Hi
Ok when your screen does not light up is your PC still active ??? Hard drive turning ? If so then if you can get hold of an external monitor plug your laptop into the external monitor and see if you can see a display on it. Possible problems are failed screen , GPU ( graphics processing unit )failed , or possibly the RAM ( Memory) needs re-seating or has failed. We can identify better when you get the monitor connected . Post me your findings
Checkurtech