On Fri, 12 Nov 2010 07:05:34 +0000, Clyde
wrote:

Hi. This monitor has a strange fault. When switched on without signal
the screen illuminates and the "check signal cable" display moves around

That's a healthy sign.

However, when I connect a signal, I get a brief
screen of garbled lines (very brief indeed) then the backlights go out.

That could indicate that you supply an out of range signal.
Either too much resolution or too high a refresh rate.
(640 x 480 should be fine, but at more than 60 Hz some LCDs still
prefer to stay asleep :-)

--
Kind regards,
Gerard Bok