TM 11-5895-846-14
Table 8-8. Alarm Monitor Power Supply, Troubleshooting Chart
Item of Check
Test Conditions
Normal Indications
Remarks
7.
-- Continued
limit circuit components.
See
power supply schematic, figure
8.
Overvoltage
a. On the test fixture turn off the
protection.
POWER LINE CIRCUIT BKR.
Disconnect power connector P1
from connector J1 on the UUT
b. On the test fixture place the LOAD
switches to the N.L. position.
c. Connect the test equipment power
DMM to the + 24 V VOLTAGE
T.P. (plus to + 24 V and minus to
GND). On the test power supply
rotate the output control fully
CCW (minimum). Ap ply power
to the test power supply.
d. Reconnect power connector P1 to
connector J1 on the UUT. On the
text fixture turn on the POWER
LINE CIRCUIT BKR.
e. Observe the DMM and slowly in-
+ 24 V:30 V max.
If any voltage indication
crease the output of the test power
exceeds the max limit,
supply until the UUT crowbars.
check the over-voltage
At this instant note the highest
circuits: + 24 V: Q2,
voltage indication on the DMM
VR2; + 15 V: Q4, VR4;
before the voltage drops off then
-15 V; Q3, VR3; and
decrease the test supply output to
+5 V: Q6, VR6. Also
minimum. Turn off and discon-
check the common crow-
nect the test power supply.
bar SCR Q7 and associated
See power supply
f.
Repeat the preceding test (steps a
+ 5 V: + 6.25 V max.
through e) for each voltage by
+ 15 V: + 18.75 V max.
connecting the test power supply
- 15 V: - 18.75 V max.
to the +5V, +15 V, and -15 V
VOLTAGE T.P. (step c) Re-
verse polarity connections of the
test power supply when testing
the - 15 V output.
g.
Reset the POWER LINE CIRCUIT
BKR before preceding to the next
item of check.
9.
Current limiting.
a.
On the test fixture place the LOAD
switches to the F.L. position.
Place the CURRENT LIMITING
+ 24 V ADJ. and + 15 V ADJ. con-
trols fully CCW and + 24 V and
+ 15 V switches to the OFF
position.
b.
Observe the DMM connected to the
PWR. LINE test points and adjust
for 115 0.5 Vac on the DMM.
c.
Connect the second DMM to the
+ 24 V VOLTAGE T.P. and the
clip-on milliammeter to the + 24 V
CURRENT T.P. jumper (observe
clip-on polarity).
d.
On the test fixture place the LOAD
+24 V switch to the N.L. position.
8-20