Blowing Fuses. Dennis Had Inspire 300B SET

@moose89 Does the amp blow its fuse if the power tubes are not installed but the rectifier is?

I’ll just say that your thought that the fuse is always properly sized to prevent a "poorly engineered power transformer" from blowing is an example of what I meant by overly optomistic. You think they screwed up the power transformer but properly sized the fuse?

@carlsbad2 No, this isn’t what I think nor did I suggest that.

What I did say is that somehow this and other amps like it seem to work with a 2A fuse. That suggests that since this one did at one time, it should be able to do it again. But I don’t know what its like (although the photo looks OK) and since I don’t want to be on hook for a part that might be underrated or the like, I won’t put in a fuse that is beyond the suggested rating. That isn’t the same thing as saying there are parts that are underrated or poorly engineered.

You’re right that we’re conservative about our fuse ratings. They have served us well in the last 45 years. When a fuse blows in our stuff there’s always a good reason.

@carlsbad2 I probably do see this from a different perspective. I’ve worked on so many different pieces over the years and I’ve seen attempts to install higher rated fuses. About 1/2 the time it ended in tears.

If you put a 3A fuse were a 2A fuse was indicated, there will be 50% more current allowed. If all that current is feeding a short in a rectifier, you may not have enough time to shut things down before that power transformer gets fried. Some transformers are not nearly as durable as some others!

Now you might argue that a transformer so easily damaged is substandard or the like and I won’t disagree. All I’m saying is apparently this amp has been made for a while so there are multiple examples out there that seem to run fine on a 2Amp fuse, just like this one did until whatever came along and knocked it out.

So, as a thinking man, the idea of putting in a higher rated fuse rings false to me. Actually, it rings scary. I’ve seen poorly engineered power transformers catch fire; its not pretty and they were able to do that with a properly rated fuse. I don’t know how well engineered this power transformer is, but why go where angels fear to tread?

@carlsbad2 I'm not certain how you arrived at this:

Your opinion is noted and considered overly optiomistic at best.  You are a manufacturer and have an overly proud opinion of manufacturers IMHO. 

My prior comment is based on experience. I started my career in 1974 servicing consumer electronics and that is how I put myself through engineering school.

You don't put a fuse of a higher rating in any kind of equipment, especially if that equipment is consistently blowing fuses.

Bad Things tend to happen.

I have no idea how you might have arrived at the 'overly proud opinion' thing. To me the comment makes no sense, so I suspect its not accurate 😉

I would try a 3A slo blow

@moose89 Please ignore the above advise- never, ever put a fuse higher than the rated fuse in any product unless specifically told by the manufacturer that its OK.

Solid state amps usually have fast blow fuses. Tube amps almost always have slow blow fuses. All the 'zigzag' fuses I've seen are fast blow. I would get a Littlefuse or Bussman slow blow fuse as a replacement so as to know that the fuse you're installing will actually do the job.

If it continues to blow you have other problems; the amp should be checked out by a qualified technician.