Trouble shooting: xrandr, external monitor remains blank (black)

[Steven Webb]

Update:

My computer froze and when I rebooted (sysrq + RUB) the memcheck
displayed on the external monitor (which it hadn't been doing) and
then everything resumed correctly. I'm not sure why the external
monitor was working correctly under microsoft windows and nowhere
else.

Steve.

2008/7/9 Steven Webb <steven.daniel.webb at gmail.com>:
> Problem: The external ViewSonic VA1912w monitor attached to my laptop
> at work stays blank (black) and refuses to display anything. The light
> on the monitor stays orange (no signal?). My external NEC monitor at
> home works correctly. The ViewSonic works correctly when I boot into
> microsoft windows; therefore, I do not believe that the problem is
> hardware based.
>
> xrandr appears to work correctly; however, the monitor does not switch on:
>
> two:~/>xrandr
> Screen 0: minimum 320 x 200, current 1280 x 800, maximum 2720 x 900
> VGA-0 connected (normal left inverted right x axis y axis)
>  1440x900       59.9 +   59.9
>  1152x864       74.8
>  1024x768       84.9     75.1     70.1     60.0
>  832x624        74.6
>  800x600        84.9     72.2     75.0     60.3     56.2
>  640x480        84.6     75.0     72.8     66.7     60.0
>  720x400        70.1
> LVDS connected 1280x800+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
>  1280x800       59.5 +   60.0*
>  1280x768       60.0
>  1024x768       60.0
>  800x600        60.3
>  640x480        59.9
> S-video disconnected (normal left inverted right x axis y axis)
> two:~/>xrandr --output LVDS --pos 0x100 --output VGA-0 --pos 1280x0 --auto
> two:~/>xrandr
> Screen 0: minimum 320 x 200, current 2720 x 900, maximum 2720 x 900
> VGA-0 connected 1440x900+1280+0 (normal left inverted right x axis y
> axis) 410mm x 256mm
>  1440x900       59.9*+   59.9
>  1152x864       74.8
>  1024x768       84.9     75.1     70.1     60.0
>  832x624        74.6
>  800x600        84.9     72.2     75.0     60.3     56.2
>  640x480        84.6     75.0     72.8     66.7     60.0
>  720x400        70.1
> LVDS connected 1280x800+0+100 (normal left inverted right x axis y
> axis) 0mm x 0mm
>  1280x800       59.5 +   60.0*
>  1280x768       60.0
>  1024x768       60.0
>  800x600        60.3
>  640x480        59.9
> S-video disconnected (normal left inverted right x axis y axis)
>
> OS: Ubuntu Hardy Herron 8.04
> Laptop: Toshiba A70/7001
> Video Card: ATI Radeon Mobility 9100IGP
> External Monitor: ViewSonic VA1912w
> Native res on external monitor 1400x900
>
> This laptop/monitor combination works correctly under microsoft
> windows, but only when I enable composite synchronization (I don't
> know how to do this under X).
>
> Any information/advice would be greatly appreciated. I hope I have
> provided all relevant info.
>
> Cheers.
>
> Steve.
>