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|  must be brought into the right
from the amplifier plate circuit at the
400-mc high-frequency end of the band.
s i d e of the rf tuner through the
(1) The dc path for applying B+ voltage
center partition. The ac heater
to the plate of the amplifier is un-
path consists of the following cir-
c o n v e n t i o n a l because the plate of
c u i t elements:
the coplanar triode is located on the
(a) T h e 6.3-volt ac line continues
left side of the grounding partition
from the if. preamplifier sub-
(A, fig. 69) in the rf tuner. The dc
assembly to rf choke L414, which
path consists of the following cir-
is mounted between an insulated
c u i t elements:
t i e - p o i n t terminal on the rear of
{a) T h e voltage set by the arm of
the rf tuner (A, fig. 69) and the
V401 ADJ control R405 (an
i n n e r conducting terminal of
alignment adjustment control) is
feedthrough capacitor C411,
fed to fixed resistor R402, which
which bypasses rf currents to
is mounted on the rear of the rf
ground.
tuner (A, fig. 69). The low poten-
(b) The inner conducting terminal of
tial terminal of R402 is connected
C 4 1 1 penetrates the rear of the
to the protruding terminal of
rf tuner and applies the ac volt-
feedthrough capacitor C410.
a g e through rf choke L408 to a
(b) T h i s feedthrough capacitor by-
second feedthrough capacitor,
passes r f c u r r e n t s t o t h e
C 4 0 7 . This feedthrough element
grounded rf tuner chassis and
p e n e t r a t e s t h e upright center
c o n d u c t s the plate voltage
partition which serves as a
t h r o u g h the chassis to the in-
A m o u n t i n g surface for the three
t e r i o r of the cathode input cir-
t u n i n g capacitors, C402, C404,
cuit.
and C413 (B, fig. 69). Feed-
(c) A wire lead conducts the B+ po-
t h r o u g h capacitor C407 further
t e n t i a l to a second feedthrough
filters the 6.3-volt ac power sup-
capacitor, C409 (B, fig. 69),
ply.
w h i c h is mounted through the
(c) The inner conducting terminal of
g r o u n d e d partition which sepa-
C407 connects the ac heater volt-
r a t e s the cathode input circuit
age to an rf choke, L407, which is
f r o m the plate output circuit.
connected in series with the elec-
(d) Resistor R401 is connected from
tron tube heater. A metallic clip
the plate side of C409 to bypass
c o n n e c t s the 6.3-volt ac voltage
t o the cylindrical heater elec-
capacitor C406. This network de-
t r o d e which protrudes from one
c o u p l e s the rf amplifier stage
from the B+ power supply.
e n d of the electron tube. `The
(e) R f choke L406 adds to the de-
h e a t e r return circuit to chassis
c o u p l i n g network by offering a
g r o u n d is completed within the
high impedance to frequencies in
tube envelope by the common
heater and the cathode ring. The
the uhf spectrum, and applies the
B+ potential to the center of
r i n g is connected to the tuned
pickup loop L404, which is part
c a t h o d e input LC circuit, which
of the plate tuned circuit.
consists of pickup loop L402 and
(4) A metallic bar to which LA04 is
tuning capacitor C402. Series
m o u n t e d completes the dc path
coil LA403 completes the 6.3-volt
t o the plate of the rf amplifier
ac circuit to rf tuner chassis
tube.
ground.
(2) T h e ac path for applying 6.3-volt
( 3 ) The rf output of amplifier V401 is
h e a t e r voltage to the filament of
inductively coupled to crystal diode
t h e rf amplifier is also unusual
CR401 through coils L404 and
because the heater voltage lead
L405.
61
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