JLG 26MRT Service & Maintenance Download

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SECTION 2 - PROCEDURES

3120791

– JLG Sizzor –

2-29

The valve driver card potentiometer adjustments are as
follows:

P1 - DRIVE FWD ACCEL (A RAMP UP)

P2 - DRIVE FWD DECEL (A RAMP DOWN)

P3 - DRIVE FWD HIGH (A MAXIMUM)

P4 - DRIVE FWD LOW (A MINIMUM)

P5 - DRIVE REV ACCEL (B RAMP UP)

P6 - DRIVE REV DECEL (B RAMP DOWN)

P7 - DRIVE REV HIGH (B MAXIMUM)

P8 - DRIVE REV LOW (B MINIMUM)

2.19 VALVE DRIVER CARD SETUP

PROCEDURE

Elevate the drive wheels and support them securely.

Turn all eight potentiometers fully counter-clockwise.
Turn until the potentiometer clicks at the end of its
travel.

Start the engine from the platform.

Verify that the horsepower card (HP) card is operat-
ing properly as follows:

a. Connect a voltmeter to the HP card with the red

lead connected to “L” and the black lead to
“MO.” These are the only two test points avail-
able on the HP card.

b. With the engine at idle, and enable depressed,

the voltage should read approximately -3.8 volts
dc. With the engine running at high engine, the
voltage should read at least +2 volts dc. The
reading will probably be slightly higher.

NOTE: If the horsepower card’s voltage does not change,

then the card is not receiving the RPM signal, the
engine speed is not correct, or the card is bad.
Replace the horsepower card if necessary. DO NOT
ATTEMPT TO ADJUST THE HORSEPOWER
CARD.

Disconnect the control box wiring harness from the
valve driver card, then connect test harness
4922012 between the valve driver card and the con-
trol box wiring harness. To adjust the “A Driver” for-
ward direction, connect the ammeter to the “A
Driver“ forward output wire on the test harness to
adjust trimpots P1 through P4.

Energize drive forward and hold the joystick at
“FULL ON.” Make sure the speed switch is set to
high speed.

Turn P4, drive forward low, clockwise until the
wheels just start to move. The ammeter should read
about 0.4 Amps or 400 mA. This value is approxi-
mate, the reading will be slightly different from one
machine to another.

NOTE: Adjusting the low setting affects the high. Adjusting

the high setting does not affect the low. If you have to
re-adjust the low after the high is set, you must re-
check the high, the decel, and the accel settings.

with drive forward still full on, set P3, drive forward
high. Turn P3 clockwise until the ammeter reads 1.1
Amps or 1100 mA. DO NOT TURN ANY HIGHER!
The valve will draw more current but no additional
speed will be gained and the acceleration and
deceleration will not work properly.

Next, set P2, drive forward deceleration. Turning P2
clockwise increases the time. Turn the pot approxi-
mately 15 turns and test by energizing drive forward,
stroking the joystick to full on, then letting go. It
should take about 3 seconds for the drive wheels to
stop. Adjust P2 to obtain 3 seconds.

10.

Next, set P1, drive forward acceleration. Turning P1
clockwise increases the acceleration. Turn the pot
approximately 15 turns and test by going from no
drive to full on drive forward, then timing how long it
takes until the meter reads 1.1 A or 1100 mA. It
should take about 5 seconds. Adjust P1 to obtain 5
seconds.

11.

To adjust the “B Driver” reverse direction, connect
the ammeter to the “B Driver“ reverse output wire on
the test harness to adjust trimpots P5 through P8.

12.

Energize drive joystick and hold the joystick at
“FULL ON.” Make sure the speed switch is set to
high speed.

Figure 2-23. Valve Driver Card