Fuses only blow like that when a semiconductor device is acting like a piece of wire causing an overload. An ohmmeter on the ohms setting will show any transistor with this condition as a short, just like you had touched the test leads together! Follow where the fuse leads to. And look out for signs of damage too. The most obvious parts to go are the ones that do the work, in the power supply or the main amp device, often an IC.