ESAB MIG-28A* Wire Feeder Troubleshooting instruction

Brand: ESAB

Model: MIG-28A* Wire Feeder

Category: Welding System

Type: Troubleshooting instruction

INSTRUCTIONS for

MIG-28A*

WIRE FEEDER

These INSTRUCTIONS are for experienced operators. If you

are not fully familiar with the principles of operation and safe

practices for arc welding equipment we urge you to read our

booklet Precautions and Safe Practices for Arc Welding,

Cutting and Gouging, Form 52-529. Do NOT permit untrained

persons to install, operate or maintain this equipment. Do NOT

attempt to install or operate this equipment until you have read

and fully understand these instructions. If you do not fully

understand these instructions contact your supplier for further

information. Be sure to read the Safety Precautions on page 2

before installing or operating this equipment.

Be sure this information reaches the operator.

You can get extra copies through your supplier.

SPECIFICATIONS

Torch Capacity (100% duty) .................................. 250 amps DC

Torch Weight, approx ..... 3 Ibs. 1.4 kg, (less wire; service lines)

Control Weight, approx ........................................ 16 lbs. (7.2 kg)

Primary Power Required.....................115 volts, 50/60 Hz, 1 ph.

Wire Feed Speed Range .................. 79-709 ipm (33-300 mm/s)

Wires Accommodated ....................... 030- through .045-in. hard

.030- through 1/16-in. soft

Dimensions, in.

Torch Control

Length ........... 15 (381 mm) Length. ..............14.7 (373 mm)

Width ........... 3-1/4 (82 mm) Width .................10.7 (272 mm)

Height ............. .8 (203 mm) Height ................10.2 (260 mm)

Handle Dia ....... .1-3/4 mm)

F-12-728-C

February, 1995

I. INTRODUCTION

The MIG-28A Wire Feeder can be used for either short

arc or spray arc welding with a constant potential (CP) or

a constant current (CC) power supply. A flip of a selector

switch readies the control for use with either type of

welding power. The control operates from a 115 volt AC

50/60 Hz power source.

The MlG-28A consists of two basic units: an SEC-7A

Control and an ST-23 Torch. This instruction booklet

covers the installation and operation of the complete

MIG-28A (torch and control). For installation of torch

accessories and torch maintenance, refer to Form 14-

353, ‘Instructions for ST-23A Mig Welding Torch’.**

A. DESCRIPTION

The SEC-7A Control contains a solid state governor to

maintain wire feed rate for constant potential welding,

and to regulate arc voltage for constant current welding.

Most of the control circuits in the SEC-7A are incorpo-

rated on one printed circuit board which is mounted

inside the control for easy access and removal.

The control circuitry contains a dynamic brake which

quickly stops wire feed, to eliminate freezing of wire in the

weld puddle for the vast majority of conditions. In addi-

tion, an optional Anti-Stick Kit is also available for the

SEC-7A to adjust the amount of wire burnback after wire

feed stops, to further prevent any freezing of welding wire

in the weld puddle.

The ST-23 Torch is an air cooled, spool-on-gun type

manual mig welding torch with a maximum current ca-

pacity of 250 amperes DC continuous duty. The torch

contains a complete gearmotor in the handle which pulls

the welding wire from a 4-in. diameter spool, mounted in

a molded case on the rear of the torch, and delivers it to

the torch nozzle. The case is molded from a rugged,

flame retardant, glass-reinforced polyester compound.

II. SETTING UP THE MIG-28A

A. EQUIPMENT SUPPLIED

The MIG-28A (Series A) is available in a welding outfit

under P/N 19163. Contents of the outfit are listed in Table

F-12-728-C

Table 1 - Contents of MIG-28A Outfit, P/N 19163

Description Qty. Part No.

