Operating instructions
FIL AUENT
VOLTA6E
VOLTA6E
atas
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Figure 16
,
Po'*-er
Sttltplg
Pf'-308
lU
RR, block
dia
grant.
F/LAn'tEn/r
VOLTA6E
TM
295-
r7
^
r/.
For 115-volt
a-c operation, the
positive
\r,lf11-s
act'oss
capacitor
C114 is sr-rpplied
to
the receiver
through series
regulator V101,
re-
sistor
R111, contacts
3 and 2
of relay
K101,
and
pin
6
of J101. For d-c
operation, contacts
of POWER
SELECTOR srn'itch
5101 and con-
tacts
1
and 2 of K101
are used in
place
of relay
contacts 3
and
2.
e.
The
positive
voltage across
C114 also
is
supplied to contacts
of
filament
voltage vibrator
E102
through a series circuit u'hich includes
regulator
V104, resistors
R115 and R116,
the
primary
winding
of
T103,
and chokes
L109
ancl
L110.
Operation
of the
vibrator
is
explained
in
g
belor.v.
.f.
Series
regulators V101
and V104
maintain
the
receiver B
r
and filament voltages constant,
despite
changes
in input voltage. For
this
pur-
pose,
the full
positive
output across C114 is sup-
pìied
to the
plates
and screens of
V101
and V104
and the control
grids
of these tubes are main-
tained at a constant
potential
b-v the action of
reference-voltage
regulator V103. The refer-
ence-voltage regulator
is connected
in
series
.\GO 3134
with current-limiting
resistor
R113
betr,veen
the
full
Bf
output and
gronnd.
If
the
R;
voltage increases
or decreases,
the resi-stance of
V103
changes
so as to
maintain
a constant
volt-
age
across
the tube. It
is
this constant
voltage
which is
suppliecl
to the control
grids
of V101
and
V104. In
the case of V104,
the voltage is
supplied
through isolation
and
gricl-current-
limiting
resistor R114.
Although
the control
grids
of the regulators
are held at
a constant
potential,
variations in Bf
voltage
(because
of
the variations
of
input
voltage)
are
present
at
the
plates
of
these tubes. Variation
in
plate
voltage
causes
a change in
plate
current
ancl a
corresponcling
change in cathode
bias. Althougir
an increased
plate potential
lolrrers
the re-qist-
ance
of
the
regulators,
the resultant increase
in
bias raises
the resistance.
Similarly,
rle-
creasecl
plate
voltage calrses increasecl
resistance
and decreased
cathode bias,
br,rt the decreased
bias causes
a decrease in resistance.
The rrr-er-
all effect is
a substantially constant loacì
ltoten-
tial at the cathodes
of V101 and \-101. The
cathode
potential
of V101 is suppliecì
to the
le-
B+ VOLTAGE
REGULATOR
vt
0l
HIGH
VOLTAGE
tcu I tt tEt
v ro2
VI
BRATOR
RECTIFI
ER
cR
r0l
FI
LAMENT
VOLTAGE
REGULATOR
vt04
F I LAMENT
VOLTAGE
VIBRATOR
E r02
FI
LAMENT
VOLTAGE
RECT I FIER
cR ro2
29