Changing refresh rate for specific monitor

I have 3 monitors, one of which is a CRT, and I need to bump up it's refresh rate to 75/80 to get rid of the flicker, I've used it with my Raspberry Pi and it fully supports up to 100Hz. When I use xrandr it tries to change my 1st monitor, I want my 2nd one changed.

xrandr confirms that I can do this,

HDMI1 connected 1280x1024+2646+0 (normal left inverted right x axis y axis) 338mm x 270mm 1280x1024 60.02*+ 75.02 1920x1080 60.00 59.94 1152x864 75.00 1280x720 60.00 59.94 1024x768 75.08 60.00 800x600 75.00 60.32 720x480 60.00 59.94 640x480 75.00 60.00 59.94 720x400 70.08

I have Intel HD Graphics 4400. Ubuntu 16.04.

2 Answers

Method 1

With the following command

xrandr --output HDMI1 --rate 75

Where the string after --output is the name of the monitor and the number after --rate is the new refresh rate

Or, if you want to make sure the resolution is correct too in the same command

xrandr --output HDMI1 --mode 1280x1024 --rate 75

See man xrandr and the following link to learn more

Method 2

You should have a file monitors.xml (~/.config/monitors.xml)

Edit the file with your favorite text editor

vim ~/.config/monitors.xml

You will see monitors available, and you should recognize them by name.

Here's some example information you will see about a monitor

<vendor>AUO</vendor> <product>0x38ed</product> <serial>0x00000000</serial> <width>1920</width> <height>1080</height> <rate>60</rate> <x>0</x> <y>0</y> <rotation>normal</rotation> <reflect_x>no</reflect_x> <reflect_y>no</reflect_y> <primary>yes</primary>

There's the line

<rate>60</rate>

Replace the current refresh rate with a new one. For example

<rate>75</rate>

Save the file and reboot, and the new refresh rate will take place.

NOTE: Make sure that monitor's resolution supports the refresh rate you are going to change

Well if you want an intuitive GUI tool that shows the refresh rate and resolutions you may want the lubuntu default resolution tool lxrandr as it allows changing refresh rates and resolution by each other not installed by default ubuntu though. Install lxrandr and then open it and click on the advanced tab to change refresh rates. In a drop down option for each column.