TM 9-4940-549-14&P
(9) Test armature for short circuits as follows:
(a) Place armature on a growler fixture.
(b) Activate the fixture and slowly rotate the armature while
touching the armature lightly with a steel strip.
(c) Strip will vibrate against armature over a shorted area.
(d) Replace armature if a short is indicated.
(10) Turn down commutator if scored or out of round. Under cut
mica to a depth of 0.025 to 0.032 inch below surface of com
mutator.
NOTE
Check diameter of commutator after re-
moving material. Diameter shall not
be less than 1.6470 inches.
(11) Use an ohmmeter to check field coils for insulation breakdown
as follows:
(a) Attach one lead to field housing and the other to field coil
terminal.
(b) Replace field coil if a reading of less than 1 megohm is
indicated.
(12) Inspect drive assembly for badly worn or broken teeth. Check
internal spline for wear and damage. Check spring for cracks,
breaks, and distortion. Replace drive assembly if defective.
(13) Inspect brushholders and support for cracks, corrosion, and
other damage. Replace defective parts.
(14) Measure brush length.
Replace brushes if length is 5/16-inch
or less.
(15) Test brush spring tension with a spring tester. Tension shall
be 36 to 40 ounces. Replace brush springs if tension is less
than specified.
(16) Inspect all threaded parts for crossed, stripped, or peened
threads. Replace damaged parts.
(17) Using an ohmmeter, test for continuity across terminals of sole-
noid case and coil. There shall be no sign of open circuit.
(18 ) Check solenoid case and coil for grounding by touching one
lead of ohmmeter to either lead and the other to the frame cas-
ing. There shall be no sign of continuity.
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