PSP fat problem

[Deesal]

Hello.  I was looking at my friends PSP that doesn't work.  It will just power on for about 15 seconds, then just power off.  The screen doesn't flicker and I don't hear any sound.  I tried to use my Pandora batt and stick on it, but it still does the same thing.  I put my Pandora batt and stick in mine and it comes up to the firmware loading screen.  Anyone got any ideas??  It is a fat.  I think the motherboard might have went out, but I'm not a pro like most of the people here.      Thanks for the help in advance