Lincoln Electric LF-72/74 Welder User Manual


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ELECTRICAL DIAGRAMS
G-7
LF-72/74
SCHEMATIC - ENTIRE MACHINE - CODE 11209, 11210, 11211,11227 (G4617-1) LF-72
A
D
C
B
E
554
556
TRIGGER
C
ONNECTOR
J4
559
515
558
COLD FEED
S1
FEED
PLATE
T
RIGGER
I
NPUT
67
556
J1-4
J1-5
J1-11
J1-12
J1-15
559
1
4
3
2
6
5
P
5
8
7
M
OTOR /
G
EARBOX
W
B
L5
515
558
589
587
554
551
550
551
550
576
577
575C
553
552
2
4
KEY
580
552A
605
606
601
607
608
5
15A
THERMAL LED
W
563
563
562
575B
562
B
W
B
1
0K/2W
2
1
P7
4
3
REMOTE
C
ONTROL
VOLTAGE
POTENTIOMETER
(OPTIONAL)
75A
76A
7
7A
WIRE FEED
S
PEED
C
ONTROL
POTENTIOMETER
10K/2W
1
4
3
2
6
5
575
5
77
5
76
5
89
TRIGGER
INTERLOCK
S2
587
-
+
580
4
2
5
52A
41
5
52B
T
IMER KIT
(
OPTIONAL)
SCHEMATIC =
M20336
J60-6
601
5
15A
6
05
607
608
606A
5
52
553
G
AS
S
OLENOID
O
UTPUT
CONTROL
J6
2
C
4
D
77AE
76A
F
75AG
4
1
I
J
42
K
L
M
6
7
N
R
EMOTE
V
OLTAGE
CONTROL
S
ENSE
5
52B
ARC VOLTAGE
ARC CURRENT
2-STEP
GAS PURGE
L
1
5
77A
576A
575A
75
76
7
7
L
2
L3
575
5
75C
5
75B
24-42VAC
L4
5
62
563
15 VDC in
2 STEP
p
osition
5
VDC
when lit
38VDC at
42VAC input
w
ith control
board
disconnected.
60VDC with
control board
connected
1.6V @ 50 IPM
30.6V @ 800 IPM
Motor is located
behind
glastic panel
Lights when motor
current exceeds 4
Amps foran
extended time.
O
ff = 0 VDC
O
CV = 59 VDC
On = 7.7 VDC
Locatedon
CaseFront
Locatedon
C
ase Front
Locatedon
CaseFront
Locatedon
c
ase back
Values for CV300. Others
m
ay be different.
0 VDC @ 0 = 5.8 Arc Volts
6.6 VDC @ 10 = 40 ArcVolts
0 VDC MIN. WFS
5 VDC MAX. WFS
Trigger Interlock does not
stop welding when the
arc is broken. Pull and
release to end the weld.
15 VDC Open
0 VDC Closed
1
5 VDC Open
0 VDC Closed
Gearbox ratio is 2:47
Motor is atelectrode
p
otential
Locatedon
i
nternalpanel
Start-Up
On power-up, the LF-72 will light the
motor thermal LED for 0.5 seconds.
I
f the feeder is powered-up with the
trigger depressed, welding will not start
until the trigger is released and then
depressed again.
To Power Source Electrode Connection
750 ohm
+15V
750 ohm
TRIGGER
OPEN = 0V
CLOSED = 8V
MOTOR
CURRENT
SENSE
SCALING
MOTOR
VOLTAGE
SENSE
BRAKE
FET
DRIVE
FET
0.1 ohm
MOTOR
DRIVE
CIRCUIT
+ POWER
J1-1
+5V
FILTER
TACH
FEEDBACK
(NOT ACTIVE)
0-5V PULSE SIGNAL
FREQUENCY = SPEED
J1-9
J1-13J1-3
100K
ohm
WIRE
FEED
SPEED
0V = MIN SPEED
5V = MAX SPEED
+5V
J
1-8
200 ohm
GAS
SOLENOID
SOLENOID
FET
10K
ohm
0.25
ohm
J
1-2
J
1-6
J1-16
+POWER
COM
COM
BOARD
POWER
SUPPLY
J
14-1
J14-9
MOV
20
ohm
MACHINE
OUTPUT
ENABLE
20 OHM = OUTPUT ENABLED
HIGH IMPEDANCE = OUTPUT DISABLED
J
14-8
J14-14
J
14-2
J14-5
+5V
BURNBACK
0V = 0.02 SECONDS
5V = 0.25 SECONDS
J14-4
EXTERNAL
GAS
SOLENOID
CONTROL
LOW = CONTROL AT CONTROL BOARD
HIGH = CONTROL AT TIMER BOARD
J
14-12
J
14-13
PROGRAM
DO NOT USE
NOT FIELD PROGRAMMABLE
J14-7
200 ohm
THERMAL
LED
5V = OFF
4V OR LESS = ON
J14-10
COLD
FEED
LOW = DISABLE
HIGH = ENABLE
J14-16 J14-11
J
14-15
J
14-3
GAS
PURGE
LOW = DISABLE
HIGH = ENABLE
+15V +15V
TRIGGER
INTERLOCK
LOW = DISABLE
HIGH = ENABLE
+15V
MICRO
CONTROLLER
COMMON ANALOG P.C. BOARD
SCHEMATIC =G4559
Control Board Summar
y
• Has on-board power supply.
• Receives switch signals from Trigger, Cold Feed, Gas Purge, Trigger
Interlock
• Reads WFS potentiometer.
• Communicates with optional timer kit to control burnback, postflow.
• Controls motor speed with PWM.
• Turns Gas Solenoid on, off.
• Monitors motor current, lights yellow thermal LED if over 3.75 amps for an
extended time period. LED remains lit for 30 – 60 seconds to allow motor
to cool.
•
Does NOT support Run-in at this time.
• Operates on 24-42 VAC. Maximum WFS and/or maximum pull force may
be less when operating at 24 VAC.
• Does NOT operate on 115 VAC.
J60-5 J60-8
J
60-7J60-1
J60-3
+15V
COM
COM
BURNBACK
POT
PREFLOW &
POSTFLOWTIMER
LOGIC
POSTFLOW
POT.
A
b
PREFLOW
TIME FIXED
AT 30msec
c
D
POSTFLOW
TIME RANGE
.25 - 10 SEC
FIXED
PULSE
WIDTH
G
ENERATOR
A
c
5V SIGNAL
GAS FLOW
ENABLE
Locatedon
CaseFront
I
NPUT
OUTPUT
b
15V SIGNAL
100 msec PULSES
TOGGLE GAS FLOW ON/OFF
D
Time
r
Board Summar
y
• Has potentiometers for burnback and postflow.
• Preflow fixed at 30msec.
• Burnback range is 0 to 0.25sec.
• Postflow range is 0.25 to 10sec.
•
Receives “Gas FlowEnable” signal.
• Outputs 100 msec pulses to turn Gas Flow On, Gas
Flow Off.
J2-1 J2-2 J2-3 J2-4 J2-5 J2-6 J3-1 J3-2
NOT USEDNOT USED
C
onnectorlocated
by sheetpanel
Motor resistance
is 1.5 ohms
Connector located
behindcase front
P8
Connector located
b
ehindcase front
C
oil
measures
21 ohms
INDEX
MOLEX
+5V
+15V
G-7
NOTE: This diagram is for reference only
. It may not be accurate for all machines covered by this manual.
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