Evening star., 1925-10-18
RADIO TUBES GAM
Be REACT|VATED
Bureau of Standards Gives
Simple Process for Use
| of Set Owners.

Radio tubes, like some of the older
humans, eventually lose their pep
under the strain of constant work
and require a rest or need to be
rejuvenated. This rejuvenating proc
ess. applied to vacuum tubes is
not as serious an operation, now
ever, as the one some humans un-
dergo in the search for youth.
1t is known as "reactivation" and
is said by the Bureau of Standards
radio experts to renew the sensitivity
of electron tubes of the thorlated
tungsten filament type.
Concerning this method of reacti-
walton the bureau has issued the fol.
lowing report. so skilled listeners can
"pep up their tubes themselves:
"Electron tubes in radio receiving
sets eventually lose their sensitiVity
This sometimes progresses to the
point where the receiving set op-
crates very poorly or not at all, even
though the tube filament Is not
burned out. The user of the set ire
ouently confuses this condition with
that due to an exhausted b battery.
If the tubes are of the thorlated
tungsten (X-L} tilament type they
can usually be rejuvenated by SIM
Die process, and made to serve as
well as new tubes in the receiving set.
Two Cannot Be Reactivated.
1T happens that most of the tubes
now used are of the thoriated tung-
stem type. and it therefore becomes or
quite general interest for the pubtc
to know how to secure the full life
of their electron tubes. The Will
and WD-12 types of tubes are the
only ones extensively used which can
not be reactivated. In these tubes
the source of the electrons Is coat
ing of certain oxides on the surface
of the filament, and when this has
been used up no process can re-
new 1t.
"The thoriated tungsten filaments,
however, used in most of the various
other types of tubes, contain the
oxide of thorium throughout the
whole mass of the tungsten f1lament,
this oxide having been originally put
in incandescent lamps to keep the
flaments from being too fragile. Ihe
filaments are given treatment
which produces a layer of atoms of
thorium on the surface of the
tungsten. and this thorium. which is
radioactive, emits electrons much
more copiously than the tungsten
would After long use, or after burn
ing the filament too brightly, the
laver of thorium atoms is evaporated
off. and so few electronS are then
emitted that the tube does not func.
ton properly. Reactivatlon Is
process which boils additional thorium
atoms out of the interior OF the
tungsten filament and forms new
Iayer OF thorium atoms on the sur
face.
Process Successful.
"The thoriated filament was develop
ed by the General Electric Co.. which
has also developed the methods Of re-
activating tubes of this type. The
Bureau Of Standards has found that
the reactivation process is quite sue
cessful and frequently makes Won
derful difference in the results obtain
ed with a receiving set. The process
Is essentially the operation of the lila
ment for a very brief interval at
specified high voltage Called flash
ing"), followed by a lower voltage for
a longer time Called "aging"D, all of
this with no grid or plate voltage.
The flashing reduces some of the
thorium oxide in the wire to
thorium and the aging forms the re-
quired surface layer. The following
schedule of these operations Is the
result of extensive experience of the
Radio Corporation of America, and is
published here by courtesy of that
Cop1napv