2011 iMac Brightness Flicker

Discussion in 'iMac' started by Kavik, Feb 21, 2012.

  1. Kavik macrumors member

    Oct 12, 2007
    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?
  2. Kavik thread starter macrumors member

    Oct 12, 2007
    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:



    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.

  3. luke23 macrumors member

    Jan 2, 2006
    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?
  4. John T macrumors 68020

    John T

    Mar 18, 2006
    If it's out of Warranty - it's out of Warranty! :)
  5. iMacC2D, Feb 26, 2012
    Last edited: Aug 12, 2017
  6. Worldbuyer macrumors newbie

    Mar 15, 2012
    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.:mad:
  7. MikeKubo macrumors newbie

    Jan 15, 2013
    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?
  8. Worldbuyer macrumors newbie

    Mar 15, 2012
    Genius my a%@#$@

    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.:mad:
  9. walrusaur macrumors newbie

    Feb 25, 2013
    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...
  10. ijohn.8.80 macrumors 65816


    Jul 7, 2012
    Adelaide, Oztwaylya.
    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.
  11. Wavell macrumors regular


    Nov 7, 2007
    Essex, UK
    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 :(
  12. ijohn.8.80 macrumors 65816


    Jul 7, 2012
    Adelaide, Oztwaylya.
    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.
  13. curtisinoc macrumors 6502

    Mar 13, 2011
    Southern California
    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?

  14. Wavell macrumors regular


    Nov 7, 2007
    Essex, UK
    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 ! :(
  15. curtisinoc macrumors 6502

    Mar 13, 2011
    Southern California
    Okay. Thanks!
  16. Chesron macrumors newbie

    Sep 14, 2012
    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.
  17. Rowbear macrumors 6502a


    Apr 14, 2010
    Gatineau, PQ, Canada
    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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