ESAB 251cv User manual

INSTRUCTION MANUAL
F-15-358
July, 1998
251cv
POWER SOURCE
These INSTRUCTIONS are for experienced operators. If you are not fully familiar with the principles of
operation and safe practices for arc welding equipment, we urge you to read our booklet, "Precautions
and Safe Practices for Arc Welding, Cutting and Gouging." Form 52-529. Do NOT permit untrained
persons to install, operate, or maintain this equipment. Do NOT attempt to install or operate this
equipment until you have read and fully understand these Instructions. If you do not fully understand
these Instructions, contact your supplier for further information.
Be sure this information reaches the operator.
You can get extra copies through your supplier.
This manual provides complete instructions for the following packages starting with Serial No. MORI80800 :
36696 - 25 cv, 200/230/460 Vac 60 Hz
36697 - 25 cv, 230/460/575 Vac 60 Hz
36698 - 25 cv, 220/400 (380/4 5) Vac 50 Hz
251cv shown with optional
Meter Kit and MT-250SG
Spool-On-Gun Torch

2
USER RESPONSIBILITY
This equipment will perform in conformity with the description thereof contained in this manual and accompanying labels and/or inserts
when installed, operated, maintained and repaired in accordance with the instructions provided. This equipment must be checked
periodically. Malfunctioning equipment should not be used. Parts that are broken, missing, worn, distorted or contaminated should be
replaced immediately. Should such repair or replacement become necessary, the manufacturer recommends that a telephone or written
request for service advice be made to the uthorized Distributor from whom purchased.
This equipment or any of its parts should not be altered without the prior written approval of the manufacturer. The user of this equipment
shall have the sole responsibility for any malfunction which results from improper use, faulty maintenance, damage, improper repair
or alteration by anyone other than the manufacturer or a service facility designated by the manufacturer.
SECTION 1 DESCRIPTION..................................................... 7
1.1 General................................................................. 7
1.2 Receiving-Handling .............................................. 7
1.3 Description ........................................................... 7
1.3.1 251cv Power Source............................................ 7
1.3.2 Optional Controls ................................................. 7
1.4 Optional Accessories ........................................... 7
1.4.1 MT-250SG Spool-on-Gun .................................... 7
1.4.2 ST-23A Spool-On-Gun Torch and Adaptor Kit .... 7
1.4.3 TR-24 and TR-251cv Trucks ............................... 7
1.4.4 Torch/Wire Feed Accessories ............................. 7
1.5 Safety ................................................................... 7
1.6 Duty Cycle and Curves ........................................ 7
1.7 Volt/Ampere Curves ............................................. 8
SECTION 2 INSTALLATION................................................... 9
2.1 Location................................................................ 9
2.1.1 Lifting Eyebolt....................................................... 9
2.2 Electrical Input Connections ................................ 9
2.2.1 Input Electrical Requirements.............................. 9
2.2.2 Input Conductor Connections ............................ 10
2.3 Output Welding Connections ............................. 10
2.4 Control Connections .......................................... 10
2.4.1 Wire Feeder Control........................................... 10
2.4.2 42V Circuit Breaker ............................................ 10
2.4.3 24V Circuit Breaker ............................................ 10
SECTION NO
PARAGRAPH TITLE PAGE NO.
TABLE OF CONTENTS
SECTION NO
PARAGRAPH TITLE PAGE NO.
SECTION 3 OPERATION ...................................................... 11
3.1 Controls .............................................................. 11
3.1.1 Power Switch (ON-OFF) .................................... 11
3.1.2 Contactor Control ............................................... 11
3.1.3 Voltage Panel/Remote Switch ........................... 11
3.1.4 Voltage Control .................................................. 11
3.1.3 Feeder Selector Switch ...................................... 11
3.2 Operating Procedures ........................................ 12
3.2.1 Operating Safety Precautions ............................ 12
3.2.2 Pre-Weld Requirements..................................... 12
3.2.3 Set-Up Procedure .............................................. 13
3.2.4 Welding Operation ............................................. 13
SECTION 4 MAINTENANCE................................................. 15
4.1 General............................................................... 15
4.2 Inspection and Service....................................... 15
4.3 Power Source..................................................... 15
4.3.1 Fan Motor ........................................................... 15
4.3.2 Transformer........................................................ 15
4.3.3 Over Temperature Protection ............................ 15
SECTION 5 TROUBLESHOOTING....................................... 16
5.1 General............................................................... 16
SECTION 6 PARTS ............................................................... 21
6.1 General............................................................... 21
6.2 Ordering ............................................................. 21

3
WARNING: These Safety Precautions are for
your protection. They summarize precaution-
ary information from the references listed in
Additional Safety Information section. Before
performing any installation or operating procedures, be
sure to read and follow the safety precautions listed below
as well as all other manuals, material safety data sheets,
labels,etc.FailuretoobserveSafetyPrecautionscanresult
in injury or death.
