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 joedwardes,

    joedwardes joedwardes Aug 1, 2015 4:09 PM in response to Brad Elec Eng
    Level 1 (0 points)
    Aug 1, 2015 4:09 PM in response to Brad Elec Eng

    I have been working for weeks trying to get to the bottom of my 2008 iMac screen constantly going black.

     

    I tried every fix suggested, in every forum I could find.

     

    I did all the PRAM and SMC resets over and over, I uninstalled and reinstalled Yosemite, I unplugged all peripherals, I installed smc fan control in case it was an overheating problem. I turned off bluetooth etc etc


    NOTHING worked.


    I was about to give up and resign myself to having to cart my heavy machine down to the Apple store with the prospect of spending a lot of money to investigate and maybe not even fix the problem. But there was one last thing I'd read that I hadn't tried. I couldn't see how it would make a difference but I had nothing to lose so tried it.

     

    It worked!!!

     

    The solution? Try a different keyboard.

     

    So simple but so effective. I was using a wired Apple keyboard with a usb stick plugged into it to power a wireless mouse. I plugged the mouse usb into a usb port in the iMac and plugged in a different (wireless) Logitech keyboard.

     

    Ta da! Problem gone.

     

    I can only assume that the Apple keyboard was causing a glitch (like tripping a fuse) in the display. Different keyboard, no problem.

     

    I urge anyone with this problem to give this solution a try. It's like a miracle cure

  • by Al in St. Pete,

    Al in St. Pete Al in St. Pete Aug 22, 2015 7:57 AM in response to joedwardes
    Level 1 (0 points)
    Aug 22, 2015 7:57 AM in response to joedwardes

    Hi Joe ... It's been 21 days of your new keyboard fix. Is your iMac going black problem still fixed?

     

    I have a 2011 27" Intel iMac and am having the going black problem described in this thread. The only solution I've found - and it may be temporary - is dimming the brightness to its lowest setting.

     

    I read that I'm entitled to a new AMD Radeon 6970M Video Card replacement under a recall program and will be checking into that.

     

    You're all brilliant. Wish my monitor was   Carry on.

  • by RyanRadio,

    RyanRadio RyanRadio Aug 29, 2015 2:21 AM in response to Stepppy
    Level 1 (0 points)
    Aug 29, 2015 2:21 AM in response to Stepppy

    I've got an iMac with the same problem! First thought it was a sleep issue and software related, but sure enough there is still a shadow of an image, so thats almost definitely backlight hardware related. Its even blacked out before could get to OS selection. Been scouring the web for a couple days now, and there seems to be a few variations of the issue. Most are summarized in this 15 page+ thread!

    -If you don't see a brightness meter, reinstalling OSX will fix, likely a KEXT /driver issue

    -A grounding issue in which a new UPC cable does the trick.

    -Even a faulty keyboard, maybe sending a sleep command, or some sort of monitor brightness function.

    -But for those with the stubborn back light dropping out, I would say things point to the backlight board. But that only seems to work for some, so were left with one more known possibility - there is a confirmed problem with the V-Sync cable connector on the display of 27" iMacs of your erra. That is, the socket, not the Cable. Over time the solder on this connection breaks up. The reason frequency increases in black screen while the computer is on, is the joints warm up and expand, and disconnect. Although this known issue in 27" iMacs is more popular for manifesting itself in other ways such as a half dim screen, its possible that this faulty connection could result in a total black out. Repairing it in that case, is unfortunately pretty tricky and requires some pretty extreme soldering skills. From what I hear, Apple protocol is to replace the whole screen. Which I get when it comes to amount of work and tools it would take to repair. Hope that helps any other pour souls with the same issue! I personally am going to try a new backlight board, just in case.

  • by LondonLaurence,

    LondonLaurence LondonLaurence Oct 1, 2015 9:11 AM in response to RyanRadio
    Level 1 (4 points)
    Oct 1, 2015 9:11 AM in response to RyanRadio

    Hi Ryan - Did you change the backlight control board and did it work?

