Screen Extremely Dim

Hey Guys

I was fixing a mates Pavilion Dv7, it was having over heating problems. So took it apart to clean the radiator and put new heat transfer paste for the CPU and Graphics. Now that I have put it back together the screen is extremely dim. It looks like a ghost image on the screen. I have to use a torch to see whats going on. I have plugged the laptop into an external screen and works fine, brightness is on full but laptop screen still not right.

Please help