PROTECT YOURSELF AND OTHERS --
Some welding, cutting, and gouging
processes are noisy and require ear
protection. The arc, like the sun, emits
ultraviolet(UV) andother radiationand
can injure skin and eyes. Hot metal can cause burns.
Training in the proper use of the processes and equip-
ment is essential to prevent accidents. Therefore:
1. Alwayswear safetyglasseswithside shieldsinanywork
area, even if welding helmets, face shields, and goggles
are also required.
2. Use a face shield fitted with the correct filter and cover
plates to protect your eyes, face, neck, and ears from
sparks and rays of the arc when operating or observing
operations. Warn bystanders not to watch the arc and
not to expose themselves to the rays of the electric-arc
or hot metal.
3. Wearflameproofgauntlettypegloves,heavylong-sleeve
shirt, cuffless trousers, high-topped shoes, and a weld-
ing helmet or cap for hair protection, to protect against
arcrays and hot sparks orhot metal. Aflameproof apron
may also be desirable as protection against radiated
heat and sparks.
4. Hot sparks or metal can lodge in rolled up sleeves,
trouser cuffs, or pockets. Sleeves and collars should be
kept buttoned, and open pockets eliminated from the
front of clothing
5. Protect other personnel from arc rays and hot sparks
with a suitable non-flammable partition or curtains.
6. Use goggles over safety glasses when chipping slag or
grinding. Chipped slag may be hot and can fly far.
Bystandersshouldalsoweargogglesoversafetyglasses.
FIRES AND EXPLOSIONS -- Heat from
flamesand arcs can startfires.Hot slag
or sparks can also cause fires and ex-
plosions. Therefore:
1. Remove all combustible materials well away from the
work area or cover the materials with a protective non-
flammablecovering.Combustiblematerialsincludewood,
cloth,sawdust, liquid andgas fuels, solvents, paints and
coatings, paper, etc.
2. Hot sparks or hot metal can fall through cracks or
crevices in floors or wall openings and cause a hidden
smoldering fire or fires on the floor below. Make certain
that such openings are protected from hot sparks and
metal.“
3. Do not weld, cut or perform other hot work until the
workpiece has been completely cleaned so that there
are no substances on the workpiece which might pro-
duce flammable or toxic vapors. Do not do hot work on
closed containers. They may explode.
4. Havefireextinguishing equipmenthandyforinstantuse,
such as a garden hose, water pail, sand bucket, or
portable fire extinguisher. Be sure you are trained in its
use.
SAFETY PRECAUTIONS
11/95
5. Do not use equipment beyond its ratings. For example,
overloaded welding cable can overheat and create a fire
hazard.
6. After completing operations, inspect the work area to
make certain there are no hot sparks or hot metal which
could cause a later fire. Use fire watchers when neces-
sary.
7. For additional information, refer to NFPA Standard 51B,
"Fire Prevention in Use of Cutting and Welding Pro-
cesses",availablefromthe National Fire ProtectionAsso-
ciation, Batterymarch Park, Quincy, MA 02269.
ELECTRICALSHOCK--Contactwithlive
electrical parts and ground can cause
severe injury or death. DO NOT use AC
welding current in damp areas, if move-
ment is confined, or if there is danger of
falling.
1. Be sure the power source frame (chassis) is connected
to the ground system of the input power.
2. Connect the workpiece to a good electrical ground.
3. Connect the work cable to the workpiece. A poor or
missing connection can expose you or others to a fatal
shock.
4. Use well-maintained equipment. Replace worn or dam-
aged cables.
5. Keepeverythingdry,includingclothing,workarea,cables,
torch/electrode holder, and power source.
6. Make sure that all parts of your body are insulated from
work and from ground.
