Lincoln Electric LF-72/74 Welder User Manual


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ELECTRICAL DIAGRAMS
G-9
LF-72/74
SCHEMATIC - ENTIRE MACHINE - CODE 11195, 11196, 11197, (G4942) LF-74
A
D
C
B
E
554
556
T
RIGGER
C
ONNECTOR
J13
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
10
8
7
M
OTOR /
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
601
607
608
515A
THERMAL LED
1W
563
562
575B
562
1B
1W
1B
10K/2W
2
1
P7
4
3
REMOTE
C
ONTROL
VOLTAGE
POTENTIOMETER
(OPTIONAL)
7
5A
7
6A
77A
W
IRE FEED
S
PEED
C
ONTROL
P
OTENTIOMETER
1
0K/2W
589
TRIGGER
INTERLOCK
S2
587
-
+
580
4
2
5
52A
41
552B
TIMER KIT
(OPTIONAL)
S
CHEMATIC=
M20336
J60-6
6
01
5
15A
605
6
07
6
08
606A
552
5
53
GAS
SOLENOID
O
UTPUT
C
ONTROL
J12
2
C
4
D
7
7A
E
7
6A
F
7
5AG
4
1
I
J
42
K
L
M
6
7
N
REMOTE
V
OLTAGE
C
ONTROL
SENSE
552B
2-STEP
GAS PURGE
L1
577
5
76
5
75
7
5
7
6
77
L
2
L3
575
575C
575B
2
4-42VAC
L4
562
5
63
1
5 VDC in
2
STEP
position
5 VDC
when lit
3
8VDC at
42VAC input
with control
board
disconnected.
60VDC with
control board
connected
1
.6V @ 100 IPM
30.6V @ 800 IPM
Motor is located
behind
glastic panel
Lights when motor
current exceeds
3.75 Amps for an
extended time.
O
ff = 0 VDC
O
CV = 59 VDC
On = 7.7 VDC
Locatedon
CaseFront
Locatedon
CaseFront
Locatedon
CaseFront
Locatedon
case 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 MIN. WFS
Trigger Interlock does not
stop welding when the
arc is broken. Pull and
release trigger 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-74 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 this code of LF-74 is
100-800 ipm. The WFS range of the
LF-72 is 50-800 ipm.
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
0-5V PULSE SIGNAL
FREQUENCY = SPEED
J1-9
J
1-13J1-3
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
J1-6 J1-16
+POWER
C
OM
COM
BOARD
POWER
SUPPLY
J14-1
J
14-9
MOV
20
ohm
MACHINE
OUTPUT
ENABLE
J
14-8
J14-14
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
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
J
14-16
J
14-11
J
14-15
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.
J60-5 J60-8
J60-7J60-1
J60-3
+15V
COM
COM
BURNBACK
P
OT
PREFLOW &
P
OSTFLOWTIMER
L
OGIC
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
E
NABLE
Locatedon Case Front
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 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 USED
NOT USED
Connector located
b
y sheetpanel
Motor resistance
is 1.5 ohms
Connector located
behindcase front
Leads Pass through
toroid 2 times.
Coil
measures
21 ohms
INDEX
MOLEX
+5V
+15V
R
U
B
4
3
2
1
4
3
2
1
4
32
1
A
B
521
5
22
P
4
P11
P6
551A
521
522
5
51B
NORMAL
SPEED
4
32
1
A
B
HIGH
TORQUE
L6
5
51
Locatedon
CaseFront
Locatedon
C
ase Front
Locatedon
CaseFront
Locatedon
CaseBack
L
ocatedon
Sheet Panel
Leads
Pass
through
toroid 2
t
imes.
LeadsPass through
t
oroid 3 times.
Leads Pass
through
toroid 2 times.
5
51A
LeadsPass
t
hrough
toroid 2
times.
C
onnectorlocated
o
n sheetpanel
P11
Motor Connecter Summar
y
• High Torque Setting engages
Machine Select by connecting Pins 1
and 2 on Connector J2.
• High Torque not available on Normal
S
peed Model.
•
Normal Speed Setting not available
on High Torque Model.
20 OHM = OUTPUT ENABLED
HIGH IMPEDANCE = OUTPUT DISABLED
L
eadsPass
through
toroid 2
times.
5
63
40 pole
ring
magnet
5 VDC
284 pulses/sec @ 100 IPM
1139 pulses/sec @ 400 IPM
G-9
NOTE: This diagram is for reference only
. It may not be accurate for all machines covered by this manual.
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