TM 11-6625-847-45
A2A1A2 and A2A1A3, the output is the input of two-tone
output. The 54-volt ac is stepped-up by transformer
mixer assembly A2A1A5 (fig. 6-3).
winding 7-8, full-wave rectified by diodes A3CR5 through
A3CR8, regulated by 33-volt Zener diode A3VR1, filtered,
and applied to pin 14 of connector J2.
1-1 2. Mixer Assembly A1A5
resistors, capacitors, and inductors.
Note. Where partial reference designators are used,
prefix with test set and mixer assembly reference
1-1 1. IF Oscillator Circuit
designator A2A1A5, unless otherwise specified, for
example: A2A1A5 C1.
Note. Where partial reference designators are used,
The input from IF oscillators modules A2A1A2 and
prefix with test set reference designator AZ, and the
A2A1A3 are combined by the common tie point of
appropriate IF oscillator module presence designator
capacitors C1 and C2 and by diode CR1. Diode CR1 is
A1A2, A1A3, or A1A4, for example: A2A1A2.
utilized as a diode switch and controlled by the RCVR IF
AGC SYNC switch on tray A1A2. When the RCVR IF
AGC SYNC switch is set to ON, +20-volt dc is supplied to
a. The function of the IF oscillator circuitry is to
the anode of diode CR1 through resistor R5, forward-
provide either a two-tone or single-tone IF frequency to
biasing the diode into conduction. When diode CR1 is
connector A2J1 on the test set. The IF oscillator circuit
forward based, the input signals at J3 and J4 are coupled
consists of three crystal-controlled oscillators modules
to AMPLITUDE control resistor R1 through diode CR1
A2A1A2, A2A1A3, and A2A1A4 and two-tone selector
and capacitor C5. Resistor R1 is used to control the
switch A2A1S8. The two-tone selector switch selects the
output level of the mixer assembly. Placing the RCVR IF
output of the IF oscillator circuit by switching the + 20-vk
AGC SYNC switch on tray A1A2 to OFF removes the
dc B + supply voltage to the oscillator module selected,
forward-bias from diode CR1, disconnecting the input
energizing the oscillator. Oscillator module A2A1A4,
signals from J3 and J4 from J2 and OUT connector J5,
when selected, provides a 1.7500-mc output to test set
and forward-biasing diode CR2 into conduction. When
connector A2J1.
Oscillator modules A2A1A2 and
diode CR2 is forward-biased, the external if. signal
A2A1A3 provide 1.7525-mc and 1.7515-mc inputs,
connected to IN connector J1 of the mixer assembly is
respectively, to two-tone mixer assembly A2A1A5.
coupled as the output of the mixer assembly through
capacitor C3, diode CR2, and capacitor C4 to connector
J2 and OUT connector J5. Resistor R1 controls the
A2A1A4 are identical in operation and in circuitry with the
amplitude by shunting a portion of the input signal to
exception of the frequency of the crystals. Each oscillator
ground.
module contains a crystal controlled transistor oscillator
A1Q1 and a buffer amplifier A1Q2.
Oscillation of
1-13.
SERV SEL Switch
transistor A1Q1 is sustained by coupling the in-phase
signal from the emitter of A1Q1 through resistor A1R7
and capacitor A1C1 to the base of A1Q1. A positive
Note. Prefix reference designators with test set reference
output trigger from the crystal-driven tank circuit
designator A2, unless otherwise specified.
consisting of capacitors all, A1C2, and diode A1CR1 is
coupled to the base of A1Q1 through diode A1CR2 and
a. The +27-volt dc applied to pins A and B of
A1C4 to frequency-stabilize the OSCILLATOR The -input
POWER connector A1J1 is applied through the ON
of oscillator A1Q1 is the input at the base of buffer
position of POWER switch A1S2; through 10 AMP fuse
amplifier A1Q2. Variable resistor A1R1 in the emitter of
A1F1; to contact 1 of switch A1S1, section A, front; to
A1Q2 controls the output amplitude of the buffer amplifier
indicator A1DS1; and through switch S1 to fan motors
at output jack J1 for module A2A1A4. For modules
Change 1
1-11
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