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.
(5) Set the instrument, refer to TM5-6675-250-
(7) Energize the system in the BIAS mode and
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
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
rotating the upper band clamp
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
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.
(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).
Loosen the four upper band clamp mounting
4 - 8 , Change 1