Interference - I've found the problem, how to solve it !?
I've had a nagging problem with my car pc for a few months in that faint horizontal lines scroll across the screen when the pc is on.
I finally got round to checking it out today and found that when the screen is plugged into the mains there are no such lines.
At the moment, the screen is powered using a (hacked) molex splitter that also runs to the hard disk drive. I guess the noise on the screen must come from the HDD (thinking about it the lines are probably proportional to HDD activity).
So, how can I smoothen out the supply. A capacitor perhaps?