TM 11-6625-828-45
ZERO SET control. The meter needle will hi the lower
(2) Adjust the test set ATTENUATOR uV
stop pin for about 2 seconds., Hold the control in until the
control until the ac voltmeter indicates 300 microvolts.
needle returns to the vicinity of the ZERO SET line on
(3) If required, loosen the ATTENUATOR TV dial on its
the S%M mete scale. Adjust the control to align the
shaft and rotate the dial until the dial indicates 300
needle c the 7%M meter with the ZERO SET line on the
microvolts. Tighten the dial on its shaft.
meter scale.
(4) Using a 1/16-inch Bristol wrench, back off
the two setscrews securing the ATTENUATOR uV
3-10. RF unit Alignment
control dial on its shaft and rotate the ATTENUATOR tV
a. RF Tuning. Capacitors C143A, C149A, an
control fully clockwise until the dial indicates 10K. The
C143B, C149B peak the oscillator output for the A- and
setscrews are located on the bore of the knob portion of
B-frequencies, respectively. The capacitors are located
the dial and are 120 apart.
on the front panel adjacent t the MC switch and are
(5) Be careful not to disturb the attenuator
marked: PLATE A, X (C143A, LB) and GRID A, B
control setting, back off locknut H128 (fig. 3-6), and
(C149A, B). Se the MC switch to A. Adjust the RF
adjust stop screw H126 until the end of the screw
LEVEL SET control as required. With a small-screw
contacts the top of attenuator assembly A107. Tighten
driver, adjust the PLATE A capacitor and GRI] A grid in
the locknut.
turn for maximum RF meter indication. Repeat the
3-11. Modulation Meter Alignment
adjustment until both capacitor are peaked. Set the MC
Recheck the ZERO SET meter indications as specified
switch to B and similarly adjust the PLATE B and GRID B
in paragraph 3-9 and proceed as follows:
capacitor for maximum RF meter indication.
a. Set the test set MODULATION switch to 30- and
CAUTION
turn the 30- MOD control fully counterclockwise.
Do not apply undue pressure to the
b. Set the MC switch to B.
capacitors or damage and false
c. Adjust the RF LEVEL SET control until RF meter
settings may result.
M101 indicates at the LEVEL SET redline.
b. RF Output Alignment.
d. Connect the dc voltmeter between terminal 3
(1) Remove the termination cap from the RF
(green wire with red trace) of RF unit Z104 (fig. 3-5) and
OUTPUT-1 VOLT connector and connect a external 51-
the negative terminal of RF meter M101. Connect the
ohm termination to the connector.
vacuum tube voltmeter across the dc voltmeter.
(2) Connect the ac voltmeter across the
e. Use a small screwdriver to adjust the PLATE B
external 51-ohm termination.
trimmer capacitor on the front panel of the test set, as
(3) Adjust the RF LEVEL SET control until 1.0
required, to obtain the maximum detuning effect
volt is indicated on the voltmeter.
(minimum RF meter indication). Record the voltage
(4) Adjust RF meter sensitivity variable
indicated by the dc ,voltmeter as Eo.
resistor R212 (fig. 2-3 (1)) until RF mete M101 indicates
f. Adjust PLATE B trimmer capacitor for maximum
at the LEVEL SET redline.. If the range of R212 is
RF meter indication, and reset the RF meter to the
insufficient, reorientate L-115 in RF unit Z104 (fig. 3-5)
LEVEL SET redline. Record the voltage indicated by the
and readjust the output level to 1.0 volt.
dc voltmeter as E.
(5) Remove the external 51-ohm termination
g. Compute EAC from the following formula:
and replace the 51-ohm termination car The RF meter
EAC = 0.212 (E, + 3 - Eo).
needle should return to the SE! LEVEL redline within
h. Adjust the test set 30- MOD control until the
1/32 inch.
vacuum tube voltmeter indicates a reading equal to the
c. RF attenuator Alignment. Connect the test set
computed value of EAC.
RF OUTPUT ATTEN connector to the a voltmeter 50-
ohm input connector, and proceed as follows:
(1) Adjust the test set RF LEVEL SE: control
until RF meter M101 indicates at the LEVEL SET redline.
3-12
