JLG X390AJ Operator Manual - Manual (Page 84)

SECTION 5 - EMERGENCY PROCEDURES
5-6 – JLG Lift – 3128792
Manual Descent with Engine Running but
without Electrical Power
(Combustion Engine Only)
(See Figure 5-3.)
ENSURE BOOM IS NOT POSITIONED OVER THE OUTRIGGERS OR
OVERHEAD OF PERSONNEL BEFORE LOWERING.
1. Remove the electrical components cover on the left
side of the machine and locate the valve adjustment
tool, black knob, and knob installation screw in the plas-
tic bag.
2. Slide the adjustment knob onto the proportional valve
stem (item 1 - Figure 5-3.) next to the electrical engine
switch box on the left rear of the machine.
NOTE: The proportional valve adjusts the speed of the boom
movements (pressure flow) when using the boom
control valves at the valve distributor on the left side of
the machine in Figure 5-2. Without electrical power
you must manually open this valve with the adjustment
knob before operating the boom controls.
3. Turn the proportional valve adjustment knob clockwise
approximately four turns, the more turns the valve is
open the faster the movement of the boom component.
Always carry out movement at the slowest possible
speed.
4. Operate the boom manual hydraulic control valve levers
(items 5 thru 8 - Figure 5-2.) at the ground control valve
distributor.
5. Make boom movements in the following sequence:
• fully retract main boom
• fully lower jib
• fully lower tower boom
• fully lower main boom
6. When emergency operation is complete, loosen adjust-
ment knob on the proportional valve completely,
remove it and place it back in the protective bag.
7. Position the Emergency Stop to the OFF position.
Figure 5-3. Proportional Flow Valve
1