Q: Intermittent Black Screens with 27" on Pro

I have the same problem with a very similar setup. I have not noticed any "click" noise. Monitor just blinks off momentarily. The problem only began when I upgraded to OSX Yosemite. My current thinking is that it is a Yosemite bug.

Mac Pro (Late 2013)

Processor: 3.5 GHz 6-Core Intel Xeon E5

Memory: 64 GB 1866 MHz DDR3 ECC

Graphics: AMD FirePro D500 3072 MB

Apple 27-inch thunderbolt x1

Same problem here. Started happening in the last couple days. Wasn't sure if this was faulty hardware but seeing others are experiencing the same issues makes me believe it's not.

I've got a 27" LED Cinema Display plugged into a recent Mac Mini through its Thunderbolt port. The intermittent black screen also happens when the is daisy chained to the computer with another thunderbolt device between the 2. That device works reliably so ruled out issues with the Thunderbolt port on the Mac Mini.

On my end, the black screen doesn't come back unless I unplug and replug the power cord of the display. However, while the image is black, everything else on the screen (camera, USB, speakers) works as it happened this morning during a FaceTime call and I could still hear the person through the display's speakers and they could still see me through the display's camera and hear me through a USB mic plugged in the display.

The latest update (10.10.1) did not fix this

Your issue sounds a bit different than the problem I was having, here's my latest.

For me the problem only occurs when I am using the Crome browser. It usually occurs just as I am scrolling up or down with the trackpad. It seems to be a problem with the Crome browser and Yosemite. The new firmware for the thunderbolt did not help. If I use the Safari browser the problem does not occur.

I have the same issue: while using a 27" thunderbolt monitor and a Mac Pro, the screen briefly turns off and on. I'll try to determine whether this is only happening in Chrome for me. Before I installed Chrome on this computer, I was using Safari, and I think I also noticed the flicker using Safari. I also noticed a soft click noise.

I have the exact same issue as the original poster.

2x AMD FirePro D500 and 2x 27" thunderbolt displays.

Mac Pro Xeon E5, 16GB ram.

Issue started occurring after Yosemite upgrade.

Anyone found a resolution to this issue?

identical, my problems started as well after the yosemite upgrade.

retina mbp.

This is also happening to me. It started a couple months ago. At first it would only happen when the Chrome browser was open. But now I rarely every use Chrome and it happens plenty when Chrome is not even open.

I have a 27" Thunderbolt Display and a Thunderbolt Mac Pro (cylinder).

The screen will blink out but all other peripherals plugged into the display's ports will still work.
I get these messages in the Console every time the display blinks out:

3/29/15 9:37:42.000 PM kernel[0]: IOThunderboltSwitch<0xffffff804e9b7c00>(0x0)::listenerCallback - Thunderbolt HPD packet for route = 0x0 port = 2 unplug = 1

3/29/15 9:37:42.000 PM kernel[0]: IOThunderboltSwitch<0xffffff806dd5b200>(0x1)::listenerCallback - Thunderbolt HPD packet for route = 0x1 port = 2 unplug = 1

3/29/15 9:37:43.000 PM kernel[0]: IOThunderboltSwitch<0xffffff806dd5b200>(0x1)::listenerCallback - Thunderbolt HPD packet for route = 0x1 port = 2 unplug = 0

3/29/15 9:37:43.000 PM kernel[0]: IOThunderboltSwitch<0xffffff804e9b7c00>(0x0)::listenerCallback - Thunderbolt HPD packet for route = 0x0 port = 2 unplug = 0

I have a very similar setup as the original poster:

Mac Pro (Late 2013)

Processor: 3.5 GHz 6-Core Intel Xeon E5

Memory: 16 GB 1866 MHz DDR3 ECC

Graphics: AMD FirePro D500 3072 MB

Apple Thunderbolt Display (x1)

I was struggling with the same problem (screen flickers black intermittently), but found a solution a few months back that has 100% worked.

Solution:
System Preferences | Displays | Uncheck "Automatically adjust brightness"

Your mileage may vary, but I hope this helps at least one other person. I was very speculative at first that it would make any difference, but I'm happy to say my display has been flicker free ever since.

Good luck!

Having same problem as many have said above and was wondering what everyone's end result was. Did the unchecking "Automatically adjust brightness" work?

Purchased a new Mac Pro in January and noticed the flicker to black intermittently and randomly from the get go and reported it to Apple where we ran all sort of diagnostic/resets without any success. The issue continued, and although new it shouldn't be happening, it didn't crash my system so I worked through it. As time went along many other issues happened too (am a Video Editor) and it was determined my new Mac Pro had a bad logic board so Apple sent me a brand new Mac Pro. Of course, I thought this would also solve the display flickering to black issue too so was quite surprised when I noticed the issue happening again with a new Mac Pro. Finally, I had time to bring the Display into the Genius Bar where they were able see the problem right away. After a week, they replaced the Power Supply 250W and all in one Cable and said I should be set. The issue still persists. Next step is to bring it back to Genius bar where they will replace the logic board in the Display. So in summary, I have had the issue happen from the beginning, on two different new Mac Pros and after sending it into Apple for replacement.

Similar to others:

Mac Pro

OS X Yosemite 10.10.2

3.5 GHz 6-Core Intel Xeon E5

32 GB 1866 MHz DDR3 ECC

AMD FirePro D700 6144 MB

Thanks!