fiona.mac

Q: iMac 27" Black Screen?

For 6 long and painful weeks, my 27" iMac (10.7.5) has intermittently turned itself to sleep mode (black screen). It's driving me up the wall and sent my productivity through the floor. You'll be in the middle of something and whammo, black screen. I have to push the power button to get the screen to work again. It doesn't respond to keyboard or mouse.

 

The screen turns black when you're on the Internet, playing quicktime files, using Microsoft office, so it happens across different applications... it happens on my account, my daughter's account, the guest account. It is indiscriminate, it just does it whenever it feels like it, but not all the time. If it shuts down video, the audio still plays, there is just a black screen with no picture to watch.

 

The computer is 8 months old and I have Apple Protection as well, so that's not the problem, but I see other people have experienced a similar issue and I'm up for suggestions as to what you think might be causing the problem.

 

So far, these are the fixes that have been done and NOT fixed the problem:

 

  • OSX has been reinstalled twice
  • The logic Board has been replaced
  • RAM has been replaced
  • The graphics card has been replaced

 

The tech is coming back out Monday to replace the power supply and the screen. If this doesn't work I'm told I'll be reissued with a new machine.

 

So any other suggestions out there? Is it possessed by a ghost? Cursed? Just should be declared a lemon?

iMac, Mac OS X (10.7.5), Bought July 2012, Built mid 2011

Posted on May 2, 2013 9:56 PM

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Q: iMac 27" Black Screen?

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  • by scarlettr8,

    scarlettr8 scarlettr8 Jan 1, 2015 1:11 PM in response to fiona.mac
    Level 1 (0 points)
    Jan 1, 2015 1:11 PM in response to fiona.mac

    Same problem, random black screen, stated in Mavericks continues in Yosemite. Had the video card replaced (re: stbodie). Black screen returned after a week. Have tried all of the solutions mentioned in this thread, with the exception of having all of the wires re-plugged in. Appears Apple is just ignoring this issue.

  • by Guy Burns,

    Guy Burns Guy Burns Jan 22, 2015 9:39 AM in response to fiona.mac
    Level 2 (349 points)
    Applications
    Jan 22, 2015 9:39 AM in response to fiona.mac

    I'll throw in my two cents worth, untested. A friend rang me about this problem with his 27", mid 2011 iMac. Was unaware of this thread when I paid him a visit, but will be suggesting to him that if it is a software problem and something to do with controlling screen brightness, we should be trying Brightness Control, a small program which controls brightness.

     

    See http://www.macupdate.com/app/mac/10429/brightness-control

     

    I used it for years as a fully adjustable brightness control, not as a fix for the dark-screen problem.

  • by cyrano7,

    cyrano7 cyrano7 Jan 22, 2015 10:31 AM in response to Guy Burns
    Level 1 (1 points)
    Jan 22, 2015 10:31 AM in response to Guy Burns

    Thanks.

     

    Has anyone tried this yet?

  • by Guy Burns,

    Guy Burns Guy Burns Jan 22, 2015 6:11 PM in response to fiona.mac
    Level 2 (349 points)
    Applications
    Jan 22, 2015 6:11 PM in response to fiona.mac

    This problem has got me – and Apple and their technicians – intrigued because of the variety of so-called fixes. After talking to Apple (Sydney) and the local tech for about an hour, this is how I understand matters:

     

