Belt Valley times. [volume] (Armington, Mont.) 1894-1977, 1926-11-04

Described

Describe
5 me biggest difficulty to-he- over
! come Ia obtaining "A" current from
the house a. c lighting supply is IN
} finding a rectlfer that viii pass suf
ficient- current for-the- hfanieHfs=
yet make battery elimination an eco.
nomical proposition. In the course OF
description OF an efficient "a. /" "B. "
&C" line supply device ln the Radio
Broadcast Magazine. b. r. Roland
] writes as follows: "A logical solution
% the difficulties Of "A" power filter
ing Is TO connect the filamenls Of the
radio tubes In series. thus reducing
the overall current consumption.
1.-THE accompanying diagram shows
a unit which has been found entirely
satisfactory for use In conjunction
with receiver employing 100 type
tubes In series. Due 10 the fact that
the current consumed is small. the
filter choke coils are OF reasonable
proportions. Tbs device viii supply
yoltages and, currents as follows:
"a battery-G0 miIliamperes. 9 TO
80 volts.
"5'B' battery-Up TO % milliamperes,
at 200 volts. 30 (variabie) volts, 40
(variabIe) volts
&C battery-From to 90 volts.
''The use Of the device is. Of course,
restricted 10 radI0 receivers employ
ing tubes similar In. characteristics to
the UX-109 or DV-3 tubes with, fla
ments wired In series, and under these
conditions It's performance as uni
versal power is ideal The device IL
Illustrated Is adaptable TO any type Of
radio circuit and has been used with
success on a three-circuit regeneratiye
set the Browning Drake. and tuned
radio-frequency receivers. with varia-
lions Of each type. Transformers
sistance or mpedance-cOupled ampli-
fers have been employed IndlscrImi-
nately with equally good results.
The Power Transformer
#sIn the diagram, I, is General ra-
do power transformer designed for
80 watts, 40 volts, at full load. The
high voltage secondary provides $50
volts each side OF the tap at the cen-
ter at no load. The third winding, r..
provides s volts at amperes for the
raw a. c. hlament supply OF an UX-
112 or UX-171 power-amplifier tube.
This may be supplied by a separate
filament lighting TRANSFORMER. In this
construction, a Brach unit serves the
purpose nicely. across each half Of /
the secondary, #, Is connected a Oh
mIerofarad buffere CONDENSER q and Ga
Of ]. OOO-voJt cash test type. The out !
er ends Of this winding are connected
to the fiiament terminals OF STANDARD
UX type socket. into which is plugged
the new type BIZ Raytteon rectifer,,
Ra, which is capable Of passing So mill
lamps. The plate terminal Of the
socket, corresponding TO the cathode
o. the RaytbeeBe tEiha.sisa conBeeted-ta
the plus side OF the filter circuit. The
filter circuit Of this power unit In
cIudes choke coils, L, capable Of pass.
Ing IS miIlIamperes direct current
without heating, and having a residual
inductance OF at least Is henries per
choke at this value Of direct current.
The General Ra8io type 1896 standard
''B"-substltute choke Is admirably
suited for this service. Others which
fulfill the above requirements viii
probably be equSlyas satisfactory.
"The voltage-control unit shown al
the right-hand end Of the diagram
has been tried under all conditions.
and has given good service. There
was some difficulty In obtaining prop
er values and current-carrying capaci-
ties OF the various resistors and. afterd
testing. the units speoI-
fed were adopted. All OF the parts In
The control unit may be obtained from
regular stock Of the various manufac-
turers or their dealers. For the plate
voltage Of the power-ampIIfer tube,
the maximum B' Plus is taken direct
" from the terminals of the filter cir
.mt. This terminal provides approxi- !,
nateJy 200 volts at full load A claro-
tat, r.. Is used TO control the volt
lge output Of the next lower tap (B'
,lus Init and win give from 90 10 Z,
35 volts approximately on the usual
Dlate-current drain al This vOltageo II
me 'Bsplus- defector stap Is Obtainedi
hrougt jtbe use Of another clarostat :
n a. Bradleyehm No. 10. r. .opessmlasll :.
refarad condensers are connected IN /.
9th OF these cases from the 'B' plus }.
ariaBle 70 b minus TO bypass rhe0. !
TAT noises. and 70 prevent undesirable I I
5nbiing between fhe various ampai- :.
1
IL @ev Battery Voltage. b.
The &c battery voltage IL obtained /.
rom . wfre-wound variable resistance
Z the proper value A. this resist
nee carries the fuii=i0ad current 81 q
he device, n must be designed 10 D
-, m 81 as t.,fiIlamucrea Without II