MAXSTAR140STR (KK013519)

Maxstar 140 STRWith Auto-Link AndRemote Receptacle

Processes

Description

TIG (GTAW) Welding

Stick (SMAW) Welding

Arc Welding Power Source

TM-2224A February 2002Eff. w/Serial Number KK013000

Visit our website atwww.MillerWelds.com

The following terms areused interchangeablythroughout this manual:TIG = GTAWStick = SMAW

TABLE OF CONTENTSSECTION 1 SAFETY PRECAUTIONS FOR SERVICING 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1. Symbol Usage 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2. Servicing Hazards 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3. EMF Information 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 2 SPECIFICATIONS AND INSTALLATION 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1. Specifications 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2. Description 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3. Included with Your Unit (Stick Only) 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4. Included with Your Unit (TIG / Stick) 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5. Duty Cycle And Overheating 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6. Volt-Ampere Curves 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7. Selecting A Location 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8. Typical Connection Methods 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9. Connecting To Weld Output Receptacles 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10. Connecting Remote Control To Remote Receptacle (For Lift-ArcE TIG Only) 8. . . . . . . . . . . . 2-11. Rear Panel And Power Switch 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12. Connecting Input Power 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14. Installing 230 Volts Ac Input Power Cord 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15. Remote Receptacle Information (For Lift-ArcE TIG Only) 11. . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 3 OPERATION 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1. Front Panel Controls 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2. Lift-Arct TIG Procedure 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 4 HOW AN INVERTER WORKS 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SECTION 5 THEORY OF OPERATION 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SECTION 6 PRE-POWER CHECKLIST 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6-1. Checking Unit Before Applying Power 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2. Output Rectifier SR2 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3. Varistor 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4. Power Switch S1 18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 7 EXPLANATION OF ELECTRICAL PARTS 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SECTION 8 TROUBLESHOOTING 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1. Troubleshooting 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2. Troubleshooting Circuit Diagram 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 9 MAINTENANCE 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1. Routine Maintenance 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2. Blowing Out Inside Of Unit 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3. Measuring Input Capacitor Voltage 27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 10 ELECTRICAL DIAGRAM 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SECTION 11 STICK WELDING (SMAW) GUIDELINES 31. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SECTION 12 SELECTING AND PREPARINGTUNGSTEN ELECTRODE 39. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12-1. Selecting Tungsten Electrode 39. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2. Safety Information About Tungsten 39. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3. Preparing Tungsten For DC Electrode Negative (DCEN) Welding 40. . . . . . . . . . . . . . . . . . . . .

SECTION 13 GUIDELINES FOR TIG WELDING (GTAW) 41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1. Positioning The Torch 41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-2. Torch Movement During Welding 42. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3. Positioning Torch Tungsten For Various Weld Joints 43. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 14 PARTS LIST 46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

WARNINGThis product, when usedfor welding or cutting,produces fumes orgases which containchemicals known to theState of California tocause birth defects and,in some cases, cancer.(California Health &Safety Code Section25249.5 et seq.)

TM-2224 Page 1Maxstar 140 STR

SECTION 1 SAFETY PRECAUTIONS FOR SERVICING1-1. Symbol Usage

OM-2224F - 3/02, safety_stm 7/98

Means Warning! Watch Out! There are possible hazardswith this procedure! The possible hazards are shown inthe adjoining symbols.

Marks a special safety message.

Means Note; not safety related.

This group of symbols means Warning! Watch Out! possibleELECTRIC SHOCK, MOVING PARTS, and HOT PARTS hazards.Consult symbols and related instructions below for necessary actionsto avoid the hazards.

1-2. Servicing Hazards

The symbols shown below are used throughout this manual tocall attention to and identify possible hazards. When you seethe symbol, watch out, and follow the related instructions toavoid the hazard.

Only qualified persons should service, test, maintain, and re-pair this unit.

During servicing, keep everybody, especially children, away.

ELECTRIC SHOCK can kill.

Do not touch live electrical parts. Turn Off welding power source and wire feeder

and disconnect and lockout input power usingline disconnect switch, circuit breakers, or by removing plug from re-ceptacle, or stop engine before servicing unless the procedure spe-cifically requires an energized unit.

Insulate yourself from ground by standing or working on dry insulat-ing mats big enough to prevent contact with the ground.

Do not leave live unit unattended.

If this procedure requires an energized unit, have only personnelfamiliar with and following standard safety practices do the job.

When testing a live unit, use the one-hand method. Do not put bothhands inside unit. Keep one hand free.

Disconnect input power conductors from deenergized supply lineBEFORE moving a welding power source.

SIGNIFICANT DC VOLTAGE exists after removal ofinput power on inverters. Turn Off inverter, disconnect input power, and discharge input

capacitors according to instructions in Maintenance Section beforetouching any parts.

STATIC (ESD) can damage PC boards. Put on grounded wrist strap BEFORE handling

boards or parts. Use proper static-proof bags and boxes to

store, move, or ship PC boards.

FIRE OR EXPLOSION hazard. Do not place unit on, over, or near combustible

surfaces. Do not service unit near flammables.

FLYING METAL can injure eyes. Wear safety glasses with side shields or face

shield during servicing. Be careful not to short metal tools, parts, or

wires together during testing and servicing.

HOT PARTS can cause severe burns. Do not touch hot parts bare handed. Allow cooling period before working on welding

gun or torch.

EXPLODING PARTS can cause injury. Failed parts can explode or cause other parts to

explode when power is applied to inverters. Always wear a face shield and long sleeves

when servicing inverters.

SHOCK HAZARD from testing. Turn Off welding power source and wire feeder

or stop engine before making or changing me-ter lead connections.

Use at least one meter lead that has a self-retaining spring clip such as an alligator clip.

Read instructions for test equipment.

FALLING UNIT can cause injury. Use lifting eye to lift unit only, NOT running

gear, gas cylinders, or any other accessories. Use equipment of adequate capacity to lift and

support unit. If using lift forks to move unit, be sure forks are

long enough to extend beyond opposite side ofunit.

MOVING PARTS can cause injury. Keep away from moving parts such as fans. Keep all doors, panels, covers, and guards

closed and securely in place.

TM-2224 Page 2 Maxstar 140 STR

MOVING PARTS can cause injury. Keep away from moving parts. Keep away from pinch points such as drive

rolls.

MAGNETIC FIELDS can affect pacemak-ers.

Pacemaker wearers keep away from servicingareas until consulting your doctor.

OVERUSE can cause OVER-HEATING. Allow cooling period; follow rated duty cycle. Reduce current or reduce duty cycle before

starting to weld again. Do not block or filter airflow to unit.

H.F. RADIATION can cause interference.

High-frequency (H.F.) can interfere with radionavigation, safety services, computers, andcommunications equipment.

