DIRECT SUPPORT MAINTENANCE INSTRUCTIONS
Section I. GENERAL
3 - 1 . Introduction
b. Inverters that fail at any time because of one of
the following, should be forwarded direct to depot
The maintenance instructions in this and the following
chapter supplement the organizational maintenance
(1) Defect in armature assembly.
procedures in TM 11-6125-240-12. The troubleshooting
(2) Defect in status coils.
which begins at the organizational level is carried to a
(3) Worn bearing liner in endbell.
higher level in these chapters.
(4) Fragmented housing.
3-2. Direct Support Maintenance Guidance
C. Turn in for depot overhaul, any inverter that vi-
The maintenance and overhaul schedule outlined below
brates excessively, overheats, is unusually noisy, or has
should be followed. Implementation of this schedule
a brush contact area on the commutator and/or slip
will insure a high degree of reliability and an increase
rings that exhibit serious grooving or pitting.
in effective inverter life.
d. In aircraft where the main and spare inverters
a. Inverters that fail before 600 hours of service
are the same type, install the spare in the main posi-
(recorded aircraft flight hours) should be sent to
tion when the main inverter is turned in for depot over-
general support maintenance if the failure is caused by
haul. Operational hours of the spare inverter, if only oc-
bad bearings, or if a replacement regulator card assem-
casional, should be disregarded. However, inspection,
bly is not available and the defective regulator card as-
testing, and routine maintenance of the spare inverter
sembly is repairable.
will be performed periodically. For main inverters pre-
sently in operation, but for which no service time
Repairable card assemblies are those coated
records are available, the accumulated operational
with clear polyurethane and numbered either
hours should be a multiple of the average weekly or
CSV2215-2, CSV2215-3, or 4B93-1-A. Non-
monthly aircraft hours and the number of weeks or
repairable card assemblies are coated with
months the inverter has been installed.
blue epoxy and numbered CSV1186-1.
3-3. Direct Support Tools and Equipment
If the inverter has not been modified (para
Tools and test equipment required for direct support
to handle all models
of the universal
maintenance of the inverter are listed in table 1 of ap-
regulator card assembly, a direct replacement
p e n d i x C (maintenance allocation) in TM
card must be used or return the inverter to
depot for modification.
S e c t i o n Il. DIRECT SUPPORT TROUBLESHOOTING
3-4. Organization of Procedures
tioned in the troubleshooting table are noted, higher
category maintenance is required.
a. General. The first step in servicing a defective in-
verter is to sectionalize the fault. The second step is to
d. Intermittent Trouble. When making any test, do
trace the fault to a specific defective part. Some faults,
not overlook the possibility of intermittent troubles. If
such as burned-out resistors, arcing brushes, burned
present, this type of trouble may often be made to ap-
electrical leads, and shorted stator windings can often
pear by tapping or jarring the equipment. In addition,
be located by sight, smell, or hearing. Other faults must
check the external and internal wiring connections.
be located as described below.
3-5. Operational Test
b. Sectionalization. The inverter consists of two ma-
a. General. The operational test may be performed
jor sections: the electromechanical motor-generator
while the inverter is part of an aircraft installation.
section and the electronic regulator section. The opera-
(Refer to the applicable aircraft manual.) If the in-
verter is determined to be the faulty unit, localize the
the organizational troubleshooting table in TM
11-6125-240-12, will be helpful in sectionalizing the
b. Power Requirements. Connect an external power
supply to the external power connector on the aircraft
c. Localization Repair and replacement of parts at
while making the operational test. (Refer to the ap-
direct support is limited to those functions and
plicable aircraft technical manual.) The power supply
procedures specifically described in this chapter. Use
must be capable of delivering 200 amperes at 27.5 volts
troubleshooting table 3-1 for fault localization. If this
fails to correct the problem, or if symptoms not men-