Onan gen set problem

I had my 7.5 onan diesel loaded right down. Both airs, microwave,100amp charger,Etc. AC power quit. Found blown 15A glass fuse on gen set. Replaced and still blows without load. Any suggestions?
Onan gen set problem

I talked to my generator expert (not being one myself) and he said, "Time to take that one to the shop." According to him there could be 7 or 8 different things wrong with it depending on when the fuse is actually blowing, during cranking, after start up, etc.