Have only qualified persons familiar withelectronic equipment install, test, and serviceH.F. producing units.

The user is responsible for having a qualified electrician prompt-ly correct any interference problem resulting from the installa-tion.

If notified by the FCC about interference, stop using theequipment at once.

Have the installation regularly checked and maintained. Keep high-frequency source doors and panels tightly shut, keep

spark gaps at correct setting, and use grounding and shielding tominimize the possibility of interference.

READ INSTRUCTIONS. Use Testing Booklet (Part No. 150 853) when

servicing this unit. Consult the Owners Manual for welding safety

precautions. Use only genuine replacement parts.

1-3. EMF InformationConsiderations About Welding And The Effects Of Low FrequencyElectric And Magnetic FieldsWelding current, as it flows through welding cables, will cause electro-magnetic fields. There has been and still is some concern about suchfields. However, after examining more than 500 studies spanning 17years of research, a special blue ribbon committee of the NationalResearch Council concluded that: The body of evidence, in thecommittees judgment, has not demonstrated that exposure to power-frequency electric and magnetic fields is a human-health hazard.However, studies are still going forth and evidence continues to beexamined. Until the final conclusions of the research are reached, youmay wish to minimize your exposure to electromagnetic fields whenwelding or cutting.To reduce magnetic fields in the workplace, use the followingprocedures:

1. Keep cables close together by twisting or taping them.

2. Arrange cables to one side and away from the operator.

3. Do not coil or drape cables around your body.

4. Keep welding power source and cables as far away from opera-tor as practical.

5. Connect work clamp to workpiece as close to the weld as possi-ble.

About Pacemakers:Pacemaker wearers consult your doctor first. If cleared by your doctor,then following the above procedures is recommended.


SECTION 2 SPECIFICATIONS AND INSTALLATION2-1. Specifications

InputPowerSingle-Phase

AC

Rated WeldingOutput

WeldingAmperage

Range

MaximumOpen-CircuitVoltage DC

AmperesInput AtRated

Load Out-put,

50/60Hz,Single-Phase

KVAAT

100%DutyCyc.

KW Dimensions Weight

115Volts

80A @ 23.2 VoltsDC, 100% Duty

Cycle5 110A 93V 31 3.5 2.24 H: 8 in (203 mm)

10 lb

230Volts

100A @ 24 VoltsDC, 100% Duty

Cycle5 140A 93V 23 5.3 2.76

W: 4-5/16 in (110 mm)L: 12-1/4 in (311 mm)

10 lb(4.5 kg)

2-2. Description

Ref. ST-802 385-A

1 Welding Power SourceThis unit is a compact, light weight,portable welding power sourcecontaining the latest high perfor-mance electronics that supplies DCweld output for use with the StickElectrode and TIG welding pro-cesses.

This unit also has a carrying strapand quick-disconnect weld outputreceptacles to aid portability and toencourage use wherever the jobmay be located. Because of itselectronic design, this unit con-sumes only modest amounts of in-put power and provides superb arccharacteristics. Further, it is easyto install and simple to operate. Thiswelding power source is equippedwith the advanced Auto-Link cir-cuitry which automatically adjuststhe unit to operate from the avail-able input voltage without makingany internal changes. The circuitryworks with either 115 or 230 voltsinput power.

1


2-3. Included with Your Unit (Stick Only)1 Shoulder Strap (Carrying

Strap)2 13 ft (4 m) Cable With

Electrode Holder andQuick-Connect Plug

3 10 ft (3 m) Cable WithWork Clamp AndQuick-Connect Plug

4 6 ft (1.8 m) 115 VAC InputPower Cord With 20 A Plug

Some assembly is required.For options and accessories,contact your distributor.

1

2

3

4

Ref. ST-802 387-A

2-4. Included with Your Unit (TIG / Stick)1 Shoulder Strap (Carrying

Strap)2 12 ft (3.6 m) Gas Hose /

Coupler And Inert GasRegulator / Flowmeter

3 10 ft (3 m) Cable WithWork Clamp AndQuick-Connect Plug

4 12 ft (3.6 m) TIG TorchWith valve andQuick-Connect Plug

5 13 ft (4 m) Cable WithElectrode Holder andQuick-Connect Plug

6 6 ft (1.8 m) 115 VAC InputPower Cord With 20 A Plug

Some assembly is required.For options and accessories,contact your distributor.

1

23

4

ST-802 387A / ST-802 0205

6


2-5. Duty Cycle And Overheating

193 116

Duty Cycle is percentage of 10 min-utes that unit can weld at rated loadwithout overheating.If unit overheats, output stops, theOvertemperature Light comes On,and the cooling fan runs. Wait fif-teen minutes for unit to cool. Re-duce amperage or voltage or dutycycle before starting to weld again. Exceeding duty cycle can

damage unit and voidwarranty.

110 A @ 35% Duty Cycle (115 V Input)140 A @ 25% Duty Cycle (230 V Input)

Overheating0

15

A or V

ORReduce Duty CycleMinutes

3-1/2 Minutes Welding 6-1/2 Minutes Resting

35% duty cycle for 115 vac

Continuous Welding

100%dutycycle

80 A @ 100% Duty Cycle (115 V Input)100 A @ 100% Duty Cycle (230 V Input)

2-1/2 Minutes Welding 7-1/2 Minutes Resting

25% duty cycle for 230 vac


2-6. Volt-Ampere Curves

193 117-115V / 193 117-230V

Volt-ampere curves show minimumand maximum voltage and amper-age output capabilities of weldingpower source. Curves of other set-tings fall between curves shown.

115 VAC INPUT

230 VAC INPUT

TIG and Stick Max.

Stick Min.TIG Min.

TIG and Stick Max.

Stick Min. TIG Min.


2-7. Selecting A Location1 Welding Power SourceUse shoulder strap to lift and moveunit.2 Rating LabelLabel is located on side of unit. Userating label to determine input pow-er needs. Special installation may be

required where gasoline orvolatile liquids are present see NEC Article 511 or CECSection 20.

2Airflow DistanceRequirements

18 in(460 mm)

18 in(460 mm)

ST-801 956-A / Ref. ST-802 385-A / 193 623-A

1

Do not move or operate unitwhere it could tip.

ETP-1400-PDF

Turn Off welder before mak-ing connections.

1 Stick Connections2 TIG ConnectionsObtain gas cylinder and proper TIGtorch from your distributor.

2

2-8. Typical Connection Methods

Typical TIG Connections And Equipment

Typical StickConnections

1


Turn Off welder before mak-ing connections.

1 Negative () Weld OutputReceptacle

2 Positive (+) Weld OutputReceptacle

3 ConnectorsFor TIG Welding (Electrode Nega-tive), connect work cable connectorto positive (+) receptacle and TIGTorch cable connector to negative() receptacle.For STICK Welding (ElectrodePositive), connect work cable con-nector to negative () receptacleand Electrode Holder cable con-nector to positive (+) receptacle.To connect to receptacle, align key-way, insert connector, and turnclockwise (approximately 1/2 turn)..