7. Do not stand directly on metal or the earth while working
in tight quarters or a damp area; stand on dry boards or
an insulating platform and wear rubber-soled shoes.
8. Putondry,hole-freeglovesbeforeturning on the power.
9. Turn off the power before removing your gloves.
10. RefertoANSI/ASC StandardZ49.1(listedonnextpage)
forspecificgroundingrecommendations.Donotmistake
the work lead for a ground cable.
ELECTRIC AND MAGNETIC FIELDS —
Maybedangerous.Electriccurrentflow-
ing through any conductor causes lo-
calized Electric and Magnetic Fields
(EMF). Welding and cutting current cre-
ates EMF around welding cables and
welding machines. Therefore:
1. Welders having pacemakers should consult their physi-
cian before welding. EMF may interfere with some pace-
makers.
2. ExposuretoEMFmay have other health effectswhichare
unknown.
3. Welders should use the following procedures to minimize
exposure to EMF:
A. Route the electrode and work cables together. Secure
them with tape when possible.
B. Never coil the torch or work cable around your body.
C. Do not place your body between the torch and work
cables. Route cables on the same side of your body.
D. Connect the work cable to the workpiece as close as
possible to the area being welded.
E. Keep welding power source and cables as far away
from your body as possible.

4
FUMES AND GASES -- Fumes and
gases,cancausediscomfortorharm,
particularly in confined spaces. Do
notbreathefumesandgases.Shield-
ing gases can cause asphyxiation.
Therefore:
1. Always provide adequate ventilation in the work area by
naturalormechanicalmeans.Do not weld, cut, orgouge
on materials such as galvanized steel, stainless steel,
copper,zinc,lead,beryllium,orcadmiumunlesspositive
mechanicalventilationisprovided.Donotbreathefumes
from these materials.
2. Do not operate near degreasing and spraying opera-
tions. The heat or arc rays can react with chlorinated
hydrocarbon vapors to form phosgene, a highly toxic
gas, and other irritant gases.
3. If you develop momentary eye, nose, or throat irritation
whileoperating,thisisanindicationthatventilationisnot
adequate. Stop work and take necessary steps to im-
prove ventilation in the work area. Do not continue to
operate if physical discomfort persists.
4. Refer to ANSI/ASC Standard Z49.1 (see listing below)
for specific ventilation recommendations.
CYLINDER HANDLING -- Cylinders, if
mishandled, can rupture and violently
release gas. Sudden rupture of cylin-
der,valve,orreliefdevicecaninjureor
kill. Therefore:
1. Use the proper gas for the process and use the proper
pressure reducing regulator designed to operate from
the compressed gas cylinder. Do not use adaptors.
Maintain hoses and fittings in good condition. Follow
manufacturer'soperatinginstructionsformountingregu-
lator to a compressed gas cylinder.
2. Always secure cylinders in an upright position by chain
orstraptosuitablehandtrucks,undercarriages,benches,
walls, post, or racks. Never secure cylinders to work
tables or fixtures where they may become part of an
electrical circuit.
3. When not in use, keep cylinder valves closed. Have
valve protection cap in place if regulator is not con-
nected. Secure and move cylinders by using suitable
hand trucks. Avoid rough handling of cylinders.
4. Locate cylinders away from heat, sparks, and flames.
Never strike an arc on a cylinder.
5. For additional information, refer to CGA Standard P-1,
"PrecautionsforSafe HandlingofCompressedGasesin
Cylinders", which is available from Compressed Gas
Association, 1235 Jefferson Davis Highway, Arlington,
VA 22202.
EQUIPMENTMAINTENANCE--Faultyorim-
properly maintained equipment can cause
injury or death. Therefore:
1. Always have qualified personnel perform the installa-
tion, troubleshooting, and maintenance work. Do not
perform any electrical work unless you are qualified to
perform such work.
2. Before performing any maintenance work inside a power
source, disconnect the power source from the incoming
electrical power.
3. Maintaincables,groundingwire,connections,powercord,
and power supply in safe working order. Do not operate
any equipment in faulty condition.
4. Do not abuse any equipment or accessories. Keep
equipment away from heat sources such as furnaces, wet
conditions such as water puddles, oil or grease, corrosive
atmospheres and inclement weather.
5. Keepall safety devices andcabinet covers in positionand
in good repair.
