Hey, so just to add my two cents, I had the exact same problem as all of you. I don't know exactly what I did to fix it, but it seemed dead, hooked it up to the old display and i got backlight and sound, then i attached it to the new one and i got backlight and sound. Tried doing home + power button and nothing, went back and hooked up the old display, this time the lcd worked and displayed the apple logo (probably from me holding power+home), I switched it to the new display and it booted up normally and made me reauthorize the phone. Maybe i tricked it into displaying on the new lcd?