Lincoln Electric LF-72/74 service manual High Torque Setting engages

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G-9	ELECTRICAL DIAGRAMS				G-9
SCHEMATIC - ENTIRE MACHINE - CODE 11195, 11196, 11197, (G4942) LF-74
	Values for CV300. Others
	may be different.
	0 VDC @ 0 = 5.8 Arc Volts
	6.6 VDC @ 10 = 40 ArcVolts
	75A	1	75	REMOTE	Located on
				CONTROL
	76A	2	76	10K/2W VOLTAGE	Case Front
	77A	3	77	POTENTIOMETER
				(OPTIONAL)
	Connector located	4
	behind case front
	284 pulses/sec @ 100 IPM	P7
	1139 pulses/sec @ 400 IPM

577

WIRE FEED

Located on

576

10K/2W

SPEED

575

Case Front

Connector located

Gearbox ratio is 2:47

CONTROL

Motor resistance

by sheet panel

Motor is at electrode

0 VDC MIN. WFS

POTENTIOMETER

is 1.5 ohms

Leads Pass through

potential

1

Motor is located

5 VDC MIN. WFS

575

toroid 2 times.

Off = 0 VDC

R

L4

2

40 pole

behind

OCV = 59 VDC

575B

563

3

U

ring

glastic panel

magnet

FEED

On = 7.7 VDC

575C

562

562

4

B

MOTOR /

PLATE

553

563

575B

5

5 VDC

GEARBOX

Located on

6

Coil

case back

551

7

B

To Power Source Electrode Connection

measures

550

8

W

21 ohms

GAS

P10

1.6V @ 100 IPM

SOLENOID

30.6V @ 800 IPM

552

67

552B

Leads Pass through

L2

TRIGGER

Located on

Case Front

toroid 3 times.

INPUT

Leads

556

A

Pass

B

through

554

TRIGGER

C

toroid 2

Located on Case Front

CONNECTOR

D

times.

J13

15V SIGNAL

b

D

Timer Board Summary

E

552B

100 msec PULSES

POSTFLOW

POSTFLOW

TOGGLE GAS FLOW ON/OFF

• Has potentiometers for burnback and postflow.

Located on

L5

TIME RANGE

Sheet Panel

.25 - 10 SEC

POT.

A

c

•

Preflow fixed at 30msec.

551

FIXED

c

D

5V SIGNAL

COM

• Burnback range is 0 to 0.25 sec.

GAS FLOW

Located on

PULSE

PREFLOW &

ENABLE

•

Postflow range is 0.25 to 10 sec.

WIDTH

Case Front

+

552A

POSTFLOW TIMER

OUTPUT

+15V

TIMER KIT

GENERATOR

LOGIC

INPUT

• Receives “Gas Flow Enable” signal.

PREFLOW

POT

SCHEMATIC =

THERMAL LED

Connector located

A

b

BURNBACK

(OPTIONAL)

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

-

on sheet panel

TIME FIXED

COM

J60-6

J60-5

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

M20336

Flow Off.

5 VDC

Lights when motor

AT 30msec

current exceeds

41

580

42

606A

when lit

1B

601

1W

3.75 Amps for an

522

605

608

607

Leads Pass

551A

515A

extended time.

through

521

551B

Motor Connecter Summary

1B

551A

J12

toroid 2 times.

L1

P4

1

2

3

4

P6

1

2

3

4

• High Torque Setting engages

Leads Pass

15 VDC Open

COLD FEED

NORMAL

Machine Select by connecting Pins 1

through

0 VDC Closed

Located on

J

SPEED

and 2 on Connector J2.

toroid 2

558

P11

1

2

3

4

P11

1

2

3

4

Case Front

L

• High Torque not available on Normal

times.

515A

S1

I

41

HIGH

515

24-42VAC

B

B

Speed Model.

K

42

L3

Located on

REMOTE

G

75A

TORQUE

• Normal Speed Setting not available

559

Leads Pass

Case Back

VOLTAGE

F

76A

A

on High Torque Model.

15 VDC Open

GAS PURGE

CONTROL

E

77A

575C

through

A

0 VDC Closed

SENSE

67

toroid 2

N

L6

576

562

times.

TRIGGER

M

563

INTERLOCK

OUTPUT

C

2

Located on

589

Case Front

CONTROL

D

4

556

20 OHM = OUTPUT ENABLED

MOLEX

587

S2

552

554

522

HIGH IMPEDANCE = OUTPUT DISABLED

INDEX

Trigger Interlock does not

38VDC at

552A

577

KEY

558

42VAC input

4

605

1W

589

2-STEP

stop welding when the

521

NOT USED

NOT USED

601

with control

580

553

A

2

606

608

607

515

559

587

15 VDC in

arc is broken. Pull and

board

release trigger to end the

550

disconnected.

2 STEP

weld.

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

MOV

ohm

Start-Up

COM

+5V

+5V

750 ohm

OPEN = 0V

MACHINE

CLOSED = 8V

TRIGGER

OUTPUT

On power-up, the LF-74 will light the

+15V

+15V

ENABLE

motor thermal LED for 0.5 seconds.

+5V

BOARD

POWER

MOTOR

If the feeder is powered-up with the

SUPPLY

VOLTAGE

trigger depressed, welding will not start

+ POWER

SENSE

0V = 0.02 SECONDS

until the trigger is released and then

DRIVE

BURNBACK

5V = 0.25 SECONDS

depressed again.

MOTOR

FET

DRIVE

Notes

BRAKE

CIRCUIT

COM

+5V

+15V

EXTERNAL

The WFS range of this code of LF-74 is

FET

LOW = CONTROL AT CONTROL BOARD

GAS

100-800 ipm. The WFS range of the

SOLENOID

HIGH = CONTROL AT TIMER BOARD

LF-72 is 50-800 ipm.

MOTOR

CONTROL

CURRENT

SENSE

MICRO

SCALING

Control Board Summary

0.1 ohm

CONTROLLER

• Has on-board power supply.

DO NOT USE

PROGRAM

NOT FIELD PROGRAMMABLE

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

0-5V PULSE SIGNAL

TACH

Interlock

FILTER

FEEDBACK

5V = OFF

200 ohm

•

Reads WFS potentiometer.

FREQUENCY = SPEED

THERMAL

4V OR LESS = ON

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

0V = MIN SPEED

LED

LOW = DISABLE

WIRE

• Controls motor speed with PWM.

5V = MAX SPEED

FEED

COLD

HIGH = ENABLE

• Turns Gas Solenoid on, off.

SPEED

FEED

• Reads the motor tachometer.

SOLENOID

200 ohm

LOW = DISABLE

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

GAS

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

FET

GAS

HIGH = ENABLE

0.25

SOLENOID

PURGE

to cool.

10K

ohm

• Does NOT support Run-in at this time.

ohm

•

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

TRIGGER

LOW = DISABLE

HIGH = ENABLE

be less when operating at 24 VAC.

INTERLOCK

• Does NOT operate on 115 VAC.

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