TM 11-6625-847-45
Item
No.
Indication
Probable trouble
Procedure
measurement of transistor
stage Q3 as indicated in
chart (para 2-14b). If
gain of transistor Q3 is
not 3.2, check transistors
Q3 and Q2, resistors R6
through R11, and capacitors
C3, C6, and C7 for defects.
Replace defective parts.
b. Defective if. amplifier stage
b. Connect test equipment as
(transistor Q6).
shown in figure 6-20.
Make stage gain measure-
ments of transistor stage
Q6. If gain is not 3, check
transistors Q5 and Q6,
resistors R24 through R30,
transformers T1 and T2,
and capacitors C9, C15,
C19, C20, and C21 for
defects. Replace defective
parts.
3
Output level is not in-
a. Defective if. amplifier ages
a. Check transistor stages QS
dicated on the AN/
(transistors Q3 or Q6).
and Q6 as indicated in item
URM-145.
No. 2 above. Replace de
festive parts.
b. Defective 20-volt dc filter
b. Connect the ME-26(*)/U
circuit
across capacitor C5, and
check for an indication of
+20 volts dc. If +20 volt s
dc is not indicated, check
capacitors C5 and C4,
and inductor L2 for defects.
Replace defective parts.
2-23. Troubleshooting Chart, Troy A1A3 (Amplifier Modules AR1 through AR5)
Note. Refer to paragraph 2-15 before using chart.
Item
No.
Indication
Probable trouble
Procedure
1
The AN/URM-115 does
Defective amplifier module
Check switch for physical dam-
not indicate output
switch S1.
age. Using the AN/PSM-6B,
level of the AN/
check continuity between ter-
GRM-50 when am-
minals 3 and 6 of switch S1.
plifier module switch
Replace defective switch S1 and
S1 is set to OFF.
any defective wiring.
2
Amplifier output level
Defective potentiometer R1
With no power or signal in-
indication on the
puts to the amplifier module
AN/URM-145 does
under test, connect the AN/
not vary when poten-
PSM-6B between terminals
tiometer R1 is varied
E5 and E6 (fig. 4-7). Rotate
from fully counter
potentiometer R1 from fully
clockwise to fully
counterclockwise to fully
clockwise.
clockwise, and check for a re-
sistance variation of from 0 to
approximately 500 ohms. Re-
place potentiometer R1 if
defective.
2-18
Previous Page
