The Challis messenger. (Challis, Idaho) 1912-current, 1925-12-09
showing
of Of

Radio tubes, like some of the oldel
under the strain Of constant work an(
require rest or need to be rejuve
mated. This rejuvenating process, a.
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
this condition with that due to an ex-
hausted ''B" battery If the tubes are
of the thoriated tungsten (X-L) fla
ment type they can usually be reju-
venated by a simple process, and made
to serve as well as new tubes Ia the
receiving set.
Two Cannot Be Reactivated.
ut 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 up no
process can renew it.
''The thoriated tungsten fiIaments,
however, used in most of the various
other types of tubes, contain the oxide
of thorium throughout the whole mass
of the tungsten filament. this oxide
having been originally put In mean
descent lamps to keep the filaments
from being too fragile. The filaments
are given treatment which produces
a 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
function properly. Reactivation is a
process which boils additional thorium
atoms out of the interior Of the tung-
stem filament and forms new layer
IF thorium atoms on the surface
Method Is Successful.
'1The thoriated filament was devel- |
,ped by the General Electric company,
which has also developed the methods /
# reactivating tubes Of this type The
bureau of standards has found that |
he reactivation process is quite sue
essful, and frequently makes a won
lerful difference in the results OBJ
aimed with a receiving set. The proc
SO is essentially the operation of the
lament for very brief interval at
pecified high voltage (called flash
ng'), followed by lower voltage for
longer time (called "aging), all Of
his with no grid or plate voltage.
he flashing reduces some of the thor
I'M and the aging forms the required
urface layer. The following schedule
( these operations is the result of
experience Of the Radio
Of America, and is pub
shed here by courtesy Of that COM
any:
FLASHING.
Fflament
Radiotron Voltage Time
x and wv 1879. .-...10 volts 80 sec.
x and wv 201-A. is volts / min.
X-120 ........... 10 volts l min.
AGING.
Radiotron Voltage limo
x and wv 1ss... As volts 10 min. I
x and wv COLA. rs volts 10 min
X-120 ... AS volts 10 min.
Exactly the same procedures apply
r O and OK tubes as for the UX
bes of corresponding number. Thus, s
and CX-299 correspond to U and G
X-199, c and CX-301-A to q and Tx b
Ia and CX-22O to UX 100. e
I'm carrying out this schedule It IS b
essential to have a volt e
ster of good degree of accuracy and O
use watch. No grid or plate volt g
es are used. Either alternating or c
.ect current may be used for heating p
. filaments. IL