i had the same probleme with my phone and i do this https://www.youtube.com/watch?v=Af5DvIZw... it work for screen too, it's the same cable. i even try to change the daughter board but this look like a motherboard connecteur problem.

Screen black but phone works

I haved the same probleme it's come because the connection between the mother board and the usb wire was baddly plug i have to maintain the connections and restart my phone (hold second the power button) if this solved the problem you can add a lot duct tap to make pressure between the connections and the duct tape. Bye sry for my english