Owner’s Manual 36
with a crocus cloth to maintain the finish under normal conditions. This should not be required more than
once each 1000 hours of operation.
3. ELECTRICAL TESTING - Testing generator field for opens and grounds:
A. Disconnect field lead from rectifier.
B. Set multimeter to read resistance, and connect the meter leads to the field leads. If field is open,
meter will read infinite resistance (very high ohms). Repair or replace field if it is open. Typical resis-
tance for these fields vary from 12.8 to 14.1 ohms.
C. Leaving one meter lead connected to the field, connect the other meter lead to the field shell. If meter
indicates continuity (any reading - should be infinite resistance), the field is grounded and should be
repaired or replaced. To determine which of the fields is grounded, cut the connector between the
two coils and retest to determine which coil has the low resistance path.
4. TESTING ARMATURE FOR OPENS AND GROUNDS (Fig. 3):
A. Remove all brushes.
B. Ground fault test - set multimeter to read high resistance (meg-ohms).
C. Holding one meter lead against a clean spot on the armature shaft, touch the other lead to each of
the slip rings (one at a time) while observing the meter. If meter indicates continuity (any reading
lower than one meg-ohm), armature is grounded. Dirt between the slip-rings and on the insulator
surface can cause grounding. If grounding was indicated, carefully clean all dirt off the slip-rings and
their insulators and then re-check it. Rplace the armature if it is grounded and unrepairable.
D. Testing for opens - set meter to read low resistance (R x 1 ohms). Holding one meter lead on surface
of slip-ring No. 1, touch other meter lead to surface of slip-ring No. 2 while observing the meter. Meter
should indicate continuity (low resistance - less than 1 ohm is typical). If the meter indicates open
circuit (infinite resistance) part of armature winding is open. This may be caused by a repairable
defect in the connection at the slip ring, however generally an open armature will have to be replaced.
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