General Description; Power Input Circuits; Theory Of Operation - Lincoln Electric LN-8 SVM132-A Service Manual

E-2
REMOTE
OUTPUT
CONTROL
#75
#76
#77
#32
INPUT
RECEPTACLE
#31
#2
&
#4
C
O
N
T
A
C
T
O
R
CONTROL
OPTIONAL
BURNBACK
BOARD

GENERAL DESCRIPTION

The LN-8 is a semiautomatic wire feeder
designed for Innershield (FCAW) and
gas metal arc processes with the appro-
priate accessories. It is also suitable for
constant voltage (CV) submerged arc
welding processes. With the optional
variable voltage board installed the LN-8
can be used with constant current (CC)
procedures. The wire feed speed and
welding power source output can be
controlled from the LN-8.

POWER INPUT CIRCUITS

The 115VAC is applied (usually from the
welding power source) via the input
NOTE: Unshaded areas of block logic diagrams are the subject of discussion.

THEORY OF OPERATION

FIGURE E.1 – POWER INPUT CIRCUITS
#21
VARIABLE VOLTAGE
BOARD
WIRE FEED
SPEED CONTROL
CIRCUIT
BREAKER
#32A
2 OHMS
#531
FUSE
REED
GLP
SWITCH
ELECTRODE
#567
METER
SHUNT
ARMATURE
CONTROL
BOARD
#3
2
A
FIELD
RELAY
BOARD
WIRE
TRIGGER INTERLOCK
FEED
TRANS. SWITCH
SWITCH
receptacle, through the circuit breaker
and 2 ohm resistor to the control board,
the relay board, and the trigger trans-
former.
The 24VAC developed at the trigger
transformer is rectified on the relay
board and applied to the gun trigger cir-
cuit which controls the 1CR relay.
The 115VAC that is applied to the con-
trol board is rectified and controlled by
SCRs (See SCR Operation) and
applied to the armature of the wire feed
motor.
The relay board rectifies the 115VAC
and applies it to the field winding of the
wire feed motor.
LN-8
WIRE
THERMAL
FEED
CIRCUIT
MOTOR
BREAKER
GUN
CABLE
RECEPTACLE
E-2