6. Use equipment only for its intended purpose. Do not
modify it in any manner.
ADDITIONAL SAFETY INFORMATION -- For
more information on safe practices for elec-
tric arc welding and cutting equipment, ask
your supplier for a copy of "Precautions and
Safe Practices for Arc Welding, Cutting and
Gouging", Form 52-529.
The following publications, which are available from the
American Welding Society, 550 N.W. LeJuene Road, Miami,
FL 33126, are recommended to you:
1. ANSI/ASC Z49.1 - "Safety in Welding and Cutting"
2. AWS C5.1 - "Recommended Practices for Plasma Arc
Welding"
3. AWS C5.2 - "Recommended Practices for Plasma Arc
Cutting"
4. AWS C5.3 - "Recommended Practices for Air Carbon Arc
Gouging and Cutting"
5. AWS C5.5 - "Recommended Practices for Gas Tungsten
Arc Welding“
6. AWS C5.6 - "Recommended Practices for Gas Metal Arc
Welding"“
7. AWS SP - "Safe Practices" - Reprint, Welding Handbook.
8. ANSI/AWSF4.1,"RecommendedSafePracticesforWeld-
ing and Cutting of Containers That Have Held Hazardous
Substances."
Thissymbolappearingthroughoutthismanual
means Attention! Be Alert! Your safety is
involved.
The following definitions apply to DANGER, WARNING,
CAUTION found throughout this manual:
Used to call attention to immediate haz-
ards which, if not avoided, will result in
immediate,seriouspersonalinjuryorloss
of life.
Used to call attention to potential haz-
ardswhichcouldresultinpersonalinjury
or loss of life.
Used to call attention to hazards which
could result in minor personal injury.

5
a. Éloigner suffisamment tous les matériaux combus-
tibles du secteur où l’on exécute des soudures ou des
coupes à l’arc, à moins de les recouvrir complètement
d’une bâche non-inflammable. Ce type de matériaux
comprend notamment le bois, les vêtements, la sciure,
l’essence, le kérosène, les peintures, les solvants, le
gaz naturel, l’acétylène, le propane et autres sub-
stances combustibles semblables.
b. Les étincelles ou les projections de métal incandes-
cent peuvent tomber dans des fissures du plancher ou
dans des ouvertures des murs et y déclencher une
ignition lente cachée. Veiller à protéger ces ouvertures
des étincelles et des projections de métal.
c. N’exécutez pas de soudures, de coupes, d’opérations
de gougeage ou autres travaux à chaud à la surface
de barils, bidons, réservoirs ou autres contenants
usagés, avant de les avoir nettoyés de toute trace de
substance susceptible de produire des vapeurs
inflammables ou toxiques.
d. En vue d’assurer la prévention des incendies, il
convient de disposer d’un matériel d’extinction prêt à
servir immédiatement, tel qu’un tuyau d’arrosage, un
seau à eau, un seau de sable ou un extincteur portatif.
e. Une fois le travail à l’arc terminé, inspectez le secteur
de façon à vous assurer qu’aucune étincelle ou projec-
tion de métal incandescent ne risque de provoquer
ultérieurement un feu.
3. CHOC ÉLECTRIQUE-- Le gougeage à l’arc et à l’arc
au plasma exige l’emploi de tensions à vide
relativement importantes; or, celles-ci risquent de
causer des dommages corporels graves et même
mortels en cas d’utilisation inadéquate. La gravité du
choc électrique reçu dépend du chemin suivi par le
courant à travers le corps humain et de son intensité.
a. Ne laissez jamais de surfaces métalliques sous ten-
sion venir au contact direct de la peau ou de
vêtements humides. Veillez à porter des gants bien
secs.
b. Si vous devez effectuer un travail sur une surface
métallique ou dans un secteur humide, veillez à assu-
rer votre isolation corporelle en portant des gants secs
et des chaussures à semelles de caoutchouc et en
vous tenant sur une planche ou une plate-forme
sèche.
c. Mettez toujours à la terre le poste de soudage/coupage
en le reliant par un câble à une bonne prise de terre.
d. N’utilisez jamais de câbles usés ou endommagés. Ne
surchargez jamais le câble. Utilisez toujours un
équipement correctement entretenu.