Ref. ST-802 385-A

1

3

2-9. Connecting To Weld Output Receptacles

2

2-10. Connecting Remote Control To Remote Receptacle (For Lift-Arc TIG Only)

ST-802 385-A

1 Remote Control PlugTo tighten, insert plug into recep-tacle and turn collar clockwise 90.

Connecting a remote controlautomatically places the ma-chine in Lift-Arc TIG regardlessof front panel setting.

1

2-11. Rear Panel And Power Switch

Ref. ST-802 385

1 Rear Panel2 Power On/Off SwitchRotate the Power Switch to the On(l) or Off (0) position as needed ac-cording to the markings on the rearpanel.3 Input Power Cord

2

1

3


The welder is shipped with a115 VAC 20 amp input powercord installed. If unit is to beused on 230 VAC 20 amp in-put power, install new powercord according to Section2-12.

1 Input Power Cord2 115 or 230 VAC Grounded

Receptacle

The Auto-Link circuitry in thisunit automatically links thepower source to the primaryvoltage being applied, either115 or 230 VAC.

An individual branch circuit capableof carrying 30 amperes and pro-tected by fuses or circuit breaker isrequired. Recommended fuse orcircuit breaker size is 35 amperes.Connect input power plug to properreceptacle.

Ref. ST-802 385A

1

2-12. Connecting Input Power

2

1

2-13. Selecting Extension Cord (Use Shortest Cord Possible)

Conductor Size (AWG)*Single Phase AC

Input Voltage4 6 8 10 12 14

Input VoltageMaximum Allowable Cord Length in ft (m)

115 160 (49) 107 (33) 71 (22) 47 (14) 29 (9) 19 (6)230 471 (144) 321 (98) 215 (66) 146 (45) 90 (27) 59 (18)

*Conductor size is based on maximum 3% voltage drop


2-14. Installing 230 Volts Ac Input Power Cord

Disconnect input power plug from re-ceptacle before installing differentinput power cord.

Remove the case by removing the two tophandle screws and sliding case up and off.Disconnect case grounding wire when re-moving case.1 Input Power CordRemove knob from Power Switch (4). Notehow knob goes onto shaft.Remove screws holding Power Switch inplace, and pull switch out toward inside ofunit.

Loosen strain relief clamp, and push severalinches of power cord into unit.Mark location of switch terminals whereblack and white leads are connected, andnote location of ground lead. Disconnectleads from ground terminal and switch.2 Black Switch Lead3 Rear Panel4 Power SwitchPull out power cord from rear of unit.5 Case Grounding Lead6 White Lead

7 Green Ground Lead

Insert new power cord through strain relief,and push an extra inch into unit.

Connect ground lead and black and whiteleads to marked locations. Double-check allconnections.

Reinstall Power Switch onto rear panel. Pullpower cord back through strain relief untilleads are properly dressed in unit. Tightenclamp.

Reinstall case and reconnect case ground-ing lead during assembly.

Ref. ST-802 385

5

4

6

2

1

3 7

Tools Needed:


2-15. Remote Receptacle Information (For Lift-Arc TIG Only)

Remote control device has complete control of amperage at all times whenconnected to the remote receptacle.

NOTE

Socket* Socket Information

1 N/A

2 N/A

3 +10 volts DC

4 0 to +10 volts DC input command signal from remote control.

5 Remote control circuit common.

ST-802 385-A6 Remote enable. Closure to circuit common enables the remote

control and places the machine in Lift-Arc TIG (see Section3-2).

*The remaining sockets are not used.Note: Receptacle is not used to control contactor. Output is always on.Note: Connecting a remote control automatically places the machine in Lift-Arc TIG regardless of front panel setting.


SECTION 3 OPERATION

3-1. Front Panel Controls

192 999-A

2

3

4

5

1

6

1 Ready LightThis light comes On when the PowerSwitch on the rear panel is placed in the ON(I) position. The light indicates that the unitis energized and ready for welding opera-tions. The fan motor is thermostatically

controlled and only runs when coolingis needed.

2 Amperage Adjustment ControlThis control adjusts the desired amperagefor the welding application. Use this controlto set the required value for the specific joband electrode. The dial is calibrated in actu-al amperes according to the input voltageused to power the unit.

The Amperage Adjustment Control is adual reading dial. Be sure to set it ac-cording to the input voltage supplyingpower to the unit.

3 Overtemperature LightThis light comes ON when the unit over-heats. When this happens, the unit shutsdown and the fan motor runs. Once the unithas cooled down, the output will come backON. Reduce the duty cycle or amperagebefore starting to weld again. This lightflashes if the input voltage (primary) is toolow or if there is an input overcurrent fault.4 Positive Weld Output Receptacle

IndicatorFor STICK welding, connect the electrodecable to this receptacle (normally uses re-verse polarity connections, but alwayscheck electrode recommendations.) ForTIG welding, connect work cable to this re-ceptacle (normally uses straight polarity).

5 STICK / TIG Selector SwitchThis switch provides a simple and easyway to select the required welding process.

Place the switch in the desired position tosuit the application. This switch is NOT aPolarity Switch. This switch activates theLift Arc (see Section 3-2) and Dig circuitry.6 Negative Weld Output Receptacle

IndicatorFor STICK welding, connect the work cableto this receptacle (normally uses reversepolarity connections, but always checkelectrode recommendations.) For TIGwelding, connect torch cable to this recep-tacle (normally uses straight polarity).7 Remote Receptacle (For Lift-Arc TIG

Only)Allows amperage to be controlled remotely.Amperage may be adjusted from min tomax of unit output, regardless of wherefront panel amperage control is set.

Connecting a remote control automati-cally places the machine in Lift-Arc TIGregardless of front panel setting.

Weld output receptacles areenergized when PowerSwitch is On and Input sup-ply power is connected andOn.

7


3-2. Lift-Arc TIG ProcedureWith Process Switch in the Lift-ArcTIG position, start an arc as follows:1 TIG Electrode2 WorkpieceTouch tungsten electrode to work-piece at weld start point, holdelectrode to workpiece for 1-2seconds, and slowly lift electrode.An arc will form when electrode islifted.Open-circuit voltage is present be-fore tungsten electrode touchesworkpiece. However, the arc willnot initiate until after the electrode islifted from workpiece. This allowselectrode to touch workpiece with-out overheating, sticking, or gettingcontaminated.

1

1 2SecondsTouch

Do NOT Strike Like A Match!

