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Old Feb 21, 2012, 09:38 AM   #1
Kavik
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2011 iMac Brightness Flicker

About a week ago I started noticing the screen brightness randomly changing on my mid-2011 27" i7 iMac. The screen is darkening the equivalent of one to two brightness settings from full brightness, which is typically where I have it set during the day. Sometimes it only flickers for a second or two, but often stays at the darker setting for several minutes.

I do not have the ambient brightness change setting checked in the Display control panel. I'm running Snow Leopard 10.6.8 and have already performed a PRAM and SMC reset.

I'd like to find out if this could potentially be a system/firmware issue, or if this points to a physical problem with the backlight, its power supply or the video card. I know that LED screens adjust their brightness with a modulator, but not sure if this would be located in the power supply or the screen itself. The iMac is still under warranty, but I'm loathe to have to haul it in to the Apple Store, particularly since this is an intermittent problem.

Has anyone else had this issue?
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Old Feb 23, 2012, 01:43 PM   #2
Kavik
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After spending some more time with my iMac, I realized yesterday that the brightness changes are occurring only on the left side of the screen. After searching for "half screen dark," I found these threads:

https://discussions.apple.com/thread...art=0&tstart=0

https://discussions.apple.com/thread...art=0&tstart=0

It appears that the LG panel used in the 27" iMac utilizes two LED backlight bars, located on the left and right sides at the bottom. For whatever reason, the left light bar seems to be more prone to failure and is apparently going bad on my iMac.

I have contacted Apple for service, though hopefully they will be able to fix or replace the backlight without replacing the entire display panel module. My current screen up until now has been perfect with no color temperature differences (yellowing) or other issues, and it would be extremely disappointing to get an inferior replacement.

By the way, the photo below (from the thread above) shows what I am experiencing.


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Old Feb 26, 2012, 11:54 AM   #3
luke23
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I have the same problem. My iMac is first generation of 27" display and is out of warranty. Can I claim a free of charge repair?
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Old Feb 26, 2012, 01:36 PM   #4
John T
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Quote:
Originally Posted by luke23 View Post
I have the same problem. My iMac is first generation of 27" display and is out of warranty. Can I claim a free of charge repair?
If it's out of Warranty - it's out of Warranty!
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Old Feb 26, 2012, 06:23 PM   #5
iMacC2D
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Originally Posted by Kavik View Post
I have contacted Apple for service, though hopefully they will be able to fix or replace the backlight without replacing the entire display panel module.
The Backlight is only provided with a complete change of the display assembly, so I wouldn't expect this to be possible.

Quote:
Originally Posted by luke23 View Post
I have the same problem. My iMac is first generation of 27" display and is out of warranty. Can I claim a free of charge repair?
Nope. It will be eligible for Out Of Warranty paid service, but that's it.
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Old Mar 15, 2012, 04:32 PM   #6
Worldbuyer
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Angry flickering back light

I had this problem on my 2011 27" for a months, always thinking it was me hitting the mouse incorrectly. Then the left side went out completely, once I reliezed it was something wrong with the monitor I took it in the "genius bar". They proceeded to tell me it was not a month out of warranty so I would have to pay to have it fixed. They did admit they have the same problem with the 2012 models and are fixing those for free, but since they haven't fessed up to knowing the have a problem with 2011's I'd have to pay the $530- to have it fixed. Basically they suck, if you have any issue and are still under warranty take it in, it will go back and they will not give you any leeway.
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Old Jan 15, 2013, 01:30 PM   #7
MikeKubo
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LED Backlight Flickering

I am also having the same problem with my mid 2011 iMac 27" i7. LED backlight is flickering on the left side only. Unfortunately, I didn't get AppleCare for this machine. Does anyone have any useful words that will convince the "Genius" Bar folks that this problem should be covered?
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Old Jan 16, 2013, 12:32 PM   #8
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Genius my a%@#$@

Quote:
Originally Posted by MikeKubo View Post
I am also having the same problem with my mid 2011 iMac 27" i7. LED backlight is flickering on the left side only. Unfortunately, I didn't get AppleCare for this machine. Does anyone have any useful words that will convince the "Genius" Bar folks that this problem should be covered?
Sadly the genius bar should be in quotes, my 16yr old son knows more than the folks I've interacted with at the Carlsbad store. Apple knows they have a problem and only offered to correct the 2012's, obviously the 2011 have the same problem and they offered to fix it for $500. So I bought a second monitor for $200 and pluged it in as an accessory. Apple sucks on backing up their products, I have since bought 2 computers, both Windows based and from Costco as they stand by their products. I keep my iphone and ipad, but never buy a computer from mac again.
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Old Feb 26, 2013, 01:03 AM   #9
walrusaur
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My gf's iMac just started exhibiting this same behaviour in the exact same way as the picture in this thread shows. Left side kind of dark/dim, more towards the bottom left corner. Before the display went dark in that area, I had noticed sometimes that it would flicker slightly and change brightness periodically.

Is this for certain caused by a bad led light bar in the display itself, or is it something that can be fixed by just replacing the led driver board?

