Miguel --
The fuse(s) blow probably because either filter cap has shorted, or there's some other deadly load on the power supply like a shorted power transistor. Maybe. It didn't eat your speakers?
The fuses, judging from my ongoing repair of a Coliseum Slave, are rated at 10 amps. The 250v is a maximum voltage; the power supply, if same as Slave, is running +50 and -50 volts.
Cheers!