     

    For the sake of adding my name onto the long list of owners of faulty iMacs ... I also have a late 2009 iMac (2.66ghz i5) bought new in 2010 with the same "black screen" issue. The issue started to appear very randomly in May 2010 just after my applecare ran out; I initially thought it was a software issue of some sorts and as it was a random fault did not take any actions other than keeping my eyes and ears open for possible fixes and avoiding to use the iMac much.

    With time the "Random black screens" became more frequent and the iMac is now only usable at a brightness of approximately 4 bars maximum, above this the screen goes black within a few seconds.

     

    What are the symptoms:

    - Randomly the screen gets black. Initially the fault occurred every few month but could some time happened repeatedly in quick succession on a single day, making the iMac unusable on this day. Nowadays, the fault is much more frequent if the display brightness is set above 4 bars (Roughly 30% of the Maximum possible) and this appears to be reducing with time.

    - The computer continues running as normal when this happens - There are no events/errors in the logs.

    - The image is still visible on an external display and the computer can be operated as normal.

    - Shining a torch on the black screen shows the actual image is there in the background.

    - The black screen can occur when the computer is starting up (even before the log in screen) and is cold or later and does not seem to be temperature related.

    - As I do not see any glow on the screen when it turns black, I assume that the backlight is off.

    - An extended diagnostics check identified no hardware issues.

    - PRAM and SMC resets did not solve the issue.

    - The screen can be "awakened" by using SHIFT CTRL Eject + any key or by putting it to sleep and waking it up again. I set-up a hot corner at this effect.

    -  A screen recording of the screen during blackout using QuickTime player does not show any blackout. The screen looks normal as per the external monitor.

     

    Next Steps:

    As I am interested to know exactly what caused the issue, I am taking the iMac to a well reputed electronics repair company for a full assessment tomorrow and if they succeed in tracing the issue to a specific component or connection I will report back on this thread and hopefully help others with the same issue who may be looking at keeping their old iMac for a bit longer.

     

    As a side comment, I would point-out that the Apple certified resellers/service providers were mostly interested in changing parts until eventually they got (or not) to the right one; a way to operate that is fine when an item is under warranty but that can be extremely un-economical for an out of warranty item. Add to this, the diagnostics cost and it is a potentially very pricy repair! I was even told by one of them that I got good use from the iMac so should not have anything to complain about! OOPS! I guess I need to stop being a laggard!

  • by Murrfk,

    Murrfk Murrfk Oct 13, 2015 3:12 PM in response to Stepppy
    Level 1 (0 points)
    Oct 13, 2015 3:12 PM in response to Stepppy

    I have done a lot of reading on this, as I have a Late 2009 running yosemite 10.10.5 with this problem.  Here is a summary of what I have found.

     

    1.  People are often told to reset the pram and SMC but these rarely, if ever work.

    2.  Some have found that changing peripherals, such as the keyboard solves the problem, especially if the genius bar was unable to replicate the black screen when the computer was left with them.

    3.  If you use an adapter to plug in an external monitor and it works, your graphics card is not the source of the problem.  Be sure to been running the operating system, as the installation process, or apple hardware test do not drive the external monitor.

    4.  Apple hardware test (start and hit D) will usually not report a problem.  Some have reported the need to run the extended  test three times in a row, but I have not seen anyone reporting success through this method, and it did not work for me.

    5.  The problem is progressive and becomes worse over time.  Some have had success using the keyboard or hot corners to put the computer to sleep and wake it, to get the monitor to function but this only works for a while, and no longer works for me.

    6.  Some have reported success simply by detaching the video sync cable (the first cable you have to remove when opening up the iMac), but this did not work for me.  Leaving the sync cable detached did not cause any problems in running the system that I could note. Others have reported success by removing and reseating ALL of the cables inside the iMac.

    7.  Most, including me, get the best success by turning down the brightness of the monitor.  I can run for at least several hours with the brightness turned down, but the screen will black out almost instantly if I turn the brightness up beyond about 25%.

