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User profile for user: TwoSlick
TwoSlick Author
User level: Level 2
275 points

Thunderbolt Display blanking for a second

I have a Thunderbolt Display connected to The latest Mac Pro with D700 video cards. Since upgrading to Yosemite I've noticed two problems with the display. First, about every ten minutes or so, my screen will go completely black for about one second, then turn back on. The second problem is that sometimes that after putting the machine to sleep, or using a key combo to turn off the display, it will just turn right back on after a few minutes. Sometimes I come back to my machine hours later and the login screen is showing. I have the screen saver set, and the energy save settings set to turn these things off, but the screen turns on and stays like that. I've resorted to just turning the machine completely off, so I don't needlessly waste money. Anybody else seeing this kind of problem?

Mac Pro, OS X Yosemite (10.10)

Posted on Oct 27, 2014 3:48 PM

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User profile for user: sterling r
sterling r
User level: Community Specialist

Oct 30, 2014 12:02 PM in response to TwoSlick

Hey there TwoSlick,


It sounds like you're seeing some unexpected behaviour when using an external thunderbolt display with your Mac Pro. I would use the troubleshooting in the following article to help resolve the issue:


Apple computers: Troubleshooting issues with video on internal or external displays

Check connections

When using an external display be sure to check the following:

  1. If you're using an Apple notebook, confirm the AC power cable or adapter is securely connected to the computer and the cable providing power to the display is also secure. It is always good to have your notebook connected to AC power when an external display is in use.
  2. Confirm display adapters are fully seated in their respective connections and that they are supported models and for the computer and display. Refer to these articles to assist you with adapter compatibility and further configuration information:
  3. Remove all display cable extenders, KVM switches, or other like devices and retest to determine if the issue is resolved.
  4. Try unplugging the video adapter or cable and then plug it back in.
  5. If more than one video adapter is in use (or "daisy-chained"), troubleshoot by using only one adapter.

    Example: A mini DisplayPort to DVI adapter connected to a DVI to HDMI adapter is an unsupported configuration because there is a series of adapters in use.

  6. If available, try using a different display and or adapter (or use a different connector by using DVI instead of VGA, for instance).

Reset the system

You can reset the Mac's parameter RAM and SMC.

Reset the resolution

Start by resetting the Mac's parameter RAM. If the display does not come up, was previously set to an unsupported resolution, and still results in no video:

  1. Start up in Safe Mode.
  2. From the Apple () menu, choose System Preferences.
  3. Choose Displays from the View menu to open the preferences pane.
  4. Select any resolution and refresh rate that your display supports.
  5. Restart your computer.


Thank you for using Apple Support Communities.

All the very best,

Sterling

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Thunderbolt Display blanking for a second

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