Tom Rauch wrote:
>> 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.
How do these developments relate to the Heath SB-1000? Are any
modifications required to the cooling?
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
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