Hi there,
If your phone is Warming up but does not Power on or Charge, this could Indicate that specific Circuits are fried.
Another indication is that the Screen could also be dead and may need replacing. You could have a look under a Strong Magnifying Glass or a Microscope and see if any of the Capacitors, Resistors or Mosfets are burned on the circuit boards.
Take a look at the Power Port closely and try to Test it with a Tester to see if the Power from the Charger is reaching the Board . Make sure the Charger is outputing correct voltage and amps. Usually 5v @ 1amp ot 2 amps anything more or less could cause problems.
If the problem is too intricate to test, you can take it to you local Fix it shop... Hope this helps !
thank you,
Neo43