Random Black screen, Help please

have you tried resetting PRAM?:

Shut down the computer.

Turn on the computer.

Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.

Hold the keys down until the computer restarts and you hear the startup sound for the second time (I usually let it do this till it chimes 3 times).

Release the keys.

I have the issue with 'Black Screen' on my late 2010 27-inch iMac. Boots up fine, but then randomly goes black. The iMac is still alive as I can still hear things playing. Someone suggested I try putting the iMac to sleep using the cmd/alt/eject key commends. Well I tried this, and after doing the key commends then touching any key afterwards the iMac came back. Screen came back on. It did however go off again after a couple of minutes, but used the same tactics again and it worked again. Still a pain, but a solution.

Hi Gerald, my advice is try replacing the keyboard.

I had this problem and have spent weeks trying to fix it, using every suggested fix on every forum I could find. I did endless PRAM and SMC resets, installed smc fancontrol, uninstalled and reinstalled Yosemite. Every fix failed. In fact it just got worse.

My 2008 imac had become virtually unusable. As soon as it powered up the screen went black, and it sometimes got stuck in a loop of trying to restart and would only stop if I unplugged the machine from the wall.

Then I read that someone had fixed this by replacing the keyboard. I had nothing left to try, so tried it.

It worked. Everything is back to normal. No screen glitches at all. It's like a miracle cure.

I hope it works for you too :)

Double check your System Pref > Desktop & Screen Saver settings.

Try changing the screen saver to something else and also check your Hot Corner settings. You could also have "Put Display Asleep" set for a corner.

In the left top corner of the screen is a flat wire . Make sure it is properly seated.

It can come lose when the hard drive is replaced, and maybe you did not properly seat it back. The mac starts up, but as soon as the kernel loads it dims the screen, and then turns the screen off.

Interestingly, when I try to reboot the mac by holding the power button pressed, it would flash the screen. Apparently the power button briefly over ride the kernel control of the screen.

hold Shift + D simultaneously while holding the power key (to turn on the mac) for 10 or 15 seconds. Seems to work anytime it's necessary, which for me has been only after system updates in el capitan.

I had the black screen appear after installing office for mac - reinstalling OSX fixed the problem.

I reinstalled OSX and iMac works fine now. Simples.

What works for me perfectly since almost one year is simply to set the brightness of the screen to maximum and disable the automatic brightness control (I don’t know how it’s exactly called in english, I’m translating directly from german. However it’s the checkbox below the slider for brightness).

I have an iMac Mid 2011 and the problem of the screen randomly going black occured a year ago. It went black but the iMac was still working, like when I had music on it still played. I couldn’t awake the screen with my keyboard or mouse, only by pressing the power button for short and then the iMac went into silent mode and then pressing the power button again the screen came back, but very often only for a few minutes before it got black again.

I was doing a very hard research over two days and tried everything recommended. Finally the above described solution by setting the brightness to maximum worked for me (I’ve also read that for some dimming the brightness works). Since then the screen doesn’t go black anymore. I sometimes got anxious when I accidently touched the dimming key on my apple keyboard, like when I removed dust from the keyboard and the screen went black again. Fortunately I understood what has happened and set the brightness to maximum again. I can’t explain what exactly is causing this issue, if it’s a software bug or some dust covering a sensor inside the Mac. I guess there are also different reasons for the screen randomly going black and it might not work on every Mac, but give it a try.

What I’ve recently read and makes sense to me, is that some sensors (like for temperature) are covered with dust, don’t work properly and are causing the screen to go black. Try to clean the inside of your Mac with compressed air, before you hand your Mac to the Apple store for reparations.

This worked for me on my 2011 iMac 27” High Sierra:

https://mac-how-to.gadgethacks.com/how-t...

If you’re afraid to click the link just type in “Mac caffeinate” and this page should pop up as one of the first ones. It worked great for me. And believe me I’ve spent hours trying to figure it out and tried everything. So far, mine’s still going without any problem at full brightness after cancelling the caffeinate program, putting the Mac to sleep and waking it up several hours later. HOOAH!!!

I had the same problem and the fix was easy. Download and install the SMC fan control program and bump up the speed on the HD fan. In my case the HD was too hot. I haven't had the issue since.

I recently ran into the same problem with my iMac (27-inch, Mid 2010) 2.8 GHz Intel Core i5 ATI Radeon HD 5750 1024 MB computer w/ 16 GB of ram. The screen started flickering than blacking out all together shortly after updating from El Capitan to Sierra. I tried Resetting Vram, Pram, using a different keyboard, booting in safe mode, etc. Nothing worked. In the end resetting the computer back to El Capitan was the solution. No issues experienced since reverting! They do not offer hardware support for this iMac any longer, so I was glad to get back to having a monitor that functioned normally.

A couple of years ago I had the power supply replaced, but have had few other issues with it since. Hope to get a few more years out of this computer, as it is more than powerful enough for the work I do here at the office. Best of luck to those experiencing the same issue.

Same issue on a 2011 iMac 27, random black screen. Tried resetting Pram, holding shift D on startup, SMC fan control. Continued researching and came across this most basic, basic of advice – check the vents on top and bottom of computer body for dust built up enough to clog the airflow. Lo and behold, bottom vents were packed with a thick carpet of dust! Just vacuumed them 5x, as well as top vent. Can easily see how this would create a thermal problem. So far, so good... can't hurt, gotta help.

cleared the “hot corner” setting to nothing Fine now

I did have the same issue , and found it may also be caused by a low (but still sufficient to connect&work) wireless keyboard battery

so ive got a similar problem but the worst thing is that i locked my computer for 3 days and right before the 3 days was up, i went to the store for 20 minutes before i left everything was fine, it all worked perfectly but i came back, moved and clicked my mouse to turn on the screen, all the rgb lights went on, but the screen was black. i restarted my mac about 25 times and nothing, i reset the SMC NVRAM and PRAM all atleast 3 times and nothing worked, the model is a 2007 iMac High Sierra