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5-12 4. Inspect brush leads for cracks, wear, or fraying. If any of these conditions exist, replace with new brushes along with new brush springs as a set. 5. Inspect the rear cover bushing for wear. 6. Inspect the front cover bearing for wear. 7. Inspect the brass commutator end of the arma- ture for any discolored spots or damage. If the commutator is slightly discolored or damaged, the armature must be replaced. This is a molded commutator and no attempt to turn it down in a lathe should be attempted. 8. Inspect the commutator end of the armature for buildup in the grooves. Carefully remove any buildup by undercutting using a thinly ground hacksaw blade. Do not cut any deeper than the original groove which can be seen by looking at the end of the commutator. 9. Using a caliper, measure the undercut. Maxi- mum undercut groove must be 0.2 mm (0.008 in.). SNO2171 10. Inspect the commutator for shorting using a multimeter and the following procedure. A. Set the selector to the OHMS position. B. Touch the black lead to the armature shaft. C. Using the red tester lead, probe the commuta- tor end of the armature. The meter indicator should not change. If the indicator shows resistance, the armature is shorted and must be replaced. 11. Inspect the armature for shorting using a “growler” and the following procedure. A. Place the armature in the “growler.” B. While holding a metal strip on the armature, rotate the armature an entire revolution. If the metal strip vibrates at any point on the arma- ture, the armature is shorted and must be replaced. 0725-653 12. Inspect the ground brushes to make sure they are properly grounded. Use a multimeter and the following procedure. A. Set the selector to the OHMS position. B. Touch the black tester lead to a ground brush. C. Touch the red tester lead to the brush holder assembly. NOTE: If no resistance is indicated, check the ! CAUTION Do not use emery cloth to clean the commutator as ! CAUTION Buildup in the grooves must be removed to prevent |