e. Mettez l’équipement hors tension lorsqu’il n’est pas en
service. une mise à la masse accidentelle peut en
effet provoquer une surchauffe de l’équipement et un
danger d’incendie. Ne pas enrouler ou passer le câble
autour d’une partie quelconque du corps.
f. Vérifiez si le câble de masse est bien relié à la pièce en
un point aussi proche que possible de la zone de
travail. Le branchement des câbles de masse à
l’ossature du bâtiment ou en un point éloigné de la
zone de travail augmente en effet le risque de pas-
sage d’un courant de sortie par des chaînes delevage
PRÉCAUTIONS DE SÉCURITÉ
AVERTISSEMENT: Ces règles de sécurité ont pour objet
d’ assurer votre protection. Veillez à lire et à observer les
précautions énoncées ci-dessous avant de monter l’
équipement ou de commercer à l’utiliser. Tout défaut
d’observation de ces précautions risque d’entraîner des
blessures graves ou mortelles.
1. PROTECTION INDIVIDUELLE-- Les brûlures de la
peau et des yeux dues au rayonnement de l’arc
électrique ou du métal incandescent, lors du soudage
au plasma ou à l’électrode ou lors du gougeage à
l’arc, peuvent s’avérer plus graves que celles
résultant d’une exposition prolongée au soleil. Aussi
convient-il d’observer les précautions suivantes:
a. Portez un écran facial adéquat muni des plaques
protectrices et des verres filtrants appropriés afin de
vous protéger les yeux, le visage, le cou et les oreilles
des étincelles et du rayonnement de l’arc électrique
lorsque vous effectuez des soudures ou des coupes
ou lorsque vous en observez l’exécution.
AVERTISSEZ les personnes se trouvant à proximité
de façon à ce qu’elles ne regardent pas l’arc et à ce
qu’elles ne s’exposent pas à son rayonnement, ni à
celui du métal incandescent.
b. Portez des gants ignifugés à crispins, une tunique
épaisse à manches longues, des pantalons sans
rebord, des chaussures à embout d’acier et un
casque de soudage ou une calotte de protection, afin
d’éviter d’exposer la peau au rayonnement de l’arc
électrique ou du métal incandescent. ll est également
souhaitable d’utiliser un tablier ininflammable de
façon à se protéger des étincelles et du rayonnement
thermique.
c. Les étincelles ou les projections de métal incandes-
cent risquent de se loger dans des manches
retroussées, des bords relevés de pantalons ou dans
des poches. Aussi convient-il de garder boutonnés le
col et les manches et de porter des vêtements sans
poches à l’avant.
d. Protégez des étincelles et du rayonnement de l’arc
électrique les autres personnes travaillant à proximité
à l’aide d’un écran ininflammable adéquat.
e. Ne jamais omettre de porter des lunettes de sécurité
lorsque vous vous trouvez dans un secteur où l’on
effectue des opérations de soudage ou de coupage à
l’arc. Utilisez des lunettes de sécurité à écrans ou
verres latéraux pour piquer ou meûler le laitier. Les
piquetures incandescentes de laitier peuvent être
projetées à des distances considérables. Les
personnes se trouvant à proximité doivent également
porter des lunettes de protection.
f. Le gougeage à l’arc et le soudage à l’arc au plasma
produisent un niveau de bruit extrêmement élevé (de
100 à 114 dB) et exigent par conséquent l’emploi de
dispositifs appropriés de protection auditive.
2. PRÉVENTION DES INCENDES-- Les projections de
laitier incandescent ou d’étincelles peuvent
provoquer de graves incendies au contact de
matériaux combustibles solides, liquides ou gazeux.
Aussi faut-il observer les précautions suivantes:
9/97

6
des câbles de grue ou divers chemins électriques.
g. Empêchez l’apparition de toute humidité, notamment
sur vos vêtements, à la surface de l’emplacement de
travail, des câbles, du porte-électrode et du poste de
soudage/coupage. Réparez immédiatement toute
fuite d’eau.
4. VENTILATION-- La respiration prolongée des fumées
résultant des opérations de soudage/coupage, à
l’intérieur, d’un local clos, peut provoquer des mal-
aises et des dommages corporels. Aussi convient-il
d’observer les précautions suivantes:
a. Assurez en permanence une aération adéquate de
l’emplacement de travail en maintenant une ventila-
tion naturelle ou à l’aide de moyens mécaniques.
