I am trying to help my neighbor. She has a Sanyo flat screen tv Model DS20930. The picture she gets is a thin line across the center of the screen.

Hello
Set the brightness, contrast and colour control of that TV to minimum. Watch it in a dark room whether ther are thin white lines across the screen, at about an inch apart, from bottom to top of the screen. If there are lines, that TV needs screen control adjustments. That is, now the screen voltage given to the picture tube went high to some reasons. If you have confidence that you can adjust it, I will guide you.
Open the back cover of that TV. Locate the LOT [Line output Transformer], usually one red thick wire is connected to the top of the picture tube with the help of a rubber ****** and clip. In most TVs it can be located and can be seen as the back cover opened. There are two variable control, fitted, integrated to LOT. Normally the upper one is marked as focus, and the lower one is marked as screen. You shoud adjust this control to avoid these lines.
It is a live service, that is the TV must be switched on during this time, and take causion in every respect not hurt by yoursef and the TV. Keep the children away from you, and an other adult person beside you is better. A liitle turn counterclockwise will remove this problem.