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Page Title:
Section IV. POWER CONTROL CIRCUITS |
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|  TRC-68 is supplied -30 volts dc from
b. Transmit. On transmit, tr relay K601
Power Supply PP-1494/U through terminal
operates (para 82b) and contacts 12-20 of
Z of plug P1 and FL27. A negative volt-
relay K601 open. This removes the +125-
age is tapped off the parallel combination
volt dc supply to the 500-kc if. amplifier
of resistors R711, R712, and R717 in series
stages, V501 through V503, first audio
with R715 and applied to the if. avc gate
amplifier V504, and second receiver mixer
CR504. Resistor R711 controls the squelch
V303. Contacts 1 and 20 of relay K601 close
threshold adjustment.
and supply +125 volts dc to first trans-
mitter mixer V304, second transmitter
b. Approximately 6 volts negative bias
mixer V101, and the screen grid of trans-
is tapped off voltage divider resistors
mitter power amplifier V106. Resistor
R605, R619, R617, and R618, at the junc-
R616 and capacitor C1 lengthen the decay
tion of resistors R605 and R619, and ap-
time for the low B+, which reduces the
plied to the control grids of V805, V806,
transient produced by the change in cur-
V807, and V808 through the secondary of
rent through transformer T801 when the
T801 (fig. 14). The -30-volt bias supply
rt unit is switched from transmit to re-
also supplies energizing voltage to the
ceive. Tr relay contacts 7 and 16 of re-
carbon microphones. The cathode of de-
lay K601 close and short-circuit resistor
tector diode CR 501 is biased with +5.6
R602, which raises the plate voltage sup-
volts dc on receive, +70 volts dc on trans-
plied to third rf amplifier V104.
mit, and +45 volts dc when the frequency
selector is running. Transmitter power
amplifier V106 is protected by a fixed
bias applied to the control grid through
relay subunit terminal W of plug P602,
jack terminal W of J14, terminal T of
24 is supplied -30 volts dc volts from Dyna-
jack J1, terminal T of plug P101, resis-
motor DY-151/U through terminal M of
tors R109, R108, and coil L114.
jack J10. Receiver-Transmitter RT-441/
Section IV. POWER CONTROL CIRCUITS
it will not conduct when a negative
voltage is applied to the anode, the
equipment cannot be turned on when
Radio Set AN/VRC-24 is powered by a
the polarity of the battery voltage
26.4-volt dc vehicle battery connected to
is reversed.
the positive and negative terminals of
(2) When the POWER control (S701)
terminal board TB1703. The 26.4-volt
on the rt unit or POWER control
dc input is applied to Dynamotor DY-151/
(S1505) on the Radio Set Control
U, which supplies the operating voltages
C-1439/U is momentarily turned to
to the radio set and to the filament cir-
the ON position, contact 5 of power
cuits, through power relay K3.
relay K3 is grounded and power re-
a. POWER ON Control.
lay K3 is energized. Holding con-
(1) The negative terminal of terminal
tacts 2 and 3 of K3 close and com-
board TB1703 is grounded. The
plete a groundpath through resistor
positive terminal is connected
R2 to contact 5 of K3, so that when
through terminal 35 of TB1702 and
when the POWER control is re-
fuse F704 to contacts 1 and through
leased, relay K3 remains ener-
silicon rectifier CR1 to terminal
gized. Relay contacts 1 and 4 of K3
6 of relay K3. Silicon rectifier CR1
close to apply the +26.4 volts dc to
protects the equipment in case the
the dynamotor, the filament cir-
battery polarity is reversed; since
cuits, the dc case blower, the pilot
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