N’effectuez jamais de travaux de soudage ou de
coupage sur des matériaux de zinc, de plomb, de
beryllium ou de cadmium en l’absence de moyens
mécaniques de ventilation capables d’empêcher
l’inhalation des fumées dégagées par ces matériaux.
b. N’effectuez jamais de travaux de soudage ou de
coupage à proximité de vapeurs d’hydrocarbure
chloré résultant d’opérations voisines de dégraissage
ou de pulvérisation. La chaleur dégagée ou le
rayonnement de l’arc peut déclencher la formation de
phosgène -- gaz particulièrement toxique -- et d’autres
gaz irritants, à partir des vapeurs de solvant.
c. Une irritation momentanée des yeux, du nez ou de la
gorge constatée au cours de l’utilisation de
l’équipement dénote un défaut de ventilation. Arrêtez-
vous de travailler afin de prendre les mesures néces-
saires à l’amélioration de la ventilation. Ne poursuivez
pas l’opération entreprise si le malaise persiste.
d. Certaines commandes comportent des canalisations
où circule de l’hydrogène. L’armoire de commande est
munie d’un ventilateur destiné à empêcher la forma-
tion de poches d’hydrogène, lesquelles présentent un
danger d’explosion; ce ventilateur ne fonctionne que
si l’interrupteur correspondant du panneau avant se
trouve placé en position ON (Marche). Veillez à
manœuvrer cette commande en vérifiant si le
couvercle est bien en place, de façon à assurer
l’efficacité de la ventilation ainsi réalisée. Ne jamais
débrancher le ventilateur.
e. Les fumées produites par l’opération de soudage ou
de coupage peuvent s’avérer toxiques. Aussi est-il
nécessaire de disposer en permanence d’un dispositif
adéquat de ventilation de type aspirant, afin d’élimi-
ner du voisinage de l’opérateur tout dégagement de
fumée visible.
f. Consultez les recommandations particulières en
matière de ventilation indiquées à l’alinéa 6 de la
norme Z49.1 de l’AWS.
5. ENTRETIEN DE L’ÉQUIPEMENT-- Un équipement
entretenu de façon défectueuse ou inadéquate risque
non seulement de réaliser un travail de mauvaise
qualité mais, chose plus grave encore, d’entraîner
des dommages corporels graves, voire mortels en
déclenchant des incendies ou des chocs électriques.
Observez par conséquent les précautions suivantes:
a. Efforcez-vous de toujours confier à un personnel qua-
lifié l’installation, le dépannage et l’entretien du poste
de soudage et de coupage. N’effectuez aucune
réparation électrique sur l’équipement à moins d’être
qua-lifié à cet effet.
b. Ne procédez jamais à une tâche d’entretien
quelconque à l’intérieur du poste de soudage/
coupage, avant d’avoir débranché l’alimentation
électrique.
c. Maintenez en bon état de fonctionnement les câbles,
le câble de masse, les branchements, le cordon
d’alimentation et le poste de soudage/coupage.
N’utilisez jamais le poste ou l’équipement s’il présente
une défectuosité quelconque.
d. Prenez soin du poste de soudage et de coupage et
des équipements accessoires. Gardez-les à l’écart
des sources de charleur, notamment des fours, de
l’humidité, des flaques d’eau maintenez-les à l’abri des
traces d’huile ou de graisse, des atmosphères corro-
sives et des intempéries.
e. Laissez en place tous les dispositifs de sécurité et tous
les panneaux de l’armoire de commande en veillant à
les garder en bon état.
f. Utilisez le poste de soudage/coupage conformément à
son usage prévu et n’effectuez aucune modification.
6. INFORMATIONS COMPLÉMENTAIRES RELATIVES
À LA SÉCURITÉ--
Pour obtenir des informations complémentaires sur les
règles de sécurité à observer pour le montage et
l’utilisation d’équipements de soudage et de coupage
électriques et sur les méthodes de travail
recommandées, demandez un exemplaire du livret N°
52529 “Precautions and Safe Practices for Arc Weld-
ing, Cutting and Gouging” publié par ESAB. Nous
conseillons également de consulter les publications
sui-vantes, tenues à votre disposition par l’American
Welding Society, 550 N.W. LeJuene Road, Miami, FL
32126:
a. “Safety in Welding and Cutting” AWS Z49.1
b. “Recommended Safe Practices for Gas-Shielded Arc
Welding “AWS A6. 1.
c. “Safe Practices for Welding and Cutting Containers
That Have Held Combustibles” AWS-A6.0.
d. “Recommended Safe Practices for Plasma Arc Cut-
ting” AWS-A6. 3.
e. “Recommended Safe Practices for Plasma Arc Weld-
ing” AWS-C5. 1.
f. “Recommended Safe Practices for Air Carbon Arc
Gouging and Cutting” AWS-C5. 3.
g. “Code For Safety in Welding and Cutting”
CSA-Standard W117. 2.
