TM 11-6125-240-34
Table 3-1. Direct Support Troubleshooting -- continued
Corrective action
Malfunction
Probable cause
c. Open or shorted windings in ac stator
c. Refer inverter to higher category mainte-
nance.
coils.
a. Frequency potentiometer out of adjust-
a. Readjust frequency potentiometer as in
Output frequency incorrect.
ment.
b. Refer inverter to higher category mainte-
b. Open or short in dc stator coil.
nance.
a. Check brushes, brush springs and holders.
a. Brushes stuck in holder.
Excessive sparking at brushes.
Replace if defective. Clean brush
holders.
b. Remove fan cover, ac end cover, and air
b. Commutator or sliprings dirty or pitted.
duct plate (46, fig. 4-7) and check condi-
tion of commutator or sliprings. If dirty
or pitted, refer inverter to higher
category maintenance.
c. Check input current; if it is more than 190
c. Grounded circuit in armature coils.
amperes, a short cicuit is present.
Refer inverter to higher category main-
tenance.
a. Check for adequate air circulation around
a Poor external ventilation.
Inverter overbeats.
unit. Correct as necessary.
b. Poor internal ventilation,
b. Check to see that air louvers are free of
obstructions. Correct as necessary.
c. Feel bearing housings in ac and dc endbell
Faulty bearings.
c.
assemblies. If hot to the touch, refer in-
verter to higher category maintenance.
d. Check and comet as necessary.
d. Excessive load.
e. Remove fan cover and inspect fan for
e. Defective fan.
broken or bent blades. Refer inverter `o
higher category maintenance, if defec-
tive.
a. Check mounting bolts and other bolts and
a. Inverter or associated hardware not
Excessive noise.
firmly mounted.
screws; tighten as necessary.
b. Worn bearings.
b. Remove fan cover and rotate armature
counterclockwise by hand; feed and
listen for roughness in bearings. If any
is detected refer inverter to higher
category maintenance.
c. Remove fan cover and rotate armature
c. Armature dragging or striking on
counterclockwise by hand; feel and
polepiece.
listen for indications of interference. If
interference is evident, referinverter to
higher category maintenance.
d. Refer inverter to higher category mainte-
d. Shorted armature coil.
nance.
Refer inverter to higher category mainte-
Defective radio interference filter FL1.
Interference in aircraft's radio system.
nance.
Check conditons of test point jacks and inter-
Test point jacks or wiring defective.
Output voltage and frequency cannot be
nal wiring for open or shorted circuits.
measured at test point jacks.
Refer inverter to higher category mainte-
nance.
Section Ill. DIRECT SUPPORT MAINTENANCE OF PU-545/A
3-7. Cleaning
b. Remove loose carbon dust and dirt from the in-
Cleaning of the exterior of the inverter is carried out
terior with a stream of dry, low-pressure compressed
primarily at the organizational category. If such clean-
air.
ing is necessary, the procedures in TM 11-6125-240-12
c. Replace ac end cover and fan cover.
should be applied. In addition, clean the interior of the
3-8. Replacement of Brushes
generator section as follows
Both ac and dc contact brushes are replaced at direct
and two screws and regulator housing bracket from fan
support as described below. The inverter must be
cover and remove cover.
removed from the aircraft for brush replacement.
3-4
