Evening star. [volume] (Washington, D.C.) 1854-1972, 1923-04-15
SKILL NEEDED in MODERN
/ RADIO TUBE PRODUCTION
s:Electro-Mechanical Brains'' of Receiv.
ing Outfit Now in Daily Use to
Extent of Three Millions.

which must be eliminated for the
effectual protection of the tube and
Its satisfactory operation.
The harmful gasses can be elm
| mated sufficiently from the flame mt
! during the process of evacuation by
simply circulating a heating current
through 1t of greater value than that
| used in the normal operation of the
! tube for radio purposes.
This method cannot be employed in
| connection with the grid and plate
| however, because they do not of
| themselves form closed electrical cir
cults as does the t1lament, and there
! fore ordinary heating currents cannot
| be circulated through them. Likewise
the glass Of the bulb, not being an cleo
trical conductor. 1t Is obvious that
electrical currents cannot be circu-
lated through it for heating purposes.
The methods employed utilizes fur
| mace heat for the glass bulb. electric
current for the filament and "electron
bombardment" for the grid and plate.
The tube is placed in heating fur
mace. which Is then brought to a tenn
,, melting point of glass. The intense
, heat drives the harmful gases out
OF the glass and into the surrounding
space and also into the space within
the bulb itself.
heating value much higher than that
normally used in the operation of the
tube for radio purposes is circulated
through the tilament circuit, thereby
bringing the filament to a tempera-
ture sufficiently high to drive out the
harmful gases and at the same time
give off an abnormally large stream
of "electrons."
These electrons are drawn through
the grid to the plate under the in
fuence of u potential difference be-
tween filament and plate such as to
maintain the plate highly positive
with respect to the filament.
"EIectron Bombardment.1
Under these conditions, the invis-
ible electrons strike or collide against
the grid and also the plate with such
force and in such numbers as to bring
these two electrodes to a red heat
thereby driving the harmful gasses
out of these elements and into the
space within the bulb. The latter
as "electron bombardment" of the
grid and plate.
Simultaneous with these various
actions, a vacuum pump operates on
the tube. drawing out both air and
the released gases from the space
vacuum within the bulb sufficiently
high for all purposes for which the
tube is designed.
With the completion of these pro-
cesses, each individual tube Is tested
for it's filament voltage and amperage
rating, the resultant current flow in
the. grid circuit and the plate circuit
and for any evidences Of possible par
tial loss Of vacuum or the presence Of
harmful gases remaining In the tube.
The present extensive manufa "ture
Of vacuum tubes involves the services
of glass blowers for the production
of the fragile bulb, the mechanic for
the manufacture Of the filament, grid,
plate and base and their assembly
and the radio technician for the final
assembly of the tube and it's prepara-
ton for radio work and their testing
for defects or otherwise when the
product is finally completed.
The miniature radio receiving tube,
which survives the process of manu-
facture, assembly. evacuation of air
and gas, and its final test, is A most
delicate and sensitive electrical de-
vice, work Of art in electro
mechanical craftsmanship.
Copyrighted. 1873. 2Ist Century Press.)