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 NOTE
end frame bearing to prevent entry of dirt
and other foreign material; also place a
If the rotor is not defective, but the
piece of tape over the shaft on the slip
generator fails to supply rated output,
ring end.
t h e defect is in the diode trio, recti-
CAUTION
f i e r bridge or stator.
USE PRESSURE SENSITIVE TAPE AND NOT
FRICTION TAPE, WHICH WOULD LEAVE A
GUMMY DEPOSIT ON THE SHAFT.
a. If brushes are to be reused, clean with
a soft dry cloth.
f. To remove the drive end frame from the
rotor, place the rotor in a vise and
tighten only enough to permit removal
of the shaft nut.
CAUTION
AVOID EXCESSIVE VISE TIGHTENING, AS
THIS HAY CAUSE DISTORTION OF THE ROTOR.
g. Remove the shaft nut, washer, pulley,
Plate 12337. Checking Rotor Field Winding
fan and the collar, then separate the
drive end frame from the rotor shaft.
DIODE TRIO CHECK:
The diode trio is identified in Plate 12338.
5 - 6 6 . INSPECTION
First, connect an ohmmeter using lowest range
scale from diode trio long connector to the end
ROTOR FIELD WINDING CHECKS:
frame (as shown in plate 12338, step 2), then
reverse lead connections. If both readings are
the same, check for grounded brush lead clip
a. To check for opens, connect the test lamp or
caused by omission of insulating washer (plate
ohmmeter to each slip ring.
If the lamp fails
12338) , omission of insulating sleeve over screw,
t o light, or if the ohmmeter reading is high
( i n f i n i t e ) , the winding is open, (Plate 12337).
b. The winding is checked for short circuits or
excessive resistance by:
1. connecting a battery and ammeter in series
with the edges of the two slip rings. An
ammeter reading above the value specified
(Refer to SPFCIFICATIONS section)indicates
shorted windings; a reading below the value
s p e c i f i e d indicates excessive resistance.
2. an alternative method, which is to check the
resistance of the field by connecting an
ohmmeter to the two slip rings (per Plate
If the resistance reading is below
12337) .
the specified value, the winding is shorted;
if above the specified value, the winding
has excessive resistance.
NOTES:
1. The specified resistance value can
be determined by dividing the vol-
tage by the current given in SPEC-
IFICATION Section.
2. Remember that the winding resistance
and ammeter readings will vary slightly
with winding temperature changes.
Plate 12338. View Inside Typical End Frame Ass'y
5-50D
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