TM 11-6625-847-45
Item
No.
Indication
Probable trouble
Procedure
3
When the AN/GRM-
a. Defective transistor a
a. Perform the following:
50 is adjusted for an
Q1.
(1) Connect test equip-
output of 50 mv (560
ment as described in
mv for module AR3
(fig. 6-15)) at 1 mega-
(2) Make stage gain mea-
cycle, the amplifier
surement for transistor
module output level
stage Q1 as indi-
indication on the AN/
cated in paragraph
URM-145 is substan-
2-16b.
tially below 100 mv
(3) If stage gain of tran-
(60 mv for module
sistor stage Q1 is
AR3).
abnormally below
16.9 (15.6 for
module AR3), check
transistor Q1, a
sistors R1 through
R5, and capacitors C2
and C4 for defer
Replace defective
parts.
b. Defective transistor stage
b. Perform the following:
Q2.
(1) Make stage gain mea-
surement of transistor
stage Q2 as indicated
(2) If stage gain of tran-
sistor stage Q2 is
abnormally below
0.74 (0.76 for module
AR3), check tran-
sistor Q2, resistors
R6 through R9,
and capacitors C3
and C5 for defects.
Replace defective
parts.
4
With potentiometer R1
a. Defective input or output
a. Check capacitors A1C2 and
set fully clockwise, the
coupling circuits.
A1C5 and resistors A1R1
AN/URM-145 does
and A1R9 for defects. Re-
not indicate amplifier
place defective parts.
output level.
b. Defective amplifier module
b. Replace defective switch
switch S1.
S1.
5
When frequency of the
Defective bandpass filter
Check inductor L1and capaci-
AN/GRM-50 is
tor C6 for defects. Replace
changed from 1 mc
defective parts.
to 7.1 mc, 10 mc, and
23.1 me, the output
level indication on
the AN/URM-145
changes substantially.
2-19
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