I have a Fujitsu Siemens AMILO L7300 laptop which was originally given me to fix because the power connector socket on the motherboard was non-functional. I replaced that and then discovered the power adapter is also non-functional. I've powered the laptop with a replacement adapter, but the screen displays white with an occasional faint yellow-brown line of colour. If Ilook really hard I can just make out the windows desktop when it finishes booting. I've attached an external disply which displays fine. I've opened the case and 'jiggled' the video signal and video power cables, but it doesn't alter the LCD display at all.
What is the likely source of the fault. As far as I know it hasn't been dropped, and the LCD panel is physically intact. So I'm suspecting some sort of power problem could have affected the display.
Any clues? How to diagnose?