I'm using Ubuntu 16.04 installed on Lenovo ThinkPad T500 laptop with two external monitors connected via display and VGA ports.
I think the issue started after I upgraded to Ubuntu 16.04. But I'm not sure about this.
Occasionally at some random moment one of the monitors turns off. It looks like there is no signal on the monitor. In 2-5 seconds the monitor turns on. This might happen several times in a row with small delays or might not happen for a long time. Both monitors might turn off at the same time or one by one.
I do not understand why this happens. Either I do not understand what should I do to reproduce the issue. Last time (a moment before I wrote this) this happened when I switch to a different tab in Google Chrome and pause YouTube music video. But when I try to do the same one more time the issue is not reproduced. I kept using the computer all the time looking at the screen and writing this question at the moment when issue happened
I failed to find any signs of the issue in the logs.
My issue looks close to Monitor turning off randomly Ubuntu 13.10 with the differences that only one monitor might turn off instead of two and they turn on automatically.
By coincidence I've entered the command
xset -q and pressed enter key right at the moment when the monitor turned off. I waited for several seconds and saw the result
$ xset -q Keyboard Control: auto repeat: on key click percent: 0 LED mask: 00000000 XKB indicators: 00: Caps Lock: off 01: Num Lock: off 02: Scroll Lock: off 03: Compose: off 04: Kana: off 05: Sleep: off 06: Suspend: off 07: Mute: off 08: Misc: off 09: Mail: off 10: Charging: off 11: Shift Lock: off 12: Group 2: off 13: Mouse Keys: off auto repeat delay: 500 repeat rate: 33 auto repeating keys: 00ffffffdffffbbf fadfffefffedffff 9fffffffffffffff fff7ffffffffffff bell percent: 50 bell pitch: 400 bell duration: 100 Pointer Control: acceleration: 5/1 threshold: 5 Screen Saver: prefer blanking: yes allow exposures: yes timeout: 0 cycle: 0 Colors: default colormap: 0x22 BlackPixel: 0x0 WhitePixel: 0xffffff Font Path: /usr/share/fonts/X11/misc,/usr/share/fonts/X11/Type1,built-ins DPMS (Energy Star): Standby: 0 Suspend: 0 Off: 0 DPMS is Enabled Monitor is On
What can I do to investigate the issue? What log files should I check? I failed to find any signs of the issue anywhere in the system.
Is this a known issue? I might describe it wrong when searching for it and thus failed to find it.
How can I understand if it is a hardware or software issue? I might install Windows and see if the issue happens with Windows or not. But may be there might be an option to check this using Ubuntu.
What can I do to prevent the issue?
Following suggestion in the answer I tried to do the following to reduce the refresh rate on my screens. I had a refresh rate 59.95 Hz and decided to change it to 58 Hz.
Identify existing refresh rate
Created parameters for the new mode
$ cvt 1920 1200 58 \# 1920x1200 57.93 Hz (CVT) hsync: 72.01 kHz; pclk: 185.50 MHz Modeline "1920x1200_58.00" 185.50 1920 2048 2248 2576 1200 1203 1209 1243 -hsync +vsync
Registered new mode
$ xrandr --newmode "1920x1200_58.00" 185.50 1920 2048 2248 2576 1200 1203 1209 1243 -hsync +vsync
Added this new mode to both screens
$ xrandr --addmode DP1 1920x1200_58.00 $ xrandr --addmode DP2 1920x1200_58.00
Selected this newly added mode for both screens
$ xrandr --output DP1 --mode 1920x1200_58.00 $ xrandr --output DP2 --mode 1920x1200_58.00
As a result now
xrandr -q shows the following output
$ xrandr --query Screen 0: minimum 8 x 8, current 3840 x 1248, maximum 32767 x 32767 eDP1 connected (normal left inverted right x axis y axis) 1920x1080 60.00 + 59.93 1680x1050 59.95 59.88 1600x1024 60.17 1400x1050 59.98 1600x900 60.00 1280x1024 60.02 1440x900 59.89 1280x960 60.00 1368x768 60.00 1360x768 59.80 59.96 1152x864 60.00 1280x720 60.00 1024x768 60.00 1024x576 60.00 960x540 60.00 800x600 60.32 56.25 864x486 60.00 640x480 59.94 720x405 60.00 640x360 60.00 DP1 connected 1920x1200+0+48 (normal left inverted right x axis y axis) 518mm x 324mm 1920x1200 59.95 + 1920x1080 60.00 1600x1200 60.00 1680x1050 59.95 1280x1024 60.02 1280x960 60.00 1024x768 60.00 800x600 60.32 640x480 60.00 720x400 70.08 1920x1200_58.00 57.93* DP2 connected primary 1920x1200+1920+0 (normal left inverted right x axis y axis) 518mm x 324mm 1920x1200 59.95 + 1920x1080 60.00 1600x1200 60.00 1680x1050 59.95 1280x1024 60.02 1280x960 60.00 1024x768 60.00 800x600 60.32 640x480 60.00 720x400 70.08 1920x1200_58.00 57.93* HDMI1 disconnected (normal left inverted right x axis y axis) HDMI2 disconnected (normal left inverted right x axis y axis) VIRTUAL1 disconnected (normal left inverted right x axis y axis)
I'm checking if the issue repeats or not now. If it does not this means that I've got the solution and I'll mark it as answer.
I still do not know how to permanently store these settings, I guess I should add a new file to the
/usr/share/X11/xorg.conf.d folder following recommendations in this document. I'm going to study this when I see that the issue is fixed.