Lincoln Electric SVM144-B User Manual

POWER MIG 255

SVM144-B

July, 2006

Safety Depends on You

Lincoln arc welding and cutting
equipment is designed and built
with safety in mind. However,
your overall safety can be
increased by proper installation
. . . and thoughtful operation on
your part. DO NOT INSTALL,

OPERATE OR REPAIR THIS
EQUIPMENT WITHOUT READ­ING THIS MANUAL AND THE
SAFETY PRECAUTIONS CON­TAINED THROUGHOUT. And,

most importantly, think before
you act and be careful.

SERVICE MANUAL

For use with machines having Code Number : 10563, 10583,10986, 10990

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• Sales and Service through Subsidiaries and Distributors Worldwide •

Cleveland, Ohio 44117-1199 U.S.A. TEL: [phone] FAX: [phone] WEB SITE: www.lincolnelectric.com

• World's Leader in Welding and Cutting Products •

Copyright © 2006 Lincoln Global Inc.

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i

SAFETY

i

LN-15

FOR ENGINE
powered equipment.

1.a. Turn the engine off before troubleshooting and maintenance
work unless the maintenance work requires it to be running.

____________________________________________________

1.b.Operate engines in open, well-ventilated
areas or vent the engine exhaust fumes
outdoors.

____________________________________________________

1.c. Do not add the fuel near an open flame weld­ing arc or when the engine is running. Stop
the engine and allow it to cool before refuel­ing to prevent spilled fuel from vaporizing on
contact with hot engine parts and igniting. Do
not spill fuel when filling tank. If fuel is spilled,
wipe it up and do not start engine until fumes
have been eliminated.

____________________________________________________

1.d. Keep all equipment safety guards, covers and devices in posi­tion and in good repair.Keep hands, hair, clothing and tools
away from V-belts, gears, fans and all other moving parts
when starting, operating or repairing equipment.

____________________________________________________

1.e. In some cases it may be necessary to remove safety

guards to perform required maintenance. Remove
guards only when necessary and replace them when the
maintenance requiring their removal is complete.
Always use the greatest care when working near moving
parts.

___________________________________________________

1.f. Do not put your hands near the engine fan.
Do not attempt to override the governor or
idler by pushing on the throttle control rods
while the engine is running.

___________________________________________________

1.g. To prevent accidentally starting gasoline engines while
turning the engine or welding generator during maintenance
work, disconnect the spark plug wires, distributor cap or
magneto wire as appropriate.

ARC WELDING CAN BE HAZARDOUS. PROTECT YOURSELF AND OTHERS FROM POSSIBLE SERIOUS INJURY OR DEATH.
KEEP CHILDREN AWAY. PACEMAKER WEARERS SHOULD CONSULT WITH THEIR DOCTOR BEFORE OPERATING.

Read and understand the following safety highlights. For additional safety information, it is strongly recommended that you
purchase a copy of “Safety in Welding & Cutting - ANSI Standard Z49.1” from the American Welding Society, P.O. Box 351040,
Miami, Florida 33135 or CSA Standard W117.2-1974. AFree copy of “Arc Welding Safety” booklet E205 is available from the
Lincoln Electric Company, 22801 St. Clair Avenue, Cleveland, Ohio 44117-1199.

BE SURE THAT ALL INSTALLATION, OPERATION, MAINTENANCE AND REPAIR PROCEDURES ARE
PERFORMED ONLY BY QUALIFIED INDIVIDUALS.

WARNING

Mar ‘95

ELECTRIC AND
MAGNETIC FIELDS
may be dangerous

2.a. Electric current flowing through any conductor causes
localized Electric and Magnetic Fields (EMF). Welding
current creates EMF fields around welding cables and
welding machines

2.b. EMF fields may interfere with some pacemakers, and
welders having a pacemaker should consult their physician
before welding.

2.c. Exposure to EMF fields in welding may have other health
effects which are now not known.

2.d. All welders should use the following procedures in order to
minimize exposure to EMF fields from the welding circuit:

2.d.1.

Route the electrode and work cables together - Secure
them with tape when possible.

2.d.2. Never coil the electrode lead around your body.

2.d.3. Do not place your body between the electrode and

work cables. If the electrode cable is on your right
side, the work cable should also be on your right side.

2.d.4. Connect the work cable to the workpiece as close as

possible to the area being welded.

2.d.5. Do not work next to welding power source.

1.h. To avoid scalding, do not remove the
radiator pressure cap when the engine is
hot.

CALIFORNIA PROPOSITION 65 WARNINGS

Diesel engine exhaust and some of its constituents
are known to the State of California to cause can­cer, birth defects, and other reproductive harm.

The engine exhaust from this product contains
chemicals known to the State of California to cause
cancer, birth defects, or other reproductive harm.

The Above For Diesel Engines

The Above For Gasoline Engines

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ii

SAFETY

ii

LN-15

ARC RAYS can burn.

4.a. Use a shield with the proper filter and cover
plates to protect your eyes from sparks and
the rays of the arc when welding or observing
open arc welding. Headshield and filter lens
should conform to ANSI Z87. I standards.

4.b. Use suitable clothing made from durable flame-resistant
material to protect your skin and that of your helpers from
the arc rays.

4.c. Protect other nearby personnel with suitable, non-flammable
screening and/or warn them not to watch the arc nor expose
themselves to the arc rays or to hot spatter or metal.

ELECTRIC SHOCK can kill.

3.a. The electrode and work (or ground) circuits
are electrically “hot” when the welder is on.
Do not touch these “hot” parts with your bare
skin or wet clothing. Wear dry, hole-free
gloves to insulate hands.

3.b. Insulate yourself from work and ground using dry insulation.
Make certain the insulation is large enough to cover your full
area of physical contact with work and ground.

In addition to the normal safety precautions, if welding
must be performed under electrically hazardous
conditions (in damp locations or while wearing wet
clothing; on metal structures such as floors, gratings or
scaffolds; when in cramped positions such as sitting,
kneeling or lying, if there is a high risk of unavoidable or
accidental contact with the workpiece or ground) use
the following equipment:

• Semiautomatic DC Constant Voltage (Wire) Welder.

• DC Manual (Stick) Welder.

• AC Welder with Reduced Voltage Control.

3.c. In semiautomatic or automatic wire welding, the electrode,
electrode reel, welding head, nozzle or semiautomatic
welding gun are also electrically “hot”.

3.d. Always be sure the work cable makes a good electrical
connection with the metal being welded. The connection
should be as close as possible to the area being welded.

3.e. Ground the work or metal to be welded to a good electrical
(earth) ground.

3.f.

Maintain the electrode holder, work clamp, welding cable and
welding machine in good, safe operating condition. Replace
damaged insulation.

3.g. Never dip the electrode in water for cooling.

3.h. Never simultaneously touch electrically “hot” parts of
electrode holders connected to two welders because voltage
between the two can be the total of the open circuit voltage
of both welders.

3.i. When working above floor level, use a safety belt to protect
yourself from a fall should you get a shock.

3.j. Also see Items 6.c. and 8.

FUMES AND GASES
can be dangerous.

5.a.Welding may produce fumes and gases
hazardous to health. Avoid breathing these
fumes and gases.When welding, keep
your head out of the fume. Use enough
ventilation and/or exhaust at the arc to keep

fumes and gases away from the breathing zone. When

welding with electrodes which require special
ventilation such as stainless or hard facing (see
instructions on container or MSDS) or on lead or
cadmium plated steel and other metals or coatings
which produce highly toxic fumes, keep exposure as
low as possible and below Threshold Limit Values (TLV)
using local exhaust or mechanical ventilation. In
confined spaces or in some circumstances, outdoors, a
respirator may be required. Additional precautions are
also required when welding on galvanized steel.

5.b.

Do not weld in locations near chlorinated hydrocarbon

vapors
coming from degreasing, cleaning or spraying operations.
The heat and rays of the arc can react with solvent vapors

to
form phosgene, a highly toxic gas, and other irritating prod­ucts.

5.c. Shielding gases used for arc welding can displace air and
cause injury or death. Always use enough ventilation,
especially in confined areas, to insure breathing air is safe.

5.d. Read and understand the manufacturer’s instructions for this

equipment and the consumables to be used, including the
material safety data sheet (MSDS) and follow your
employer’s safety practices. MSDS forms are available from
your welding distributor or from the manufacturer.

5.e. Also see item 1.b.

Mar ‘95

POWER MIG 255

SAFETY

iii iii

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FOR ELECTRICALLY
powered equipment.

8.a. Turn off input power using the disconnect
switch at the fuse box before working on
the equipment.

8.b. Install equipment in accordance with the U.S. National
Electrical Code, all local codes and the manufacturer’s
recommendations.

8.c. Ground the equipment in accordance with the U.S. National
Electrical Code and the manufacturer’s recommendations.

CYLINDER may explode
if damaged.

7.a. Use only compressed gas cylinders
containing the correct shielding gas for the
process used and properly operating
regulators designed for the gas and

pressure used. All hoses, fittings, etc. should be suitable for
the application and maintained in good condition.

7.b. Always keep cylinders in an upright position securely
chained to an undercarriage or fixed support.

7.c. Cylinders should be located:

•Away from areas where they may be struck or subjected to

physical damage.

•A safe distance from arc welding or cutting operations and

any other source of heat, sparks, or flame.

7.d. Never allow the electrode, electrode holder or any other
electrically “hot” parts to touch a cylinder.

7.e. Keep your head and face away from the cylinder valve outlet
when opening the cylinder valve.

7.f. Valve protection caps should always be in place and hand
tight except when the cylinder is in use or connected for
use.

7.g. Read and follow the instructions on compressed gas
cylinders, associated equipment, and CGA publication P-l,
“Precautions for Safe Handling of Compressed Gases in
Cylinders,” available from the Compressed Gas Association
1235 Jefferson Davis Highway, Arlington, VA 22202.

Mar ‘95

WELDING SPARKS can
cause fire or explosion.

6.a.

Remove fire hazards from the welding area.

If this is not possible, cover them to prevent

the welding sparks from starting a fire.

Remember that welding sparks and hot
materials from welding can easily go through small cracks
and openings to adjacent areas. Avoid welding near
hydraulic lines. Have a fire extinguisher readily available.

6.b. Where compressed gases are to be used at the job site,
special precautions should be used to prevent hazardous
situations. Refer to “Safety in Welding and Cutting” (ANSI
Standard Z49.1) and the operating information for the
equipment being used.

6.c. When not welding, make certain no part of the electrode
circuit is touching the work or ground. Accidental contact can
cause overheating and create a fire hazard.

6.d. Do not heat, cut or weld tanks, drums or containers until the
proper steps have been taken to insure that such procedures
will not cause flammable or toxic vapors from substances
inside. They can cause an explosion even

though

they have
been “cleaned”. For information, purchase “Recommended
Safe Practices for the

Preparation

for Welding and Cutting of
Containers and Piping That Have Held Hazardous
Substances”, AWS F4.1 from the American Welding Society

(see address above).

6.e. Vent hollow castings or containers before heating, cutting or
welding. They may explode.

6.f.

Sparks and spatter are thrown from the welding arc. Wear oil
free protective garments such as leather gloves, heavy shirt,
cuffless trousers, high shoes and a cap over your hair. Wear
ear plugs when welding out of position or in confined places.
Always wear safety glasses with side shields when in a
welding area.

6.g. Connect the work cable to the work as close to the welding
area as practical. Work cables connected to the building
framework or other locations away from the welding area
increase the possibility of the welding current passing
through lifting chains, crane cables or other alternate circuits.
This can create fire hazards or overheat lifting chains or
cables until they fail.

6.h. Also see item 1.c.

POWER MIG 255

SAFETY

iv iv

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PRÉCAUTIONS DE SÛRETÉ

Pour votre propre protection lire et observer toutes les instructions
et les précautions de sûreté specifiques qui parraissent dans ce
manuel aussi bien que les précautions de sûreté générales suiv­antes:

Sûreté Pour Soudage A L’Arc

1. Protegez-vous contre la secousse électrique:

a. Les circuits à l’électrode et à la piéce sont sous tension

quand la machine à souder est en marche. Eviter toujours
tout contact entre les parties sous tension et la peau nue
ou les vétements mouillés. Porter des gants secs et sans
trous pour isoler les mains.

b. Faire trés attention de bien s’isoler de la masse quand on

soude dans des endroits humides, ou sur un plancher met­allique ou des grilles metalliques, principalement dans
les positions assis ou couché pour lesquelles une grande
partie du corps peut être en contact avec la masse.

c. Maintenir le porte-électrode, la pince de masse, le câble de

soudage et la machine à souder en bon et sûr état defonc­tionnement.

d.Ne jamais plonger le porte-électrode dans l’eau pour le

refroidir.

e. Ne jamais toucher simultanément les parties sous tension

des porte-électrodes connectés à deux machines à souder
parce que la tension entre les deux pinces peut être le total
de la tension à vide des deux machines.

f. Si on utilise la machine à souder comme une source de

courant pour soudage semi-automatique, ces precautions
pour le porte-électrode s’applicuent aussi au pistolet de
soudage.

2. Dans le cas de travail au dessus du niveau du sol, se protéger
contre les chutes dans le cas ou on recoit un choc. Ne jamais
enrouler le câble-électrode autour de n’importe quelle partie du
corps.

3. Un coup d’arc peut être plus sévère qu’un coup de soliel, donc:

a. Utiliser un bon masque avec un verre filtrant approprié ainsi

qu’un verre blanc afin de se protéger les yeux du rayon­nement de l’arc et des projections quand on soude ou
quand on regarde l’arc.

b. Porter des vêtements convenables afin de protéger la peau

de soudeur et des aides contre le rayonnement de l‘arc.

c. Protéger l’autre personnel travaillant à proximité au

soudage à l’aide d’écrans appropriés et non-inflammables.

4. Des gouttes de laitier en fusion sont émises de l’arc de
soudage. Se protéger avec des vêtements de protection libres
de l’huile, tels que les gants en cuir, chemise épaisse, pan­talons sans revers, et chaussures montantes.

5. Toujours porter des lunettes de sécurité dans la zone de
soudage. Utiliser des lunettes avec écrans lateraux dans les

zones où l’on pique le laitier.

6. Eloigner les matériaux inflammables ou les recouvrir afin de
prévenir tout risque d’incendie dû aux étincelles.

7. Quand on ne soude pas, poser la pince à une endroit isolé de
la masse. Un court-circuit accidental peut provoquer un
échauffement et un risque d’incendie.

8. S’assurer que la masse est connectée le plus prés possible de
la zone de travail qu’il est pratique de le faire. Si on place la
masse sur la charpente de la construction ou d’autres endroits
éloignés de la zone de travail, on augmente le risque de voir
passer le courant de soudage par les chaines de levage,
câbles de grue, ou autres circuits. Cela peut provoquer des
risques d’incendie ou d’echauffement des chaines et des
câbles jusqu’à ce qu’ils se rompent.

9. Assurer une ventilation suffisante dans la zone de soudage.
Ceci est particuliérement important pour le soudage de tôles
galvanisées plombées, ou cadmiées ou tout autre métal qui
produit des fumeés toxiques.

10. Ne pas souder en présence de vapeurs de chlore provenant
d’opérations de dégraissage, nettoyage ou pistolage. La
chaleur ou les rayons de l’arc peuvent réagir avec les vapeurs
du solvant pour produire du phosgéne (gas fortement toxique)
ou autres produits irritants.

11. Pour obtenir de plus amples renseignements sur la sûreté, voir
le code “Code for safety in welding and cutting” CSA Standard
W 117.2-1974.

PRÉCAUTIONS DE SÛRETÉ POUR
LES MACHINES À SOUDER À
TRANSFORMATEUR ET À
REDRESSEUR

1. Relier à la terre le chassis du poste conformement au code de
l’électricité et aux recommendations du fabricant. Le dispositif
de montage ou la piece à souder doit être branché à une
bonne mise à la terre.

2. Autant que possible, I’installation et l’entretien du poste seront
effectués par un électricien qualifié.

3. Avant de faires des travaux à l’interieur de poste, la debranch­er à l’interrupteur à la boite de fusibles.

4. Garder tous les couvercles et dispositifs de sûreté à leur place.

POWER MIG 255

vv

MASTER TABLE OF CONTENTS FOR ALL

SECTIONS

Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i-iv

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section A

Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section B

Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section C

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section D

Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section E

Troubleshooting and Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section F

Electrical Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section G

Parts Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .P344 Series

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X

Section A-1 Section A-1

TABLE OF CONTENTS

- INSTALLATION SECTION -

Installation ..............................................................................................................Section A

Technical Specifications...............................................................................................A-2

Safety Precautions .......................................................................................................A-3

Uncrating the POWER MIG 255 ...................................................................................A-3

Location........................................................................................................................A-3

Input Power, Grounding and Connection Diagrams ....................................................A-3

Output Polarity Connections........................................................................................A-5

Gun and Cable Installation...........................................................................................A-6

Shielding Gas ...............................................................................................................A-6

POWER MIG 255

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A-2

INSTALLATION

A-2

75°C Copper Wire 75°C Copper Wire

in Conduit in Conduit

Input Ampere AWG (IEC) Sizes AWG (IEC) Sizes

Input Voltage/ Fuse or Breaker Rating On (For lengths (For lengths

Frequency (Hz) Size (Super Lag) Nameplate up to 100 ft) exceeding 100 ft)

208/60 60 50 8 (10 mm2)6 (16 mm2)
230/60 60 46 10 (6 mm2)8 (10 mm2)
460/60 30 24 14 (2.5 mm2) 12 (4 mm2)
575/60 25 19 14 (2.5 mm2) 12 (4 mm2)

NOTE: Use #10 AWG Grounding Wire

TECHNICAL SPECIFICATIONS – POWER MIG 255

INPUT – SINGLE PHASE ONLY

RATED OUTPUT

OUTPUT

RECOMMENDED INPUT WIRE AND FUSE SIZES

Height Width Depth Weight

31.79 in. 18.88 in. 38.78 in. 220 Ibs
808 mm 480 mm 985 mm 100 kg

PHYSICAL DIMENSIONS

Wire Speed 50 – 700 IPM (1.27 – 17.8 m/minute)

WIRE SPEED RANGE

Standard Voltage/Frequency

Input Current @ 200 Amp Rated Output Input Current @ 250 Amp Rated Output

208/230/60 Hz 41/37 Amps 50/46

230/460/575/60 Hz 41/20/16 Amps 50/24/19

Duty Cycle

Amps V

olts at Rated Amperes

40% 250 Amps 26 Volts
60% 200 Amps 28 Volts

100% 145 Amps 26 Volts

Welding Current Range Maximum Open Circuit V

oltage Welding Voltage Range

(Continuous)

30 – 300 Amps 40 Volts 10-28 Volts

POWER MIG 255

INSTALLATION

A-3 A-3

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INPUT POWER, GROUNDING AND
CONNECTION DIAGRAMS

------------------------------------------------------------------------

1. Before starting the installation, check with the
local power company if there is any question
about whether your power supply is adequate for
the voltage, amperes, phase, and frequency spec­ified on the welder nameplate. Also be sure the
planned installation will meet the U.S. National
Electrical Code and local code requirements. This
welder may be operated from a single phase line
or from one phase of a two or three phase line.

