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Old Jun 13, 2014, 06:14 PM   #26
Tropical John
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Screen goes black

So, if it is a failing video card, it is going to start to fail when it is hot.

That's why turning up the fan and turning down the screen help, doing so keeps your machine cooler.

Your typical Apple store is kept at meat locker temps with all those machines running. Meaning they might not be able to reproduce the problem. Take a video of it failing at home on your phone and take that with you. It's not like you're going to make this stuff up! but hard evidence might be necessary to get them to replace the video card.

PS you can hit alt+command+eject and then space and the screen will come back. Don't need to hard reboot.
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Old Jun 14, 2014, 06:20 AM   #27
ijlakw
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Thanks for the tip!
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Old Jun 26, 2014, 02:42 PM   #28
12Tarona
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27" iMac black screen fixed!!

I bought my 27" iMac in 2011..two years later the screen went black. Brought it back to Best Buy, they put in a new graphics card and some other stuff.. Returned home, shortly black screen returned. Put up with it for a while, returned to Best Buy, they put in a new back light, did some adjustments or what ever, returned home, shortly went black again. I installed a fan software, seemed to help, then went black again. I kept playing with it, shutting it of, turning it on over and over again. Sometimes it'd stay on for a while other times I just gave up and walked away. Finally I returned to Best Buy hot and red-faced. They took it in, called in about 10 days, it was ready.....Yea sure......I was skeptical. Brought it home and guess what?? It's been running almost non stop for 12 days and no black screen. What did they do? No parts! They just went in and unplugged all of the switches and wires and replugged everything again. Evidently one was loosely connected. Seems like they put these things together so fast that sometimes they get a little sloppy and things aren't plugged in tightly enough. It sure worked for me, and I'll bet this is the same problem for most of you guys. Good luck.
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Old Aug 27, 2014, 06:18 PM   #29
gatortpk
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Quote:
Originally Posted by 12Tarona View Post
I bought my 27" iMac in 2011..two years later the screen went black. Brought it back to Best Buy, they put in a new graphics card and some other stuff.. Returned home, shortly black screen returned. Put up with it for a while, returned to Best Buy, they put in a new back light, did some adjustments or what ever, returned home, shortly went black again. I installed a fan software, seemed to help, then went black again. I kept playing with it, shutting it of, turning it on over and over again. Sometimes it'd stay on for a while other times I just gave up and walked away. Finally I returned to Best Buy hot and red-faced. They took it in, called in about 10 days, it was ready.....Yea sure......I was skeptical. Brought it home and guess what?? It's been running almost non stop for 12 days and no black screen. What did they do? No parts! They just went in and unplugged all of the switches and wires and replugged everything again. Evidently one was loosely connected. Seems like they put these things together so fast that sometimes they get a little sloppy and things aren't plugged in tightly enough. It sure worked for me, and I'll bet this is the same problem for most of you guys. Good luck.
Thanks for this post!

My problem has been that after my screen goes to sleep, sometimes only the backlight will come back on and the screen will still stay black. Sometimes I will actually see my mouse arrow, so I know that the LCD display and it's backlight are actually working, but it just won't wake all the way up. The only solution is to hold the back power button for ~5 seconds to force a shutdown and then click it back on.

Why your post caught my attention is that I have also taken apart my entire 2009 27" iMac (32GB RAM, Core i7 2.8 GHz) including the logic board and put it back together. It actually seemed to work well for a week after I put it back together and I started getting the black screen after waking from sleep 3 times just today. I didn't take it apart because of this issue, I took it apart to replace the SATA cable (yes, that requires one to get to the back side of the logic board which means 34+ screws and ~19 connections have to be undone).

It's interesting that these connections can have unexpected consequences when they aren't perfect (within design specifications, they're never perfect and designed with that in mind). It's always either a lack of power, or a inconsistent data connection. I'm suspecting because parts of the computer wake up, the software itself didn't get the message to wake, and this could be caused by either problems associated with hardware connections.

