Lincoln Electric LF-72/74 Welder User Manual


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ELECTRICAL DIAGRAMS
G-6
LF-72/74
SCHEMATIC - ENTIRE MACHINE - CODE 11075, 11076, 11077 (G4617) LF-72
A
D
C
B
E
554
556
T
RIGGER
C
ONNECTOR
J4
559
515
558
COLD FEED
S1
FEED
PLATE
T
RIGGER
INPUT
67
556
J1-4
J1-5
J1-11
J1-12
J1-15
559
1
4
3
2
6
5
P5
8
7
M
OTOR /
GEARBOX
W
B
L5
515
558
589
5
87
554
551
550
5
51
550
576
577
575C
553
552
2
4
KEY
580
552A
605
606
601
607
608
515A
T
HERMAL LED
W
563
5
63
562
575B
562
B
W
B
P
9
12345678
50
51
41A
552C
10K/2W
2
1
P
7
4
3
REMOTE
CONTROL
V
OLTAGE
POTENTIOMETER
(OPTIONAL)
7
5A
7
6A
77A
W
IRE FEED
SPEED
CONTROL
P
OTENTIOMETER
1
0K/2W
1
4
3
2
6
5
5
75
5
77
5
76
589
TRIGGER
INTERLOCK
S2
5
87
-
+
5
80
42
552C
552A
4
1
4
1A
5
52B
TIMER KIT
(OPTIONAL)
S
CHEMATIC=
M
20336
J60-6
6
01
515A
605
607
608
606A
5
52
553
GAS
SOLENOID
OUTPUT
C
ONTROL
J6
2
C
4
D
77A
E
7
6A
F
7
5A
G
41
I
J
4
2
K
L
M
67
N
R
EMOTE
V
OLTAGE
C
ONTROL
SENSE
552B
A
RC VOLTAGE
A
RC CURRENT
51
50
2-STEP
GAS PURGE
L1
577A
5
76A
575A
7
5
7
6
77
L2
L3
5
75
5
75C
5
75B
2
4-42VAC
L4
562
5
63
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 @ 50 IPM
30.6V @ 800 IPM
M
otor is located
b
ehind
g
lastic panel
Lights when motor
c
urrent exceeds 4
Amps foran
extended time.
Plug for future
run-in kit.
Off = 0 VDC
OCV = 59 VDC
O
n = 7.7 VDC
Locatedon
CaseFront
Locatedon
CaseFront
Locatedon
CaseFront
L
ocatedon
case back
Values for CV300. 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.
1
5 VDC Open
0
VDC Closed
15 VDC Open
0 VDC Closed
Gearbox ratio is 2:47
Motor is atelectrode
p
otential
Locatedon
internalpanel
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
t
rigger depressed, welding will not start
until the trigger is released and then
depressed again.
T
o 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
(NOT ACTIVE)
0-5V PULSE SIGNAL
FREQUENCY = SPEED
J
1-9
J
1-13J1-3
100K
o
hm
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
J1-6
J
1-16
+POWER
COM
COM
BOARD
POWER
SUPPLY
J14-1
J
14-9
MOV
20
ohm
MACHINE
OUTPUT
ENABLE
20 OHM = OUTPUT ENABLED
HIGH IMPEDANCE = OUTPUT DISABLED
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.
• Monitors motor current, lights yellow thermal LED if over 4 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
J60-7J60-1
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
GENERATOR
A
c
5V SIGNAL
GAS FLOW
ENABLE
Locatedon
CaseFront
I
NPUT
OUTPUT
b
15V SIGNAL
100 msec PULSES
TOGGLE GAS FLOW ON/OFF
D
T
ime
r
B
oard 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 Flow Enable”signal.
• Outputs 100 msec pulses to turn Gas Flow On, Gas
Flow Off.
9
1
0
Locatedbehind
front panel
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 USEDNOT USED
C
onnectorlocated
by sheetpanel
Motor resistance
is 1.5 ohms
Connector located
behindcase front
P8
Connector located
behindcase front
Coil
measures
21 ohms
I
NDEX
M
OLEX
G-6
NOTE: This diagram is for reference only
. It may not be accurate for all machines covered by this manual.
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