TM 11-6625-847-45
Item
No.
Indication
Probable trouble
Procedure
2
Amplitude of 1-usec
Defective AMPLITUDE con-
Replace defective potentiometer
pulse output does not
trol R3.
R3.
vary when potentiom-
eter R3 is rotated
from fully counter-
clockwise to fully
clockwise
3
Pulse width of 160-usec
Defective pulse WIDTH con-
Replace defective potentiometer
and 85-usec pulse
trol R2.
R2.
outputs does not vary
when potentiometer
R2 is rotated from
fully counterclock-
wise to fully clockwise.
4
Pulse width of 1-usec
Defective pulse WIDTH control
Replace defective potentiometer
pulse output does
R4.
R4.
not vary when poten-
tiometer R4 is rotated
from fully counter-
clockwise to fully
clockwise.
5
The AN/USK-140(0)
Elective output coupling ca-
Replace defective capacitor A1C7.
does not show 85-usec
pacitor A1C7.
pulse output at connec-
tor J3, but 150-usec
pulse output is ob-
servable at connector
J2.
6
The AN/USM-140(*)
Defective output coupling ca-
Replace defective capacitor A14.
does not show 160-
pacitor A1C6.
usec pulse output at
connector J2, but 85-
usec pulse output is
observable at con-
nector J3.
7
The 150-, 86-, and 1-
Defective pulse shaping cir-
a. Connect test equipment as
usec pulse outputs at
cuitry (transistors Q1 and Q2).
described in paragraph
connectors J2, J3,
2-10. See figure 1-17 for
and J4 are not visible
waveshapes.
on the AN/USM-
140(*).
b. Connect the AN/USM-140(*)
probe to base of transistor
Q1, and adjust the AN/
USM-140(*) to show a
500 cps audio signal. If
signal is not present, check
capacitor A1C1, resistor
A1R1, and diode A1CR1
for defects. Replace
defective parts.
c. If audio signal is present at
base of transistor Q1, con-
nect the AN/USM-140(*)
probe to collector of tran-
sistor Q1 and adjust the
AN/USM-140(*) to show
2-11
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