Manitowoc Published 10-01-2012, Control # 045-08 1-49
777 SERVICE MANUAL INTRODUCTION
1
Hoist Bucket
See Figure 1-34 for following procedures.
When rear hoist control handle is pulled back, the PC
energizes front and rear drum park brake solenoids HS12,
HS8, and front and rear drum band brake solenoids HS16,
and HS17. As the solenoids shift, hydraulic system pressure
is supplied to release the front and rear drum hydraulic park
brakes.
At the same time, the PC closes regulated voltage circuits to
the front and rear hoist pump EDCs. The EDCs tilt the pump
swashplates in the hoisting direction, causing the front and
rear hoist motors to rotate the drums and raise the bucket. To
ensure the bucket remains closed when raising, the PC
monitors the high pressure side of both load drum systems
for differences in working pressures. The PC compares this
data and then calculates a correction factor to maintain equal
lifting pressure in both systems. This correction factor is then
FIGURE 1-34
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