HP Pavilion Dv7 1130el Display :: Screen Goes Black - Can Still Hear Music

It's about my old notebook, hp pavilion dv7 1130el bought 5 years ago, it always wokerd fine but now its screen goes black without reasons... at first I thought it might be overheating, but that's totally random:

-sometimes works even when is hot
-sometimes goes blackafter I turn it on and then open google
-sometimes works for a while, when its not hot, and then goes black
 
I don't have a second monitor to connect it, but even if the screen goes black I can still hear the music from youtube, so I guess it's just the screen.
 
HP Pavilion dv7 1130el, Windows 7 ultimate, runned fine for a year with this OS.