I recently bought my first tube amp a used Port City Twelve single channel 12w head and it blew the power fuse. The fuse is a 1A 250VP 313. I went up the the store and bought a slightly different fuse. 1A 250VP 312. It blew immediately. The filament in the fuse I bought is much thinner than the one that came out of it. Is the diffence between the 313 and 312 slow and fast burn? I have also read where some guys will replace the 1A with a 2 or even 5A if there power fuse goes out. How sensitive are the components when it comes to and amp spike?

You're going to want to change your fuse to exactly what the amp requires.

I'd also change your power tube or take it in to a tech, your amp blew a fuse for a reason...
Quote by DeathByDestroyr
What the hell is a G&L.

Quote by Flux'D
Gay & Lesbian I think, the box smelled funny
Greg what did you send me??
Thanks man that's what I figured. I hadnt really thought about the tubes being a problem but it makes sense cause it was left on over night a couple times after we recorded.