iMac 27" Black Screen?

OK, the screen finally got to the point where it would only stay on for a couple of hours with the brightness at zero. I'm able to use UltraVNC to get into it from a PC even when it goes black, but I can't really go on using it like that. I now have a shiney new Philips 272P4QPJKEB/75 monitor connected as a primary mirror (mini Display Port to Display Port) and am getting the full 2560x1440@60Hz. I think I can go like this for some time now, waiting too see if there is a new Mac mini in October 2016. The late 2009 27 inch iMac is a lost cause.

In posession of an iMac 27" (mid 2011), facing the black screen challenge since aprox 2 years now. Did all of the suggestions except rewiring inside, replacing the screen or replacing keyboard. Since the black screen happens on both MacOS and Bootcamp/Windows, this indicates it is not a software problem. Reinstalled OS anyway 2x since which did not bring relief.

Will try new keyboard. Also... anyone tried plugging in an external monitor. Did this happen to anyone with an external monitor too? That would indicate whether the problem lies in Apple's display or potentially something on the graphic card.

Hi Steve, thanks. So this supports the hypothesis of me & Steve's issue lying in the areas of

1- the display

2- the dedicated part of the graphic card that sends the video output to the internal display

3- the cables between graphic card and internal display

Keyboard & power seems unlikely as they would tend to affect both your internal and external display.

At least - for the most frustrated users, an external monitor may bring relief to the black screen problem.

That said, as long-time user and lover of Apple products, I start questioning the company for not providing out-of-guarantee support on this kind of broad quality issue, while making $8.3million net profit per hour. Shame.

My last fix was not a permanent one (May 4, 2016 9:57 AM, Page 9). I know how to force screen flickering and thus make the monitor work for a couple of hours, but it is not a solution. At first it would work for a week, but in the end sometimes even less than a minute.

However, I have found something else. Since I couldn't afford a new iMac, I went for a Windows desktop (yes, I know, shush). I moved lots of my files to my new desktop and backup, and deleted them of my Mac. I went from 120 GB free space to 600 GB. And here it comes; since I have done that (2 months ago), the **** iMac has not gone black screen once...

The idea was to hook up my iMac to my new monitor, as it is performance wise a very good computer. But since it is up and running like it used to be, I had to extend my desk. I refuse to trow away (or sell) my good old iMac.

So my guess is that the black screen is being caused by several faults. De HDD is probably demanding more power when it is nearly full, the PSU can't handle that, so it turns of something that won't hurt hardware or software, so it turns to the backlight.

This may not help everyone (or anyone else at all), but it did for me. We're talking 2 months now, at full brightness. But it might be worth a try to delete some stuff of the internal HDD (Backup First ⚠)

I diagnosed this as a short in my keyboard - thanks to someone mentioning the keyboard as a possibility. My keyboard was sending out the key combination to toggle displays on a whim (alt+cmd+eject.) Whenever this would happen the main display would toggle off. Later on, on a whim once more, the keyboard would once again send alt+cmd+eject, the short would temporarily resolve and the main display would remain on for a period of time - until the next time... Replacing the keyboard absolutely fixed the problem.

I turned my keyboard off... Mac has been running fine now for 6 hours

Keeping my fingers crossed

I think we have a winner... How can a keyboard cause so much graphic problems ?

Actualy 12 hrs now

Computer just went to sleep... Almost had a heart attack...

Still going...

Do it, might speed things up... If apple store isint to far from you

still going strong here

Mine too.

well... still rolling... looking real good