jcb JS300 Service Manual page 781

Swing Park Brake (CT1)
When the Swing pressure switch is closed on the servo
shuttle valve, the MECU sends a signal to the CT1
solenoid, which allows servo pressure across the solenoid,
over the shuttle valve CT10 and across the Swing lock
solenoid CT3. Pressure exits at port B and releases the
Swing brake.
Controls Enable (CT2)
The solenoid energises when both the controls Enable
lever in the cab is in the lowered position and the isolator
button on the right hand fascia switch panel is turned off.
No further function will operate unless the isolator is
energised.
Oil from the servo pump enters the solenoid valve block at
port P which:
1 Charges the servo pressure accumulator.
2 Is available to the controls isolate spool (CT2).
When the controls enable solenoid energises oil at servo
pressure crosses the spool and becomes available to the
remaining 7 solenoid valves.
Oil exits the solenoid valve block at port B2 to feed the cab
manifold which distributes servo pressure to the cab servo
controls.
Swing Lock (CT3)
When the Swing lock button is selected in the cab the
Swing lock solenoid will energise five seconds after the
Swing shut off solenoid energises, sufficient time for the
Swing motion to stop before the Swing brake is applied.
Max Flow Control (CT4)
The solenoid energises when the CREEP travel speed is
selected (snail).
When selected the max flow control solenoid energises
and oil at servo pressure flows to both max flow control
ports of the pump via port C4. This restricts the maximum
pump flow.
E-120
Travel Speed (CT5)
When FAST speed travel is selected in the cab (hare) the
CT5 solenoid energises, which directs servo pressure to
the track drive motors via port C5 to select high speed
travel in the motors.
Boom Priority (CT6)
When the boom priority rocker switch in the LH console is
selected, the Boom up pressure switch is powered through
the MECU. When boom up is selected, the boom up
pressure switch closes and energises solenoid CT6, which
sends a pilot signal to port Pi1 in the main control valve and
selects the boom priority spool. This reduces the available
flow to the swing spool when operating boom up and swing
together.
2 Stage MRV (CT7)
This can be operated in two ways
1 When the power boost switch is selected, (located on
the front of the RH control lever) the 2 stage MRV
solenoid will energise for 3 seconds, then de-
energise for 9 seconds.
2 By selecting L1, L2 or L3 powerband. This will
permanently energise the 2 stage MRV solenoid.
When the 2 stage MRV solenoid is energised, servo
pressure acts on the 2 stage relief valve in the main
control valve via port C7 and selects the 2 stage relief
valve to its second stage (higher machine operating
pressure).
Cushion Off (CT8)
This function is operated by the cushion off switch in the
cab. When the cushion off solenoid is de-energised the
boom and dipper services are cushioned when the control
levers are released to improve controllability (cushion
control ON).
When the cushion off switch is selected the cushion off
solenoid energises. Oil at servo pressure via port C8 acts
on the cushion spools in the cushion valve via port C8 This
prevents cushioning of the boom and dipper services
(cushion control OFF).
9813/5100-1
Section E - Hydraulics
Solenoid Valve Block
Operation
E-120