TM-5-4310-389-14
j.
Separate rotor from front housing.
1.
Remove retaining screws (10).
2.
Place the rotor/front housing assembly on a press, pushing rotor and front bearing (9) out of the front housing (8).
Use a bearing puller to remove front bearing from the rotor shaft. Lift bearing off the shaft.
3.
Check the rotor assembly for current draw or resistance.
CAUTION
Turn off dc power source before removing test leads to avoid arc damage to slip ring surfaces.
NOTE
Place test leads on edges of slip rings to avoid arcing on brush contact surfaces.
a)
Current draw in amperes at 700 to 80'F should be 3.2 to 3.7 amps.
b)
Resistance of windings in ohms at 700 to 80'F should be 4.0 to 4.7 ohm.
4.
Grounded slip ring or winding.
Using a 12-Vdc test lamp, multimeter, or 1 10-Vac test lamp, place one test lead on the rotor body and the other
on either slip ring. An open circuit should exist.
k.
Test rotor winding.
1.
Continuity. Use ohmmeter to check continuity, insulation, and resistance of the rotor winding.
2.
Rotor shaft and body. Inspect for a) stripped threads on shaft, b) worn key slot, c) worn bearing surface, d)
scuffed pole fingers, and e) worn or dry rear bearing. Replace rotor if any of the deficiencies are noted.
l.
Slip ring removal. This is only necessary if the slip rings are worn beyond reuse or if the rear bearing must be
replaced. Unsolder ends of rotor leads from slip ring terminals. Carefully unwind the ends of the rotor coil leads
from the slip ring terminals. Straighten rotor leads. Insert a No. 10 x 1-inch cap screw into the opening at the center
of the slip ring assembly. Position bearing puller (figure 4-66) and remove slip rings from rotor shaft. Slip ring
assembly will usually slide off shaft. Use care not to damage leads. Slip ring may be cleaned with a fine crocus
cloth.
4-94
