Why is my power adapter fuse blowing?

Hi

I have a PowerBook G4 15" 1.67Ghz model A1138. The power adapter keeps blowing it's fuse every time I plug it in. When I plug it in to the computer, there are no lights on the charger ring, probably because the fuse has blown again. I replaced the plug fuse and removed the DC board connector from the logic board inside the computer, and the charger ring glows orange. I tested the voltage and it reads 24.7 volts. When I plugged the DC board connector back into the logic board, the fuse blew again.

I suspect there is a short circuit in the logic board, can anyone confirm that this might be the case? If it is, would I need to replace the entire logic board or is there any way of finding and fixing the short circuit?

Thanks :o)