9/97

7
SECTION 1 DESCRIPTION
gun torch designed for the mig welding process. It is
completely portable (up to 30-ft.), air-cooled and hand
operated, and weighs less than three (3) pounds which
allows for great maneuverability and operator conve-
nience. The gun is equipped with three thirty (30) foot
service lines; control cable with amphenol plug, power
cable with twist-lock connector, gas hose for direct
connection to gas cylinder.
1.4.2 ST-23A SPOOL-ON-GUN TORCH, P/N 19164;
ADAPTOR KIT ST-23A TO 251cv P/N 37301
TheST-23A Spool-On-Gun torch can also be used with
the251cvbuttheadaptorkit,P/N37301,willberequired.
The adaptor is equipped with a gas hose for hooking up
to a flowmeter.
1.4.3 TR-24 SINGLE CYLINDER TRUCK KIT, P/N
37300 or TR-251cv DUAL CYLINDER TRUCK
KIT, P/N 36700
Provides complete mobility for power source. Each kit
includes handle, 4 castors, and 1 or 2 gas cylinder
brackets.
1.4.4 METER KIT, P/N 36699
LCDmeterhasvolt/ampselectorswitchtodisplayactual
welding voltage or current. Mounts easily to the front
control panels of 251cv power source.
1.5 SAFETY
Before the equipment is put into operation, the safety
section at the front of this manual should be read com-
pletely.Thiswillhelpavoidpossibleinjuryduetomisuse
or improper welding applications.
The symbol which precedes safety notes appear-
ingthroughoutthismanualmeans“Attention!BeAlert!
Yoursafetyisinvolved.”Thedefinitionsrelatingtothe
DANGER, WARNING and CAUTION safety notations
aredescribedattheendoftheSafetySectioninthefront
of this manual -- read them and their specific text refer-
ences carefully.
1.6 DUTY CYCLE AND CURVES (Figure 1.1)
Thedutycycleoftheequipmentisthepercentageofa10
minute period which it can operate at a given output
currentwithoutoverheating.The251cvPowerSourceis
ratedat 40% dutycycle.This means thattheequipment
can be operated at 250 amperes for four minutes out of
every 10. This cycle can be repeated indefinitely (See
Figure 1.1).
1.1 GENERAL
This manual has been prepared especially for use in
familiarizing personnel with the design, installation, op-
eration,maintenance,andtroubleshootingofthisequip-
ment. All information presented here in should be given
carefulconsiderationtoassureoptimumperformanceof
this equipment.
1.2 RECEIVING-HANDLING
Priortoinstallingthisequipment,cleanallpackingmate-
rial from around the unit and carefully inspect for any
damage that may have occurred during shipment. Any
claims for loss or damage that may have occurred in
transit must be filed by the purchaser with the carrier. A
copy of the bill of lading and freight bill will be furnished
by the carrier on request if occasion to file claim arises.
When requesting information concerning this equip-
ment,itisessentialthatPart,SerialandModelNumbers
of the equipment be supplied.
1.3 DESCRIPTION
The 251cv Power Source has been designed for fine
wire, (0.023, 0.030, 0.035 and 0.045 in.) welding using
theshortarcmethod,aswell asfor sprayarcaluminum,
short arc and spray arc stainless steel and spray arc
coredwires.Italso hasa built-incontrolforoperatingan
optionalspool-on-gunandhasprovisionsforanoptional
undercarriagewithsinglecylinderrackoradualcylinder
rack.
1.3.1 251cv POWER SOURCE
The power source consists of a single phase trans-
former, single phase full wave controlled rectifier, stabi-
lizing reactor, filtering capacitors and internal output
connections for polarity reversal. See front cover for list
of available 251cv power sources.
