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STARTING MOTOR-DIRECT
DRIVE
8-21
CAUTION: Do
not damage the field coil during the
drilling operation.
(8)
Attach the insulated brush set to the series field
terminal with the flat washer and the number
8
self-
tapping screw.
(9)
Attach the shunt field lead to the new ground
brush set by making a loop around the terminal and
soldering the lead to the terminal with resin core
solder.
(10) Attach the ground brush terminal to the field
frame with the attaching screw. Fold the surplus
shunt
field
lead back along the brush lead and secure
with rubber insulating tape.
(11) Measure the brush spring tension with a
spring scale hooked under the spring near the brush
end. Pull the scale on a line parallel to the edge of
the brush and take a reading just as the spring end
leaves the brush. The spring tension should be
32
to
36 ounces. Replace the springs that do not meet spec-
ifications.
(12) Brush springs can be removed by spreading
the retainers and disengaging the springs from the
retainer legs.
TESTING THE ARMATURE
Testing the Armature for Short Circuit
Place the armature in a growler (Fig.
8 )
and hold a
thin steel blade parallel to the core and just above it,
while slowly rotating the armature in the growler. A
shorted armature will cause the blade to vibrate and
be attracted to the core. Replace a shorted armature.
Testing the Armature for Ground
Touch armature shaft and end of a commutator bar
with a pair of test lamp prods (Fig. 9). If the lamp
lights, it indicates a grounded armature. Replace a
grounded armature.
Fig. 8-Testing
Armature for Short
i f
K180
Fig. 9-Testing
Armature for Ground
Testing Commutator Runout, Refacing
Place the armature in a pair of
"V"
blocks and
check the runout with a dial indicator. Check both the
shaft and commutator. A bent shaft requires replace-
ment of the armature.
When the commutator runout exceeds
.003
inch,
the commutator should be refaced. Remove only a suf-
ficient amount of metal to provide a smooth, even
surf ace.
TESTING THE FIELD COILS
FOR GROUND
(1)
Remove the through bolts and remove the com-
mutator end frame.
(2)
Remove the brushes from the brush holders
and remove the brush ring (Fig. 2).
(3) Disconnect the field lead wires at the solenoid
connector and separate the field leads to make sure
Fig. I L T e s t i n g Series Coil for a Ground
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