MP 6,1 Mac Pro 6,1 and Apple 27” Thunderbolt Display: screen blackout.

[Dorothy Gale]

The display is connected directly to the Mac via Thunderbolt, with no hubs or adapters involved.

The problem occurs sporadically when waking up from sleep. Additionally, the Mac Pro might be running and the screen could flicker, turn black, and won't return until I perform a power cycle or restart it.

macOS correctly recognizes the display, which never goes black during boot or after a restart. The built-in speakers, USB ports, and Thunderbolt port of the display work fine.

There is a LaCie Thunderbolt rugged disk connected to the Display for Time Machine backup purposes. Disconnecting it from the Apple Thunderbolt Display did not resolve the issue. Besides, I can't see it overworking the Mac while the computer is in sleep mode.

There is a Logitech USB dongle required to pair a Logitech MX mouse, presently attached to the display; connecting it to either the Display or the Mac Pro USB ports doesn't make any difference. The issue persists.

The Apple Thunderbolt Display cable is in good condition, with no fraying, even though I needed to apply electrical tape to secure the end where the cable connects to the Mac Pro, it was becoming loose on the outside, similar to what would happen to an iPhone or iPad cable.

Resetting PRAM/NVRAM/SMC didn't help.

There is no setting for "Allow accessories to connect" that I might have accidentally unchecked, which, uneducated guess on my end, might stop the display from sending its signal to the Mac. I found out such a setting only applies to laptops where the display serves as a secondary or external screen.

Another point to consider: At times, a kernel panic is generated, but I'm unable to decipher it beyond 'AppleIntelCPUPowerManagement' or 'xpcproxy' being listed.

The Mac Pro is running Sequoia 15.4, having been OCLP-ed (OpenCore Legacy Patcher). This issue did not occur with 'vintage' Apple Cinema Displays, specifically the 23" and 30" DVI Aluminium models under the same Sequoia installation.

According to System Information, the Firmware version for the Thunderbolt Display is 26.2, and 2.0.7 for the Port Micro Firmware, which aligns with the Thunderbolt Display Firmware Update v 1.2. Apple states this update addresses "a rare issue that may cause the display to go black." However, when I attempt to install the Firmware Update, macOS says 'Your computer does not need this update'. So I guess it's been already applied.

Have you ever experienced the issue of your Apple Thunderbolt display going black? How were you able to solve it? I would greatly appreciate your assistance.

 

[tsialex]

If you have KernelPanics while sleeping/awakening and you see AppleIntelCPUPowerManagement right in the start of the crash log, the most probable culprit is the RTC battery.

Measure the RTC battery voltage, replace with a new Panasonic BR2032 if the voltage is below 3.00V. There are easy to access test points for the battery:

You can download the Apple Technician Guide from this thread:

Mac Pro Cylinder led diagnostics

I bit and paid the $1.99 for that eBay service manual. It is a PDF capture of the web manual using "PD4ML. HTML to PDF Converter for Java", not the true Apple manual PDF. That's why the diagram is cut off as it is formatted for page. 1588006518

forums.macrumors.com

 

[Bigwaff]

Have you ever experienced the issue of your Apple Thunderbolt display going black? How were you able to solve it? I would greatly appreciate your assistance.

Find an Apple OEM Thunderbolt 2 cable. The display can be driven using the Thunderbolt port rather than the attached cable. One of my Thunderbolt displays was displaying the same behavior. Switched to direct TB2 cable and display has worked w/out issues for several years now. Obviously, you can't daisy-chain w/ this setup.

 

[weckart]

Find an Apple OEM Thunderbolt 2 cable. The display can be driven using the Thunderbolt port rather than the attached cable. One of my Thunderbolt displays was displaying the same behavior. Switched to direct TB2 cable and display has worked w/out issues for several years now. Obviously, you can't daisy-chain w/ this setup.

I did this because the TB display I picked up had a fraying cable. Replaced the internal cable with that as there is a tight TB2 socket on the display's internal logic board to connect to. I still get a blackout if the cable gets the slightest knock and it requires a display power cycle in a specific order to resurrect the screen image. Sometimes even that doesn't work and a Mac reboot is necessary. Apparently, it's just a thing with the display and the too loose TB sockets in the 6,1.

 

[eldxmgw]

If you have KernelPanics while sleeping/awakening and you see AppleIntelCPUPowerManagement right in the start of the crash log, the most probable culprit is the RTC battery.

Measure the RTC battery voltage, replace with a new Panasonic BR2032 if the voltage is below 3.00V. There are easy to access test points for the battery:

You can download the Apple Technician Guide from this thread:

Mac Pro Cylinder led diagnostics

I bit and paid the $1.99 for that eBay service manual. It is a PDF capture of the web manual using "PD4ML. HTML to PDF Converter for Java", not the true Apple manual PDF. That's why the diagram is cut off as it is formatted for page. 1588006518

forums.macrumors.com

That's a wonderful approach.
And yes, I've experienced this waking-up phenomenon as you describe it a few times, though not very often. Most of the time it works out fine.

Nevertheless, I'll keep it in mind, and next time I clean the internals, I'll remove the I/O board and replace the 2032 battery.

I don't plan on taking any measurements. For me, it's a given that I'll replace it with a new standard battery after this amount of time.
Thank goodness they didn't install a Dallas clock or something like that. 😉

The tech manual was also excellent. I was missing that.

Thanks for that!

 

[tsialex]

it's a given that I'll replace it with a new standard battery after this amount of time.

Remember, you have to buy a BR2032 and not a CR2032. High Temperature area, CR2032 chemistry with the maximum working temperature of 55ºC is not adequate for the application.

 

[eldxmgw]

Remember, you have to buy a BR2032 and not a CR2032. High Temperature area, CR2032 chemistry with the maximum working temperature of 55ºC is not adequate for the application.

Thanks for the reminder. I would have completely missed that. 😉

 

[vader_slri]

The built-in Thunderbolt 2 cable on the 27” Thunderbolt Displays is a common failure point, even if the cable appears to be physically ok. I bet this is the problem, not your Mac. I’ve picked up a couple of these Thunderbolt Displays for cheap due to this issue. The easiest solution is to connect it to your Mac using the Thunderbolt 2 port on the rear of the display. You’ll obviously need a Thunderbolt 2 cable which is becoming harder and harder to find.

 

[ToniCH]

My 27" TB display didn't wake up from sleep every time. It remained black more often than it did wake up. Tried different cables, computers etc. but no help. Then I bought a known good replacement motherboard for it and swapped it in. After that no problems ever with waking up, it happens instantly when I touch my keyboard.

My combo is MP6,1+Magic kbd and mouse+external USB drives+TB dock etc. The display is directly connected to the machine.

 

[Dorothy Gale]

I bought the Apple Thunderbolt cable, and it seems to have fixed the issue. I found the black version too, and got it as a spare. Thank you so much for your advice; you've been really helpful.