Alignment of 42-Mc If. Amplifiers

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