JLG 120HX Service Manual - Manual (Page 72)

SECTION 2 - PROCEDURES
2-50 – JLG Lift – 3120819
14. Adjust HI trimpot until ammeter indicates the value
shown in Table 2-6, Platform Controller Settings (S/N
38697 to Present).
15. Repeat step 13.
16. Place the creep toggle switch in the creep on posi-
tion. Adjust the mid trimpot to the value shown in
Table 2-6, Platform Controller Settings (S/N 38697 to
Present) for mid.
17. Move controller handle back to the position given in
step 6 and check ammeter reading. This reading will
have changed due to HI trimpot adjustment, and
must be readjusted back to the value shown in Table
2-6, Platform Controller Settings (S/N 38697 to
Present).
18. Move handle to the position given in step 13 and
check ammeter reading. This reading too will have
changed due to LO trimpot readjustment, and must
be adjusted back to the value shown in Table 2-6,
Platform Controller Settings (S/N 38697 to Present).
19. Move controller handle back to the position given in
step 6 and check ammeter reading. This reading will
have changed due to MID trimpot adjustment, and
must be readjusted back to the value shown in Table
2-6, Platform Controller Settings (S/N 38697 to
Present).
20. Repeat steps 17 and 18 until LO and HI readings as
shown in Table 2-6, Platform Controller Settings (S/N
38697 to Present) can be achieved without further
trimpot adjustments.
21. Adjust the Ramp trimpot clockwise according to
Table 2-6, Platform Controller Settings (S/N 38697 to
Present).
22. Release footswitch.
23. Using all applicable safety precautions, start
machine and allow hydraulic oil to reach a tempera-
ture of 100° F - 140° F (38° - 60° C).
24. Depress footswitch and operate controller until 1/2
of slide lock is out of the housing lock notch. Hold
control handle in that position.
25. Adjust LO trimpot until applicable function just starts
to work. Immediately stop adjustment.
26. Release footswitch and stop machine.
27. Seal each trimpot with a drop of enamel paint to pre-
vent maladjustment due to vibration.
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-
TIONA L FUNC TION. THEREFORE A DJU STI NG TH E R AMP
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 20-30 cm (8-
12 in.) 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
20-30 cm (8-12 in.) 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 mp t i m e a n d t h e te s t
repeated.