Manitowoc Published 10-01-2012, Control # 045-08 1-55
777 SERVICE MANUAL INTRODUCTION
1
hoisted load will drop unless controlled by application of the
working brake.
When front drum control handle is pulled back in the hoist
position, the PC opens and closes the following circuits:
• OPENS circuit to front drum clutch solenoid HS20. This
releases hydraulic pressure from the cylinder of the front
drum clutch. The clutch spring-applies, connecting the
drum to the motor drive assembly.
• CLOSES a regulated voltage circuit to the front hoist
pump EDC.
• CLOSES clutch switch to verify clutch engagement.
The circuit to front drum brake solenoid HS12 and front drum
band brake solenoid HS16 remains closed, keeping the park
brakes released.
The front drum clutch applies first, then the front hoist pump
EDC strokes the front hoist pump to hoist the load. The PC
governs the hoisting speed by varying the voltage to the
EDC with movement of the front hoist control handle and its
program requirements.
CAUTION
Momentary Load Drop!
Begin moving control handle before releasing working
brake to hold load while clutch engages and power
becomes available to drum.
Load will drop immediately unless held by working brake!
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