I have a nice big 27" CRT that has started to develop horizontal lines near the top 2 or 3 inches. As the TV stays turned on they 'retreat' back towards the top of the screen. At first they would disappear completely, but now about 1.5" area at the top of the screen remains with these horizontal lines. They distort the image a bit and against a black background they are not noticeable, but white or any other color and you can see them clearly.
I don't even really know how to begin troubleshooting something like this. I thought it might be RF interference, but I moved the TV to a different room of the house, and turned off all the electronic stuff near it and they are still there.
The TV is a Panasonic CT-27D20B TV














