TM 11-6625-847-45
Item
No.
Indication
Probable trouble
Procedure
through C4 for de-
fects. Replace de-
fective parts (fig.
b. If a 1.75-mc signal is present
Q1.
at base of transistor Q1 in
a above, connect the AN/
USM-140(*) probe to the
collector of transistor Q1
and adjust the AN/USM-
140(*) to show a 1.76-mc
signal. If signal is not pre-
ent, check translator Q1,
resistors R7, RB, and R10,
and capacitors C5, C6, and
C8 for defects. Replace
defective parts.
c. Defective buffer amplifier
c. If 1.75-mc signal is present
stage Q2.
in b above at collector of
transistor Q1, connect the
AN/USM-140(*) probe to
emitter of transistor Q2
and adjust the AN/USM-
140(*) to show a 1.76-
mc signal. If signal is not
present, check transistor
Q2 and potentiometer R1
for defects. Replace de-
fective parts.
d. Defective output coupling
d. Replace defective capacitor
capacitor C9.
C9.
2-21. Troubleshooting Chart, Test Set (Mixer Module A1A5)
Note. Refer to paragraph 2-12 before using chart.
Item
No.
Indication
Probable trouble
Procedure
1.
When the AN/GRM-
Defective potentiometer control
With no power or signal inputs
50 is connected to con-
R1.
to the mixer assembly, connect
nector J1, J2, J8, or
the AN/PSM-6B between
J4, the mixer output
connector J2 and ground.
at connector J6 does
Check the AN/PSM-6B for
not vary an potentiom-
resistance indication of 0 to
eter R1 is varied
1,000 ohms as potentiometer
from fully counter-
R1 is varied from fully coun-
clockwise to fully
terclockwise to fully clock-
clockwise.
wise. If the AN/PSM-6B
does not indicate a variable
resistance, replace potentiom-
eter R1.
2
When the AN/GRM-
a. Defective two-tone mixer
a. Perform the following:
50 is connected to
circuit (diode CR2 and
(1) With no power or
connector J1, the fre-
associated parts).
signal inputs to the
quency selective volt-
mixer assembly,
meter does not indi-
connect the AN/
cate mixer output
PSM-6B between
level.
terminals E1 and
2-15
Previous Page