2

Ref. S-156 279


SECTION 4 HOW AN INVERTER WORKS

This welding power source uses invertertechnology. An inverter is a specific type ofpower converter. Power converters changeelectrical power from one form to another.What is commonly called an inverter-typewelding power source is really three con-verters in one. (See Figure) AC primary in-put power is first converted to DC by the in-put rectifier. The actual inverter section ofthe power source converts DC back to AC.And after the inverter section, the AC is con-verted back to DC welding output power.HOW DO INVERTERS WORK?Instead of operating at common input power

frequency of 50 or 60 hertz (Hz), invertersboost the frequency as much as 1000 timesthat of input frequency. This allows for adrastic reduction in the number of trans-former coil turns, and reduced core area.The inverter creates its own operating fre-quency to drastically reduce the transform-er size and to provide electrical advantagesto enhance weld performance. To do thiswith electrical efficiency, the convertingmust take place to raise the frequency andultimately provide the desired DC arc char-acteristics.

This high operating frequency is the secret.

Because an inverter has the high operatingfrequency, the duration of each cycle ismuch shorter. Therefore, the amount ofpower available in each cycle is drasticallyreduced. With less power in each cycle, theinverters output power can be controlledmuch more precisely and also much quick-er. The increased precision in output controlmeans that the best weld characteristicscan be obtained for various weld processes.The ultra-fast, electrical circuitry responseprovides smooth, clean, blast free arc initi-ations and quick reactions to changes in theweld puddle.

Inv 4/01


SECTION 5 THEORY OF OPERATION

1 Power Switch S1Provides on/off control of weldingpower source.2 Fan Motor FMProvides cooling of internal compo-nents.3 Main Control Board PC1Provides electrical connections forS1, PC1, PC10, PM1, L1 and L2. In-put capacitors, precharge relay andresistor, bleed resistors, various fil-ter and snubber components, inputcurrent transducer, inverter primarycurrent transformer, and switch-mode power supplies for controlpower are mounted on PC2.4 Thermistor RT1Protects output sink from overheat-ing.5 Thermistor RT2Protects main transformer T1 fromoverheating.6 Front Assembly Board PC2Controls output of machine, anddisplays error message.7 Main Transformer T1Driven by MOSFETs in PM1. Sup-plies power to weld output circuit.8 Inductors L1 And L2Filter switching noise from output ofT1.9 Output Rectifier SR2Rectifies main transformer T1 volt-age.10 ShuntMonitors output current for regula-tion.11 Positive And Negative Weld

Output ReceptaclesProvide weld output and allowchanging of output polarity.

PowerSwitch

S1

Line InputPower

1

Main TransformerT1

Shunt

Single-Phase

Main Control Board PC1

9

Output Current Feedback

Output V

oltage Feedback

Fan MotorFM1

Inductor L1

Output Rectifier SR2

NegativeWeld OutputReceptacle

11_

Weld OutputReceptacle

11Positive

+

ThermistorRT1

ThermistorRT2

Output Current Feedback

Inductor L1Filter Signal

Filter Signal

Output V

oltageFeedback

32 4

5

7

8 8

10

Front AssyBoard PC2

6


SECTION 6 PRE-POWER CHECKLIST

6-1. Checking Unit Before Applying Power

See Section 8-2 for test points and values andSection 14 for parts location.

Discharge input capacitors according to Section 9-3 and be sure voltage is near zero before touching any parts. Before troubleshooting or applying power to unit, complete following checks to avoid causing further damage.

6-2. Output Rectifier SR2

Ref. 802 931

Read and follow safetyinformation in Section 6-1before proceeding.

1 Output Rectifier SR2Visually inspect SR2 for discolor-ation or signs of heat damage.Isolate diode module for testing.Check each diode anode to cath-ode (diode test). Replace module ifnecessary.

Forward Bias Testing(Conducting)

= .200 to .900Set meter forDiode testing.

K

A

1


6-3. Varistor Read and follow safety

information in Section 6-1before proceeding.

From component side of circuitboard, visually inspect varistor fordiscoloration or signs of heat dam-age.1 Varistor Test PointsCheck the resistance of varistor atpoints indicated. Polarity is not im-portant. Resistance should mea-sure 650K ohms 10%. If resist-ance is infinite, varistor was dam-aged by an over-voltage condition.

1

Rear Of Unit


6-4. Power Switch S1

Ref 802 931

Read and follow safetyinformation in Section 6-1before proceeding.

1 Checking ResistanceMake sure unit is unplugged andPower switch S1 is in the On posi-tion. First check resistance acrossterminals labeled A. Meter shouldread near 0 ohms. Next, check re-sistance across terminals labeledB. Meter should read near 0 ohms.Turn Power switch Off.2 Checking Input VoltagePlug unit in and turn Power switchto the On position. Measure inputvoltage across terminals labeled C.Meter should read 115 or 230 VACdepending upon input power.

Power Switch S1

A

A

B

B

1 2

C C


SECTION 7 EXPLANATION OF ELECTRICAL PARTSelect_parts 2/02

7-1. Safety Precautions Read Before Using This Guide

WARNING: ELECTRIC SHOCK can kill. Disconnect input power or stop engine before servicing. Do not touch live electrical parts. Do not operate machines with covers removed. Have only qualified persons install, use, or service equipment.

7-2. Explanation Of Electrical PartsPART NAME FUNCTION PICTURE CIRCUIT SYMBOL

CAPACITOR A device that stores electrical energy. Largecapacitors or a bank of capacitors can beused to smooth out the DC welding arc in aMIG welding power source. Smaller diskcapacitors can be used for HF protection.

C1 C1

POLARIZED NON-POL.

CIRCUIT BREAKER A protection device that breaks a circuit whencurrent levels exceed its rating. Unlike a fusethat needs to be replaced when blown, acircuit breaker can be reset.

CB1

DIODE A device that allows current to flow in onedirection only. Most common use is tochange AC to DC.

D1

FUSE A protection device, usually an enclosedpiece of wire that melts and breaks the circuitwhen the current exceeds the fuse rating.

F1

HALL DEVICE Produces a small DC voltage proportional tothe current it is sensing (usually weldingcurrent). This feedback signal can be used toregulate the welding output (line voltagecompensation). It may even be used to drivean ammeter.

HD1

RESISTOR A device which resists the flow of electriccurrent. Uses include limiting the current for amotor brake circuit in a wire feeder and fordischarging a capacitor.

FIXED

FIXED TAPPED

R1

R1

POTENTIOMETERORRHEOSTAT

Both devices have a moveable brush thatmakes contact along a resistor, allowing youto easily change the resistance measured atthe brush (sometimes referred to as a wiper).Their primary purpose is to give the operatora way to adjust welding parameters such aswire speed, preflow time, voltage,inductance, etc.

VARIABLE R1


PART NAME CIRCUIT SYMBOLPICTUREFUNCTION

PILOT LIGHT A light located on the front panel whichindicates if the machine is on or off. PL

1

FAN MOTOR This device provides cooling of the internalparts of a welding power source.

