Will Matney wrote:
>Even though a vacuum is pulled, when an element gets hot it can release
>a small amount of gas, even though they say the material has been
>de-gassed. Plus with age, a small amount of atmosphere can seep in,
>especially on glass tubes and where the ceramic to steel meets on a
>steel tube.
We should be careful to think of these as two totally different kinds of
"gassy tube" problems.
The releases of gas from structural materials are big enough to cause an
arc when they happen, but are often small enough to be removed by the
chemical gettering action (which is built into most transmitting tubes
even if you don't know it).
On the other hand, a leak from the atmosphere is only going to continue,
and will eventually use up all the gettering capacity.
So the first kind of "gassy tube" problem will often be recoverable, but
the other kind won't.
--
73 from Ian G/GM3SEK
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