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Re: [Amps] SB-220 update and gettering

To: J Lyles <>
Subject: Re: [Amps] SB-220 update and gettering
From: Rob Atkinson <>
Date: Sat, 26 Nov 2016 13:57:09 -0600
List-post: <">>
You're sending me a long paper from 1935 30 years before the 3-500Z,
which is the tube I am discussing, although I may have incorrectly
described it as an internal anode graphite tube.  I don't have time to
wade through a 4 or 5 page Ph.D. paper--I have a job and a lot of
other work to do.  If you want to ignore decades of advice and
experience with these tubes from every other authority out there and
run them with them never showing any color go ahead.  I've seen I
don't know how many broadcast rigs and linear/non-linear RF amplifiers
with one or another member of the 3/4/5-125/250/400/500/1000 showing
color as a normal part of their operation.  Sorry, I'll stick with
what design engineers seem to know, with chimneys and a lot of air.



On Sat, Nov 26, 2016 at 11:58 AM, John Lyles <> wrote:
> Rob
> I emailed you a very authoritative paper from RCA in AIEE in 1935, although
> very old, the designs have not changed much. The technology hasn't changed
> much since then. Most modern Tantalum or Moly plates do run with a lot of
> color in their typical full power state, but no so true with graphite. It is
> mechanically very stable comparatively, although it requires a lot of vacuum
> processing before it is very useful.
> Some of the anode materials do function as a getter to desorb other stray
> ions when heated. Graphite is not one of them, although it certainly does
> outgass residual molecules if it is running hotter.
> 73
> John L.
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