which components on main logic board fails the most

hi

i have some dead logic boards for ipod video 5th gen 30gb 820-1975-A and 820-1763-A

just wondering if anybody ever manually tested the components on these logic board and found which smd parts have caused there boards to fail... no sign of life ..dead.

was it a fuse or a resistor or those km coils any pointers for me to start with would be great ?

as i sooner repair them than buy new boards.

also while we on this subject which components on hard drive logic boards are prone to fail to cause the clicking noise

please dont say replace them as i'm trying to repair the ones i already have.and it be a learning curve too.

thanks david