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Thread: Black screen after login - Working with external monitor

  1. #1
    Join Date
    Feb 2016
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    16

    Black screen after login - Working with external monitor

    Hello,

    I've run into some sort of bug where my laptop screen display fails after login. Funnily enough, the system boots just fine when I have my HDMI monitor running through my thunderbolt adapter. This is a pretty big problem for me, as I need to use the laptop in at university. I tried doing some google-ing for similar problems but it is an awkward problem to search. I'm running kubuntu 15.10 with a 4.2 kernel.

    Something I've noticed is sometimes after rebooting in using my external display, very briefly, the aspect ratio on the external display is that of my laptop screen before it fixes itself. I think there has been some sort of miscommunication between my laptop display and the external display and it has somehow 'hardwired' this into it's settings. I've tried removing the thunderbolt adapter and restarting, shutting down and then removing the adapter before boot but neither of these seem to work.

    I'm sorry, I'm not very technically literate and I'm still learning. I really need some help with this.

  2. #2
    Join Date
    Feb 2008
    Location
    Land of fire and drought
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    Hidden!
    Distro
    Xubuntu

    Re: Black screen after login - Working with external monitor

    Thread moved to General Help.

    Boot to the HDMI input, go to 'Display' settings, make sure your laptop monitor is there and on. If it is there but not 'Active', make it so. You should have both screens visible.

    There is also a box to tick in the configuration 'Configure displays automatically'. Is that ticked? If not and you have set up for the HDMI screen only, that is what you'll get in perpetuity, until you manually change it back.

  3. #3
    Join Date
    Feb 2016
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    16

    Re: Black screen after login - Working with external monitor

    I have these settings in the display configuration module. I can't seem to find the automatic settings but I will have a closer look.

    edit - To clarify, I think the desktop is booting thinking it has a second display to the side of it, when infact it doesn't. This leads to a perpetual black screen on my laptop screen. I can access command line from tty1 just fine. I hate to sound desperate but I really am, I need this laptop to bring in to university.

    edit 2 - For what its worth, I unplugged my thunderbolt adapter(thunderbolt to HMDI adapter) while the screens were in use, and working. After I unplugged it some of the applications were still on the other screen. I then tried to go into the display settings, and the screen blacked out, and in a similar fashion to boot up, the system seemed to labour under a task(presumably trying to fix itself). I'm really lost I don't know what to do =/
    Attached Images Attached Images
    Last edited by hermes5; March 7th, 2016 at 12:33 PM.

  4. #4
    Join Date
    Oct 2012
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    148

    Re: Black screen after login - Working with external monitor

    Does this command work?

    Code:
    xrandr --output HDMI1 --off
    You might need to change "HDMI1" to something else if that's not what it is actually called. Use xrandr -q with both monitors plugged in to find out the actual name.

    You might also try setting the laptop screen as primary, like this:

    Code:
    xrandr --output <name of laptop screen> --primary
    I think this option should be in the GUI display configuration options. Maybe it's under advanced? There are also other things you can do with xrandr that might be helpful, like --pos, which should allow you to make the laptop display actually appear on the screen if it is offset. See the man pages for xrandr.

    All this stuff should really work from the GUI, but Plasma 5 is still pretty new and it seems like it has some issues with HDMI displays.
    Last edited by montag dp; March 7th, 2016 at 05:58 PM. Reason: more info and suggestions

  5. #5
    Join Date
    Feb 2016
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    16

    Re: Black screen after login - Working with external monitor

    Thanks for the reply montag!

    I queried xrandr -q and got the following output

    james@vulcan:~$ xrandr -q
    Screen 0: minimum 320 x 200, current 1440 x 900, maximum 8192 x 8192
    LVDS-1 connected primary 1440x900+0+0 (normal left inverted right x axis y axis) 331mm x 207mm
    1440x900 59.90*+
    1152x864 59.96
    1024x768 59.92
    800x600 59.86
    640x480 59.38
    720x400 59.55
    640x400 59.95
    640x350 59.77
    DP-1 connected (normal left inverted right x axis y axis)
    1920x1080 60.00 + 50.00 59.94
    1920x1080i 60.00 50.00 59.94
    1680x1050 59.88
    1400x1050 59.95
    1600x900 60.00
    1280x1024 75.02 60.02
    1440x900 59.90
    1280x800 59.91
    1152x864 75.00
    1280x720 60.00 50.00 59.94
    1024x768 75.08 60.00
    800x600 75.00 60.32
    720x576 50.00
    720x480 60.00 59.94
    640x480 75.00 60.00 59.94
    720x400 70.08
    DP-2 disconnected (normal left inverted right x axis y axis)
    DP-3 disconnected (normal left inverted right x axis y axis)
    VGA1 disconnected
    VIRTUAL1 disconnected
    I proceeded to turn off DP-1 which turned off the external monitor. It looked to have work as the laptop screen spun up, but then it died a black screen death =/. I have to go to university now, I'll have a look at the man pages while I'm there. Hopefully I can get it working for tomorrow.

    edit - Rebooted and it is working. 2nd monitor is still off but I'll look at the man pages to get that setup properly. Thanks montag
    Last edited by hermes5; March 7th, 2016 at 10:51 PM.

  6. #6
    Join Date
    Oct 2012
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    148

    Re: Black screen after login - Working with external monitor

    I'm glad it worked! I had a similar issue awhile ago when I unplugged the HDMI display and it just messed everything up. Since then I've had a few updates to Plasma that problem hasn't happened again. But now I normally just use a script to toggle the HDMI display on/off. It uses the following commands:

    On:
    Code:
    xrandr --output HDMI1 --auto --right-of LVDS1
    and off:
    Code:
    xrandr --output HDMI1 --off
    I also have some commands in the script to automatically set the audio profile so that it plays through HDMI when it's plugged in. It has been much more convenient to me than going through the system settings every time I connect/disconnect the display.

  7. #7
    Join Date
    Apr 2013
    Beans
    2

    Re: Black screen after login - Working with external monitor

    I think you should mark this as [SOLVED]
    I've been having this problem for about a week now and just couldn't find a solution, and was bout ready to reformat. Turning off, in my case, VGA1 via xrandr resolved the problem successfully.

    Thank you!

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