    1. The fault is not directly software related. Nothing to do with suspect code, except if the code somehow affects (in a significant way) a physical attribute inside the computer, such as voltage, current, or electromagnetic radiation (EMR), and that change in attribute causes the fault to occur. Brightness variation is just such a change because voltage levels undergo significant variation as brightness is altered. But the code itself cannot be blamed.
    2. Not directly related to heat, either. The tech stated that the fault is more likely to occur cold. As an example, he blocked up the vents while testing a particular machine, ran a processing task that consumed all the CPU power, and watched while the Processor Temperature Diode (I think) ran up to 98º – but no fault. He also runs cold tests.
    3. Could be related to the amount of EMR being emitted in certain areas of the video card. He gave an example (from his radio repair days) of a copper track making a right-angle bend on a circuit board. At the sharp point, radiation will be emitted much like from an antenna. The amount of such radiation will depend on voltage, current, and frequency of signals on the track, and may affect – cause arcing – in areas close by.
    4. Apple's engineers may have an inkling of what the problem is, but if they do they are not sharing the info with technicians in Australia. The particular tech I was talking with has been pushing Apple for more info, and offering them as much info as he can, but in his words: "I've pushed and pushed, but until Apple engineers find what the problem is – nothing". He is still pretty much working in the dark regarding this fault. i.e. there is no definite fix as yet that points to a definite connector/component/track/whatever. They fix mostly by changing the video card, but other fixes can also appear to work.
    5. Apple may not give the go ahead for repair until the problem is seen to occur AND the problem is detected by an Apple on-line diagnostic program, something called VST on the Apple Diagnostic Server. The tech hooks up the faulty computer, and based on the serial number of the computer a specific test is run.
    6. It is possible that the computer can be faulty, but the fault not be picked up by the diagnostic test. From Apple's point of view that creates a problem. They would like to be able to fix the fault (which at the moment can't reliably be detected) by a defined series of steps (do this, do that), otherwise they are inefficiently spending money on repairs. But they also want to keep their customers happy. I can understand Apple's point of view. If the problem hasn't been definitely located, it is not sensible for Apple to simply replace all video cards on the off chance the problem may be fixed.
    7. The tech said he is getting better at the diagnosis, but he still has to see the fault occur and have it detected diagnostically. He can't repair until Apple gives the go ahead.
    8. Supporting evidence by means of a video of the fault occurring, preferably several in short succession, is good evidence which Apple may accept in lieu of the diagnostic test.
    9. Affected computers are subject to a worldwide recall, iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support

     

    To sum up: by all means experiment with various software fixes, but none of them go to the core of the problem. The problem is in hardware, but software can appear to fix the problem if the software changes some attribute (voltage, current, EMR), in a way that may be different from another piece of software trying to do the same thing.

  • by scarlettr8,

    scarlettr8 scarlettr8 Jan 22, 2015 6:54 PM in response to scarlettr8
    Level 1 (0 points)
    Jan 22, 2015 6:54 PM in response to scarlettr8

    An update, after trying everything I've read about this issue online, I finally solved it by installing the Owly app. Works beautifully, no black screen (hope I didn't just jinx myself)  for 3 weeks.

  • by Chicago Dude,

    Chicago Dude Chicago Dude Jan 23, 2015 9:28 AM in response to fiona.mac
    Level 1 (0 points)
    Jan 23, 2015 9:28 AM in response to fiona.mac

    I have a solution that worked for me!!  But first some background.

     

    I have been dealing with the screen on my iMac 27" (Mid 2011) for several months now.  In the beginning it would randomly just go dark and I could not get it to come alive without shutting it down and restarting.  I soon realized that it was only the screen that was shutting down, since certain key strokes produced a sound (e.g., command-shift-escape).  So then I found that if I clicked the power button a few times, then I would get the logging on screen.  I reset the PRAM, etc, but no help.  I called Apple support and they recommended fixing everything in Disk Utilities (permissions, repair disk), but that did not improve things.  I was then using Mountain Lion and they strongly recommended updating to Yosemite.  I eventually did but things actually got worse.   I changed my security setting to "require password after 1 minute" so that I would not have to log in after every dark screen episode. 

     

    After reading many blogs, there was much discussion about heat being the cause.  While the screen was bright, I put my hand over the vents and found that every time I put my hand over the middle part of the screen (back of the iMac, near the top), the screen would go black within a few seconds.  Clearly, blocking the airflow raised the temperature sufficiently that it caused the system to shut down.  You should try this!

     

    Solution:  As suggested by someone in one of the blogs, I installed "smc Fan Control", a freeware utility that allows you to increase the default fan speed for the three fans that are evidently in the iMac.  The utility showed that the internal temperature of my mac was 49 °C (120 °F), which seems quite hot.  I set the speeds of the three fans to ca. 2000 and within 15 minutes the temperature had come down to 39 °C (102 °F), still warm, but much better.  Since doing this, the computer had not gone dark on me.  I should note that even at this temperature, if I block the central part of the vent slot, the computer will go dark within a few seconds.  So, as long as I don't do this, I can now use my computer without the dreaded black screen.