I was wondering if a computer hardware expert can weigh in here? I repair computers, but I don't design them. I know no one person or team designs an entire computer system from the ground up like they did a few decades ago, but someone must have an idea what could be happening here. This issue seems common, but not prevalent enough for a recall. (I also understand that some posters on this thread are talking about a different issue. I'm referring to the 27 inch iMac display not waking completely from sleep, even though the backlight is on, the software isn't always aware that the display is back on.)
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27" iMac 2.8GHz Quad Core i7, 32GB RAM; Several 13"-15" MacBook Pros with Core 2 Duo, 3-16GB RAM; iPad 3rd Gen 64GB AT&T; Every iPhone 3GS to 6 Plus with max storage; 2 x Apple TV (3rd Generation)
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Old Aug 29, 2014, 10:43 AM   #30
ijlakw
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I'm still suspicious that I'm seeing a OSx bug. When my screen randomly goes black... while the computer is running find in the background.... if I briefly press the power button... the screen comes right back on. Very strange.. and basically unusable.
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Old Oct 4, 2014, 06:55 PM   #31
Uscambau
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This way worked alright for me

I had the same problem described here and the way I got it sorted was really fast and simple. I turned the i mac off, turn it back on again and before the gray screen showed I pressed command, option, shift and the keys P and R simultaneously.

Good luck!
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Old Jan 26, 2015, 10:12 AM   #32
jerrodtracy
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Mid 2011 27" Apple replacement program

http://support.apple.com/en-us/HT203787
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Old Feb 25, 2015, 01:26 PM   #33
T. Kier
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SMC Fan Control Worked!

I have an early 2008 24” Imac and been having the same issue with the screen going black randomly. The issue started about a month ago and has since happened more frequently. I had searched forums and tech sites looking for a cause. I had noticed that the aluminum computer housing seemed to be very hot and has been so the entire time I have had the computer. The computer has had the motherboard and graphics card replaced under warranty previously. Thus far the twech’s post from January 2014 has been most useful and the recommended fan control program by SMC; http://www.eidac.de/ . In a follow up I found this YouTube link (https://www.youtube.com/watch?v=FJkkiHHJ-oU) to be very helpful in explaining the problem and how to set the SMC fan control software. Prior to setting the fan speed, the CPU temp registered as high as 70°c. I have all of my fans set to 3000 rpm at this time and have not had a problem with six hours of run time. The CPU now rarely goes above 35°c. The fans are a bit noisy which may lead to my adjusting of the fan speeds but as of this post this has addressed my black screen issue. Hope this helps!

2008 24” Imac
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Old Feb 27, 2015, 11:21 AM   #34
Uscambau
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SMC fan control worked for a while, I tried many other fixes, but everything failed. Nobody seems to know for sure what the problem is. There's nothing to do with the temperature, cause the same thing happened even at 35º.
I gave up trying and bought myself a new monitor and a cable to connect my mac to it.
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Old Mar 10, 2015, 05:42 PM   #35
seabiscuit387
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temperature sensor?

I have a 2011 imac 27 that had the screen black problem. I cleaned the inside and re-positioned the flex print cable that is attached to back light shroud. I believe this is a temp. sensor. I re-taped this sensor? to the back of one of the foam offsets. Fans still operating. I haven't had a problem in three weeks. Has anyone else tried this? Any results?
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Old Mar 22, 2015, 02:13 PM   #36
U2LN
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Thumbs up

Quote:
Originally Posted by seabiscuit387 View Post
I have a 2011 imac 27 that had the screen black problem. I cleaned the inside and re-positioned the flex print cable that is attached to back light shroud. I believe this is a temp. sensor. I re-taped this sensor? to the back of one of the foam offsets. Fans still operating. I haven't had a problem in three weeks. Has anyone else tried this? Any results?
You're probably right about the sensor. My fans were running rather high before the problem started. No way my mom's letting me open it though.
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