Why does it not turn on?

dismantle the phone and take out the logic board of dead phone then put inside the working phone and that one put inside this phone. means just interchange the logic board to check the faulty parts. it the working logic board still not working in this dead phone then may be its a charging jack or battery. check this out. otherwise its just a logic board. remove the shields to check any damage to the logic board.

put the dead phones logic board inside working phone. if logic board heats up from the upside left side then it a PM ic got shorted just change the logic board then . if not then tell us what is happening after changing . thnx