2. Models that have multiple input voltages specified
on the nameplate (e.g. 208/230) are shipped con­nected for the highest voltage. If the welder is to
be operated on lower voltage, it must be recon­nected according to the instructions in Figure A.1
for dual voltage machines and Figure A.2 for
triple voltage machines.

Make certain that the input power is electrically
disconnected before removing the screw on the
reconnect panel access cover.

------------------------------------------------------------------------

Read entire installation section before starting
installation.

SAFETY PRECAUTIONS

ELECTRIC SHOCK can kill.

• Only qualified personnel should perform this
installation.

• Only personnel that have read and under­stood the POWER MIG 255 Operating
Manual should install and operate this equip­ment.

• Machine must be grounded per any national,
local or other applicable electrical codes.

• The POWER MIG power switch is to be in the
OFF position when installing work cable and
gun and when connecting other equipment.

WARNING

------------------------------------------------------------------------

UNCRATING THE POWER MIG 255

Cut banding and lift off cardboard carton. Cut banding
holding the machine to the skid. Remove foam and cor­rugated packing material. Untape accessories from
Gas Bottle Platform. Unscrew the two wood screws (at
the Gas Bottle Platform) holding the machine to the
skid. Roll the machine off the skid assembly.

LOCATION

Locate the welder in a dry location where there is free
circulation of clean air into the louvers in the back and
out the front. A location that minimizes the amount of
smoke and dirt drawn into the rear louvers reduces the
chance of dirt accumulation that can block air pas­sages and cause overheating.

ELECTRIC SHOCK can kill.

• Do not touch electrically live parts such as
output terminals or internal wiring.

• All input power must be electrically discon­nected before proceeding.

WARNING

WARNING

POWER MIG 255

INSTALLATION

A-4 A-4

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4. Using the instructions in Figure A.3, have a qual­ified electrician connect the receptacle or cable to
the input power lines and the system ground per
the U.S. National Electrical Code and any applic­able local codes. See Technical Specifications
at the beginning of this chapter for proper wire
sizes. For long runs over 100 feet, larger copper
wires should be used. Fuse the two hot lines with
super lag type fuses as shown in the following dia­gram. The center contact in the receptacle is for
the grounding connection. A green wire in the
input cable connects this contact to the frame of
the welder. This ensures proper grounding of the
welder frame when the welder plug is inserted into
the receptacle.

3. The 208/230 volt 60 Hz model POWER MIG is
shipped with a 10 ft. input cable and plug con­nected to the welder. A matching receptacle is
supplied with the machine. Mount the receptacle
in a suitable location using the screws provided.
Be sure it can be reached by the plug on the input
cable attached to the welder. Mount with the
grounding terminal at the top to allow the power
cable to hang down without bending.

The 230/460/575 volt 60 Hz model is not
equipped with a plug, an input cable, or a
receptacle.

FIGURE A.1 — DUAL VOLTAGE MACHINE INPUT CONNECTIONS.

POWER MIG 255

INSTALLATION

A-5 A-5

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FIGURE A.3 — RECEPTACLE DIAGRAM.

CONNECT TO ASYSTEM
GROUNDING WIRE. SEE
THE UNITED STATES
NATIONALELECTRICAL
CODE AND/OR LOCAL
CODES FOR OTHER
DETAILS AND MEANS FOR
PROPER GROUNDING.

CONNECT TO HOT WIRES
OF A THREE-WIRE, SINGLE
PHASE SYSTEM OR TO ONE
PHASE OF ATWO OR
THREE PHASE SYSTEM.

OUTPUT POLARITY CONNECTIONS

The welder, as shipped from the factory, is connected
for electrode positive (+) polarity. This is the normal
polarity for GMA welding.

If negative (–) polarity is required, interchange the con­nection of the two cables located in the wire drive com­partment near the front panel. The electrode cable,
which is attached to the wire drive, is to be connected
to the negative (–) labeled terminal. The work lead,
which is attached to the work clamp, is to be connect­ed to the positive (+) labeled terminal.

FIGURE A.2 — TRIPLE VOLTAGE MACHINE INPUT CONNECTIONS.

POWER MIG 255

INSTALLATION

A-6 A-6

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GUN AND CABLE INSTALLATION

The Magnum 250L gun and cable provided with the
POWER MIG 255 is factory installed with a liner for

0.035-0.045 in. (0.9-1.2 mm) electrode and an 0.035
in. (0.9 mm) contact tip. Install the 0.045 tip (also pro­vided) if this wire size is being used.

Turn the welder power switch off before installing
gun and cable.

------------------------------------------------------------------------

1. Lay the cable out straight.

2. Unscrew knurled screw on the drive unit front end
(inside wire feed compartment) until tip of screw
no longer protrudes into gun opening as seen
from front of machine.

3. Insert the male end of gun cable into the female
casting through opening in front panel. Make sure
connector is fully inserted and tighten knurled
screw.

4. Connect the gun trigger connector from the gun
and cable to the mating receptacle inside the
compartment located above the gun connection
made in item 3 above. Make sure that the key­ways are aligned, insert and tighten retaining ring.

SHIELDING GAS

(For Gas Metal Arc Welding Processes)
Customer must provide cylinder of appropriate type

shielding gas for the process being used.
A gas flow regulator, for CO2or Argon blend gas, and

an inlet gas hose are factory provided with the POWER
MIG 255. Install the shielding gas supply as follows:

1. Set gas cylinder on rear platform of POWER MIG

255. Hook chain in place to secure cylinder to rear
of welder.

2. Remove the cylinder cap. Inspect the cylinder
valves and regulator for damaged threads, dirt,
dust, oil or grease. Remove dust and dirt with a
clean cloth.

DO NOT ATTACH THE REGULATOR IF OIL,
GREASE OR DAMAGE IS PRESENT! Inform

your gas supplier of this condition. Oil or grease
in the presence of high pressure oxygen is
explosive.

------------------------------------------------------------------------

3. Stand to one side away from the outlet and open
the cylinder valve for an instant. This blows away
any dust or dirt which may have accumulated in
the valve outlet.

Be sure to keep your face away from the valve out­let when “cracking” the valve.

------------------------------------------------------------------------

4. Attach the flow regulator to the cylinder valve and
tighten the union nut(s) securely with a wrench.

NOTE: If connecting to 100% CO2cylinder, insert
regulator adapter between regulator and cylinder
valve. If adapter is equipped with a plastic washer, be
sure it is seated for connection to the CO2cylinder.

5. Attach one end of the inlet gas hose to the outlet
fitting of the flow regulator, the other end to the
POWER MIG 255 rear fitting, and tighten the
union nuts securely with a wrench.

6. Before opening the cylinder valve, turn the regu­lator adjusting knob counterclockwise until the
adjusting spring pressure is released.

7. Standing to one side, open the cylinder valve
slowly a fraction of a turn. When the cylinder pres­sure gauge pointer stops moving, open the valve
fully.

Never stand directly in front of or behind the flow
regulator when opening the cylinder valve. Always
stand to one side.

------------------------------------------------------------------------

8. The flow regulator is adjustable. Adjust it to the
flow rate recommended for the procedure and
process being used before making the weld.

WARNING

WARNING

CYLINDER may explode if
damaged.

• Gas under pressure is explosive. Always keep
gas cylinders in an upright position and always
keep chained to undercarriage or stationary
support. See American National Standard Z-

49.1, “Safety in Welding and Cutting” pub­lished by the American Welding Society.

WARNING

WARNING

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POWER MIG 255

Section B-1 Section B-1

TABLE OF CONTENTS

- OPERATION SECTION -

Operation ................................................................................................................Section B

Product Description......................................................................................................B-3

Recommended Processes and Equipment..................................................................B-3

Welding Capability........................................................................................................B-3

Limitations ....................................................................................................................B-3

Description of Controls ................................................................................................B-4

Wire Drive Roll..............................................................................................................B-4

Wire Size Conversion Parts..........................................................................................B-4

Procedure for Changing Drive and Idle Roll Sets ........................................................B-5

Wire Reel Loading - Readi-Reels, Spools, or Coils .....................................................B-5

To Mount a 30 lb (14 kg) Readi-Reel Package

(Using the Molded Plastic K363-P Readi-Reel Adapter).......................................B-5

To Mount 10 to 44 lb (4.5-20 kg) Spools (12 in./300 mm Diameter)

or 14 lb (6 kg) Innershield Coils .............................................................................B-5

To Start the Welder.......................................................................................................B-6

Feeding Wire Electrode................................................................................................B-6

Idle Roll Pressure Setting.............................................................................................B-6

Setting Run-In Speed on Standard Power MIG Feeder ..............................................B-6

Fast or Slow Run-In Mode Selection (When Timer Option is not Installed)..........B-6

Instructions to Enter Slow Run-In..........................................................................B-6

Instructions to Enter Fast Run-In...........................................................................B-6

Making a Weld..............................................................................................................B-7

Avoiding Wire Feeding Problems.................................................................................B-7

Fan Control...................................................................................................................B-8

Input Line Voltage Protection .......................................................................................B-8

Wire Feed Overload Protection....................................................................................B-8

Welding Thermal Overload Protection .........................................................................B-8

Overcurrent Protection .................................................................................................B-8

POWER MIG 255

OPERATION

B-2 B-2

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Read entire Operation section before
operating the POWER MIG 255.

ELECTRIC SHOCK can kill.

• Do not touch electrically live parts
or electrode with skin or wet
clothing. Insulate yourself from
work and ground.

• Always wear dry insulating
gloves.

FUMES AND GASES can be
dangerous.

• Keep your head out of fumes.

• Use ventilation or exhaust to
remove fumes from breathing
zone.

WELDING SPARKS can
cause fire or explosion.

• Keep flammable material away.

• Do not weld on closed containers.

ARC RAYS can burn eyes and
skin.

• Wear eye, ear and body protec­tion.

Observe all safety information throughout
this manual.

WARNING

POWER MIG 255

OPERATION

B-3 B-3

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PRODUCT DESCRIPTION

The POWER MIG™ 255 is a complete semiautomatic
constant voltage DC arc welding machine built to meet
NEMA specifications. It combines a constant voltage
power source and a constant speed wire feeder with a
microcomputer-based controller to form a reliable high­performance welding system. Asimple control scheme,
consisting of continuous full range voltage and wire
feed speed controls, provides versatility with ease of
use and accuracy.

Other features include a 2 in. (51 mm) O.D. wire reel
spindle with adjustable brake, an integral gas cylinder
mounting undercarriage, an adjustable CO2or Argon
blend flow regulator with cylinder pressure gauge and
inlet hose, a 12 ft (3.6 m) Magnum 250L GMAW gun
and cable with fixed (flush) nozzle, a 10 ft (3.0 m)
power cable with plug and mating receptacle, and a 10
ft (3.0 m) work cable with clamp.

An Optional Timer kit provides variable burnback con­trol, a spot function, a selectable 4-step trigger inter­lock and adjustable “Run In” for wire starting optimiza­tion. Also optional are a Spool Gun Adapter kit, a Dual
Cylinder Mounting Kit and an Aluminum Feeding Kit for
push feeding with standard built in feeder.

RECOMMENDED PROCESSES
AND EQUIPMENT

The POWER MIG 255 is recommended for GMA
welding processes using 10 to 44 lb (4.5 to 20 kg)
2 in. (51 mm) I.D. spools or Readi-Reel®coils (with
optional adapter) of 0.025 in. through 0.045 in.
(0.6 to 1.2 mm) solid steel, 0.035 in. (0.9 mm)
stainless, 3/64 in. (1.2 mm) aluminum and 0.045 in.
(1.2 mm) Outershield®; as well as 0.035 in. (0.9 mm)
and 0.045 in. (1.2 mm) Innershield®self-shielding
electrodes.

The POWER MIG is factory equipped to feed

0.035 in. (0.9 mm) electrodes and provides tip, guide,
and drive rolls for 0.045 in. (1.2 mm) electrode. It also
includes a 200A, 60% duty cycle (or 250A, 40% duty
cycle) rated, 12 ft (3.6 m) GMAW gun and cable
assembly equipped for these wire sizes. Use of GMAW
processes requires a supply of shielding gas.

WELDING CAPABILITY

The POWER MIG 255 is rated at 250 amps @ 26 volts,
at a 40% duty cycle based on a ten minute cycle time.
It is capable of higher duty cycles at lower output cur­rents and capable of up to 300 Amps at lower duty
cycles.

LIMITATIONS

The POWER MIG 255 MAY NOT operate
satisfactorily if powered with a portable or in-plant
generating system.

POWER MIG 255

OPERATION

B-4 B-4

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DESCRIPTION OF CONTROLS

Power ON/OFF Switch — Place the lever in the “ON”

position to energize the POWER MIG 255. When the
power is on, the red LED display lights illuminate.

Voltage Control — This is a continuous control that
gives full range adjustment of power source output volt­age. It can be adjusted while welding over its 10 to 28
volt range.

Wire Speed Control — This controls the wire feed
speed from 50 to 700 inches per minute (1.2 to

17.8 m/min). The wire speed control can be preset on
the dial to the setting specified on the Procedure Decal
located inside the wire compartment door. Wire speed
is not affected when changes are made in the voltage
control.

WIRE DRIVE ROLL

The drive rolls installed with the POWER MIG each
have two grooves, both for 0.030-0.0035 in.
(0.8-0.9 mm) solid steel electrode. Drive roll size is indi­cated by the stencilling on the exposed side of the drive
roll. If feeding problems occur, then the drive roll may
be reversed or changed. See Procedure for
Changing Drive Roll in this section. This information
also appears on the Procedure Decal on the door
inside the wire compartment. An additional drive roll set
is provided for 0.045 in. (1.2 mm) solid steel electrode,
packaged standard with each machine.

WIRE SIZE CONVERSION PARTS

The POWER MIG 255 is rated to feed 0.025 through

0.045 in. (0.6 to 1.2 mm) solid or cored electrode sizes.
The drive roll kits and Magnum 250L gun and cable

parts are available to feed different sizes and types of
electrodes. See Accessories section.

FIGURE B.1 — OPERATOR CONTROLS

POWER

POWER MIG 255

WIRE SPEED

ON

OFF

VOLTS

LINCOLN

ELECTRIC

POWER MIG 255

OPERATION

B-5 B-5

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PROCEDURE FOR CHANGING
DRIVE AND IDLE ROLL SETS

1. Turn off the power source.

2. Release the pressure on the idle roll by swinging
the adjustable pressure arm down toward the
back of the machine. Lift the cast idle roll assem­bly and allow it to sit in an upright position.

3. Remove the outside wire guide retaining plate by
loosening the two large knurled screws.

4. Twist the drive roll retaining mechanism to the

unlocked position.

5. Wiggle both the metal idle and drive rolls off of
their plastic hubs.

6. Remove the inside wire guide plate.

7. Replace the drive and idle rolls and inside wire
guide with a set marked for the new wire size.

NOTE: Be sure that the gun liner and contact tip are
also sized to match the selected wire size.

8. Manually feed the wire from the wire reel, over the
drive roll groove and through the wire guide and
then into the brass bushing of the gun and cable
assembly.

9. Replace the outside wire guide retaining plate by
tightening the two large knurled screws.
Reposition the adjustable pressure arm to its orig­inal position to apply pressure. Adjust pressure as
necessary.

WIRE REEL LOADING ­READI-REELS, SPOOLS, OR COILS

To Mount a 30 lb (14 kg) Readi-Reel
Package (Using the Molded Plastic K363-P
Readi-Reel Adapter:)

1. Open the wire drive compartment door.

2. Depress the release bar on the retaining collar
and remove it from the spindle. See Figure B.2.

3. Place the optional adapter on the spindle.

4. Re-install the retaining collar. Make sure that the
release bar “pops up” and that the collar retainers
fully engage the retaining ring groove on the
spindle.

5. Rotate the spindle and adapter so the retaining
spring is at the 12 o'clock position.

6. Position the Readi-Reel so that it will rotate in a
direction when feeding so as to be de-reeled from
top of the coil.

7. Set one of the Readi-Reel inside cage wires on
the slot in the retaining spring tab.

FIGURE B.2 — READI-REEL INSTALLATION.

8. Lower the Readi-Reel to depress the retaining
spring and align the other inside cage wires with
the grooves in the molded adapter.

9. Slide cage all the way onto the adapter until the
retaining spring “pops up” fully.

Check to be sure the retaining spring has fully returned
to the locking position and has securely locked the
Readi-Reel cage in place. The retaining spring must
rest on the cage, not on the welding
electrode.

------------------------------------------------------------------------

10. To remove Readi-Reel from adapter, depress
retaining spring tab with thumb while pulling the
Readi-Reel cage from the molded adapter with
both hands. Do not remove adapter from spindle.

To Mount 10 to 44 lb (4.5-20 kg) Spools
(12 in./300 mm Diameter) or 14 lb
(6 kg) Innershield Coils:

(For 13-14 lb (6 kg) innershield coils, a K435 coil
adapter must be used).

1. Open the wire drive compartment door.

2. Depress the release bar on the retaining collar
and remove it from the spindle.

3. Place the spool on the spindle making certain the
spindle brake pin enters one of the holes in the
back side of the spool (Note: an arrow mark on the
spindle lines up with the brake holding pin to
assist in lining up a hole). Be certain the wire
comes off the reel in a direction that it can de-reel
from the top of the coil.

4. Re-install the retaining collar. Make sure that the
release bar “pops up” and that the collar retainers
fully engage the retaining ring groove on the
spindle.

2 IN. O.D.
SPINDLE

ADAPTER

RETAINING

SPRING

BRAKE

HOLDING

PIN

GROOVES

READI-REEL

INSIDE

CAGE

WIRES

RELEASE

BAR

RETAINING

COLLAR

CAUTION

POWER MIG 255

OPERATION

B-6 B-6

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TO START THE WELDER

Turn the Power Switch switch to ON. This lights the red
LED display lights. With the desired voltage and wire
speed selected, operate the gun trigger for welder out­put and to energize the wire feed motor.

FEEDING WIRE ELECTRODE

When triggering, the electrode and drive mecha­nism are electrically “hot” relative to work and
ground and remain “hot” several seconds after the
gun trigger is released.

------------------------------------------------------------------------

NOTE: Check that drive rolls, guide plates, and gun
parts are proper for the wire size and type being used.
Refer to Table C.1 in Accessories section.

1. Turn the Readi-Reel or spool until the free end of
the electrode is accessible.

2. While securely holding the electrode, cut off the
bent end and straighten the first six inches. (If the
electrode is not properly straightened, it may not
feed properly through the wire drive system.)

