GYRO SYNC INDICATOR FAILS TO LIGHT WITHIN TWO MINUTES AFTER MODE SELECT SWITCH IS PLACED TO GC

TM 5-6675-250-34

Table 2-1. TroubleshootingContinued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

f. Loosen the BIAS control lock (fig. 2-53) and rotate the BIAS control (fig. 2-53) to the extreme

clockwise position, then rotate the BIAS control (5) turns counterclockwise. Thie sets the

BIAS control at mid range and the pendulum biasing current to zero (0).

g. Loosen the four upper band clamp mounting screws enough so that the clamp can be rotated

with the adjustment tool.

h. Place the TEST SELECT switch (fig. 2-53) to the BIAS position.

i. Energize the system in the BIAS mode and uncage the pendulum.

j. Depress the PRESS TO TEST switch (fig. 2-53) and observe that the TEST METER (fig. 2.

53) pointer comes to rest after swinging left and right several times.

k. While depressing the PRESS TO TEST switch (fig. 2-53), move the meter pointer to zero by

rotating the upper hand clamp. Moving the meter pointer to zero from the left side of the

meter requires clockwise rotation of the upper band clamp, and moving the pointer towards

zero (0) from the right side of the meter requires rotating the upper band clamp coun-

terclockwise. Moving the upper band clamp is best accomplished by tapping the end of the

setting tool with a screwdriver handle or similar object.

l. When tbe meter pointer is on zero (0), release the PRESS TO TEST switch.

m. With the PRESS TO TEST switch released, the gain to the meter is increased and further

adjustment will probably be necessary.

n. Continue to tap the setting tool to rotate the upper band clamp in small increments and the

meter pointer shows on scale. There is no reason to adjust for a perfect zero (0) adjustment; on

scale is adequate.

o. Tighten the four upper band clamp mounting screws and remove the upper band clamp ad-

justing tool.

p. With the BIAS control (fig. 2-53), set the test meter pointer to zero (0), then cage and uncage

several times while observing the BIAS stability. Tbe test meter pointer shall not drift more

than half way through the yellow hand.

q. Place the theodolite over the GRU housing and connect the electrical connector to terminal

(1A1J3).

CAUTION

Ensure that electrical wire slack is placed adjacent to the inner circular surface of this mounting plate prior to lowering

the theodolite.

r. Lower the theodolite to position on the mounting plate. Position the white strip on the

theodolite base so that it is adjacent to the yellow stripe on the theodolite mounting plate.

s. Secure the theodolite by installing three sockethead screws. Using a torque wrench

progressively tighten the screws in 10-inch pound increments to 30-inch pound torque.

8 . GYRO SYNC INDICATOR FAILS TO LIGHT WITHIN TWO MINUTES AFTER MODE SELECT SWITCH IS PLACED

TO GC.

Step 1. Inspect printed circuit board for evidence of damage or failed components.

a. Loosen the eight captive screws and lift the electronic control panel assembly from the case (fig. 2-54).

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