replaced screen on iPad 2, now screen doesn't display anything

I have recently replaced my iPad 2 screen. It all went well (I thought) however after putting back together and turning on, nothing is displayed??? I can see that the screen is lit but very dim. When plugged into laptop I can see the iPad and it all seems to be working fine. It makes the click noise when I lock the screen also. but its just blank.

I've tried to reboot it - holding home and lock. also restored it to factory. still nothing.

Please help!

THanks