3. Release the pressure on the idle roll by swinging
the adjustable pressure arm down toward the
back of the machine. Lift the cast idle roll assem­bly and allow it to sit in an upright position. Leave
the outer wire guide plate installed. Manually feed
the wire through the incoming guide bushing and
through the guide plates (over the drive roll
groove). Push a sufficient wire length to assure
that the wire has fed into the gun and cable
assembly without restriction. Reposition the
adjustable pressure arm to its original position to
apply pressure to the wire.

4. Press gun trigger to feed the electrode wire
through the gun.

IDLE ROLL PRESSURE SETTING

The idle roll pressure adjustment knob is set at the fac­tory at the #2 hash mark. This is an approximate set­ting. The optimum idle roll pressure varies with type of
wire, wire diameter, surface conditions, lubrication, and
hardness. As a general rule, hard wires may require
greater pressure, and soft, or aluminum wire, may
require less pressure than the factory setting. The opti­mum idle roll setting can be determined as follows:

1. Press end of gun against a solid object that is
electrically isolated from the welder output and
press the gun trigger for several seconds.

2. If the wire “birdnests”, jams, or breaks at the drive
roll, the idle roll pressure is too great. Back the
adjustment knob out 1/2 turn, run new wire
through gun, and repeat above steps.

3. If the only result was drive roll slippage, loosen the
adjustment knob on the conductor plate and pull
the gun cable forward about 6 in. (15 cm). There
should be a slight waviness in the exposed wire. If
there is not waviness, the pressure is too low.
Tighten the adjustment knob 1/4 turn, reinstall the
gun cable and repeat the above steps.

SETTING RUN-IN SPEED ON STAN­DARD POWER MIG FEEDER

FAST OR SLOW RUN-IN MODE SELECTION
(When Timer Option is not installed)

The POWER MIG 255 is factory set for fast run-in
mode where the wire feed will accelerate directly to the
preset wire feed speed when the gun trigger is closed.

Slow run-in mode may also be selected, where it will
initially feed wire at 50 IPM until output current is
sensed or for 1.0 second, whichever occurs first. It will
then accelerate to the preset wire feed speed.

NOTE: See operating instructions for Timer Option Kit
if it is installed, as it provides its own run-in operation.

INSTRUCTIONS TO ENTER SLOW RUN-IN

1. Turn power OFF on front panel of POWER MIG

255.

2. Turn the wire feed speed dial fully counterclock­wise to minimum.

3. With the gun trigger closed, turn the power ON at
the front panel of the POWER MIG 255.

4. The display will read “SLO run”.

INSTRUCTIONS TO ENTER FAST RUN-IN

1. Turn power OFF on front panel of POWER MIG

255.

2. Turn the wire feed speed dial fully clockwise to
maximum.

3. With the gun trigger closed, turn the power ON at
the front panel of the POWER MIG 255.

4. The display will read “FAS run”.

WARNING

POWER MIG 255

OPERATION

B-7 B-7

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NOTE: Arc starting characteristics may be effected
when using the fast run-in mode since optimum start­ing processes are being overridden.

On the initial trigger closure at power up, no output
power or wire feed will be available until the trigger is
opened and reclosed, regardless of wire feed speed
dial setting.

It is not necessary to repeat either of the above proce­dures each time the unit is powered up. The unit will
remember the run-in mode from the previous power
down and return you to that same state upon your next
power up. Therefore, you need only perform one of the
above procedures when you want to change the run-in
mode.

MAKING A WELD

1. Check that the electrode polarity is correct for the
process being used, then turn the power switch
ON.

2. Set desired arc voltage and wire speed for the
particular electrode wire, material type and thick­ness, and gas (for GMAW) being used. Use the
Application Chart on the door inside the wire com­partment as a quick reference for some common
welding procedures.

3. If T imer Kit is installed, select the desired mode as
described in Operating Instructions for Timer
Kit in the Accessories section. Refer to the
Accessories section for additional welding infor­mation pertaining to Spot mode.

4. Press the trigger to feed the wire electrode
through the gun and cable and then cut the elec­trode within approximately 3/8 in. (10 mm) of the
end of the contact tip [3/4 in. (20 mm)
Outershield®].

NOTE: If set for slow run-in when the trigger is pulled,
the wire feeder feeds wire at low speed regardless of
the set wire feed speed until the welding arc starts or 1
second has elapsed. This feature enhances starting
and makes it easier to set the stickout. The 1 second
limit permits high speed loading of the gun and cable.
To change run-in mode, see Setting Run-In Speed in
this section, if the Timer Kit is not installed, or Timer Kit
Operation section if installed.

5. If welding gas is to be used, turn on the gas sup­ply and set the required flow rate (typically 25-35
CFH; 12-16 liters/min).

6. When using innershield electrode, the gas nozzle
may be removed from the insulation on the end of
the gun and replaced with the gasless nozzle.
This will give improved visibility and eliminate the
possibility of the gas nozzle overheating.

7. Connect work cable to metal to be welded. Work
clamp must make good electrical contact to the
work. The work must also be grounded as stated
in Arc Welding Safety Precautions.

When using an open arc process, it is necessary
to use correct eye, head, and body protection.

------------------------------------------------------------------------

8. Position electrode over joint. End of electrode
may be lightly touching the work.

9. Lower welding helmet, close gun trigger, and
begin welding. Hold the gun so the contact tip to
work distance is about 3/8 in. (10 mm) [3/4 in.
(20 mm) for Outershield].

10. To stop welding, release the gun trigger and then
pull gun away from the work after arc goes out.

11. When no more welding is to be done, close valve
on gas cylinder (if used), momentarily operate gun
trigger to release gas pressure, and turn off
POWER MIG 255.

AVOIDING WIRE FEEDING
PROBLEMS

Wire feeding problems can be avoided by observing
the following gun handling procedures:

1. Do not kink or pull cable around sharp corners.

2. Keep the gun cable as straight as possible when
welding or loading electrode through cable.

3. Do not allow dolly wheels or trucks to run over
cables.

4. Keep cable clean by following the maintenance
instructions.

WARNING

POWER MIG 255

OPERATION

B-8 B-8

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5. Use only clean, rust-free electrode. The Lincoln
electrodes have proper surface lubrication.

6. Replace contact tip when the arc starts to become
unstable or the contact tip end is fused or
deformed.

7. Keep wire reel spindle brake tension to minimum
required to prevent excess reel over-travel which
may cause wire “loop-offs” from coil.

8. Use proper drive rolls and wire drive idle roll pres­sure for wire size and type being used.

FAN CONTROL

The fan is designed to come on automatically when a
weld arc is established. The fan will stay on for a mini­mum of 6 minutes after the weld arc is terminated. The
fan will also stay on when the machine’s welding and
feeding are disabled during thermostatic over temper­ature protection. (See Welding Thermal Overload
Protection.)

INPUT LINE VOLTAGE
PROTECTION

High Line V oltage — If the line voltage exceeds 125%

of rated input voltage, the output will be reduced to the
lower level to protect voltage rating of the capacitor
bank.

Low Line Voltage — You may not be able to get max­imum output from the machine if the line voltage is less
than rated input. The unit will continue to weld, but the
output may be less than what is set.

WIRE FEED OVERLOAD
PROTECTION

The POWER MIG has solid state overload protection
of the wire drive motor. If the motor becomes
overloaded, the protection circuitry turns off the wire
feed speed and gas solenoid. Check for proper size
tip, liner, and drive rolls, for any obstructions or bends
in the gun cable, and any other factors that would
impede the wire feeding. To resume welding, simply
pull the trigger. There is no circuit breaker to reset as
the protection is done with reliable solid state
electronics.

WELDING THERMAL
OVERLOAD PROTECTION

The POWER MIG 255 has built-in protective ther­mostats that respond to excessive temperature. They
open the wire feed and welder output circuits if the
machine exceeds the maximum safe operating tem­perature because of a frequent overload, or high ambi­ent temperature plus overload. The thermostats auto­matically reset when the temperature reaches a safe
operating level and welding and feeding are allowed
again, when gun is retriggered.

OVERCURRENT PROTECTION

The machine will automatically reduce the output if the
load on the machine exceeds 300 to 320 amperes.
This protects the welding power SCR’s from excessive
short circuit currents and from exceeding their temper­ature rating before the thermostats can react.

Welding Procedure Information

Note: See inside cover of machine for additional, commonly used welding procedure information.

70

80

90

100 110 120

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POWER MIG 255

Section C-1 Section C-1

TABLE OF CONTENTS

- ACCESSORIES SECTION -

Accessories ............................................................................................................Section C

Drive Roll Kits ...............................................................................................................C-2

3/64 in. (1.2 mm) Aluminum Feeding Kit (K1703-1) .....................................................C-2

K363P Readi-Reel Adapter ..........................................................................................C-2

Dual Cylinder Mounting Kit (K1702-1)..........................................................................C-2

Alternative Magnum GMAW Gun and Cable Assemblies............................................C-2

Magnum Gun Connection Kit (Optional K466-6) .........................................................C-2

Timer Kit Installation (Optional K1701-1) .....................................................................C-2

Operating Instructions for Timer Kit.......................................................................C-3

Spool Gun Adapter Kit (K1700-1) (Included in the K1692-1).......................................C-4

Making a Weld with the Spool Gun, Spool Gun (K1692-1) Installed.....................C-4

POWER MIG 255

ACCESSORIES

C-2 C-2

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DRIVE ROLL KITS

Refer to Table C.1 for various drive roll kits that are
available for the POWER MIG. All items in Bold are
supplied standard with the POWER MIG.

TABLE C.1 — AVAILABLE DRIVE ROLL KITS.

3/64 in. (1.2 mm) ALUMINUM
FEEDING KIT (K1703-1)

This kit helps push feeding aluminum through standard
machine feeder and gun. It provides gun and wire drive
conversion parts to weld with 3/64 in.
(1.2 mm) aluminum wire. 5356 alloy aluminum wire is
recommended for best push feeding performance.

Kit includes drive rolls and wire guide plate for the wire
drive, liner and two contact tips for the gun, along with
installation instructions.

K363P READI-REEL ADAPTER

The K363P Readi-Reel adapter mounts to the
2 in. spindle. It is needed to mount the 22-30 lb Readi­Reels.

DUAL CYLINDER
MOUNTING KIT (K1702-1)

Permits stable side-by-side mounting of two full size (9
in. dia. x 5 ft. high) gas cylinders with “no lift” loading.
Simple installation and easy instructions provided.
Includes upper and lower cylinder supports, wheel
axles and mounting hardware.

ALTERNATIVE MAGNUM GMAW
GUN AND CABLE ASSEMBLIES

The following Magnum 250Lgun and cable assemblies
are separately available for use with the POWER MIG

255. Each is rated 200 amps 60% duty cycle (or 250
amps 40% duty) and is equipped with the integrated
connector, twist-lock trigger connector, fixed nozzle
and insulator, and includes a liner, diffuser, and contact
tips for the wire sizes specified:

*Fixed Nozzle

MAGNUM GUN CONNECTION KIT
(Optional K466-6)

Using the optional K466-6 Magnum Connection Kit for
the POWER MIG permits use of standard Magnum
200, 300 or 400 gun and cable assemblies.

TIMER KIT INSTALLATION
(Optional K1701-1)

The timer kit adds selectable 4-step trigger interlock,
spot and Run-In functions and manual adjustment of
burnback time. Install as follows, or per the instructions
included with the kit:

Remove all input power to the POWER MIG 255
before proceeding.

------------------------------------------------------------------------

1. Verify that the following items have been included
in the kit:

a. Timer board with harness and panel

assembly.

b. Two screws.

2. Turn the power switch off and disconnect power
from the machine to prepare for kit installation.

Wire Size Drive Roll Kit

0

.023-0.030 in. (0.6-0.8 mm)

KP1696-030S

Solid

0.035 in. (0.9 mm) KP1696-035S

Steel

0.045 in. (1.2 mm) KP1696-045S

Cored

0.035 in. (0.9 mm) KP1697-035C

0.045 in. (1.2 mm) KP1697-045C

Aluminum

3/64 in. (1.2 mm) KP1695-3/64A

WARNING

English Wire Metric Wire

Length Part No. Size Size

10 ft (3.0 m) K533-1

*12 ft (3.6 m) K533-7 0.035 – 0.045 in. 0.9 – 1.2 mm

15 ft (4.5 m) K533-3

POWER MIG 255

ACCESSORIES

C-3 C-3

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3. Using a screwdriver, remove the two screws
securing the lower cover panel to the front of the
machine. Remove the lower cover panel.

4. Attach the rectangular 10-pin plug connector on
the timer kit wiring harness to the mating recepta­cle connector located directly behind the removed
cover panel. Be sure that the latch on the connec­tor is aligned with the one on the board and insert
it until the latch engages.

5. Align the timer panel for installation and carefully
insert the printed circuit board and wiring harness
through the opening. Make sure the wiring har­ness is not pinched between panels or between
printed circuit board and front panel cover.

6. Secure the timer assembly with either the two
supplied screws or with the original screws. The
installation is now complete. Refer to the following
section for operating instructions.

OPERATING INSTRUCTIONS
FOR TIMER KIT

If the optional Timer Kit (K1701-1) is installed, select
the desired mode with the selector switch:

1. Normal Welding mode provides weld power only
while the trigger switch is depressed. This is the
same operation as when the Timer Kit is not
installed.

2. 4-Step Trigger interlock mode eliminates the
need to hold the gun trigger while welding. It oper­ates in 4 steps:

a. Close trigger and establish welding arc.
b. Release trigger and continue welding.
c. Reclose trigger near end of weld.
d. Release trigger again to stop welding.

If the arc is broken while using this feature, the
machine will reset to the “trigger off” condition
automatically.

3. Spot Weld Mode is used for tack welding parts
into position or for spot plug welds to hold thin
sheet metal together prior to manual stitch or con­tinuous welding. To use this feature, adjust the
On-Time (0-5 seconds) as appropriate to obtain
the desired results. Closing the trigger initiates a
single timed spot weld cycle. Plug welds are made
by using a punch to make a 3/16 in. (5 mm) diam­eter hole in the top sheet and arc welding through
the hole into the back sheet.

To make spot plug welds, punch 3/16 in. (5 mm)
holes in the top sheet. Set the Spot Time control
to approximately 1.2 seconds and set the proce­dure for the metal thickness to be welded. Install
spot weld nozzle (if available) on gun and press it
against the top sheet so the top and bottom
sheets are tight together. Close trigger and hold it
closed until the arc goes out. If a spot weld nozzle
is not used, smoother welds will result by moving
the welding wire in a small circle during the weld.

4. Burnback Time control provides manual adjust­ment of the burnback time (0-250 milliseconds) for
any selected welding mode. This control should
be set as low as possible without the wire “stick­ing” in the puddle after each weld. Too long of a
burnback time may form a “ball” on the end of the
wire, or may “flash back” to the gun tip.

5. Run-In Mode is used to adjust the starting wire
feed speed. Starting conditions for certain welding
applications can be improved with adjustment to
the Run-In speed. The control allows for initial
starting speeds from 50 to 150 IPM. After the arc
is started, the set point on the wire feed speed
control will dominate. Note that the Run-in is not
functional with the spool gun. Also note that if
Run-in is set fully counterclockwise to OFF, Run­in speed will equal the preset WFS on the
machine.

POWER MIG 255

ACCESSORIES

C-4 C-4

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SPOOL GUN ADAPTER KIT

Remove all input power to the POWER MIG 255
before proceeding.

------------------------------------------------------------------------

The Spool Gun Adapter Kit provides direct connection
and use of the Spool Gun (with remote speed control)
with the POWER MIG 255 wire feed welder.

It also provides gun trigger switch transfer between the
machine’s use with its feeder gun or the spool gun for
same polarity welding with different wire and gas
processes.

The kit includes a spool gun adapter module assembly
with a single connecting plug, a rear gas inlet setting
with hose and mounting hardware with installation and
operation instructions.

*This kit can only be configured to run a Magnum® SG
Spool Gun OR a Prince® XL Spool Gun at a time; kit is
shipped configured for the Magnum® SG Spool Gun.

MAKING A WELD WITH THE SPOOL GUN,
SPOOL GUN INSTALLED

The POWER MIG control circuitry is designed to
sense either the spool gun (built in) wire feeder trigger
circuitry. After the spool gun adapter kit has been
installed, the spool gun can easily be plugged in and
will be ready to use.

Closing either gun trigger will cause the electrode of
both guns to be electrically “HOT”. Be sure unused gun
is positioned so electrode or tip will not contact metal
case or other metal common to work.

1.Pulling the trigger for the built-in feeder gun:
a. Disables spool gun operation.
b. Closing feeder gun trigger starts feeder gun

welding and makes both

electrodes electri-

cally “HOT”.

2. Pulling SPOOL GUN Trigger:
a. Disables built-in feeder gun operation.
b. Closing spool gun trigger starts spool gun

welding and makes both electrodes electri­cally “HOT”.

3. Operation with POWER MIG 255:
a. Turn the POWER MIG-255 input power

ON.

b. Adjust the voltage control to increase or

decrease your welding voltage.

c. Adjust the wire speed control on the spool

gun to increase or decrease the spool gun
wire feed speed.

4. The following procedure settings for Aluminum

4043 can be used as initial settings for making
test welds to determine final settings:

5. To return to normal POWER MIG 255 welding

release the spool gun trigger and reset feeder
gun voltage procedure setting if necessary.

6. Operation with Timer Option Kit (K1701-1)

installed in Power MIG 255:
All Timer Option Kit functions, except Run-in,

are functional with the spool gun. (See operat­ing instructions for Timer Option Kit.

WARNING

CAUTION

Wire Dia. WFS Setting Arc Voltage

In. (mm) Spool Gun Setting

0.030 in. (0.8 mm) 270 15V

0.035 in. (0.9 mm) 250 16V
3/64 in. (1.2 mm) 240 20V

K2297-1

K2310-1*

Prince®XL Spool Gun with Adaptor Included

Power MIG 255 Spool Gun Adaptor Kit
(connects Magnum®SG Spool Gun OR
Prince®XL Spool Gun

K487-25

Magnum®SG Spool Gun (requires K2310­1 Adaptor Kit

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POWER MIG 255

Section D-1 Section D-1

TABLE OF CONTENTS

- MAINTENANCE SECTION -

Maintenance ...........................................................................................................Section D

Safety Precautions ........................................................................................................D-2

Routine and Periodic Maintenance ...............................................................................D-2

Drive Rolls and Guide Tubes.........................................................................................D-2

Cable Cleaning ..............................................................................................................D-2

Gun Tubes and Nozzles ................................................................................................D-2

Contact Tip and Gas Nozzle Installation.......................................................................D-4

Liner Removal and Replacement ..................................................................................D-4

Liner Removal, Installation, and Trimming Instructions for Magnum 250L ..................D-4

Gun Handle Disassembly ..............................................................................................D-5

Accessories and Expendable Replacement Parts for Magnum 250L Gun and Cable Assemblies

............D-6

POWER MIG 255

MAINTENANCE

D-2 D-2

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SAFETY PRECAUTIONS

• Have a qualified electrician do the maintenance
and troubleshooting work.

