> AL-80B uses side-flow air cooling which appears substantial in volume
> but does not use pressurized cooling, chimney, etc. I can't complain
> about its service, it's remarkable, but I remember reading lots of
> material many years ago about how critical it was to keep the filament
> pins below a certain temperature so as not to exceed the base seal
> ratings, blah, blah...whatever. I thought that was one of the primary
> reasons for the pressurized cooling (blower, moving air from base to
> envelope, up and out) systems used by Henry, Drake, et al in their
> 3-500Z models.
When the AL80A and later models were designed, seal and
envelope temperatures were measured at full rated power. In all
cases, all seals are well below ratings.
That is contrary to some 3-500 amps, and even the original AL80
(the design was scrapped). The cooling system in the original AL80
had to be reworked with additional ventilation holes in strategic
positions and the fan changed to a TA450S from the original fan
that had a resistor in series with it.
The original AL80, like most Amp Supply amplifiers, ran the seals
far over temperature in the interest of being "quiet" even when NO
RF drive was applied.
73, Tom W8JI
W8JI@contesting.com
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