SEC-7A Control 1 2075159

ST-23A Torch/30-ft. service lines 1 19164

Control Cable, 6-ft., 6-cond., 19 pin 1 36618

Gas Hose, 12-1/2-ft. 1 40V77

Contact Tip (.030" Hard & Soft) 3 996994

Contact Tip (.035" Hard & Soft) 3 996995

Contact Tip (3/64" Soft & .045" Hard) 3 996999

Contact Tip (1/16" Soft) 3 996997

Feed Roll (.030" & .035" Hard & Soft) 1 636343

Torch Liner (.030 & .035 Wire) 1 19166

No. 8 Nozzle Std. Duty 3 999471

No. 10 Nozzle Std. Duty 2 999472

B. REQUIRED COMPANION EQUIPMENT AND

ACCESSORIES

1. R-5007 Argon Regulator-Flowmeter, P/N 998124.

2. 2/0 Welding Cable (customer supplied) in suitable

lengths to connect the power supply to the control and

workpiece. Terminal lug with fiber cover, P/N 81F64,

is available for connecting the cable to the power

supply.

3. Gas Hose Coupling, P/N 11N17 permits you to extend

gas hose by ordering additional hose (40V77).

4. One of the following types of power supplies:

a. A D.C. Rectifier-Type Constant Potential Power

Supply (such as VI-206, VI-300, VI-450, etc.) as

shown in Figure 2.

b. A D.C. Generator or D.C. Rectifier-Type Constant

Current Power Supply which does not have a built-

in contactor. For this type unit, a 300 Amp. Second-

ary Contactor Assembly (P/N 677333) will be re-

quired to interrupt the welding current between the

SEC-7A Control and the power source as shown in

Figure 3. (Refer to Form 12-825 for complete

installation instructions.)

c. A D.C. Rectifier-Type Constant Current Power

Supply that contains a built-in contactor with a

115-volt coil. This type unit can be operated di-

rectly from the SEC-7 control as shown in Figure 4.

d. A Heliarc 306/Heliarc 350 AC/DC Power Supply may

also be used; however, in this case an Adaptor Kit

(P/N 995313) will be required. (Refer to Form 12-

324 for complete installation instructions.)

5. Standard Welders Helmet with proper shade of

glass. A No. 12 glass should be used for currents

of 75 to 200 amperes.

C. OPTIONAL ACCESSORIES

1. Torch Control Cable Extension Assy., (30-ft.) P/N

636968. Used to extend the length of the torch cables

(see Fig. 5)

2. Torch Power and Gas Extension Adaptor, P/N 993457.

This adaptor is used in conjunction with extension

636968 above. Both parts enable you to extend the

torch service lines up to 60-ft. (See Fig. 5.)

3. Control Adaptor Cable (3-ft., 6-cond.) P/N 996736.

Required to connect the control to any power supply

which does not contain a remote contactor recep-

tacle.

4. Control Extension Cable (25-ft.) P/N 996738. Used to

extend the control to power supply cable (see Fig. 2).

Fig. 1 - Interior View of SEC-7A Control

WELD POWER

SELECTOR SWITCH

SWITCH ON P/C BOARD

CONSTANT

POTENTIAL

CONSTANT

CURRENT

PRINTED CIRCUIT BOARD

P.C. Board location of

SLOW INCH DOWN TRIMPOT

(See Section IV-D-2.)

TRANSFORMER

POWER CABLE / GAS CONNECTIONS

WIRE INCH RELAY

TORCH SWITCH RELAY

5. Anti-Stick Kit, P/N 2075076. Kit permits precise ad-

justment of amount of burnback after wire feed stops,

to eliminate freezing of wire in weld puddle. For

installation refer to Section III-B

III. INSTALLATION

A. HOSE AND ELECTRICAL CONNECTIONS

CAUTION: Be sure the Main Line Switch (MLS) on the

control cabinet and the power supply are OFF

before making any connections.

Depending on the type of power supply used, make the

necessary cable and hose connections in accordance

with one of the following interconnection diagrams.

Fig. 2 - Interconnection Diagram for Constant Potential

Welding

Fig. 3 - Interconnection Diagram for Constant Current

Power Supplies without Built-in Contactor.

Fig. 4 - Interconnection Diagram when using a Con-

stant Current Power Supply/Built-in Contactor.

REGULATOR/FLOWMETER

GAS

SEC-7A

FRONT

TORCH POWER

CABLE (30 ft.)

