JLG 723A Service Manual - Manual (Page 33)

3-3 L2906H, 2906H, 3507H, 619A, 723A, 29.6LP, 29.6, 35.7
Boom
3.2 SAFETY INFORMATION
3.3 BOOM SYSTEM - TWO SECTION
BOOM
3.3.1 Boom System Description
The boom operates via an interchange among the
electrical, hydraulic and mechanical systems. Components
involved include the joystick, tilt cylinder, extend/retract
cylinder, lift/lower cylinder, compensating cylinder,
electronic sensors, various pivots, supporting hardware
and other components.
3.4 BOOM ASSEMBLY MAINTENANCE
The boom assembly consists of the first and second
section booms and supporting hardware.
Note: Before removing the boom or boom section, the
carriage or any other attachment must be removed from
the quick attach.
Before beginning, conduct a visual inspection of the
machine and work area, and review the task about to be
undertaken. Read, understand and follow these
instructions.
During service of the boom, perform the following:
1. Check wear pads. (Refer to Section 3.5.1, “Wear
Pad Inspection.”)
2. Apply grease at all lubrication points (grease fittings).
(Refer to Section 2.6, “Lubrication Schedule.”)
3. Check for proper operation by operating all boom
functions through their full ranges of motion several
times.
Depending on your particular circumstance, the following
procedures explain the removal/installation of individual
boom sections or removal/installation of the complete
boom.
3.4.1 Boom Removal
1. Remove any attachment from the quick switch
assembly.
2. Be sure there is enough room in front of the machine
to allow the boom sections to be removed. Park the
machine on a hard, level surface, fully retract the
boom, lower the boom, place the transmission
control lever in (N) NEUTRAL, engage the park
brake and shut the engine OFF.
3. Place a Do Not Operate Tag on both the ignition key
switch and the steering wheel, stating that the
machine should not be operated.
4. Properly disconnect the battery.
5. Open the engine cover. Allow the system fluids to
cool.
6. Remove the quick switch assembly. Refer to Section
3.6.1, “Quick Attach Removal.”
7. Support the front of the boom by placing a sling
behind the boom head. Support the lift/lower cylinder
and remove the lock bolt (1) and pin from the rod
end of the lift/lower cylinder (2). Lower the lift/lower
cylinder onto the frame rails.
8. Label and disconnect the tilt and auxiliary hydraulic
hoses attached to the machine at the rear of the
boom. Plug and cap the hose ends to prevent dirt
and debris from entering the hydraulic system.
9. Label and disconnect the extend/retract hydraulic
hoses at the extend/retract cylinder.
WARNING
DO NOT service the machine without following all
safety precautions as outlined in the “Safety Practices”
section of this manual.
MZ3630
1
2
MZ3640
3
4