TM 11-6625-828-45
(4) Remove the 20,000 ohm resistor installed
illustrated in A, figure 3-9 is obtained. The display
in place of resistor R143 (a above) and by the
illustrated in B, figure 3-9 is not an acceptable display.
substitution method, determine the resistance value of
(4)The resistance value of the decade resistance box
R143 required to obtain the smallest error as indicated
setting must be between 100,000 ohms and 1 megohm
on the course checker Permanently install R143 of the
when the acceptable display is obtained. If the setting is
determine value.
not within these limits, replace the 0.002-microfarad
(5) Repeat (1) through (4) above to rE check
capacitor of C123 with a 0.001- or 0.003-microfarad
the 0 and 15 track accuracy.
capacitance, and readjust the R149 decade resistance
(6) Set the test set OMNI TRACK switch to 0
box until the correct oscilloscope display is obtained.
and set the course checker SELECTOR switch to 0.
NOTE
(7) Vary the input line voltage to the test set
The phase of the 30-cycle output
from 105 volts to 125 volts and see that the DEGREES
from the signal generator must be
meter on the course checker does no vary more than a
adjusted properly (para 3-12) to
total of 0.20. Set the line volt age to 115 volts.
obtain the desired overlapping
3-13. 90- to 150-cycle Phase and AMP LOC
pattern illustrated in the display on
Alignment
a. Preliminary 90- -to 150-c,ycle Phase Adjustment.
(5) Set the test set MODULATION switch to
Replace each resistor, R146, R148, an R149 (fig. 2-3(2),
90- and rotate the 90- MOD control (variable resistor
with a decade resistance box set to reach 0.62
R130) fully clockwise. Check to see that the test set %
megaohm (mgo). Replace capacitor C123 (fig. 2-30)
M meter indicates at least 24 percent.
with a capacitor of 0.00 microfarad (Iff), and proceed as
(6) If the correct meter reading is not
follows: (1) Position the test set 90- MOD control in a
observed, readjust the decade resistance box,
75 percent clockwise rotation. Set the tee set 150- MOD
substituted for resistor R146, until the 24 percent
control to the center of its rang
indication is obtained.
(2) Use the vacuum tube voltmeter wit the test
(7) Set the test set MODULATION switch to
leads connected to the terminals of coil L103 (fig. 3-80)
150- and rotate the 150- MOD control (variable resistor
to be sure that the output c L103 is 14 volts -+0.01.
R144) fully clockwise. Check to see that the % M meter
Disconnect the vacuum tube voltmeter.
indicates at least 24 percent.
(3) Set the test set MODULATION switch to
(8) If the correct meter reading is not
90, and adjust the setting of the decade resistance box,
observed, readjust the decade resistance box,
substituted for resistor R146, until %M meter M102
substituted for resistor R148, until the 24 percent
indicates at the redline.
indication obtained.
(4) Set the test set MODULATION switch to
(9) Recheck the phase adjustments in (1)
150- and adjust the setting of the decade resistance box,
through (4) above. Note the values indicated on the
substituted for resistor R148, until % M meter M102
decade resistance boxes for resistors R146, R148, and
indicates at the redline.
R149. Disconnect the decade resistance boxes. Install
b. 90- to 150-cycle Phase Adjustment. Without
resistors R146, R148, and R149, with a resistance value
disturbing any of the above adjustments, set the test set
equal to that noted above. Solder capacitor C123 in
MODULATION switch to the AMP LO position and
place.
proceed as follows:
c. AMP LOC Level Adjustments. Connect the
(1) Apply a 30-cycle output from the sign<
vacuum tube voltmeter to the input connectors of the
generator to the X (horizontal) amplifier of the
filter unit and connect the filter unit output connector to
oscilloscope and connect the test set DEMO output to
the test set DEMOD connector. Place both the test set
the Y (vertical) amplifier of the oscilloscope.
MODULATION switch and the filter unit switch in the 30-
(2) Set the oscilloscope to external inpl and
cycle position, and proceed as follows:
adjust its controls for a full screen display TM 11- 662-
(1) Adjust the test set 30- MOD control
245
(3) Adjust the setting of the decade resistance
box, substituted for resistor R149, until the display
3-15
