Lincoln Electric LF-72/74 Service Manual page 81

Section E-1
- THEORY OF OPERATION SECTION -
Theory of Operation ...............................................................................................Section E
General Description ......................................................................................................E-2
Input Receptacle, Control Board and Operator Controls.............................................E-2
Drive Motor, Tach Feedback and Gas Solenoid...........................................................E-3
14 PIN
INPUT CABLE
RECEPTACLE
24/42 VAC
TABLE OF CONTENTS
FIGURE E.1 – LF-72/74 BLOCK LOGIC DIAGRAM
OPTIONAL OPTIONAL
BURNBACK REMOTE
TIMER VOLTAGE
CONTROL
CONTROL BOARD
WIRE FEED
SPEED POT.
LF-72/74 SINGLE/DUAL
3.75 AMP
OVERLOAD
PROTECTION
WIRE DRIVE
RECEPTACLE
TRIGGER
INTERLOCK
2-STEP
Section E-1
GAS
SOLENOID
WIRE
DRIVE
MOTOR
TACK
To Gun Trigger
COLD FEED
GAS PURGE