  • by cyrano7,

    cyrano7 cyrano7 Jan 23, 2015 12:04 PM in response to Chicago Dude
    Level 1 (1 points)
    Jan 23, 2015 12:04 PM in response to Chicago Dude

    What about just pointing an 8 inch fan on the back of the computer. It seems that would have the same effect. I tried that but nothing.

     

    Now, my screen stays on for only seconds before going black, no matter how low the dimmer settings.

     

    I'm using an external monitor in mirror display to use my late 2009 iMac 27.

  • by cyrano7,

    cyrano7 cyrano7 Jan 29, 2015 12:28 AM in response to cyrano7
    Level 1 (1 points)
    Jan 29, 2015 12:28 AM in response to cyrano7

    Well this is strange, and may be good. I was minutes away from going to shell out $500 to get the LED display on my late 2009 27 iMac replaced, and I decided to give it one last try.

     

    I hooked up the 27 as an external monitor to my 24 iMac via the mini displayport cable.

     

    After being black for 4 months, the darn 27 monitor works! It works as an external display. Which means the monitor is probably not defective.

     

    What does this mean?  Thanks.

  • by Guy Burns,

    Guy Burns Guy Burns Jan 29, 2015 2:53 AM in response to cyrano7
    Level 2 (349 points)
    Applications
    Jan 29, 2015 2:53 AM in response to cyrano7

    Says to me: faulty internal connection somewhere.

     

    I've had my friend's mid-2011 27" iMac for a week now, trying to pinpoint the problem. It's subject to the recall, but the local Apple tech and I agreed that until we can reliably trigger the fault, it's best not to send it for repair just yet.

     

    Another interesting thing: when this particular machine goes black screen, it can always be fixed by Opt-Cmd-Eject which puts the machine to sleep. Now, sometimes after about 5 seconds the machine automatically comes out of sleep, all by itself, and the screen is okay. But other times, I have to Opt-Cmd-Eject a second time.

     

    The tech couldn't explain this behaviour. What could be the explanation of a machine in sleep mode, coming out of sleep by itself?

     

    Also, I'm thinking of starting a new thread: not how to fix the fault, but how to induce it. If the fault can be reliably induced, it can be fixed.

  • by stevefromfiley,

    stevefromfiley stevefromfiley Jan 29, 2015 3:24 AM in response to Guy Burns
    Level 1 (4 points)
    Jan 29, 2015 3:24 AM in response to Guy Burns

    I have used the Opt-Cmd-Eject method and the screen comes back on,when my Mac was at its worse i would Opt-Cmd-Eject and then within a second it would black screen again.

    As i explained the other day mine is now fine as long as i keep the brightness on 3 blocks,anymore and it black screens instantly.

    Not forgetting i am running Mavericks which is very stable,i tried to upgrade to Yosemite last week and after a while of using it,the black screens came back big time!!!


  • by cyrano7,

    cyrano7 cyrano7 Jan 29, 2015 12:22 PM in response to stevefromfiley
    Level 1 (1 points)
    Jan 29, 2015 12:22 PM in response to stevefromfiley

    My monitor had that exact same problem.

    If brightness went above 50% it went black. Then 40%. Then 30%. Then it would come on for only seconds and go black.

    Now, it works just fine as an external monitor.

     

    2 months ago I took it to the Apple repair shop and then another place. They both checked or changed something that cost about $200 (graphics card? blah blah panel, board?) , and returned the Mac to me, but both times the black monitor returned.

     

    But the monitor DOES WORK as an external display.

  • by cyrano7,

    cyrano7 cyrano7 Jan 29, 2015 12:40 PM in response to cyrano7
    Level 1 (1 points)
    Jan 29, 2015 12:40 PM in response to cyrano7

    And this just occurred to me.

     

    My 27 iMac works as a monitor for my 24 iMac. But it does not work as a monitor for itself.

     

    However, and oddly. The 27 iMac will send it signal to an external monitor.

     

    The brains of the 27 will show visual to from another computer. And to another computer. But it will now show visuals on itself.

