iMac 27" Black Screen?

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　　

You can add me to the list too.. Unfortunately.

10- 15 minutes ago black screen with a cursor fail had happened to my computer.

But different from other users, after restart from button my computer started working...

But after a quick search I stated that is a common and urgent matter to all apple users.

And I think not for apple comp.. Sadly.

After selling most expensive hardware on the market around the world, they have to

solve our problems so as their products problems rapidly. 2013 to 2015 there is a

great deal of time to diagonise the problem and fix it both software and hardware

part of product.

I will check it regularly from now on.

(Sorry for my bad english.)

UPDATE

Even though my iMac was bought in 2011, Apple was so kind to replace the complete display + backlight and everything works fine again. 🙂

Mine stayed good for 7 months after setting the monitor on FULL brightness and not one block less. unfotunatly today it occurred again one time. 😠

Im not sure how it wil develop now but setting it on full brightness was at least good for a very descent time.

Loose connection somewhere is my best guess. A friend asked me to look into his problem, so I went to have a look. Bad – after the first hour problem free, it occurred every few minutes and became unusable. Took it home with me, and the problem disappeared. Returned it to him, and it was okay for a few months, then got so bad he put the computer in the car to take to Apple. Was unable to deliver that day, so used it that night. No problems. Good for another several weeks. Then got bad again.

How else to explain that moving the computer can fix the problem, other than a loose connection?

Also, mine has never displayed the problem, but maybe once in 20 turn-ons I can hear an arcing noise for half a second. Don't know where it's coming from (could be the mains cable). The screen's never gone black but I'm thinking: there's a loose connection somewhere in my machine. I wonder if it's to do with the black screen problem?

Try Preferences Bluetooth Advanced and Uncheck "Allow Bluetooth devices to wake this computer "

I tried this and it has worked for a few days. And counting

For want of a better metaphor, it seems that the innards of the computer have only a tenuous grasp on the monitor. So, I set the desktop to change images every minute, and the screen saver to slow slides. Logic might say that this allows the brains to exert continuous control over the monitor and thus prevent it from lapsing.

Anyway, that is my logic, and my latest attempt to keep the monitor from going black.

OK I think I fixed it! Go to the display options, and turn of auto dimming. I think it's that dimming sensor that is faulty from being used over the years. In most cases, the computer is still on after the screen turns black, so that means just the computer screen is off.

You just have to manually control the brightness with the keyboard now.

A) thanks.

B) could you be real specific (but simple) about where to find the "auto dimming"? I have a late 2009 27 iMac, using Mavericks, and I don's see it when I open up displays.

Thanks.

go to 'system preferences', 'Displays', and uncheck 'automatically adjust display brightness'. Unless you don't have this functionality on your mac?

I don't appear to have that functionality. I just have basic choices of DISPLAY, COLOR, RESOLUTION, SCALED, and SHOW MIRRORING OPTIONS.

I have an early 2009 24 inch on Mavericks, and a late 2009 27 inch on Yosemite. Neither one shows that functionality.

(the 27 is the one with the black screen problem)

?

I am a new black screen sufferer. Let me share the detail briefly. 27" iMac vintage 2011. Dragged it in to the local store a few weeks ago. They could not replicate fault despite running tests and having the machine on test for 18 hours so they handed it back. It was no better when I set it up again and I tried many of the suggestions on this thread. It got to a point when it was going black on start up before reaching the login screen. Dragged it back to the store and this time the fault repeated itself on the service counter so they said they would replace the video card (quoting UK consumer law but in actual fact Apple had already issued a notice on this particular video card in this manufacturing batch of machine). I got a call from the store asking if it was OK to clear down the HD and reload the operating system suggesting that installing a new video card had not cleared the black screen fault. I ok'ed this and picked the unit up last week. After 2 hours of use the fault has returned. I plan to couple the unit up to a second monitor to confirm it is just the video component dropping out (which seems to be confirmed by other people commenting on this issue) prior to returning to the Apple Store for the third (and last) time. Personally I think it disgraceful that a business this big with as much income as they generate cannot fix this problem effectively.

Here is an update to yesterday's post. Finished last night restarting the iMac after the black screen kept reappearing seconds after clearing via Cmd-Alt-Eject but couldn't get to the login screen before going black again. 8 hours later it booted normally. Connected to a second monitor and waited for the first black screen which came about 1/2 hour later but the second monitor stayed on playing YouTube. Downloaded Owly but the black screens continued periodically. Dropped the main screen brightness to 2 bars and black screens stopped appearing over a couple of hours. Added one bar to the screen intensity and got an immediate black screen. Went back to 2 bars and again ran without blackouts for a couple of hours. Decided to eliminate the wired keyboard as a cause so disconnected and used the mouse on preferences to increase intensity slightly and got an immediate black screen so recoupled keyboard and went back to 2 bars and again stability returned. Temperature monitoring shows GPU diode at 149 F, GPU heat sink at 138 F and CPU Core at 99 F and casing is warm but not boiling hot. The graphics card is new from last week and based on other posts the temperatures at not high. After several hours of playing YouTube videos I seem to have stability at 2 bars intensity and immediate black screen if I go over 2 bars. Anyone got a concrete cause for this? My next step is to upgrade from Mavericks to Yosemite after which it is either back to Apple store or live with 2 bar screen brightness until it goes phut completely.

Billymick wrote:

Here is an update to yesterday's post. Finished last night restarting the iMac after the black screen kept reappearing seconds after clearing via Cmd-Alt-Eject but couldn't get to the login screen before going black again. 8 hours later it booted normally. Connected to a second monitor and waited for the first black screen which came about 1/2 hour later but the second monitor stayed on playing YouTube. Downloaded Owly but the black screens continued periodically. Dropped the main screen brightness to 2 bars and black screens stopped appearing over a couple of hours. Added one bar to the screen intensity and got an immediate black screen. Went back to 2 bars and again ran without blackouts for a couple of hours. Decided to eliminate the wired keyboard as a cause so disconnected and used the mouse on preferences to increase intensity slightly and got an immediate black screen so recoupled keyboard and went back to 2 bars and again stability returned. Temperature monitoring shows GPU diode at 149 F, GPU heat sink at 138 F and CPU Core at 99 F and casing is warm but not boiling hot. The graphics card is new from last week and based on other posts the temperatures at not high. After several hours of playing YouTube videos I seem to have stability at 2 bars intensity and immediate black screen if I go over 2 bars. Anyone got a concrete cause for this? My next step is to upgrade from Mavericks to Yosemite after which it is either back to Apple store or live with 2 bar screen brightness until it goes phut completely.

Upgrading OS X WILL NOT solve your issue, doing so will only make troubleshooting your problem much more difficult. If you had the computer serviced at an Apple Store, take it back immediately!

I'm dealing with the same issue. My computer is a 27" 2012 iMac with the 6970M graphics card. Everything was great until a month ago when randomly my iMac would flicker and go black. I have an external monitor hooked up to the device and this monitor always stays on when I'm experiencing the issue. Eventually the iMac screen comes back, sometimes its a few minutes other times its like an hour. Usually it goes black out of sleep when it does happen.

I took my computer to the store to have them look at it and they ran a bunch of test one of them being a VST test which it passed. The tech told me to have the faulty video card replaced it would have to fail the VST test 😟. After she ran more test I got a chance to try and show her the issue. We booted the computer to my drive and put it to sleep, no issues. We put it to sleep a second time and sure enough the iMac did not come up, the external display come up fine. After a couple of minutes the iMac came back up which is what I've been experiencing.

So will see how things turn out but I'm getting concerned about the iMac passing the VST test even though the tech saw the issue first hand.