• Disconnect the input power off using the dis­connect switch at the main input supply before
working inside machine.

• Unplug the power cable if it is connected to a
receptacle.

------------------------------------------------------------------------

Read the Safety Precautions in the front of this manu­al before working on this machine.

ROUTINE AND PERIODIC
MAINTENANCE

1. Disconnect input AC power supply lines to the
machine before performing periodic maintenance,
tightening, cleaning, or replacing parts.

Perform the following daily:

1. Check that no combustible materials are in the
welding or cutting area or around the machine.

2. Remove any debris, dust, dirt, or materials that
could block the air flow to the machine.

3. Inspect the electrode cables for any slits, punc­tures in the cable jacket, or any condition that
would affect the proper operation of the machine.

Perform Periodically:

Clean the inside of the machine with low pressure air
stream. Clean the following parts. Refer to Figure D.1.

Main transformer and output choke.
Power enhancement choke.
Wire drive assembly.
Capacitor bank.
SCR rectifier bridge and heat sink fins.
Fan motor assembly.
Control printed circuit board.
Snubber printed circuit board.

NOTE: The fan motor has sealed bearings which
require no maintenance.

WARNING

DRIVE ROLLS AND GUIDE TUBES

After every coil of wire, inspect the wire drive mecha­nism. Clean it as necessary by blowing with low pres­sure compressed air. Do not use solvents for cleaning
the idle roll because it may wash the lubricant out of
the bearing. All drive rolls are stamped with the wire
sizes they will feed. If a wire size other than that
stamped on the roll is used, the drive roll must be
changed.

CABLE CLEANING

Clean the cable liner after using approximately 300
pounds (136 kg) of electrode.

1. Remove the cable from the wire feeder and lay it
out straight on the floor.

2. Remove the contact tip from the gun.

3. With an air hose at the gas diffuser end, use low
pressure to gently blow out the cable liner.

Excessive pressure at the start may cause the dirt to
form a plug.

------------------------------------------------------------------------

4. Flex the cable over its entire length and again blow
out the cable.

5. Repeat this procedure until no more dirt comes
out.

GUN TUBES AND NOZZLES

1. Replace worn contact tips as required.

2. Remove spatter from the inside of the gas nozzle
and tip every 10 minutes of arc time or as required.

CAUTION

POWER MIG 255

MAINTENANCE

D-3 D-3

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FIGURE D.1 — COMPONENT LOCATIONS.

CONTROL PC

BOARD

POWER

ENHANCEMENT

CHOKE

OUTPUT

CHOKE

MAIN

TRANSFORMER

SCR

RECTIFIER

BRIDGE

CAPACITOR

BANK

SNUBBER

PC BOARD

WIRE DRIVE

ASSEMBLY

FAN

MOTOR

ASSEMBLY

POWER MIG 255

MAINTENANCE

D-4 D-4

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CONTACT TIP AND GAS
NOZZLE INSTALLATION

1. Choose the correct size contact tip for the elec­trode being used (wire size is stenciled on the side
of the contact tip) and screw it snugly into the gas
diffuser.

a. Be sure the nozzle insulator is fully screwed

onto the gun tube and does not block the gas
holes in the diffuser.

2. Slip or screw the appropriate gas nozzle onto the
nozzle insulator.

NOTE: Either a standard 0.50 in. (12.7 mm) or option­al 0.62 in. (15.9 mm) I.D. slip-on gas nozzle may be
used and should be selected based on the welding
application.

3. Adjust the gas nozzle as appropriate for the
GMAW process to be used.

a. Typically, the contact tip end should be flush

to extended 0.12 in. (3.2 mm) for the short­circuiting transfer process and recessed 0.12
in. (3.2 mm) for spray transfer.

LINER REMOVAL AND
REPLACEMENT

NOTE: When you change wire size, a replacement

gas diffuser is required. Use the table below to select
the proper diffuser so the liner is held securely in place.

LINER REMOVAL, INSTALLATION,
AND TRIMMING INSTRUCTIONS
FOR MAGNUM 250L

NOTE: The variation in cable lengths prevents the

interchangeability of liners between guns. Once a liner
has been cut for a particular gun, it should not be
installed in another gun unless it can meet the liner cut
off length requirement. Liners are shipped with the
jacket of the liner extended the proper amount.

1. Remove the gas nozzle and nozzle insulator. See
Figure D.2.

2. Locate the set screw in the gas diffuser which is
used to hold the old liner in place.

3. Loosen the set screw with a 5/64 in. (2.0 mm) Allen
wrench.

4. Remove the gas diffuser from the gun tube.

5. Lay the gun and cable out straight on a flat surface.

6. Loosen the set screw located in the brass cable
connector at the feeder end of the cable and pull
the liner out of the cable.

7. Insert a new untrimmed liner into the connector
end of the cable.

a. Check the liner bushing stencil to make sure

it is the appropriate one for the wire size being
used.

8. Fully seat the liner bushing into the connector.

Diameter of

Electrodes Used

0.025-0.030 in. Steel
(0.6-0.8 mm)

0.035-0.045 in. Steel
(0.9-1.2 mm)

3/64 in. Aluminum

(1.2 mm)

Replacement

Liner

Part Number

KP1934-2

KP1934-1

KP1955-1

Size Stenciled on

End of Liner

Bushing

0.030 in. (0.8 mm)

0.045 in. (1.2 mm)

3/64 in. (1.2 mm)

Fixed Nozzle Gas

Diffuser Part No.

(and Stencil)

KP2026-3

KP2026-3

KP2026-3

Adjustable Nozzle

Gas Diffuser Part

No. (and Stencil)

KP2026-2

KP2026-1B1

KP2026-1B1

POWER MIG 255

MAINTENANCE

D-5 D-5

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GUN HANDLE DISASSEMBLY

The internal parts of the gun handle may be inspected
or serviced if necessary.

The gun handle consists of two halves that are held
together with a collar on each end.

To open up the handle:

1. Turn the collars approximately 60 degrees coun­terclockwise (the same direction as removing a
right hand thread) until the collar reaches a stop.

2. Pull the collar off the gun handle.

NOTE: If the collars are difficult to turn, position the
gun handle against a corner, place a screwdriver
against the tab on the collar and give the screwdriver a
sharp blow to turn the collar past an internal locking rib.
See Figure D.3.

FIGURE D.3 — GUN HANDLE DISASSEMBLY.

9. Tighten the setscrew on the brass cable
connector.

NOTE: Do not install the gas diffuser onto the end of
the gun tube at this time.

10. Straighten the cable with the gas nozzle and noz­zle insulator removed from the gun tube.

11.Trim the liner to the length shown in Figure D.2.

FIGURE D.2 — LINER MAINTENANCE.

12. Remove any burrs from the end of the liner.

13. Screw the gas diffuser onto the end of the gun tube
and tighten.

NOTE: Be sure the gas diffuser is correct for the liner
being used. (See table and diffuser stencil.)

14. Slightly tighten the set screw in the side of the gas
diffuser against the cable liner using 5/64 in.
(2.0 mm) Allen wrench.

This screw should only be gently tightened. Over tight­ening will split or collapse the liner and cause poor wire
feeding.

------------------------------------------------------------------------

BRASS CABLE

CONNECTOR

SET

SCREW

GAS DIFFUSER

NOZZLE INSULATOR

GAS NOZZLE

1-1/4" (1.25)

(31.8MM)

LINER TRIM

LENGTH

CAUTION

POWER MIG 255

MAINTENANCE

D-6 D-6

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ACCESSORIES AND EXPENDABLE REPLACEMENT PARTS FOR
MAGNUM 250L GUN AND CABLE ASSEMBLIES

*Included with Power MIG 255.

**Requires S19418-1 Gas Diffuser Assembly.

METRIC SIZE

0.6 - 0.8 mm

0.9 - 1.2 mm

1.2 mm (Alum. Wire)

0.6 mm

0.8 mm

0.9 mm

1.2 mm

0.9 mm

1.2 mm

0.6 mm

0.8 mm

0.9 mm

1.2 mm

1.2 mm (Alum. Wire)

9.5 mm

12.1 mm

15.9 mm

9.5 mm

15.9 mm

15.9 mm

0.6-1.2 mm

12.7 mm

15.9 mm

0.6-0.8 mm

0.9-1.2 mm

ENGLISH SIZE

0.025-0.030 in.

0.035-0.045 in.

3/64 in. (Alum. Wire)

0.025 in.

0.030 in.

0.035 in.

0.045 in.

0.035 in.

0.045 in.

0.025 in.

0.030 in.

0.035 in.

0.045 in.

3/64 in. (Alum. wire)

3/8 in.
1/2 in.
5/8 in.

3/8 in.
5/8 in.
5/8 in.

0.025-0.045 in.
1/2 in.

5/8 in.

0.25-0.030 in.

0.35-0.045 in.

PART NO.

KP1934-2
KP1934-1
KP1955-1

KP2020-6B1
KP2020-7B1
KP2020-1B1*
KP2020-2B1*

KP2021-1B1
KP2021-2B1

KP2021-5B1
KP2021-6B1
KP2022-1B1
KP2022-2B1

KP2010-5B1

KP1931-1
KP1931-2*
KP1931-3

KP1930-1
KP1930-2
KP1930-3

KP2026-3*
KP1935-2

KP1935-1
KP2025-1
KP2026-2

KP2026-1
KP1947-1**

KP2015-1*
KP2041-1

DESCRIPTION

Cable Liner
For 15 ft (4.5 m) or Shorter Cable

Contact Tips

Standard Duty

Heavy Duty

Tapered

Tab (For Aluminum)

Gas Nozzles

Fixed

(Flush)

(Recessed)

(Requires: Gas Diffuser Assembly)

Adjustable Slip-On

(Requires: Nozzle Insulator Assembly)
(Requires: Gas Diffuser Assembly)

Gasless Nozzle

(for Innershield®)

Gun Tube Assembly

Standard (60 Degrees)
45 Degrees

TABLE D.2

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POWER MIG 255

Section E-1 Section E-1

Theory of Operation ...............................................................................................Section E

Input Line Voltage and Main Transformer.....................................................................E-2

Output Rectification and Feedback Control.................................................................E-3

Constant Voltage Output ..............................................................................................E-4

Wire Drive Motor and Feedback...................................................................................E-5

Thermal and Overload Protection.................................................................................E-6

Overcurrent Protection...........................................................................................E-6

Wire Feed Overload Protection..............................................................................E-6

SCR Operation..............................................................................................................E-7

TABLE OF CONTENTS

- THEORY OF OPERATION SECTION -

FIGURE E.1 – BLOCK LOGIC DIAGRAM

LINE

SWITCH

RECONNECT

MAIN

TRANSFORMER

SNUBBER

BOARD

RECTIFIER

DIODE

BRIDGE

ARC

VOLTAGE

WIRE

SPEED

GAS

SOLENOID

FAN

MOTOR

CONTROL

BOARD

WIRE

DRIVE

MOTOR

TACH

GUN TRIGGER

FEEDBACK

115 VAC

30 VAC

G
A
T
E

S

I
G
N
A

L

SCR

RECTIFIER

POWER

ENHANCEMENT

CHOKE

OUTPUT

CHOKE

C
A
P
A
C

I
T
O
R
S

F
E
E
D
B
A
C
K

NEGATIVE
TERMINAL

POSITIVE

TERMINAL

SHUNT

POWER MIG 255

THEORY OF OPERATION

E-2 E-2

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INPUT LINE VOLTAGE
AND MAIN TRANSFORMER

The desired single phase input power is connected to
the POWER MIG 255 through a line switch located on
the front panel.

A reconnect panel allows the user to configure the
machine for the desired input voltage. This AC input
voltage is applied to the primary of the main trans­former. The main transformer converts the high
voltage, low current input power to a low voltage, high
current output. In addition, the main transformer also
has an isolated center tapped 30 V AC auxiliary winding
that supplies power to the Control Board for the SCR

NOTE: Unshaded areas of Block Logic

Diagram are the subject of discussion

FIGURE E.2 — INPUT LINE VOLTAGE AND MAIN TRANSFORMER.

LINE

SWITCH

RECONNECT

MAIN

TRANSFORMER

SNUBBER

BOARD

RECTIFIER

DIODE

BRIDGE

ARC

VOLTAGE

WIRE

SPEED

GAS

SOLENOID

FAN

MOTOR

CONTROL

BOARD

WIRE

DRIVE

MOTOR

TACH

GUN TRIGGER

FEEDBACK

115 VAC

30 VAC

G
A
T
E

S

I
G
N
A
L

SCR

RECTIFIER

POWER

ENHANCEMENT

CHOKE

OUTPUT

CHOKE

C
A
P
A
C

I
T
O
R
S

F
E
E
D
B
A
C
K

NEGATIVE
TERMINAL

POSITIVE

TERMINAL

SHUNT

gate drive circuitry. The weld power windings connect
to the main SCR Rectifier and via the Snubber Board
to the Rectifier Diode Bridge. This AC voltage is recti­fied and then regulated by the control board. The
resultant +15 VDC and +5 VDC voltages supply power
to the control board circuitry . The 115 VAC winding (X8
and X9) supplies power, through the control board, to
the thermostatically controlled fan motor.

The fan is designed to come on automatically when
weld arc is established. The fan will stay on for a mini­mum of six minutes after the weld arc is terminated.
The fan will also stay on when the machine’s welding
and feeding are disabled during thermostatic over-tem­perature protection. (See Thermal and Overload
Protection.)

POWER MIG 255

THEORY OF OPERATION

E-3 E-3

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OUTPUT RECTIFICATION AND
FEEDBACK CONTROL

The AC output from the main transformer secondary
weld winding is rectified and controlled through the
SCR rectifier assembly . Output voltage and current are
sensed at the shunt and output terminals and are fed
back to the control board. The control board compares

NOTE: Unshaded areas of Block Logic

Diagram are the subject of discussion

LINE

SWITCH

RECONNECT

MAIN

TRANSFORMER

SNUBBER

BOARD

RECTIFIER

DIODE

BRIDGE

ARC

VOLTAGE

WIRE

SPEED

GAS

SOLENOID

FAN

MOTOR

CONTROL

BOARD

WIRE

DRIVE

MOTOR

TACH

GUN TRIGGER

FEEDBACK

115 VAC

30 VAC

G
A
T
E

S

I
G
N
A
L

SCR

RECTIFIER

POWER

ENHANCEMENT

CHOKE

OUTPUT

CHOKE

C
A
P
A
C

I
T
O
R
S

F
E
E
D
B
A
C
K

NEGATIVE
TERMINAL

POSITIVE

TERMINAL

SHUNT

FIGURE E.3 — OUTPUT RECTIFICATION AND FEEDBACK.

the commands of the ARC Voltage Control poten­tiometer with the feedback signals. The appropriate
gate firing pulses are generated by the control board
and applied to the SCR rectifier assembly. The control
board controls the firing of the SCRs, thus controlling
the output of the machine. See SCR Operation. The
control board also powers and commands the gas
solenoid, fan motor, and the wire drive motor.

POWER MIG 255

THEORY OF OPERATION

E-4 E-4

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CONSTANT VOLTAGE OUTPUT

The controlled DC output from the SCR rectifier
assembly is supplied to the power factor enhancement
choke which limits the rate at which the supply current
rises through the capacitors. The DC output from the

NOTE: Unshaded areas of Block Logic

Diagram are the subject of discussion

FIGURE E.4 — CONSTANT VOLTAGE OUTPUT.

LINE

SWITCH

RECONNECT

MAIN

TRANSFORMER

SNUBBER

BOARD

RECTIFIER

DIODE

BRIDGE

ARC

VOLTAGE

WIRE

SPEED

GAS

SOLENOID

FAN

MOTOR

CONTROL

BOARD

WIRE

DRIVE

MOTOR

TACH

GUN TRIGGER

FEEDBACK

115 VAC

30 VAC

G
A
T
E

S

I
G
N
A

L

SCR

RECTIFIER

POWER

ENHANCEMENT

CHOKE

OUTPUT

CHOKE

C
A
P
A
C

I
T
O
R
S

F
E
E
D
B
A
C
K

NEGATIVE
TERMINAL

POSITIVE

TERMINAL

SHUNT

power factor enhancement choke is filtered by the
capacitor bank resulting in a constant voltage DC out­put. Since the output choke is in series with the posi­tive leg of the rectifier and also in series with the gun
and welding load, a filtered constant voltage output is
applied to the output terminals of the machine.

POWER MIG 255

THEORY OF OPERATION

E-5 E-5

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WIRE DRIVE MOTOR
AND FEEDBACK

The wire drive motor is controlled by the control board.
A motor speed feedback signal is generated at the
motor tach and sent to the control board. The control

NOTE: Unshaded areas of Block Logic

Diagram are the subject of discussion

FIGURE E.5 — WIRE DRIVE MOTOR AND FEEDBACK.

LINE

SWITCH

RECONNECT

MAIN

TRANSFORMER

SNUBBER

BOARD

RECTIFIER

DIODE

BRIDGE

ARC

VOLTAGE

WIRE

SPEED

GAS

SOLENOID

FAN

MOTOR

CONTROL

BOARD

WIRE

DRIVE

MOTOR

TACH

GUN TRIGGER

FEEDBACK

115 VAC

30 VAC

G
A
T
E

S

I
G
N
A
L

SCR

RECTIFIER

POWER

ENHANCEMENT

CHOKE

OUTPUT

CHOKE

C
A
P
A
C

I
T
O
R
S

F
E
E
D
B
A
C
K

NEGATIVE
TERMINAL

POSITIVE

TERMINAL

SHUNT

board compares this feedback signal with the com­mands set forth by the Wire Speed Control poten­tiometer and sends the appropriate armature voltage to
the wire drive motor. The drive motor speed is thus
controlled which in turn regulates the electrode wire
feed speed through the gun.

POWER MIG 255

THEORY OF OPERATION

E-6 E-6

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THERMAL AND OVERLOAD
PROTECTION

The POWER MIG 255 has built-in protective ther­mostats that respond to excessive temperatures. One
is located on the output choke. The other thermostat is
located on the SCR heat sink assembly . They open the
wire feed and welder output circuits if the machine
exceeds the maximum safe operating temperature.
This can be caused by a frequent overload, or high
ambient temperature.

The thermostats are self-resetting once the machine
cools sufficiently. If the thermostat shutdown is caused
by excessive output or duty cycle and the fan is oper­ating normally , the power switch may be left on and the
reset should occur within a 15 minute period. If the fan
is not turning or the air intake louvers are obstructed,
then the input power must be removed and the fan
problem or air obstruction be corrected.

OVERCURRENT PROTECTION

The machine will automatically reduce the output if the
load on the machine exceeds 300 to 320 amperes.
This protects the welding power SCR’s from excessive
short circuit currents and from exceeding their temper­ature rating before the thermostats can react.

