Ubuntu 14.04 stopped detecting my HDMI montor

Question

One normal day I started up my Acer Aspire (NVIDIA GEFORCE 720m) running Ubuntu 14.04 and the HDMI screen had stopped working. This has worked fine for ages and there is no reason I can see that it would spontaneously stop working except perhaps, to make me cry. I have read endless posts and messed around with the proprietary NVIDIA drivers and nothing has made any difference. Can anyone help me debug this??

xrandr is assuring me that the HDMI screen is not connected:

     Screen 0: minimum 320 x 200, current 1366 x 768, maximum 32767 x 32767
     eDP1 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
     1366x768       60.1*+
     1360x768       59.8     60.0  
     1024x768       60.0  
     800x600        60.3     56.2  
     640x480        59.9  
     DP1 disconnected (normal left inverted right x axis y axis)
     HDMI1 disconnected (normal left inverted right x axis y axis)
     VIRTUAL1 disconnected (normal left inverted right x axis y axis)

Solution

I have managed to make the screen work again but I am not sure how repeatable the fix is. I first purged kdm and nvidia settings and then re-installed nvidia-settings and then switched to the gnome shell on login. This combination of randomness seemed to bring it back to life temporarily. This morning I was back to having issues although this time with the error:

"Could not switch the monitor configuration. Could not find a suitable configuration"

xrandr was showing the HDMI1 as connected.

To fix this I ran

sudo dpkg-reconfigure -phigh xserver-xorg

First time out I rebooted - same issue, second time out I ran with the HDMI cable attached and didnt make any difference. Third time I removed cable, ran above command and re-attached cable and lo! there was life.

Hope that helps someone else even though it is the product of random frustrated hacking

Comments

[individuo7]

same problem, acer f550c, nvidia 720m, ubuntu 14.04, nouveau driver

[Mike Miller]

Yes tried the cold boot technique. No avail, have put a part formed answer below if it helps anyone