Komatsu PC500LC-10R Shop Manual page 219

10 STRUCTURE AND FUNCTION
When the pump secondary drive switch is turned on due to failure in pump con-
troller, and the light load is applied to the main pump
1.
If the pump controller is faulty, the pump secondary drive switch is turned on to shift it to the resistor side.
At this time, the power is supplied directly from the battery. The resistor is inserted to control the current
flowing to PC-EPC valve solenoid (1) since the current is too high.
As the current is stabilized, the force pressing piston (2) is stabilized.
2.
When main pump pressures (PP1) and (PP2) are low, the combined force of the force of PC-EPC valve
solenoid (1) and pump pressure is lower than the spring set force, and accordingly spool (3) is balanced at
the left side.
3.
The port (C) is connect to the drain pressure in port (D). The large diameter piston side of servo piston (9)
is also set to the drain pressure (PT) through LS valve.
4.
The pressure on the small diameter piston side is high, and servo piston (9) moves in the direction to in-
crease the discharged volume.
PC500LC-10R
COMPONENT PARTS OF HYDRAULIC SYSTEM
AEP19360
10-125