JLG 120HX Service Manual - Manual (Page 74)

SECTION 2 - PROCEDURES
2-52 – JLG Lift – 3120819
Length Indicator Adjustment
1. Level the frame before beginning any adjustments.
2. Make all adjustments with the engine running unless
otherwise noted.
3. Fully retract the boom.
4. On the Load Radius Circuit Card, measure TP10 and
insure that 10 (+0.1/-0) Volts DC is present.
5. On the Load Radius Circuit Card, adjust P1 to 1.223
Volts DC while measuring TP1.
6. Make the following adjustment with the power off.
a. On the Load Radius Circuit Card, disconnect
connector J2 (the 6 pin connector on the printed
circuit board). Measure between Pin (6) of the
socket connector and ground (TB1-1), adjust
potentiometer P5 to a value of 1915 (+/- 5)
Ohms.
b. Adjust the 5K Ohm potentiometer in the boom
cable reel by loosening the three screws holding
it in place.
NOTE: When checking the resistance on the 6 pin connec-
tor as outlined in step (c), be sure to use connector
pins (6) and (3) corresponding to pins (6) and (3) on
plug 2 on the circuit card.
c. Rotate the 5K Ohm potentiometer until you mea-
sure 100 Ohms between Pin (3) and Pin (6) on
the 6 pin plug connector which mates with J2.
d. Tighten the three (3) screws on the 5K Ohm
potentiometer in the boom cable reel.
7. Turn the power on and measure TP2. It should be
1.287 Volts DC. Re-adjust the 5K Ohm potentiometer
if necessary.
Boom Angle Sensor Adjustment
1. With the platform level, the boom fully retracted and
at 45 (+/- 1) degrees elevation, measure the DC
voltage at TP5 on the Load Radius Circuit Card.
2. Loosen the three screws securing the sensor to the
box and rotate the sensor until 7.1 (+/- 0.1) Volts DC
is measured at TP5. Tighten the screws on the sen-
sor.
3. Return the boom to horizontal.
Radius Adjustment and Display Lights
Setting Procedure
1. On the Load Radius Circuit Card, measure TP11 and
adjust potentiometer P6 for a reading of 0.525 Volts
DC.
2. On the Load Radius Circuit Card, measure TP8 and
adjust potentiometer P2 for a reading of 2.050 Volts
DC.
3. On the Load Radius Circuit Card, measure TP9 and
adjust potentiometer P3 for a reading of 5.0 Volts
DC.
4. Telescope the boom until the leading edge of the red
marking tape is exposed from the mid boom. Adjust
potentiometer P2 until the red light just turns on and
the blue light turns off.
5. Measure TP2 and adjust potentiometer P4 until TP7
measures 0.05 Volts DC more than TP2. This deter-
mines the length of the boom (critical length) where
the lift down speed limiter is turned on.