I have two CRT TVs that just recently started producing perfectly straight horizontal lines across them. I thought maybe it was a cable related issue, so I posted in a cable forum but got no usable help.
The lines are very thin, horizontal, spaced fairly close together and run from the top to the bottom of the screen. It's hard to say what color they are so I'd have to go with translucent. They're hardly visible on dark colored screens/pictures, but clearly there on white screens. These lines don't appear to be moving, but they could be. It's hard to tell.
One TV is a 4-5 y/o, 27" CRT SD DTV. The other is around 13 y/o, 20" analog CRT SD TV. They are both hooked up via coaxial cable to a SD cable box. The lines are a lot more noticeable on the 27" TV, but that TV is getting a weaker cable signal (confirmed by checking the statistics in the cable boxes). Sometimes, I don't even see the lines on the 20" TV.
Up until these lines appeared, the 27" TV had vertical waves in it for about three weeks. I noticed the horizontal lines on both TVs around the same time/day. I've also noticed that on two channels, the dialogue is out of sync with the video. So I'm not sure if the problem is cable related or not.
For all I know, maybe these lines are perfectly normal and I've just become hyper aware of them, so that's all I see.
I'm going to try to find a picture of this problem online, because there is no way my camera is going to be able to capture these lines.