[TenTec] Centurion

[Gary Hoffman]

Well !!  We certainly generated a very useful discussion on this topic !
Reading all the technical posts, and the links people provided, I certainly
learned a lot.  I now understand that the getter is of continued value
throughout the life of the tube, and that if a temporarily disused tube is
placed back in service, there are very specific things I can do to allow the
getter to do its job.  This information appears correct, and contradicts the
(incorrect) information that I previously had been taught, that the getter
is fired once at the factory and is of no use thereafter.

I went back to the original source I had, who taught me this when I was 10
years old.  (My Father, a retired electrical engineer).  He corrected
me....he told me that I was remembering when I asked him about the slight
colored coating visible on the inside of the glass of certain types of glass
tubes.  He said that this resulted from the firing of an element inside the
tube when it was new.  This results in the deposition of a layer on the
glass...which thereafter acts as the getter !  I see one of the references
here says essentially the same thing....that some tubes have a coating on
the glass which acts as a getter.

So, ever since I was 10, I have misunderstood what he meant all the way back
then, and got it wrong as "firing the getter" rather than "producing the
getter" inside the tube.

This may explain 3-500Z tube failures I have had.  I have never cooked them
to clean out the tube.  Also I see that they require more than just filament
heat to activate the getter.  Resistors in the plate lead are called for on
a temporary basis to allow this to happen without wrecking the tube.  I've
never done any of that.

Since I'm 53 now, I've gone 43 years with a wrong definition of the getter !
Must be some kind of a record.

73 de Gary, AA2IZ


----- Original Message ----- 
From: <CATFISHTWO at aol.com>
To: <tentec at contesting.com>
Sent: Saturday, December 10, 2005 10:19 PM
Subject: Re: [TenTec] Centurion


>
> I am not a Tube expert by any means but  This  is supposed  to be true, I
run
> all my metal tubes for an hour or so each months, and I  suppose this also
> keeps everything else good too.  ( cap etc.) .  I am  not sure of the
source of
> this info, ( a mind is a terrible thing to loose!!)  but I believe it is
> correct, and some components of the tube  off gas a few  molecules of O2
and such.
> and the vacuum can never be perfect.  I wonder if  any one else is
familiar
> with this..
>
> tom N6AJR
>
>
>
> In a message dated 12/10/2005 7:06:24 P.M. Pacific Standard Time,
> ghoffman at spacetech.com writes:
>
> I have  two observations about all this, or perhaps I should call  them
> questions.
>
> First of all, I thought a tube was supposed to be  pumped down to a very
good
> vacuum and then completely sealed.  Thus  there should not be gas leaking
in.
> It should not accumulate over  time.  If it does, its gone bad.  Is this
not
> so  ?
>
> Secondly, I thought the getter was used once, when it was "fired" at  the
> factory.  I did not believe that it was at all functional beyond  that
single
> use.  Is this not so ?
>
> I've never read before about  turning on an amp for a long time after a
> period of disuse, to "clean up  gas" in the tubes.  Has anyone else
(besides
> the original poster here)  ?  I have heard of course about reforming the
> electrolytics after a  period of disuse.  Could we inadvertently be
confusing
> these two  different concepts ?
>
> 73 de Gary, AA2IZ
>
>
>
>
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