Belt Valley times. [volume] (Armington, Mont.) 1894-1977, 1926-01-07
BY ARTHUR 2. MoRAsH, S. B.,
In Roston Herald.

In Boston Herald.
Many radio fans have, no doubt.
heard about some sort Of a process by
which inactive tubes may be restored
TO their former activity, but according
60 the many questions concerning IT,
there has been evidently shroud Of
mystery cast over the process.
Some know from observation, and
many others know through sad ex-
perience. that the vacuum tube con-
talns a filament that becomes luni-
nous when a current passes through
Il This hlament- receives lts cur
rent from the A battery. Contrary
to the popular belief the hlament is
not put in the tube for illumination
purposes, but 70 serve as source of
the electrons necessary In the mech
anism' Of the vacuum tubes A more
technical term for the filament Is
''hot cathode and simply means that
1t becomes a source OF negatively
charged particles known as electrons
when It reaches the proper tempera-
ture. This temperature Is obtained
by passing a current through the fla
fnent. For this reason It would per-
haps be more to the point to call
this current the "heatlng" instead of
the more common expression, fila
ment" current.
Treating Fiiaments.
The first filaments were OF pure |
tungsten. carbon, platinum. etc. but
II was soon discovered that the num- [
Der Of electrons emitted by the hot
cathode, or flameHt, could be enor-
mously Increased by coating the sur
face OF the flament with certain
chemical compounds The compounds
that proved to be the most active IN
this respect are the alkaline earth
oxides. such as barium, calcium, stron-
fium, etc.
However, a still more active mate
rial was discovered In recent years.
and is known as "thorlum oxide" It
may be Of Interest to know that It Is
OF the tltanium series of chemical
elements. and is used in the forma-
tlOn Of incandescent gas mantles
Another very interesting fact Is that
II is radioactive.
Because OF the compounds, two
general types OF fiIaments have come
Into prominence, they being the oxide
coated filaments and the thoriated Al
ament. The WD11 and - are ex-
amples Of the former, while the UV109
and UV201A tubes are In the latter .
lass AS the exIde-eeated alament !
,annot be rejuvenated. will not dis $
'uss II any further In this article, but L
viii focus my entire attention on the ?
horiated style element. a
This type Of flament consists OF {
ungsten core that has been treated
With thorium oxide, not merely coat y
ID with the compound, but actually Z
80 that the amount OF
ctive material on the surface Of the n
lament is comparatively small in
omparison with the total amount. It
) because Of this feature that tube
Employing fiiament OF this variety
eldom goes out OF service because OF
burned-out illament, but because the
has dropped below the
ecessary value. When this condition
as been reached the tube is said to
e inactive. The real significance Of |
hts expression Is that most Of the
ctive material has been evRporated
rom the surface of the fllament, and
s a, consequence the number OF cleo |
rons emitted is reduced TO very low |
alue. Now. you win remember that
just said that the ilament is Inn D
regnated with this active material,
o It becomes evident that II, by some
COX or crook. we can bring some OF tn
his remaining oxide to the surface pi
10 shall have tube that is theo- al
stically. as good as new. This is "
xactly what the process known as tn
Ilashing' is supposed to do, and in NJ
ANY coses actually does. ch
Now 20 ~Flash" a Tubs. CO
This process merely consists Of Ut
uFnlng the nlainent by passing a CO
aren't through 1t, but with the b IL
artery totally disconnected. Why ne
nonld the B battery be disconnecf- no
1 during the reactlpating measures5 VI
fefI, this IL necessary because with II
le b battery connected. the pogl- tn
We high voltage charge on the plate IN
ould cause the material to become fr
as fast as Il came 10 the tn
srfacN, which ID at best a very slow M
ze hence q IL necessary that we re- Is
ove the cause Of the exhaustion. a.
1here seems 70 be quite diver r.