Welcome to the forum Keith, but as Steve says above you are going to have to supply more specific information to make analysis of your problem even remotely possible.
Are the white lines:
Are they wide or narrow?
Do they cover the whole picture or just parts of it?
Are the lines the full length of the screen in whatever direction?
Repeatable? If you rewind do they occur in the same places?
Do they sustain throughout of the whole of the discs or just some of the time?
Do they only occur with pre-recorded discs and not on self-recorded discs?