FM

VARISTOR A protection device whose resistance isdependent on the voltage applied to it. Innormal operation it has a high resistance;however, a surge of voltage (voltage spike)will cause its resistance to go way down andabsorb the spike. These devices are mostoften found in rectifying circuits, where theyare used to protect the diodes.

VR1

GAS OR WATERSOLENOID(VALVE)

These are electromechanical devices used tostart or stop the flow of shielding gas orwater. GS1OR

WS1

RELAYCOIL ANDCONTACTS,NORMALLY OPENAND NORMALLYCLOSED

This is an electromechanical device whosecontacts change state (the normally openpoints close and the normally closed pointsopen) when proper voltage is applied to thecoil. These contact points in turn may controla fan motor, gas solenoid, contactor, etc.Circuit diagrams (schematics) always showthe contact points in the power off state.

CR1 CR1

COIL

NRM OPENPOINTS

NRM CLOSEDPOINTS

THERMOSTAT,NORMALLY OPENAND NORMALLYCLOSED

This is a switch that closes its normally opencontacts (or opens its normally closedcontacts) when a preset temperature isreached. When the temperature goes backdown, it will reset itself. Uses of thesedevices include turning on a fan motor whenneeded and shutting off the output of awelding power source if it is overheating.

NRM OPEN NRM CLOSED

TP1TP1

CONTACTOR A heavy duty relay. Usually used to makeand break the welding arc or primary power.

WW

COIL

NRM OPENPOINTS

STABILIZER/REACTOR

When placed in a DC circuit, the inductor orstabilizer as it is usually called, will opposeany change in existing current. It is thereforewidely used to stabilize the welding arc.When the inductor is placed in an AC circuit itis referred to as a reactor where it now actsto restrict the flow of current. A tappedreactor is used to create current ranges forwelding.

Z1

L1



MOTOR A device that is typically used to feed wire ina MIG welding system.

B1

SHUNT A precision low-value resistor typically usedto supply a small voltage to drive anammeter. SHUNT

MOSFET A device that is used as an electronicswitch. When a signal is applied to the gate(G), current is allowed to flow from the source(S) to the drain (D). This device can be usedto control a relay, the speed of a motor, oreven the output of a welding machine.

D

GAS S

IGBT A device that is used as an electronicswitch. When a signal is applied to the gate(G), current is allowed to flow from the emitter(E) to the collector (C). This device is typicallyused in Invertor designed welding machinesto control the welding output.

C1

G1 (B1)

E1

BRUSHES/SLIPRINGS

Components that allow electrical connectionsbetween stationary and rotating contacts. SLIP

RINGS

BRUSHES

TERMINAL STRIP An insulated connection point for wires. Theyare used for the ease of making multipleconnections and can be a convenient pointfor making electrical checks whentroubleshooting. (Notice the jumper linkconnecting terminals A and B together.)

A B C D E1T

42 42 104 105 74

SWITCH A mechanical device that completes orbreaks the path of the current or sends it overa different path.

SPDTSPST

DPDTDPST



SCR A Silicon Controlled Rectifier (SCR) is anelectrical device with three connections,anode, cathode, and gate. It will allow currentto flow in only one direction and will only doso after receiving a signal on the gate lead.SCRs are used to change AC to DC and tocontrol the output to a load such as a weldingarc.

K

A

G

THERMISTOR A thermally sensitive resistor. The resistanceof a thermistor changes with a change intemperature. Primarily used for Fan onDemand and Thermal Shutdown circuits.

RT1

TH1OR

TRANSFORMER A device that changes AC voltage from onemagnitude to another. Typically used toreduce high primary voltages to lowerwelding voltages.

T1

INTEGRATEDBRIDGERECTIFIER

An arrangement of four diodes used tochange AC to DC. AC

AC

+

AC

AC

+

_

SPARK GAP The arrangement of two electrodes betweenwhich a discharge of electricity will occur.Typically used to produce high frequencywhich can be used for arc starting when TIGwelding.

G

CURRENTTRANSFORMER

A transformer that produces an AC voltageused for measuring purposes. The primarywinding is in series with the circuit carryingthe current to be measured. Its main use inengine-driven equipment is to activate theAutomatic Idle circuit by sensing weldingcurrent or auxiliary power current.

CT1

OR

CT1


SECTION 8 TROUBLESHOOTING

8-1. Troubleshooting

Trouble Remedy

No weld output; unit completely inop-erative; Ready light Off.

Place line disconnect switch for circuit powering welder in On position.

Check and replace line fuse(s), if necessary, or reset circuit breaker.Be sure input power cord is plugged in and that receptacle is receiving input power.

Check continuity of Power switch S1 (see Sections 6-4 and , and replace if necessary.

Check resistance of varistor on circuit board PC1. Correct resistance is 650K ohms 10% (see Section6-3).

No weld output; Ready light On; Over-temperature light Off.

Check and secure loose weld cable(s) into receptacle(s) on welding power source.

Check and correct poor connection of work clamp to workpiece.

No weld output; Ready light On; Over-temperature light On.

Unit overheated causing thermal shutdown. Allow unit to cool with fan On (see Section 2-5).

Reduce duty cycle or amperage to prevent further overload conditions.

Check and correct blocked/poor airflow to and around unit or move unit clear of blockages (see Sec-tion 2-7).Check and clean dirty power module (see Section 9-2).Check thermistor RT1, and replace if necessary (see Section 8-2).

Check fan motor FM, and replace if necessary (see Section 8-2).No weld output; Ready light On; Over-temperature light Flashing.

Turn Power Switch Off and back On again. If light continues to flash, this condition may indicate afault in the power section.

Erratic or improper welding arc oroutput.

Use proper size and type of weld cable (see your Distributor).

Clean and tighten all weld connections.

Check and reverse electrode polarity; check and correct poor connections to workpiece.

Fan not operating (unit is equipped withFan-On-Demand, so fan runs onlywhen needed).

Unit is cool and not warmed up enough to require fan cooling.

Check for and remove anything blocking fan movement.

Check fan motor and control circuitry.

Stick welding problems: Hard starts; Use proper type and size of electrode.poor welding characteristics; unusualspattering problems. Use method shown in Section 11 to get better starts.


Make sure a remote control is not connected to the remote receptacle (see Section 2-10).

TIG welding problems: Wandering arc; Use proper type and size of tungsten.hard starts; poor welding characteris-tics; spattering problems. Use properly prepared tungsten.



Trouble Remedy

TIG welding problems: Tungsten elec- Shield weld zone from drafts.trode oxidizing and not remaining brightafter conclusion of weld. Check shielding gas supply, and be sure it is the correct type (argon) and that the cylinder is not empty.after conclusion of weld.

