Are these thin lines, or more like bands across the screen, maybe an inch or more high? Regular speed, drifting slowly up the screen over the course of a few seconds, with more coming onto the bottom of the screen at regular intervals, or completely random timing and speeds? Are the lines perfectly horizontal, or slanted about 30 degrees? Are they like an area of different contrast/brightness to the rest of the picture, or an actual line of different colour running through the picture on the monitor?