Figure 3-27.--Inverting amplifier diagram.

Servo amplifiers

Dither oscillator

Error circuit

Gyro alarm circuits

Gyro signal card

Source light failure detector

Power distribution circuits

Gyro Demodulator

The gyro demodulator is a nonrepairable item. The

gyro demodulator receives 115-volts ac, 400-Hz

reference signals from stator leads S1 and S3 of the pitch

and roll synchros in the gyro. The demodulator converts

the ac synchro signals to dc with the in-phase ac signal

positive and the out-of-phase signal being negative. This

type of demodulator is called a phase-sensitive rectifier.

For an in-phase signal, the device behaves as a bridge

rectifier with a capacitor falter to remove ripple.

Figure 3-27.--Inverting amplifier diagram.

The internal gyro synchros that feed the demod-

ulator are excited with 26 volts ac, 400 Hz and have a

maximum output between S1 and S3 of 11.8 volts ac at

its input resistor and the feedback resistor with the inputs

90 rotation. When the signals are demodulated by the

added.

gyro demodulator, the output is 10 volts dc at 90 of

No voltage greater than 15 volts should be applied

rotation from horizontal.

to any pin of an op-amp or damage will result. The

op-amps output is short-circuit protected; thus, shorting

Linear Voltage Differential Transformer

the op-amps outputs will not damage them. Op-amps

exhibit three common types of failures: no output,

The LVDT is an ac electromechanical transducer

saturated positive, and saturated negative. A saturated

that converts physical motion into an output voltage

voltage is one that is maximum for a particular op-amp

whose amplitude and phase are proportional to position.

usually greater than 11 volts. Any op-amp whose output

In operation, an ac excited primary winding is

is greater than 11 volts and does not change with varying

coupled to two secondary windings by a moveable core

inputs may be defective. Check for large inputs and open

placed between them (fig. 3-28). Displacement of the

feedback resistors before replacing the op-amp.

SYSTEM ELECTRONICS

The GSI system electronics is divided into 13

fictional areas as follows:

Gyro demodulator

LVDT

LVDT demodulator card

LVDT oscillator

Figure 3-28.--LVDT aimplified schematic

LVDT demodulator

3-19