JamesZhangToTheMax

Q: iMac 27 inch Late 2009 Random Black Screen Issue

Hi. This issue is very common with this model apparently. So here goes. I bought an iMac and installed Windows on it. After a few weeks the screen randomly switches off (this is later discovered as the backlight turning off as the screen's image (ie, Windows start menu, background, etc) are visible when a torch is shone on it in a dark room). At first, simply restarting fixed the issue. But soon, upon restart, the screen would turn on for a second and then turn off. So I cannot even get past the apple logo with a turned on screen. However for some reason, after waiting for a few hours and turning it on, the screen worked again. But after a while, this technique didn't work and the screen turned on for a second and turned off.

 

This was bugging me so I took my iMac apart using iFixit's guide.

 

I disconnected all cables and all cables that connected to the inverter otherwise known as the LED Backlight Board and reconnected them.

 

I reassembled the iMac back. Still it didn't work. It got further though. It didn't turn off in the first few seconds of bootup, but just after logging in to Windows.

 

So I took it apart again and this time firmly reconnected the power cable from inverted board to LCD display. I reassembled and rebooted. It worked.

 

However after a week, the screen turned black again. I think this happened because I made the screen brighter on Windows for a while.

 

So I did the same thing, firmly reset the powercable. But this time it didn't work. I did it several times.

 

So giving up I just left it for a while. However after a day or two, I started it again. It worked.

 

Now this issue is really confusing me and a lot of other people. What is the problem?

 

Recently I read a post by Motorcycle Michael who showed that when he reset the LED Connector cables on the LCD Display, the black screen problem was fixed. So I did exactly that. I cut the retainers and disconnected and reconnected the LED Cables. It didn't work. I even tried placing wedges to hold the connection in place. Still didn't work.

 

So I am wondering if one of the LED cable was loose and it caused the whole LED backlight to turn off. So I intentionally disconnected one of the LED cables and reassembled. It worked! It worked without a problem. Up to now, it is still working. But why? Why is it when I disconnected one of the LED Connectors, that the backlight works, but does not with two?

 

Right now I am trying to decide if the problem lies in the LCD Panel, Inverter, Power Supply or Logic Board.

 

Does anyone here have any idea or fix? I know this post is way too long, but it is a serious problem among many users.

iMac, Windows 7

Posted on Jun 15, 2014 7:22 AM

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Q: iMac 27 inch Late 2009 Random Black Screen Issue

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  • by callzhang,

    callzhang callzhang Aug 10, 2014 1:30 PM in response to JamesZhangToTheMax
    Level 1 (0 points)
    Aug 10, 2014 1:30 PM in response to JamesZhangToTheMax

    Hi James,

     

    Thanks for your post. I am having the same problem and I haven't tried the LED cable or connector yet. Would you tell me how you did to the LED connector? A picture is worth a thousand word. It'll be great if you can show the process with pictures.

     

    Best,

     

    Lei

  • by DenLiam,

    DenLiam DenLiam Aug 12, 2014 7:25 PM in response to JamesZhangToTheMax
    Level 1 (0 points)
    Aug 12, 2014 7:25 PM in response to JamesZhangToTheMax

    I found the Energy Saver in settings set to 12 mins and the screen would go blank after that time. It can be changed to "never" or in increments of 3 mins.

    Best to check before pulling the computer apart.

  • by Liiaa ,

    Liiaa Liiaa Sep 18, 2014 6:14 PM in response to JamesZhangToTheMax
    Level 1 (0 points)
    Sep 18, 2014 6:14 PM in response to JamesZhangToTheMax

    i'm scared to mess with it... it's technically my dads but i've had this problem for maybe a year or two i don't even know it feels like forever.

  • by MarkusWinter,

    MarkusWinter MarkusWinter Oct 19, 2014 5:21 AM in response to Liiaa
    Level 1 (4 points)
    Oct 19, 2014 5:21 AM in response to Liiaa

    I installed Yosemite on my 2009 27in iMac on Friday morning and it hasn't blacked out since (Sunday noon now). Let's hope it continues that way. Anyone else with similar experiences?

  • by MarkusWinter,

    MarkusWinter MarkusWinter Dec 9, 2014 1:46 AM in response to MarkusWinter
    Level 1 (4 points)
    Dec 9, 2014 1:46 AM in response to MarkusWinter

    Update:

     

    My 27in iMac late 2009 could go three days without going black or black out every few seconds. I worked around it by having a hotspot in the lower right to trigger the "screen off".

