Specifications

of servo faults would include mechanical problems with the
servo or electrical problems with the motor, servo drive amp, or
power supply. This fault would not allow the transmitter to put
out power since the transmitter may not be at the proper tuning
point.
R.5.25
Tune Servo Position Sample
Two voltages are taken from the Tune Servo Assembly and used
in the servo control.
R.5.25.1 Tune Servo Position Feedback
A potentiometer is mechanically connected to the servo and
provides the position voltage.A resistor is in series with the wiper
that makes the output voltage non-linear, such that it tracks
circuit Q.
R.5.25.2 Tune Servo Motor Current Feedback
A lowvalueshunt resistor is connected from the motor to ground.
The voltage across the shunt will be very small and change in
polarity, depending upon the motor direction.
R.5.25.3 Tune Servo Low Pass Summing Amplifier
Both sample inputs are connected to a summing amplifier and
buffer U44. The output Load Position voltage at TP43 is con-
nected to the Servo Amplifier (+) input, the Tune Position Mul-
timeter at J19, and to the Tune Servo Fault Detector.
R.5.25.4 Tune Servo Differential Amplifier
Both the reference and position voltages are applied to inputs of
differential amplifier U44. If both inputs are equal, as theyshould
be, the output voltage will 0VDC. A resistive level shifter at the
output applies 7.5VDC to the window detector at TP48.
R.5.25.5 Tune Servo Window Detector
If the 2 voltages at the differential amplifier are not the same, the
input voltage to U43 will increase or decrease. If the voltage at
TP48 is greater than 8VDC or less than 7VDC, the comparator
output will go logic low and generate a Tune Fault at TP45. This
output is connected to the Tune REFERENCE COUNTER PAL
which will generate a Tune Servo Fault.
R.5.26
Load Servo Fault Detector
The Load Servo Fault Detector is the same as the Tune.
R.5.27
Efficiency Coil Board Interlocks
The Bit 0 and Bit 1 information loops through the interconnec-
tions for the 8 Efficiency Coil boards inside the respective
Figure R-4. Servo Encoder
R-8 888-2339-002
WARNING: Disconnect primary power prior to servicing.