TM 11-6125-249-34
Table 3-1. Direct Support Troubleshooting
NOTE
All checks are to be conducted with the inverter connected for normal use,
Corrective action
Probable cause
Malfunction
a. Check dc fuse or circuit breaker.
a. Blown fuse or circuit breaker in dc line.
Inverter fails to start
(1) Clean and tighten fuse contacts.
Replace Mown fuse.
(2) Reset circuit breaker.
b. If circuit breakers or fuses are blown, in-
b. Short circuit in dc line.
spect wiring between fuses or circuit.
breakers and the inverter. Repair or
replace as necessary.
c. Check wiring and input cconnection for
c. Open circuit in dc line.
open circuit. Repair or replace as neces-
sary.
d. Check for weak or broken brush holders,
d. DC brushes not making contact with com-
springs, and for sticking, worn or broken
mutator.
brushes. Replace as in paragraph 3-8.
e. Remove fan cover and try to turn ar-
e. Armature jammed.
mature assembly by hand. Check for
obstructions in airgap. If jammed, refer
inverter to higher category mainte-
nance.
a. Check exterior wiring and connections for
a. Ac circuit open.
Inverter starts, but delivers no output
open circuit. Repair or replace as neces-
voltage,
sary.
b. Check for weak or broken brush holders,
b. Ac contact brushes not making contact
springs, and for sticking, worn, or
with sliprings.
broken brushes. Clean, or replace as in
c. Remove ac end cover and air duct plate
C.
(46, fig. 4-7) and use multimetcr to
citer winding.
check resistance between the Sliprings.
Resistance must be 2.99 ohms 10
percent. If the multi meter indicates
much higher or zero resistance, refer in-
verter to higher category maintenance.
d. Replace regulator card assembly as in
d. Regulator failure.
bly to higher category maintenance.
a. Check dc voltage at power supply and cor-
a. DC input voltage low.
Output voltage is low.
rect.
b. Readjust voltage potentiometer as in TM
b. Voltage potentiometer out of adjustment.
11-6125-240-12.
c. Replace regulator card assembly as in
c. Regulator failure.
sembly to higher category maintenance.
a Check dc voltage at power supply and cor-
a. Input voltage higher than 30V.
Output voltage is high.
rect.
b. Readjust voltage potentiometer as in in TM
b. Voltage potentiometer out of adjustment.
11-6125-240-12.
c. Regulator failure.
higher category maintenance.
d. Check armature for shorted coils. A thin
d. Shorted coil in dc armature windings.
strip of stell held over the armature core
will vibrate if a short exists. Refer in-
verter to higher category maintenance.
a. Check for loose connections in the in-
a. Loose connections.
Output voltage unstable.
verter, tighten as necessary
b. Remove fan cover, ac end cover and air
b. Poor commutation or poor brush contact
duct plate (46, fig. 4-7) and check condi-
at sliprings.
tion of commutator and sliprings. Check
brushes, brush holder and brush springs.
Replace if defective. Clean commutator
and sliprings with 000 paper.
3-3
