why do hi-end fuses keep blowing, while std don't?


I've had my McIntosh MC275 for several years running flawlesly. Up until last Nov I was using stock KT88 and rolled small tubes and had a Hi-Fi Tunning fuse without issues.

In Nov-13 I upgraded the KT-88 to Psvane black bottles measuring 60mA plate current. A few power-ons after I rolled the tubes, I turned on the amp to let it warm up, but returned to a blown fuse. I thought a tube might be bad so used a std fuse, but never had a problem again.

Two months ago I bought a new high-end fuse, replaced it, and soon thereafter the same happened: blown fuse. I replaced it with a std fuse again, which is still running.

So I want to upgrade the fuse, but chances are if I use the 2A fuse it will happen again. Yet I don't want to use a higher value fuse. I'm thinking the Psvanes might be drawing significantly more current than the stock KT88 and the Hi-Fi Tunning fuse might have a tighter spec, driving said fuses to fail while the std ones survive. Would you agree?

Suggestions as to how to resolve this?

thanks much!
lewinskih01
Do an experiment. I did.

For the fun of it and to see what is what..

... I swapped out the emitter resistors on a power amplifier for fuses. the theory being that if the current was too high in the one transistor, the fusing element’s resistive properties would change, or increase..like it is designed to do ---and thus enforce current sharing.  This is a goodly part of what an emitter resistor is supposed to be doing. Enforced current sharing. But, not quite the same....as how a fuse would handle it.

This change (fuses for emitter resistors) would cause the worst elements of what a fuse is - to come to the fore.

Gotta be one of the most horrible sounding amplifiers I’ve ever heard. If not the worst.

If you want to hear what a fuse does, try that.
bdp24 writes:
You’re missing my point, Mr. Kait.


If we could just pin this, maybe next to the Forum link, cut and paste, save an awful lot of time.