I have a hp pavillion dv6-2088x.?

I received a new battery after mine went out, but shortly after the screen would just go black on me during games or movies. Now the machine will not start up at all. I have taken it apart and cleaned the heat sink and applied new thermal paste, but no bueno. Anybody have any other suggestions? The warranty went out in between the week it took to get my new battery shipped to me, yay.