Upper Band Clamp Adjustment

TM 5-6675-250-34

screws enough so that the clamp can be rotated with

the caging mechanism cover with twelve (12)

t h e adjustment tool.

m o u n t i n g screws prepared as in (para 2-10a).

(6) Place the TEST SELECT switch to the

( 4 ) Install the cage-uncage knob.

BIAS position.

(5) Set the instrument, refer to TM5-6675-250-

(7) Energize the system in the BIAS mode and

and

see

that

the

pendulum

can

biased

u n c a g e the pendulum.

repeatably. This test will verify that the pendulum is

(8) Depress PRESS TEST and observe that the

free.

T E S T METER pointer comes to rest after swinging

4-7. Upper Band Clamp Adjustment (fig. 4-5).

l e f t and right several times.

a. Adjust. Adjustment of the upper band clamp is

( 9 ) While depressing PRESS TO TEST switch,

necessary when the bias control reaches its limit in

move the meter pointer to zero by rotating the upper

positioning the test meter needle to (O) during the

band clamp. Moving the meter pointer to zero from

b i a s i n g operation. The adjustment procedure shall

the left side of the meter requires clockwise rotation

be as follows:

o f the upper band clamp, and moving the pointer

(1) Set the instrument up as for operation, refer

towards (O) from the right side of the meter requires

to TM5-6675-250-12, being sure that the GRU is

clockwise.

rotating the upper band clamp

level.

M o v i n g the upper band clamp is best accomplished

( 2 ) Remove the theodolite (para 4-2).

by tapping the end of the setting tool with a

CAUTION

s c r e w d r i v e r handle or similar object.

Store the theodolite on a soft clean surface

(10) When the meter pointer is on (O), release

so as not to damage the theodolite mounting

the PRESS TO TEST switch.

pads.

(11) With the PRESS TO TEST switch

(3) Install the upper band clamp adjusting tool,

r e l e a s e d , the gain to the meter is increased and

using the two- 4-40 by 3/8-inch attachment screws.

f u r t h e r adjustment will probably be necessary.

(4) Loosen the bias control lock and rotate the

(12) Continue to tap the setting tool to rotate

bias control to the extreme clockwise position, then

the upper band clamp in small increments until the

r o t a t e the bias control 5 turns counterclockwise.

meter pointer shows on scale. There is no reason to

T h i s sets the bias control at mid range and the

adjust for a perfect (O) adjustment; on scale is

pendulum biasing current to (O).

adequate.

(5)

Loosen the four upper band clamp mounting

4 - 8 , Change 1