EMC 2133 Vertical lines on screen. How to figure out the cause?

Hey folks, these lines have appeared gradually over a few years. They are not so bad I can't use the computer. But I'd like to try and fix them if possible.

Can you please tell me what must I do to to figure out what is causing these lines (i.e. to determine if it's a cable, the screen, the logic board, etc?). And in what order it would be wise to make the investigation?

Thanks and regards,

Greg