Lincoln Electric LF-72/74 service manual Internal panel

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G-7

ELECTRICAL DIAGRAMS

G-7

SCHEMATIC - ENTIRE MACHINE - CODE 11209, 11210, 11211,11227 (G4617-1) LF-72

Values for CV300. Others

may be different.

0 VDC @ 0 = 5.8 Arc Volts

6.6 VDC @ 10 = 40 ArcVolts

75A

1

75

REMOTE

CONTROL

76A

2

76

10K/2W

VOLTAGE

77A

3

77

POTENTIOMETER

(OPTIONAL)

Connector located

4

behind case front

P7

577

3

577A

WIRE FEED

576

2

576A

10K/2W

575

1

575A

SPEED

Connector located

Gearbox ratio is 2:47

CONTROL

Motor resistance

4

by sheet panel

Motor is at electrode

0 VDC MIN. WFS

POTENTIOMETER

is 1.5 ohms

5

potential

1

6

5 VDC MAX. WFS

575

Motor is located

Off = 0 VDC

L4

2

behind

P8

OCV = 59 VDC

575B

563

3

glastic panel

FEED

On = 7.7 VDC

575C

562

562

4

MOTOR /

Connector located

563

PLATE

behind case front

575B

5

GEARBOX

553

Located on

6

Coil

case back

551

7

B

To Power Source Electrode Connection

measures

550

8

W

21 ohms

GAS

P5

1.6V @ 50 IPM

SOLENOID

30.6V @ 800 IPM

552

67

552B

L2

TRIGGER

INPUT

556

A

554

B

TRIGGER

C

CONNECTOR

D

J4

15V SIGNAL

b

E

552B

D 100 msec PULSES

POSTFLOW

TOGGLE GAS FLOW ON/OFF

Located on

POSTFLOW

internal panel

TIME RANGE

POT.

.25 - 10 SEC

A

c

FIXED

c

D

5V SIGNAL

COM

GAS FLOW

PULSE

PREFLOW &

ENABLE

Located on

Start-Up

WIDTH

+

552A

GENERATOR

POSTFLOW TIMER

OUTPUT

+15V

TIMER KIT

Case Front

On power-up, the LF-72 will light the

LOGIC

POT

INPUT

PREFLOW

SCHEMATIC =

THERMAL LED

motor thermal LED for 0.5 seconds.

A

b

BURNBACK

(OPTIONAL)

-

L5

TIME FIXED

COM

J60-6

J60-8 J60-7 J60-1 J60-3

M20336

Lights when motor

If the feeder is powered-up with the

J60-5

5

VDC

AT 30msec

current exceeds 4

trigger depressed, welding will not start

41

580

42

Located on

606A

when lit

B

601

W Amps for an

until the trigger is released and then

Timer Board Summary

608

Case Front

605

607

515A

extended time.

depressed again.

• Has potentiometers for burnback and postflow.

B

J6

L1

•

Preflow fixed at 30msec.

15 VDC Open

COLD FEED

• Burnback range is 0 to 0.25 sec.

0 VDC Closed

Located on

ARC CURRENT

J

• Postflow range is 0.25 to 10 sec.

558

Case Front

ARC VOLTAGE

L

• Receives “Gas Flow Enable” signal.

515A

S1

I

41

515

24-42VAC

K

42

• Outputs 100 msec pulses to turn Gas Flow On, Gas

L3

559

G

75A

Flow Off.

REMOTE

VOLTAGE

F

76A

15 VDC Open

GAS PURGE

CONTROL

E

77A

0 VDC Closed

SENSE

67

20 OHM = OUTPUT ENABLED

N

TRIGGER

HIGH IMPEDANCE = OUTPUT DISABLED

M

INTERLOCK

OUTPUT

C

2

Located on

589

Case Front

CONTROL

D

4

575C

MOLEX

587

S2

552

INDEX

Trigger Interlock does not

38VDC at

576

552A

563

KEY

558

42VAC input

577

551

556

4

605

W

589

2-STEP

stop welding when the

NOT USED

NOT USED

601

550

554

with control

580

553

562

2

606

608

607

515

559

587

15 VDC in

arc is broken. Pull and

board

release to end the weld.

disconnected.

2 STEP

position

60VDC with

J1-2

J1-6

J1-16

J1-8

J1-3 J1-13

J1-9 J1-1 J1-15

J1-12 J1-5

J1-11

J1-4

+15V

J2-1 J2-2 J2-3

J2-4 J2-5

J2-6

J3-1 J3-2

J14-1 J14-9

J14-8

J14-14

J14-2 J14-5 J14-4

J14-12 J14-13

J14-7

J14-10

J14-16

J14-11

J14-15

J14-3

control board

750 ohm

+15V

connected

+POWER

100K

20

ohm

OPEN = 0V

MOV

ohm

+5V

+5V

750 ohm

COM

MACHINE

CLOSED = 8V

TRIGGER

OUTPUT

+15V

+15V

ENABLE

BOARD

+5V

POWER

MOTOR

SUPPLY

VOLTAGE

Control Board Summary

+ POWER

SENSE

0V = 0.02 SECONDS

BURNBACK

5V = 0.25 SECONDS

• Has on-board power supply.

DRIVE

MOTOR

• Receives switch signals from Trigger, Cold Feed, Gas Purge, Trigger

FET

DRIVE

Interlock

BRAKE

CIRCUIT

EXTERNAL

•

Reads WFS potentiometer.

COM

+5V

+15V

FET

LOW = CONTROL AT CONTROL BOARD

GAS

• Communicates with optional timer kit to control burnback, postflow.

SOLENOID HIGH = CONTROL AT TIMER BOARD

• Controls motor speed with PWM.

MOTOR

CONTROL

• Turns Gas Solenoid on, off.

CURRENT

SENSE

MICRO

• Monitors motor current, lights yellow thermal LED if over 3.75 amps for an

SCALING

0.1 ohm

CONTROLLER

extended time period. LED remains lit for 30 – 60 seconds to allow motor

DO NOT USE

to cool.

PROGRAM

NOT FIELD PROGRAMMABLE

• Does NOT support Run-in at this time.

0-5V PULSE SIGNAL

TACH

•

Operates on 24-42 VAC. Maximum WFS and/or maximum pull force may

FILTER

FEEDBACK

5V = OFF

200 ohm

FREQUENCY = SPEED

(NOT ACTIVE) THERMAL

be less when operating at 24 VAC.

4V OR LESS = ON

LED

• Does NOT operate on 115 VAC.

0V = MIN SPEED

LOW = DISABLE

WIRE

5V = MAX SPEED

FEED

COLD

HIGH = ENABLE

SPEED

FEED

SOLENOID

200 ohm

GAS

LOW = DISABLE

FET

GAS

HIGH = ENABLE

SOLENOID

PURGE

0.25

10K

ohm

ohm

TRIGGER

LOW = DISABLE

HIGH = ENABLE

INTERLOCK

COMMON ANALOG P.C. BOARD

SCHEMATIC = G4559

NOTE: This diagram is for reference only. It may not be accurate for all machines covered by this manual.

LF-72/74