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

[Steven Webb]

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.
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