Complete PDF Service Manual for the following JCB Mini Excavators:
- JCB 802.7 M747001 on
- JCB 803 M665001 on
- JCB 803 M666001 on
- JCB 803 M765001 on
- JCB 804 M734001 on
Component Key 14 R.H. Servo Hand Controller
P1 Pump Section 1 14A Boom Control
P2 Pump Section 2 14B Bucket Control
P3 Pump Section 3 14C Check Valves (Standard setup)
P4 Pump Section 4 to M665736 15 L.H. Servo Hand Controller
T Tank 15A Swing / Slew Control
E Engine 15B Dipper Control
1 Main Relief Valve Test Block 16 Dual Solenoid Valve
1A Swing/Slew Dozer Main Relief Valve 17 Return Filter
1B Digging and Tracking Main Relief Valve 18 Suction Strainer
1C Servo Main Relief Valve 19 High Speed Selector
1D Pressure Reducing Valve *20 Accumulator M665143 on
1E By-pass Filter 21 Solenoid Lock Valve
1F Non-return Valves 22 High Pressure Carry Over (HPCO) M666001 on
1G Gauge Connection Points 23 Servo Pressure Maintenance Valve Block
2 Valve Block M666001 on
2A Auxiliary Relief Valves 23A Pressure Maintenance Valve M666001 on
2B Auxiliary Spool 24 Oil Cooler M666001 on
2C Track Spool to M665736
2D Boom Boost Spool
2E Dipper Spool
2F Non-return Valves
2G Auxiliary Couplings (Double Acting)
2H Auxiliary Couplings (Single Acting)
3 Valve Block
3A Auxiliary Relief Valves
3B Track Spool
3C Boom Spool
3D Bucket Spool
3E Non-return Valves
3F Restrictor
4 Valve Block to M665736
4A Auxiliary Relief Valves to M665736
4B Slew Spool
4C Swing Spool
4D Dozer Spool
4E Non-return Valves to 665736
5 L.H. Track Motor
, 2 Hydraulics 2
2-6 2-6
SERVO CIRCUIT *803 to M665736 SERVO HAND CONTROL CIRCUIT
Section P4 of the engine driven pump supplies oil to the The control lever is mounted on a universal joint to allow
servo circuit. The flow for servo actuation is very small actuation of four plungers, each of which is connected,
and is dead-ended at the controls when they are in via service ports and pipework, to one end of a spool in
netural. Excess flow is directed from the pressure side the control valve block. Each plunger port contains a
of the pump to the suction side. plunger with its return spring and a spool.
Oil is fed via a filter 10 and non-return valve 11 into With the lever in neutral, oil from the pumps enters via a
accumulator 1. This stores sufficient pressure to ensure central port but is unable to flow any further than the
limited operation of the controls in the event of engine or spools. The service ports are connected to the tank via
pump failure. the hollow centre of the spool and through a cross-
drilling into the annular passage which connects to a
High speed track selector2 and servo cab controls3 and tank port.
4 are fed via solenoid lock valve 5 which is controlled by
an isolator switch. When the left hand seat pod is in the When the lever has been moved to depress a spool, the
'down' position, the switch is closed, energising solenoid cross-drilling is aligned with a pressure gallery, allowing
valve 5 which directs oil from line 1a to the controls via pressure to actuate the relevant spool of the control
line 5b. valve block. Pressure from the opposite end of the main
control valve spool is exhausted to tank via a hand
The servo cab controls direct pressure as required to control plunger which has remained in netural.
operate the excavator spools in the main control valves
6 and 7. When pressure has increased sufficiently to overcome
spool spring pressure, pressure builds up in the line,
Solenoid lock valve 5 also supplies pressure to the dual moving the spool upwards so that the cross-drilling
solenoid valve 8 which operates the control valve spool moves up into the control housing. This reduces the flow
for swing and slew. of oil through the port to the relevant control valve, so
balancing out the pressure in both this line and the line
When the left hand seat pod is raised, the isolator switch from the pump. If the control lever is moved slowly, this
opens, de-energising solenoid lock valve 5, connecting metering can be used to operate the relevant service
ports B to A and blocking port C. Pressure is exhausted gradually.
to tank T and the servo cab controls are thereby isolated,
thus preventing accidental operation of the services. KEY TO SERVO HAND CONTROL PORTS
The exhaust from the hand controls is now directed to Servo Port Colour Service
tank T. 3a Yellow
3b No Tag
3c Dark Green TBA
3d Natural
3e Red
3f Dark Blue
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