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

Hi Boomer and All,

Thanks for the put it up to 100% suggestion. My screen will only stay on it seems at 100% or at the lowest setting! My hard drive crashed on my iMac 27" mid 2011 (2.7GHz Intel Core i5 with AMD Radeon HD 6770M 512MB graphics card - not eligible for the video card program it seems) and i took it in to have a new one installed, and figured I would have my backlight issue addressed as well. For 6 months the right side of my screen would occasionally go dark, without rhyme or reason. The shop said the backlight card needed to be changed, which they did, but then after bringing it home and running it for a day, it started going completely dark. I took it back in, thinking it was a defective backlight board, and they changed the card for another one, but the problem continued. I am going through this thread trying things ... I tried the mfacci solution(PRAM reset, then Setup Manager - Dec 19 2015), but that did not resolve the problem 😟 Still fishing for a solution ... but at least I know I can use it at 100%! Way better than the lowest brightness setting 🙂 Would be nice for to have the option of an in between setting though!

So I brought my computer into the Apple store. .got a new hard drive and when I was updating the drive from Time Machine the screen kept going black. unable to wake it up using the keyboard; the only thing that worked was pressing the on/off button..

Finally got everything up and running; set on 80% to test whether it's going to black out on me again.

Late 2009 27" iMac (Intel Duo Core); .........I love my iMac but straight out of the box, I had a firmware issue that caused the screen to flicker black. It took Apple several months to figure it out and send out a firmware update. Then, the hard-drive crashed back in 2012 or 2013-ish. Apple generously replaced it at no cost after a recall due to a factory defect in my particular model; however, my CD/DVD drive and iPhoto stopped working when they returned it to me. (Now I've realized I can't reinstall Snow Leopard without CD optical drive working properly....... so there's a problem). Anyway, I was ironically looking to upgrade my RAM when the screen started going black. I have to put the computer into sleep mode and then wake it for the screen / light to return. All applications still run in the background, though. This just started within the past few days.

Like most everyone else on this board, I'm looking for a real fix.

For those who've had this issue and then replaced the RAM, has the blackout gone away?

I tried replacing my ram and it did not help the problem. I have to run at 100% backlight or the lowest. If I change it to anything else it blacks out. Late 2009 Imac 27in. I have also replaced the video card, backlight driver board, and recently upgraded to a SSD drive.

Mid 2010 27" iMac. I haven't replaced the RAM or anything else.

I do have to run at 100% brightness.

The blacking out problem comes and goes. OK for weeks, then suddenly it starts happening again. I also have issues with the AppStore not loading up sometimes and CreativeCloud mini app not loading up. Sometimes when there are updates available, the screen starts blacking out again.

I'm not technical, but I do see patterns emerge. I'm pretty sure there is a software conflict happening. The fact that a reboot often fixes it suggests it isn't hardware.

I do highly recommend using the "ctrl + cmd + eject button, then any key" trick to wake up the screen again. If that fails, reboot in safe mode (hold down the shift key immediately you hear the start up tone) and make sure AppleStore and Adobe updates have all been completed. Uncheck startup at login on non-essentials. Then restart. If that works, you know it's a software issue.

Most recently my screen went highly unstable – pages and websites were loading in multi passes and the dock graphics went all wobbly. Nothing would stay fixed. I thought it was my graphics card. Then it went permanently black.

I started up in safe mode twice before it miraculously ....touch wood ...seemed to recover to normal function.

I have no idea why. All I can say is, don't rush out and spend a fortune on replacements until you've exhausted all other possibilities.

Wow, whodathunkit? It turns out it was brightness. 😮 SO WEIRD and I hope I'm not invoking Murphy's Law... but it started blacking out when it was on 100% brightness. That's why I turned it down to 60%. I had just moved my computer and plugged my USB infrared mouse into a different socket when the blacking out started. ANYWAY I unplugged all my USB's, rebooted my iMac, then plugged my mouse into its original socket and turned the brightness back up to 100%. I haven't had a black screen for 2 days.

LONG-TERM FIX and SOLUTION: If you've read this far and still haven't been able to fix your screen from going black, please go back to Page 8 and reread this post by Motorcycle Michael, and subsequent responses by him and pbook4g5.

