iPhone 3g 3.1.2 jb.
I was having trouble with my speakers so I took apart the phone to see if I could fix it. At the end of it all I couldn't really find what was going on. So I just assembled it but to my surprise the screen just wouldn't turn on. The vibrate button works and I get calls and text but the screen doesn't turn on. I've taken the phone apart countless times even changing the headphone jack (Which was hard but worked) so I've always been careful to not rip anything. I took it apart again and all the connections are, well connected. Anyone have any idea what's up?

I've also tried to restart it but it doesn't seem to make a difference.

Any help would be appreciated.