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Wouldn't 100 or 120 times a second be more readily available?
73 de Bob - KØRC in MN
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Message: 11
Date: Wed, 13 Feb 2008 14:42:29 +0100
From: "Patrick Egloff" <pegloff@gmail.com>
Subject: Re: [Amps] filament supply D.C or A.C
To: k7fm <k7fm@teleport.com>
Cc: amps@contesting.com
Message-ID:
<41a415460802130542u7c065401h36f1c45ee536b02a@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
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Some say that if you run the tube on dc, you should alternate the polarity
of the filament every so often, to offset the migration problem.
--------------------------
About 60 times a second would be great !! ;-))
2008/2/13, k7fm <k7fm@teleport.com>:
>
> I remember reading the same test about the ac on filaments. I recall the
> test was run because the lamp manufacturer specified a long life bulb and
> an
> aircraft manufacturer installed them and found substantially less life in
> the aircraft than specified. The lamp manufacturer ran the test, and
> changed the long life specifications to ac.
>
> There are some examples of dc on filaments, however. Almost all of the WW
> II aircraft radio equipment ran on dc - and many are still running (often
> on
> ac, however). However, the war was relatively short while
> amateurs expect
> their tubes to last 30 or 40 years. Radios from the 20s all ran on
> batteries, and many of those tubes are still running.
>
> Some say that if you run the tube on dc, you should alternate the polarity
> of the filament every so often, to offset the migration problem.
>
> There are other things that may apply to the equation, however. DC is
> easier to regulate, and may be easier to ramp up for a controlled start.
> Also, the more you otherwise abuse the tube, the less important the
> filament
> is. For example, if you overdrive it, under-cool it or overload it, the
> filament source becomes less important - because the tube is less likely
> to
> fail because of filament failure and more likely to fail for other causes.
>
> 73, Colin K7FM
>
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