11. Put the armature on a growler tester to check for a
shorted armature (Fig. 47). A burned commutator bar is
an indication of a shorted armature. With the growler
turned on, put a thin strip of steel or a hacksaw blade
on the armature as it is slowly rotated. If the metal strip
vibrates over a winding, that winding is short circuited.
Short circuited windings are sometimes caused by met-
al in the commutator bridging the gap from on commu-
tator bar to the next. By removing the bridged metal, this
condition can be corrected. If this does not correct the
short replace the armature.
12. Measure the commutator O.D. and depth of under-
cut.
Repair or replace if the service limit is exceeded.
Check the commutator outside surface for dirt and
roughness. If rough, polish the commutator with fine (00
or 000) sandpaper. DO NOT use emery cloth.
Item Standard Service Limit
Commutator O.D. 38.7 mm (1.52 in.) – 1.0 mm (– 0.4 in.)
Depth of Undercut 0.5 mm (0.02 in.) 0.2 mm (0.008 in.)
13. Check the brushes (Fig. 48). Replace if worn beyond
the service limit. Check the brush spring tension. Re-
place the springs if tension is less than the service limit.
Check for insulation between the positive brush holder
and holder base. If poorly insulated, replace the holder
assembly. Check the brush holders for proper staking.
Item Standard Service Limit
Height of Brush 17 mm (0.67 in.) 6 mm (0.24 in.)
Spring Pressure 3 kg (6.6 lb.)
14. Check for continuity between one end of field coil
(brush) and yoke (Fig. 49). There should be no continu-
ity. Check for continuity between both ends of coil
(brushes). There should be continuity if the field coil is
good. Check the poles and coil for tightness.
Figure 47
Figure 48
Figure 49
Reelmaster
®
5100-D Page 5 - 39 Repairs
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