Hemlock70
Level 1 (0 points)

Q: Mac Pro won't display after switching screens

Ok so this is a strange problem but it's very annoying (at least to me). I just purchased a LG Ultrawide 29" display and connected it via HDMI cable to my Mac Pro (Home machine) and a second HDMI cable to my Macbook Pro (office machine). Both the Mac pro / Macbook pro work well with the large screen, HOWEVER, when I am using my Mac pro and select the onscreen toggle to switch to HDMI 2 connection, it works and switches to my Macbook pro. But when I try switching back to HDMI 1 (Mac Pro), it just comes back with a black screen and says no signal. Even if I replug the HDMI cable it doesn't work. I've set the sleep timer to 3 hours, still doesn't help. I know it hasn't gone to sleep because itunes can be playing when I switch and it remains playing music all the way through and continues when I try to switch back. The only way I've been able to recover is long press the power key on my Mac Pro and restart.

 

The only reasonable difference I am aware of is the Macbook pro is running Yosemites, while my Mac Pro is running Beta El Capitan. I have a feeling this is probably the cause, but just wanted to know if anyone else has solved this in some way.

 

Thanks

Mac Pro (Late 2013), Other OS, El Capitan Beta

Posted on Dec 21, 2015 12:33 AM

by alex_h1,Solvedanswer
alex_h1 alex_h1
Community Specialists
A:

Hello Hemlock70,

Thanks for using Apple Support Communities.

 

I understand that your external display is remaining completely black, with a no signal message, when switching displays.  To get help with troubleshooting this issue, please go through the steps in the link provided below.

 

Get help with video issues on external displays connected to your Mac

 

 

Take care.

Posted on Dec 22, 2015 8:00 AM

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Hemlock70

Q: Mac Pro won't display after switching screens

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  • Helpful answers

  • by alex_h1,Solvedanswer

    alex_h1 alex_h1 Dec 22, 2015 8:00 AM in response to Hemlock70
    Community Specialists
    Dec 22, 2015 8:00 AM in response to Hemlock70

    Hello Hemlock70,

    Thanks for using Apple Support Communities.

     

    I understand that your external display is remaining completely black, with a no signal message, when switching displays.  To get help with troubleshooting this issue, please go through the steps in the link provided below.

     

    Get help with video issues on external displays connected to your Mac

     

     

    Take care.

  • by Hemlock70,

    Hemlock70 Hemlock70 Dec 22, 2015 5:01 PM in response to alex_h1
    Level 1 (0 points)
    Dec 22, 2015 5:01 PM in response to alex_h1

    Tried these, it doesn't help. As mentioned, it only becomes an issue if I switch away from my Mac Pro (switch to the different HDMI connection on the screen) and then switch back. It will remain a black screen and then state no signal. None of these suggestions worked from the url.

  • by alex_h1,

    alex_h1 alex_h1 Dec 23, 2015 6:16 AM in response to Hemlock70
    Community Specialists
    Dec 23, 2015 6:16 AM in response to Hemlock70

    Hello Hemlock70,

     

    If you've followed all of the steps in the aforementioned article, then you will need to follow the final step:

     

    Get more help

    If you've tried these steps and your display still isn't working, contact Apple Support to get more help. 

    Diagnostic fees may apply for issues not covered under warranty or the AppleCare Protection Plan (APP).

     

    Take care.