TM 5-3805-291-23-1
THEORY OF OPERATION - CONTINUED
0003 00
ELECTRO-HYDRAULIC SYSTEM - CONTINUED
N OT E
The Start of Modulation Current pr vides pilot pressure to shift the main valve spool. When the main
o
spool is shifted, hydraulic oil will flow to the cylinders. The Start of Modulation Current varies for each
valve and must be adjusted for each valve. The modulation current must be calibrated on each individ-
ual machine.
The Maximum Modulation Current provides enough pilot pressure to fully shift the main valve spool.
When the main valve spool is fully shifted, the cylinder will reach maximum velocity.
427-C1811
d.
Above illustration represents an interpretation by implement ECM of signal from lift lever when joystick is in
RAISE position. As joystick is moved from HOLD position, no current is supplied to lift linkage raise solenoid
until sensor is approximately three degrees from center. At approximately three degrees of travel, ECM supplies
Start of Modulation Current (1) to raise solenoid. As joystick is moved toward detent, current supplied to raise
solenoid increases. Increase is linear up to Raise Maximum Modulation Current (2). Maximum modulation current
is reached just before joystick enters detent position. Entering detent position will not cause a further increase in
current.
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