Alignment of Second Oscillator

are the same. Set the front-panel

131. Alignment of Second Oscillator

controls as follows:

a. Test Equipment and Tool Required.

(1) Multimeter ME-26/U.

Setting

Control

(2) Alignment tool.

b. Test Setup.

MANUAL

CHAN SEL

(1) Perform the alignment test setup

SQUELCH

OFF

(para 129).

VOLUME

Fully to the right

(2) Set Multimeter ME-26/U to the

POWER

Turn to ON, momentarily

-3 volt dc range and connect the

dc probe to test point J305 (fig.

62).

(2) Set the controls of Radio Set Con-

trol C-1439/U as follows:

c. Procedure.

(1) Set MANUAL FREQUENCY UNITS

control to 9.

Control

Setting

Warning: The capacitor C340

SQUELCH

OFF

trimmer shaft is at B+ potential.

PHONE VOLUME and

Fully to the right

SPEAKER VOLUME

Avoid direct contact with shaft. Do

not short shaft to ground.

Radio-interphone

RAD

Perform procedures (2) and (3)

Note.

C a u t i o n : Do not key the transmitter unless the

below only when this subunit has been

ANT. jack is terminated in a proper load (either the

severely misaligned.

a n t e n n a or Radio Frequency Wattmeter AN/URM-

43A). Do not key the transmitter with a signal gen-

(2) Turn trimmer capacitor C340 (fig.

erator connected to the ANT. jack. Failure to ob-

62) clockwise to its stop; then tune

s e r v e these precautions will result in damage to

i t counterclockwise seven com-

the rt unit and to the test equipment.

plete turns.

Note. Allow at least 5 minutes for the radio set to warm up before

performing any alignment procedures.

(3) Adjust the slug of L310 (fig. 113)

so that the top of the slug is approx-

imately 1 inch from the top of the

130. Third Oscillator Check

tank compartment cover.

(4) Set the MANUAL FREQUENCY

Perform the following procedure before

UNITS control to 0.

aligning the if. amplifier subunits. If the

(5) Tune L310 for a maximum indi-

third oscillator does not meet the speci-

cation on the ME-26/U.

fications below, check V401B and make

(6) Set the MANUAL FREQUENCY

voltage and resistance measurements to

UNITS control to 9.

isolate the trouble (fig. 87).

(7) Tune C340 for a maxium indication

a. Test Equipment Required. M u l t i -

on the ME-26/U.

meter ME-26/U.

(8) Set the MANUAL FREQUENCY

b. Test Setup.

UNITS control to 0.

(1) Perform the alignment test setup

(9) Tune L310 for a maximum indica-

(para 129).

tion on the ME-26/U.

(2) Set the ME-26/U to the -10-volt

(10) Repeat procedures (6) through (9)

dc range and connect the dc probe

above until no further increase in

to test point J404 (fig. 56).

the voltage indication on the ME-

c. Procedure. Operate MANUAL FRE-

26/U can be obtained.

QUENCY TENTHS control from 0.0 to

(11) Set the MANUAL FREQUENCY

0.9. At each position, check the Multi-

UNITS control to positions 0

meter ME-26/U indication on receive and

through 9 and see that the voltage

transmit. The meter indication should be

at test point J305 is not less than

between 5 and 12 volts dc on both trans-

1.0 volt for each position.

mit and receive.

172