TM
11-5820-921-40-1
I
TRANSISTOR
SIGNAL AND LOCATION
CONDITION
CHANNEL
CONDITION
1A5Q7
1A5Q10 SERVO IN A(P1-1)
A
1A5Q4
1A5Q8
1A5Q9
+19 VDC THRU Q10
OFF
ON
OFF
OFF
ON
B
1A5Q6
1A5Q11
1A5Q12
1A5Q13
1A5Q14 SERVO IN B (P1-5)
OFF
ON
GND THRU Q14
OFF
ON
OFF
L
I
TRANSISTOR
SIGNAL AND LOCATION
CONDITION
CONDITION
CHANNEL
I
1A5Q8
1A5Q10 SERVO IN A(P1-1)
A
1A5Q4
1A5Q7
1A5Q9
I
OFF
ON
GND THRU Q10
OFF
ON
OFF
1A5Q6
1A5Q14 SERVO IN B (P1-5)
B
1A5Q11
1A5Q12
1A5Q13
+19 VDC THRUQ14
OFF
OFF
ON
OFF
ON
2-103. In the final fine tune portion of the TUNE CYCLE, the direction and speed of rotation of torque
motor 1A8A3B1, are controlled by the closed servo loop consisting of torque motor 1A8A3B1, variable
coil 1A8A5LI, rotor contact, tune detector 1Al0, and servo amplifier 1A5. In the closed loop mode of
operation, the polarity and magnitude of the motor drive signals (and thus the direction and speed of
rotation) at the outputs (SERVO IN A and SERVO IN B) of the servo amplifier depend on the polarity
and magnitude of the TUNE SENSE input signals (PHASE ERROR A and PHASE ERROR B at pins 21
and 23 of 1A5P1, respectively). The two dc outputs from the phase detector are applied to the inputs of
differential amplifier 1A5AR1-1 whose output is applied to differential amplifiers 1A5AR1-2 and
1A5AR2-1. The inverted output of differential amplifier 1A5AR2-1 is applied to the input of differential
amplifier 1A5AR2-2. 1A5AR1 and AR2 control the separate servo channels, one for each motor lead,
which ground or apply the +19 Vdc to the inputs of torque motor 1A8A3B1, as required for proper
direction of motor rotation. The outputs of amplifiers 1A5AR1-2 and 1A5AR2-2 are square waves,
whose duty cycle is controlled by oscillator 1A5Q15 and amplifier 1A5Q16. The output of differential
amplifier 1A5AR1-2 is connected to the common base inputs of transistors 1A5Q7 and 1A5Q8. In a
similar manner, the output of amplifier 1A5AR2-2 is connected to the common base inputs of transistors
1A5Q11 and 1A5Q12. When the error signal (PHASE ERROR A) from pulse detector 1A10 is large
enough and of the proper polarity, amplifier 1A5AR1-2 applies a positive-going (+10V) square wave
signal to transistors 1A5Q7 and 1A5Q8. On the positive cycle, transistor 1A5Q7 conducts, applying
+19 Vdc to the base of transistor 1A5Q9. This causes 1A5Q9 to conduct, applying +19 Vdc to torque
motor 1A8A3B1. On the negative cycle, transistor 1A5Q8 conducts, applying a ground to the base of
transistor 1A5Q10. This causes 1A5Q10 to conduct, applying a ground to torque motor 1A8A3B 1. This
action produces a series of pulses, the duration of which is directly proportional to the amplitude of the
input error signal. This results in torque motor 1A8A3B1 being driven by a series of pulses, with longer
pulses for faster tuning when the error is great and shorter pulses for slower motor positioning as the
proper tune point is approached and the error signal is reduced, If the SERVO ENABLE signal
