fuse for Musicmaster Bass Amp?

[Groover]

I'd like to add a AC fuse & holder to my Musicmaster Bass Amp. How can I determine the appropriate value fuse to use?

[Groover]

bump

What are the calculations I need to do to determine the appropriate value for an AC fuse for this amp which does not originally have one?

[olddawg]

bump

What are the calculations I need to do to determine the appropriate value for an AC fuse for this amp which does not originally have one?

There should be something written near the AC cord that list the power consumption of the amp in watts. Divide that by the line voltage and increase that by 20%. Round that off to the nearest 1/2 amp. Keep in mind that line fuses are not there to protect the amp but to keep you from burning down the building.

[Groover]

wha' I need 2 protect the amp?

[olddawg]

wha' I need 2 protect the amp?

You can't run faster than an electron.

[Groover]

I did think that the mains fuse provided some protection to the amp.

Perhaps you would suggest a fuse in the B+ line?

[Enzo]

Fuses protect everything around the amp. They are there to help prevent fires.

[Steve Conner]

I remember once I was messing around with one of my home-built amps on the workbench, and I accidentally dropped a screwdriver into the guts while it was on. There was a big flash and bang, and both fuses blew, the AC line and HT. The HT fuse was even cracked and blackened.

My house didn't catch fire, and after replacing the fuses, the amp was good to go again.

Fuses can't protect an amp against all possible faults (you can easily burn out a heater or bias winding on a transformer, or melt down your tubes, without blowing the line fuse) but they're better than no fuses.

For a little amp like the Musicmaster, running off 120V, I'd guess an 0.5 amp fuse for the AC line, and a 0.25 amp for the B+.