iBook g4 1.33ghz fan blowing when turned off and wont boot

Hi!

My iBook has stopped charging. I thought it to be the little dc power board thing in the laptop, so I replaced it. After re-assembling the computer, putting in the battery caused the fan to start spinning fast, with the computer off and the battery nearly dead. And the computer will not turn on, even with the power cord connected. I have since replaced the old dc board, with no effect.

Has the logic board gone now?

Thanks!