So, to start with, I'm cheating, because I'm actually asking this on behalf of my brother/gui****. But, you know, they're a necessary evil, and I know you guys are always helpful, so I wanted to ask for your help. He's got a Fender Super Twin Reverb. I think it was discontinued in 1983 or so. Anyway, he blew the fuse, which was not the original, but had been in there for years, and predated his ownership. The back of the amp and the schematic call for a 6 1/4A 125V fuse. What had been in it was a 6.5A. Anyway, after lots of running around in real life and on the internet, I can't seem to find that particular rating available anywhere. We've used three 6A 250V (bussmann AGC fast-action) fuses in the last two weeks, but we can't afford to get stranded at a gig, and I worry about the effects of repeatedly blowing the fuse on all the tubes. They get us up and running for a while, but we can't rely on them. Bussmann doesn't even make any 6 1/4 A fuses except in Slo-Blo. The amp doesn't SAY slo-blo on it, so should I assume it would be a dangerous mistake to use one? Could be what's intended, I don't really know how to know that. Also, those 6 1/4A slow-blo bussmanns are 250V, not 125V. Does that make a difference? Obviously, I don't know the ins and outs of the safety of different amps, and I was hoping that someone out there could help me decide on what would be a good choice to take the place of this seemingly-mythical fuse. It's also a possibility that I just haven't located the correct place to order such esoteric things on the web yet, so any guidance in that area would be helpful. I appreciate the help even though this is a guitar amp. It is quite a nice one, however, and I want to treat it properly.