Current regulator 3A5A8

TM 11-5820-695-35

third stage, 3A5HY4, 3A5A6 and 3A5A7 provides a gain

of R3 and CR2. Potentiometer R3 applies a fixed

voltage at the base of transistor Q1l to set the operating

of 4 dB (input 24 dBm, output 28 dBm). This stage is

similar in operation to stage 1. The output port of

point for the required bias current. The ,base-to-emitter

voltage of both Q1 and Q2 is essentially fixed at 0.7 vdc

3A5HY4 is a waveguide which has c directional detector

and the voltage drop across R2 in the emitter circuit of

circuit to provide a dc indication of the output signal

Q2 is constant. The current through R2 is also constant

level for metering and status indication. The output

and includes the current drawn by the impatt diode

signal (level +28 dBm, min.) is coupled to output flange

through E3 and Q3.

RF OUT through a short length of waveguide, W3. This

signal is coupled through bandpass filter A4 (fig. 2-31)

to diplexer 3A7HY1.

e. The RF output monitor signal DET OUT (fig. 5-

101) is connected to A8-E8. On A8 (fig. 5-102), the

c. Current regulator 3A5A8 (fig. 5-102) contains

signal at E8 is fed through R22 to E7 and to Pl-9.

three current regulators that provide the constant current

Potentiometer R22 is adjusted to set the normal level of

(high source impedance) bias supply required by the

the signal. Resistors R21 and R23 divide this signal to

impatt diodes. The constant bias current outputs at

provide the proper level at the test point PWR TP1. The

3A5A8E3, E4 and E5 are applied at bias "T" cavities

+100 vdc input voltage is divided down by resistors R19

3A5A2 for diode 3A5A3CR1, at 3A5A5 for diode

and R20 to provide the signal at test point +100 vdc

3A5A6CR1 and at 3A5A7 for diode 3A5A6CR1

TP2.

respectively. The input voltage for 3A5A8 is 100 vdc

(regulated) applied at connector P1 pin 3 and pin 4 and

f. Heater 3A5HR1 (fig. 5-101) is connected to 120

3A5A8 terminals E1 and E2.

Vac at 3A5Pl-1 and -2; it is used to maintain a minimum

temperature in 3A5.

Thermostatic switch 3A5S1

d. In current regulator 3A5A8 (fig. 5-102) the +100

controls 3A5HR1.

Thermostat 3A5S1 opens at a

temperature of 30 5 and closes at 15 5 .

vdc input voltage at E1 is applied through a pi filter (L1,

Thermostatic switch S2 is located in another area of 3A5

C1, C2) to current regulator stages 1, 2 and 3 with

and acts as temperature monitor for the impatt diodes.

outputs at E3 (75 vdc, 105 ma., stage 1) E4 (75 vdc,

In the normal position S2-2 and -3 are connected

115 ma., stage 2) and E5 (75 vdc, 125 ma., stage 3).

together; the TEMP NORM signal at P1-7 is then +28

The three constant current regulator stages are identical

vdc. If the temperature rises above 210 40 , S2

in circuit and operation; the following description of

operates to connect S2-1 to S2-2. The TEMP ALM

circuit operation uses reference designations of stage 1.

signal at P1-8 is then +28 vdc. After a temperature

The output voltage from the pi filter is applied across a

alarm condition, the temperature must drop below 185

voltage divider; CR1, CR2, CR4, R3, R4 and R6

4 before 3A5S2 will reset to the normal position.

(ground).

Zener diode CR4 maintains a constant

voltage to ground at the junction

Change 6 2-136.1/(2-136.2 blank)