On Sep 25, 2006, at 12:53 AM, pentalab wrote:
--- In ham_amplifiers@..., "Peter Voelpel" <df3kv@...>
wrote:
Hi Jim,
I understand that tube life is dependend on their vacuum and on
the emission
from the cathode such that material of it disappears until worn,
and then
the tube is probably send in for a new coating.
How does ?the clock tick? when just the heater is lit and no
current flows?
73, Peter
### anode/grid current/drive power has nothing to do with
emmision. Take 2 x identical linear's..... one with just the
fil /blower on.[no HV no drive applied] ..and the 2nd linear
with HV on and drive applied [dead cxr]. The tube in each
amp will lose emmision at the SAME rate.
### after XXX hours.... the tube in each amp will need to be
sent in for a rebuild.
### Hence.... 'when the fil is lit, the clock is ticking'
Amen, Jim, and when thoriated-tungsten fil-V is increased, the tock
ticks faster as a function of dV^23.4, so for every 3% increase in
filament V, useful emissive life is whacked 50%.
Jim VE7RF
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