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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Cold Tube turn on ? posted by Terry Koehn on August 11, 2002 at 23:35:25:
Has anybody noticed that light bulbs flash and burn out usually when first turned on...?Sure, but tube filaments are meant to create heat so
as to spur the emission of electrons and light bulb
filaments are supposed to create light.
So they're not the same thing.The usual failure mode for tubes is to either short out,
get noisy or just a wear out its cathode, which quits emitting
electrons.The German guy is right about filament failure
being unusual, and the folks at Telefunken were including, I'm sure,
series string filament tubes, where that would be more common.There are slow-warmup filaments for equipment that
runs the filaments in series-string arrangement,
but that's got nothing to with extending tube life except
for keeping the first or largest filament in the string
from blowing when the set is turned on..
Run with filaments in parallel, the slow warmup is moot point.
Broadcast Equiptment stays on all the time because of that reason or stand by modes run 1/2 filiment voltage till full turn-on is needed..Much longer tube life is realized..Yeah, but those are thoriated tungsten filament tubes that draw
amps and amps of filament current (and often cost thousands
of dollars to boot), not heater-cathode 12AX7's drawing
300 milliamps!BTW, one can also extend the life of transmitting types through
judicious use of the filament voltage control, if the
transmitter has one.I read that in Radio World
a long time ago.
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Follow Ups
- Re: Cold Tube turn on ? - Uncle Ned 21:12:01 08/12/02 (0)
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