TM11-6125-256-34
DIRECT
SUPPORT
MAINTENANCE
INSTRUCTIONS
Section I. GENERAL
records are available the accumulated operational hours
3-1. Introduction
should be a multiple of the average weekly or monthly
The maintenance instructions in this and the following
aircraft hours and the number of weeks or months the
chapter supplement the organizational maintenance
motor-generator has been installed
procedures in TM 11-6125-256-20 The troubleshooting
which begins at the organizational level is carried to a
3-3. Tools and Equipment
higher level in Chapters 3 and 4
Tools and test equipment required for Direct Support
3-2. Maintenance Guidance
maintenance of the motor-generator are listed in section
The maintenance and overhaul schedule outlined steps a
III of appendix B (Maintenance Allocation) in TM
11-6125-256-20
through c should be followed Implementation of this
schedule will ensure a high degree of reliability and an
3-4. Organization of Troubleshooting
increase in effective motor-generator life
Procedures
a General The first step in servicing a defective
motor-generator is to sectionalize the fault The second
step is to trace the fault to a specific defective part Some
a Motor-generators that fail before 600 hours of
faults such as burned-out resistors, arcing brushes
service (recorded aircraft flight hours) should be sent to
burned electrical leads and shorted stator windings, can
general support maintenance if the failure is due to bad
often be located by sight smell or hearing Other faults
bearings or if a replacement 4B48-6-A voltage and
must be located as described below
frequency regulator assembly is not available and the
defective regulator assembly is repairable
b Sectionalization The motor-generator consists of
two major sections the electromechanical motor-
generator section and the electronic regulator section
The operational test of paragraph 3-5 used in
b Motor-generators that fail at any time due to one of
conjunction with the organizational troubleshooting
the following causes should be forwarded directly to the
table in TM 11-6125-256-20, will be helpful in
depot for repair
sectionalizing the fault
(1)
Defect in armature assembly
c Localization Repair and replacement of parts at
(2)
Defect in stator coils
Direct Support is limited to those functions and
(3)
Worn bearing liner in end bell
procedures specifically described in this chapter Use
(4)
Fragmented housing
troubleshooting tables 3-1 and 3-2 for fault localization
If this fails to correct the problem, or if symptoms not
mentioned in the troubleshooting tables are noted, higher
c In aircraft where the main and spare motor-
category maintenance is required
generator (if any) are of the same type install the spare in
the main position when the main motor-generator is
turned in for depot overhaul Operational hours of the
d Intermittent Trouble In making any test do not
spare motor-generator, if only occasional, should be
overlook the possibility of intermittent troubles If
disregarded However, inspection testing and routine
present this type of trouble may often be made to appear
maintenance of the spare motor-generator will be
by tapping or jarring the equipment In addition, check
performed periodically For main motor-generators
the external and internal wiring connections
presently in operation but for which no service time