Check and tighten all gas fittings.

Check and change electrode polarity; move Changeover Switch to TIG position.


8-2. Troubleshooting Circuit Diagram

All voltage and resistance measurementshave a 10% tolerance unless specified.

95 VDC Max

10K ohms

+15 VDC

203 617-A

115 o

r 230 VAC


SECTION 9 MAINTENANCE9-1. Routine Maintenance

Disconnect power before maintaining.

Maintain more often during severe conditions.

3 Months

Replaceunreadablelabels.

Clean and tightenweld terminals. Replace Damaged

Gas Hose

3 Months

Repair Or ReplaceCracked Cables

And Cords

6 Months

Blow out inside. Duringheavy service cleanmonthly.

Do not remove case when blowing out inside of unit(see Section 9-2) .

9-2. Blowing Out Inside Of Unit Do not remove case when

blowing out inside of unit.To blow out unit, direct airflowthrough front and back louvers asshown.

Ref. ST-802 385-A


Significant DC voltage canremain on capacitors afterunit is Off. Always check ca-pacitors as shown to be surethey have discharged beforeworking on unit.

Turn Off welding powersource and disconnect inputpower.

Remove case.1 Input Capacitors2 VoltmeterCheck input capacitors as shown.Measure the dc voltage across thepositive (+) and negative ()terminals until voltage drops to near0 (zero) volts.Proceed with job inside unit.Reinstall case when finished.

Tools Needed:

5/16 in

9-3. Measuring Input Capacitor Voltage

1 22


SECTION 10 ELECTRICAL DIAGRAM The circuits in this manual can be used for troubleshooting, but there might be minor circuit differences from your machine. Use circuit

inside machine case or contact distributor for more information.The following is a list of all diagrams for models covered by this manual.

Model Serial Or Style Number Circuit Diagram

Maxstar 140 KK013519 thru LB066290 193 705-C

Maxstar 140 STR LB066291 and following 203 617-A


193 705-C

Figure 10-1. Circuit Diagram For Maxstar 140 Prior To Serial Number LB066291


Figure 10-2. Circuit Diagram For Maxstar 140 STR Effective With Serial Number LB066291

203 617-A


SECTION 11 STICK WELDING (SMAW) GUIDELINES

11-1. Stick Welding Procedure

stick 12/96 ST-151 593

Weld current starts whenelectrode touches work-piece.

Weld current can damageelectronic parts in vehicles.Disconnect both batterycables before welding on avehicle. Place work clamp asclose to the weld as possible.

1 WorkpieceMake sure workpiece is clean be-fore welding.2 Work Clamp3 ElectrodeA small diameter electrode requiresless current than a large one. Fol-low electrode manufacturersinstructions when setting weld am-perage (see Section 11-2).4 Insulated Electrode Holder5 Electrode Holder Position6 Arc LengthArc length is the distance from theelectrode to the workpiece. A shortarc with correct amperage will givea sharp, crackling sound.7 SlagUse a chipping hammer and wirebrush to remove slag. Remove slagand check weld bead before mak-ing another weld pass.

Tools Needed:

1

4

3

5

2

7

6


11-2. Electrode and Amperage Selection Chart

Ref. S-087 985-A

3/321/8

5/323/167/32

1/41/165/643/32

1/85/323/167/32

1/43/32

1/85/323/167/32

1/43/32

1/85/323/167/32

1/43/32

1/85/323/167/32

1/43/32

1/85/323/163/32

1/85/32

6010&

6011

6013

7014

7018

7024

Ni-Cl

308L

50 100

150

200

250

300

350

400

450

ELEC

TRO

DE

DC* AC

POSI

TIO

N

PEN

ETR

ATIO

N

USAG

E

MIN. PREP, ROUGHHIGH SPATTER

GENERALSMOOTH, EASY,

FASTLOW HYDROGEN,

STRONGSMOOTH, EASY,

FASTERCAST IRONSTAINLESS

DEEPDEEPLOW

MED

LOW

LOW

LOWLOW

ALLALLALL

ALL

ALLFLAT

HORIZFILLET

ALLALL

EPEP

EP,EN

EP,EN

EP

EP,EN

EPEP

601060116013

7014

7018

7024

NI-CL308L*EP = ELECTRODE POSITIVE (REVERSE POLARITY) EN = ELECTRODE NEGATIVE (STRAIGHT POLARITY)

ELEC

TRO

DE

AMPE

RAG

ER

ANG

E

DIA

MET

ER

11-3. Striking an Arc Scratch Start Technique

S-0049

1 Electrode2 Workpiece3 ArcDrag electrode across workpiecelike striking a match; lift electrodeslightly after touching work. If arcgoes out electrode was lifted toohigh. If electrode sticks to work-piece, use a quick twist to free it.

1

2

3

11-4. Striking an Arc Tapping Technique

S-0050

1 Electrode2 Workpiece3 ArcBring electrode straight down toworkpiece; then lift slightly to startarc. If arc goes out, electrode waslifted too high. If electrode sticks toworkpiece, use a quick twist to free it.

1

3

2


11-5. Positioning Electrode Holder

S-0060

90 90

10-30

45

45

GROOVE WELDS

FILLET WELDS

End View of Work Angle Side View of Electrode Angle

End View of Work Angle Side View of Electrode Angle

10-30

11-6. Poor Weld Bead Characteristics

S-0053-A

1 Large Spatter Deposits2 Rough, Uneven Bead3 Slight Crater During Welding4 Bad Overlap5 Poor Penetration

5

42 3

1

11-7. Good Weld Bead Characteristics

S-0052-B

1 Fine Spatter2 Uniform Bead3 Moderate Crater During

WeldingWeld a new bead or layer for each1/8 in. (3.2 mm) thickness in metalsbeing welded.4 No Overlap5 Good Penetration into Base

Metal

1

52 3 4


11-8. Conditions That Affect Weld Bead Shape

Weld bead shape is affected by electrode angle, arc length, travel speed, andthickness of base metal.

NOTE

S-0061

ELECTRODE ANGLE

ARC LENGTH

TRAVEL SPEEDSlow Normal Fast

10 - 30

Drag

Too Short Normal Too Long

Spatter

Angle Too Small Angle Too LargeCorrect Angle

11-9. Electrode Movement During Welding

Normally, a single stringer bead is satisfactory for most narrow groove weld joints;however, for wide groove weld joints or bridging across gaps, a weave bead ormultiple stringer beads work better.

NOTE

S-0054-A

1 Stringer Bead SteadyMovement Along Seam

2 Weave Bead Side to SideMovement Along Seam

3 Weave PatternsUse weave patterns to cover a widearea in one pass of the electrode.Do not let weave width exceed2-1/2 times diameter of electrode.

