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I am running 12.04 on a Toshiba Portege laptop. The graphics card is an Intel 945GM/GMS. The 2nd monitor is an Asus (Ancor Communications 22"). When I connect the monitor to the computer the monitor is recognized but nothing is displayed. There is only a black screen. The monitor is not receiving any signal from the computer.

Kevin
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  • Ubuntu 12.04 doesn't automatically enable the external monitor, from my testing. Did you try enabling it in the Display settings and giving it a resolution to display? (Settings -> Display) – Thomas Ward Jul 04 '14 at 02:09
  • @ThomasW., in the display settings I did set the button to "On". – Kevin Jul 04 '14 at 03:26
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    I followed these steps at another answered question and it seemed to correct the problem: http://askubuntu.com/a/370928/46496 – Kevin Jul 04 '14 at 04:00

6 Answers6

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I've had this issue for a long time and tried allot of tinkering in the terminal and nothing helped me.

What ended up helping me was, turning on the laptop with the screen connected via HDMI, and then removing the monitor from the power, and plugging it in again.

Hopefully this helps more people.

I'm using Ubuntu 20.04 and a Samsung S22D300.

Luís Santos
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  • omg this is what finally did it for me. Thanks! Unplugging and re-plugging the HDMI cable did nothing but unplugging the power cable did the trick. Weird how these things work – T. Kau Jun 17 '21 at 12:22
  • Like a magic! Maybe this is about boot area. 1) Not signing out. Do turn off. 2) After second reboot, you don't need plugging on/off the monitor. – Jehong Ahn Nov 07 '22 at 16:34
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Actual for ubuntu 18 and 20:

Try to (independently or together):

  1. adjust screen resolution for not-primary monitor
  2. adjust screen refresh rate (decreasing for 2nd monitor helped)
  3. if you have nvidia graphics choose nvidia driver in 'Software & Updates'. this may cause strange result after rebooting. i had to choose built-in monitor as primary to solve it
ilya antipyev
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  • Many hours trying various methods and tinkering with commands. Changing the non-primary monitor resolution finally worked. This is so weird. – RaidasGrisk Aug 17 '23 at 12:15
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Updating this question.

In later versions of Ubuntu, for example >14, I think we should first check displays as previously discussed, but if that doesn't work out, to check drivers and graphics hardware of our devices. I have run into multiple monitor problems many times, but most of the time it's just a driver mismatch issue. For example, as of late I ran into a similar problem with multiple monitors being unrecognized upgrading from Ubuntu 17.10 to the latest 18.04.

In general, I would recommend:

  1. Upgrade Ubuntu, as 14, 16.04, and 18.04 are awesome.
  2. Check if you use Nvidia graphics or other, as Nvidia graphics usually works best with their own drivers in Ubuntu. If other, I have used the xorg noveau driver. You can find drivers and auto install by clicking

Ubuntu 16.04-18.04 show applications > Software and Updates > Additional Drivers

youtube of the process

We just don't want to make things more complicated than they need to be, and manually writing xorg.conf could get complicated very quickly.

piie
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Turn off Secure Boot as indicated here https://wiki.ubuntu.com/UEFI/SecureBoot/DKMS. This solution also solves the problems with VirtualBox in Ubuntu.

Héctor Oses Rosa
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Work for me Ubuntu 20.04:

  1. ubuntu-drivers devices
  2. sudo ubuntu-drivers autoinstall
Sergey Mischenko
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try going into 'Setting -> Display' and select the Asus monitor.

Edit:

After more research I believe this is related to a bug with Intels 945GM chipset.

I also found one post that said they were able to get the monitor to work by:

  1. disabling the 'visual effects'
    • System > Appearance > Visual Effects is set to None
  2. connecting monitor
  3. Settings -> Display
  4. clicking 'detect monitor'
  • The monitor is set to on after I click the 2nd monitor. If I turn off the laptop screen the laptop screen will go black and the monitor also stays black. I assume I am getting a message to revert back to the previous configuration because after less than a minute it will go back to the previous setting. It looks like the monitor is not getting any signal even though the OS is recognizing that the monitor is plugged in. – Kevin Jul 04 '14 at 03:29