Buzzing suggests that something may be shorting. Start by checking all the ribbon cables are properly seated and connected.
The battery connects to the logic board on the bottom right side of the device but the camera module is located at the top.
I think you have a current running through the frame and its setting off the digitiser or a current is running through the digitiser and into the frame. Disconnect the screen and connect the battery. If there's no buzzing and it won't auto power on, connect the screen. Same thing, no buzzing, no power on, connect the digitiser. This might allow you to isolate it to the frame, the screen, or the digitiser.