Section II. FUNCTIONING OF TRANSMI=ITER RADIO T-1054(P)/GRC-144(V) AND T-1054(P)A/GRC-144(V) CIRCUITS

TM 11-5820-695-35

Section II. FUNCTIONING OF TRANSMI=ITER,

RADIO T-1054(P)/GRC-144(V) AND

T-1054(P)A/GRC-144(V) CIRCUITS

2-27.

General

sensed by Q9, which triggers Q1. When triggered, Q1

This section covers the functioning of circuits used in

short circuits the rectifier output causing the fuse in the

the T-1054(P)/GRC-144(V) and T-1054(P)A/GRC-

ac input supply to blow (this circuit is referred to as a

144(V).

The coverage is presented in sequential

crowbar configuration).

reference designation order and is at the schematic

diagram level.

Circuit functioning and schematic

(1) The base of differential amplifier stage Q8

diagrams are not provided for the non-repairable

is clamped to 3.3 volts above ground by reference diode

assemblies (i.e. coaxial circulator 1HY1, directional

CR6 and diode current limiter R11. The voltage at the

coupler 1DC1, etc.). Circuit descriptions for cabinet

base of Q7 is determined by a voltage divider consisting

mounted components (metering circuits, indicators,

of R5 and either R6 or R7. Variable resistor R6 or R7 is

radio patch panel, etc.) and the nonrepairable

connected through the chassis connector jumper to the

assemblies are covered in the block diagram description

power supply positive output lead (pin 13). Resistor R6

for the T-1054(P)/GRC-144(V) (para 2-1 through 2-18).

is used to adjust the output to 5 vdc and resistor R7 is

All cabinet mounted circuits and all interconnections in

used to adjust the output to 6 vdc. Emitter resistor R9

the T-1054(P)/GRC-144(V) are shown in figure 5-15.

maintains a constant emitter current which is determined

(The T-1054(P)/CRC-144(P) circuits are shown in figure

by the reference voltage. Since R9 is the common

5-15.1). All references to the T-1054(P)/GRC-144(V)

emitter resistor to both stages Q7 and Q8, changes in

also apply to the T-1054(P)A/GRC-144(V) unless

the operating conditions in one stage interact with the

otherwise specified.

other stage. An increase of the Q7 base voltage above

3.3 volts causes the transistor to draw higher collector

2-28.

Power Supply 1A1 Circuit Functioning

current. An increase in Q7 collector current causes an

equal decrease in Q8 collector current. As a result, the-

Power supply 1A1 contains the voltage regulators

voltage across R8 increases. The voltage developed

(1A1A1 through 1A1A4 and 1A1A6 through 1A1A12)

across R8 is applied to the base of Q6 through base

which provide the dc supply and control voltages

current limiting resistor R4. Collector current in Q6

required in the T-1054/ GRC-144. Power supply chassis

increases raising the voltage across R3 and causing Q5

1A1A13 provides: (1) a connector for each voltage

to conduct more. Due to the increase In current, the

regulator, (2) an ac fuse at the input of each voltage

voltage across R2 rises and causes Q4 to conduct more.

regulator, and (3) a failure lamp and a test point at the

Since the current source for Q4 is through R1 and R16

output of each voltage regulator. Figure 5-17, power

the voltage at terminal 5 will decrease lowering the

supply 1A1 interconnecting diagram, shows the chassis

voltage at the base of Q2 and thereby decreasing its

mounted components and the voltage regulator

collector current. Transistor Q2 supplies base current to

connections. The circuit descriptions for the voltage

series regulator Q3, therefore, transistor drive is

regulators are provided in the following subparagraphs.

reduced which increases its collector to emitter voltage

drop. Thus, the voltage regulator output voltage is

5/6v Voltage Regulator 1A1A1 through

restored to the desired regulated level.

1A1A4 (fig. 2-9). The rectified dc voltage from bridge

rectifier CR1 through CR4 is filtered by capacitor C1 and

(2) An overvoltage condition is sensed by Q9.

applied to the collector of series regulator Q3. The

The emitter of Q9 is clamped 3.3 volts below the output

series regulator, controlled by differential amplifier Q7,

Voltage by reference diode CR8; resistor R15 limits the

Q8, in conjunction with amplifiers Q4, Q5, Q6 and driver

amplifier Q2, introduces a voltage drop which maintains

voltage regulation at the emitter output. An overvoltage

condition at the voltage regulator output terminal is

Change 6

2-54.1/(2-54.2 blank)