Which are the defective pieces of my iPods?

Hi everyone,

I have 2 Ipods which doesn't work anymore.

I tried almost everything I've seen on internet and I'm almost convinced that problems come from defective pieces. I'd like to know which are them so I can make an ipod from both.

Can someone tell me from which parts come from the problems if I describe in details their symptoms?

Cheers for your answer.

(and sorry for my english, it's not perfect..)