TM10-3930-660-34 6-4.  STARTER - REPAIR (Cont’d) INSPECTION 1.   BRUSH COMPONENTS. a.  Check brush (19) lengths against length of new brush.  Brushes that are less than two-thirds the length of a new brush must be replaced. b.  An oil soaked brush must also be replaced. c.  Check to ensure that brushes fit well in holders (13 and 14), but without binding. d.  Inspect brush springs (15) for distortion or discoloration. CAUTION Do not turn down commutator nor undercut insulation between commutator bars. Replace armature if commutator cannot be restored satisfactorily in STEP 2, below. 2.   CHECK CONDITION OF COMMUTATOR, AND CLEAN, IF NECESSARY, USING NO.  240 GRIT EMERY PAPER. 3.   CHECK FOR SHORT CIRCUITS IN ARMATURE USING A GROWLER AND STEEL STRIP. a.  Rotate armature in growler. b.  Hold steel strip (e.g., hacksaw blade) across armature slots as armature rotates.  Steel strip will vibrate as slot between shorted bars passes under steel strip. c.  If short circuit is detected, check for build up of copper dust or other conductive material between commutator bars. 6-14