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Re: [TCML] Handmade Vacuum Tubes Video: Build A Better 811A Mousetrap?
Hi, i often said the same thing "why cant we make our own" well, we can, but
the equipment to do so would be a huge start-up nightmare......the hardest
part of the tube work is de-gassing to temperature and the metal coatings is
what makes a good tube....now i worked at a place that made RF amplfiers and
also rebuilt power tubes, and one design of their own....now big tubes water
cooled tubes to 500kw triodes....
some of those tubes required renting a trailer mounted vacuum system, rf
heating system, all kinds of heat control, glass, filiament, internal parts
temps and seal temps......spent up to 3 weeks doing that pump down and
de-gassing......event after the tube was taken apart, recoated/repaired, new
filiament, etc
done in a cleanroom.....then back filled with some exotic gas mixture..then
load testing.....we can make dies and weld the parts together, its the clean
room, chemistry, seal making, de-gassing and pump down that costs very big
money.....a particle counter to tell what level of de-gassing the tube is
at.......and after 4 weeks rebuilding the tube and have a filiament failure
or a gassing problem, start all over again..that is the expensive part....or
a failed seal, take it apart and start over......again....
this man making tubes is definately a skilled glassworker, machinist, and a
whole heap of equipment to make a tube and have it work.....also electronics
savy as well....
i would simply like to have a tube to display......surely a limited and very
collectable tube...with the movie. cul brian f.
www.genapro.com
----- Original Message -----
From: <Davetracer@xxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, September 11, 2008 9:13 PM
Subject: Re: [TCML] Handmade Vacuum Tubes Video: Build A Better 811A
Mousetrap?
> You're right, that's an absolutely astonishing video! Making your own
tubes
> ... !
>
> And it makes me wonder...
>
> ... What if we made a power triode with high power ratings for
ourselves?
> I'm actually not kidding after seeing that video.
>
> I know from direct vacuum tube experience that 811A-based Tesla Coils are
a
> great deal of fun.
>
> I'm a little concerned that the 811A's available now, especially from
> Russia, suffer from quality control, because I've seen their plates go red
far
> faster than US-built equivalents, and I've seen plates melt unexpectedly
quickly.
>
> But the French HAM radio operator in the video building his own tubes is
> obviously running off qty 20 at a time. (You see him building inner parts
20 at
> a time)
>
> If he can do that for tubes which are small and complex, and look
something
> like 12AU7's rough size (and please, I'm using the word "rough" here; I
know
> a 12AU7 is pretty complex), and he gets some use out of them in his HAM
rig
> ... well ...
>
> Why can't we make some power triodes? Let me draw an analogy here on what
> they might be like.
>
> Do some early tries the Soviet Way: Bigger And Clunkier.
>
> Like this: Heck, when you started up the older model Soviet tanks, you
> expected to gather a full kilogram of engine shavings in the engine oil
during its
> first run, because the tolerances were so sloppy. You have to change that
> oil before moving on.
>
> The 811A's were a design from the 1930's. (My old datasheet was copyright
in
> the 1930's). We don't have to match their "form factor" (their size and
> shape). They have 4 pins -- 2 for filament, 1 for grid, 1 for plate.
Filament is
> 6.3 volts @ 4 amps. We don't have to match that, either. We can make
> something far clunkier that isn't designed to have all the smooth
characteristics of
> a transmitter tube made for Class A, B, and C operations. We're not going
to
> be broadcasting voice through this.
>
> What we need is something that will accept an input at the grid around 90
> volts (100 V max) at 50 ma, max, to modulate a plate voltage of around
1200 to
> 1500 volts max, switching on and off a current of 130 ma to 160 ma max.
This
> is around a 160 Watt tube (max).
>
> [A lot of the 811A specs are specifically for two-tube systems; pretty
much
> double the above figures, except plate voltage. Many 811A circuits are
> push-pull and so forth.]
>
> There are also better metals and alloys than there were in the 1930's
> (obviously).
>
> Most of the rest appears to be professional grade glassblowing, and I know
> very little about that, so I'm smart enough to assemble the tube innards
and
> let pros encase it in glass and evacuate it. (And possibly not glass if a
> stronger material would work.)
>
> My question for the List is this: What characteristics of the 811A
should
> be improved upon? For example,maybe we should put a physically stronger
plate
> in there that won't fail so quickly if it is heated to red. Do we need
more
> current carrying capability? Then it needs a better anode and grid. I
might
> have to blow dust off the books, but vacuum tube design is very well
documented.
>
> This might be really interesting.
>
> Thanks,
>
> Dave Small
>
> ******
>
>
> In a message dated 9/9/2008 6:31:47 P.M. Mountain Daylight Time,
> Sfxneon@xxxxxxx writes:
>
> If you are really into hand building everything that goes into your in
your
>
> VTTC, then how about making your own tubes like this guy:
>
> _http://blog.makezine.com/archive/2008/01/make_your_own_vaccum_tube.html_
> (http://blog.makezine.com/archive/2008/01/make_your_own_vaccum_tube.html)
>
>
>
> (http://blog.makezine.com/archive/2008/01/make_your_own_vaccum_tube.html)
>
> Long, but well worth it!
>
>
> Tony Greer
>
>
>
>
> **************Psssst...Have you heard the news? There's a new fashion
blog,
> plus the latest fall trends and hair styles at StyleList.com.
> (http://www.stylelist.com/trends?ncid=aolsty00050000000014)
> _______________________________________________
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