WIRE FEED OVERLOAD PROTECTION

The POWER MIG has solid state overload protection
of the wire drive motor. If the motor becomes over­loaded, the protection circuitry turns off the wire feed
speed and gas solenoid. Check for proper size tip liner,
and drive rolls, for any obstructions or bends in the gun
cable, and any other factors that would impede the wire
feeding. To resume welding, simply pull the trigger.
There is no circuit breaker to reset, as the protection is
done with reliable solid state electronics.

POWER MIG 255

THEORY OF OPERATION

E-7 E-7

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SCR OPERATION

A silicon controlled rectifier (SCR) is a three terminal
device used to control rather large currents to a load.
An SCR acts very much like a switch. See Figure E.6
for a graphical representation of SCR operation. When
a gate signal is applied to the SCR it is turned ON and
there is current flow from anode to cathode. In the ON
state the SCR acts like a closed switch. When the SCR
is turned OFF there is no current flow from anode to
cathode thus the device acts like an open switch. As
the name suggests, the SCR is a rectifier, so it passes
current only during positive half cycles of the AC sup­ply. The positive half cycle is the portion of the sine
wave in which the anode of the SCR is more positive
than the cathode.

When an AC supply voltage is applied to the SCR, the
device spends a certain portion of the AC cycle time in

the off state and the remainder of the time in the on
state. The amount of time spent in the ON state is con­trolled by the gate.

An SCR is fired by a short burst of current into the gate.
This gate pulse must be more positive than the cath­ode voltage. Since there is a standard PN junction
between gate and cathode, the voltage between these
terminals must be slightly greater than 0.6V. Once the
SCR has fired it is not necessary to continue the flow
of gate current. As long as current continues to flow
from anode to cathode the SCR will remain on. When
the anode to cathode current drops below a minimum
value, called holding current, the SCR will shut off. This
normally occurs as the AC supply voltage passes
through zero into the negative portion of the sine wave.
If the SCR is turned on early in the positive half cycle,
the conduction time is longer resulting in greater SCR
output. If the gate firing occurs later in the cycle the
conduction time is less resulting in lower SCR output.

FIGURE E.6 — SCR OPERATION.

INPUT

OUTPUT

CATHODE

ANODE

GATE

NOTE: AS THE GATE
PULSE IS APPLIED
LATER IN THE CYCLE
THE SCR OUTPUT
IS DECREASED.

POWER MIG 255

NOTES

E-8 E-8

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POWER MIG 255

Section F-1 Section F-1

TABLE OF CONTENTS

- TROUBLESHOOTING & REPAIR SECTION -

Troubleshooting & Repair Section ........................................................................Section F

How to Use Troubleshooting Guide..............................................................................F-2

PC Board Troubleshooting Procedures and Replacement...........................................F-3

Troubleshooting Guide..................................................................................................F-4

Test Procedures

Main Transformer Test ..........................................................................................F-11

Rectifier Diode Bridge Test ...................................................................................F-15

Static SCR Rectifier Assembly Test .....................................................................F-19

Active SCR Rectifier Assembly Test .....................................................................F-23

Wire Drive Motor and Tachometer Feedback Test...............................................F-27

Oscilloscope Waveforms

Normal Open Circuit Voltage Waveform ..............................................................F-31

Typical Output Voltage Waveform - Machine Loaded..........................................F-32

Abnormal Output Voltage Waveform - Machine Loaded One Output SCR Not Functioning .............

F-33

Abnormal Open Circuit Voltage Output Capacitor Bank Not Functioning...........F-34

Typical SCR Gate Voltage Waveform ...................................................................F-35

Replacement Procedures

Control PC Board Removal and Replacement.....................................................F-37

Wire Drive Assembly Removal and Replacement................................................F-41

SCR Output Rectifier Removal and Replacement ...............................................F-45

Capacitor Bank Removal and Replacement ........................................................F-49

Main Transformer and Output Choke Removal and Replacement ......................F-51

Fan Motor and Fan Removal and Replacement ..................................................F-55

Retest After Repair......................................................................................................F-57

HOW TO USE TROUBLESHOOTING GUIDE

Service and repair should be performed by only Lincoln Electric Factory Trained Personnel.
Unauthorized repairs performed on this equipment may result in danger to the technician and machine
operator and will invalidate your factory warranty. For your safety and to avoid Electrical Shock, please
observe all safety notes and precautions detailed throughout this manual.

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POWER MIG 255

TROUBLESHOOTING & REPAIR

F-2 F-2

CAUTION

This Troubleshooting Guide is provided to help
you locate and repair possible machine
malfunctions. Simply follow the three-step
procedure listed below.

Step 1. LOCATE PROBLEM (SYMPTOM). Look
under the column labeled “PROBLEM
(SYMPTOMS)”. This column describes possible
symptoms that the machine may exhibit. Find
the listing that best describes the symptom that
the machine is exhibiting. Symptoms are
grouped into three main categories: Feeding
Problems and Welding Problems.

Step 2. PERFORM EXTERNAL TESTS. The
second column, labeled “POSSIBLE AREAS OF
MISADJUSTMENT(S)”, lists the obvious external
possibilities that may contribute to the machine
symptom. Perform these tests/checks in the
order listed. In general, these tests can be
conducted without removing the case
wrap-around cover.

Step 3. PERFORM COMPONENT TESTS. The
last column, labeled “Recommended Course of
Action” lists the most likely components that may
have failed in your machine. It also specifies the
appropriate test procedure to verify that the
subject component is either good or bad. If there
are a number of possible components, check the
components in the order listed to eliminate one
possibility at a time until you locate the cause of
your problem.

All of the referenced test procedures referred to in
the Troubleshooting Guide are described in detail
at the end of this chapter. Refer to the
Troubleshooting and Repair Table of Contents to
locate each specific Test Procedure. All of the
referred to test points, components, terminal
strips, etc., can be found on the referenced
electrical wiring diagrams and schematics. Refer
to the Electrical Diagrams Section Table of
Contents to locate the appropriate diagram.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
1-888-935-3877.

POWER MIG 255

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TROUBLESHOOTING & REPAIR

F-3 F-3

Sometimes machine failures appear to be due to PC
board failures. These problems can sometimes be
traced to poor electrical connections. To avoid prob­lems when troubleshooting and replacing PC boards,
please use the following procedure:

1. Determine to the best of your technical ability
that the PC board is the most likely component
causing the failure symptom.

2. Check for loose connections at the PC board
to assure that the PC board is properly
connected.

3. If the problem persists, replace the suspect PC
board using standard practices to avoid static
electrical damage and electrical shock. Read
the warning inside the static resistant bag and
perform the following procedures:

PC board can be damaged by static electricity.

- Remove your body’s static
charge before opening the static­shielding bag. Wear an anti-static
wrist strap. For safety, use a 1
Meg ohm resistive cord connected
to a grounded part of the
equipment frame.

- If you don’t have a wrist strap,
touch an un-painted, grounded,
part of the equipment frame. Keep
touching the frame to prevent
static build-up. Be sure not to
touch any electrically live parts at
the same time.

- Tools which come in contact with the PC board must
be either conductive, anti-static or static-dissipative.

ELECTRIC SHOCK
can kill.

•

Have an electrician install and
service this equipment. Turn the
input power OFF at the fuse box
before working on equipment. Do
not touch electrically hot parts.

- Remove the PC board from the static-shielding bag
and place it directly into the equipment. Don’t set the
PC board on or near paper, plastic or cloth which
could have a static charge. If the PC board can’t be
installed immediately, put it back in the static-shield­ing bag.

- If the PC board uses protective shorting jumpers,
don’t remove them until installation is complete.

- If you return a PC board to The Lincoln Electric
Company for credit, it must be in the static-shielding
bag. This will prevent further damage and allow prop­er failure analysis.

4. Test the machine to determine if the failure

symptom has been corrected by the
replacement PC board.

NOTE: It is desirable to have a spare (known good)
PC board available for PC board troubleshooting.

NOTE

: Allow the machine to heat up so that all

electrical components can reach their operating
temperature.

5. Remove the replacement PC board and

substitute it with the original PC board to
recreate the original problem.

a. If the original problem does not reappear by

substituting the original board, then the PC
board was not the problem. Continue to look
for bad connections in the control wiring
harness, junction blocks, and terminal strips.

b. If the original problem is recreated by the

substitution of the original board, then the PC
board was the problem. Reinstall the
replacement PC board and test the machine.

6. Always indicate that this procedure was

followed when warranty reports are to be
submitted.

NOTE

: Following this procedure and writing on the

warranty report, “INSTALLED AND SWITCHED PC
BOARDS TO VERIFY PROBLEM,” will help avoid
denial of legitimate PC board warranty claims.

PC BOARD TROUBLESHOOTING PROCEDURES

ATTENTION
Static-Sensitive
Devices
Handle only at
Static-Safe
Workstations

WARNING

CAUTION

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TROUBLESHOOTING & REPAIR

F-4 F-4

POWER MIG 255

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
1-888-935-3877.

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

Major Physical or Electrical Damage is Evident

Machine is dead — no open circuit voltage output and no wire feed when gun trigger is pulled. The machine display may be lit.

1. Contact your local Lincoln
Electric Authorized Field Service
Facility.

1. Make certain that the input
power switch is in the "ON" posi­tion.

2. Check the input voltage at the
machine. Input voltage must
match the rating plate and the
reconnect panel.

3. Blown or missing fuses in the
input line.

4. The thermostats may be open
due to machine overheating. If
machine operates normally after
a cooling off period then check
for proper fan operation and
ventilation. Make certain that the
machine's duty cycle is not
being exceeded.

5. Check the trigger circuit. Leads
#324 to #325 should have conti­nuity (zero ohms) when the gun
trigger is pulled. If not then the
gun may be faulty — replace.

6. Make sure unit is not connected
to a portable generator.

1. Contact The Lincoln Electric
Service Dept. 1-888-935-3877

1. Check input power switch (S1).
It may be faulty.

2. Check for lose or broken wires
at the reconnect panel.

3. Perform Main Transformer
Test.

4. Perform Rectifier Diode Bridge
Test.

5. Check the thermostats and
associated leads for loose or
broken connections. See wiring
diagram.

6. The control board may be faulty.
Replace.

OUTPUT PROBLEMS

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TROUBLESHOOTING & REPAIR

F-5 F-5

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

POWER MIG 255

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
1-888-935-3877.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

No open circuit voltage output but
wire feeds normally when gun trig­ger is pulled.

Wire feeds but welding output is low causing wire to “stub”. Welds are “cold”. Machine cannot obtain full rated output of 200 amps at 28 volts.

1. Check the input voltage at the
machine. Input voltage must
match the rating plate and the
reconnect panel.

2. The gun may be faulty. Check
or replace.

1. Make sure that the proper wire
and procedures are being used.

2. Check gun and work cable for
loose or faulty connections.

1. Check for loose or broken con­nections at the output terminals,
the chokes, the capacitor bank
and all heavy current carrying
leads. See Wiring Diagram.

2. Make sure that the transformer
secondary leads are securely
connected to the SCR rectifier
assembly.

3. Perform the SCR Rectifier
Assembly Tests.

4. Perform Main Transformer
Test.

5. The control board may be faulty.
Replace.

1. Check for loose or faulty con­nections of the heavy current
carrying leads.

2. The output capacitor bank may
be faulty. Check for loose con­nections at the capacitors. Also
check for leaky capacitors.
Replace if necessary.

WARNING: The liquid elec­trolyte in these capacitors is
toxic. Avoid contact with any
portion of your body.

3. Perform the SCR Rectifier
Assembly Tests.

4. Perform the Main Transformer
Test.

5. The control board may be faulty.
Replace.

OUTPUT PROBLEMS (Continued)

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-6 F-6

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CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
1-888-935-3877.

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

The output voltage and wire feed is present continuously or pulsing when gun trigger is NOT activated.

The output voltage is present contin­uously when gun trigger is NOT acti­vated.

1. Remove the gun. If the problem
is resolved the gun trigger circuit
is faulty. Repair or replace.

2. If problem persists when gun
assembly is removed from
machine, then the problem is
within the POWER MIG 255.

Contact your local Lincoln Electric
Authorized Field Service Facility.

1. Check the machine's internal
trigger leads for grounds or
shorts. See Wiring Diagram.

2. The control board may be faulty.
Replace.

1. Perform the SCR Rectifier
Assembly Tests.

2. The control board may be faulty.
Replace.

OUTPUT PROBLEMS (Continued)

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-7 F-7

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CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
1-888-935-3877.

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

No control of arc voltage. Wire feed­ing is normal.

There is no gas flow when gun trig­ger is pulled. Wire feeds and weld
voltage is present.

The machine stops feeding wire while welding.

1. The arc voltage control poten­tiometer may be dirty. Rotate
several times and check if prob­lem is resolved.

1. Check gas source and hoses for
leaks or kinks.

1. Check for adequate wire supply.

2. Check for mechanical restric­tions in the wire feeding path.
The gun may be clogged.

3. Check gun liner and tip are cor­rect for wire size being used.

4. Check spindle for ease of rota­tion.

5. If Timer Option Kit is installed,
make sure spot timer knob is set
to OFF.

1. The arc voltage control poten­tiometer may be faulty . Check or
replace. See Wiring Diagram.

2. Perform the SCR Rectifier
Assembly Tests.

3. The control board may be faulty.
Replace.

1. Check the gas solenoid by dis­connecting it from the control
board (Plug J8) and applying a
12 VDC external supply to the
gas solenoid. If the solenoid
does NOT activate then it may
be faulty. Replace.

2. The control broad may be faulty.
Replace.

1. Check the motor armature cur­rent. Normal armature current is

2.0 to 2.7 amps maximum. If
the motor armature current is
normal the control board may be
faulty. Replace.

2. If the motor armature current is
high (over 2.7 amps) and there
are NO restrictions in the wire
feeding path then the motor or
gear box may be defective.
Replace.

FUNCTION PROBLEMS

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-8 F-8

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CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
1-888-935-3877.

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

No control of wire feed speed. Other machine functions are normal

There is no wire feed when gun trig­ger is pulled. Normal open circuit
voltage is present.

1. The wire feed speed control
may be dirty. Rotate several
times and check if problem is
resolved.

1. Check for adequate wire supply.

2. If the drive rolls are turning then
check for a mechanical restric­tion in the wire feed path.

3. The gun liner may be clogged.
Check or replace.

4. If the drive rolls are NOT turning
when the gun trigger is pulled
then contact your local Lincoln
Electric Authorized Field Service
Facility.

1. The Wire Speed Control poten­tiometer may be faulty . Check or
replace. See Wiring Diagram.

2. Perform the Wire Drive Motor

and Tachometer Feedback
Test.

3. The control board may be faulty.
Replace.

1. Perform the Wire Drive Motor

and Tachometer Feedback
Test.

2. The Wire Feed Control poten­tiometer may be faulty . Check or
replace. See Wiring Diagram.

3. The control board may be faulty.
Replace.

WIRE FEEDING PROBLEMS

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-9 F-9

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CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
1-888-935-3877.

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

The arc is unstable and or “hunting”.

Weld bead is narrow or ropy. May
have porosity with electrode stub­bing into plate.

1. Check for worn or melted con­tact tip.

2. Check for loose or faulty con­nections on the work and elec­trode cables.

3. Make sure electrode polarity or
welding process being used, is
correct.

4. Check for rusty or dirty wire.

5. Make sure machine settings and
gas are correct for process
being used.

1. Make sure the weld procedure
and electrode polarity is correct
for the process being used.

2. Make sure shielding gas is cor­rect and flow is proper.

3. Make sure the weld joint is not
“contaminated”.

1. Check for loose connections at
the output terminals, the
chokes, the capacitor bank and
all heavy current carrying leads.
See Wiring Diagram.

2. Make sure that the transformer
secondary leads are securely
connected to the SCR rectifier
assembly.

3. The output capacitor bank may
be faulty. Check for loose con­nections at the capacitors. Also
check for leaky capacitors.
Replace if necessary.

WARNING: The liquid elec­trolyte in these capacitors is
toxic. Avoid contact with any
portion of your body.

4. Perform the SCR Rectifier
Assembly Tests.

5. The control board may be faulty.
Replace.

1. The output capacitor bank may
be faulty. Check for loose con­nections at the capacitors. Also
check for leaky capacitors.
Replace if necessary.

WARNING: The liquid elec­trolyte in these capacitors is
toxic. Avoid contact with any
portion of your body.

2. The control board may be faulty.
Replace.

WELDING PROBLEMS

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-10 F-10

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CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
1-888-935-3877.

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

The contact tip seizes in the gas diffuser.

The welding arc is variable and sluggish.

The arc striking is poor.

1. The tip being over heated due to
excessive current and/or high
duty cycle welding.

2. A light application of high tem­perature anti-sieze lubricant
(such as Lincoln E2607
Graphite Grease) may be
applied to the contact tip
threads.

1. Check the welding cable con­nections for loose or faulty con­nections.

2. Make sure the wire feed speed,
voltage, and shielding gas are
correct for the process being
used.

1. Check the welding cable con­nections for loose or faulty con­nections.

2. Make sure the wire feed speed,
voltage, and shielding gas are
correct for the process being
used.

1. Make sure tip is tight in diffuser.

1. Perform the SCR Rectifier

Assembly Tests.

2. The control board may be faulty.
Replace.

1. The output capacitor bank may
be faulty. Check for loose con­nections at the capacitors. Also
check for leaky capacitors.
Replace if necessary.

WARNING: The liquid elec­trolyte in these capacitors is
toxic. Avoid contact with any
portion of your body.

2. The control board may be faulty.
Replace.

WELDING PROBLEMS (Continued)

Service and repair should be performed by only Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in danger
to the technician or machine operator and will invalidate your factory warranty . For
your safety and to avoid electrical shock, please observe all safety notes and pre­cautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test / repairs safely, contact the Lincoln Electric Service Department for
electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.

POWER MIG 255

F-11 F-11

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WARNING

TROUBLESHOOTING & REPAIR

MAIN TRANSFORMER TEST

TEST DESCRIPTION

This procedure will determine if the correct voltages are being:
a. Applied to the primary windings of the main transformer.
b. Induced on the secondary and auxiliary windings of the main transformer.

MATERIALS NEEDED

Volt/Ohm Meter

3/8 in. Nutdriver
5/16 in. Nutdriver

POWER MIG 255

F-12 F-12

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TROUBLESHOOTING & REPAIR

4. Locate plug J5 and plug J6 on the
G3521 control PC board, and J9 on the
M19248 snubber PC board. See Figure
F.1.

NOTE: The location of plugs may vary

depending on the machine code.

5. Locate the following leads on plug J6
on the G3521 control PC board:

TEST PROCEDURE

The ON/OFF POWER SWITCH will be
“hot” during these tests.

----------------------------------------------------------

NOTE: Secondary voltages will vary pro­portionately with the primary input voltage.