I've been following this thread for several years as my screen has exhibited this problem on and off. I've tried many of the suggestions that were logical, including installing smcFanControl (heat issues) and reseating and cleaning each plug inside the computer with electrical contact cleaner (connection issues). None of these solutions provided a long-term solution. I didn't even try reinstalling the OS (it's not a software problem), or zapping the PRAM and all the other voodoo suggestions (illogical conclusions).

My black screen continued to get worse to the point where lowering the brightness to zero was the only way to keep the screen alive. As a designer and photographer, I needed to see my image and could no longer rely on the histogram alone. It was time for a real solution.

That's when I stumbled upon Motorcycle Michael's solution. It not only makes sense, it works.

The culprit are two bad connectors on the LG display itself. Disconnecting, cleaning, and reseating the two connectors instantly solved the issue and I've been running 100% brightness for two weeks 16+hours a day (I work from home).

Here's a recap of Motorcycle Michael's solution:

1. Open the case and very carefully disconnect the four connectors from the back of the screen. Here's a great tutorial to walk you through the process: https://youtu.be/xfP9mRlwYFI (only the first 3 minutes apply).
2. Place the screen face down on a soft surface such as a bath towel.
3. Locate the two ribbon cables on the back of the screen that extend from the middle of the screen, to the edge, then to two of the corners.
4. At each of the two corners, carefully peal back the silver metallic tape to expose a cloth tape, which you need to peal back. This will expose the ribbon cable and connector.
5. The connector is held in the socket by a white plastic retainer clip. Unfortunately, the tabs must be broken off to remove the socket. This can be done with a screwdriver or long-nose pliers. This step is irreversible.
6. Remove the plug. Insert and remove the plug several times to "clean" the metal contacts.
   PLEASE NOTE: If you use contact cleaner, DO NOT spray into the socket. Only spray the plug. Why? The cleaner will leak into the display and appear on the inside surface of the screen, which creates a blob on the screen - which you will see the next time you power on. Fortunately, the blob will eventually evaporate (1-2 hours) - but it can be frightening until it does.
7. Motorcycle Michael suggested adding a thin plastic wedge to help the plug to maintain contact, or using a dab of silicon dielectric compound. I did neither of these suggestions, as I felt confident the tape that was pealed back earlier would hold it just fine.
8. Place the tape back over the ribbon cable and reassemble your computer in the opposite order you took it apart.
   SIDE NOTE: Since you already have the case open, consider cleaning the dust buildup around the fans, duct work, and grill along the bottom edge. A can of compressed air would do the trick.

I would like to publicly thank both Motorcycle Michael and pbook4g5 for adding their experience and solution to this discussion. It was pbook4g5 that convinced me that it was the connection on the display itself. If you read his posts, you will see he followed the same replacement procedure prescribed by the Apple Tech Manual (which he owns for this model). pbook4g5 indirectly proved Motorcycle Michael's solution since his replacement screen would have had a newer connector.

If you try this repair and it provided a permanent solution to your black screen problem, please share your success story so others can learn and benefit from this solution.

Lastly, if this repair does not provide a 100% long-term solution for myself, I will provide a follow-up post stating so.

I too have this issue.

I would like to start by saying I have the Mid 2010 I5 2.8 Imac 27 inch (11,3).

Initially running Snow Leopard (and updating as new OS's became available) the machine ran beautifully for several years, often without any sort of break for months at a time.

Eventually the black screen issue raised it's ugly head.

I have tried resetting the PRAM and SMC...at times they seem to have given some relief but not permanent.

I tried removing / replugging the RAM (genuine Apple 4 x 2GB).

Tried the brightness adjustments.

Tried turning off the sleep and power saving.

When the problem manifests itself, by connecting a TV set via the socket on the rear of the Imac, I can see the screen (video card is working, as is everything but the inbuilt display).

Yes, if I use a bright torch at a certain angle, there is activity of sorts on the screen.

My internal hard drive reported as failing, so I took the machine to a local shop to replace it and to add a SSD for performance enhancement.

The tech there suggested the black screen was caused by the display itself being kaput and that there was nothing he could do unless I wished to spend the $$$ for a complete new display panel.

I have fixed many PC's (though this is my first mac)... and stubborn fellow that I am I took it home, plugged in a USB HDD and installed the Snow Leopard to the remote HDD from the DVD that came in the Imac box.

