CE- 1008
C. MODULATOR CIRCUIT BOARD See Figure 5-24)
(1) The modulator produces a square wave output signal whose amplitude is proportional to the magnitude of the
receiver AGC signal. It consists of two operational amplifiers, a 60-cps reference generator, and an output amplifier.
(2) The AGC signal is applied through pin 34 to operational amplifier A1. A 115-volt, 60-cps resolver reference
signal is applied through pins 2 and 6 to transformer T1. The output winding of T1 controls transistors Q2 and Q4 which
in turn switch Q1 and Q3 at a 400-cps rate. Thus the output of Al is a 60-cps square wave proportional to the AGC signal
in amplitude. This signal is further amplified by operational amplifier A2 and output amplifiers Q5 and Q6.
(3) PARTS LIST AND SCHEMATIC - The parts list for the modulator is contained in Table 5-15. The schematic
diagram is shown in Figure 5-24.
D. DEMODULATOR CIRCUIT BOARD (See Figure 5-25)
(1) The demodulator is a dual-purpose card. It provides a full-wave phase sensitive demodulator and an
operational amplifier for compensation. The demodulator consists of two transistor switches Q1 and Q2. Q1 and Q2
switch the inputs alternately to ground. Q1 and Q2 are caused to switch by the reference generator Q3 and Q4. Al is a
high gain operational amplifier which provides an integration. Amplifier current balance is provided by BAL control R10.
(2) PARTS LIST AND SCHEMATIC - The parts list for the demodulator is contained in Table 5-16.
The
schematic diagram is shown in Figure 5-25.
E. WRITING GUN RELAY DRIVER (See Figure 5-26)
(1) The writing gun relay driver controls operation of the scope writing gun so that a scope display will be present
only when a signal is being received. The circuit card consists of an operational amplifier, a transistorized relay driver
and a relay.
(2) The AGC signal from the receiver is applied to pin 3 and TP2. This signal is amplified by amplifier Al and,
when of sufficient magnitude, triggers relay driver Q1 to the ON condition. When Q1 is on, a ground path is completed
for the coil of relay K1 which is energized, applying +15V to pin 30 and enabling the writing gun in the scope to operate.
When K1 is deenergized, a ground is applied to pin 30 and the writing gun is disabled.
(3) ADJUSTMENTS - Set LEVEL control R8 so that relay K1 is energized at an AGC voltage just above zero
signal level. This control setting will vary
Revised January 22, 1968
5-61
Previous Page