1. Disconnect the main input power sup­ply to the machine.

2. Remove the case top and side panels
with a 3/8 in. nutdriver.

3. Remove the tool tray with a 5/16 in. nut­driver.

FIGURE F.1 — G3521 CONTROL PC BOARD AND M19248 SNUBBER PC BOARD

MAIN TRANSFORMER TEST POINTS.

J6

J5

J3

J8
J1

J4

J2

J9

X8

(16J5)

X9

(8J5)

#206
(3J5)

#208S

(2J9)

#209S

(6J9)

X7

(4J6)

X6

(5J6)

X5

(6J6)

MAIN TRANSFORMER TEST (continued)

WARNING

PLUG

LOCATION

6J6
5J6
4J6

LEAD

X5
X6
X7

POWER MIG 255

F-13 F-13

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TROUBLESHOOTING & REPAIR

11.Turn the machine ON.

12. Make the following voltage tests at plug
J5.

a. Turn the machine OFF between

each test.

b. Carefully insert the meter probes

into the back of each Molex plug
pin cavity to perform the test.

c. If the voltage tested is incorrect,

check for loose or broken leads
between the test points and the
main transformer.

d. If the voltage is not corrected, go to

step 16.

13. Turn OFF the machine power.

6. Connect main input power to the
machine.

7. Turn the POWER MIG 255 ON/OFF
POWER SWITCH to ON.

8. Carefully make the following voltage
tests at plug J6.

a. Turn the machine OFF between

each test.

b. Carefully insert the meter probes

into the back of each Molex plug
pin cavity to perform the test.

9. Turn OFF the machine.

10. Locate the following leads on plug J5
on the G3521 control PC board. See

Figure F.1.

MAIN TRANSFORMER TEST (continued)

FROM

LEAD

X5

(6J6)

X5

(6J6)

X6

(5J6)

TO

LEAD

X6

(5J6)

X7

(4J6)

X7

(4J6)

EXPECTED

VOLTAGE

15VAC

30VAC

15VAC

PLUG

LOCATION

16J5

8J5

LEAD

X8
X9

FROM

LEAD

X8

(16J5)

TO

LEAD

X9

(8J5)

EXPECTED

VOLTAGE

115VAC

POWER MIG 255

TROUBLESHOOTING AND REPAIR

F-14 F-14

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c. If any of the voltages tested are

incorrect, check for loose or broken
leads between the test points and
the main transformer.

d. If ALL the voltages tested are incor-

rect or missing, go to step 16.

17. Test for correct nameplate input
voltage between the H1 lead at the
ON/OFF POWER SWITCH to H2 or
H3 (H5 if connected for 575 VAC) at
the reconnect panel. Voltage tested will
vary depending on input voltage
connection. See wiring diagram for test
point locations.

a. If the voltage test is incorrect,

-check for loose or broken leads
between the reconnect panel and
the ON/OFF POWER SWITCH.

-test the ON/OFF POWER
SWITCH for proper operation.

b. If the correct nameplate voltage is

being applied to the main trans­former and one or more of the sec­ondary voltages are missing or are
incorrect, the main transformer may
be faulty. Replace.

14. Locate the following leads on plug J9
on the M19248 snubber PC board and
on plug J5 on the G3521 control PC
board. See Figure F.1.
G3521:

M19248:

15. Turn the machine ON.

16. Make the following voltage tests at plug
J9 on the M19248 snubber PC board
and at plug J5 on the G3521 control PC
board.

a. Turn the machine OFF between

each test.

b. Carefully insert the meter probes

into the back of each Molex plug
pin cavity to perform the test.

MAIN TRANSFORMER TEST (continued)

PLUG

LOCATION

3J5

LEAD

206

PLUG

LOCATION

2J9
6J9

LEAD

208S
209S

FROM

LEAD

208S

(2J9 on

M19248)

208S

(2J9 on

M19248)

209S

(6J9 on

M19248)

TO

LEAD

209S

(6J9 on

M19248)

206
(3J5 on
G3521)

206
(3J5 on
G3521)

EXPECTED

VOLTAGE

56VAC

28VAC

28VAC

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-15 F-15

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RECTIFIER DIODE BRIDGE TEST

Service and repair should only be performed by Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in dan­ger to the technician or machine operator and will invalidate your factory war­ranty. For your safety and to avoid electrical shock, please observe all safety
notes and precautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test/repairs safely, contact the Lincoln Electric service department for
technical troubleshooting assistance before you proceed. Call 1-888-935-3877.

-------------------------------------------------------------------------------------------------------------------

TEST DESCRIPTION

This test will determine if the correct voltages are being:
a. Applied to the diode bridge.
b. Supplied from diode bridge to the control PC board.

MATERIALS NEEDED

3/8 in. Nutdriver
Volt-ohmmeter
POWER MIG 255 wiring diagrams (See Electrical Diagrams Section of this Manual)

WARNING

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-16 F-16

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Leads #208R, #209R, and #354 are
connected to the rectifier diode bridge
(D2). See Figure F.2. Lead #206 is
connected at the output shunt. See the
wiring diagram.

5. Connect main input power to the
machine.

TEST PROCEDURE

1. Disconnect the main AC input power to
the machine.

2. Remove the case top and side panels
with a 3/8 in. nutdriver.

3. Perform the Main Transformer Test to
ensure the proper voltages are supplied
to the M19248 snubber PC board.

4. Locate the following leads:

RECTIFIER DIODE BRIDGE TESTING (continued)

LEAD

208R
209R

354
206

FIGURE F.2 — G3521 RECTIFIER DIODE BRIDGE LOCATION.

RECTIFIER

DIODE BRIDGE

(D2)

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-17 F-17

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9. Make the following voltage test:
a. Turn the machine OFF between

each test.

b. Carefully connect the meter probes

to the exposed lead connections.

c. Turn the machine ON to conduct

the voltage test.

10. If the DC voltage tested is incorrect or
missing, and the AC voltages are cor­rect, the rectifier diode bridge may be
faulty.

6. Turn the POWER MIG 255 ON/OFF
POWER SWITCH to ON.

7. Carefully make the following voltage
tests:

a. Turn the machine OFF between

each test.

b. Carefully connect the meter plugs

to the exposed lead connections.

c. Turn the machine ON to conduct

the voltage test.

8. If any of the AC voltages tested are
incorrect or missing, check the M19248
snubber PC board and associated
leads and connections. See the wiring
diagram.

RECTIFIER DIODE BRIDGE TESTING (continued)

FROM

LEAD

208R
209R

TO

LEAD

206
206

EXPECTED

VOLTAGE

28 VAC
28 VAC

FROM

LEAD

354

TO

LEAD

206

EXPECTED

VOLTAGE

36 VDC

POWER MIG 255

NOTES

F-18 F-18

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POWER MIG 255

TROUBLESHOOTING & REPAIR

F-19 F-19

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STATIC SCR RECTIFIER ASSEMBLY TEST

Service and repair should only be performed by Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in dan­ger to the technician or machine operator and will invalidate your factory war­ranty. For your safety and to avoid electrical shock, please observe all safety
notes and precautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test/repairs safely, contact the Lincoln Electric service department for
technical troubleshooting assistance before you proceed. Call 1-888-935-3877.

-------------------------------------------------------------------------------------------------------------------

TEST DESCRIPTION

This test is used to quickly determine if an SCR or diode is shorted or “leaky.” See the
Machine Waveform Section in this manual for normal and abnormal output waveforms.

MATERIALS NEEDED

Analog Volt-ohmmeter
POWER MIG 255 wiring diagrams (See Electrical Diagrams Section of this Manual)
3/8 in. Nutdriver
5/16 in. Nutdriver
1/2 in. Open end or socket wrench

WARNING

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-20 F-20

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4. Verify that the capacitors have
completely discharged with a volt­ohmmeter.

5. Disconnect plugs J6 from the G3521
control board and J9 from the M19248
snubber PC board. This electrically
isolates the SCR bridge assembly.
See Figure F.3.

TEST PROCEDURE

1. Disconnect main AC input power to the
machine.

2. Remove the case top and side panels
with a 3/8 in. nutdriver.

3. Remove the tool tray with a 5/16 in. nut­driver.

STATIC SCR RECTIFIER ASSEMBLY TEST (continued)

FIGURE F.3 — REMOVE PLUGS J6 AND J9 TO PERFORM STATIC RECTIFIER ASSEMBLY TEST.

J6

J5

J3

J8
J1

J4

J2

J9

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-21 F-21

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FIGURE F.5 — SCR 1 TEST POINTS.

9. Test for high or infinite resistance from
the cathode to the anode of SCR 1 by
reversing the meter leads. See Figure
F.5.

a. If a high or infinite resistance is indi-

cated for both tests 6 and 7, the
SCR 1 is not “shorted”.

b. If a low resistance is indicated in

either tests 6 or 7, the SCR is faulty .
Replace the SCR assembly.

10. Repeat steps 6 and 7 to test SCR 2.

11. Reconnect leads X2 and X3 (braided
copper strap).

12. Reconnect plugs J9 and J6.

13. If this test did not identify the problem,
or to further test the SCR, go to the
Active SCR Rectifier Assembly Test.

FIGURE F.4 — LOCATION OF

LEADS X2 AND X3.

6. Disconnect leads X2 and X3 (braided
copper strap) from the negative capaci­tor bank buss bar using a 1/2 in. open
end wrench. See Figure F.4.

7. Separate leads X2 and X3 from the
negative capacitor bank buss bar. Be
sure there is no electrical contact.

NOTE: DO NOT DISASSEMBLE THE SCR

RECTIFIER HEAT SINK ASSEMBLY.

8. Test for high or infinite resistance from
the anode to the cathode of SCR 1
using an analog ohmmeter. See Figure
F.5.

NEGATIVE

CAPACITOR

BANK BUSS

BAR

LEADS X2 AND X3

CONNECTION

STATIC SCR RECTIFIER ASSEMBLY TEST (continued)

POWER MIG 255

NOTES

F-22 F-22

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POWER MIG 255

TROUBLESHOOTING & REPAIR

F-23 F-23

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ACTIVE SCR RECTIFIER ASSEMBLY TEST

Service and repair should only be performed by Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in dan­ger to the technician or machine operator and will invalidate your factory war­ranty. For your safety and to avoid electrical shock, please observe all safety
notes and precautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test/repairs safely, contact the Lincoln Electric service department for
technical troubleshooting assistance before you proceed. Call 1-888-935-3877.

-------------------------------------------------------------------------------------------------------------------

TEST DESCRIPTION

The Active SCR Rectifier Assembly Test will determine if the device is able to be gated
ON and conduct current from anode to cathode.

The Static SCR Rectifier Assembly Test must be performed before proceeding with the
Active SCR Test.

MATERIALS NEEDED

3/8 in. Nutdriver
5/16 in. Nutdriver
An SCR Tester as specified in this procedure
POWER MIG 255 wiring diagrams (See Electrical Diagrams Section of this Manual)
SCR Heat Sink Assembly Drawings
A volt-ohmmeter

WARNING

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-24 F-24

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4. Verify that the capacitors have
completely discharged with a volt­ohmmeter.

5. Disconnect plugs J6 from the G3521
control board and J9 from the M19248
snubber PC board. This electrically
isolates the SCR bridge assembly.
See Figure F.6.

TEST PROCEDURE

1. Disconnect main AC input power to the
machine.

2. Remove the case top and side panels
with a 3/8 in. nutdriver.

3. Remove the tool tray with a 5/16 in. nut­driver.

ACTIVE SCR RECTIFIER ASSEMBLY TEST (continued)

FIGURE F.6 — CONTROL BOARD MOLEX PLUG LOCATIONS FOR G3521 PC CONTROL BOARD.

J6

J5

J3

J8
J1

J4

J2

J9

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-25 F-25

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8. Use a commercial SCR tester or con­struct the tester circuit shown in Figure
F.8. One 6-volt lantern battery can be
used. R1 and R2 resistor values are
±10%. Set voltmeter scale low, at
approximately 0-5 volts or 5-10 volts.

a. Test the voltage level of the battery.

Short leads (A) and (C). Close
switch SW-1. Battery voltage
should be 4.5 volts or higher. If
lower, replace the battery.

FIGURE F.8 — SCR TESTER CIRCUIT

AND SCR CONNECTIONS.

6. Disconnect leads X2 and X3 (braided
copper strap) from the negative capaci­tor bank buss bar using a 1/2 in. open
end wrench. See Figure F.7.

FIGURE F.7 — LOCATION OF

LEADS X2 AND X3.

7. Separate leads X2 and X3 from the
negative capacitor bank buss bar. Be
sure there is no electrical contact.

NOTE: DO NOT DISASSEMBLE THE SCR
RECTIFIER HEAT SINK ASSEMBLY.

ACTIVE SCR RECTIFIER ASSEMBLY TEST (continued)

NEGATIVE

CAPACITOR

BANK BUSS

BAR

LEADS X2 AND X3

CONNECTION

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-26 F-26

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15. Reconnect the tester leads. See Figure
F.8.

a. Connect tester lead (A) to the

cathode.

b. Connect tester lead (C) to the

anode.

c. Disconnect test lead (G) from the

gate.

16. Close switch SW-1.

17. Read meter for zero voltage.

a. If the voltage is zero, the SCR is

functioning.

b. If the voltage is higher than zero,

the SCR is shorted.

18. Perform the Active Test Procedure out­lined in Steps 6-15 for SCR 2.

19. Replace all SCR assemblies that do not
pass the above tests.

20. Reconnect plug J6 onto the control PC
board and J9 to the snubber PC board.

21. Reconnect leads X2 and X3 to the neg­ative capacitor bank bus bar.

22. Replace the tool tray and case sides.

9. Connect the tester to the SCR 1 as
shown in Figure F.8.

a. Connect tester lead (A) to the

anode.

b. Connect tester lead (C) to the

cathode.

c. Connect tester lead (G) to the gate.

10. Close switch SW-1.
NOTE: Switch SW-2 should be open.

11. Read meter for zero voltage.
a. If the voltage reading is higher than

zero, the SCR is shorted.

12. Close or keep closed switch SW-1.

13. Close switch SW-2 for 2 seconds and
release and read meter.

a. If the voltage is 3 to 6 volts while

the switch is closed and after the
switch is open, the SCR is
functioning.

b. If the voltage is 3 to 6 volts only

when the switch is closed or there
is no voltage when the switch is
closed, the SCR is defective.

NOTE: Be sure battery is functioning prop­erly. A low battery can affect the results of
the test. Repeat Battery Test Procedure in
Step 6 if needed.

14. Open switch SW-1.

ACTIVE SCR RECTIFIER ASSEMBLY TEST (continued)

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-27 F-27

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WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST

Service and repair should only be performed by Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in dan­ger to the technician or machine operator and will invalidate your factory war­ranty. For your safety and to avoid electrical shock, please observe all safety
notes and precautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test/repairs safely, contact the Lincoln Electric service department for
technical troubleshooting assistance before you proceed. Call 1-888-935-3877.

-------------------------------------------------------------------------------------------------------------------

TEST DESCRIPTION

This test will determine if the wire drive motor and voltage feedback circuit are func­tioning properly.

MATERIALS NEEDED

5/16 in. Nutdriver
Volt-Ohmmeter

WARNING

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-28 F-28

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3. Locate plug J1 on the G3521 control
PC board. See Figure F.9.

4. Locate the following leads on plug J1:

5. Connect the main power to the
machine.

TEST PROCEDURE

NOTE: POLARITY MUST BE OBSERVED

FOR THESE TESTS.
Test for Correct Wire Drive Motor Armature

Voltage

1. Disconnect main input power to the
machine.

2. Open the side panels and remove the
tool tray using a 5/16 in. nutdriver.

FIGURE F.9 — PLUG J1 LOCATION ON G3521 PC CONTROL BOARD.

J6

J5

J3

J8
J1

J4

J2

#555
(6J1)

W

(2J1)

#206B

(1J1)

#515B

(5J1)

B

(4J1)

WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST (continued)

PLUG

LOCATION

4J1
2J1

LEAD

B

W

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-29 F-29

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2. Locate plug J1 on the G3521 control
PC board. See Figure F.9.

3. Locate the following leads on Plug J1:

4. Connect main input power to the
machine.

5. Make the following voltage tests:

a. Turn the machine OFF between

each test.

b. Carefully insert the meter probes

into the back of each Molex plug
pin cavity.

6. If the 15 VDC is present, check the
leads to the tachometer circuit.

7. If the leads are okay and 15 VDC is
present, the correct voltage is being
received from the control PC board,
continue with the Supply Voltage to
Tachometer Test.

8. If the 15 VDC is not present and the
leads are okay, the control PC board
may be faulty, replace the control PC
board.

6. Make the following voltage tests:
a. Turn the machine OFF between

each test.

b. Carefully insert the meter probes

into the back of each Molex plug
pin cavity to perform the test.

c. Turn the machine ON and pull the

gun trigger to conduct the voltage
test.

7. If the voltage to the wire drive motor

armature is zero, check the wires
between plug J1 and the wire drive
motor. Also check the electrical connec­tor J12 for proper connection and con­tact.

8. If all wires and connectors are good and

the voltage to the drive motor armature
is zero, the G3521 control PC board
may be faulty, replace the control PC
board.

9. If the motor is running at high speed

and the armature voltage is high and
uncontrollable, proceed with the
tachometer test.

TEST FOR SUPPLY VOLTAGE
TO TACHOMETER

1. Disconnect the main AC input power to

the machine.

WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST (continued)

FROM

LEAD

B

(4J1)

TO

LEAD

W

(2J1)

EXPECTED

VOLTAGE

3-20 VDC

(varies depend-

ing on wire feed

speed)

FROM

LEAD

515B
(5J1)

TO

LEAD

206B
(1J1)

EXPECTED

VOLTAGE

15 VDC

PLUG

LOCATION

5J1
1J1

LEAD

515B
206B

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-30 F-30

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c. Turn the machine ON and pull the

gun trigger to conduct the voltage
test.

6. If the 1.5 to 3.5 VDC is present, the
tachometer circuit is sending the cor­rect feedback signal to the Control PC
Board.

7. If the 1.5 to 3.5 VDC is not present or
not correct, the Control PC Board is
not receiving the proper feedback
voltage from the tachometer circuit.
Check the leads from the tachometer
circuit to the control PC board for loose
or broken connections.

8. If the leads are okay, the tachometer
circuit may be faulty, replace the
tachometer circuit.

9. Replace the tool tray.

TEST FOR FEEDBACK VOLTAGE
TO CONTROL BOARD

1. Disconnect the main AC input power to
the machine.

2. Locate plug J1 on the G3521 control
PC board.

3. Locate the following leads on plug J1
(see Figure F.9):

4. Connect main input power to the
machine.

5. Make the following voltage tests:

a. Turn the machine OFF between

each test.

b. Carefully insert the meter probes

into the back of each Molex plug
pin cavity.

