1.22 CONTROL HANDLES

TM 5-3895-373-34 1.22 CONTROL HANDLES. Two control handles (joysticks) are located on the operator console. Each control handle is a friction held, bi-directional unit with adjustable drag. A clamp-type brake holds each handle at set position. Each handle has a throw of 30° on either side of center. Control handles operate on a 12 volt DC current. A printed circuit board on each handle subassembly converts the 12 volts DC to a 96 mA signal to power the coils on pump pilot control valves. Full current output, with the control handles at 30°, is a maximum of 2 amps into a 5 ohm load. Step current (96 mA) is a maximum of 50% of full current output. The current can be adjusted through the use of threshold and gain controls. Control handles govern startup functions, travel speed variations, brake release (when engaging paving machine travel), and automatic screed vibration operation. The paving machine engine will not start unless both control handles are centered. Each control handle operates its respective track. When paving with screed vibration in automatic, screed vibration is halted when either control handle is centered. Screed vibration resumes when both handles are moved out of the center position. 1.23 HIGH SPEED SHIFT VALVE. The high speed shift valve is a 12 volt DC, solenoid activated, two-position, four-way valve that enables the paving machine to move at two separate speed ranges. The high speed is used for traveling, and the low speed is used for paving. The solenoid is wet-operated for low impact and smooth operation. The high speed shift valve controls oil flow to the hydraulic motor control pistons. The oil flow determines the control piston angle, which determines drive speed. The internal charge circuit of the left propulsion pump provides the required flow of hydraulic oil to the high speed shift valve. 1-13