I just had my surface pro 4 completely die on me yesterday after only 18 months. It locked up on me so I hard power cycled it, but now only the keyboard backlight comes on when you power it up. No "Surface" boot screen, no nothing (the screen backlight doesn't even come on). I have tried every button holding reset combo I could find. I even have let it sit all night and completely drained the battery. The external monitor output shows no signal as well. Pretty sure this thing is dead. Since it is out of warranty it is $450 for a refurbished replacement. What are your thoughts on going through the replacement process vs buying a new Surface Pro (or other device).