Manitowoc 777 Service And Maintenance Manual

Reference Only
INTRODUCTION 777 SERVICE MANUAL
1-44 Published 10-01-2012, Control # 045-08
Liftcrane Operation
When FULL-POWER mode is selected and confirmed at
crane mode selector, the crane is ready for general liftcrane
usage, and the PC ensures the clamshell, luffing, and setup
operations are inoperable.
When the front drum park switch is placed in the off position
while in full power mode, the PC automatically controls the
front drum hydraulic disc and band brakes in conjunction
with movement of front hoist control handle.
Front Hoist Rotation Indicator
Whenever the front drum rotates, front drum speed sender
completes a circuit to the PC, which activates rotation
thumper in control handle. This causes the rotation thumper
to move up and down with a varying frequency that conveys
the rotational speed of the front drum to the operator.
Off
See Figures 1-31, and 1-32 for following procedures.
When front hoist control handle is in the off position, the
handle neutral switch is open and the control circuit from the
handle potentiometer to the PC is not completed. The PC
receives no voltage from the handle, and it opens the circuits
to the front hoist pump EDCs, front hoist motor PCP valve,
front drum disc brake solenoid HS12, and band brake
solenoid HS16. Because these circuits are open, front hoist
pump does not stroke, front hoist motor remains at low
speed, and front drum brakes remain applied to prevent the
front drum from turning.
Hoist
See Figures 1-33, 1-34, and 1-35 for following procedures.
When front hoist control handle is pulled back for up
operation, the handle neutral switch closes, completing a
regulated voltage circuit from the handle potentiometer to the
PC. The PC interprets the signal for speed and direction and
closes voltage regulated circuits to the front hoist pump EDC,
front hoist motor PCP, and front drum brake solenoid HS12
releasing the disc brake. These circuits close only if the seat
switch is closed, drum park switch is closed, applicable
operating limit switches are closed free fall switch is closed,
and no operating faults are present.
FIGURE 1-30

Manitowoc 777 Specifications

General

Brand	Manitowoc
Model	777
Category	Construction Equipment
Language	English