     

    It went black only once after upgrading to Yosemite in October but has not gone black at all since the upgrade to 10.10.1.on the 18th of November.

     

    I hope it stays that way. Very happy camper :-)

  • by Captain L,

    Captain L Captain L Jan 24, 2015 7:55 AM in response to MarkusWinter
    Level 1 (0 points)
    Jan 24, 2015 7:55 AM in response to MarkusWinter

    SOLVED!

     

    I had the blackscreen/blackout issue (not the backlight) after I added RAM. I had added 2 x 4Gb and kept the 2 x 2Gb in the original slots.  I now had 12 Gb.

    The blackout issue started shortly after this.

    After reading the post (below) I took out the 2 x 4 Gb and replaced them with 2 x 2 Gb from another Mac I had lying around. This gives me 8 Gb with 4 identical DIMMS in the slots. The Black screen did not occur again, no matter how I try to recreate it changing the brightness, screensavers and/or sleep mode.

    I think the RAM solution makes sense, so far working for me, problem looks solved. Try it and let us know! Thanks Sunfiresaturn!

     

     

    Sunfiresaturn including Apple logo changes for feature 126 Apple image including Apple logo changes for feature 126 Apple image ends here

    Jan 19, 2014 5:03 PM

    Re: 27' iMac (2011) Screen turns off

    in response to Ashadur

    [DocumentBodyStart:b21f0b0e-bbb6-4d8f-827a-58c825f45ac6]

    All of your symptoms were indentical to mine and I tried EVERYTHING to fix it.

     

    My realization?

     

    RAM

     

    I have 4 slots open in my 2010 - iMac

     

    2x2GB DDR3-10600

    2x4GB DDR3-10666

     

    For some reason, my iMac couldn't handle both together. At first I thought it was the 10666, but then tried both RAM types separately, and both work.

     

    I guess you shouldn't pair 10600 with 10666 - or at least different ram sizes.

     

    I am going for 4x4GB 10666 now.

     

    I hope this helps everyone because I was losing my mind for a short while.

     

    iMac is happy and on full brightness.

     

    Life is good.

  • by c_ceddy,

    c_ceddy c_ceddy May 14, 2015 6:53 AM in response to JamesZhangToTheMax
    Level 1 (9 points)
    iPad
    May 14, 2015 6:53 AM in response to JamesZhangToTheMax

    I have a similar problem that just began in May 2015. The screen goes black and I discovered  if I used the keyboard command  [command option eject] to put it to sleep and then held down the [command option] keys again, it wakes up.

    I also discovered it appears to be related to heat and fan speed. I have HDD Fan control app installed and turned up the fan speed and the problem has improved. If i lower the fan speed under 3200 rpm the screen turns black when the temperatures rises above 35°C.

    Can anyone tell me what needs to be repaired?

  • by c_ceddy,

    c_ceddy c_ceddy May 14, 2015 7:00 AM in response to Captain L
    Level 1 (9 points)
    iPad
    May 14, 2015 7:00 AM in response to Captain L

    My research and self diagnosing led me to believe increasing the RAM would solve the problem. It just makes sense to increase the RAM with all the software upgrades that have occurred. You have reconfirmed my suspicions. Thank you.

  • by rajpool,

    rajpool rajpool Jul 7, 2015 11:52 AM in response to MarkusWinter
    Level 1 (0 points)
    Jul 7, 2015 11:52 AM in response to MarkusWinter

    Hi MarkusWinter


    I am experiencing the same problem (along with a whole lot of people by the looks of things!). Just wondering if changing to Yosemite has still been working for you?

     

    Many thanks

  • by MarkusWinter,

    MarkusWinter MarkusWinter Jul 7, 2015 12:13 PM in response to rajpool
    Level 1 (4 points)
    Jul 7, 2015 12:13 PM in response to rajpool

    Yes, still behaving itself. I had ONE black screen since upgrading last November.

     

    If you upgrade then let me/us know how it goes for you.

     

    P.S. My memory configuration is

     

    2x 4 GB 1333 MHz RAM (cheaper than 4 GB 1066 MHz RAM)

    2x 2 GB 1066 MHz RAM

     

    All running at 1066 MHz

  • by Anonmusic,

    Anonmusic Anonmusic Sep 9, 2016 12:14 AM in response to JamesZhangToTheMax
    Level 1 (4 points)
    Sep 9, 2016 12:14 AM in response to JamesZhangToTheMax

    I installed F.lux and all my backlight problems went away. Hope this helps someone.