jcb JS300 Service Manual page 949

Boom Down
1 Prepare the machine
a Operate the dipper out and lower the boom to set
the bucket on the ground.
Fig 11.
b Make the machine safe, refer to Section E,
Service Procedures.
c Connect a 0 - 400 bar (0 - 6000 lb/in
gauge and adaptor to port TP1 on the hydraulic
pump.
2 It is not physically possible to fully close the boom
ram, without lifting the undercarriage of the ground.
Therefore the ARV's must be swapped over.
a Fully raise the boom and then continue to operate
the right control lever as at A at minimum no-load
speed in the E mode.
Fig 12.
E-288
Note: For accurate pressure setting, the pressure should
be adjusted up to the required level. Release lock nut X.
Adjust setting screw Y to a pressure below the required
level and then bring the pressure back up for final setting.
Tighten lock nut X.
C030150-1
2 ) pressure
3
4
A
C002690-C1
9813/5100-1
Section E - Hydraulics
Hydraulic System Test Procedures
b The pressure gauge reading (Boom down) should
be compared to the technical data at the start of
the section. If it is outside the limits, adjust the
ARV.
Fig 13.
The relief valves for boom up and boom down must
be swapped and returned to the correct ports.
Restore Original MRV Pressure, refer to Section E,
Service Procedures.
Auxiliary Relief Valves
312460-C1
E-288