TM 5-4310-227-15
(12) Clean the field windings with a clean
3/64 inch. Smooth the commutator
w i t h NO. 00 sandpaper and blow
c l o t h dampened with an approved
off particles with low-pressure, com-
cleaning solvent and dry thoroughly.
pressed air.
(13) Test the field windings for an open
(9) Use a growler to test the armature for
circuit with a test lamp circuit. Test
a short winding. Position the arma-
across the interconnection between the
ture on the growler and energize the
coils of the field windings. If the
growler. Hold a thin, steel strip paral-
lamp fails to light, resolder the inter-
lel to the core slots and explore the
connection. T e s t between the two
exposed surface of the armature core.
leads of the field windings. Failure of
A short-circuited coil in one of the
the lamp to light indicates an open
s l o t s , bridged by the jaws of the
circuit replaced.
growler, will cause the steel strip to
(14) Test the field winding for a grounded
vibrate when brought close to the oth-
circuit. Test between a lead of the
er slot occupied by the defective coil.
field windings and the field windings
Turn the armature in the growler one
frame. If the lamp lights, a grounded
slot at a time, continue to explore
condition exists and the defective field
with the steel strip until all coils have
winding must be replaced.
been tester. Replace a defective arma-
(15) Clean the commutator end head with
ture.
a clean cloth dampened with an ap-
Caution: In the following open and
proved cleaning s o l v e n t and dry
g r o u n d test do not touch the test
thoroughly.
probes to the shaft bearings surfaces
(16) Using a test lamp circuit, test between
or the commutator brush surfaces.
the insulated brush holder and the
(10) Test the armature for open circuits
commutator end head. If the lamp
with a growler. Position the armature
lights, the brush holder is grounded
on the growler and energize the grow-
and the commutator end head must be
ler. With the test probes connected to
replaced.
a n AC voltmeter, select a pair of
(17) T e s t between the grounded brush-
commutator bars which give a read-
holder and the commutator end head.
indication on the voltmeter.
able
If the lamp fails to light, the brush-
Maintaining this relation between the
holder is defective and the commu-
test probe position and the growler,
tator end head must be replaced.
turn the armature one slot at a time
until all coils are tested. The volt-
meter readings should be nearly uni-
cordance with figure 4-4 reversing the numeri-
form. If the armature has been proved
cal sequence.
free of shorts (see above), a low of
zero reading indicates an open cir-
cuit. Replace a defective armature.
a. Removal and Installation. Remove and in-
(11) Test the armature for grounds with a
stall the generator (para 3-49).
test lamp circuit. T e s t between the
armature shaft or core and one of the
assemble the generator. Due to the method
commutator bars. Repeat the test at
of installing field coils and other components
two or more locations around the com-
in the frame and field of fungus resistant as-
mutator to preclude the possibility of
semblies, it is necessary to replace the frame
testing from an isolated bar. If the
and field assembly as a unit, if field coils are
lamps light, the armature is ground-
required.
ed. Replace a defective armature.
