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Page Title:
Alignment of 3.0- to 3.9-Mc If. Subunit |
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|  serted, the circuit is tuned above
132. Alignment of 3.0- to 3.9-Mc If. Subunit
resonance and requires adjust-
a. Test Equipment Required.
ment. If the indication increases
(1) Rf Signal Generator Set AN/URM-
when the brass tip is inserted, the
25D.
tuned circuit is below resonance
(2) Multimeter ME-26/U.
and requires adjustment.
(3) Alignment tool.
Tune L401, L403, and L405, if nec-
(8)
(4) Tuning wand.
essary, for a maximum indication
b. Test Setup.
of the ME-26/U.
(1) Perform the alignment test setup
(9)
Set the MANUAL FREQUENCY
TENTHS control to .9. Set the AN/
(2) Connect the output of the AN/URM-
URM-25D frequency to 3.9 mc.
25D to test point J303 (fig. 62).
Check L401, L403, and L405 with
(10)
(3) Set ME-26/U to the -3-volt dc
the tuning wand ((7) above).
range and connect the dc probe to
Tune LA02, L404, and L406, if nec-
(11)
test point J504 (fig. 59).
essary, for a maximum indication
c. Procedure.
of the ME-26/U.
(1) Set the MANUAL FREQUENCY
Repeat (4) through (11) above until
(12)
TENTHS control to .9.
no further increase in the ME-26/U
voltage indication can be obtained.
Note. Perform procedures (2) and (3)
Operate the MANUAL FRE-
(13)
below only when this subunit has been
QUENCY TENTHS control from
severely misaligned.
.9 to .0 and tune the AN/URM-25D
(2) Adjust the slugs of L402, L404,
in corresponding 0.1-mc decre-
ments from 3.9 to 3.0 mc. Check
and L406 (fig. 56) counterclock-
wise to their stops; then turn three
the tuning of L401, L403, and L405
complete turns clockwise.
with the tuning wand. Only slight
(3) Adjust slugs of L401, L403, and
detuning (if any) should be noted
L405 (fig. 56) so that the tops of
in the middle of the .9- to .0-mc
range. If considerable detuning is
the slugs are 1-3/32 inches from
noted, check the tuning slugs for
the top of the cover.
proper travel. T h e s l u g s s h o u l d
(4) Set the MANUAL FREQUENCY
move linearly for given increments
TENTHS control to .0.
(5) Set the AN/URM-25D frequency to
of rotation. Replace any worn or
3.0 mc unmodulated and adjust the
broken parts, or replace coil L401,
output level for a readable indica-
L403, or L405 (para 110).
tion on the ME-26/U.
Note. In the following procedure, adjust
the AN/URM-25D output level as neces-
a. Test Equipment and Tools Required.
s a r y to keep the ME-26/U indication
(1) Rf Signal Generator Set AN/URM-
between -1 and -2 volts do. This will
25D.
prevent the avc voltage from affecting
(2) Signal Generator TS-497/URR.
alignment.
(3) Multimeter ME-26/U.
(4) Alignment tool.
(6) Check L401, L403, and L405 with
(5) Tuning wand.
the tuning wand ((7) below).
(7) If the meter indication shows a de-
b. Test Setup.
crease when either the brass or the
(1) Perform the alignment test setup
iron tip of the tuning wand is in-
serted into the coil form, the tuned
(2) Set the ME-26/U to -3-volt dc
circuit requires no further adjust-
range and connect the dc probe
ment. However, if the indication
to test point J504 (fig. 59).
increases when the iron tip is in-
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