Operating instructions

Sections 8
and 9. rear,
select
winding
A of T8.
Section
9,
front,
grounds
the
unused
windinss.
The
padder
netrvork
changes.
/.
When BAND
S\\r. srvitch
51
is
placed
in
band 4
position (fig.
24),
r,vinding
E
of T8 is
used, and
all other windings
are
grounded.
g.
The capacitors
connected
across
the u'ind-
ings
of
ali the r-f
transformers
except T1
and
T5,
and contained rvithin
the coil
assemblies,
are
negative-temperature
compensating
capaci-
tors. These
capacitors
are
nsed to
prevent
drift
of the oscillator.
Thus,
on
all bands,
the oscil-
lator is
temperature-stabilized
to compensate
for
the normally
expected
expansion
of other
components
and thus minimize
oscillator fre-
quency
clrift.
55.
Converter
V3
(figs.
24 and 25)
The
analysis of
the converter stage
u'ill be
discussed
in
complete detail for
band 1. The
analyses
of bands 2, 3,
and
4
will cliscuss
the
circuit
variations that
are accomplished
by band
srvitching.
a. The incoming signals
are conplecl incluc-
tively to the seconclar.r' of u'incling
C of
T3
(fig.
25). This rvinding is
tuned by section
C1C of
the
I\{A}[I'AL-PRESET
TUNING
capacitor.
Section 7.
rear.
of
BAND
SW. switch
51
con-
nects
the capacitor across the r,r'incling. The
tunecl circuit is coupled
to the
grid (pin
6) of
V3 through capacitor
C19.
Resistor
R7
pro-
vides
bias
voltage ancl a d-c return for
the
gricl
circuit. When
BAND
SW.
sr,vitch
51
is in
bancl
1
position,
section 7, flont
(fi,g.
24),
grounds
the
secondaries
of the r-f
transformers
not in
use-in this case,
D
rvinding of T3,
C and
D
u'indings
of
T7.
b. The
converter
utilizes a 1R5
pentagrid
converter
tube.
Filament
voltage
for the tr,rbe
is obtained from
pin
11
of J4 through
r-f
choke
L1.
Screen
voltage
is
supplied through
voltage-
dropping resistor R9 from the 90-volt d-c
poten-
tial
present
between
pin
6 of
J4
and
ground.
Cnpacitor
C21
provides
an
r-f
ground
for
the
sclreen.
Plate voltage
is
obtained
from
the
90-
'
',11
d-c
potential
through the
primary
of
T9
;rich
is fixed tuned by a
270-p.1,f capacitor.
".
Tube
V3
mixes the r-f signal
input
and the
.r'nal
of
the
local osciìlator
(par.
54), and
de-
+z
velops
a signal
at
the difference
frequency
of
455 kc.
The
signal is
der-elopecl
in
the
primary
of T9
and
coupled inductivell'to
the
secondary
of T9.
d.
When
BAND
SW. srvitch
51
is
in
band
2
position,
the foilowing
circuit
changes
are
ef-
fected
(fig.24):
(1)
Section
'1,
teàt,
seìects
the D
winding
of T3 in
place
of
the
C
r,vinding.
(2)
Section
7, front,
grounds
the
C rvind-
ing
of T3
atrd removes
the
ground
from
the D rvinding.
e.
In band
3
position
of
BAND
SW. switch
S1
(fig.
24),
section
7, tear,
selects
the
C
rvind-
ing
of T7,
and
section 7, front,
grounds
the D
wincling
of T3.
/.
In band 4
position
of
BAND
SlV. srvitch
51
(flg.
24),
section
'7,
reat,
selects
C winding
of
T7,
and
section
7,
front,
grounds
D
winding
of T7.
56.
First
l-f Amplifier
V4
(fig.
26)
The
i-f amplifìer
stage is tuned
to
455
kc and
operates
at this frecluencl'for
all
bancls of oper'-
ation of
the receiver'.
o.
The
signal tlevelopecl
in
the converter
stage is
conpletl incluctively
to the
.sl'irl
(pin
6)
of V4,
through
the
rvinding-q
of
transformer T9.
The
ar-c cilcuit
(thror-rgh
R15
ancl
R18)
pro-
vicles a d-c
return for
the
grid,
rvhen PHI{.-
C.W.-NET-CAL.
su'itch
52
is in PHN.
position.
Capacitor C22 is
the avc filter capacitor. \\rhen
function
srvitch
52 is in any
position
other than
PHN.,
the
grid
is returned
to
ground
through
section 1, rear,
of
S2.
b.
The
first i-f amplifler
Llses a
1L4
pentode
tube.
Filament
voltage for
the tube
is
obtained
from
the
1.4-volt
d-c
potential
at
pin
11
of J4.
Screen
voltage is
supplied through voltage-drop-
ping
resistor R10
and
section
3, rear, of func-
tion srvitch
52
from
the arm of R.F. GAIN
control R32. The
gzrin
control
is
connected
across the
9O-volt
potential present
between
pin
6 of
J4 and
ground.
Capacitor
C49
is
a
noise
filter, and capacitor C23
places
the
screen
at r-f
grouncl
potential.
Plate
voltage is
sup-
plied
from the 90-volt
potential
through the
primary
of T10.
AGO 313^{