Frequency Generation Circuit Tests

TM 11-5820-509-35

Item

Indication

Probable trouble

Procedure

Shorted capacitor in power

Check continuity of L105

amplifier plate circuit.

(normal 3.2 ohms} and verify

that none of the plate tank

capacitors is shorted: replace

L105, C105, C108 thru C122 if

defective.

Plate voltage circuit in main

Check continuity from S103A.8

chassis defective.

to L122-1, from L122-2 to C29,

and from C29 to J1-A2.

Resistance of L122 is 11.6 ohms.

Repair circuit or replace

defective component.

of malfunctions to a module within the frequency

c. Frequency Generation Circuit Tests. Perform

generation and control circuits.

the following procedures in the order listed for isolation

Item

Indication

Probable trouble

Procedure

Place the POWER LIGHTS switch on the front panel of RT -671/PRC 47 to POWER OFF. Connect the test equipment for

receiver tests (fig. 3 2). Adjust the frequency control knobs for a reading of 2225 on the KILOCYCLES indicator; adjust the

signal generator for 2.0 microvolts output at 2226 kHz. Rotate the VOLUME control on the front of RT-671/PRC-47 to its

maximum clockwise stop and then place POWER-LIGHTS switch to POWER ON

No signal, or erratic operation at

a. Hf oscillator circuit in signal

a. Measure waveform at A7J3;

selected frequency.

data translator A3 defective.

normal is 3.5 volts pep at a 0.3-

microsecond rate. Measure

waveform at test jack A3J5;

normal reading 8.0 volts p-p at a

0.3-microsecond rate. Repair hf

oscillator circuit (para 3-13c) or

replace CV-1377A /PRC-47.

b. Hf oscillator circuit on main

b. Check continuity from J10-A2

chassis defective.

to J5 A2; repair defective cir-

cuit.

c. 500-kHz standard signal circuit

c. Check waveform at test jack

of radio frequency oscillator A6

A6J4. Normal reading is 4.25

defective.

volts pep: measure waveform at

test jack A6J3. Normal reading

is 3.5 volts pep; repair oscillator

circuit (para 3-13e) or replace 0-

1032/PRC-47 if defective.

d. 500-kHz standard signal circuit

d. Check continuity from J9-A2 to

in main chassis defective.

K4-8, from K4-8 to K4-2 and

K4-7, and from K4-2 to J4-1.

Repair circuit as necessary or

replace K4 if defective. Also

check continuity from J9-A3 to

J10-A3 and repair if open.

e. 1-MHz pulse generator circuit

e. Measure waveform at J11-A1

in oscillator control A7 defec-

(main chassis). Normal reading

tive.

5.5 volts pep. pulses at

1.0-microsecond rate. Repair 1-

MHz pulse circuit (para 3-13f )

or replace C-4311/PRC-47.

5- to 14-MHz amplifier circuit

Measure waveform at J11-A2

in signal data translator A3 is

is (main chassis). Normal reading

defective.

3.0 volts p-p at 0.5-microsecond

rate. Check continuity from J11-

A2 to J8-A2 and from J11-A1 to

J8-A1. Repair circuit (para 3-

13c ) or replace CV-1377A/PRC-

47.

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