TORCH CONTROL

CABLE (30 ft.)

CONSTANT POTENTIAL

POWER SUPPLY

(Customer Supplied)

GRD.

WORK

2/0 WELDING CABLE

(Customer Supplied)

SEC-7A

BACK

ST-23A TORCH

25 ft. EXTENSIONS

CABLE - 996738

Optional

6 ft. CONTROL CABLE-

996739 (Provided)

Fig. 2 - Interconnection Diagram for Constant Potential Welding

NOTE:

For Internal power cable & gas hose

connections, See Fig. 3

B. ANTI-STICK KIT

All components of the Anti-Stick Kit are mounted on a PC

board connected to the anti-stick potentiometer. To

install the kit simply insert potentiometer through knock-

out on back panel. Then with hardware provided tighten

potentiometer, and install knob. For electrical connec-

tions refer to Figure 10.

IV. ADJUSTMENTS AND OPERATION

A. SHIELDING GAS FLOW

The torch trigger switch controls the flow of shielding gas

set by the flowmeter. To check the flow, first deenergize

the control by placing the Main Line Switch (MLS) in the

OFF position. Then depress the torch switch. After

making the necessary adjustments to the flowmeter,

place the Main Line Switch in the ON position.

B. TORCH CONTROLS

Wire feed power is provided by the permanent-magnet

type DC motor in the ST-23A torch. Wire may be inched

by pressing the button on the bottom of the torch handle

CAUTION: Do not allow metal-to-metal contact between the wire feeder (control) cabinet and a metal surface

connected in any way to a welding ground. Without insulation, a poor work lead connection may create a

difference in potential that sends part of the welding current through the safety ground wiring in the control

cable and wire feeder, resulting in burnout of that wiring and/or damage to wire feeder circuitry. If safety

ground burns out, the operator may be exposed to 115 V. shock hazard.

12-1/2 ft. GAS

HOSE-40V77

2/0 WELDING CABLE

(Customer Supplied)

12-1/2 ft. GAS

HOSE-40V77

SEC-7A

FRONT

TORCH POWER

CABLE (30 ft.)

POWER CABLE

ADAPTOR - 993457

Fig. 5 - Extending Torch Service Lines

Wire feed speed during the welding cycle is controlled by

the potentiometer on the torch.

In constant potential welding, the wire begins to feed

the instant the torch trigger is fully depressed. This is

desirable when welding with CP or CP slope control

power. During CP operation, the potentiometer on the

torch regulate the welding current by means of the wire

feed speed. Turning the potentiometer in a clockwise

direction will increase the welding current (increase wire

feed speed); turning counterclockwise will decrease

welding current (decrease wire feed speed). An initial

setting should be low to reduce the possibility of burning

through the plate.

In constant current welding, full torch switch depres-

sion immediately initiates a slow inch down sequence

until the wire touches the work and stops. After the arc is

established, normal welding speed is regulated from the

torch potentiometer. During constant current welding,

the torch potentiometer controls the arc voltage. Turning

the potentiometer clockwise will decrease the arc volt-

age by increasing the wire feed speed; turning it counter-

clockwise will increase the arc voltage by decreasing the

wire feed speed. Thus, wire feed speed is regulated the

same way in CC as in CP welding. An initial setting

should be high to avoid burnbacks.

C. CONTROL SWITCH SETTINGS (see Figs. 6- 8)

1. Place the Weld Power Selector Switch inside the

control (on the PC board) to the proper position with

respect to the type of power supply being used. Refer

to Figure 8 for correct position of the switch.

2. Place the Main Line Switch in the ON position.

3. If the optional Anti-Stick Kit has been installed, set the

potentiometer to the desired setting depending on the

amount of burnback desired. The higher the setting,

the greater the amount of time that the contactor is

held in to allow the wire to burn back out of the weld

puddle.

IMPORTANT: If the power supply you are using is

equipped for high frequency starting,

make sure that the HF. Control is in the

‘OFF ’position.