Well, "bob's yer uncle", I am typing this now from this same machine and not one (tempts fate hugely.. 😉 ) blackout.

This suggests to me a symptom of the failing hard drive (maybe)...but read on.

I have previously performed these steps and run the machine for weeks from the little Toshiba 1TB USB.

Flawlessly.

Then I updated the OS via the internet and still going well....until..I'm not quite sure which of these possible scenarios brought me back to square one.

A:I installed the latest version of Flash..."ALL4" or "ITV Hub" were demanding it and at one stage, twice trying to use these (TV streaming) provoked an immediate black screen.

B:Also installed AVG free anti-virus & Google Chrome, but I'm leaning toward the Flash install as it is related to video performance.

In no time flat ugly, ugly scenes (which of course I couldn't see, the screen was black!).

So, complete format of the USB drive, reinstall Snow Leopard and voila, no problemo (again)...like, straight away, back to running fine. My next course of action will be to replace the Snow Leopard install with El Capitan again (but no Flash install this time) and test before springing for and installing a new internal drive (HDD or SSD). I must do some more reading about kext files, I'm of the opinion (as was one of the earlier posters) that these are being corrupted somehow by one of the software changes I'm making...

If (when?) I come up with an answer, I will of course return and share.

Thanks to ALL the previous posters for your collective efforts to cure what WE know can be a maddening problem with what is otherwise the finest computer I have owned.

OK. I have applied several updates including a cumulative OS update which has brought me to 10.6.8 and still no probs. I will continue to incrementally update rather than clean install in the hopes of preserving the original video drivers. Still no Flash.

So, the machine invited me to update to El Capitan, which I did by first downloading and then installing. Well, straight back to black screen 😟...managed to get a lookin for only a few moments and noticed a large ? mark in the dock which upon hovering, discovered relates to the El Capitan. I would give more info but BLACK SCREEN again...arrrgghh. Rebooting leads me to the grey screen with no cursor. Repeated efforts have lead me to a nice looking El Cap screen with the ? mark on the dock and.....oh oh...black again.

Is this solution still working ?

Our Late 2009 iMac (10.1) had this issue too (random black screen, not found bootable disk / question mark, white screen). Tried several SMC and PRAM reset, boot in recovery mode and Disk Utility First Aid (as I had installed an OWC SSD disk 2 years ago).

Also installed macOS Sierra, and also a clear harddisk, and again complete installation of macOS Sierra and restore from TimeMachine (12 hours) but problem still persist.

Finally I found a article over defect Magic Keyboard - so I was lucky we had a (thai) keyboard as spare, connected by bluetooth and Voila it works!

Now my daughter is doing a stress test, and going steady for 1 hour so I am optimistic this is the fix!

Our Late 2009 iMac (10.1) had this issue too (random black screen, not found bootable disk / question mark, white screen), started after a recent El Capitan update

Tried several SMC and PRAM reset, boot in recovery mode and Disk Utility First Aid (2 years ago I had installed an OWC Mercury Electra 6G SSD).

Also installed macOS Sierra, and also a clear harddisk, and again complete installation of macOS Sierra and restore from TimeMachine (12 hours) but problem still persist.

Whenever the screen goes black, I could connect it by Target Display Mode (⌘ F2) to a MacBookPro, and when I closed that Target Display Mode session the screen worked normal for some minutes.

Finally I found a suggestion to replace the Magic Keyboard - and I was lucky we had a (thai) keyboard as spare, connected by bluetooth and Voila it works!

http://forums.macrumors.com/threads/imac-screen-goes-black-must-hard-reboot-help .1375427/page-2#post-21660024

Now my daughter is doing a stress test, and going steady for 2 hours so I am optimistic this is the fix!

(sorry for posting twice, could not save my update/edit)

Hi, since i 1 Month i have the same Display issue with my 2010 27' imac.

I have already tried literally everything software related.

Is the display issue still gone on you imac since the "repair"?

I'm thinking about trying this too.

Yes, my repair of replacing the screen with one that has updated connectors is still holding great after many years. The screen has never turned dark again. My 2009 27"iMac is now being used as a secondary display for my new 5k iMac and it works great.