ESAB MEK 4 Manuel utilisateur

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0740 800 085 Valid for serial no. 431--xxx--xxxx to 826--xxx--xxxx040426

MEK 4

Service manual

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LIST OF CONTENTS Page

READ THIS FIRST 2.......................................

COMPONENT DESCRIPTION 4.............................

WIRING DIAGRAM

Valid for serial no. 431--xxx--xxxx 5..........................

WIRING DIAGRAM

Valid for serial no. 514--xxx--xxxx to 826--xxx--xxxx 6............

DESCRIPTION OF OPERATION 7...........................

Design changes 7...........................................

1 Power supply 9.........................................

2 Activation, contactor 9...................................

3 Crater filling 10...........................................

4 Voltage adjustment 12....................................

5 Gas valve 14............................................

6 2--stroke / 4--stroke 15....................................

7 Burn--back time 15.......................................

8 Wire feed speed 16.......................................

9 Creep start / Normal start 17...............................

10 Motor driving / braking 18..................................

11 Tachometer input 19......................................

12 Current relay 19..........................................

13 Start / Stop 20...........................................

14 Processor 20............................................

15 Remote control input 21...................................

16 Digital display 22.........................................

TECHNICAL DATA 24.......................................

MAINTENANCE 24.........................................

SETTING THE WIRE FEED PRESSURE 25...................

CONTROL PANEL AND CONNECTIONS 26...................

ACCESSORIES 27.........................................

SPARE PARTS 28..........................................

NOTES 28.................................................

READ THIS FIRST

Maintenance and repair work should be performed by an experienced person, and electrical

work only by a trained electrician. Use only recommended replacement parts.

This service manual is intended for use by technicians with electrical/electronic training for

help in connection with fault--tracing and repair.

Use the wiring diagram as a form of index for the description of operation. The circuit

board is divided into numbered blocks, which are described individually in more detail in

the description of operation. All component names in the wiring diagram are listed in the

component description.

This manual contains details of all design changes that have been made up to and including

February 2003.

Rights reserved to alter specifications without notice.

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The MEK 4 wire feed unit is designed and tested in accordance with European

standard EN 60974--1 and EN 50199.

On completion of service or repair work, it is the responsibility of the person(s) etc.

performing the work to ensure that the product does not depart from the requirements

of the above standard.

WARNING !

STATIC ELECTRICITY can damage circuit

boards and electronic components.

SObserve precautions for handling electrostatic

sensitive devices.

SUse proper static--proof bags and boxes.

ESD

WARNING

READ AND UNDERSTAND THE INSTRUCTION MANUAL BEFORE INSTALLING OR OPERATING.

ARC WELDING AND CUTTING CAN BE INJURIOUS TO YOURSELF AND OTHERS. TAKE PRECAU-

TIONS WHEN WELDING. ASK FOR YOUR EMPLOYER’S SAFETY PRACTICES WHICH SHOULD BE

BASED ON MANUFACTURERS’ HAZARD DATA.

ELECTRIC SHOCK -- Can kill

SInstall and earth the welding unit in accordance with applicable standards.

SDo not touch live electrical parts or electrodes with bare skin, wet gloves or wet clothing.

SInsulate yourself from earth and the workpiece.

SEnsure your working stance is safe.

FUMES AND GASES -- Can be dangerous to health

SKeep your head out of the fumes.

SUse ventilation, extraction at the arc, or both, to keep fumes and gases from your breathing zone and

the general area.

ARC RAYS -- Can injure eyes and burn skin.

SProtect your eyes and body. Use the correct welding screen and filter lens and wear protective

clothing.

SProtect bystanders with suitable screens or curtains.

FIRE HAZARD

SSparks (spatter) can cause fire. Make sure therefore that there are no inflammable materials nearby.

NOISE -- Excessive noise can damage hearing

SProtect your ears. Use ear defenders or other hearing protection.

SWarn bystanders of the risk.

MALFUNCTION -- Call for expert assistance in the event of malfunction.

PROTECT YOURSELF AND OTHERS!

WARNING!

Rotating parts can cause injury, take great care

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COMPONENT DESCRIPTION

This component description refers to the wiring diagram.

AP01 Main circuit board with control electronics: see the description on

page 7.

AP02 Circuit board with display: see the description on page 22.

C01 Capacitor 0.1µF, decoupling.

CXX Capacitor 4700µF. Must be fitted when an intermediate wire feed unit is

in use in extreme applications (low mains voltage and long cables).

G01 Tachogenerator: 660 Hz output at a wire speed of 25 m/min. The

tachogenerator is incorporated in motor M01.

M01 Motor, rated voltage 42 V.

RP01 Potentiometer, 10 kΩ, for setting the wire feed speed.

RP02 Potentiometer, 10 kΩ, for setting the welding voltage.

RP03 Potentiometer, 10 kΩ, for setting the burn--back time.

RP04 Potentiometer, 10 kΩ, for setting the crater fill time.

SA01 Switch, 2/4--stroke changeover. When the switch is closed, 4--stroke

control mode is selected.

SA02 Switch, Crater fill function On/Off. When the switch is closed, crater fill

function is operative.

XP01 23--pole connector, for connection to the welding power unit.

XP02 Terminal for welding current connection from the power unit.

XS . . Connectors marked XS are socket connectors.

XS02 If circuit board AP01 has part no. 0486 205 880 or 0486 205 882:

the Creep Start function is operative when the connector links B01--B02.

