Powerbook and firewire

[Fra]

Hi guys i'm new here and sorry for my english (i'm italian)!
I've a problem!
i installed yellowdog3 on my Powerbook 667 (the first one with 16MB
video)and everything work fine but firewire is completely off!
when i start my powerbook if i have a firewire hd the disk start to take
energy from computer but after few time the computer "switch off" the
firefire port and no way to bring it back!
any ideas?
i used mac and windows till now but it's my first time on linux so i
neeed a loooooooooot of help
Thanks
Fra