Inspection And Service; Reassembly - JLG 1930ES Service Maintenance Manual

SECTION 3 - CHASSIS & SCISSOR ARMS

Inspection and Service

1. Carefully blow out any accumulated carbon dust
and dirt from the end head and the frame assembly
using clean, oil free, compressed air.
2. Replace brushes (3) that are worn below their
usable length (0600 in.), show signs of uneven wear
or signs of overheating, such as discolored brush
shunts and brush springs. Brushes should always
be replaced in complete sets of four or eight. USe
identical replacement parts; do not substitute brush
grades as the brushes are matched to the motor
type and application to provide the best service.
Substituting brushes of the wrong grade can cause
premature failure and excessive brush wear.
3. Make sure the brush box assembly (5) is tight on the
commutator end head. Replace brush box assem-
blies in the commutator end head if they are physi-
cally damaged or brush holders are loose on the
brush plate.
4. Visually inspect the frame and field assembly (1) for
overheating or other signs of damage. Check all wir-
ing to insure that the insulation is in good condition.
Verify that pole screws are torqued to 250-300 in-lb
[28.2-33.9 N-m]. Verify field resistance using a suit-
able ohmmeter per the appropriate motor specifica-
tion. Verify that the field is electrically isolated from
the frame using a dielectric tester. Replace as neces-
sary.
5. Visually inspect the armature (2) assembly for signs
of overheating or physical damage. Visually inspect
the seal surface of the shaft for excessive wear.
Check for grounded circuits using a dielectric tester
by applying voltage between the commutator and
the shaft. Visually inspect the commutator for exces-
sive wear and overheating. Replace as necessary.
6. Visually inspect the brake surfaces for excessive
wear. Remove any RTV Silicone sealant that may be
present on the friction disc, cover, or commutator
end head. Replace brake assembly (11) if neces-
sary.
7. Visually inspect the wire harness (8) for frayed insu-
lation, loose terminals, or other damage. Replace as
necessary.
3-30

Reassembly

1. After inspection and servicing, reassemble the wir-
ing in the commutator end head (9) as originally
found. Ensure the wiring does not contact metal
parts and that it allows the brushes to move unre-
stricted in the holders. Motor terminals must be
assembled as shown Figure 4. Torque bottom termi-
nal nut to 110-140 in-lb. (12.4-15.8 Nm).
2. After the motor has been disassembled, it is recom-
mended that new bearings be installed because
bearings may have been damaged during removal.
Although the bearings may appear and feel good,
the bearing races could be "brinelled" (races or balls
deformed) and may exhibit noise and vibration prob-
lems or fail within a relatively short period of service.
Press a new bearing into the commutator end head,
pressing on the outer race only. See Figure 3.
Replace the snap ring (6) in the snap ring groove.
1. Press Fixture must press against Outer Race
2. Bearing
3. End Head (held stationary)
4. Armature Assembly
5. Assembled End Head, Bearing, and Retaining Ring
6. Press Fixture must press against Inner Race (held sta-
tionary)
Figure 3-27. Bearing Pressure Guidelines
3. Press the armature (2) commutator end into the
commutator end head and bearing assembly, care-
fully supporting the inner-race of the bearing. See
Figure 3.
– JLG Lift – 3121166