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THEORY OF OPERATION
E-4E-4
LN-25™
OPTIONAL CIRCUITS
CONTACTOR
The contactor, contactor PC board, and cold inch
switch are commonly incorporated in the LN-25™. This
feature enables the user to have an electrically “COLD”
gun even though the power sources output terminals
are electrically “HOT”. Upon receiving a command
from the control board, the contactor PC board sends
a current signal to activate the contactor. The signal
closes the welding current path from the cable to the
conductor block, making the gun electrically “HOT”.
The cold inch switch allows the user to feed wire
without closing the contactor. In this manner, the
electrode wire can be fed through the gun with the gun
tip electrically “COLD”. See Figure E.4.
LATER MODELS
Codes above 11144 have the Contactor circuitry
added to the Control Board and the Contactor PC
Board has been eliminated. Older codes that have
been upgraded to the newew PControl Board may
have had the Contactor PC Board removed
GAS SOLENOID
Early Models Only (Below 10500)
The gas solenoid feature permits the LN-25™ to be
used for gas metal arc welding (GMAW) processes.
When the gun trigger circuit is activated, the control
board signals the solenoid PC board to activate the
gas solenoid, which allows shielding gas to flow
through the gun to the arc.
Later Models Only (Above 10500)
The solenoid PC board circuitry has been added to
the Control board and the solenoid PC board has been
eliminated.
FIGURE E.4 – OPTIONAL CIRCUITS.
NOTE: Unshaded areas of block logic diagrams are the subject of discussion.
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ELECTRODE
INPUT CABLE
TO WORK
SENSING LEAD
P
O
L
A
R
I
T
Y
S
W
I
T
C
H
VOLT
METER
CONTROL
BOARD
WIRE FEED
MODE SWITCH
SOLENOID
PC BOARD
GAS
SOLENOID
WIRE SPEED
CONTROL
RANGE
SWITCH
CONDUCTOR
BLOCK
M
O
T
O
R
HALL
EFFECT
MODULE
GUN
TRIGGER
CONNECTOR
OPTIONAL
CONTACTOR
BOARD
COLD
INCH
SWITCH
OPTIONAL
CONTACTOR
GUN CABLE
RPM FEEDBACK
ARMATUREVOLTAGE
EARLY MODELS ONLY - LATER MODELS HAVE CIRCUITRY
INCLUDED ON CONTROL BOARD