Chosen Solution
It seems like the screen backlight is up but no display other than the blank dark screen….
This problem can be either the laptop display or the GPU/motherboard. You can test the GPU by connecting an external monitor, if the monitor displays then the problem is in the laptop display. The laptop display could have a problem with the back light, if you shine a bright light onto the display and you can see icons on the desktop then the problem is the back light. If all you see is blank then the problem is the laptop display.
HP laptops are tops soldered at the factory, meaning they are baked. A temporary fix if it dies on the road is using a hair dryer. The permanent fix is by rebaking it. https://www.youtube.com/watch?v=G65-ncBx…
You can also try this for a reflow procedure. http://www.deskdecode.com/how-to-fix-a-l…
You can use reflow to fix ANY top soldered board including automotive and television applications.
