, you'll have to replace the whole plasma screen to fix it. It's the most expensive
part of the TV.
The web link below is the cheapest place to get a new screen.
If your TV is model 42PC3D, they don't have your screen in stock right now. If you look at the other screens that are 42", the are $350 and up. Other web site will charge more than double for the same screen.
Sorry to give you bad news.