Section VI
Paragraphs 6-41 to 6-44
and coil (2) with the MICROVOLTS dial set to its max-
VOLTS dial set at 1000. (Use GS output connector. )
Adjust R1544 (figure 6-12) on the univerter to dupli-
imum output position. This clearance will normally
be 1/32 to 3/64 inch. If the loop touches L1508 at any
cate the avc reading noted above.
point, insert a small screwdriver through the hole and
very carefully bend the loop until it centers properly.
i. Check the univerter output as follows to insure
Repeat steps in paragraph 6-40 above.
that the response is sufficiently flat from 329.3 to
335.0 mc. Set SG-13/ARN MEGACYCLES control to
329.3 and MICROVOLTS dial to 1000. Feed the output
into an AN/ARN-18 receiver through Adapter UG-
NOTE
528/U and note the receiver avc reading. Substitute
SG-2 for SG-13/ARN and duplicate the avc reading by
U s e a non-metallic screwdriver to adjust
adjusting the SG-2 output. The SG-2 output should be
L1522 and all variable capacitors located in
within 15 percent of 500 microvolt. Make similar
the univerter.
comparisons at 331.1, 332.0, 332.9 and 335.0 mc.
If the 15 percent requirement is not met, readjust
a. Install the univerter cover and all r-f covers be-
C1583 and/or C1587 slightly to correct any peaks or
f o r e alignment. Be sure the covers are properly
dips in the response and repeat the entire procedure
seated and screws tightened securely.
out lined in paragraphs h and i above.
b. Set NAV-GS switch on GS, MEGACYCLES dial on
332.0, and connect the GS output to the input jack of
justments must be made with the r-f covers on and all
cover screws securely tightened. Set the SG-13/ARN
an AN/ARN- 18 glide slope receiver through a 53-ohm
6-db pad (UG-528/U). See figure 5-2. Adjust METER
MICROVOLT: dial at 1000 and the NAV-GS switch in
ZERO and set carrier level to the redline on the meter,
the NAV position unless otherwise specified. -Adjust
for 21 volts line on the panel meter and allow 10 min-
c. Connect a d-c vacuum tube voltmeter between
utes warm-up period before making any adjustments.
L1530 and ground. (L1530 is accessible through the
Tighten locking nuts on controls as each adjustment is
hole in the univerter cover as shown in figure 6-11.
completed.
Make test connections by placing meter lead on any
part of the turns in the coil,) Tune L1522 (figure 6-12)
for a peak reading on the vacuum tube voltmeter.
a. Connect the vertical input of an oscilloscope to
d. Measure the receiver avc voltage with a d-c vac-
the AUDIO OUT connector located behind access plate
uum tube voltmeter and adjust the MICROVOLTS dial
on the front panel and set AUDIO SELECTOR to 30%
to a level just high enough to give a small avc voltage.
VAR
Adjust METER ZERO and set carrier to red
line. Connect a 60 cps power line frequency or an ac-
In cases of extreme misalignment, it may be neces-
curate frequency standard to the horizontal input of
sary to advance the setting of R1544 in a clockwise di-
rection to obtain an indication of avc voltage. Adjust
the oscilloscope.
C1571 and C1574 for maximum output as indicated by
b. Set the 30@ FREQUENCY control behind the ac-
the receiver avc voltage. See figure 6-12.
cess cover on the front panel to exactly 30 cps by ad-
e. Tune the overcoupled tuned circuits between the
justing until the proper Lissajous pattern is obtained.
mixer and the first amplifier as follows. Short any
This will be a double loop if the 60 cps power line fre-
two adjacent turns of L1527 together by inserting a
quency is used. Adjust until this double loop is sta-
small metallic screwdriver through the hole in the
tionary.
bottom cover of the univerter and tune C1577 for max-
c. Rotate AUDIO SELECTOR to 9960 FM position
imum avc voltage. (If the avc voltage falls too low
when the coil is shorted, increase the setting of the
and set 9960 FM DEV control for zero deviation. Ad-
MICROVOLTS dial. ) Then short L1526 and tune
just the 9960 FM FREQ control to a frequency of 9960
C1578. When tuning overcoupled circuits, it is al-
cps as measured at the AUDIO OUT connector with an
oscilloscope and accurately calibrated a-f oscillator
ways necessary to detune one side by shorting turns
using Lissajous patterns. These controls are located
to tune the other side properly.
on the potentiometer panel (figure 6-11). The oscilla-
g. In the same manner, short L1530 and tune C 1580,
tor is very stable and should seldom need resetting.
short L1529 and tune C1581, short L1532 and tune
If the frequency is lower than 9960 cps at all settings
of the 9960 FM FREQ control, remove the white-
C1583, and short L1531 and tune C1587.
orange jumper wire used to connect C1437 in parallel
h. Check the univerter output to make sure it ie uni-
with C1434. If the frequency is higher than 9960 cps
form within 15 percent over the frequency range
at all settings of the 9960 ,FM FREQ control, connect
329.3 to 335.0 mc. This can be done by checking Sig-
a jumper wire to place C1437 in parallel with C1434.
nal Generator SG-13/ARN against an SG-2 signal gen-
These capacitors are located on the underside of the
erator. Set the SG-2 MICROVOLTS dial at 500 and
potentiometer panel and accessible only when the panel
feed a 332-mc signal into an AN/ARN-13 glide slope
is pulled back. Points A and B (figure 6-14) show the
receiver through a 53-ohm 6-db pad (Adapter UG-
jumper connecting points.
528/U). See figure 5-2. Note the receiver avc volt-
age. Substitute SG-13/ARN for the SG-2, using the
d. Rotate AUDIO SELECTOR to 1000~ position and
same frequency setting and 6-db pad with the MICRO-
adjust 1000~ FREQUENCY control behind the access
