Operating instructions

tions,
reÌa1'
K1
can
be
energized
through
con-
nectior.r
to
an associated
transmitter,
to disable
the receiver
during
transmissions.)
Capacitor
C33
places
the screen
at
a-f
ground
potential,
and
C32 decouples
the
plate
and
screen
circr-iits
from
the B-l-
supply.
Plate
voltage
is
suppliecl
from
pin
6
of J4
through
plate
load
resistor
R21
and
the rela;'
circuit.
c.
The
amplified
audio
signal
is
developed
across
R21
and is coupled
capacitively
by
C34
to A.F.
GAIN
control
R19B
ancl resistor
R22.
R22
determines
the minimum
signal voltage
fed to
the
low
and high
a-f amplifiers.
A
por-
tion of this
signal voltage
(depending
on A.F.
GAIN control
setting) is
coupled
to
the high
a-f amplifier
through
C35, and is
coupled to
the
low
a-f
amplifier
through
C35 and
C47.
60.
Low A-f
Amplifier
V7
(fig.
28)
A-f amplifier
V7
is
used
only u'hen
OUTPUT
HIGH-LOW
su'itch
54
is in
the
LOW
position.
The
tube amplifies
the audio signal
taken from
VG
and couples it to
the loudspeaker
ancl the
headset. The loudspeaker,
rvhich is
located in
the
power
suppl;r, may
be disconnected
lvhen
SPEAKER
ON-OFF
srvitch
5102
is
in the
OFF
position.
a. The input signal
to tribe V7 is coupled
from the output of V6
thror"rgh capacitors
C35
and C47.
R30
and
R31
act as the cl-c
return
resistors for the control
grid.
R30
also
fr"rnc-
tions as
part
of a
voltage divider
(R26,
R27, and
R30) for the negative voltage
present
betu'een
pin
8
of J4 and
grouncl.
The voltage
at the
junction
of resistors R30 and R27 is
suppliecl
to
the
grid
of V7 as bias voltage.
Section
1,
rear, of PHN.-C.W.-NET-CAL.
srvitch
32 short-
circuits
R30
to
ground
on all
positions
of
the
su,itch except
PHN.
This
action removes the
fixecl
bias
from the stage and
improves its
stability.
b.
The
lorv
a-f
amplifier stage Llses a
portion
of a
1R5
pentagricl
tube,
rvith
the filament. last
four
grids,
ancl the
plate
as a
pentocle
amplifier'.
,rrilament voltage
is supplied from the 1.4-volt
i-c
potentiaì
at
pin
11
of J4 through r-f choke
?.
Capacitor
C45
bypasses af to
ground
at the
,ament.
Screen
voltage
is sr.ipplied from
pin
of J4
through
voltage-dropping
resistor R28
46
ancl
a
portion
of the rvinding
of
bfo tank
trans-
frirmer
T13.
Capacitor
C41 clecouples
the
screen
circuit from
the
po\\'er
suppl;r.
Plate
voltage
is
sttppliecl
through
the full
primary
u'inding
of
T14
and OUTPUT
HIGH-LOW
srn'itch
54. Ca-
pacitor
C42
is
an h-f
b1'pass.
c.
The
signals
ai'e ampliflecl
by the
tube
and
the output
is couplecl
inductively
from
the
pri-
mary
of
T14
to the seconclar]'
of T14.
The
full
secondary
u'incling
of
T141 is
connected
to
PHONES
connectors
J2 and
J3, and
a
portion
of
the secondary
is
tripped for
the loudspeaker.
The
signal
for
the speaker is
suppiied
from
pin
9 of
J4 to
pin
9 of
J101 in
the
po\\,er
supply,
thence through
SPEAKER
ON-OFF
sr.vitch
3102
to the speaker.
d.
Section 3,
rear,
of PHN.-C.W.-NET-CAL.
srvitch
52 connects
voltage-dropping
resistor
R29 in
parallel
u'ith
R28
and increases
the
screen
(bfo
plate)
voltage
of
the
tube in
all
positions
of function
su,itch
52,
except PHN.
61.
High
A-f Amplifier
V8
(fig.
2e)
A-f
amplifier
tnbe
V8
is
used
only
rvhen
OUT-
PUT
HIGH-LOW
su'itch
S'1
is
in
the
HIGH
position.
The
tube
amplifies
the auclio signal
taken from
V6 and conples
it to the loudspeaker
and/or
phones.
The
speaker ma)-
be discon-
nected
in
this mocle
of operation
by turning
the
SPEAKER
ON-OFF srvitch
to OFF.
a. The
input
signal to tube
V8
is
coupled from
the output
of V6 through
capacitor
C35.
Bias
voltage is
supplieil from the
voltage divider
(R26,
R27, and
R30)
rvhich
is
connected
be-
trveen
pin
8
of
J4 and
ground.
The negative
r,olta.qe
at the
junction
of
R26
and R27 is
sup-
plied
zrs bias to the
gricl (pin
6) of V8
through
R2.1. R2.1, R27,
and R30 form
the
grid
d-c
re-
turn circuit for
the PHN. setting
of PHN.-
C.W.-NET-CAL.
su'itch
52.
For
all other
set-
tin.gs of
the
srvitch,
resistor
R30 is short-cir-
cuitecl to
gronncl,
thus increasing
the bias volt-
aqe
on V8.
b.
The
high a-f amplifier stage
uses
a 3V4
pentocle
tube. The filaments
of the
tube
are
connected in
parallel
through
SB
and
contacts
4
and 5 of 54
for
1.4-volt
operation.
Filament
voltage is supplied
from
pin
11
of J4.
Capacitor
C39
is
an a-f filter for
the filament
circuit.
AGO 313A