HDMI stops working when DisplayPort is unplugged

I am trying to set up a media centre on a Gigabyte BRIX computer.

I have a monitor connected via the DisplayPort, and a TV connected via the HDMI port. Once it is set up I only intend to use the TV through the HDMI port.

The HDMI connection did not work out of the box, but by adjusting the resolution through the Screen Display GUI, the TV it is working fine as a second monitor.

The problem is, as soon as I unplug the DisplayPort monitor, the HDMI connection stops working. If I boot with only HDMI connected, I don't get any display. (Note, I have tried booting with just HDMI with other TVs, and it works just fine. The fact that I have the 'problem' TV working as a second monitor seems to suggest that there is a configuration solution.)

Also - in case it is relevant - I have an active displayport to HDMI converter, but booting with the TV connected to the DisplayPort through the converter gives me the same results as booting with the TV connected directly to the HDMI port (no display.)

Any help would be greatly appreciated!

Specs: Ubuntu 16.04 LTS; Intel HD Graphics 620 (Kabylake GT2)

Output of xrandr

Screen 0: minimum 320 x 200, current 3600 x 1080, maximum 8192 x 8192
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 connected 1680x1050+1920+0 (normal left inverted right x axis y axis) 433mm x 271mm
   1680x1050     59.95*+
   1600x1200     60.00  
   1400x1050     59.95  
   1280x1024     75.02  
   1440x900      74.98    59.90  
   1280x960      60.00  
   1360x768      59.95  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   640x480       75.00    72.81    66.67    59.94  
   720x400       70.08  
DP-2 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 1872mm x 1053mm
   3840x2160     30.00 +  25.00    24.00    29.97    23.98  
   4096x2160     24.00    23.98  
   1920x1080     60.00*   50.00    59.94    30.00    25.00    24.00    29.97    23.98  
   1920x1080i    60.00    50.00    59.94  
   1680x1050     59.88  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1440x900      59.90  
   1366x768      59.79  
   1280x800      59.91  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94  
   720x400       70.08 

Solution 1:

It may so happen that, the display ports listed in xrandr may be mislabelled because of manufacturer's error or whatever.

So, it will prove useful to experiment by forcing the outputs through the various ports listed by xrandr. One of them would give the output on the port that you would have physically connected the second display to.

So if you have HDMI-1 and DP-2 as the options available, you can try forcing output through both of them(You may want to try with all other options listed in your xrandr output, till you get an output).

xrandr --addmode HDMI-1 1680x1050
xrandr --output HDMI-1 --mode 1680x1050

and

xrandr --addmode DP-2 1680x1050
xrandr --output DP-2 --mode 1680x1050

You may have to play with the resolution to get a properly sized output. As pointed out in the comments, the second set of commands, modified with the correct resolution, that worked for the OP is with 1920x1080 resolution.

The following answer may be referred for more detailed explaination: https://askubuntu.com/a/968522/574724

These questions also might help:

• xrandr not showing my VGA port, instead it lists DP1
• Can I force VGA signal output even when xrandr shows 'disconnected'?