At 2011-05-05 1:48 pm Paul Jeroni wrote in sci.electronics.repair,
"You must connect the shields, the waveforms on the scope are all
noise."

OK. With the shield of the scope lead connected to the shield of
composite output on the Armada, these are the signals while the
BIOS setup is running and when X is running in Linux.
http://members.shaw.ca/peasthope/ArmadaBIOS.jpg
http://members.shaw.ca/peasthope/ArmadaWithX.jpg

Two details. Normally the Armada is not grounded.
The external power supply has a ground pin on the plug but,
as I understand, the DC output is isolated. Secondly, the
composite signal is very jumpy. The two traces were taken
using the digital storage capability of the scope.

In these images, the big wave is the vertical refresh and the
horizontal sweep isn't resolved at this speed of the scope? So
what can be done to dissect the composite signal enough to see
why the BIOS gives an image on the TV and X does not?

I haven't ruled out use of Windows and Powerstrip as suggested
by Adrian C. Just want to apply the scope effectively as a
first step.

Thanks, ... Peter E.