Why is my screen black after screen replacement?

iPad was dropped and there were lines across the screen, no cracks though. I had it repaired and it was working fine after that. The battery started draining fast and the screen became black. I thought it was the battery, like it had died or something. Until one day, I was playing around with it, charging it and pressing the home and power button simultaneously. I heard what sounded like the iPad taking a screen shot. Any thoughts? Tips? I would really like to use the iPad again.