Lincoln Electric LF-72/74 Welder User Manual


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ELECTRICAL DIAGRAMS
G-8
LF-72/74
SCHEMATIC - ENTIRE MACHINE - CODE 11290, 11291, 11292,11293 (G4617-2) LF-72
A
D
C
B
E
554
556
TRIGGER
CONNECTOR
J
13
559
515
558
C
OLD FEED
S1
FEED
PLATE
TRIGGER
INPUT
67
556
J1-4
J1-5
J1-11
J1-12
J1-15
559
1
4
3
2
6
5
P10
8
7
MOTOR /
GEARBOX
W
B
L5
515
558
589
587
554
A
550
551
550
576
577
575C
553
552
2
4
KEY
580
552A
605
606
6
01
607
608
515A
THERMAL LED
1W
5
63
562
575B
562
1B
1W
1B
10K/2W
2
1
P
7
4
3
REMOTE
CONTROL
VOLTAGE
P
OTENTIOMETER
(OPTIONAL)
75A
76A
7
7A
WIRE FEED
SPEED
CONTROL
POTENTIOMETER
10K/2W
589
TRIGGER
I
NTERLOCK
S2
5
87
-
+
580
42
552A
4
1
552B
TIMER KIT
(OPTIONAL)
SCHEMATIC =
M20336
J60-6
601
515A
6
05
607
608
6
06A
5
52
553
G
AS
SOLENOID
OUTPUT
CONTROL
J12
2
C
4
D
7
7A
E
7
6A
F
7
5AG
41
I
J
4
2
K
L
M
67
N
R
EMOTE
V
OLTAGE
C
ONTROL
S
ENSE
5
52B
2
-STEP
G
AS PURGE
L1
5
77
576
5
75
75
76
7
7
L2
L3
5
75
575C
575B
2
4-42VAC
L4
5
62
563
15 VDC in
2 STEP
position
5
VDC
w
hen lit
38VDC at
42VAC input
with control
board
disconnected.
60VDC with
control board
connected
1.6V @ 100 IPM
3
0.6V @ 800 IPM
Motor is located
behind
glastic panel
L
ights when motor
current exceeds
3.75 Amps for an
extended time.
Off = 0 VDC
OCV = 59 VDC
O
n = 7.7 VDC
Locatedon
CaseFront
Locatedon
C
ase Front
Locatedon
CaseFront
Locatedon
c
ase back
Values for CV305. Others
may be different.
0 VDC @ 0 = 5.8 Arc Volts
6
.6 VDC @ 10 = 40 ArcVolts
0 VDC MIN. WFS
5
VDC MIN. 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
15 VDC Open
0
VDC Closed
Gearbox ratio is 2:47
Motor is atelectrode
potential
Start-Up
On power-up, the LF-72 will light the motor
thermal LED for 0.5 seconds.
If the feeder is powered-up with the trigger
depressed, welding will not start until the
trigger is released and then depressed
again.
Notes
The WFS range of the LF-72 is 50-800 ipm.
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
J
1-1
+5V
FILTER
TACH
FEEDBACK
0-5V PULSE SIGNAL
FREQUENCY = SPEED
J
1-9
J1-13J1-3
100K
ohm
WIRE
FEED
SPEED
0V = MIN SPEED
5V = MAX SPEED
+5V
J1-8
200 ohm
GAS
SOLENOID
SOLENOID
FET
10K
ohm
0.25
ohm
J1-2
J
1-6
J
1-16
+POWER
COM
COM
BOARD
POWER
SUPPLY
J14-1
J
14-9
MOV
20
ohm
MACHINE
OUTPUT
ENABLE
J14-8
J
14-14
J14-2
J
14-5
+5V
BURNBACK
0V = 0.02 SECONDS
5V = 0.25 SECONDS
J
14-4
EXTERNAL
GAS
SOLENOID
CONTROL
LOW = CONTROL AT CONTROL BOARD
HIGH = CONTROL AT TIMER BOARD
J14-12 J14-13
PROGRAM
DO NOT USE
NOT FIELD PROGRAMMABLE
J
14-7
200 ohm
THERMAL
LED
5V = OFF
4V OR LESS = ON
J
14-10
COLD
FEED
LOW = DISABLE
HIGH = ENABLE
J
14-16
J
14-11
J14-15
J14-3
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.
• Reads the motor tachometer.
• 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 atthis time.
• Operates on 24-42 VAC. Maximum WFS and/ormaximum pull forcemay
be less when operating at 24 VAC.
• Does NOT operate on 115 VAC.
J
60-5 J60-8
J60-7J60-1
J60-3
+15V
COM
COM
B
URNBACK
POT
PREFLOW &
P
OSTFLOWTIMER
LOGIC
POSTFLOW
POT.
A
b
PREFLOW
TIME FIXED
AT 30msec
c
D
POSTFLOW
T
IME RANGE
.25 - 10 SEC
FIXED
PULSE
WIDTH
GENERATOR
A
c
5
V SIGNAL
G
AS FLOW
E
NABLE
Locatedon Case Front
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 0.25to 10 sec.
• Receives “Gas Flow Enable”signal.
•
Outputs 100 msec pulses to turnGas Flow On, Gas
F
low Off.
J
2-1
J
2-2
J
2-3
J
2-4
J
2-5
J
2-6
J
3-1
J
3-2
NOT USED
NOT USED
Connector located
by sheetpanel
M
otor resistance
is 1.5 ohms
Connector located
behindcase front
Leads Pass through
toroid 2 times.
C
oil
measures
21 ohms
I
NDEX
MOLEX
+5V
+15V
R
U
B
4
3
2
1
4
32
1
4
32
1
A
B
5
21
5
22
P4
P11
P6
5
21
5
22
551B
L6
551
Locatedon
C
ase Front
Locatedon
CaseFront
Locatedon
CaseFront
L
ocatedon
CaseBack
Locatedon
Sheet Panel
L
eads
Pass
through
toroid 2
times.
LeadsPass through
toroid 3 times.
Leads Pass
through
toroid 2 times.
551A
LeadsPass
through
toroid 2
times.
C
onnectorlocated
behindsheet panel
M
otor Connecte
r
S
ummar
y
• P6 not used – required for LF-74
only..
20 OHM = OUTPUT ENABLED
HIGH IMPEDANCE = OUTPUT DISABLED
LeadsPass
through
toroid 2
times.
5
63
Connector located
on sheetpanel
G-8
NOTE: This diagram is for reference only
. It may not be accurate for all machines covered by this manual.
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