It's most likely the LCD ribbon cable right where it goes into the connector. Many times it will get corroded right there. It's entirely possible that multiple other things are wrong as well but you won't know until you take it apart. If I were you I'd pop off the back panel and metal plate and just take a look at the motherboard to see what seems to be affected the most. In fact if it was me I would remove the motherboard and clean it, then put it back in and clean any connectors and ribbon cables that need it and see if it will work...sometimes that's all it takes.