Chosen Solution
I recently replaced a cracked screen in a friends Galaxy S4. When I first put the phone back together I thought the new screen was faulty as the phone would turn on but the display wouldn’t light up. After some fiddling around I tried turning on the phone while I had the mid frame removed and to my surprise the screen worked just fine. Upon re-installing the mid frame the screen stopped working again. I removed the mid frame once more, turned the phone on and then began to snap the display assembly back into the mid frame. Everything was fine until I snapped the display assembly and the mid frame together around the top left corner near the volume button at which point the screen cut out. Does anybody know of a way that the screen could be shorting out? Or could it perhaps be pressure on the digitizer flex cable? Any assistance would be greatly appreciated.
I faced the exact same problems with my new brand new s4 module from a official Samsung dealer. I could secure the whole frame, but once i secured the right top part of the midframe (looking from behind) it would short out and not even boot the whole phone anymore. The phone was a i9506 and the module a i9505. I am not sure if this has anything to do with it, but i do know what caused it. When i taped off the black screw securing the motherboard right under the part of the frame that shorts the display the whole problem went away. I tried it without the black screw and it also does not short out. I believe the black screw helps alot with positioning accuracy from your GPS, so if it is not a solution to leave out the black screw for good, u will have to kapton tape it. To make it a little bit more clear, i am talking about this black screw:
Good luck! :)
Not sure if this will help. But I had same problem and I then relized I had ordered frames for verizon/Sprint and there just enough difference between them and T-Mobile/AT&T to make it not sit right and it actually power switch causing problem.
