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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

Showing 2 responses by lacee

lacee
811 posts
 
I have Acoustat tube servo amps with lethal voltages,made in the 1970's but modiffied.
There are 4 tubes in each amp,sourced from television technology because of the demands made on such a circuit.The amps also are the source of power to charge the electrostatic panels and keep them charged, they are not just "power amps",but made specifically for the Acoustat X series.They are not a conventional amplifier design.

The amps are always "on",but in a sleep mode until I flip the toggle switches for listening, and then off when I'm done.So there's a lot of juice flowing thru those fuses.

I've been using upgraded fuses(HiFi Supremes-4) in them for two years and never had one blow on me , except when it was an error on my part.

That the upgraded fuses are blowing and the stock fuses are not would indicate to me that the stock fuses are more forgiving and the upgraded fuses are only doing what they are supposed to do-self destruct before something awful happens.
I would stick with the stock fuses and the new tubes and cross my fingers, or go back to the stock tubes and the upgraded fuses.

I am curious.
What made the most enjoyable improvement, the upgraded fuses or the upgraded tubes?
The answer to that should settle it.
lacee
811 posts
 
Good news and good luck with the cake.
It's always great when things go the way you think they should.
We should now be able to forget about HiFi fuses being inferior to stock fuse at least for protection.
The next hurdle to jump is to somehow proving they sound better than stock fuses, but just for those who refuse to try them and let their ears decide.
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