TM 11-6625-847-45
Item
No.
Indication
Probable trouble
Procedure
b. Defective coupling capacitor
b. Replace defective capacitor
C5.
C5.
4
The selective frequency
Defective coupling capacitor
Replace defective capacitor C1.
voltmeter does not
C1.
indicate mixer output
level with the AN/
GRM40 connected to
connector J8 but in-
dicates a mixer out-
put level when the
AN/GRM60 is con-
nected to connector J4.
5
The frequency selective
Defective coupling capacitor C2.
Replace defective capacitor C2.
voltmeter does not
indicate mixer output
level with the AN/
GRM-50 connected
to connector J4 but
indicates an output
level when the AN/
GRM-60 is connected
to connector J8.
2-22. Troubleshooting Chart, If Amplifier Module A1, Common Module Tray A1A2
Note. Refer to paragraph 2-13 before using chart.
Item
No.
Indication
Probable trouble
Procedure
1
Output level indication
Defective APC attenuator cir-
a. Connect the ME-20 (*) /U
on the AN/URM-
cuit.
between the emitter of
145 does not change
transistor Q4 and ground,
when 10-kilohm po-
and check for a 0-volt in-
tentiometer A2R5 is
dication. If 0 volt is not
adjusted for maxi-
indicated, check diode CR9
mum output.
for defects.
b. If diode CR9 is not defective,
connect the ME-26(*)/U
between the collector of
transistor Q4 and ground.
Adjust 10K potentiom-
eter (fig. 6-8) A2-R5,
clockwise and then coun-
terclockwise; check to see
that resistance indication
increases and decreases as
the potentiometer is adjusted.
If no resistance variation
is observed, check transis-
tor Q4, resistors R16, R84,
and R28, capacitors C11,
C28, and C18, diode CR8,
and inductor L4 for de-
fects.
c. Replace defective parts.
2
Output gain of ampli-
a. Defective if. amplifier stage
a. Connect test equipment as
fier is below 20 0.5
(transistor Q3).
described In paragraph
db.
2-14. Make stage gain
2-17
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