iPhone 5 wont turn on no power at all.

Hi I've got an iPhone 5 that won't turn on at all. I have tried holding the home button and plugging USB into PC. The PC doesn't register any device being plugged in at all. I've tried out the battery in another phone and it's fine. It needed a new screen when I got it so replaced that. Tried the screen on another phone and it works perfect. I've changed the charger port on the phone, still no luck. I'm just wondering if there could be anymore hardware problems stopping it from turning on?