    8.  Some have reported success by replacing simply the LED control board, which is different from the graphics card.  This is the board that the video sync cable is attached to.  There is no actual backlight on LED displays so a failed backlight will not be the problem on this era of computer

    9.  Others have needed to replace or repair (see motorcycle Michael's post on this, above) the entire LG LED panel to solve the problem.

    10.  Some have been able to see the display by looking very carefully at the display while holding a strong light to it.  I am not sure what this tells you however.

    11.  Heat and cleaning the fans does not help me, but some have reported getting longer by installing a fan controller program.  Again, this did not work for me; No matter what the temperature, turning up the brightness will eventually lead to a black screen.

     

    So, as things are right now, according to the above, I either need to keep the display dimmed, replace the LED control board (also sometimes called the inventor board), or replace/repair the monitor.  I know of no way to determine which will solve the black screen problem on this iMac

  • by MarkusWinter,

    MarkusWinter MarkusWinter Oct 13, 2015 10:38 PM in response to Murrfk
    Level 1 (4 points)
    Oct 13, 2015 10:38 PM in response to Murrfk

    @Murrfk: About Point 10: if you can see the desktop then it is the backlight which is off, and the actual screen is not the problem.

  • by Murrfk,

    Murrfk Murrfk Oct 14, 2015 2:49 PM in response to MarkusWinter
    Level 1 (0 points)
    Oct 14, 2015 2:49 PM in response to MarkusWinter

    That might be true for the screens that have a backlight, but mine, being a LG LCD (I mistakenly typed LED in my previous post) does not have a backlight.  So perhaps the flashlight test is not useful for screens that don't have a backlight?

     

    Also, I did read where one person felt the problem was solved by removing incompatible memory, and I failed to mention that in my previous post.

  • by LondonLaurence,

    LondonLaurence LondonLaurence Oct 21, 2015 1:17 PM in response to LondonLaurence
    Level 1 (4 points)
    Oct 21, 2015 1:17 PM in response to LondonLaurence

    My display blackout issue (As per my above comment posted on 1 October 2015) has been diagnosed as a faulty LG LCD Display (LED strip)... Unfortunately not a cheap fix as the display unit needs replacing. I would guess that the majority of the screen blackout issues (Partial or intermittent) were probably caused by the same design/manufacturing issue with the LG LCD display.

  • by Murrfk,

    Murrfk Murrfk Oct 21, 2015 1:54 PM in response to LondonLaurence
    Level 1 (0 points)
    Oct 21, 2015 1:54 PM in response to LondonLaurence

    That would suggest that Motorcycle Michael's fix might be useful.  I haven't tried it yet, as I am kind of learning to live with it.

  • by Boomer49,

    Boomer49 Boomer49 Nov 14, 2015 5:33 PM in response to Murrfk
    Level 1 (15 points)
    Nov 14, 2015 5:33 PM in response to Murrfk

    Hi guys,

     

    The screen blacking-out started happening to me just yesterday. I could still hear faint mechanical sounds from within, so I know that the computer was still running. I was able to get the screen working again (for not too long) by unplugging the computer and then plugging it back in, and then restarting it. But the blacking-out situation would soon re-occur. I intuitively sensed that the screen was "shutting down" for self-preservation reasons, and tried lowering the brightness level to about 35% ... quite dim ... but if I nudged it up even a bit more ... click-blackness.

     

    I managed to read all 16 pages of this. Oh ****.

     

    But then I had a minor flash ... actually two flashes. It seemed to be putting itself into some kind of sleep mode, but a sleep mode from which it couldn't be awakened in the usual way. Somebody suggested adjusting the sleep timer to *never*. I had enough technical expertise to do that do that, and then I would  use the slowest smallest simplest darkest Screen Saver instead. But I was a Science teacher, and I started thinking back a day or two ... wondering what might have changed with the computer ... and I suddenly remembered that yesterday morning I'd had to replace the batteries in my wireless ... KEYBOARD! And at least two people in the thread had commented about switching-out keyboards! Hmmm ...

