Trigger And Shutdown Circuit - Lincoln Electric LN-9 SVM127-A Service Manual

E-3
CIRCUIT
BREAKER
INPUT
CONNECTOR
TO
CONTROL
BOARD
T1
TO
VOLTAGE
BOARD
METER
10VAC
BOARD
VOLTS
SPEED
SWITCH
TRIGGER AND SHUTDOWN
CIRCUIT
When the gun trigger switch is activated (closed), the
trigger board completes the trigger signal path. This
energizes the CR1 relay located on the power board.
The CR1 relay activates the wire drive motor and the
#2 and #4 circuit, which then activates the Lincoln
welding power source. The CR1 relay may also be
used to energize a gas solenoid.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
THEORY OF OPERATION
FIGURE E.3 – TRIGGER AND SHUTDOWN CIRCUIT
GEAR
BOX
WIRE
FEED
MOTOR
POWER SOURCE OUTPUT TRIGGER (#2 &#4)
TRIGGER
T2
BOARD
TRIGGER
CONNECTOR
24VAC
R1
28VAC
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
U
D
R
T
D
O
W
N
WIRE FEED
MOTOR
THERMOSTAT
TRIGGER SIGNAL
The normally closed relay located on the voltage board
is in series with the trigger signal. If an out-of-voltage-
range signal or a ground fault condition should occur,
the CR501 (on voltage board) relay contacts would
"open," and the trigger signal path would be interrupt-
ed. This would cause the wire feeder to "shut down"
until the gun trigger is released or the ground fault pro-
tector is reset.
VOLTAGE CONTROL
VOLTAGE SENSING
POLARITY
SWITCH
WIRE
SPEED
CONTROL
C
O
B
O
N
A
T
R
R
D
O
L
R
V
E
O
F
L
E
T
R
A
E
G
N
C E
E
VOLTAGE
CONTROL
VOLTAGE
BOARD
GROUND
LEAD
PROTECTOR
E-3