WIRE DRIVE MOTOR AND TACHOMETER FEEDBACK TEST (continued)

PLUG

LOCATION

6J1
1J1

LEAD

555

206B

FROM

LEAD

555

(6J1)

TO

LEAD

206B
(1J1)

EXPECTED

VOLTAGE

1.5 to 3.5 VDC

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-31 F-31

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0 VOLTS

20.0 V 2.5 ms

This is a typical DC output voltage waveform
generated from a properly operating
machine. Note that each vertical division
represents 20 volts and that each horizontal
division represents 2.5 milliseconds in time.

NOTE: Scope probes connected at
machine output terminals: (+) probe to elec­trode, (-) probe to work.

Volts/Div . . . . . . . . . . . . . . . . . . 20 V/Div

Horizontal Sweep . . . . . . . . . 2.5 ms/Div

Coupling . . . . . . . . . . . . . . . . . . . . . . DC

Trigger . . . . . . . . . . . . . . . . . . . . Internal

SCOPE SETTINGS

NORMAL OPEN CIRCUIT VOLTAGE WAVEFORM

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-32 F-32

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0 VOLTS

20.0 V 5 ms

MACHINE LOADED TO 250 AMPS AT 26 VDC

TYPICAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED

This is a typical DC output voltage waveform
generated from a properly operating
machine. Note that each vertical division
represents 20 volts and that each horizontal
division represents 5 milliseconds in time.
The machine was loaded with a resistance
grid bank.

NOTE: Scope probes connected at machine
output terminals: (+) probe to electrode, (-)
probe to work.

Volts/Div . . . . . . . . . . . . . . . . . . 20 V/Div

Horizontal Sweep . . . . . . . . . . 5 ms/Div

Coupling . . . . . . . . . . . . . . . . . . . . . . DC

Trigger . . . . . . . . . . . . . . . . . . . . Internal

SCOPE SETTINGS

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-33 F-33

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0 VOLTS

20.0 V 5 ms

MACHINE LOADED TO 220 AMPS AT 22 VDC

ABNORMAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED
ONE OUTPUT SCR NOT FUNCTIONING

This is NOT a typical DC output voltage
waveform. One output SCR is not function­ing. Note the increased ripple content. One
SCR gate was disconnected to simulate an
open or non-functioning output SCR. Each
vertical division represents 20 volts and
each horizontal division represents 5 mil­liseconds in time. The machine was loaded
with a resistance grid bank.

NOTE: Scope probes connected at machine
output terminals: (+) probe to electrode, (-)
probe to work.

Volts/Div . . . . . . . . . . . . . . . . . . 20 V/Div

Horizontal Sweep . . . . . . . . . . 5 ms/Div

Coupling . . . . . . . . . . . . . . . . . . . . . . DC

Trigger . . . . . . . . . . . . . . . . . . . . Internal

SCOPE SETTINGS

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-34 F-34

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0 VOLTS

20.0 V 5 ms

ABNORMAL OPEN CIRCUIT VOLTAGE
OUTPUT CAPACITOR BANK NOT FUNCTIONING

This is NOT the typical DC output voltage
waveform. The output capacitors are not
functioning. Note the lack of “filtering” in the
output waveform. The output capacitor bank
was disconnected. Each vertical division
represents 20 volts and each horizontal divi­sion represents 5 milliseconds in time.

NOTE: Scope probes connected at machine
output terminals: (+) probe to electrode, (-)
probe to work.

Volts/Div . . . . . . . . . . . . . . . . . . 20 V/Div

Horizontal Sweep . . . . . . . . . . 5 ms/Div

Coupling . . . . . . . . . . . . . . . . . . . . . . DC

Trigger . . . . . . . . . . . . . . . . . . . . Internal

SCOPE SETTINGS

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-35 F-35

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0 VOLTS

2.00 V 5 ms

TYPICAL SCR GATE VOLTAGE WAVEFORM

This is a typical SCR gate pulse voltage
waveform. The machine was in an open
circuit condition (no load) and operating
properly. Note that each vertical division
represents 2 volts and each horizontal
division represents 5 milliseconds in time.

NOTE: Scope probes connected at Plug J6
on the control board. The (+) probe to lead
G2, and the (-) probe to lead 204.

Volts/Div . . . . . . . . . . . . . . . . . . 2.0 V/Div

Horizontal Sweep . . . . . . . . . . 5 ms/Div

Coupling . . . . . . . . . . . . . . . . . . . . . . DC

Trigger . . . . . . . . . . . . . . . . . . . . Internal

SCOPE SETTINGS

POWER MIG 255

NOTES

F-36 F-36

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POWER MIG 255

F-37 F-37

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Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC

TROUBLESHOOTING AND REPAIR

Service and repair should be performed by only Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in danger
to the technician or machine operator and will invalidate your factory warranty . For
your safety and to avoid electrical shock, please observe all safety notes and pre­cautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test / repairs safely, contact the Lincoln Electric Service Department for
electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.

WARNING

CONTROL PC BOARD

REMOVAL AND REPLACEMENT PROCEDURE

DESCRIPTION

This procedure will aid the technician in the removal and replacement of the Control PC
Board.

MATERIALS NEEDED

5/16 in. Nutdriver
Static electricity grounding strap

Printed Circuit Boards can be damaged by static electricity. Follow static handling
guidelines detailed in “PC Board Troubleshooting Procedures” at the beginning of this
chapter.

------------------------------------------------------------------------------------------------------------------

CAUTION

POWER MIG 255

F-38 F-38

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TROUBLESHOOTING AND REPAIR

CONTROL PC BOARD

REMOVAL AND REPLACEMENT PROCEDURE (Continued)

REMOVAL AND REPLACEMENT
PROCEDURE

1. Disconnect main input power the
machine.

2. Open the side panels and remove the
tool tray using a 5/16 in. nutdriver.

3. Disconnect all wiring harness plugs and
Molex plugs connected to the control
board. See Figure F.10.

FIGURE F.10 — WIRING HARNESS

AND MOLEX PLUG LOCATIONS.

J1

J2

J3

J4

J5

J6

J8

POWER MIG 255

F-39 F-39

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TROUBLESHOOTING AND REPAIR

CONTROL PC BOARD

REMOVAL AND REPLACEMENT PROCEDURE (Continued)

7. When re-installing the control PC board
carefully secure board to mounting
standoffs.

8. Install all plug connectors previously
removed from the control PC board.

9. Install the tool tray and close the side
panels.

4. Ensure a static electricity grounding
strap is used before handling the con­trol PC boards.

5. Carefully remove the control PC board
from the mounting standoffs.

6. Lift the control PC board straight up and
out from the machine.

FIGURE F.11 — CONTROL BOARD MOUNTING.

PC CONTROL

BOARD

TOOL
TRAY

NOTE: TOP COVER SHOWN

REMOVED FOR CLARITY.

MOUNTING
STANDOFF

POWER MIG 255

NOTES

F-40 F-40

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POWER MIG 255

TROUBLESHOOTING & REPAIR

F-41 F-41

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Service and repair should be performed by only Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in danger
to the technician or machine operator and will invalidate your factory warranty . For
your safety and to avoid electrical shock, please observe all safety notes and pre­cautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test / repairs safely, contact the Lincoln Electric Service Department for
electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.

WARNING

WIRE DRIVE ASSEMBLY

REMOVAL AND REPLACEMENT PROCEDURE

DESCRIPTION

This procedure will aid the technician in the removal and replacement of the Wire Drive
Assembly.

MATERIALS NEEDED

Large slot head screwdriver
5/16 in. Nutdriver
Small slot head screwdriver
3/4 in. Open end wrench
7/16 in. Nutdriver

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-42 F-42

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6. Disconnect the wire connectors J13
and J12 to the motor/gearbox assem­bly. See Wiring Diagram.

7. Use a 3/4 in. wrench and remove the
flange nut and positive lead from the
wire drive assembly. See Figure F.12.

8. Use pliers to remove the hose clamp
and flex hose from the wire drive
assembly.

9. Remove the outer guide assembly from
the wire drive assembly by loosening
the thumb screws until the outer guide
can be removed.

PROCEDURE

1. Disconnect main input power to the
machine.

2. Remove the wire gun and wire.

3. Lift the wire drive door to gain access to
the wire drive assembly.

4. Lift the tool tray door to allow access to
the tool tray.

5. Use a 5/16 in. nutdriver and remove the
tool tray to gain access to the
motor/gearbox assembly.

FIGURE F.12 — WIRE DRIVE ASSEMBLY REMOVAL FOR CODES 10563 & 10583 REFER TO P344-F.2

FOR EXPLODED VIEW OF WIRE DRIVE FOR CODES 10986 AND 10990 - SIMILAR PROCEDURE

4

3

7

8

14

13

12

11

2

17

18

19

9

10

1

5

6

16

15

WIRE DRIVE ASSEMBLY REMOVAL AND REPLACEMENT (continued)

1. Wire Drive Assembly

2. Motor/Gearbox Assembly

3. Flange Nut

4. Positive Lead

5. Hose Clamp

6. Flex Hose

7. Outer Guide Assembly

8. Thumb Screw

9. Adjustment Arm Assembly

10. Idle Arm

11. Round Head Screw

12. Lock Washer

13. Flat Washer

14. Molded Drive Roll Shaft
Assembly

15. Pan Head Screw

16. Lock Washer

17. Hex Head Cap Screw

18. Lock Washer

19. Flat Washer

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-43 F-43

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15. Grasp the motor/gearbox assembly and
wiggle the motor/gearbox assembly
gently back and forth until it separates
from the wire drive assembly.

16. Use a 7/16 in. nutdriver to remove the
hex head cap screws, lock washers,
and flat washers securing the wire
drive assembly to the wire drive
compartment.

17. Remove the wire drive assembly from
the wire drive compartment.

18. Reassemble the wire drive assembly in
the reverse order.

10. Rotate the adjustment arm assembly
counterclockwise to release the tension
on the idle arm.

11. Swing the idle arm up and away from
the wire drive assembly.

12. Use a screwdriver and remove the
round head screw, lock washer, and flat
washer securing the molded drive roll
shaft assembly to the wire drive assem­bly.

13. Remove the molded drive roll shaft
assembly and the rest of the outer
guide assembly from the wire drive
assembly.

14. Use a screwdriver and remove the pan
head screws and lock washers secur­ing the motor/gearbox assembly to the
wire drive assembly.

WIRE DRIVE ASSEMBLY REMOVAL AND REPLACEMENT (continued)

POWER MIG 255

NOTES

F-44 F-44

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POWER MIG 255

TROUBLESHOOTING & REPAIR

F-45 F-45

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Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC

Service and repair should be performed by only Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in danger
to the technician or machine operator and will invalidate your factory warranty . For
your safety and to avoid electrical shock, please observe all safety notes and pre­cautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test / repairs safely, contact the Lincoln Electric Service Department for
electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.

WARNING

SCR OUTPUT RECTIFIER

REMOVAL AND REPLACEMENT PROCEDURE

DESCRIPTION

This procedure will aid the technician in the removal and replacement of the SCR
Assembly.

MATERIALS NEEDED

1/2 in. Open end wrench
1/2 in. Socket wrench, universal tool, and extension
3/8 in. Nutdriver
3/8 in. Open end wrench

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-46 F-46

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3. Disconnect lead #204 and heavy alu­minum choke lead from the middle heat
sink with a 1/2 in. socket wrench and
1/2 in. open end wrench. See Figure
F.14.

4. Remove the diode lead from the nega­tive capacitor band buss bar on the
right side of the machine using a 1/2 in.
socket and 3/8 in. open end wrench.

FIGURE F.14 — MIDDLE HEAT SINK

LEAD DISCONNECTION.

PROCEDURE

1. Remove the case side panels using a
3/8 in. nutdriver.

2. Disconnect lead #208S and trans­former lead X1 from the heat sink on
the left side of the machine using a 1/2
in. socket wrench. See Figure F.13.

a. Thin lead is always on the outboard

side of the connection.

FIGURE F.13 — LEFT HEAT SINK

LEAD DISCONNECTION.

SCR OUTPUT RECTIFIER REMOVAL AND REPLACEMENT (continued)

LEAD X1

LEAD

#208S

LEFT

HEAT SINK

HEAVY

LEAD

LEAD

#204S

MIDDLE

HEAT SINK

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-47 F-47

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8. Clear the leads and carefully remove
the SCR rectifier assembly.

NOTE: When installing the SCR rectifier
assembly, apply a thin coating of Dow
Corning #340 compound to the electrical
connections.

9. Unplug leads 320 and 320B from the
SCR heat sink thermostat on the right
side at the SCR assembly.

10. Reassemble the SCR assembly in the
reverse order.

5. Remove lead #209S and transformer
lead X4 from the right side heat sink
using a 1/2 in. socket wrench and
1/2 in. open end wrench. See Figure
F.15.

6. Unplug the SCR gate leads G1 and G2
(see wire markers and wiring diagram).

7. Remove the four nuts holding the SCR
assembly to the floor of the machine
using a 3/8 in. nutdriver.

FIGURE F.15 — RIGHT HEAT SINK LEAD DISCONNECTION.

LEAD

X4

LEAD

#209S

LEAD

#320B

LEAD

#320

SCR DIODE

LEAD

SCR

ASSEMBLY

SCR OUTPUT RECTIFIER REMOVAL AND REPLACEMENT (continued)

POWER MIG 255

NOTES

F-48 F-48

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POWER MIG 255

TROUBLESHOOTING & REPAIR

F-49 F-49

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The liquid electrolite in the capacitors is toxic. Do not touch the capacitors with
any part of your body.

-------------------------------------------------------------------------------------------------------------------

WARNING

Service and repair should be performed by only Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in danger
to the technician or machine operator and will invalidate your factory warranty . For
your safety and to avoid electrical shock, please observe all safety notes and pre­cautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test / repairs safely, contact the Lincoln Electric Service Department for
electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.

WARNING

CAPACITOR BANK

REMOVAL AND REPLACEMENT PROCEDURE

DESCRIPTION

This procedure will aid the technician in the removal and replacement of the Capacitor
Bank.

MATERIALS NEEDED

5/16 in. Nutdriver
3/8 in. Nutdriver
1/2 in. Open end wrench
3/8 in. Open end wrench
Wiring diagram

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-50 F-50

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tive capacitor bank buss bar using a
1/2 in. open end wrench.

6. Remove the choke lead and lead 204B
from the positive capacitor bank buss
bar using two 1/2 in. open end wrench­es.

7. Remove the power factor enhancement
choke lead from the positive capacitor
buss bar using two 1/2 in. open end
wrenches.

8. Remove the three nuts holding the
capacitor bank to the floor of the
machine using a 3/8 in. nut driver.

9. Clear the leads and carefully remove
the capacitor bank assembly from the
machine.

10. Reassemble the capacitor bank in the
reverse order.

PROCEDURE

See Figure F.16 for location of capacitor
bank removal and replacement components.

1. Disconnect main input power to the
machine.

2. Remove the case side panels using a
3/8 in. nutdriver.

3. Test that the capacitors are discharged
using a volt ohmmeter. Polarity must
be observed.

4. Remove the two transformer secondary
leads X2 and X3 (braided copper strap)
from the negative capacitor bank buss
bar using two 1/2 in. open end wrench­es.

5. Remove the shunt, leads 206, 206B,
and the SCR diode lead from the nega-

FIGURE F.16 — LOCATION OF CAPACITOR BANK REMOVAL AND REPLACEMENT COMPONENTS.

SCR DIODE

LEAD

LEAD

#206B

LEAD

#206

SHUNT

CAPACITOR

BANK

OUTPUT

CHOKE LEAD

POWER

ENHANCEMENT

CHOKE LEAD

LEADS

X1 AND X2

CAPACITOR BANK REMOVAL AND REPLACEMENT (continued)

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-51 F-51

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Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC

Service and repair should be performed by only Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in danger
to the technician or machine operator and will invalidate your factory warranty . For
your safety and to avoid electrical shock, please observe all safety notes and pre­cautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test / repairs safely, contact the Lincoln Electric Service Department for
electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.

WARNING

MAIN TRANSFORMER AND OUTPUT CHOKE

REMOVAL AND REPLACEMENT PROCEDURE

DESCRIPTION

This procedure will aid the technician in the removal and replacement of the Main
Transformer and Choke Assembly.

MATERIALS NEEDED

5/16 in. Nut Driver
1/2 in. Open end wrench
3/8 in. Open end wrench
1/2 in. Socket wrench, extender, universal adapter
Wire cutters
Phillips head screwdriver

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-52 F-52

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6. Remove the two transformer secondary
leads X2 and X3 (braided copper strap)
from the negative capacitor bank buss
bar using two 1/2 in. open end wrench­es.

7. Disconnect and label all transformer
leads from the reconnect panel using a
3/8 in. open end wrench.

8. Disconnect and label all leads from the
input power switch.

9. Remove the power switch.

10. Disconnect thermostat leads #320 and
#320B from the SCR Rectifier.

PROCEDURE

1. Disconnect main input power to the
machine.

2. Remove the case side panels using a
3/8 in. nutdriver.

3. Test that the capacitors are discharged
using a volt ohmmeter. Polarity must
be observed.

4. Remove lead X1 from the left side SCR
heat sink assembly using a 1/2 in. sock­et wrench, extender and universal
adapter. See Figure F.17.

5. Remove lead X4 from the right side
heat sink assembly using a 1/2 in. sock­et wrench, extender and universal
adapter.

FIGURE F.17 — MAIN TRANSFORMER REMOVAL.

OUTPUT

CHOKE

LEAD

LEAD

X1

LEAD

X4

LEADS

X2 AND X3

POWER

ENHANCEMENT

CHOKE

MAIN

TRANSFORMER

PLUG-IN LEADS ARE
NOT SHOWN FOR
CLARITY.

NOTE:

OUTPUT

CHOKE

POSITIVE

LEAD

MAIN TRANSFORMER AND OUTPUT CHOKE

REMOVAL AND REPLACEMENT (continued)

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-53 F-53

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11. Unplug and label leads X5, X6, X7, X8, and X9.
These leads have connectors near the trans­former which can be disconnected.

12. Disconnect the output choke lead from the posi­tive capacitor bank buss using two 1/2 in. open
end wrenches.

13. Remove the other output choke lead from the
positive output terminal using a 1/2 in. wrench.

13. Remove all cable ties, wire mounts, and any har­ness type that could get in the way during trans­former removal using wire cutters and screw
driver.

14. Remove the four nuts and washers mounting the
transformer to the floor of the machine using a
1/2 in. wrench.

15. Carefully remove the main transformer and choke
assembly.

16. Reassemble the main transformer and choke
assembly in the reverse order.

MAIN TRANSFORMER AND OUTPUT CHOKE

REMOVAL AND REPLACEMENT (continued)

POWER MIG 255

NOTES

F-54 F-54

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POWER MIG 255

TROUBLESHOOTING & REPAIR

F-55 F-55

Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC

Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC

Service and repair should be performed by only Lincoln Electric factory trained
personnel. Unauthorized repairs performed on this equipment may result in danger
to the technician or machine operator and will invalidate your factory warranty . For
your safety and to avoid electrical shock, please observe all safety notes and pre­cautions detailed throughout this manual.