     

    So I turned off the computer. Removed the new batteries from the keyboard ... confirming that ... yes ... they were placed in correctly. I fired up the computer and returned the batteries and turned on the keyboard (which connected immediately) and boldly set the monitor's brightness to a very workable 50%. And that was 30 minutes ago.  in a coupe of days.

     

    Still goin' strong ...

     

    Two variables were monkeyed-around a bit, but the Screen Saver hasn't even had a chance to kick-in yet, so I am thinking that the simple disconnect/reconnect of the keyboard might have done something. Your mileage may vary, but it's worth a shot. I'll report-back in a couple of days.

  • by Boomer49,

    Boomer49 Boomer49 Nov 15, 2015 7:28 AM in response to Boomer49
    Level 1 (15 points)
    Nov 15, 2015 7:28 AM in response to Boomer49

    Well, it's morning now. The screen saver was working when I went to bed, but ... uh oh ... black screen is back. I restarted the computer and set the brightness back to about 48% and poof ... in three seconds the screen went black. I quickly restored it with keystrokes and rushed to turn down the brightness level but poof it would go black within a few seconds. So I turned off the computer and removed the keyboard batteries and restarted the computer. With the dead keyboard sitting here, I went to the brightness level and moved it to 50% ... in three seconds it goes black. Restart the computer and connect the keyboard and it loads in at 30%, but it's functioning. So now I'm gonna try to move the brightness to 45%, to see if I can duplicate last night's relative success. Fingers crossed. Here goes ...

     

    (To be continued ... )

  • by Boomer49,

    Boomer49 Boomer49 Nov 15, 2015 7:38 AM in response to Boomer49
    Level 1 (15 points)
    Nov 15, 2015 7:38 AM in response to Boomer49

    Well, as soon as I moved that brightness level the screen went black. I re-booted the computer again and it came to life with the brightness defaulting to 25%.

     

    Back to Square One. I wonder why my little fix worked for an hour last night.?

     

    Je me demande, "Qu'est qui se passe?"

  • by MarkusWinter,

    MarkusWinter MarkusWinter Nov 15, 2015 8:57 AM in response to Boomer49
    Level 1 (4 points)
    Nov 15, 2015 8:57 AM in response to Boomer49

    @Boomer49: it didn't. Our brains are build for detecting connections, so if an action is followed by an effect we quickly conclude that the effect was caused by the action. But often this isn't the case. That's why in Science you need at least three repeats before you trust a result, and even then others have to confirm it independently before it is accepted.

     

    Btw a LOT of superstitions arise from these false connections .

  • by Boomer49,

    Boomer49 Boomer49 Nov 15, 2015 12:36 PM in response to MarkusWinter
    Level 1 (15 points)
    Nov 15, 2015 12:36 PM in response to MarkusWinter

    Hmmmm .... just tried bumping the brightness from 25% to 35% three times and it blacked out immediately so I tried something I maybe read about yesterday ... I just jammed that effen slider to 100% as fast as possible ... and the screen is holding at 100% right now.

     

    Go big or go home. Let's see how long it works. It is now 1:35 on November 15th, 2015.

  • by Boomer49,

    Boomer49 Boomer49 Nov 15, 2015 6:48 PM in response to Boomer49
    Level 1 (15 points)
    Nov 15, 2015 6:48 PM in response to Boomer49

    It is 7:25 and heat is (as always) pouring out of the top of the iMac (as it has since I bought it a few years ago) ... the screen (at 100% brightness) gives-off the usual infrared warmth in this cool room ... BUT IT IS ALL STILL WORKING.

     

    Please just do what I did, and give feedback to this website.

     

    Here's what worked, at least for a day .... Before it goes black after nudging-up the brightness-control from 25% to some lame 45% on the Systems "Display" app ... doomed to fail ... be ready to just crank that ****** slider to the max 100 in a nano-second. Don't use the keyboard brightness keys.

     

    A day in ... and so far all is well ... the heat is pouring out of the top vents at the back of the screen (as it has for a few years) but ... so far so good.

     

    Them Apple engineers are not earning their keep. They maybe don't follow this **** on the Internet?

     

    There's no budget for catastrophic Apple failures like this?

     

    R

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