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Vacuum Tubes for Amps
How Are Tubes Made
How to make tubes:
Row upon row of nice ladies in smocks sit at benches with air-filtration
hoods
and slip the parts together with tweezers, then weld them in place with
small spot-welders. The completed assemblies are inserted into the glass
envelopes, then the base button (with pre-sealed-in wires for connections
and
a tube out the middle for exhausting gases) is sealed on with a rotating
flame-ring.
This assembly is put on a "sealex" machine, which pumps it down thru the
bottom tube while cooking the whole assembly with an RF induction heater
coil.
(this also flashes the getter, which was welded to the plate along with
other parts.)
After a couple minutes, the machine takes it out and seals the bottom tube
with
a flame and a pneumatic cylinder to lift the assembly. Once the tube is
sealed,
the base, labeling etc. can be applied. Miniature tubes are done the same
way except
the pump-down tube is on top and the base button is the entire base.
These tubes are plugged into a big aging rack, holding 100-200 tubes at
a time.
They are aged for 4-6 hours while monitoring the plate current. The aging
involves
starting with filament voltage at 25% above normal for 2-5 minutes
(depending on the
tube type being made), then reducing to normal operating voltages and
running it at the
limit of plate dissipation.
Inspectors check each tube at the end of burn-in, then box them up.
At least, that's how it happens at the Svetlana factory in St.
Petersburg. I even have
photos of this. Can't speak for other makers.....at least Svetlana doesn't
allow
smoking on the factory floor.....Scott! Any comments? :)
Eric Barbour
Svetlana Electron Devices
From sveteng--(at)--ol.com Mon Mar 10 22:11:44 CST 1997
Article: 41593 of alt.guitar.amps
From: sveteng--(at)--ol.com (SVETENGR)
Newsgroups: alt.guitar.amps
Subject: Re: How are tubes made???
Date: 11 Mar 1997 02:16:43 GMT
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Xref: geraldo.cc.utexas.edu alt.guitar.amps:41593
Sorry Mark, no prizes. Why, you some kinda masochist or something???
You WANT tubes that blow up? ........:)
As for that guy who wants to know how the grid are made:
it's a special lathe--two copper rods are chucked into it and the
grid wire is wrapped automatically at the pitch set on the lathe
controls. It also automatically swages the rods so the wire is
buried in the rods partway--the soft copper would have to melt
for the grid wire to get loose--the wire itself will break before that
happens.
All these interior parts are stuck into one mica spacer, then the plate
is put over all of them, then the other spacer is attached. It ain't easy.
micK pages
