jcb JS300 Service Manual page 177

Operation
Operating Levers/Pedals
Left Joystick
The left hand joystick controls the slew of the superstructure and the movements of the boom. When released,
the joystick returns to the neutral position.
The superstructure will slew within its limits for as long as you hold the joystick over to one side. It will stop
automatically when you release the joystick due to the application of the slew brake.
When the joystick is returned to neutral, the machine will still not stop moving immediately because of inertia.
Remember this when you do a swing operation. The operation of the bucket attachment is reversed when it
is fitted in the reverse position, be careful.
To slew to the left, move the joystick to the left (position 1).
To slew to the right, move the joystick to the right (position 2).
The dipper will move within its limits for as long as you hold the joystick forward or backwards. It will stop
automatically when you release the joystick.
To raise the boom, pull the joystick backwards (position 4).
To lower the boom, push the joystick forwards (position 3).
If the engine stops and will not re-start, to lower the attachment the ground:
1. Make sure the ignition is on.
2. Make sure the controls isolation lever is down.
3. Make sure the controls isolation switch button is off.
4. Push the joystick forwards (position 2).
Press and hold the boom priority switch to change priority of slew to boom raise. Release the switch to deselect
boom priority. Selecting the boom priority switch during simultaneous slew and boom operation will restrict flow
to the slew motor and therefore give more flow to the boom up operation.
Press and hold the auxiliary hold button to remember the last position of the proportional control (if fitted).
Release the button to stop the flow. This is particularly useful where continuous prolonged hydraulic flow is
required. A momentary press of the auxiliary hold button whilst the proportional control is not in the neutral
position will store the position.
Press the horn switch to sound the horn. Sound the horn to give a signal before the machine is started or
before you engage travel or slew.
The proportional auxiliary control (high flow) switch is a variable position switch, spring loaded to the central off
position, it provides bi-directional flow for relevant attachments, e.g. weed cutter, grab rotate. Press and hold
the switch to the right or left, as appropriate, for as long as the attachment is to be used. Release the switch to
turn off the attachment. The hammer/auxiliary foot pedal can be used but with on/off functionality only.
On machines with a 'Supershort' dipper or a 'Triple Articulated Boom', the bucket can foul the boom when the
dipper is swung inwards. Be careful when you swing the dipper is inwards.
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