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Section D
35 - 2
Basic System Operation
Component Identification
A
Right hand joystick
B
Left hand joystick
C
Operator seat
D
Pilot supply valve
E
Supply valve solenoid
F
Oil filter access plug
G
Accumulator
H
Right hand pilot control valve
J
Left hand pilot control valve
K
Seat mounted micro switch
L
Joystick mounted 'mode switch'
M
Loader valve block
N
Excavator valve block
P
Hose sleeves
Q
Pressure relief valve
R
Hose clamps (seat base mounted)
S
Mechanical linkages
T
Machine hydraulic tank
U
Bolt on spool section - extending dipper (if fitted)
V
Plastic cover panel
F
9803/3280
Precision Control (Servo)
E
Q
D
A402080
Purchased from www.WorkshopManuals.co.uk
Controls
The following section describes the JCB Precision Control
*
system fitted to machines up to serial number 931159. There
is another JCB Precision Control system fitted to later
machines, which is described in a separate section. Refer to
Precision Control (Servo) - Machines from January 2003.
Circuit Description
The JCB Precision Control system facilitates operation of the
backhoe (excavator) via joysticks A and B mounted in the
arms of the operator's seat. Unlike manual machines the
excavator valve spools are moved by hydraulic pressure and
not directly by a mechanical levers.
A pilot supply valve D maintains a constant supply of oil at
servo pressure to the right and left hand pilot control valves
H and J. The valves are mounted at the rear of the seat arm
rests.
The joysticks each operate a hydraulic pilot control valve (H
or J as applicable) via a mechanical linkage. These valves in
turn operate the excavator valve spools via hydraulic pilot
pressure. The interconnecting hoses are routed to and from
the pilot control valves through the central seat support pillar
and then through the cab floor.
The mechanical linkages S incorporate universal type
couplings at both ends.
The joysticks control boom, dipper, bucket and slew
functions. Unlike manual control machines, the foot pedal
controlled auxilary valve spool (typically used to operate the
extending dipper ram) is located on the loader valve block.
For details of this valve spool see Section E.
The seat arms incorporating the joysticks are adjustable for
both height and length. A gas strut mounted in the left hand
arm supports the weight of the assembly when adjusting the
height.
Note: Precision control machines - extending dipper.
When fitted, the extending dipper ram is controlled by bolt
on spool section U located on the loader valve. The spool is
actuated by the normal foot pedal via a cable.
Section D
35 - 2
Issue 2*
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