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Page Title: Alignment of 42-Mc If. Amplifiers
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e. T h e 4 2 - m c i f . p r e a m p l i f i e r s u b a s -
sembly is also mounted at the top of tuning
u n i t 3, with the electron tubes in an in-
verted position. W o r k from the electron
t u b e side of this subassembly and adjust
the cores of networks Z402, Z401, and T401
t o obtain a maximum panel meter indica-
tion.
f. After completing the procedures given
in a through e above, align signal peaking
c o i l L431, in if. cathode follower stage
V410, as follows:
(1) S e t I F . C A T H O D E F O L L O W E R
d. Set the front-panel controls on the
ADJ switch S704 on the main unit
test set as listed in paragraph 88c except
power supply partition (fig. 51) to
for the FREQUENCY RANGE MC switch.
t h e open-circuited position.
Tuning unit 3 has no band switch.
(2) O b s e r v e t h a t t h e p a n e l m e t e r
pointer deflects to approximate
93. Alignment of 42-Mc If. Amplifiers
midscale, with the tuning unit 3 sig-
nal g e n e r a t o r  injecting a 12-
a. Set the frequency dial of the tuning
microvolt output signal (at 42 mc)
unit 3 signal generator to 42 mc and inject
into the 42-mc if. amplifier.
the output signal into if. preamplifier cable
(3) R o t a t e t h e t u n i n g u n i t 3 s i g n a l
assembly W402.
generator MICROVOLTS control to
b. Set the MICROVOLTS control of the
o b t a i n the full-power leve1 capa-
tuning unit 3 signal generator to produce
b i l i t y from the signal generator.
a n approximate midscale reading on the
Adjust the core of L431 (fig. 71) for
main unit panel meter.
a maximum output indication on the
p a n e l meter.
c. The 42-mc if. amplifier subassembly
(4) Set switch S704 to its c 1 o s e d-
is mounted in a horizontal position at the
c i r c u i t position and see that the
top of tuning unit 3. Working from the elec-
panel meter pointer indicates a
t r o n tube side of the 42-mc if. amplifier
f u l l - s c a l e  reading.
subassembly, adjust the cores of networks
(5) Repeat the procedures given in (1)
Z403, T408, T407, T406, and T405, in this
through (4) above to assure that a
sequence, to obtain a maximum panel meter
12-microvolt output from the
i n d i c a t i o n . As the 42-mc if. amplifier is
tuning unit 3 signal generator pro-
b r o u g h t into alignment, decrease the MI-
d u c e s a f u 1 l-scale panel meter
CROVOLTS control setting on the tuning
indication, while the SIGNAL AT-
unit 3 s i g n a l generator and the GAIN
TENUATOR DB switch on the main
control setting (if necessary) on the front
u n i t front panel set to the 20-db
p a n e l to maintain an onscale panel meter
position.
indication.
d. Working from the tube socket side of
g. After meeting the requirement in f
4 2 - m c if. amplifier subassembly, adjust
above, disconnect the output of the tuning
t h e cores of networks T408, T407, and
unit 3 signal generator from plug P407 on
T406 to obtain a further peak indication on
cable assembly W402. Reconnect P407 to
t h e panel meter.
its mating jack, J406, at the top of the rf
tuner (fig. 58). This procedure enables the
Note: If the 42-mc if. amplifier cannot be aligned
with the tuning unit 3 signal generator connected to
output of the rf tuner to pass through the
preamplifier cable assembly W402, connect the tun-
if. amplifier, through the detector and
ing unit 3 signal generator to cable assembly W403
e l e c t r o m e t e r assembly, and to the meter-
(connector P409) and repeat the procedures given
ing circuit in the main unit  e
in b, c, and d above.
203


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