Test Set, Radio TS-1967/ARC-54 Audio Amplifier A1

TM 11-6625-601-34

Test Set, Radio TS-1967/ARC-54 Audio

1-12.

2 of the motor control unit to pin 1 of relay K1.

Amplifier A1

Relay K1 energizes, which applies +27.5 volts

(fig. 1-6)

dc through pins 3 and 8 of relay K1 to terminal

5 of the motor control unit. From terminal 5,

Audio amplifier Al consists of a voltage reg-

+27.5 volts dc is applied to motor B1. Motor B1

ulator, three audio amplifier stages, and two

turns switch S5A (rear) clockwise until contact

emitter followers. Input voltage of +27.5 volt

19 is at an open segment of the switch. This

dc is applied through terminal 19 to the voltage

removes the ground on megahertz select line B

regulator. The voltage regulator, composed of

from pin 1 of relay K1. Simultaneously, how-

resistor R1 and Zener diodes CR2 and CR1, reg-

ever, ground from megahertz select ambiguity

ulates the voltage at +18.2 volts dc. The +18.2-

line B is applied, through contacts 12 and 19 of

volt dc output from the voltage regulator is

switch S5B (front), contacts 18 and 20 of

applied to the junction of resistors R2 and R27,

switch S5C (front), terminal 9 of the motor con-

the collectors of transistors Q4 and Q5, and

trol unit, and diode CR5, to pin 1 of relay K1,

resistor R24. From the junction of resistors R2

keeping the relay energized. Motor B1 con-

and R27, +18.2 volts dc routes through resistor

tinues to turn switch S5 until contact 19 of

R2 to the base and collector circuits of transis-

switch S5A (rear) and contact 18 of switch S5C

tor Q1. Resistor R27 connects +18.2 volts dc to

(front) are at open segments of the switch. The

the base and collector circuits of transistor Q2

open segments remove ground from relay K1,

and Q3 and the base circuit of emitter follower

deenergizing K1; this removes +27.5 volts dc

Q4. An audio signal applied to HEADSET jack

from motor B1, stopping the motor. Mechani-

J9 routes through terminal 5 and capacitor Cl

cally connected to switch S5 and motor B1 is

to the base of transistor Q1. (Resistor R26

the frequency readout counter. As motor B1

serves as a load for the headset connected to

runs, the whole-megacycle dial on the frequency

jack J9.) Transistor Q1 amplifies the audio

readout counter rotates. When motor B1 stops,

signal to a level determined by the setting of

the frequency indicated on the whole-

gain adjust potentiometer R6. The amplified

megahertz dial is the whole-megahertz fre-

audio signal is then routed through capacitor

quency selected.

C3 to the base of transistor Q2. Transistor Q2

c. Operation of .05 Megahertz Readout Circuit.

amplifies the audio signal and routes it through

The code for .05 megahertz is a ground on the

c a p a c i t o r C7 to the base of transistor Q3.

.05 megahertz select line B. This ground is

Capacitor C9 couples the amplified audio signal

applied from . 0 5 megahertz select line B,

from the collector of transistor Q3 to the base

through contacts 19 and 1 of switch S4A (rear)

of emitter follower Q4. From the emitter of

and terminal 3 of the motor control unit, to pin

transistor Q4, the audio signal is routed through

1 of relay K2. Relay K2 energizes; this applies

t e r m i n a l 56 to switch S10, and through

+27.5 volts dc, through pins 3 and 8 of relay K2

capacitor C11 and terminal 7 to switch S9. The

and terminal 8 of the motor control unit, to

audio signal applied to switch S10 is routed

motor B2. Motor B2 turns switch S4A (rear)

through terminal 55, resistor R21, and capacitor

clockwise until contact 19 reaches an open seg-

C12 to the base of emitter follower Q5. Capacitor

ment of switch S4A (rear). When contact 19 of

C14 couples the audio signal from the emitter

switch S4A (rear) reaches the open switch seg-

o f transistor Q5 through terminal 78 to

ment, ground is removed from pin 1 of relay K2.

HEADSET jack J9. An audio signal applied to

Relay K2 deenergizes, removing +27.5 volts dc

the VOL control is routed, through switch S11,

from motor B2, which stops the motor. The .05

terminal 54, resistor R22, and capacitor C13, to

megahertz dial of the frequency readout

the base of emitter follower Q5. From the emit-

counter is mechanically connected to motor B2

ter of transistor Q5, the audio signal is coupled

and switch S4. When motor B2 stops, the fre-

t h r o u g h capacitor C14 and terminal 78 to

quency indicated on the .05 megahertz dial is

HEADSET jack J9.

the frequency selected.

1-13. Simulator-Test Set SM-349/ARC-54

d. Frequency Coding. For any frequency

Audio Amplifier A1

selected, the sequence of operation is as

(fig. FO-8)

described in b and c above. Refer to paragraph

located in

the

1-10d for the coding of .05 megahertz select lines

The

audio

amplifier

A through E. Paragraph 1-10f contains the cod-

SM-349/ARC-54 is the same as the one located

in the test set, with the following exceptions:

ing for megahertz select lines A through E and

megahertz select ambiguity lines A and B.

a. Audio from emitter follow Q4 is applied

1-14