Thank you all for the replies. I don't know a lot about electronics, but I'm assuming that the mains goes through a transformer, so I'm wondering if it matters if the fuse blows.
The amp is 25 years old, and since it is a tube amp, the voltage to run the power tubes is 400 (440?) volts, and to reduce hum all guitars have the ground from the amp wired to the bridge of the guitar. (so that by playing, the amp is grounded through the hands.)
If the amp shorts out to ground and the ground goes hot, I will get quite a shock! (will it kill me? will 400 volts stop my heart? yikes!)
Fortunately I have found a circuit that can be wired between the ground and the guitar bridge, that will still allow for grounding, but will reduce the amps so that I will feel a small electric shock so that I will stop playing. ( for anyone who wants to know, wire a 220 k ohm resistor and a .001uf (1000pf) capacitor, both rated for a minimum of 500 volts, in between the bridge and the circuitry. wire them in parallel, not in series! solder them together and insulate the leads).
I'm wondering if I can test the amp by removing the fuse, and testing the resistance between the a/c lugs and inside the fuse opening. by putting the test lead just inside I should get a reading close to ) ohms. (I think).