If your laptop beep 3 times and nothing comes on screen the simple solution is ...
1. don't need to diassamble laptop.
2. take a blanket and open laptop in L shape.
3. cover the laptop by blanket from all keyboard, processor fan and screen bottom side (the air of processor fan should not be crossed).
4. turn on laptop, it will beep 3 time and just leave it for 1hour. ( keep remember charger and bettery both should be connected to laptop and hot air of fan should not be leak from blanket, coz the hot air will heat nvidia chipset automatically).
5. After 1 hour, take out laptop from blanket and and restart it, it will turn on and work.
99 % will work.