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Page Title:
Isolating Trouble in Module A14 |
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|  (a) Signal voltage chart.
a. Preparation.
(1) Prepare the following equipment:
(b) Dc voltage chart.
(d) Oscilloscope AN/USM-50A.
(e) Multimeter ME-26B/U.
(i) Module extender.
(2) Remove module A9.
( 3 ) Turn the receiver-transmitter
function switch to ON.
b. VFO InPut Test.
(3) After the replacement of a faulty
(1) Connect the AN/URM-48 between
part, perform the alignment pro-
pin 1 of J2 (receptacle for A9) and
cedure outlined in e and f below
chassis ground. Connect the 411A
and repeat the procedures given in
across the AN/URM-48 output.
a, b, and c above. Replace module
(2) Adjust the AN/URM-48 frequency
A9.
to 53 mc and set the level to 10
e. Prepration for Alignment.
millivolts, as indicated by the
(1) Set the receiver-transmitter front
411A.
panel controls as follows:
(3) Disconnect the 411A from the AN/
(a) BAND switch at 30-52.
URM-48 and connect it between
(b) Tuning knobs to 30.50 mc.
A14J2 and chassis ground.
(c) Function switch at ON.
(4) Slowly vary the AN/URM-48 fre-
(2) Remove module A9.
quency from 41 to 65 mc while ob-
f. Alignment Procedures.
serving the 411A.
(1) Connect the AN/URM-48 between
(5) The 411A should indicate 25 milli-
pin 1 of J6 (receptacle for A9) and
volts 2 db throughout the 41- to
chassis ground. Connect the 411A
65-mc tuned range.
across the AN/URM-48 output.
(2) Adjust the AN/URM-48 frequency
c. 1-Mc Input Test.
(1) Connect the AN/USM-26 between
to 52 mc and the level to 3 milli-
A14J3 and ground. The frequency
volts, as indicated by the 411A.
meter should indicate 1 mc 25
(3) Disconnect the 411A from the AN/
Cps .
URM-48 and connect it between
(2) Connect the AN/USM-50A between
A18J2 and chassis ground.
A14J3 and ground. The AN/USM-
(4) Record the voltage level at A18J2
50A should indicate 1.5 volts peak-
as indicated by the 411A.
to-peak.
(5) Adjust the AN/URM-48 frequency
to 54 mc (maintain the output level
d. Faulty Parts Isolation.
at 3 millivolts).
(1) Insert the module extender into the
(6) Record the voltage level at A18J2
A14 connector and insert A14 into
as indicated by the 411A.
the module extender. Remove the
(7) Compare the indications obtained
cover from A14.
in the procedures given in (4) and
(2) Apply a 53-mc, 0.01-volt signal
(6) above. If the indications are
between pin A of A14J1 and chassis
equal to each other, alignment of
ground. Measure the voltages at
A14 is accurate. If the indications
the points listed below. Compare
are not equal to each other, pro-
them with the normal signal and dc
ceed to (8) below.
voltages listed.
(8) Repeat the procedures given in (1)
Note: Measure all voltages to ground.
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