Lincoln Electric SVM138-A Service Manual page 59

Section E-1
-THEORY OF OPERATION SECTION-
Theory of Operation .............................................................................................................Section E
General Description ...............................................................................................................E-2
Power Input Circuits...............................................................................................................E-2
Trigger and Shutdown Circuit ................................................................................................E-3
Arc Voltage, Wire Speed Control and Metering.....................................................................E-4
Printed Circuit Board Functions.............................................................................................E-5
POWER SOURCE OUTPUT TRIGGER (#2 &#4)
CIRCUIT
BREAKER
INPUT
CONNECTOR
TO
CONTROL
BOARD
T1
TO
VOLTAGE
BOARD
METER
10VAC
BOARD
VOLTS
SPEED
SWITCH
TABLE OF CONTENTS
GEAR
BOX
WIRE
FEED
MOTOR
TRIGGER
T2
BOARD
TRIGGER
CONNECTOR
24VAC
F
U
S
E
R1
28VAC
FIGURE E.1 - LN-9 GMA BLOCK LOGIC DIAGRAM
LN-9 GMA Wire Feeder
WORK VOLTAGE SENSING
ELECTRODE VOLTAGE SENSING
HALL EFFECT
DEVICE
WIRE SPEED CONTROL
+ 15VDC
GAS
SOLENOID
TRIGGER SIGNAL
+ 15VDC
P
B
O
O
W
A
S
R
E
H
D U
R
T
D
O
W
N
R
E
F
E
R
E
N
C
E
TRIGGER SIGNAL
Section E-1
VOLTAGE CONTROL
POLARITY
SWITCH
WIRE
SPEED
CONTROL
C
O
B
O
N
A
T
R
R
D
O
L
V
O
L
T
A
G
E
VOLTAGE
CONTROL
VOLTAGE
BOARD
GROUND
LEAD
PROTECTOR