TM 11-5895-846-14
Table 8-8. Alarm Monitor Power Supply, Troubleshooting Chart
Item of Check
Test Conditions
Normal Indications
Remarks
9.
--Continued
Place the CURRENT LIMITING
+ 24 V switch to the up position.
e. Observe the DMM and clip-on mil-
0.625 to 0.750 A max.
If indication is normal,
liammeter. Slowly rotate the
proceed to step g. If
CURRENT LIMITING + 24 V ADJ.
indication is abnormal,
proceed to step f.
control CW until the voltage starts
to drop off and the current stops
NOTE If necessary,
increasing (starts limiting). Ob-
step c for disassembly proce-
serve the current indication.
dures required to make current
limiting adjustment.
f.
Rotate the CURRENT LIMITING
Check CR3, CR4, U1
+ 24 V ADJ. control fully CCW.
R21, and R4. See power
supply schematic,
control R21 CL to another position
and then repeat step e above.
Repeat steps e and f as neces-
sary, to obtain a normal indication
(step e). If a normal indi-
cation now can be obtained,
proceed to step g. If the indica-
tion is still abnormal, the current
see Remarks.
g. On the test fixture place the CUR-
RENT LIMITING + 24 V ADJ.
control fully CCW and the CUR-
RENT LIMITING + 24 V switch to
the OFF position. Place the LOAD
+ 24 V switch to the F.L. position.
h. Connect the second DMM to the
+ 15 V VOLTAGE T.P. and the
clip-on-milliammeter to the + 15 V
CURRENT T.P. jumper (observe
clip-on polarity).
i. On the test fixture place the LOAD
+ 15 V switch to the N.L. position.
Place the CURRENT LIMITING
+ 15 V switch to the up position.
j. Observe the DMM and clip-on mil-
0.625 to 0.750 A max.
If indication is normal,
liammeter. Slowly rotate the
this procedure is com-
CURRENT LIMITING + 15 V ADJ.
pleted. If indication is
control CW until the voltage starts
abnormal, proceed to
step k. (See note in
to drop off and the current stops
step 8e.)
increasing (starts limiting). Ob-
serve the current indication.
k. Rotate the CURRENT LIMITING
Check U2, R25, and R26.
+ 15 V ADJ control fully CCW
See power supply sche-
control R25 CL to another position
and then repeat step i above.
Repeat steps j and k as neces-
sary, to obtain a normal indication
(step i). If a normal indication
can now be obtained, this proce-
dure is completed. If the indica-
tion is still abnormal, the current
fault: see Remarks.
l. Turn OFF POWER LINE CIRCUIT
BKR switch and disconnect UUT
from test fixture.
8-21