Ian,
>There are two ways gas can get into a vacuum tube. One is through a faulty
>seal, as Rich said. But even if a tube has perfect seals, the inside surfaces
>of the tube can very slowly release gas.
Ok, that makes sense. I suppose an inverted way of looking at it
is that if the tube -didn't- emit any gas internally, there would
be no need for a getter.
One of the reasons I asked was based on experience. After pulling
a new 3CX400 from storage, (probably 5 years or so) it immediately
glitched when B+ was applied. After disengaging from the ceiling
and checking everything, I hit the power again and got another
glitch. The third time it didn't, and hasn't in at least a
hundred power cycles since then. (the amp is used at least every
3rd day or so)
So.. Now I'm wondering if there would be any advantage at all
in changing my (8877) controller sequencing so that the B+ supply
didn't engage until after the 3-minute warmup timer expired?
I would guess 3 minutes isn't long enough to matter, but it's
worth asking.
>An archive search for "ion gauge" should find this, but AFAIK
>nobody has investigated it further. It would be a great project
>for someone with a bucket of new and used tubes!
W-e-l-l, I'm not sure I'd be comfortable tinkering with my
8877's in that manner, or qualified to interpret the results.
(Maybe 3-500's, or something a little less spendy than 8877's!)
Interesting idea, though. I'm sure I'm not the only one that
collects tubes over time, and has them sitting about for extended
periods.
Thanks,
Jim, N7CXI
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