D. WELDING OPERATION

With the control Main Line Switch in the ON position and

the torch, shielding gas, and power supply properly

adjusted, welding action will begin as follows:

1. In CP Welding, partial depression of the torch switch

opens the gas flow valve in the torch (for preflow) and

full depression energizes the welding contactor and

initiates wire feed at welding speed to strike an arc.

REGULATOR/FLOWMETER

ST-23A TORCH

30 ft. EXTENSION

CABLE- 636968

TORCH CONTROL

CABLE (30 ft.)

Welding will continue as long as the arc is maintained

and the torch switch is fully depressed.

2. In CC Welding, partial depressing of the torch switch

opens the gas flow valve in the torch to provide

shielding gas preflow. Full torch switch depression

energizes the contactor and initiates an automatic

slow inch down wire sequence. This sequence imme-

diately feeds electrically hot wire at a slow inch speed

and stops when the wire touches the work. After the

arc is established, normal welding speed is regulated

from the torch potentiometer. Welding will continue as

long as the arc is maintained and the torch switch is

fully depressed. The touch starting feature provided

by the “slow-inch” sequence allows the operator to

hold his torch position and eliminates the out-of-

position problems caused by scratch starting with an

extended wire.

NOTE: The slow inch control in CC welding is provided

by an adjustable trimpot that has been added in

the upper right-hand portion of all PC boards

(997245) manufactured after September, 1980.

The wire inch speed can be varied by readjust-

ing the trim pot; however, if you still prefer the

original scratch-starting mode of operation, sim-

ply set the trim pot to its minimum setting.

To stop the welding action in CC or CP welding, slowly

(for postflow) release the trigger switch until the arc is

extinguished. Partially depressing the trigger switch al-

lows shielding gas to continue to flow. Flow will stop when

switch is fully released.

V. OPERATING SEQUENCE

Normal

1. Partially close torch switch

—Gas valve opens (for preflow).

2a. Fully close torch switch (Constant Potential Weld-

ing)

—Gas valve remains open, torch switch relay ener-

gizes, weld contactor closes, wire feed motor runs.

2b Fully close torch switch (constant current weld-

ing)

—Gas valve remains open, torch switch relay ener-

gizes, weld contactor closes, and wire feed motor

runs at slow inch down speed until wire touches

work. After the arc is established, motor runs at

normal welding speed.

3. Partially release torch switch

—Torch switch relay opens, weld contactor opens,

wire feed motor deenergizes, brake circuit activates,

gas valve remains open (for postflow).

4. Fully release torch switch

—Gas valve closes.

With Optional Anti-Stick Kit Installed

Same as normal except when the torch switch is re-

leased the weld contactor is held in for a short period of

time to allow the wire to burnback out of the weld puddle.

The duration of this time is controlled by the anti-stick

potentiometer.

VI. TROUBLESHOOTING

If this equipment does not operate properly, stop

work immediately and investigate the cause of the

malfunction. Maintenance work must be performed

by an experienced person, and electrical work by a

trained electrician. Do not permit untrained persons

to inspect, clean, or repair this equipment. Use only

recommended replacement parts.

Listed below are a number of trouble symptoms, each

followed by the checks or action suggested to determine

the cause. Listing of checks and/or actions is in “most

probable” order, but is not necessarily 100% exhaustive.

Always follow this general rule: Do not replace a printed

circuit (PC) board until you have made all the following

checks. Make sure that the PC board is in good contact

with its receptacle when making the following checks.

Always put the main power switch in “OFF” position

before removing or installing a PC board. Take great care

not to grasp or pull on components when removing a PC

board.

A. SYMPTOM: No arc.

1. Welding cable circuit may be broken.

2. Welding work lead connection may be poor.

3 Contactor does not come in when torch switch is

closed (see B below).

4. Check main power fuses and power supply.

B. SYMPTOM: Contactor does not energize when

torch switch is closed.

1. Control cable may be faulty.

2. Contactor coil may be open.

3. Torch switch relay (TSR) may be bad; replace if

necessary (see C below).

C. SYMPTOM: Torch Switch Relay (TSR) does not

energize when torch switch is closed.

