[TenTec] Centurion

[Ken Brown]

Hi Gary,

There are varying degrees of vacuum. I don't have my Vacuum Technology 
books here in the shack, so I won't go into details about where the line 
is drawn between "High Vacuum" and "Super High Vacuum" and what level of 
vacuum is needed in power tubes, because my memory on the details is not 
that good and I'm sure I'd get it wrong. In any case I do know there is 
no such thing as a perfect barrier or seal to gas molecules. Much as a 
latex balloon loses it's pressure, metals and glass both allow gas to 
leak through at a slow, yet measurable rate when measured over long 
periods of time.

I'm sure there is someone else on this reflector who can tell you more 
about getters. I do not think that getters are "spent" the first time 
the tube is fired up in the factory, they continue to function 
throughout the tube's life in order to counteract the slow, inevitable 
leakage through the glass. I'd sure like to hear a more authoritative 
account of that. Anyone know?

DE N6KB


>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 ?
>  
>
>  
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