SELF TEST

TM 5-6675-250-34

the high-speed gear is energized through 2A2S1D-5.

(1) THEO ILLUM. With the MODE SELECT

The servo motor control circuit is activated through

switch 2A2S3 positioned t o THEO ILLUM,

a derived signal from transformer 2A2T1 and

unregulated B+ voltage is applied to THEO BRT

energized relay 2A1K1. With the servo motor

rheostat 2A2R1 through 2A2S3B-2. The voltage is

operating at high speed and rotating the follow-up

tapped from 2A2R1 to receptacle 2A2J3, through

assembly clockwise, a feedback signal from the

the interconnect cable W1 to 1A1P1 on the GRU. A

tachometer in the GRU is applied to the demodulator

wiring harness connects 1A1J1 through 1A1J3 to

through de-energized relay 2A1K2. From the

the theodolite lamp. Voltage to the HAND LAMP

demodulator, the signal is routed to the torquer coil.

switch 2A2S6 and receptacle 2A2J1 is applied

Current through the torquer coil is monitored by the

through 2A2S3C-2.

TEST METER when the PRESS TO TEST switch is

(2) SELF TEST. With the MODE SELECT

pressed.

switch 2A2S3 at position 3, SELF TEST, power is

(f) SERVO CCW. With the TEST

applied to all circuits of the system. Activation of

SELECT switch 2A2S1 positioned to SERVO CCW,

the circuits corresponds to the positioning of the

operation is the same as described in the preceding

T E S T SELECT switch 2A2S1. Each circuit

monitored in SELF TEST has its own calibration

paragraph except that voltage is distributed

network to ensure proper meter deflection when the

through 2A2S1A-6 and 2A2S1D-6 causing the di-

rection of rotation to be reversed. The theodolite ro-

equipment is operating correctly. With the exception

of the GYRO and SOURCE VOLTAGE positions,

tates in a counterclockwise direction when looking

satisfactory operation of circuits corresponding to

down on the GRU.

(g) BRAKE ON. With the TEST SELECT

the following switch positions is indicated by the

switch 2A2S1 positioned to BRAKE ON, relay

TEST METER pointer in the green band of the

2A2K1 is energized through 2A2S1D-7. Through

meter scale.

relay 2A2K1, dc current is applied to the high side of

(a) SOURCE VOLTAGE. With the TEST

the gyro motor. Pressing the PRESS TO TEST

SELECT switch 2A2S1 positioned to SOURCE

switch connects the TEST METER to the circuit

VOLTAGE, B+ voltage is applied to the PRESS

current limiting resistor to indicate the state of the

TO TEST switch 2A2S2 through 2A2S1C-1.

circuit.

Pressing the PRESS TO TEST switch routes the

(h) GYRO. With the TEST SELECT switch

signal to the TEST METER. The voltage is read out

2A2S1 positioned to GYRO, the circuit is monitored

on the voltage scale of the TEST METER.

through the output of the sync sensor. Through

(b) REG AC. With the TEST SELECT swith

2A2S1B-8 and 2A2S1C-8, a circuit to the TEST

2A2S1 positioned to REG AC, regulated 26 Vac

METER is completed when the PRESS TO TEST

from the ac supply is applied to the PRESS TO

switch is pressed. Satisfactory operation of the

TEST switch 2A2S2 through 2A2S1C-2. Pressing

circuit and gyro motor is indicated when the TEST

the PRESS TO TEST switch routes the signal to the

METER needle moves to the green area while the

TEST METER.

MODE SELECT switch is in GC and the SYNC

(c) REG DC. With the TEST SELECT

indicator is illuminated.

switch 2A2S1 positioned to REG DC, regulated 5, 9,

and 18 Vdc is applied through a summing junction

(3) BIAS. With the MODE SELECT switch

2A2S3 at position 3, BIAS, rotation of the BIAS con-

and 2A2S1C-3 to the PRESS TO TEST switch.

Pressing the PRESS TO TEST switch routes the

trol knob provides control of biasing through poten-

signal to the TEST METER.

tiometer 2A2R4. The biasing operation is performed

with the pendulum in the GRU uncaged. Feedback

(d) BIAS. In the BIAS mode 2A2S1 in pos-

signals from the GRU reflect error torques which

ition 4, relays 2A1K1 and 2A1K2 are energized. A

are balanced by the adjustment of potentiometer

simulated signal derived from transformer 2A2T1

2A2R4. Relay 2A1K2 is energized during biasing

through 2A1P6-E to 2A2S1A4 and back through

2A1P6-MM and the closed contacts of 2A1K1A to

operation to permit electronic damping of the pen-

dulum. Centering the meter pointer in the center of

amplifier 2A1A1. The output of 2A1A1 is then

routed via the closed contacts of 2A1K2A through

the scale is necessary to obtain a high degree of ac-

the demodulator. The output of the demodulator

curacy in the subsequent gyro-compassing opeation.

then routed to the GRU torquercoil via 2A1P5-E,

Following the biasing operation, it is necessary to

W1 and 1A1Ja. Current drawn from the torquer coil

cage the pendulum to permit the MODE SELECT

is monitored to provide an indication of the circuit

switch to be moved to the next position.

condition on the TEST METER.

(e) SERVO CW. With the TEST SELECT

switch 2A2S1 positioned in the SERVO CW mode,

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