Rock-Ola 477 - Fuse Blows every time its switched on

My brother-in-law has a Rock-Ola 477 which has a fault. He asked me to find some answers for him.
He has a Rock-Ola 477 with a 9.6V Power Supply and when he turns it on it blows the fuse every time.
Fuse 101 on the Rectifier Board is what blows - part number 52355-A.
Can anyone help to identify what part of the system this fuse covers, as the manual is not clear.
Thanks (and I hope I got his message explained correctly).
Claire

Hi Claire,

Is this fuse also blowing with the 12 pins plug in front of the power supply unplugged? In other words; is the short circuit in the power distribution or in de boards?
Kind regards Piet

Thanks Piet... I've sent an email to my brother-in-law with your question, and I'll get back to you with the answer.
Claire