1 2

3


11-10. Butt Joints

S-0662

1 Tack WeldsPrevent edges of joint from drawingtogether ahead of electrode by tackwelding the materials in position be-fore final weld.2 Square Groove WeldGood for materials up to 3/16 in (5mm) thick.3 Single V-Groove WeldGood for materials 3/16 3/8 in (5-9mm) thick. Cut bevel with oxyacety-lene or plasma cutting equipment.Remove scale from material aftercutting. A grinder can also be usedto prepare bevels.Create 30 degree angle of bevel onmaterials in V-groove welding.4 Double V-Groove WeldGood for materials thicker than 3/8in (9 mm).

30

2

1

1/16 in(1.6 mm)

3 4

11-11. Lap Joint

S-0063 / S-0064

1 Electrode2 Single-Layer Fillet WeldMove electrode in circular motion.3 Multi-Layer Fillet WeldWeld a second layer when a heavi-er fillet is needed. Remove slag be-fore making another weld pass.Weld both sides of joint for maxi-mum strength.

30Or Less

Single-Layer Fillet Weld Multi-Layer Fillet Weld

30Or Less

1 1

2 3

11-12. Tee Joint

S-0060 / S-0058-A / S-0061

1 Electrode2 Fillet WeldKeep arc short and move at definiterate of speed. Hold electrode asshown to provide fusion into thecorner. Square edge of the weldsurface.For maximum strength weld bothsides of upright section.3 Multi-Layer DepositsWeld a second layer when a heavi-er fillet is needed. Use any of theweaving patterns shown in Section11-9. Remove slag before makinganother weld pass.

45Or Less

1

2

1

3

2


11-13. Weld Test

S-0057-B

1 Vise2 Weld Joint3 HammerStrike weld joint in direction shown.A good weld bends over but doesnot break.2 To 3 in

1/4 in

3

21

2 To 3 in

3

2

1

(51-76 mm)

(6.4 mm)

(51-76 mm)

11-14. Troubleshooting Porosity

Porosity small cavities or holes resulting from gaspockets in weld metal.

Possible Causes Corrective Actions

Arc length too long. Reduce arc length.

Damp electrode. Use dry electrode.

Workpiece dirty. Remove all grease, oil, moisture, rust, paint, coatings, slag, and dirt from work surface beforewelding.

11-15. Troubleshooting Excessive Spatter

Excessive Spatter scattering of molten metal particlesthat cool to solid form near weld bead.


Amperage too high for electrode. Decrease amperage or select larger electrode.

Arc length too long or voltage too high. Reduce arc length or voltage.


11-16. Troubleshooting Incomplete Fusion

Incomplete Fusion failure of weld metal to fuse completely withbase metal or a preceeding weld bead.


Insufficient heat input. Increase amperage. Select larger electrode and increase amperage.

Improper welding technique. Place stringer bead in proper location(s) at joint during welding.Adjust work angle or widen groove to access bottom during welding.Momentarily hold arc on groove side walls when using weaving technique.

Keep arc on leading edge of weld puddle.

Workpiece dirty. Remove all grease, oil, moisture, rust, paint, coatings, slag, and dirt from work surface beforewelding.

11-17. Troubleshooting Lack Of Penetration

Lack Of Penetration shallow fusion between weld metal andbase metal.

Lack of Penetration Good Penetration


Improper joint preparation. Material too thick. Joint preparation and design must provide access to bottom of groove.Improper weld technique. Keep arc on leading edge of weld puddle.

Insufficient heat input. Increase amperage. Select larger electrode and increase amperage.

Reduce travel speed.

11-18. Troubleshooting Excessive Penetration

Good Penetration

Excessive Penetration weld metal melting through base metal andhanging underneath weld.

Excessive Penetration


Excessive heat input. Select lower amperage. Use smaller electrode.

Increase and/or maintain steady travel speed.


11-19. Troubleshooting Burn-Through

Burn-Through weld metal melting completely through base metal resultingin holes where no metal remains.


Excessive heat input. Select lower amperage. Use smaller electrode.

Increase and/or maintain steady travel speed.

11-20. Troubleshooting Waviness Of Bead

Waviness Of Bead weld metal that is not parallel and does not coverjoint formed by base metal.


Unsteady hand. Use two hands. Practice technique.

11-21. Troubleshooting Distortion

Distortion contraction of weld met-al during welding that forces basemetal to move.

Base metal movesin the direction of

the weld bead.


Excessive heat input. Use restraint (clamp) to hold base metal in position.Make tack welds along joint before starting welding operation.Select lower amperage for electrode.

Increase travel speed.

Weld in small segments and allow cooling between welds.


SECTION 12 SELECTING AND PREPARINGTUNGSTEN ELECTRODE

gtaw 7/97

For additional information, see your distributor for a handbook on the GasTungsten Arc Welding (GTAW) process. Wear clean gloves to preventcontamination of tungsten electrode.

NOTE

12-1. Selecting Tungsten Electrode

Amperage Range - Gas Type - PolarityElectrode Diameter DC Argon Electrode Negative/Straight

PolarityDC Argon Electrode Positive/Reverse

Polarity2% Thorium Alloyed Tungsten (Red

Band).010 Up to 25 *.020 15-40 *

.040 25-85 *

1/16 50-160 10-203/32 135-235 15-301/8 250-400 25-405/32 400-500 40-553/16 500-750 55-801/4 750-1000 80-125

Typical argon shielding gas flow rates are 15 to 35 cfh (cubic feet per hour) 7 to 16.5 lpm (liters per minute).*Not Recommended.The figures listed are intended as a guide and are a composite of recommendations from American Welding Society (AWS) and electrodemanufacturers.

12-2. Safety Information About Tungsten

Ref. S-0161

Grinding the tungsten elec-trode produces dust and fly-ing sparks which can causeinjury and start fires. Use lo-cal exhaust (forced ventila-tion) at the grinder or wear anapproved respirator. ReadMSDS for safety information.Consider using tungstencontaining ceria, lanthana,or yttria instead of thoria.Grinding dust from thoriatedelectrodes contains low-lev-el radioactive material.Properly dispose of grinderdust in an environmentallysafe way. Wear proper face,hand, and body protection.Keep flammables away.

1 Pointed Tungsten Electrode2 Tungsten Electrode With

Balled End

2

1


12-3. Preparing Tungsten For DC Electrode Negative (DCEN) Welding

Ref. S-0161 / Ref. S-0162

1 Tungsten Electrode2 Tapered EndGrind end of tungsten on fine grit,hard abrasive wheel before weld-ing. Do not use wheel for other jobsor tungsten can become contami-nated causing lower weld quality.