  • by andyvj,

    andyvj andyvj Mar 12, 2015 1:17 PM in response to cyrano7
    Level 1 (1 points)
    Mar 12, 2015 1:17 PM in response to cyrano7

    hi guys

    I'm having this problem as well.. it's started this week about Tuesday

    I've been told it could be "adware" and cleanmymac" and even that its my logic board battery.

    so here goes.

    i run SSD Fan control

    Owly app

    using a usb keyboard (a knackered one for the time been)

    only using  track and a wacom one tablet

    disconnected my bluetooth mouse from my iMac in the other room and other things related

    i do have all the plugs filled at the back of the iMac

    will give it a go

    and report back

  • by Eprom,

    Eprom Eprom Mar 25, 2015 7:59 AM in response to andyvj
    Level 1 (0 points)
    Mar 25, 2015 7:59 AM in response to andyvj

    You can add me to the list!

    Since last week I too have a black screen on my 27" 2011 iMac. I have tried all the tips here; fan control, keyboard, singel user, etc. I did a clean install of Yosemite twice and also tried starting up from an external drive, but after just a few seconds my Mac goes black. Connected an extra monitor and that keeps working even if the iMac's screen goes black.

    But now for the weird thing: if I start up Bootcamp, the Imac screen is working perfectly!!!

     

    So, it looks like OSX is putting the screen to sleep for some reason, but why is it still doing that after a clean install?

  • by jhnmorely,

    jhnmorely jhnmorely Apr 2, 2015 5:49 PM in response to Eprom
    Level 1 (0 points)
    Apr 2, 2015 5:49 PM in response to Eprom

    I have had problems recently with the white screen of death.  I have a 27 inch iMac, from 2012.

     

    Last September or so I started having keyboard problems.  I was getting strange characters when I tried to type.  I had an Apple wireless keyboard. Apple suggested it might be a software problem.  I remembered that I might have leaned my elbow on part of the keyboard and damaged some of the keys. So I bought an apple USB keyboard.  The keyboard came with an extra USB cable, but I did not use it, since the cable coming out of the keyboard  was long enough to reach the back of the monitor. The new USB keyboard fixed my problem with inputting characters; however, sometimes on booting up the keyboard would not work at all when I tried to input my password.  I read that some users had had this problem and fixed it by just plugging in the keyboard cable USB connector in another USB slot on the back of the monitor.  This solution worked for me.  Sometimes I would have to boot up one or two more times and try another USB connection slot. After two-three times I was able to input my password and get to my documents, etc.

     

    Last month I had my first experience of the white screen of death. While I was using Power Point, the screen flickered, and then went completely white. The machine would start up, but would never boot past the apple logo. I tried various keyboard commands suggested by apple support and by users, such as Safe Boot, Command-R, Shift, etc., but none seemed to work. I tried DiskWarrior and it may have helped.  I set aside my computer for a couple of days and worked on a laptop. A few days later a login screen appeared on my desktop, and I was able to login.   However, after two-three days the machine flickered again, this time in a checkerboard pattern, and went out, back to the white screen of death. In trying to deal with this problem, I had read in user support comments that the Command and Option keys on the right side of the keyboard should be used, not the ones on the left side, which I had been using. The right-side Command key plus r got me this time to Disk Utility.  I verified my disks, and there were no problems found.   I still found that sometimes in logging in, the keyboard input would go dead, and I could not input my password.  Changing the USB slot helped a few times, but then it didn't.  Thanks to apple support users, I had also read that the Apple keyboard USB connector on the cable coming out of the keyboard sometimes had weak connections with the USB slots on the back of the iMac. So I tried the extra USB cable that came with the keyboard. I connected the keyboard cable connector to the extra USB cable and then connected the extra USB cable to the a USB slot on the back of the iMac. This  worked. I was able to login, and I have been using my iMac for two-three days so far without any flickering screens and crashes.  I keep it in Sleep mode so I will not have to boot up.  

     

    I do not know if this is just a temporary fix or not. Anyway, two take-aways would seem to be:

    1) Use the Command key on the right side of the keyboard + r to get past the white screen of death to Disk Utility  and

    2) Check your USB connections from the keyboard to the monitor and use the extra cable that comes with the apple usb keyboard  

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