[R-390] TUBES

[mikea]

On Thu, Feb 14, 2002 at 04:58:28PM -0600, Bill Hawkins wrote:
> Other tries at this thread revealed that the home tinkerer
> might be able to build (or rebuild) an 01-A class tube with
> a "soft" vacuum. IF he or she could get coated filament wire.
> 
> The tubes that we want are all hard vacuum tubes. It takes
> an expensive set of vacuum pumps to get down to where flashing
> the getter takes out all of the molecules left.

I seem to recall some article(s) in Scientific American about
DIY pumps for getting a good, hard vacuum. I worked with a bunch
of hi-vac stuff, and can attest that the commercial gear is
expensive to buy, operate, maintain, and debug. 

> Making the elements for a 7 pin miniature pentode seems to be
> impossible without expensive tooling - kinda like making a
> turbo-pump for a Saturn V engine. Both materials and tools
> will be prohibitive for short production runs.

There I agree wholeheartedly. Material composition would
have to be _very_ rigidly controlled. 
 
> And then there are the glass seals for the pins ...

_That_ I don't see as a great problem, given that we have a way
to produce and align the elements, put them in the envelope, 
pump the critter down, seal it, fire up the getter, etc. Metal-
glass seals are (relatively) simple in lab glasswork. Not by
any means trivial, but vertainly no more difficult than a 10-
step graded seal from quartz to Pyrex.

And it appears that the bases were mass-produced. One-offs, once
the process is refined to repeatability, shouldn't be terribly
hard. 

For those who want to respond, "When pigs fly", I have a very 
nice flying pig hanging from the ceiling of my office by a 
tether. It has nice fabbric wings, a small DC motor, and flaps
in a circle on 2 AA batteries. I will accept "When Satan sells
ski-lift-and-slope tickets. ifor Hell".

And I'm not saying that _any_ of it will be _easy_. Far from it.

-- 
Mike Andrews
mikea@mikea.ath.cx
Tired old sysadmin since 1964