3

Ideal Tungsten Preparation Stable Arc

2-1/2 TimesElectrode Diameter

1 2

1 Stable Arc2 FlatDiameter of this flat determinesamperage capacity.3 Grinding Wheel4 Straight Ground3

1

2

1 Arc Wander2 Point3 Grinding Wheel4 Radial Ground

2

1

4

Wrong Tungsten Preparation Wandering Arc

4


SECTION 13 GUIDELINES FOR TIG WELDING (GTAW)13-1. Positioning The Torch

Ref. ST-161 892

Grinding the tungsten elec-trode produces dust and fly-ing sparks which can causeinjury and start fires. Use lo-cal exhaust (forced ventila-tion) at the grinder or wear anapproved respirator. ReadMSDS for safety information.Consider using tungstencontaining ceria, lanthana,or yttria instead of thoria.Grinding dust from thoriatedelectrodes contains low-lev-el radioactive material. Prop-erly dispose of grinder dustin an environmentally safeway. Wear proper face, hand,and body protection. Keepflammables away.

1 WorkpieceMake sure workpiece is cleanbefore welding.2 Work ClampPlace as close to the weld aspossible.3 Torch4 Filler Rod (If Applicable)5 Gas Cup6 Tungsten ElectrodeSelect and prepare tungstenaccording to Sections 12-1, and12-2 or 12-3.Guidelines:The inside diameter of the gas cupshould be at least three times thetungsten diameter to provide ade-quate shielding gas coverage. (Forexample, if tungsten is 1/16 indiameter, gas cup should be aminimum of 3/16 in diameter.Tungsten extension is the distancethe tungsten extends out gas cup oftorch.The tungsten extension should beno greater than the inside diameterof the gas cup.Arc length is the distance from thetungsten to the workpiece.

1

1025

1015

6

2

3

4

90

4

5

3/16 in

1/16 in

65

Bottom View Of Gas Cup


13-2. Torch Movement During Welding

ST-162 002-B

Tungsten Without Filler Rod

Tungsten With Filler Rod

Form pool Tilt torch Move torch to frontof pool. Repeat process.

75

75Welding direction

Form pool Tilt torch Add filler metal

Move torch to frontof pool. Repeat process.

Remove rod

Welding direction 15


13-3. Positioning Torch Tungsten For Various Weld Joints

ST-162 003 / S-0792

70

70

90

20

20

1020

70

40

30

20

70

90

20

Butt Weld And Stringer Bead

T Joint

Lap Joint

Corner Joint


Notes

Visit our website atwww.MillerWelds.com

Processes

Description

TIG (GTAW) Welding

Stick (SMAW) Welding

TM-2224A February 2002Eff. w/Serial Number KK013000

Maxstar 140 STRWith Auto-Link AndRemote Receptacle


SECTION 14 PARTS LIST

Hardware is common andnot available unless listed.

ST-802 386-C

1

23

43

5

6

7

89

10 11

13

1617

24

28

2931

32

1415

23

2526

27

10 o

r 10A

1218

2022

19

33

34

35

21

Figure 14-1. Welding Power Source Components


DescriptionPartNo.

Dia.Mkgs.

ItemNo. Quantity

Figure 14-1. Welding Power Source Components

1 203 990 LABEL, WARNING, general precautionary 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 +194 218 WRAPPER (order by serial number) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 S1 194 227 SWITCH, Input Power 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 +194 216 PANEL, REAR 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 197 443 CABLE, INPUT, 115V, 20A 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 043 962 CABLE, INPUT, 230V, 20A (optional) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 190 028 LABEL, WARNING, electric shock hazard 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 FM1 194 226 FAN MOTOR ASSY 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 194 237 BRACKET, shield 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 194 235 BRACKET, transformer 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10 PC1, PC2 194 225 CIRCUIT CARD ASSY, main (consisting of circuit cards PC1 and. . . . . . . . . . . PC2, and heat sink) (Prior to LB066291) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10 PC1 203 619 CIRCUIT CARD ASSY, main (consisting of circuit cards PC1 and. . . . . . . . . . . . . . . . . heat sink (Eff w/LB066291) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10A PC2 203 621 CIRCUIT CARD ASSY, front (Eff w/LB066291) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 194 236 FAN MOTOR BRACKET 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 197 460 INSULATOR 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 197 463 BUS BAR, transformer, top 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Z1,Z2 194 234 TORROID, output filter 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 197 462 BUS BAR, transformer, bottom 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 T1 194 224 TRANSFORMER, main 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 RT2 197 459 THERMOSTAT 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 SR2 185 940 DIODE FAST RECOVERY KIT 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 197 461 CAP, rectifier 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 RT1 194 219 THERMISTOR, assy 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 C1,C2 194 233 CAPACITORS, output filter 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 194 244 BUS BAR, flexible, positive output 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 194 215 PANEL, FRONT (Prior to LB066291) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 203 618 PANEL, FRONT (Eff w/LB066291) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 RC1,RC2 194 223 WELD OUTPUT RECEPTACLES 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 194 221 AMPERAGE ADJUSTMENT KNOB 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 194 222 COVER, KNOB, BLUE 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 192 999 NAMEPLATE (Prior to LB066291) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 203 620 NAMEPLATE (Eff w/LB066291) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 194 231 BUS BAR, negative output 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 R1 194 228 SHUNT 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 194 217 BASE 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 194 220 SHOULDER STRAP 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 197 457 ELECTRODE HOLDER 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 197 456 WORK CABLE, w/clamp 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

197 458 CONNECTOR, tw lk male (Dinse type) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 203 753 COVER (Eff w/LB066291) 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

200 257 KIT, diode conversion 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +When ordering a component originally displaying a precautionary label, the label should also be ordered.To maintain the factory original performance of your equipment, use only Manufacturers SuggestedReplacement Parts. Model and serial number required when ordering parts from your local distributor.

PRINTED IN USA 2002 Miller Electric Mfg. Co.

Miller Electric Mfg. Co.An Illinois Tool Works Company1635 West Spencer StreetAppleton, WI 54914 USA

International HeadquartersUSAUSA Phone: 920-735-4505 Auto-AttendedUSA & Canada FAX: 920-735-4134International FAX: 920-735-4125

European Headquarters United KingdomPhone: 44 (0) 1204-593493FAX: 44 (0) 1204-598066

TABLE OF CONTENTS1 SAFETY PRECAUTIONS FOR SERVICING2 SPECIFICATIONS AND INSTALLATION3 OPERATION4 HOW AN INVERTER WORKS5 THEORY OF OPERATION6 PRE-POWER CHECKLIST7 EXPLANATION OF ELECTRICAL PARTS8 TROUBLESHOOTING9 MAINTENANCE10 ELECTRICAL DIAGRAM11 STICK WELDING (SMAW) GUIDELINES12 SELECTING AND PREPARING TUNGSTEN ELECTRODE13 GUIDELINES FOR TIG WELDING (GTAW)14 PARTS LIST

MAXSTAR140STR (KK013519)

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