(1) Clean the armature and field wind-
ings of any dirt or magnetized particles. To
remove grease and oil, apply a light coat of a
safety type petroleum solvent such as MIL-
T-6003, with a brush. Wipe clean, then use
compressed air to remove any remaining dirt
film. Do not use any degreasing compounds
or submerge the armature in a degreasing
tank as this would damage the insulation.
(2) Clean the commutator with 00 sand-
paper and remove sand particles with com-
(3) Clean the commutator end frame,
(5) Inspect brush plate for cracks and
and components with an approved solvent
loose rivets. Inspect insulated brush holders
and dry thoroughly.
(6) Inspect brush springs for tension
and signs of breaks or other damage. Replace
f . Inspection and Repair
(1) Inspect the commutator for rough-
(7) Inspect the ball bearings for smooth
ness, high mica, loose winding, burrs, or pits.
operation. Inspect for excessive side play and
Smooth the commutator with 00 sandpaper or
undercut on a lathe. Replace the armature if
the commutator bars are less than 1/16-inch
breaks, cracks, and damaged threads.
thick after undercut. Undercut the mica be-
tween the bars to a depth of 1/32-inch.
(9) Inspect all hardware for damaged
Caution. Do not widen commutator
slots by removing metal from bars when un-
(1) Inspect for windings grounded to
dercutting. Use only solder with a rosin core
of the tester to the armature shaft and the
(2) Inspect the armature shaft for wear,
other to each commutator riser. An indication
pita, bends, corrosion, or breaks.
(3) Place the armature ends in V-blocks
and measure the commutator for out-of-round
with a dial indicator. Turn down if in excess
(2) Inspect for open windings with a
of 0.001-inch out-of-round.
test lamp. Touch the probes to a pair of ad-
(4) Inspect end frames for cracks and
jacent commutator risers. Failure of the lamp
damaged or worn bearing surfaces.
to light indicates an open winding.