Lincoln Electric LN-9 SVM127-A Service Manual page 53

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
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
POWER SOURCE OUTPUT TRIGGER (#2 &#4)
TRIGGER
T2
BOARD
TRIGGER
CONNECTOR
24VAC
R1
28VAC
FIGURE E.1 - LN-9 BLOCK LOGIC DIAGRAM
LN-9 Wire Feeder
WORK
ELECTRODE VOLTAGE SENSING
TACH
BOARD
WIRE SPEED CONTROL
+ 15VDC
TRIGGER SIGNAL
F
U
S
E
+ 15VDC
P
B
O
O
W
A
S
R
E
H
D U
R
T
D
O
W
N
WIRE FEED
MOTOR
THERMOSTAT
TRIGGER SIGNAL
Section E-1
VOLTAGE CONTROL
VOLTAGE SENSING
POLARITY
SWITCH
WIRE
SPEED
CONTROL
C
O
B
N O
A
T
R
R
D
O
L
R
V
E
O
F
L
E
T
R
E A
N G
C E
E
VOLTAGE
CONTROL
VOLTAGE
BOARD
GROUND
LEAD
PROTECTOR