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Lester GrimeNose Level 1 (0 points)

I'm using a new 27" iMac. I require a dual-monitor configuration so yesterday I purchased a new 27" Thunderbolt display and plugged its built-in Thunderbolt cable into the Thunderbolt port of the iMac. I now have a huge desktop space that spans two monitors. With that in mind…


At least once every few minutes the new Thunderbolt display blacks out (i.e. flickers) for approximately one second. The symptom is very similar to what a Windows-attached display does when the screen resolution is changed. A quick Google search indicates others are experiencing the same problem although most complainants are using a MacBook or Mini, not an iMac.


Apple posted a firmware update for the Thunderbolt display a few days ago. I installed it successfully but the problem remains. Any advice?

iMac, Mac OS X (10.7)
  • BarrettF77 Level 1 (45 points)

    I have two of them hooked up to my 27" iMac i7 with a 3 screen setup currently.  I applied the firmware patch to the displays last night upon hook up and haven't had what you are describing.  I did have one time today where when I powered the computer out of sleep that only one of the two displays turned on the backlight.  I put it to sleep and then woke it up again and tried a restart and they haven't done this since. 


    I did have the flickering issue with the 24" ACD that I had attached and finally got replacements yesterday after months and months of back and forth with every channle within apple.  See about going and applying the firmware update again.  Perhaps it didn't take correctly.  I'm also sure that apple will have more updates rolling out for thunderbolt as we progress forward as it seems the pubilc has become Apple's/Intel's beta testers on this new technology. 

  • Lester GrimeNose Level 1 (0 points)

    I tried reinstalling the firmware update for the Thunderbolt display but it didn't help. The update process automatically halts when it recognizes that the firmware is already up to date.


    I also tried updating the firmware for the iMac's Thunderbolt port as described here:


    ...but this didn't solve the problem either.


    So what now? It doesn't make sense for me to do an exchange for a new monitor; Apple forums indicate that the problem is widespread which leads me to believe there's a fundamental problem with all of the 27" Thunderbolt displays. I can return the monitor to the Apple store for a full refund within the next fourteen days. That's likely what I'm going to do.

  • Lester GrimeNose Level 1 (0 points)



    On 9/25/11, I called AppleCare and asked for advice. The only salient take-away points were:


    (1) Apple is aware of the flicker problem with the 27" Thunderbolt display. It's affecting numerous customers.


    (2) The flaw manifests on some, but not all displays.


    AppleCare's recommendation was to return my monitor and exchange it for a new one. I did exactly that. I then reinstalled the latest firmware on the new monitor.


    The flickering problem resumed within minutes. My suspicion is that this is a fundamental design flaw that affects virtually all 27" Thunderbolt displays. Needless to say, I'll be returning mine to the Apple store and getting a refund. 


    I'd strongly advise avoiding this display until Apple has worked out all of the kinks. It's beta quality and simply isn't ready for production use yet.

  • BarrettF77 Level 1 (45 points)

    Personally, I would hold off until a day or two until your return period expires if you like the display.  I know 10.7.2 is just about to release and I am assuming that it may fix it.  I do know it contains graphic updates and a firmware update might go along with it.  Since the display has only been available for a week or two I am sure that something will be done.  I personally haven't seen it. 


    I did come from two 24" cinema displays that were awful on thunderbolt.  7 months of Apple stating that they were working on a fix and nothing ever came of it.  So I don't think this will be a repeat.  It would really reflect poorly on apple's cinema display line. 

  • Lester GrimeNose Level 1 (0 points)

    Thanks, Barrett. I will do as you've advised. I didn't realize that 10.7.2 was right around the corner. If it's released within fourteen days [which is my return time window], I'll install it and let you know if it resolves the issue.

  • BarrettF77 Level 1 (45 points)

    Not a problem.  The latest beta for 10.7.2 shows no known issues and thunderbolt and graphical components are one of many areas it is targeting as well as the integration of iCloud.  And if you are close, just have your apple store put it in writing that they will take it back after the 14 day period in the hopes that resolves your problem.  Glad I could help.

  • Lester GrimeNose Level 1 (0 points)



    I received a call back from a senior tech at Apple. The salient points are as follows:


    (1) Apple engineers are well aware of the problem.

    (2) They plan to release a firmware update for the display at some indeterminate time.

    (3) The fix for this problem will not be bundled into the forthcoming 10.7.2 Lion update.


    Given that the flickering problem renders the Thunderbolt monitor virtually unusable as a desktop extension for a 27" iMac, combined with the fact that Apple has no idea when a fix for the problem will be available, my decision to return the monitor for a full refund is a virtual certainty.


    AppleCare objected to my conclusion that the Thunderbolt monitor is "incompatible" with the iMac. Perhaps they're right. I'm not super technical so it's possible that I used the wrong term. It's a semantic distinction though. The bottom line is that Thunderbolt displays flicker when attached to a brand new 27" iMac and my personal opinion is that one is better off not purchasing this device until Apple fixes this major flaw.


    Apple asked me to make a video of the Thunderbolt display manifesting the problem. Here it is.



    Hopefully this information will be of value to someone.

  • BarrettF77 Level 1 (45 points)

    Based off of that answer I would do the same.  It's really sad to see that Apple has had thier phone support sink to this level.  In my dealing with them over the 24" cinema display and the flickering they promised me a fix "shortly". 7 months later I still had the problem and no firmware rollout was ever implimented.  Too much on their plate or perhaps they hired some staff from microsoft?  Who knows.  Sadly, their secretive nature is beginning to work against them as they are no longer a small company with a mentality of such.  Instead, they want us to prove the problem exists, make us wait, and then prove the problem exists again. 


    I think you are making the right call to prove to them that money talks and you are taking yours back.  Customers are not BETA TESTERS. 

  • My voice is my password Level 2 (270 points)

    looks like it's official now.


    the article and firmware can be found here.  its also has a description of what systems and configurations are affected




  • matthew.heinrich Level 1 (0 points)

    I can confirm this issue with a brand new 27in iMac (3.4, 6970M 2Gb) and Thunderbolt display. I does not happen every few minutes but it does happen a few times throughout the day.


    I have 10.7.1 and all the updates that are available but still have the issue.


    Hopefully Apple resolves this soon... hard to accept such an expensive setup not working correctly.

  • Lester GrimeNose Level 1 (0 points)

    Hi MVIMP,


    Looks like this firmware update only applies to the older Cinema displays, not the newer Thunderbolt displays. Unfortunate.



  • Natejj Level 1 (0 points)

    I've got the same setup...27" iMac and 27" Cinemea display.  I just hooked up the secondary display today and every 5 minutes or so the screen blanks out for a second.  I just ran updates and there was a firmware update available for it.  Unfortunately, it's still doing it after installing the update.

  • Natejj Level 1 (0 points)

    Well, I called Apple and they sent me a new display since it was less that 30 days old.  I hooked up the display....same flicker.  I even decided to format my hard drive and reinstall the OS.  Even with no software installed other than what comes preloaded in 10.7.2, I still have the same flicker. 

  • Xolev Level 1 (0 points)

    My 27" display worked for over a year on a older Mac Mini Core2 using the Tunderbolt connection, It only started with the screen flicker after I upgraded to a new Mac Mini i7. I am beginning to believe it's within the computer systems themselves when on for 30+ Minutes after they heat up, and has nothing to do with the display?  On the lastest patches 10.7.2

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