If for any reason you do not understand the test procedures or are unable to per­form the test / repairs safely, contact the Lincoln Electric Service Department for
electrical troubleshooting assistance before you proceed. Call 1-888-935-3877.

WARNING

FAN MOTOR ASSEMBLY

REMOVAL AND REPLACEMENT PROCEDURE

DESCRIPTION

This procedure will aid the technician in the removal and replacement of the Fan Motor
Assembly.

MATERIALS NEEDED

3/8 in. Nutdriver
11/32 in. Open end wrench
Slot head screwdriver

POWER MIG 255

TROUBLESHOOTING & REPAIR

F-56 F-56

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a. Loosen and remove the two nuts

and lock washers from the motor
mounting bracket using a 11/32 in.
open end wrench.

b. When the motor is free from the

mounting bracket, slide the motor
from the POWER MIG unit.

5. Install the replacement motor in the
reverse order of removal.

6. Install the fan blade and tighten the fan
blade clamp. Ensure the fan is in the
same position on the shaft as it was
prior to removal.

a. Spin the fan to be sure it is free to

rotate.

7. Reassemble the remaining compo­nents in reverse order of removal.

PROCEDURE

1. Disconnect main input power to the
machine.

1. Remove the case side panels using a
3/8 in. nutdriver.

2. Disconnect the fan motor leads #352
and #352. See Figure F.18.

3. Remove the fan blade. Note the posi­tion of the fan on the shaft for reassem­bly.

a. Use a screwdriver to loosen the fan

blade clamp.

b. Slide the fan blade off the motor

shaft.

4. Remove the fan motor.

FIGURE F.18 — FAN MOTOR ASSEMBLY REMOVAL.

LEAD

#352

LEAD

#353

FAN

MOTOR

FAN

BLADE

FAN

BLADE

CLAMP

FAN MOTOR ASSEMBLY REMOVAL AND REPLACEMENT (continued)

POWER MIG 255

TROUBLESHOOTING AND REPAIR

F-57 F-57

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INPUT IDLE AMPS AND WATTS

WIRE SPEED RANGE

OPEN CIRCUIT VOLTAGE

RETEST AFTER REPAIR

Maximum Idle Watts

Maximum Idle Amps

Input Volts/Hertz

4007.0230/60

50 - 700 IPM (1.27 - 17.8 m/minute)

35-40 VDC

POWER MIG 255

NOTES

F-58 F-58

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POWER MIG 255

Section G-1 Section G-1

TABLE OF CONTENTS

- ELECTRICAL DIAGRAMS SECTION -

Electrical Diagrams ...............................................................................................Section G

Wiring Diagram - Entire Machine - Code 10563 - (L10979) . . . . . . . . . . . . . . . . . . . .G-2

Wiring Diagram - Entire Machine - Code 10583 - (L10980) . . . . . . . . . . . . . . . . . . . .G-3

Wiring Diagram - Entire Machine - Code 10986 - (L11980) . . . . . . . . . . . . . . . . . . . .G-4

Wiring Diagram - Entire Machine - Code 10990 - (L11979) . . . . . . . . . . . . . . . . . . . .G-5

Control PC Board Schematic (G3520-1D1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .G-6

Control PC Board Assembly (G3521-1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .G-7

Display PC Board Schematic (L10951) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .G-8

Display PC Board Assembly (L10952-1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .G-9

Snubber PC Board Schematic (S24374) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .G-10

Snubber PC Board Assembly (M19248-1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .G-11

G-2

ELECTRICAL DIAGRAMS

POWER MIG 255

WIRING DIAGRAM - ENTIRE MACHINE - CODE 10563 - (L10979)

392

325

515B

209S

**

204S

209R

209

209S

W

254

256

551

254A

552

COLOR CODE:

ELECTRICAL SYMBOLS PER E1537

GENERAL INFORMATION

POWER MIG 255 (208/230V)

206B

G2

4
5

J7

4
5
6

2

7
8

J11

GUN
TRIGGER

2

325

4

3
4

J12

325

324

H4

H1

9

6

8

7

7

5

4

L1

7

2

1

5

6

265
263

260

261

U - BLUE

R - RED

W - WHITE

B - BLACK

INDICATES CONNECTOR CAVITY NO.

10

3

3

1

2

1
2

253
252

262
267
264

J3

J8

1

J5

J6

1

TO GROUND PER

NATIONAL ELECTRICAL

CODE

OUTPUT

CHOKE

POWER FACTOR

ENHANCEMENT

CHOKE

POWER

TRANSFORMER

2-23-2001A

B

555

D1

204B

205

352
X9

325B

320

207

FOR SPOOL GUN OPTION

204S

208R

**

208R

P.M.

SECONDARY VOLTAGES SHOWN
ARE NO LOAD RMS VALUES

252

2
3
4

TO
WORK

5

6

MOTOR/

GEARBOX

7
8
9

10

11

14
15
16

6

H3

209
208
206

354

1
2
3

J2

4
5
6
7
8

10

11

12
13
14

2

6

1
2
3

10

CAVITY

WIRE FEED
SPEED

352

1

2

1

B

+

L2

208V

H1

LINE

SWITCH

S1

RECONNECT

PANEL

G

H2

C3C1

X4

205206S

206B

R1

8

1

6

8
9

10

11

12

OUTPUT CHOKE

THERMOSTAT

SCR HEATSINK

ASSEMBLY

THERMOSTAT

116.6V

14.2V

14.2V

28.4V

515B

B

324

206B

L2L1

208

208S

1

2

SCI
325A
543
326

SCI

204

GND

500

C2

+++

C1 THRU C3
31,000 MFD
50V

X7

G1

X6

204

X5

G2

X8

353

207

206S

15 OHMS
100 W

5

4

3

2

1

12
13

2
3

4

5

CONTROL BOARD

CONDUCTOR STRAP AND WORK STUD.

OFF AND REVERSE LEAD CONNECTIONS AT CABLE

"POSITIVE". TO CHANGE POLARITY, TURN THE UNIT

FUTURE APPLICATIONS.

8

7

6

5

4

3

B

-

W

555

354

D2
BAFFLE
MOUNTED
RECTIFIER
DIODE
BRIDGE

R.F.

CHOKE

AS’BLY

B

+

-

325B

541A

320B

320

253256

550

**

DISPLAY
BOARD

5

1

4

1

3

1

4

12

7

8

6

1 1

7

1

1

J10

209R

324

**

J10

GAS

SOLENOID

9

251

353

515B

390

555
206B

B

392

NOTES:

N.A. WELDING CABLE MUST BE OF PROPER CAPACITY FOR THE

CURRENT AND DUTY CYCLE OF IMMEDIATE AND

N.B. THIS DIAGRAM SHOWS THE "ELECTRODE" POLARITY

1

J1

J4

J6

J8

J9

J7

(NON-LEAD SIDE OF CONNECTOR)

2

J11

J12

J13

10

3

4

J2

J5

9

14

8

16

1

1

2

3

3

4

X8

X9

X5

X5

X6

R.F. FILTER

X6

X7

X7

X1

2

1

ARC
VOLTAGE

FAN

MOTOR

R3

GND

500

515

550

551

552

J3

CAVITY NUMBERING SEQUENCE

(COMPONENT SIDE OF P.C. BOARD)

2

10

6

8

5

6

NUMBERING SEQUENCE

X9

251254

R4

206

J1

J4

1

3
4

8

7

9

FOR TIMER

OPTION

515

390

206A

515

SCR 1

J13

SCR HEATSINK
ASBLY

SCR 2

X8

230V

TO SINGLE PHASE

SUPPLY LINE

H1

X2

X3

H2

28.4V

W

SNUBBER
BOARD

J9

W

H4H3

W

208S

G1

R

T
A
C
H

U

G-2

Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC

Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC

NOTE: This diagram is for reference only. It may not be accurate for all machines covered by this manual. The wiring diagram specific to your code is pasted inside one of the enclosure panels of your machine.

G-3

ELECTRICAL DIAGRAMS

POWER MIG 255

WIRING DIAGRAM - ENTIRE MACHINE - CODE 10583 - (L10980)

G-3

Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC

Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC

1

209

555

B

W

515

254

262

207

P.M.

208S

J9

B

T
A
C
H

D1

ASBLY

2-23-2001A

11

1

28.4V

14.2V

14.2V

116.6V

515
206A

SCI

541A

326

543

206B

353

GENERAL INFORMATION

CAVITY NUMBERING SEQUENCE

(COMPONENT SIDE OF P.C. BOARD)

1

2

1

J7

1

16

J5

9

TO
WORK

CAVITY

J13

WIRE FEED
SPEED

C1 THRU C3
31,000 MFD
50V

4

-

U

515B
555
206B

206

204S

3

2

SCR HEATSINK

ASSEMBLY

THERMOSTAT

8

7

6

5

4

3

204
G1
X7

325A

324

SCI

390

FOR SPOOL GUN OPTION

OUTPUT

CHOKE

+

X4

206B

G2

209S

H4

**

COLOR CODE:

H5

GUN
TRIGGER

POWER

TRANSFORMER

4

2

324

325

324

H3

J3

7

7

5

209R

320B

W

G1

3
4

1
2
3
4

7

CURRENT AND DUTY CYCLE OF IMMEDIATE AND
FUTURE APPLICATIONS.

5

3

-

N.B. THIS DIAGRAM SHOWS THE "ELECTRODE" POLARITY

SNUBBER
BOARD

D2
BAFFLE
MOUNTED
RECTIFIER
DIODE
BRIDGE

W

207

B

205

390

10

256

206S
205

352
X9

**

325B

DISPLAY
BOARD

X5

208R

209R

354

8

12

2

3

4

8

6

5

7

14
15
16

J12

1

2

209
208
206

354
325B
GND
320

353

252

2

1

4

2

3

13

12

10

6

5

1

2

208R

208

204S
209S

500

256

551

552

206B

251

555

X8

515B

G2

325

J11

1

1

2

3

X8

3

4

C3+C2C1

X2

X3

R4

INDICATES CONNECTOR CAVITY NO.

U - BLUE

R - RED

W - WHITE

B - BLACK

SECONDARY VOLTAGES SHOWN
ARE NO LOAD RMS VALUES

OUTPUT CHOKE

THERMOSTAT

++

B

206S

L1

H2

H5

5

R

H4

H1

4

2

1

3

H1

LINE

SWITCH

S1

RECONNECT

PANEL

(SHOWN CONNECTED

FOR 230V)

TO SINGLE PHASE

SUPPLY LINE

TO GROUND PER

NATIONAL ELECTRICAL

CODE

ARC
VOLTAGE

10

6

5

1

J4

4

3

14

8

252

253

5

4

2

FOR TIMER

OPTION

6

GAS

SOLENOID

4

3

2

1

261

263

204

L2

15 OHMS
100 W

R1

204B

+

208S

6

R.F. FILTER

SCR 2

254A

R3

FAN

MOTOR

392

254253

X6

X7

X7

X1

H1

H2

H1H3

H4

W

B

L2L1

**

1

6

8

9
10

J5

28.4V

J6

320

**

R.F.

CHOKE

AS’BLY

GND

4

9
10

11
12

13

1

2

3
4
5

J7

5

6

J8

515B

550

X6

NOTES:

N.A. WELDING CABLE MUST BE OF PROPER CAPACITY FOR THE

J1

2

108

(NON-LEAD SIDE OF CONNECTOR)

2

1

J10

1

7 11

J2

J4

6
7
8

3

9

1

10

5

7
8
9

260

264

267

265

14

11

J2

J1

9

8

1
2

CONTROL BOARD

6
7
8

X9

X9

X5

POWER FACTOR

ENHANCEMENT

CHOKE

251

325

1

J6

J8

J9

6

5

4

6

1

J3

NUMBERING SEQUENCE

12

7

J12

8

2

J11

J13

4

3

1

352

J10

POWER MIG 255 (230/460/575V)

515

500

551

550

552

ELECTRICAL SYMBOLS PER E1537

SCR 1

SCR HEATSINK

MOTOR/

GEARBOX

B

X6

X5

X8

CONDUCTOR STRAP AND WORK STUD.

OFF AND REVERSE LEAD CONNECTIONS AT CABLE

"POSITIVE". TO CHANGE POLARITY, TURN THE UNIT

392

W

NOTE: This diagram is for reference only. It may not be accurate for all machines covered by this manual. The wiring diagram specific to your code is pasted inside one of the enclosure panels of your machine.

G-4

ELECTRICAL DIAGRAMS

POWER MIG 255

G-4

Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC

Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC

WIRING DIAGRAM - ENTIRE MACHINE - CODE 10986 - (L11980)

NOTE: This diagram is for reference only. It may not be accurate for all machines covered by this manual. The wiring diagram specific to your code is pasted inside one of the enclosure panels of your machine.

POWER MIG 255 (230/460/575 V)

TO SINGLE PHASE
SUPPLY LINE

TO GROUND PER
NATIONAL ELECTRICAL
CODE

J8

1

J3

7

H2

H5

5

2

RECONNECT
PANEL
(SHOWN CONNECTED
FOR 230V)

CAVITY NUMBERING SEQUENCE

(COMPONENT SIDE OF P.C. BOARD)

1

4

3

6

J2

J1
J9

J12

1

8

10

GUN
TRIGGER

1

2

3

4

H1H3

1

5 8

324

325

J4
J7

6

1

7

J5

9

14

1

J11

J11

**

1

325

2

3

324

4

L2

L1

L2L1

H1

H1H4H1

H4H1H4

H4

LINE
SWITCH
S1

1

1

J6

4

2

6

12

J10

H4

4

1

3

W

B

G

253

253

253R4254256

ARC

ARC

ARC

ARC

ARC

ARC

ARC

ARC
VOLTAGE

VOLTAGE

VOLTAGE

VOLTAGE

VOLTAGE

VOLTAGE

VOLTAGE

VOLTAGE

B

W

WIRE
DRIVE
MOTOR/
GEARBOX

J10

DISPLAY

DISPLAY

DISPLAY

DISPLAY

DISPLAY
BOARD

BOARD

BOARD

BOARD

BOARD

352

FAN
MOTOR

265
263
262
267
264
260

261

204
208S
208
208R
204S
209S
209
209R

325B

TO

TO

TO
WORK

WORK

WORK

352

353

353

FOR TIMER
OPTION

J7

1
2
3

4
5
6
7
8
9

10

GND

3

2

3

3

2

3

352

5

5

5

5

8

427

847

8

7

4

8

7

4

8

7

4

6

6

6

6

1

1

1

1

1

R4

R4

R4

R4

R4

R4

6

550

551

515

552

500

500

515

551

552

550

500

515

550

551

552

5152551

552

550

500

500

515

550

551

552

254A

254A

254A

254A

254A

254A

254A

254A

254A

R3

R3

R3

R3

R3

R3

R3R4

R3

252

251

252254253256

252254253256

252254256

252254256

252

252254253256

252254253256

252254253256

SNUBBER
BOARD

J9

320

SCR HEATSINK
ASSEMBLY
THERMOSTAT

R.F. FILTER

R.F. FILTER

R.F. FILTER

390 392

GAS

SOLENOID

320B

OUTPUT CHOKE
THERMOSTAT

1
2
3

4
5
6
7
8

WIRE FEED

WIRE FEED

WIRE FEED

WIRE FEED

WIRE FEED

WIRE FEED

WIRE FEED

WIRE FEED
SPEED

SPEED

SPEED

SPEED

SPEED

SPEED

SPEED

SPEED

J12

1
2

R
U

B

B

W

515B

3

555

4

206B

5
6

B

7

W

8

207

207

CONTROL BOARD

CONTROL BOARD

253
252
251
552
551
256

550
254
500

515

206B
B

W
515B
555
325
324

390
392

SCI
325A
543
326

541A
SCI

515
206A

FOR SPOOL GUN OPTION

209
208
206
206S
205

352
X9
354
325B
GND
320
207

353
X8

G2
204
G1
X7
X6
X5

1

2
3
4

5

6
7
8

9
10
11
12
13
14

1

2

3

4
5
6
7
8
9

10

1

2

3

4
5
6
7
8

1

2

1

2

3

4

5
6
7
8
9

10
11
12

1

2

3

4

5

6

7

8

9

10
11
12
13
14
15
16

1

2

3

4

5
6

J2

J4

J1

J8

J3

J3

J5

J6

GENERAL INFORMATION

ELECTRICAL SYMBOLS PER E1537

COLOR CODE:

B - BLACK
W - WHITE

X8

116.6V

X9

X5

14.2V

X6

14.2V

X7
X1

28.4V

X2

28.4V

X4

R - RED
U - BLUE

CAVITY

**

2

1

J11

3

4

D2
BAFFLE
MOUNTED

C3C1

C1 THRU C3

+++

31,000 MFD
50V

204S

204S

204S

204S

204S

204S

RECTIFIER
DIODE
BRIDGE

D1

X8

X9
X5

X6

X7

X3

C2

5

10

8

16

H1

INDICATES CONNECTOR CAVITY NO.

NUMBERING SEQUENCE

(NON-LEAD SIDE OF CONNECTOR)

SECONDARY VOLTAGES SHOWN
ARE NO LOAD RMS VALUES

H1

H2
H5

H3

H4

POWER

POWER

POWER
TRANSFORMER

TRANSFORMER

TRANSFORMER

POWER FACTOR
ENHANCEMENT
CHOKE

NOTES:

N.A. WELDING CABLE MUST BE OF PROPER CAPACITY FOR THE

CURRENT AND DUTY CYCLE OF IMMEDIATE AND
FUTURE APPLICATIONS.

N.B. THIS DIAGRAM SHOWS THE "ELECTRODE" POLARITY

"POSITIVE". TO CHANGE POLARITY, TURN THE UNIT
OFF AND REVERSE LEAD CONNECTIONS AT CABLE
CONDUCTOR STRAP AND WORK STUD.

208R

208R

208R

208R

209R

209R

209R

209R

354

354

354

-

-

-

-

-

+

+

+

+

+

208S

208S

208S

208S

208S

208S

G1

G1

G1

G1

G1

G1

SCR 1

SCR 1

SCR 1

SCR 1

SCR 1

SCR HEATSINK

SCR HEATSINK

SCR HEATSINK

SCR HEATSINK

SCR HEATSINK

SCR HEATSINK
ASBLY

ASBLY

ASBLY

ASBLY

ASBLY

ASBLY

SCR 2

SCR 2

SCR 2

SCR 2

SCR 2

SCR 2

G2

G2

G2

G2

G2

G2

209S

209S

209S

209S

209S

209S

205206S

+

-

206B

15 OHMS

1
R

100 W

204B

OUTPUT
CHOKE

256

256 253 254

R
U

B

206

T
A
C
H

A

L11980