>Maybe amps with radiation cooled glass tubes and modest air flow
requirements
>have advantages if you live at high altitude, although it's not something
that
>I've ever had to consider.
I keep hoping that someone will resurrect the vapor-phase method of cooling
and incorporate it into commercial amplifier. Despite perceptions, the
method is nearly maintenance-free and provided that all plumbing connections
are secure, there's little danger of leakage. I presently use an original
ALPHA SEVENTY that will one day require a new tube. However, its 3CV1500A7
is scarcer than a Deforest spherical audion and I cannot find anyone with
the necessary spirit, skill-set and tools to retrofit a boiler "dud" onto a
new 3CX1000A7. Perhaps George Daughters will have some input. By the way
George, nice article of yours in the March, 1966 issue of QST on "The Field
Day Gallon."
Vapor-phase cooling offers approximately ten times the plate dissipation
efficency as that provided by forced-air cooling: power dissipation of
approximately 500-watts per square centimeter of internal anode area easily
achieved. Compare this with 50-watts per square centimeter using forced-air
cooling and 100-watts provided by pure water cooling. I recently ran across
an Eimac ad in that same year which featured the original "Stanley Steamer"
by Jack Quinn, W6MJG. However, the ad introduced a tetrode version that I
do not believe ever went into production. Its designation was the 4CV1500B.
Unlike the ALPHA SEVENTY, Jack's amplifier uses a horizontally-mounted
condenser located atop the amplifier, negating the requirement of a small
whisper fan but it also required a seperate water reservoir. ETO's version
incorporated the reservoir into the bottom of a vertically-mounted
condenser, much like an automobile radiator. All heat generated from plate
dissipation is transfered by steam into the condenser where it converts back
into cooled water and recirculates. Both amplifers run absolutely silent,
little heat builds-up within the cabinet, and altitude is not factor. A
much better description of the overall cooling process is decribed by Jack
in the May, 1966 issue of QST.
-Paul, W9AC
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