TM 11-6625-828-45
(6) Rotate the test set 360 MOD control in
(2) Set the test set MODULATION switch
a clockwise direction until the vacuum tube voltmeter
to OMNI and set the OMNI TRACK switch to 0. (3) Set
0
indicates the computed value of EAC. Check that the
the course checker COURSE "TO" switch to and set
7%M meter needle indicates exactly at the meter green
the EQUALIZE switch to READ COURSE ERROR.
line (30 %).
Check that the course checker DEGREES COURSE
(7) Set the test set MODULATION switch
ERROR meter indicates exactly 0 degrees. If reading is
to EXT and connect the vacuum tube voltmeter to the
not exactly 0 degrees, proceed as follows:
(a) Set the course checker EQUALIZE switch
set DEMOD receptacle.
to SET INPUT (RED LINE). Use a screwdriver to adjust
the course checker INPUT control as necessary to obtain
the test set MIC jack and adjust the 1,000-cycle tone to
a red line indica- tion on course checker DEGREES
produce a full scale reading on the %M meter. Rotate the
COURSE ERROR meter.
(b) Set the course checker EQUALIZE switch
test set 9960- MOD control fully counterclockwise.
to NOTE METER position and record the meter reading.
(9) Check that the RF meter indications
(c) Set the course checker EQUALIZE switch
do not change by more than the width of the meter
to 9960- and compare the meter reading with the reading
needle with modulation percentages as high as 60
recorded in (b) above. If the readings are not identical,
percent..
g. Limiters Test. Connect the oscilloscope to
use a screwdriver to adjust the course checker 9960-
control until the meter readings are identical.
the test set 9960- MOD control capacitor C109 (located
(d) Set the course checker EQUALIZE switch
on the underside of the chassis adjacent to terminal 1 of
to ADJUST PHASE-BAL and observe the position of the
Z103) and ground and proceed as follows:
meter needle. Use a screw- driver to adjust the course
(1) Set the test set MODULATION switch
checker PHASE control to remove one-half of the needle
to 9960- and rotate the 9960- MOD control as required
deviation from the 0 position on the meter.
to obtain a green line indication on the % M meter.
(e Set the course checker COURSE "TO"
(2) Observe the limiter output pattern on
switch to 180 and observe the position of the meter
the oscilloscope. The envelope should show no trace of
needle. Use a screwdriver to adjust the course checker
amplitude modulation with sweep frequencies of 15 or 30
BALANCE control to remove one-half of the needle
cycles. At high sweep frequency (approximately 2,000
deviation from the 0 position on the meter.
cycles) the wave- form must show equal flattening of the
(f) Repeat (d) and (e) above until the course
top and bottom peaks.
(3) Set the test set MODULATION control
checker DEGREES COURSE ERROR meter indicates 0
0
to 30- and adjust the 30- MOD control as required to
in both the and 180 positions of the course checker
obtain a green line indication on the % M meter. (4)
COURSE "TO" switch.
(g) Set the course checker EQUALIZE switch
control capacitor C116 (located on the underside of the
to READ COURSE ERROR and observe the position of
chassis adjacent to tube socket XV103) and ground.
the meter needle. If the meter does not indicate to 0, use
Observe the limiter output pattern. The waveform must
a screwdriver to adjust the test set variable resistor
appear essentially the same as that described in (2)
R138- (located on the underside of the chassis adjacent
above.
to capacitor C158) until the course checker DEGREES
h. 30- Phase Angle Test-Zero Phase Shift
COURSE ERROR meter indicates exactly 0.
(4) Set the test set OMNI TRACK switch
to 15 and set the course checker SELECTOR switch to
15 to measure the 15-degree angle of the test set.
NOTE
Check that the course checker DE- GREES COURSE
ERROR meter indicates 0 0.2 degree.
Allow the test set to warm up for at least
2 hours before proceeding with this test.
(1) Connect the course checker to the
test set DEMOD connector.
Change 1 53