I’m laughing because there is no warranty on my amps or preamp. They are Grover Huffman custom designs of which there are four or five made. Obviously, the amps are operating just fine with the higher rated SR fuses and Elliott of SR suggested that I use them because of the huge draw on turnon due to the huge capacitors..
If you read previous posts, they indicated by someone who appears knowledgeable that there exists a range of up to 400% in melting points which may or may not be the same thing as amperage. SR states that their fuses are different than standard fuses and should be chosen accordingly based on the equipment needs, not just as the manufacturer stated.
I am quoting the prior posts below for your edification:
Jon, sorry that you’ve experienced this issue. I have no particular suggestions beyond what Sgordon1 has said (although you indicated that you’ve already performed step 1 of his suggestions), but the following may have some relevance:
I took a look at the detailed technical info for the 0.25A 250V 5x20mm fast blow fuses manufactured by Littelfuse, one of the leading makers of non-audiophile fuses. Interestingly, they offer at least four different series of fuses of that specific type, designed to various combinations of UL, IEC, and other standards, which have "nominal melting points" (defining the combination of current and time that will cause the fuse to blow) ranging from 0.0166 amps squared-seconds to 0.042 amps squared-seconds. That’s a difference of a factor of 2.5, even though all of those fuses are from a single manufacturer and all are 5x20mm fast blow fuses rated at 0.25A 250V.
If the stock 0.25A 250V 5x20mm fast blow fuses in your amp are rated at or near the upper end of that 0.0166 to 0.042 range, and the unspecified rating of the SR fuse is at or near (or even below) the lower end of that range, it would certainly seem to account for what happened. If you call SR, you might ask them if they can tell you what the nominal melting point of that fuse is, in amps squared-seconds.
and this one:
Gpgr4blu, I’m sure Tsushima1 is correct about the physical size and voltage rating of the fuses that are required for your ARC gear, but to clarify about the voltage ratings: The 500v and 250v ratings refer to how much voltage a fuse can withstand when it blows. The voltage a fuse will "see" when it blows (i.e., the voltage that will appear between the fuse’s two contacts) will be the full line voltage. So the higher that rating is the better, everything else being equal. Under normal operating conditions the voltage appearing across fuses having these kinds of ratings will be a very miniscule fraction of a volt. And when the component is turned off the voltage appearing across the fuse will be zero.
HOWEVER, I would disagree with a couple of important things that have been said just above:
1)I would strongly recommend against substituting a fast blow fuse of somewhat higher current rating for a slow blow fuse of somewhat lower current rating. Some time ago, in connection with this thread, I looked at the detailed "melting point" specifications that are provided by the major manufacturers of garden variety fuses. That spec defines the approximate combination of current and time that will cause the fuse to blow (actually, in terms of current squared x time, which is proportional to energy). The upshot is that such a substitution stands an excellent chance of causing the fuse to blow almost immediately. Especially in the case of a mains fuse, where brief but very large "inrush currents" may occur at turn-on.
2)Earlier in the thread there were multiple anecdotal indications that the unspecified melting points of SR fuses are probably a bit lower than those of garden variety fuses having the same current rating (i.e., indications that the SRs blow a bit more readily). And it would seem expectable that in general a fault in a component that would cause a fuse to blow is more likely than not to result in a very large current increase, rather than one that is just slightly greater than the rating of the original fuse. Especially in the case of a mains fuse. So for both of those reasons I would suggest using a 6.3A slow blow in a 6A slow blow application, and an 8A slow blow in a 7A slow blow application. And likewise if an SR fast blow is substituted for a stock fast blow.
