TM 11-6625-847-45
Item
No.
Indication
Probable trouble
Procedure
If positive 1-use pulses
are not present, check tran-
sistors Q7 and Q8, capaci-
tors A1C10 and A1C11,
and resistors A1R19, ARW20
A1R21, and A1R22 for
defects. Replace defective
parts.
d. Defective output coupling
d. Replace defective capacitor
capacitor A1C12.
A1C12.
9
The 150-usec and 85-
a. Defective squaring circuit.
a. Perform the following:
usec pulse outputs
(1) Connect test equip-
are not observable on
ment as described in
the AN/USM-140(*)
at connectors J2 and
(2) Connect the AN/USM-
J3; however, 1-usec
140(*) probe to
pulse output is ob-
collector of transis-
servable at connector
tor Q3, and adjust
J4.
the AN/USM-
140(*) to show 500-
cps positive trigger
pulses. If trigger
pulses are not pres-
ent, check diodes
A1CR2 and A1CR3,
resistors A14,
A1R6 and A1R6,
and capacitor A1C3
for defects. Replace
defective parts.
b. Defective monostable multi-
b. If positive trigger pulses
vibrator (transistors Q3
are present at collector of
and Q4).
transistor Q4 in a above,
connect the AN/USM-140(*)
probe to collector of tran-
sistor Q4 and adjust the
AN/U8M-140(*) to show
150-usec wide positive pulses
(control R2 rotated fully
clockwise). If 150-usec
pulses are not present,
check transistors Q3 and
Q4, capacitors A1C4 and
A1C5, and resistors A1R8
through A1R12 for defects.
Replace defective parts.
c. Defective output amplifier
c. If positive pulses are present at
circuit (transistor Q3).
collector of transistor Q4 in
b above, connect the AN/
USM-140(*) probe to
emitter of transistor Q5
and adjust the AN/USM-
140(*) to show 150-usec
negative pulses. If nega-
tive pulses are not present,
check transistor Q5, resis-
tors A1R15 and A1R14, and
2-13
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