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Re: [Amps] re: baking out tubes

To: amps@contesting.com
Subject: Re: [Amps] re: baking out tubes
From: Traian <yo9fzs@office.deck.ro>
Date: Mon, 25 Oct 2004 13:44:31 +0200
List-post: <mailto:amps@contesting.com>
Hi Bill,

May a rather expensive power tube to not have an internal gettering sytem?
The getter is used even for the cheapest small signal and low power glass
tubes, so why to not be provided for a $500 (or maybe $5000) power
transmitting tube?!(Unless, it include a vacion device, of course).

Details about vacuum tube conditioning can be found in the Eimac's
AB21 Application Bulletin and in the newer edition of Care and Feeding...

I have made experiments for some tube conditioning and I have already
posted some results and personal observations, see:

http://lists.contesting.com/archives/html/Amps/2004-05/msg00030.html

>From then now, I have also verified six 8122's and other two GU43B
tetrodes with the same positive results. The breakdown voltages are
increasing by "debarnacling" for the NOS tubes but it seems that is not
for the heavy used ones? (at least not for a used 4S040 and 4CX1000 I
have tried).

73,
Traian



Bill Fuqua wrote:

>      If the tube has no getter baking out requires a high vacuum system.
> The gas has to go somewhere after being driven off the internal surfaces of
> the tube.
>     There is another process called conditioning where the tube operated at
> normal filament voltage and the plate current is kept low. The plate
> voltage is raised ( current limiting requried) to the point  where a spark
> is produced. This spark evaporates the sharp the small sharp irregularity
> that that was the cause for the low break down voltage. The process is
> repeated until the desired plate voltage is reached. This is how they make
> some not pulse rated tubes into pulse rated tubes.
>
> 73
> Bill wa4lav
>
> At 01:39 PM 10/24/2004 -0400, carl seyersdahl wrote:
> >   After reading about this subject I"m wondering about the requirements to
> >"bake out" a tube. !! do you run it with full filament voltage or percentage
> >lower? how about plate voltage?? screen? do you let it run any plate
> >(anode)current ??  How do you know when it's safe to use at normal voltages
> >?  Another inquiring mind.!!!
> >    carl / kz5ca
> >
> >
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