It could be many things but a short circuit overloading the power supply is favorite. So, you could spend £60 getting it repaired and the TV will still be well worn.
15 years for a TV is old. As an analogy it would be about 105 years old in human terms :) So, unless it has sentimental value, it's time to get yourself a new puppy,..eh i mean TV.
Cobweb, May 2006