Theory Of Operation; General Description; Power Input Circuits - Lincoln Electric LN-9 SVM127-A Service Manual

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GENERAL DESCRIPTION

The LN-9 is a semiautomatic wire feeder that allows
the user to preset the arc voltage and wire feed speed.
The wire feed speed is internally monitored and regu-
CIRCUIT
BREAKER
INPUT
CONNECTOR
TO
CONTROL
BOARD
T1
TO
VOLTAGE
BOARD
METER
10VAC
BOARD
VOLTS
SPEED
SWITCH

POWER INPUT CIRCUITS

The 115VAC is applied (usually from the welding power
source) via the input connector and through the circuit
breaker and R1 resistor to the power board, the T2 trig-
ger transformer, and the T1 transformer.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

THEORY OF OPERATION

FIGURE E.2 – POWER INPUT CIRCUITS
GEAR
BOX
WIRE
FEED
MOTOR
POWER SOURCE OUTPUT TRIGGER (#2 &#4)
TRIGGER
T2
BOARD
TRIGGER
CONNECTOR
24VAC
R1
28VAC
THERMOSTAT
LN-9 Wire Feeder
lated to the preset condition. When the LN-9 is cou-
pled to an appropriate Lincoln constant voltage power
source, the arc voltage is also regulated to match the
preset voltage.
WORK VOLTAGE SENSING
ELECTRODE VOLTAGE SENSING
TACH
BOARD
WIRE SPEED CONTROL
+ 15VDC
TRIGGER SIGNAL
F
U
S
E
+ 15VDC
P
B
O
O
W
A
S
E R
H
U
D
R
T
D
O
W
N
WIRE FEED
MOTOR
TRIGGER SIGNAL
The 24VAC developed at the T2 trigger transformer is
applied to the trigger board. There it is rectified and
regulated to 20VDC and used to operate the wire feed-
er trigger circuitry.
The 28VAC produced by the T1 transformer secondary
is applied to the power board. There it is rectified and
regulated to 15VDC. This 15VDC powers the electron-
ics on the power, control, and voltage boards. The
10VAC secondary voltage is rectified, regulated, and
utilized by the meter board.
VOLTAGE CONTROL
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
A
E
G
N
C E
E
VOLTAGE
CONTROL
VOLTAGE
BOARD
GROUND
LEAD
PROTECTOR
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