1. Main Line Switch on control in ‘OFF’ position.

2. Fuse F1 in control may be blown.

3. Torch cable or cable connections may be faulty.

4. Torch Switch Relay coil may be open; check

resistance of coil; should be from 250 to 300 ohms.

5. Torch switch may be faulty.

D. SYMPTOM: No wire inch.

1. Main Line Switch on control in ‘OFF’ position.

2. Fuse F1 in control may be blown.

3. Torch cable or cable connections may be faulty.

4. Wire Inch Relay (WIR) coil may be open; check

resistance of coil; should be from 250 to 300 ohms.

E. SYMPTOM: Welding with CP power, wire feed

motor does not run when torch switch closed.

1. Make sure Weld Power Selector Switch (WPSS) is

in "CP" position.

4. Motor armature may be shorted to feed roll. Replace

motor.

5. Replace PC board.

G. SYMPTOM: Wire sticks in puddle.

1. Motor brake defective; check contacts 3 and 7 on

Torch Switch Relay.

2. The Optional Anti-Stick Kit may be necessary.

VII. MAINTENANCE

A. GENERAL MAINTENANCE

Little maintenance is required to keep the wire feeder in

top operating condition. It is important, however, that

moving parts such as feed and pressure rolls, wire feed

motor, etc., be kept clean and free of dust or dirt.

Cleaning is best accomplished by regularly blowing off

these parts with dry compressed air. This should be

done once for every eight hours of operating time, more

often if necessary. Refer to the torch instructions booklet

F-14-353 for general torch maintenance.

Fig. 6 - SEC-7A Control, P/N 2975159 (Front View)

2. Check both TSR and WIR as described in C and D.

3. If TSR and WIR check out OK; check motor brushes.

Refer to torch instructions booklet F-14-353.

4. Transistors Q4 and Q5 may be defective replace if

necessary.

5. Resistors R17 and R18 may be burnt; replace if

necessary.

6. Replace PC board.

F. SYMPTOM: Welding with CC power, wire feed

motor does not run when torch switch closed.

1. Wire should immediately begin a slow inch down

sequence. If it does not, the trimpot is either in mini-

mum setting or is defective — check setting or replace

PC board.

2. If motor still does not run after an arc is established,

refer back to the proper interconnection diagram for

correct cable connections.

3. Check (with ohmmeter, PC board removed) for pos-

sible ground in torch switch, inch switch or motor lead

connections.

VIII. REPLACEMENT PARTS

1. Replacement parts are keyed on the illustrations which follow. Order replacement parts by part number and

part name as shown on the illustrations. DO NOT ORDER BY PART NUMBER ALONE.

2. When ordering, be sure to state quantity of each part needed.

3. Always state the series or serial number of the machine on which the parts are to be used. The serial number

is stamped on the unit's nameplate.

4. Indicate any special shipping instructions.

5. Order replacement parts from your ESAB distributor or from ESAB Welding & Cutting Products, Customer

Service Department, Florence, SC.

COVER - 2075163

* Replace Decal if it Becomes

Excessively Worn or Lost.

HANDLE - 48N65

(4) FOOT - 99W32

F1, FUSE - 82W43

FUSEHOLDER - 182W15

MLS, MAIN LINE

SWITCH - 97W64

P2, TORCH RECEPTACLE-

647233

(Ref.) Opening for Torch

Power/Gas Cable. Includes:

SNAP BUSHING - 647345

SILKSCREEN CABINET -

679593

WARNING DECAL*

2091514

(Ref.) Knockout Plug for

Optional Anti-Stick Kit -

2075076

P1, POWER SUPPLY

RECEPTACLE - 634772

(Ref.) Opening for Gas

Line Connection. Includes:

SNAP BUSHING -

639533

(Ref.) Opening for Power

Supply Pos (+) Output

Cable. Includes:

SNAP BUSHING -

647345

Fig. 7 - SEC-7A Control (Rear View)

VIEW “A”

SWITCH ON

P/C BOARD

Fig. 8 - SEC-7A Control (Inside View)

ANTI STICK

CONSTANT

CURRENT

CONSTANT

POTENTIAL

PC BOARD ASSY. - 997245

(Ref.) WELD POWER SELECTOR

SWITCH (See View “A”)

TPI, TIE POINT - 94W84

(Ref.) SLOW INCH TRIMPOT.

