

  • by marcduchesne,

    marcduchesne marcduchesne Jul 10, 2015 2:31 AM in response to jdvelasquez
    Level 1 (0 points)
    Jul 10, 2015 2:31 AM in response to jdvelasquez

    Hi There,

     

    Got the black display issue here this morning, on my Late-2012 iMac 21.5" running Yosemite 10.10.4. Never had the issue before today.

    Here in South-Western France, we've got extreme outside temperatures a week ago : 40°C and above. In my home office (under the roof) I guess it reached the 55°C barrier.

    Being on the road for a week, I just switched on my iMac this morning : Display went black every ten seconds or so, with no reason.

    I'm typing this post on my MBA, the iMac before my eyes : Display bright clear, no glitches no dark screen since ten minutes or so.

    Like you, I was more on a Software bug rather than on a Hardware problem. Bingo ! Thanks to a guy in this thread - back in 2013 or so.

    The fix is very simple : System Preferences / Energy Saver : Display sleep to "Never".

    Works perfectly well here.

     

    ps: in the meantime, I've run all the sw fixes explained in this thread : Permission repairs, Display brightness, etc. Maybe the fix is a combination of all that.

     

    Hope this helps,

    _Marc

  • by Brad Elec Eng,

    Brad Elec Eng Brad Elec Eng Jul 28, 2015 3:45 AM in response to Stepppy
    Level 1 (0 points)
    Jul 28, 2015 3:45 AM in response to Stepppy

    Hi, though I would add my experience to this thread as I also did a lot of reading to see if I could fix the same fault on my mid 2010 mac 27". In my case the screen would go black at random intervals and got progressively worse until the screen would only be on for a few seconds during boot up. Since I am happy to open electronic things (my job) I followed one of the many Youtube posts to have a look inside. Usually these sort of problems are related to poor electrical contacts on connectors so just pulling out the LCD and reconnecting the connectors is always a good start. The video cable has a connector at both ends so peel back the metal tape on the rear of the LCD and reseat this end of the video cable as well.

     

    There is a reported fault with the backlight connectors at the bottom left and right corners of the LCD screen. Again you can carefully peel back the tape and have a look - a gentle movement on the cable bundle will show if the connector has come loose and requires more drastic surgery. In my case the fact that the backlight came on (if only for a few seconds) showed that the LEDs themselves were working and there was some sort of electrical connections.

     

    The steps I followed were:

    1) connect remote screen using a display adaptor -> if it works then the graphics card is ok

    2) use a torch to see if you can spot characters on the screen. It actually took me ages to shine the light in the right spot at the right angle just near the login prompt before I could actually confirm this. If you can see characters then the LCD is working and the problem is with the backlight board.

    3) Buy a replacement backlight driver board (I picked one up on eBay for $40) and install this. All fixed!

     

    Although in this software centric world of apps people always jump to the conclusion that there is a software bug (and I was hoping for this myself) sometimes you just have to accept there is a hardware problem and get the screwdrivers out. For the backlight driver board failure was probably bought about by early aging of the capacitors (high temperatures accelerate this effect so keep those fans clean) or a failure in the pcbs internal connections (vias) which are also a high failure item in pcbs.

     

    So go through the above and hopefully you will be up and away agin. Good luck and thanks to everyone else for your posts which set me down the path to a solution.

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