No image after screen replacement

Hi every one,

I could read in previous messages that you must swich off your phone before changing the screen. When I changed my screen, I tought my phone was switch off but it wasn't. Now when I plug the old or the new screen, it doesn't display anything but I can feel that the phone is still swich on. What piece of the phone did I broke up and what can I do ?

thanks for your help!