Power Amplifier Grid Drive Alignment and Bias Adjustments

TM 11-5820-509-35

and the POWER AMPLIFIER TUNE

a. Preliminary Procedures.

controls are being adjusted. Circuit

(1) Perform the microphone amplifier gain

damage can occur.

adjustment procedures detailed in paragraph 3-25 a (1)

(6) Set the POWER AMPLIFIER LOAD and

through 3-25 b (1).

POWER AMPLIFIER TUNE controls to the turns-

(2) Reduce the audio oscillator output to 0.01

counter values indicated on the LOAD-TUNE chart; then

+ 0.002 volts rms as indicated on the multimeter.

place the OPR-TUNE switch to TUNE and quickly peak

b. Adjustment Procedures.

the load and tune controls for maximum deflection of

(1) Connect the oscilloscope to test jack A2J2

the pointer on the XMTR OUTPUT meter.

(fig. 3 95).

NOTE

(2) Adjust A1R40 (fig. 3-94) until a 500-kHz

Adjust M ADJ control as required to

signal appears on the oscilloscope trace. (this indicates

maintain the XMTR OUTPUT meter

the operation of vox relay A1K1.)

pointer on the useful portion of the

(3) Return the POWER-LIGHTS switch to

meter scale.

POWER OFF and disconnect the test equipment.

(7) Return the OPR-TUNE switch to OPR and

(4) Return the RT-671/PRC-47 to its case

set the XMTR PWR switch to HI.

using the procedures of paragraph 3-11 if no further

(8) Again place the OPR-TUNE switch to

adjustments are required.

TUNE and peak the POWER AMPLIFIER LOAD and

3-27. Power Amplifier Grid Drive Alignment and

POWER AMPLIFIER TUNE controls as necessary for

Bias Adjustments

maximum XMTR OUTPUT meter deflection.

(fig. 3-96, 3-105, 3-110)

b. Alignment Procedures.

NOTE

(1) Adjust A3L67 (fig. 3-105) for maximum rf

Perform this alignment routine only

grid drive as indicated on the multimeter connected to

after it has been determined that an

test point J104.

equipment malfunction is caused by

(2) On the front panel of RT-671/PRC-47,

improper alignment (tracking) of

place the OPR-TUNE switch to OPR, set the

Signal

Data

Translator

CV-

KILOCYCLES indicator to 3000, and place the XMTR

1377A/PRC-47 (A8A3).

PWR switch to LO. On the antenna simulator rotate the

a. Preliminary Procedures.

selector switch to 3.0 MHz position; then repeat steps

(1) Remove the RT-671/PRC-47 from its

(6) through (8) of the preliminary procedures above.

case using the procedures of paragraph 3-11.

(3) Adjust A3L68 (fig. 3-105) for maximum rf

(2) Connect the primary power source to the

grid drive as indicated by the multimeter connected to

POWER connector of RT-671/PRC-47.

test point J104.

(3) Connect the rf probe of the multimeter to

(4) Repeat

step

(2)

except

set

test jack J104 (fig. 3-105) of the power amplifier.

KILOCYCLES indicator to 4000 and set the rotary switch

(4) Connect the antenna simulator of

on the antenna simulator to the 4.0 MHz position.

AN/PRA-4 and the dummy load to the receiver-

(5) Adjust A3L69 (fig. 3-105) for maximum rf

transmitter as shown in figure 3-110. Set the selector

grid drive as indicated by the multimeter connected to

switch on the antenna simulator to the 2.0 MHz position.

test point J104.

(5) On the front panel of RT-671/PRC-47, set

(6) Repeat

step

(2)

except

set

the controls as follows:

KILOCYCLES indicator to 5000 and set the rotary switch

(a) KILOCYCLES indicator to 2000

on the antenna simulator to the 5.0 M H z position.

(b) CW-FSK/VOICE switch to VOICE.

(7) Adjust A3L70 (fig. 3-96) for maximum rf

grid drive as indicated by the multimeter connected to

test point J104.

(d) XMTR PWR switch to LO.

(8) Repeat

step

(2)

except

set

(e) POWER-LIGHTS switch to POWER

KILOCYCLES indicator to 6000 and set the rotary switch

ON.

on the antenna simulator to the 6.0 MHz position.

CAUTION

(9) Adjust A3L71 (fig. 3-96) for maximum rf

Do not permit the OPR-TUNE switch

grid drive as indicated by the multimeter connected to

to remain in the TUNE position for

test pint J104.

more than a few seconds at a time

(10) Repeat step b (2) except set

while the POWER AMPLIFIER LOAD

3-128