Centrifugal Fan HD-390/U

terminals A and L of AUDIO jacks

The low-voltage commutator drives two

high-voltage commutators which provide

J1502 and J1503 to input terminal

T of J1501. Because this terminal

operating voltages to the rt unit. The out-

is connected only to terminal L of

put of the +300-volt commutator is applied

AUXILIARY jack J1403 (fig. 34),

to terminal F of plug P1001. The electrical

no audio is available. However, this

noise from the 300 -volt commutator is fil-

switch position permits push-to-

tered by capacitor C1003 and filter

talk transmission on Receiver-

FL1003.

Transmitter RT-323/VRC-24 or

b. The output of the 170-volt commutator

is applied to terminals M and K of plug

RT-441/TRC-68.

(2) On the INT position, radio inter-

P1001. The load across terminals M and

phone switch S1504 prevents trans-

K functions as a voltage divider to ground.

mission or reception at control

The voltage from terminal K to ground is

C-1439/U. All audio circuits are

+140 volts dc and the voltage from terminal

connected through terminals R,

M to ground is -30 volts dc. The electrical

S, and T on jack J1501 to AUXIL-

noise from the 170 -volt commutator is

IARY jack J1403, terminals B, K

filtered by capacitor C1002 and filters

and L, (fig. 34) or terminals

FL1001 and FL1002. The voltage on ter-

TB1701-16 and -17 and terminal

minal K is filtered in the relay subunit

TB1702-20 (fig. 46).

(fig. 23). Under operating conditions, the

(3) On the RAD position, radio inter-

output voltage at terminal K drops to +125

phone switch S1504 functions as

volts dc.

c. Dynamotor DY-151/U also includes

described in c (3) above.

transmitter modulator blower B1003,

dynamotor and radio set blower B10002,

89. Centrifugal Fan HD-390/U

and transmitter power amplifier blower

(fig. 31)

B1001. These blowers supply forced air

Centrifugal Fan HD-390/U (part of the

cooling to the rt unit. Terminals A, B,

AN/TRC-68) consists of three blowers that

and D of plug P1001 are grounded and are

provide forced air cooling for the mod-

in the holding ground circuit to power re-

ulator and transmitter power amplifier

lay K3 (fig. 24). The rt unit will not remain

stages and circulate cooling air through the

on when POWER control switch S701 is

rt unit chassis. The blowers are driven by

released, unless dynamotor plug P1001

a single-phase ac induction motor, B1051,

is properly connected to jack J10.

which operates on 115 volts ac, 50/65 cps.

Capacitor C1051 provides starting torque

91. Case Blowers

for the motor. Input power is supplied

a. Receiver-Transmitter Case CY-2557

through terminals C and E of plug P1051.

VRC-24 and Blower B1401 (fig. 33). This

Plug terminals A and D are jumpered to

case contains a blower that circulates

provide a ground circuit to power supply

cooling air through the ducts between the

relay K1801 (fig. 25). Thus, the rt unit will

inner and outer walls of the case. The

not remain on when POWER control switch

blower is driven by series-wound dc motor

S701 is released, unless plug P1051 is

B1401, which operates from the storage

properly connected to jack J10 of the RT-

battery source, 26.4 volts dc. Input power

441/TRC-68.

is supplied through terminals A and B of

plug P1401, which mate with jack terminals

90. Dynamotor DY-151/U

A and B of jack J1702 on Mounting MT-

(fig. 32)

1436/U. Filter FL1401 isolates electrical

a. Dynamotor DY-151/U provides dc

noise from blower motor B1401 from the

main dc input supply.

plate, screen grid, and bias voltages for

Receiver-Transmitter RT-323/VRC-24.

b. Receiver-Transmitter

Case

CY-

The low-voltages commutator is driven

2712/TRC-68 and Blower (fig. 34). This

case contains a blower that circulates

from a 26.4-volt storage battery source.