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I have a strange problem with my second external monitor. It won't wake up automatically when my laptop starts, or when the laptop wakes up from standby or sleep mode. It will be on if I manually press the power button (turn it off and then on), or press the signal switch button.

The two external monitors are connected via Dual DVI cable. The primary monitor has no problem. The OS is Ubuntu 14.04 (kernel 3.13.0-59-generic). The primary monitor is ASUS VN248H, the second monitor is ASUS VS247H. The laptop is W530. The graphics card is NVIDIA® Quadro® K2000M 2GB VRAM. The NVIDIA optimus feature is disabled.

How can I fix this?

Here is the output of the xrandr (when the second monitor is still back while it is powered on)

$ xrandr
Screen 0: minimum 8 x 8, current 3840 x 1080, maximum 16384 x 16384
VGA-0 disconnected (normal left inverted right x axis y axis)
LVDS-0 connected (normal left inverted right x axis y axis)
   1920x1080      60.0 +   50.0  
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 521mm x 293mm
   1920x1080      60.0*+
   1680x1050      60.0  
   1440x900       59.9  
   1280x1024      75.0     60.0  
   1280x960       60.0  
   1280x800       59.8  
   1280x720       60.0  
   1152x864       75.0  
   1024x768       75.0     70.1     60.0  
   800x600        75.0     72.2     60.3     56.2  
   640x480        75.0     59.9  
DP-2 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 527mm x 296mm
   1920x1080      60.0*+   59.9     50.0     30.0     60.0     50.0  
   1680x1050      60.0  
   1440x900       59.9  
   1280x1024      75.0     60.0  
   1280x960       60.0  
   1280x800       59.8  
   1280x720       60.0     59.9     50.0  
   1152x864       75.0  
   1024x768       75.0     70.1     60.0  
   800x600        75.0     72.2     60.3     56.2  
   720x576        50.0  
   720x480        59.9  
   640x480        75.0     59.9     59.9  
   480x576        50.0  
   480x480        59.9  
DP-3 disconnected (normal left inverted right x axis y axis)
DP-4 disconnected (normal left inverted right x axis y axis)
DP-5 disconnected (normal left inverted right x axis y axis)
  • Have you tried disabling DPMS via xorg.conf? I'm not sure it'll help but I'm dealing with a similar issue (where my external monitor will go blank periodically/randomly) and, based on your description, looks like it may provide more insight into the actual problem. – Piotrek Dec 16 '15 at 16:25
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I was experiencing the same issue as mentioned by Piotrek (external screen connected via DP turning black randomly or not "waking up" after I locked my computer).

I solved it by going to Display Settings and checking Mirror displays. Then the screens turn on again. Now I am able to switch back to extended display mode.

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