Alignment of 400-700-Mc Rf Tuner, Tuning Unit 4

b. The 400-700-mc rf tuner is mounted

brought into alignment, decrease the

on the left side of tuning unit 4. To remove

MICROVOLTS control setting on the tun-

t h e three covers from the rf tuner, pro-

ing unit 3 signal generator and the GAIN

control setting on tuning unit 3 (if neces-

ceed as follows:

s a r y ) to maintain an onscale panel meter

(1) Loosen the two screws that secure

t h e adjustable slide for the V504

indication.

tube clamp to the side cover. Push

d. Working from the tube socket side

o f the 42-mc if. amplifier subassembly,

the slide up toward the top of the

a d j u s t the cores of transformers T506,

tuning unit to the limit of its travel.

T h i s action removes a plexiglas

T505, and T504, in this sequence, to obtain

a further peak indication on the panel

t u b e clamp on the interior of the

meter.

t u n e r from the top of oscillator

tube V504.

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 -

assembly is also mounted at the top of the

(2) T i g h t e n the two screws to secure

t h e adjustable slide in its highest

t u n i n g unit, with its electron tubes in an

position of travel.

i n v e r t e d position. Working only from the

e l e c t r o n tube side of this subassembly,

Caution: Failure to move the ad-

adjust the cores of 2502, Z501, and T501,

j u s t a b l e slide as far as possible

in this sequence, to obtain a higher indi-

before removing the s i d e cover

cation on the panel meter.

may result in breaking the glass

Note: Do not adjust the tunable core of if. trans-

envelope of the oscillator tube.

former T502. T502 is adjusted for peak tuning dur-

ing the alignment of the 400-700-mc rf tuner (para

(3) Remove the 10 screws and washers

97e).

t h a t secure the side cover to the

f. After c o m p 1 e t i n g the procedures

4 0 0 - 7 0 0 - m c tuner. Lift the side

given in a through e above, align signal

c o v e r off and place it on a clean

peaking coil L535 in if. cathode follower

s u r f a c e , free of grease and metal

stage V512, by following the identical pro-

filings.

c e d u r e as outlined in paragraph 93f for

(4) T o gain access to the plates of

tuning unit 3.

tuning capacitor C520, remove the

g. After completing the alignment of the

four s c r e w s and washers that

i f . amplifier (a through f above), discon-

secure the top cover to the tuner.

nect the output of the tuning unit 3 signal

Lift the top cover off and place it

generator from input jack J509 on the pre-

on a clean surface.

a m p l i f i e r . R e c o n n e c t plug P509, which

(5) To gain access to the crystal diode

terminates the output cable from the 400-

c o m p a r t m e n t , r e m o v e t h e four

7 0 0 - m c tuner, to jack J509. This proce-

screws and washers that secure the

dure enables the output of the 400-700-mc

Z-shaped cover to the bottom area

t u n e r to pass through the if. amplifier,

of the tuner. Lift the Z-shaped

through the detector and electrometer

cover off to gain access to crystal

a s s e m b l y , and to the metering circuit in

d i o d e CR502, inductor L514, and

the main unit.

fixed capacitor C523.

97. Alignment of 400-700-Mc Rf Tuner,

c. Inject the unmodulated output of the

t u n i n g unit 4 signal generator (para 81)

Tuning Unit 4

t o the main unit front-panel SIGNAL IN-

(fig. 72)

PUT jack. The coaxial cable assembly

a. Align the 400-700-mc rf tuner while

( t y p e 84-Z2-3) supplied with the tuning

t h e tuning unit is operating outside the

unit 4 signal generator is terminated in a

main unit. Use the test harness (fig. 46),

UG-21B/U at each end; therefore, no adap-

w i t h the front-panel controls set to the

t e r is required for mating the main unit

p o s i t i o n s listed in para 88c, except for

SIGNAL INPUT jack.

s e t t i n g the FREQUENCY RAN G E-MC

d. Allow tuning unit 4, the main unit, and

switch to the 400-700-mc position.

209