I've been working on a Dell Inspiron 8100. The LCD was remaining
dark, after bootup, but I could get a clear picture on an external
CRT.

I determined the problem was mostly likely to be the CCFL tube, so I
ordered a replacement from JKL. The tube replacement went without a
hitch, and now the display lights up when booting.

However...the display is still unusable. I can see that output from
the video card is reaching the display, because as the computer
software boots, I can see the display change, for example when its at
the "windows xp loading screen" I can see vertical lines running the
full height of the screen approximately in the right place
(horizontally) for the progress meter that XP displays at that stage.

I checked to make sure the flex/ribbon cable had firm connections with
the LCD and the video card...without any appreciable improvement.

My working theory is that I need to replace the ribbon cable, that it
has developed a flaw.

Does the inverter simply serve the same role as a the ballast in a
traditional office or shop light? Or does it play other roles in the
LCD operation?

Iain