Lester GrimeNose

Q: New 27" Thunderbolt Display Flickers when attached to new 27" iMac

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)

Posted on Sep 24, 2011 4:40 PM

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Q: New 27" Thunderbolt Display Flickers when attached to new 27" iMac

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  • by ruslantagirov,

    ruslantagirov ruslantagirov Aug 27, 2014 10:49 AM in response to willber11
    Level 1 (0 points)
    Aug 27, 2014 10:49 AM in response to willber11

    Have you tried the NVRAM reset procedure?

    Try resetting NVRAM as described in this article: About NVRAM and PRAM

    Resetting NVRAM / PRAM

    1. Shut down your Mac.
    2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
    3. Turn on the computer.
    4. Press and hold the Command-Option-P-R keys before the gray screen appears.
    5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
    6. Release the keys.

     

    As I stated above, I totally got rid of the 'flickering' issue  with my home Thunderbolt display after updating to Mavericks 10.9.2.

    Now i'm on 10.9.4 and all works fine.

     

    But recently I brought the laptop to my office and connected the other LCD monitor via Apple Displayport-DVI adaptor (which is fine with Thunderbolt port on my MBPro 8,1).

    And the display eventually started flickering, it was like my laptop tried to constantly change the LCD's resolution.

     

    I've proceed the NVRAM reset procedure and the problem disappeared.

    I've been working on this laptop with this LCD the whole previous week — no flickering or other display related problems.

     

    Now I'm at my home setup again, and still no problem.

     

    Please, let us know if the NVRAM reset helps you.

  • by willber11,

    willber11 willber11 Aug 28, 2014 9:52 AM in response to Lester GrimeNose
    Level 1 (0 points)
    Aug 28, 2014 9:52 AM in response to Lester GrimeNose

    I did all of the NV Ram resetting and everything else that apple said to do but nothing changed, and that is why I am here.

  • by Tim Hassett,

    Tim Hassett Tim Hassett Aug 28, 2014 12:52 PM in response to willber11
    Level 1 (15 points)
    Aug 28, 2014 12:52 PM in response to willber11

    Hey Wilber, I had many of the exact same issues as you.  Have you tried a short Apple Thunderbolt Cable from your Mac to the back of the display?  (thus bypassing using the TB cable that's hardwired into the back of the display.)

  • by Francisco Jose Villegas Belo,

    Francisco Jose Villegas Belo Francisco Jose Villegas Belo Aug 29, 2014 3:40 AM in response to BarrettF77
    Level 1 (0 points)
    Aug 29, 2014 3:40 AM in response to BarrettF77

    Definitively it´s the Thunderbolt cable...... since Mavericks 10.9.2 i have the problem, the TD Display flicker, goes black... etc..... one day works well.... one bad... i connect the TD with my rMBP with the Apple 0.5 meter Thunderbolt cable, and voila, all go well. No flicker, 10/10.

     

    I think that soft have part of this problem, why with pre-Mavericks 10.9.2 all works, and before that i have the flicker problem??.

     

    Well, i don´t know, the question is that with a "external" cable bypass the display thunderbolt cable all works.

  • by dukephoto,

    dukephoto dukephoto Sep 27, 2014 9:48 AM in response to ruslantagirov
    Level 1 (0 points)
    Sep 27, 2014 9:48 AM in response to ruslantagirov

    Tried the NVRAM, did nothing at all. My TD in plugged in to a 13" MBP Retna. Worked perfectly until the Mavericks 10.9.2. Not sure how this could be a hardware issue if all was working before the update.


    This bypass TB cable thing does not make sense. isn't the TB port to the right on the back an input? how can it work as an output bypass?


    Why does it take so long to send out a bug fix? I've got work to do and don't have time for this. APPLE! Lets move it...

  • by Tim Hassett,

    Tim Hassett Tim Hassett Sep 27, 2014 11:01 AM in response to dukephoto
    Level 1 (15 points)
    Sep 27, 2014 11:01 AM in response to dukephoto

    dukephoto, on the back of the TB display, you'll see 1 TB port - it functions as both an input and output.....for daisy chaining of devices.  But it also works as a video input, so try the short .5M Apple TB cable.....it worked for me. 

     

    I had the exact same issue as you.....nothing changed with my hardware, but I upgraded to Mavericks, and I started to get the flicker.  My theory on this is that Apple made the more recent versions of OS X more sensitive to the changes of the video signal in the longer TB cables, and now we're seeing the video drop in and out based on signal levels/frequencies getting too low.  Ultimately, it's a defect in the built-in TB cable in the display, and now OS X is more sensitive to it, and cuts out the video when certain tolerances are reached. 

  • by dukephoto,

    dukephoto dukephoto Sep 27, 2014 11:34 AM in response to Tim Hassett
    Level 1 (0 points)
    Sep 27, 2014 11:34 AM in response to Tim Hassett

    OK, So, I don't have a .5 meter but I did have a 2.0 meter. I figured what the heck. Tried it and it's working. So, the cable length is not the issue. Bummer I now can't use my TB drive but the TD is now working. I wonder if we can daisy-chain a TB drive and display in the sam manner?

     

    Thank you Sir,

    DG.

  • by rcx1,

    rcx1 rcx1 Oct 4, 2014 12:41 PM in response to dukephoto
    Level 1 (0 points)
    Oct 4, 2014 12:41 PM in response to dukephoto

    Did the new cable totally solve your problem?

  • by dtelena,

    dtelena dtelena Feb 10, 2015 1:55 PM in response to Lester GrimeNose
    Level 1 (4 points)
    Feb 10, 2015 1:55 PM in response to Lester GrimeNose

    I have exactly the same problem with my Apple Thunderbolt Display (27 inches), the problem started appearing right after I did apply the firmware update V1.2 to the monitor which was made available by Apple last November (my monitor was working flawlessly before applying this firmware update so I am pretty sure there is something wrong with this firmware version and this is the cause of the problem). Does anyone here did apply this firmware as well?

  • by ibrowne2011,

    ibrowne2011 ibrowne2011 Feb 23, 2015 5:41 AM in response to dtelena
    Level 1 (0 points)
    Feb 23, 2015 5:41 AM in response to dtelena

    Having the same issue after getting new(er) MBP.  On my old MBP I had the issue where the TD would simply go black and act like it wasn't connected.  The Firmware update (2.1) seemed to fix that.  Then I got a slightly newer MBP (with more ram and storage) and the TD seems to flicker every so often.  This seems slightly different than the previous issue though.  I made sure that everything was up-to-date as far as firmware goes, and that the connections were solid.  I'd love to know what's going on here since the flicker seems very random.  I only have one apple keyboard and ethernet running through the TD, nothing else.  Any ideas?

  • by Downfield,

    Downfield Downfield Aug 5, 2015 12:59 PM in response to Tim Hassett
    Level 1 (55 points)
    Aug 5, 2015 12:59 PM in response to Tim Hassett

    Tim

    Thanks for posting your solution of using a separate cable.

    I just wanted to confirm that this also worked for me.  Unfortunately I only saw the thread after taking my 4 year old TB screen in to Apple in Cambridge UK, and for them to diagnose the problem as a faulty backlight board.  They said this was attached to the display, so I would need a new display costing £640.  They only offered a 90 day warranty.

     

    So I declined, and bought a new screen (at a £100 discount) to get a longer warranty.  Having reclaimed the old screen I saw your post and purchased a new TB cable to try.  It has been working faultlessly since, now for a period of 8 weeks.  I use the captive lead as a power supply, and use the new TB lead between my MBA (2012 vintage) and the screen.

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