JLG 120HX ANSI Service Manual - Manual (Page 71)

SECTION 2 - PROCEDURES
3120686 – JLG Lift – 2-51
RAMP Adjustment
Controllers equipped with the RAMP feature actually com-
pensate for abrupt control handle operation by slowing
the response time of the output signal regardless of the
speed with which the handle is moved.
IT SHOULD BE REMEMBERED THAT THE RAMP FEATURE OPER-
ATES IN BOTH DIRECTIONS OF THE PARTICULAR PROPOR-
TIONAL FUNC TION. THEREFORE ADJU STI NG THE RAMP
POTENTIOMETER TO PROVIDE A DELAY IN STARTING A FUNC-
TION WILL PROVIDE A CORRESPONDING DELAY IN STOPPING
THAT FUNCTION.
1. Drive Controller.
a. Using all applicable safety precautions, start
machine and ensure that adequate space is
available to maneuver machine.
b. Position ENGINE SPEED switch to HIGH and
DRIVE SPEED switch to HIGH.
NOTE: Clockwise rotation of the ramp potentiometer adjust
screw increases ramp (delay) time; counterclockwise
rotation decreases ramp (delay) time.
c. Operate machine drive function and adjust ramp
pot so that machine will stop within 8-12 in. (20-
30 cm) when the control handle is released from
the full extent of its travel.
d. Operate machine drive function in the opposite
direction and check that stopping distance of 8-
12 in. (20-30 cm) is maintained.
e. Release footswitch and stop machine.
f. Seal ramp pot adjustment screw with a drop of
enamel paint to prevent maladjustment due to
vibration.
g. Install controller and secure machine.
2. Swing Controller.
a. Using all applicable safety precautions, start
machine and ensure that adequate space is
available to maneuver machine.
b. Fully extend boom at horizontal.
c. Position ENGINE SPEED switch to LOW.
d. Operate SWING controller at full speed to the left
and then quickly move controller to the full
speed RIGHT position. The platform should
slow, stop and then swing right in one smooth
and continuous operation.
e. If control valve initiates swing right motion before
platform momentum is stopped, the ramp poten-
tiometer adjust screw should be rotated clock-
w i s e to i n c r e a s e r a m p t i m e a n d t h e te s t
repeated.
f. If after operating SWING function as described
in step (d), the platform stops moving to the left
and the spring action of the boom tends to ini-
tiate the swing right motion before the control
valve starts to operate, the ramp pot adjust
screw should be rotated counterclockwise to
decrease ramp time.
g. Repeat the test in both swing directions.
h. Release footswitch and stop machine.
i. Seal ramp pot adjustment screw with a drop of
enamel paint to prevent maladjustment due to
vibration.
j. Install controller and secure machine.