Target display mode blinking black

You are onto something with the console message! Hopefully someone can decipher it.

I have heard of the Thunderbolt displays flickering too but it is much less common of an issue compared to the iMacs. My Applecare is expiring soon so I will take both of my machines down and show them the flicker. I will keep an eye out for the console message too and see if I get the same thing.

Thank you for the update !

On my side, I bring back the Thunderbolt cable and got a new one (juste in case). Issue is still there with the new cable.

Then, I discovered that my Mid 2011 27" iMac was (still) under AppleCare, so I chatted with the Apple Support today. They tried the following things:

reset the PRAM: unsuccessful. Asked to see if my Late 2013 27" iMac was also flickering when in TDM. Answer was no (well, not during the 10 min test at least), then Safe boot both iMacs. It took nearly 30 min to have the first blink, but it did happen. And it blinked again something around 2 min after the first blink.

So, since the AppleCare is about to expire, they urged me to bring the blinking iMac (the one which is Mid 2011) to the Apple Store, with mention of the case ID, of course.

The iMac is now there, I should have some news in one or two days.

We have the same machine. Mine is also a Mid 2011 27" iMac. I did test my 2013 MBP on my brother's late 2013 iMac and there was no flickering in an hour hooked up to it. I did also try resetting the PRAM, a new cable and I did clean installs of Mavericks on both machines.

It seems that the problem is quite common on our machine among others including some thunderbolt displays. Thanks for the update and good luck.

I am having the same issue here and hope that apple has a resolution. I have two iMac 27s connected together via thunderbolt. Apple please pay attention!

My 27" mid-2011 iMac is at Apple Center since July 24th for this issue, and I have yet to hear from them. I will definitely post a feedback when it comes back. I am wondering if anyone has got any official answer from Apple on this subject.

Quick update: I had a phone contact with the technician in charge: they hooked up my Mid 2011 27" iMac with a Mac Book Pro, put my iMac in TDM and had it filmed by another Mac for few hours. They claim they didn't reproduce the blinking. My concern is, on a after thougth: I think they obviously watched the video in fast forward... would they capture an half second black blink that way ? Pity I didn't ask.

However, since my issue is happening with an 27" iMac (late 2013) and not a MBP, he agreed to retest with an available 27" iMac at the lab.

If again successful, then I will bring my own late 2013 iMac to be tested with the mid 2011 iMac, because then the faulty iMac would be the Late 2013 iMac, and not the mid 2011 iMac used in TDM, even thought it's the one blinking and having the error message on its console reported on a previous post.

I thanks for the update. I have noticed that I continue to have the same issue and it's especially worse when I am running a virtual machine on the other screen but it still happens if I am not but with less frequency. The other issue is that the brightness adjustments on the screens (two 2013 iMacs) are not synced with the thunderbolt connection. This setup cost a lot of money and of apple spent a bit more time with the engineers perfecting this they would make a lot more money because I was willing to pay up for the second Mac because it wast that much more expensive vs the standalone Thunderbolt Display. Apple please invest in making this work properly. I do own every product they produce and I would have to say that this feature is the least perfected / seamless of all their products we own.

Also continuing to having the same problem. Seems worse since I've installed the 10.10 beta. It used to only blink out 2 or 3 times a day, now it's 5-6 times an hour. It is incredibly frustrating.

I've tried removing all usb devices thinking that maybe some hardware problem is triggering the display to stutter, but nothing I've done seems to make any difference.

Update from my side:

As agreed, my Mid 2011 27" iMac has been tested again as TDM with another 27" iMac. I received an update today. The technician claims everything perfectly OK. Next step is then to bring my Late 2013 27" iMac in the shop as well so they can test it with my mid 2011 iMac. Will do tomorrow. I hope it will blink in front of the technician !

Has someone been successful to get rid of the blink at some point ? I would love to hear from him/her !

This is totally a software issue apple please fix this!!

I would like to add that even more irritating than the screen going black for 1 second is audio dropping for 2-3 seconds.

The problem is getting so bad that I'm close to ordering a 2nd monitor and desk.

Im having the same problem but apple gives a ****.

I pass my complete warranty trying to solve the problem and nothing happens, i waste my time trying to contact people on the customer service, phone, stores and using the live chat but no one was able to give a dam answer.

Is apple reading all this notes ?

Is anyone with a solution diferent than throwing your imac to the face of the first apple representative ?.

Ive solve the problem !!!!

Upgrade to Yosemit on the imac late 2011 and works grate finally!!!!!

Ive tried Adobe Premiere, Davinci resolve.

I use the 2 m thunderbolt cable with a late 2012 macbook pro 15 inch.

UPGRADE YOUR OS AND YOU WILL HAVE TARGET DISPLAY ON YOUR IMAC!!!

I installed Yosemite on the target iMac, and it made it WAY worse.

Today after installing it, there has been a constant barrage of these little black screen episodes. Seems like probably at least a few times every minute.

I haven't installed Yosemite on my MBP yet, because i have apps that i don't think are ready for it, but I sure wish that i had NOT updated the iMac. This is TERRIBLE. Unusable.

Upgrade on both machines should work.

I have been working with no problems using Davinci resolve and pro apps.

I can even use the imac speakers as main audio output