I did find another thread on here from two years ago that said he replaced the led driver board and it did not change anything though....so I would guess that my question is already answered in that the whole display needs to be replaced. I was just hoping to get second opinions on it, since the system is also out of warranty...
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Old Mar 27, 2013, 11:03 PM   #10
ijohn.8.80
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This just started happening on my Mid '11 27" iMac.

According to this page, the problem is a simple matter of soldering wires into a plug.

I'm off to the Apple approved repairer who I have spoken to about the possibility of them checking out whether the cable is the problem and not wasting $1000 on a new display.
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Old May 5, 2013, 03:22 AM   #11
Wavell
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Originally Posted by ijohn.8.80 View Post
This just started happening on my Mid '11 27" iMac.

According to this page, the problem is a simple matter of soldering wires into a plug.

I'm off to the Apple approved repairer who I have spoken to about the possibility of them checking out whether the cable is the problem and not wasting $1000 on a new display.
This happened to me also.. iMac is about 17 months old and has been an issue for maybe the last 3-4 months. I took it to my local Apple store and they replaced the backlight board, to no avail. I've been booting it up into my windows 7 partition since, as I suspect there's more to this than just a hardware issue. and guess what -the display is rock solid. Go figure
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Old May 5, 2013, 03:55 AM   #12
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Originally Posted by Wavell View Post
This happened to me also.. iMac is about 17 months old and has been an issue for maybe the last 3-4 months. I took it to my local Apple store and they replaced the backlight board, to no avail. I've been booting it up into my windows 7 partition since, as I suspect there's more to this than just a hardware issue. and guess what -the display is rock solid. Go figure
Mine ended up having the display and logic board replaced. Works like a treat now. Sorry you're still having issues with yours, I have no suggestions for you I'm afraid.
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Old May 27, 2013, 10:48 AM   #13
curtisinoc
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Originally Posted by Wavell View Post
This happened to me also.. iMac is about 17 months old and has been an issue for maybe the last 3-4 months. I took it to my local Apple store and they replaced the backlight board, to no avail. I've been booting it up into my windows 7 partition since, as I suspect there's more to this than just a hardware issue. and guess what -the display is rock solid. Go figure
I've noticed this issue recently and will take it to my local Apple store also. How long did it take to replace the backlight board? Did you have to leave it for hours, days, weeks?

thanks
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Old May 28, 2013, 03:49 PM   #14
Wavell
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I've noticed this issue recently and will take it to my local Apple store also. How long did it take to replace the backlight board? Did you have to leave it for hours, days, weeks?

thanks
They literally replaced the entire display there and then after I took it back for the second time, although typically you're talking maybe 2-3 days.. Backlight board replacement wasn't enough. At least they deducted the cost of the first attempted fix from the cost of replacing the entire display. Overall though, it still came to about 450 !
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Old May 28, 2013, 05:46 PM   #15
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Originally Posted by Wavell View Post
They literally replaced the entire display there and then after I took it back for the second time, although typically you're talking maybe 2-3 days.. Backlight board replacement wasn't enough. At least they deducted the cost of the first attempted fix from the cost of replacing the entire display. Overall though, it still came to about 450 !
Okay. Thanks!
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Old Sep 18, 2013, 05:28 AM   #16
Chesron
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Repair, don't replace! (and save hundreds!!)

I have found a company in the UK who repair rather than replace the LCD at a fraction of the price charged for a new screen.

They are called The iT Store and are based in Canterbury. Have a look on FaceBook /theitstoreuk for more details. They have a listing on eBay for it as well.

I've taken two into their office and both were repaired perfectly within a week. They charge around 200 for this with their own warranty but my customers have working iMac's and they think I'm great. The iT Store are VAT registered as well so my customers were able to account for that.
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Old Apr 10, 2014, 05:27 PM   #17
Rowbear
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FYI, I just brought in my mid 2011 iMac and Apple will replace the LCD panel and the backlight board. No charge as I had purchased Apple Care. Otherwise, it would have been $564. (Canada)

Genius Bar Work Authorization

Repair No: R11********
Customer Information
Product Information
Robert Gravel Warranty Status: Protection Plan(A)
CAN Model: IMAC (27-INCH, MID 2011)
Date of Purchase: 29-Dec-11
Serial No: C02G******
Problem Description/Diagnosis
Issue: The back light is not uniform the left side has gone out after computer warms up.
Proposed Resolution: Please replace LCD panel and the backlight board
Cosmetic Condition: No signs of damage at all
Estimated Turn Around Time: We'll call you in 3 - 5 days
Mac OS Version: 10.9.2
Hard Drive Size: 1000 GB
Memory Size: 16 GB
iLife Version: n/a

Employee 195******

Repair Estimate
Item Number Description Price Amount Due Customer KBB
661-6615 LCD PANEL 27 INCH WITH BLC $ 525.00 $ 0.00
S1490LL/A Hardware Repair Labor $ 39.00 $ 0.00
Tax $ 0.00
Total $ 564.00 $ 0.00
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