I need to pick the community's brain.
I have a Samsung Series 3 NP355V5C-A01UB, That i was asked to replace the LCD in because it was cracked. so I ordered a replacement screen, installed everything, it worked so I gave it back to the friend.
Call back from the friend saying the screen is still broken. Get the laptop back and find out that the new screen will not illuminate at all. seems like the backlight is out. swap for the old broken one. backlight comes on. and works minus the crack. diagnose little bit more and decide the replacement is faulty.
I did notice some holes in the sheathing of the internal video cable. but no wires were damaged. So I ordered a replacement video cable. same result backlight on new LCD does not work, old broken one does. Next I sent the LCD back and the company tested and found the LCD in good working order. Well crap.... I can not think of any reason this would not work, checked the seating of both cables repeatedly.
Laptop does work just fine with an external monitor. so at least that part of the GPU is good.
P.S. This is why I hate Laptops.