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Page Title:
Isolating Trouble Within Modules A3 and A4 |
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|  procedure given in (9) above should
(1) BAND switch at 30-52.
be 1,100 kc.
(2) Tuning knobs for 30.00 mc.
(3) Function switch at ON.
(12) Change the receiver-transmitter
e. Alignnment Procedures.
BAND switch to 53-75.
(1) Connect the 411A between pins 1
(13) Adjust the AN/URM-48 frequency
and 4 of A2J1.
to 53.000 mc as indicated by the
(2) Adjust the output of the AN/URM-
AN/USM-26.
48 for 30.00 mc and a 25-millivolt
(14) Repeat the procedures given in (1)
indication on the 411A.
through (9) above. The input-to-
(3) Disconnect the 411A from pins 1
output voltage ratio noted in (3)
and 4 of A2J1 and connect it be-
above should be +1 db; the 3-db
tween pins 2 and 3 of A2J1.
bandwidth computed in the proce-
(4) Tune transformer T1 for a peak
dure given in (9) above should be
voltage indication on the 411A.
3,300 kc.
(5) Set the receiver-transmitter tun-
(15) Adjust the AN/URM-48 frequency
ing knobs at 52.95 mc, and adjust
to 75.950 mc as indicated by the
the AN/URM-48 to 52.95 mc.
AN/USM-26.
(6) Tune capacitor C1 for a peak volt-
(16) Repeat the procedures given in (1)
age indication on the 411A.
through (9) above. The input-to-
(7) Repeat the procedures given in (1)
output voltage ratio noted in (3)
through (6) above until the 411A
above should be -0.5 db; the 3-db
indication for 30.00 mc and 52.95
bandwidth computed in the proce-
mc can no longer be increased by
dure given in (9) above should be
tuning.
15,000 kc.
(8) Set the receiver-transmitter front
(17) If the bandwidth or the input-to-
panel controls as follows:
output voltage ratio does not meet
(a) BAND switch at 53-75.
the given standards, proceed to c
(b) Tuning knobs at 53.00 mc.
below.
(9) Repeat the procedures given (1),
c. Faulty Parts Isolation.
(2), and (3) above, except change
(1) Adjust the AN/URM-48 for a 25-
the frequency noted in (2) above
millivolt rf signal at the frequen-
to 52.95 mc.
cies indicated in the chart below
and measure the voltages at the
(10) T u n e t r a n s f o r m e r T 2 f o r a
switch terminals listed. Compare
peak voltage indication on the
them with the nor ma 1 signals
411A.
listed.
(11) Set the receiver-transmitter tun-
ing knobs at 75.95 mc, and adjust
Note: Measure all voltages to ground.
the AN/URM-48 frequency to 75.95
mc.
(12) Tune capacitor C2 for a peak volt-
age indication on the 411A.
(13) Repeat the procedures given in (9)
through (12) above until the 411A
indication for 53.00 mc and 75.95
mc cannot be increased by
tuning.
(2) After replacing a faulty part, per-
form the alignment procedures
given in d and e below and then re-
peat the procedures given in a and
A3 and A4
b above.
d. Preparation for Alignment. Set the
Because modules A3 and A4 are similar,
their maintenance procedures are similar.
receiver-transmitter front panel controls
Refer to figures 1 and 2 for schematic
as follows:
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