Question

7

External monitor recognized but getting "no signal"

rated 0 times [ 7] [ 0] / answers: 1 / hits: 53399 / 1 Year ago, tue, february 28, 2023, 7:34:33

I'm running 12.10 dual booted with windows 7 (nvidia optimus). I have no idea what might be wrong because:

the monitor works on windows

it worked on ubuntu for over a year and even now the splash screen shows up on the external monitor while ubuntu is booting

the monitor is detected and shows up in the workspace switcher

I connected it to another monitor through hdmi and it works fine

it works fine through VGA (but for some reason it's not as sharp)

changing the resolution didn't help

changing cables didn't help

here's my xrandr output:

Screen 0: minimum 320 x 200, current 3286 x 1080, maximum 8192 x 8192

LVDS1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 293mm x 164mm

   1366x768       60.0*+

   1360x768       59.8     60.0  

   1024x768       60.0  

   800x600        60.3     56.2  

   640x480        59.9  

VGA1 disconnected (normal left inverted right x axis y axis)

HDMI1 connected 1920x1080+1366+0 (normal left inverted right x axis y axis) 531mm x 299mm

   1920x1080      60.0*+   50.0     60.0     25.0     30.0  

   1600x1200      60.0  

   1680x1050      59.9  

   1680x945       60.0  

   1400x1050      74.9     59.9  

   1600x900       60.0  

   1280x1024      75.0     60.0  

   1440x900       75.0     59.9  

   1280x960       60.0  

   1366x768       59.8  

   1360x768       60.0  

   1280x800       74.9     59.9  

   1152x864       75.0  

   1280x768       74.9     60.0  

   1280x720       50.0     60.0  

   1024x768       75.1     70.1     60.0  

   1024x576       60.0  

   832x624        74.6  

   800x600        72.2     75.0     60.3     56.2  

   720x576        50.0  

   848x480        60.0  

   720x480        59.9  

   640x480        72.8     75.0     66.7     60.0     59.9  

   720x400        70.1  

DP1 disconnected (normal left inverted right x axis y axis)

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4 Years ago

answered 1 Year ago istictroubli · Accepted Answer

I had the exact same problem as the question poster: Ubuntu 12.10, Nvidia card, monitor connected via HDMI, using nouveau driver, monitor worked before (with the same setup), the monitor is detected and enabled in Ubuntu, but no signal to monitor.

The temporary solution: I'm running Ubuntu on a laptop and there is a special key on my keyboard which allows me to enable/disable external displays (in my case the key is Fn + F7, this differs per laptop). So I just pressed that key combination and the external monitor immediately was turned on.

EDIT:

Though the key combination to enable the external monitor works, you'll have to repeat this every time you reboot. I found a way to have the external monitor automatically detected and enabled at the login screen (after a reboot). And when you login, the previous settings for your monitors are restored, as you would expect. Here's how to do it:

Note: I only tested this with an Nvidia card. And before you continue, I recommend you install SSH first (sudo apt-get install ssh) to be safe. In the case something goes wrong and both internal and external monitor stop working, you can always undo whatever you did by logging in from another computer via SSH (e.g. ssh [email protected]). So make sure you know the IP address of your computer in the network.

First of all, run sudo apt-get install v86d in a terminal to install the v86d package.

Run gksu gedit /etc/initramfs-tools/modules or sudo vim /etc/initramfs-tools/modules and add the following line at the end of the file (replace 1280x1024 by the resolution of your internal monitor):

uvesafb mode_option=1280x1024-24 mtrr=3 scroll=ywrap

save and exit.

Create the file /etc/initramfs-tools/conf.d/splash by running gksu gedit /etc/initramfs-tools/conf.d/splash or sudo vim /etc/initramfs-tools/conf.d/splash with the following content:

FRAMEBUFFER=y

save and exit

Now you need to update the initramfs image because we changed some configurations. Do this by runnning sudo update-initramfs -u.

Now reboot your system and your external monitor should get a signal as soon as the Ubuntu login screen appears.