Q: iMac 2011 27inch i7 screen flicker dark left side

Here are some photos inside the mysterious gray strip.

Unfortunately in my case SQUEEZING did not solve the problem.  It is annoying because if I squeeze or especially bang it, it will "flick" to being correct for a few moments.  But then it falls back to the dim state.  It's easy to assume that something is simply loose.  So I thought, can I get inside the **** LG LED unit??

Let's see!  Notice the piece of scotch tape, which is pointless - rip it off.

Here are the six enormous images:  http://postimage.org/gallery/toakbhq/

That site is very useful for posting large images. Click on an image, and click again for the enormous image where you can easily see individual pixels on the running mac screen, etc.

Here is the mysterious black strip. Rip it off.  Underneath is mysterious slots.

What is inside the mysterious slots?

Unfortunately I do not know and couldn't find out, but it must have something to do with the backlights. I shoved every sort of tool inside all of the slots, I used a hammer and chisel and so on. (You can see the marks in the hires photo.)  Unfortunately as I say I could only make it "flick" to the correct lighting -- I was unfortuantely not able to get a permanent fix by applying pressure.

Note that WITHOUT disconnecting the four cables that connect the LED unit, you CAN carefuly edge out the LED unit, and, sit it on top of the frame - you can get your hands under all four sides at the same time. So the mac will still be running normally with the screen hanging out.  A small point, don't forget to thread just the power cable on the back of the machine "not" through the elegant stand hole, so that it does not foul the stand when the machine is lying down. By the way in this photo you can clearly see the problem where half the screen is dim.

To be clear just unscrew the eight simple screws which stop the screen from tumbling out.  Then lift out one edge of the screen.  LOOK UNDERNEATH AT THE FOUR CABLES, to see how much play you have (you can only lift it a few inches.  Then pull it towards you an inch, and then the other edge of the screen will slip out. Then you can lift all four edges and sit it on the iMac case like this.

So I could not achieve anything other than a "blink" fix by squeezing or beating on the LED unit. Next I tried to remove the piece of metal that wraps around the screen. Notice you can see TWO screwholes on the relevant piece of metal here (one pointing left one right), there are two more at the top.  I unscrewed them, but unfortunately, the piece of metal does not come off in any way I could get it to come off.  (I don't know if it's due to adhesive or what - I used chisels, heavy pliers, roofing tools etc and it would not budge.)

Continued ...

I think there's a limit of five images per post.

Finally in relation to what Nicholas said:

Very large images ... http://postimage.org/gallery/toakbhq/

in the photo I am squeezing my thumb DOWN towards the floral tablecloth and fingers UP towards my thumb with as much force possible, I also used big pliers, clamps etc.  And I tried all the way along.

I am pretty sure, this is just where Nicholas was able to apply pressure -- and in fact in his case totally fix the problem and save 1500 bucks.

I found that the "magic point" was EXACTLY where Nicholas describes it in his post above. I am sure this will help others in the future.

Unfortunately as I explain .. in my case whetever is loose would not go together: if I bang or squeeze it, it sometimes "flickers" back to perfect brightness, for a moment, but I can't get it to stay like that.

You have to assume it's nothing more than something being loose.  And again very sadly as I explain in the previous with images, I was not able to get further in to the LG LED unit.  Bad luck for me!

So unfortunately the machine is essentially a write-off. A great pity as it would have been good for at least another year, it's not even 2 years old.  I find it depressing using an external monitor and then "half" of the main monitor, you feel like you are homeless or somerhing    So, bad news for me but great info for others with the problem, thanks Nicholas.

Hope this helps someone.

Just adding my name to the list of people suffering problems.  I have a 2011 27 inch iMac (12.1) and am getting the intermittent flickering and random significant changes in the display's brightness.  Full brightness is now consistently the same as the level I used to have it on which was approximately brightness set at 50%.  I don't yet have problems with the left side of the screen, but it sounds as though these symptoms are a precurser.  I'll need to work out whether my Uni break comes before my warranty expires to take it in for repair, or if I'll have to be without it during semester. 