P3, PC BOARD RECEPTACLE

636608

Q4, TRANSISTOR - 2062221

(Under Heatsink)

MOUNTING BRACKET - 995297

TP2, TIE POINT - 94W84

R17, RESISTOR - 17120001

C1, CAPACITOR - 993539

HEATSINK - 2075164

MOUNTING CLAMP - 993540

POWER CABLE ADAPTOR BLOCK - 674156

(Ref.) 7/8 - 14NF - 2B - LH THREADS

(+), POWER/GAS CONNECTION ADAPTOR - 2075165

(Ref.) 5/8-18NF - 2B

THREADS

TB1, TERMINAL BLOCK - 91W66

TR1, TRANSFORMER - 2062227

TSR, TORCH SWITCH

RELAY - 97W55

R18, RESISTOR -

17120001

TP3, TIE POINT -

94W84

Q5, TRANSISTOR

2062221

(Under Heatsink)

WIR, WIRE INCH

RELAY - 97W55

TP4, TIE POINT -

94W84

HEATSINK - 2075164

POWER SUPPLY

CABLE

GAS

“+”

WELDING CABLE

ELECTRICAL PARTS LIST

Symbol Part No. Description

C1 993539 Capacitor, 1,500 uf, 50 WVDC

F1 82W43 Fuse, 1 Amp Standard

MLS 97W64 Switch, DPST, 15A/125V, Cutler Hammer No.

7560K5

P1 634772 Receptacle, Amphenol No. MS-3102A-18-12P

P2 647233 Receptacle, Amphenol No. MS-3102A-18-8S

P3 636608 Receptacle, PC Board

Q4, 5 2062221 Transistor, International Rectifier No. 1R3772

R-17, 18 17120001 Resistor, 1/2 Watt, 1 Ohm

TB1 91W66 Terminal Block

TP1-4 94W84 Tie Point

TR1 2062227 Transformer, 115V/25V, JWL Asso. P/N 1000-25-

TSR, WIR 97W55 Relay, Potter & Brumfield No. PRD11DY0

LOCATED ON ST-23

TORCH

LOCATED ON ST-23

TORCH

MOTOR

NOTE:

1. CONNECTION FOR P/C BOARD

ANTI-STICK OPTION

PI-F

" - "

WORK

" + "

ARC

VIO

P2-G

P2-F

YEL

RED

BLK

MLS

(1)

(2)

1 AMP

TB1-5

BLK

120 VAC

SEE NOTE 1

RED

TSR

BLU

PI-C

PI-D

PI-A

GRN

PI-E

ORN

(1)

(2)

(3)

(4)

25.2 VAC

RED

GND STUD

PI-B

WHT

MLS

(3)

(4)

RED

YEL

BRN

TB1-1

GRN

WIR

TSR

- +

1500 uF

50 VDC

GRY

TBI-8

TBI-7

BLU

BRN

BLU

GRY

TSR

P2-D

P2-E

TSR

GRY

RIB

1/2 W

GRY

1/2 W

TB1-2

R17

TB1-6

TB1-3

VIO

GRY

WIS

P2-B

SEE NOTE 1

RED

P2-A

VIO

WIR

ORN

BLK

TB1-4

BLK

P2-H

Fig. 9 - Schematic Diagram, SEC-7A Control

POWER SUPPLY WITH

Fig. 10 - Wiring Diagram, SEC-7A Control

F-12-728-C 2/95 Printed in U.S.A.

ESAB MIG-28A* Wire Feeder Troubleshooting instruction

Brand: ESAB

Model: MIG-28A* Wire Feeder

Category: Welding System

Type: Troubleshooting instruction

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ESAB MIG-28A* Wire Feeder Troubleshooting instruction

ESAB MIG-28A* Wire Feeder Troubleshooting instruction

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