What you're seeing are called retrace lines, and are the result of a bad vertical blanking circuit. Normally, the TV blanks these out when the CRT goes to retrace. On most newer TVs, this fuction is integrated into an IC circuit that also controls other video processing functions. Pinpointing the bad part can be hard, so you'll need the help of a professional TV tech that has experience in this kind of diagnosis. This isn't one of those things you want to try and fix yourself.
Depending on how old the TV is, you may want to consider replacement as an option, since the repair cost will probably be over $150 bucks. Look at how much a replacement set would cost, and if the repair is half the price or more, new may be a better option.
Questions like this can be hard to answer, but some members have had better luck getting answers when they post a screenshot of the problem.
what is a screenshot
A screenshot is picture of the TV screen when it is exhibiting the problem.
Pictures speak 1000 words.
What you're seeing are called retrace lines, and are the result of a bad vertical blanking circuit. Normally, the TV blanks these out when the CRT goes to retrace. On most newer TVs, this fuction is integrated into an IC circuit that also controls other video processing functions. Pinpointing the bad part can be hard, so you'll need the help of a professional TV tech that has experience in this kind of diagnosis. This isn't one of those things you want to try and fix yourself.
Depending on how old the TV is, you may want to consider replacement as an option, since the repair cost will probably be over $150 bucks. Look at how much a replacement set would cost, and if the repair is half the price or more, new may be a better option.
Best of luck.