Model Name:          iMac

  Model Identifier:          iMac12,2

  Processor Name:          Intel Core i7

  Processor Speed:          3.4 GHz

  Number of Processors:          1

  Total Number of Cores:          4

  L2 Cache (per Core):          256 KB

  L3 Cache:          8 MB

  Memory: 32 GB

  Boot ROM Version:          IM121.0047.B1F

  SMC Version (system):          1.72f1

  1GB GDDR5 AMD radeo 6970M

Great im having the sim Dim Flicker issue, its suddle but aggrivating during low light work... Kept waiting for the

updates to fix the Issue I guess apple wants us to be a little louder about this...

I have the same iMac and same problem DamenS is having.  Apple Care said to take the iMac back to the Apple Store.  I took my iMac to the university book store, where I purchased it, and the Mac Tech kept it for several days.  He stated he never saw the flickering and brightness problem.  So, the iMac is back at home and the flickering brightness problem continues.  I am not able to make the problem happen, it is random.  I plan to contact Apple Care again - not sure this situation will be resolved - I doubt this is software related.

Hi CWard --

it's not software.  Very simply, it's the LED lights inside the L.G. display panel which is the display panel in your Mac.

You can actually simply slip the glass screen off, and then tap on the area (see the various photos above) and you'll see it flicker - if you're lucky it might even come good by squeezing it etc.

If they claimed they "couldn't see the problem" you just have to scream at them and abuse them.  Hope it helps!

Take it to an actual Apple Store if your still under warranty or under Apple Care.  They fixed mine free and never demanded to see the flicker. They just replaced the bad part and it's been fine since.  No hassle.  And definitely not software problem btw.

With AppleCare, insist on an onsite visit so you can demo the issue.

After a conversation with Apple Care, Apple is sending me a new computer.  The engineering group wants to "capture" the problem with my current iMac.  This is a good solution and I do appreciate the concern about the problem voiced by the Apple Care rep.

If that's the case, get an ext FWHD. put a bootable backup/clone onto it, and  ensure that it works like the original. Then, erase the HD and reinstall Lion and set it up with a generic user and password. Pass that info along to Apple. When the new machine arrives, follow the steps in Pondini's Setup New Mac guide, using the bootable backup/clone as the source. Once that's finished, the new machine should act exactly like your current one; hopefully, w/o the flicker issue.

Done, thanks for the advice.  I hope the new computer is without the flicker issue too.

It should be. I suspect it'll be especially checked before the send it out. Post back when you get everything back up and running.

Baltwo,

I sent my old computer in on Monday, had the new computer on Friday.  I set up the new computer via Time Machine and it is exactly as the old computer was set up.  Looking at the new computer, I realize that in addition to a screen flicker, my old computer's screen was darker than the new computer.

Apple treated me right by replacing the computer!

I am having the same problem with my iMac 27"

Third of the left side of the screen dims after I turn it on. I believe it's an LD thing similar to what happens to laptops, but as you all have pointed out. Probably a connection issue in this case. Have an appointment to go to the Applestore on Friday. I have a time Machine backup and on the latest version of Lion 10.7.3. Anybody recommend a bootable backup over a time machine version?

Mark

Model Name:          iMac

  Model Identifier:          iMac11,3

  Processor Name:          Intel Core i3

  Processor Speed:          3.2 GHz

  Number of Processors:          1

  Total Number of Cores:          2

  L2 Cache (per Core):          256 KB

  L3 Cache:          4 MB

  Memory:          8 GB

  Processor Interconnect Speed:          5.86 GT/s

  Boot ROM Version:          IM112.0057.B01

  SMC Version (system):          1.59f2

  Serial Number (system):          QP0470KDDNP

  Hardware UUID:          30CE64A3-7D86-5E4C-A537-E47FB124D536