TM 11-5895-846-14
Table 8-8. Alarm Monitor Power Supply, Troubleshooting Chart
Item of Check
Test Conditions
Normal Indications
Remarks
3. Continued
or Q14), and the driver transistor
(Q9, -15 volt supply only). See
power supply schematic, figure
4.
Line and load reg-
ulation, full-load
output.
a. On the test fixture, place the LOAD
switches to the F. L position.
b. Observe the DMM connected to the
PWR. LINE test points and adjust
103.5 0.5 Vac on the DMM.
+ 24 0.24 V
c. Measure the dc output voltage with
If a supply voltage indica-
the second DMM at each VOLTAGE
+ 5 + 0.05V
tion is abnormal, make the
+ 15 0.15 V
T.P.
checks described under
- 15 0.15V
Remarks in item 3 above.
5.
Ripple voltage
a. On the test fixture, assure that the
full-load output.
LOAD switches -are in the F.L.
position.
b. Observe the DMM connected to the
PWR. LINE test points and adjust
103.5 0.5 Vac on the DMM.
C. Measure the ripple voltage.
+ 24 V:10 m V rms (max)
If any indication exceeds
Remove the DMM test leads and,
+ 15 V:10 m V rms (max)
the maximum limit,
in turn, connect the RMS volt-
- 15 V:10 m V rms (max)
check the appropriate
meter to each VOLTAGE T.P.
+5 V:10 m V rms (max)
supply for faulty filter
See power supply schematic,
6.
Transient recovery
a. On the test fixture, assure that the
at full-load
LOAD switches are in the F.L.
output.
position.
b. Observe the DMM connected to the
PWR. LINE test points and adjust
the variable transformer control
for 138 0.5 Vac on the DMM.
Maintain this voltage for one
minute and then reduce it to 115
0.5 Vac.
+ 24 0.24 V
c. Measure each dc output voltage.
If a supply voltage indica-
+5 0.05 V
tion is abnormal, make
+ 15 0.15 V
the checks described
- 15 0.15 V
under Remarks in item
3 above.
7.
Short circuit
a. On the test fixture, assure that the
recovery at full-
LOAD switches are in the F.L.
load output.
position.
b. Observe the DMM connected to the
PWR. LINE test points and adjust
the voltage transformer control
for 115 0.5 Vac on the DMM.
+ 24 0.24 V
c. Individually short each dc output to
If any output voltage fails
+ 5 0.05 V
ground at the VOLTAGE T.P.
to recover, check the
+ 15 0.15 V
Remove the short and then
current limit section
- 15 0.15 V
measure the voltage at the test
(pins 2 and 3) of the reg-
point using the second DMM to
ulator IC (U2) of the + 15
determine that the output has re-
volt supply. Check the
turned to normal.
associated regulator
transistor and current
8-19