Tube blows Amplifier fuse....causes?


I had a interesting experience. I was shipped a pair of 300B tubes(warranty). I put them in my Vac 140 monoblock. Everything was fine the first day and then I got a low transformer hum 2nd day. On the 3rd day after turn on the slo blow fuse blew(inspection showed low voltage). I was able to find the offending tube and replaced it. With the replacement everything is normal.

I sent the tube back to the manufacturer's agent and they say it tests fine. They will replace it though.

Is the bad tube pulling to much current? I have never had a tube cause a fuse to blow or produce a transformer hum(lucky). Can somebody tell me what's happening, My guess would be the filament is drawing too much current.
wavetrader
I had an experienced with SED 6550 winged C from TUBEDEPOT for my VTL MB250. about 3-4 tubes are bad and blow my B-fuse and a few there is no reading. they refund me back but it cost me unnecessary postage back to them.
Just a bad tube. I had a similar situation with my Auricle Musicbloc MB 70s. A KT-88 was starting to go bad. Made popping noises occasionally to start, then hum. I imagine if I let it go longer the fuse would have blown.

In my case I went straight to VAC for the replacements.
"Did they test it on a tester or in a real circut that may push it to the limit? Testers rarely test at different maximum loads."

Inquiring minds would like to know. I'm not one to crap in my oatmeal,but I question the sales people(company) for this tube manufacturer.
I sent the tube back to the manufacturer's agent and they say it tests fine. They will replace it though.
Did they test it on a tester or in a real circut that may push it to the limit? Testers rarely test at different maximum loads.
Is the bad tube pulling to much current? I have never had a tube cause a fuse to blow or produce a transformer hum(lucky). Can somebody tell me what's happening, My guess would be the filament is drawing too much current.
I would guess the tube not the filament. When filaments draw too much current they normally burn out causing a dead tube.