The Ely miner. [volume] (Ely, Minn.) 1895-1986, 1925-12-04

| Radio tubes, like some of the older
humans. eventually lose their pep"
under the strain of constant work and
require rest or need to be rejuve-
mated. This rejuvenating process, as
applied to vacuum tubes, is not as Sc
rious an operation, however, as the one
some humans undergo in the search
| for youth.
1t is known as "reactivation" and
is said by the bureau of standards ra-
dio experts to renew the sensitivity of
electron tubes of the thoriated lungs
ten filament type.
Concerning this method of reactiva-
ton 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 operates very
| poorly or not at all, even though the
tube filament is not burned out The
user of the set frequently confuses
hausted "B" battery. If the tubes are
of the thoriated tungsten (X-L) fla,
ment type they can usually be reju-
venated by simple process, and made
to serve as well as new tubes In the
receiving SET
Two Cannot Be Reactivated.
at happens that most of the tubes
now used are of the thoriated tung-
stem type, and it therefore becomes
Of quite general interest for the pub
lie to know how to secure the full life
of their electron tubes The WD-11
and WD-12 types of tubes are the only
ones extensively used which cannot, be
reactivated. In these tubes the source
of the electrons is coating of certain
oxides on the surface of the filament,
and when this has been used I'D no
process can renew 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 mean
descent lamps to keep the filaments
from being too fragile. The filaments
are given a treatment which produces
layer of atoms of thorium on the
surface of the tungsten, and this thor
ium, which is radioactive, emits cleo
irons much more copiously than the
tungsten would. After long use, or
after burning the filament too bright
ly, the layer of thorium atoms is evap-
Grated off, and so few electrons are
then emitted that the tube does not
function properly. Reactivation is a
process which boils additional thorium
atoms out of the interior of the tung-
stem filament and forms new layer
OF thorium atoms on the surface.
Method Is Successful.
The thoriated filament was devel-
oped by the General Electric company,
which has also developed the methods
of reactivating tubes of this type. The
bureau of standards has found that
the reactivation process Is quite sue
cessfur, and frequently makes a won
derful difference in the results OBJ
tanned with receiving set. The proc
ess is essentially the operation of the
filament for very brief interval at 1
specified high voltage (called flash
ing'D, followed by lower voltage for
longer time (called "aging''), all Of
this with no grid or plate voltage.
The flashing reduces some Of the thor
ium and the aging forms the required
surface layer. The following schedule
of these operations is the result of
extensive experience of the Radio
Corporation of America.
A SIIJNn