Operating instructions
3
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UF
ISI
I.FAùIPLIFIER
2 D
I-F AMPLIFIER
CALIBRATION OSCILLATOR
v5
rR5
I9
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:
Rt7
47K
.OI
UF
t
t
ll
I
tl
;
ll
TT
I
T
G
J4
(PtN
6)
+90
t/
0c
I. UNLESS
OTHERWISE
INDICATEO:
ALL-RE'SISTANCE
VALUES
ARE IN
OHMS.
ALL
CAPACIÎANCE
VALUES
ARE IN
MICROMICROFARAOS.
ALL
INOUCTANCE
VALUES
ARE
IN HENRYS.
2.K
:
l,000qHMS
3.
MEG
-
I,OOO,oOo
OHMS
4. UF
=
MICRoFARADS
5.
MH
:
MTLLTHENRYS
REA
R
6. UH
=
MICR0HENRYS.
7
S2 SHOWN IN PHN.
POSITION.
8.
SECTION I IS
NEAREST
THE KNOB
END.
9. SWTTCH
SECT|ONS, AS
V|EWED,
ROTAîE
COUNTERCLOCKWTSE
c. Tube
V4 amplifies
the i-f
signal
and
de-
velops the
signal across
the tuned
primary
of
i-f
transformer
T10. The
signal
is
coupled in-
ductively
to the
tuned secondary
wincling in
the
grid
circuit
of the
second i-f
amplifler
V5.
57.
Second
l-f Amplifier
V5
(fig.
26)
The
operation of the
second
i-f
amplifier
is
similar to the operation
of the flrst
i-f
amplifier'.
a. The signals
amplified by i-f
amplifler tube
V4 are
coupled inductively
to the secondar5' of
T10,
and
fed to the
grid (pin
6) of the seconcl
i-f
amplifier tube V5.
The
grid
circr"rit is
re-
:urned
directly to
ground.
During
C.W.,
NET,
nd
CAL.
operation, the
output of the
bfo also
{
supplied
to the
grid
of
V5
(par.
62).
4+
TM
295-27
b.
The
second
i-f
amplifier
tube
is
a
pentagrid
converter
1R5
tube. In
this
circuit,
only
the
filament
(cathode),
the last
three
grids,
and the
plate
are
used
as the i-f
amplifier.
(The
re-
maining
grids
are
used in the
calibration
oscil-
lator
circuit
(par.
63).)
Filament
voltage for
the tube is
obtained
from
the 1.4-volt
d-c
poten-
tial
at
pin
11
of J4.
Screen voltage
is supplied
through
the 10K-ohm
voltage-dropping
resis-
tor, the coil
in T12
assembly,
and
parasitic
suppressor
L3.
Capacitor
C48
places
the screen
at
r-f
ground
potential.
Plate
voltage is
supplied
from the 90-volt
d-c
potential
between
pin
6
of
J4
and
ground,
through voltage-dropping
resis-
tor R16
and the
primary
winding
of
T11.
Ca-
pacitor
C28
and resistor R16
form
a
plate-cir-
cuit decoupling network.
Fígure 26,
Radio Receiuet'R-I74/tlRR,
fi.rst
artcl seconcl
i-f amplifiers,
.f
uttctional
schamatic.
AGO 313A