IPhone 4 doesn't turn on, charge, or anything?

So recently my friend came to me so I can fix his iPhone 4. It doesn't turn on at all and it doesn't even show the red battery thing saying it needs to be charged. I tried plugging it in for at least an hour and nothing happened. ITunes can't recognize it either. So I'm asking for full detailed instruction on how to fix this thing. I don't care if i have to take the thing apart but I'm trying to avoid buying anything. I've looked everywhere and the forums didn't help at all because they just say "buy another one." It's out of warranty so don't tell me to just give it to Apple. I want to break this phone apart and fix it myself, but I need to know what exactly I'm doing so I can fix it.

It's broken

Take it to genius

Have you tried holding down the home and sleep buttons together for 15 seconds, with and without power connected?

Thats all I can suggest…