If circuit board AP01 has part no. 0486 205 886 or 0487 166 880:

the Creep Start function is operative when the connector links B02--B03.

XS12 Not mounted, from machine number 514--615--xxxx

XS13 12--pole connector:

MEK 4 with serial number 431--xxx--xxxx

23--pole connector:

MEK 4 from serial number 514--xxx--xxxx and above.

YV01 Solenoid valve

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WIRING DIAGRAM Valid for serial no. 431--xxx--xxxx

MEK 4

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See page 17

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WIRING DIAGRAM Valid for serial no. 514--xxx--xxxx to 826--xxx--xxxx

MEK 4

See page 17

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DESCRIPTION OF OPERATION

Design changes

The following changes have been introduced, with effect from serial no. 514 . . . . . .

1. Remote control socket outlet XS13 has been changed from a 12--pole socket to a 23--pole

socket.

2. Power supply arrangements to the remote control unit have been changed. See items 4a,

4b and 8a, 8b in the Function Description. See also item 15b.

3. The power supply connections for the solenoid valve in the intermediate wire feed unit

have been changed from J and K to U and V. See items 5b and 15b in the Function

Description.

4. A new circuit board (486 205--882) replaces circuit board 486 205--880. It can be used

as a replacement part in all MEK 4 units. The following changes have been introduced

on the new board:

a. New program version, with modified creep start characteristics.

See items 9 and 14 in the Function Description.

b. Higher current limit for the motor, which improves acceleration and starting.

See item 10 in the Function Description.

c. The 0 VB voltage from the power unit is no longer galvanically isolated from 0 V in

the wire feed unit, in order to allow other remote control devices to be used. The

two neutrals are connected via diode D35.

See items 4a, 4b and 8a, 8b in the Function Description. See also the component

positions diagram.

5. The circuit board is now contained in a larger screened enclosure, item 227 in the Spare

Parts List. The guard for the screened enclosure and the wiring harness, item 228 in the

Spare Parts List, is also larger. However, when fitting the new circuit board in older

MEK 4 machines, it is not necessary to replace the screened enclosure or guard.

6. Actual voltage is now measured. This involves a new conductor, no. 613 in the wiring

diagram. It runs from the motor body (the welding wire) to connector XP01;H. This

connectionworksonlywithLAWpowerunitswithserialnumbers 512 ... .... and

above, or with modified LAW power units. Note that modifying LAW power units in-

volves fitting the new circuit board (486 291--880) and modifying the wiring in the

power unit.

7. A cooling water connection has been introduced as an accessory: see item 7 in the

Accessories List.

An adapter for a 5 kg bobbin is now available as an accessory: see item 8 in the

Accessories List.

8. The above changes have resulted in corresponding changes to the following points of the

Spare Parts List: 214, 215, 225, 226, 227 and 228.

The following change has been introduced, with effect from serial no. 514 615 ....

1. The cables 401, 402 and connector XS12 are not mounted in the machine. See item 11

in the Description of operation.

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** Circuit board 0486 205 880 is supplied with capacitor C35, on circuit board 0486 205 882

capacitor C35 is replaced by diode D35. See the description of operation, items 4a and 4b.

Component positions, circuit board AP01

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Sections 1--16 below refer to the /wiring diagrams on pages 5 and 6.

The circuit board is screened by a metal casing, connected to 0 V in the wire feed unit.

1 Power supply

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The wire feed unit receives 42 V from the control power supply transformer in the

welding power unit via connector XP01. LAW 400 and 500 welding power units

can supply a maximum of 6 A to the MEK 4. The wire feed unit’s own power

requirement at maximum load is 5 A.

42 V AC is supplied to the welding gun trigger switch, the gas valve and the

contactor. In addition, terminals G01 and G02 supply 42 V to a Miggytrac unit if

this is used together with the MEK 4.

DC power supplies

Diodes D30 -- D33 rectify the 42 V supply to 60 V. Capacitor C61 smooths the

supply, which is then used to power the wire feeder motor.

Transistor Q2 is a pre--regulator that drops the voltage from 60 V to 20 V. Q2 is

current--limited to about 200 mA.

VR1 and VR2 are voltage regulators, producing 5 V and 15 V respectively. The

circuit board’s microprocessor monitors the voltages. If the 15 V supply falls below

13 V, the wire feed unit is stopped.

2 Activation, contactor

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The welding power unit contactor is connected to the wire feed unit via pin F in

connector XP01. In the LAW 400/500 power units triac TC1 is loaded by a 1 kΩ

resistor.

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3 Crater filling

The crater fill function can be used when the MEK 4 is working

with a LAW power unit.

The crater fill function comprises the following modules :

SAn input for selecting crater fill function On/Off.

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Closing switch SA02 activates the function.

SPotentiometer RP04 sets the crater fill time.

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Times between 0 and 5.1 seconds can be set.

SAn output, XP01;W, which supplies a signal to the power unit when the voltage

is to be reduced for crater filling.

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The emitter of the transistor in optocoupler IC10 is connected to 0 VB, i.e. to

the neutral of the power unit voltage reference.

The crater fill function operates as follows :

Phase 1

When in 2--stroke control mode, releasing the welding gun trigger switch reduces the

wire feed speed to 84% of its original value. In 4--stroke control mode, crater filling

starts when the trigger switch is pressed for the second time. Optocoupler IC10 is

activated, supplying a signal to the power unit that crater filling has started, causing

the power unit to reduce its output voltage.

Phase 1 continues for a time as determined by the setting of potentiometer RP04, up

to a maximum of 1.27 seconds.

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