1.3.2 OPTIONAL CONTROLS
The251cv can be usedtoweld hard and aluminumwire
with an optional MT-250SG spool-on-gun torch. The
optional spool-on-gun adaptors and control, when used
inconjunctionwiththeoptionalMT-250SGtorch,permits
aluminum wire welding with the machine.
1.4 OPTIONAL ACCESSORIES
1.4.1MT-250SGSPOOL-ON-GUNTORCH,P/N36779
The 251CV unit is equipped with a control for the MT-
250SG Spool-On-Gun welding torch. This is a high
performance, 250 ampere continuous duty spool-on-

8
SECTION 1 DESCRIPTION
TABLE 1-1. SPECIFICATIONS
POWER SOURCE 251cv
Rated Output 250 Amps @ 30 Volts d.c.
Duty Cycle, 40%
Primary Input, Volts AC 200/230/460;230/460/575;220/400(380/415)
Primary Input, Amperes 52/58/31;58/31/25;59/34(36/32)
Output Current Range 30 to 300 Amps.
Maximum Open Circuit Volts 36 v.d.c.
PHYSICAL
Net Weight 138 lbs (63 Kg.)
Height 20.9 inches (530 mm)
Width 12.9 inches (330 mm)
Depth 26.1 inches (660 mm)
Fig. 1.1 Duty Cycle Curves Figure 1.2 Volt/Ampere Curves
% DUTY CYCLE
WELDING AMPERES
20 25 30 35 40 50 60 70 80 90 100
300
250
200
150
RATED OUTPUT
VOLTS
AMPS
1.7 VOLT/AMPERE CURVES (Figure 1.2)
The Volt/A pere curves show the output voltage avail-
able at any given output current for the various Voltage
Selector positions.
The actual operating point of load voltage and current is
deter ined by type of process, electrode, shield gas,
wire feed speed, and operating technique.

9
SECTION 2 INSTALLATION
The lifting eyebolt is to be used for lifting power
source only. Do not use when additional accesso-
ries are attached to the power source.
If lifting eyebolt is not installed, the hole must be
plugged to prevent entry of dirt and water.
2.2 ELECTRICAL INPUT CONNECTIONS
It is recommended that a line disconnect switch be
installed in the input circuit to the welding machine.
This would provide a safe and convenient means to
completely remove all electrical power from the
weldingmachinewheneveritisnecessarytoperform
any internal function on the unit.
Before making electrical input connections to the
weldingmachine,“MachineryLockoutProcedures”
should be employed. If the connections are to be
made from a line disconnect switch, the switch
should be padlocked in the off position. If the con-
nection is made from a fusebox, remove the fuses
from the box and padlock the cover in the closed
position.Iflockingfacilitiesarenotavailable,attach
a red tag to the line disconnect switch (or fuse box)
to warn others that the circuit is being worked on.
2.2.1 INPUT ELECTRICAL REQUIREMENTS
The power source is a single-phase unit and must be
connected to a single-phase power supply. The unit
should be operated on a dedicated circuit to prevent
impairmentofperformanceduetoanoverloadedcircuit.
Theprimaryinputvoltagerequirementsarenotedonthe
unit’s rating plate.
2.1 LOCATION
A proper installation site should be selected for the
welding machine, if the unit is to provide dependable
service and remain relatively maintenance free.
A proper installation site permits freedom of air move-
mentintoandoutoftheweldingmachine,andalsoleast
subjects the unit to dust, dirt, moisture, and corrosive
vapors. A minimum of 18 inches (46 cm) unrestricted
spacemustbemaintainedbetweentheweldingmachine
side and rear panels and the nearest obstruction.
The installation site should also permit easy removal of
the welding machine outer enclosure for maintenance
functions.
CAUTION: Do not place any filtering device over the
intake air passages of the welding ma-
chine as this would restrict the volume of
intakeairandtherebysubjectthewelding
machineinternalcomponentsto anover-
heatingconditionandsubsequentfailure.
Warranty is void if any type of filtering
device is used.
If a forklift vehicle is used for lifting the unit, be sure that
theliftforksarelongenoughtoextendcompletelyunder
the base.
2.1.1 LIFTING EYEBOLT
Toinstallliftingeyeboltfurnishedwiththepowersource,
proceed as follows.
A. Remove the hole plug from the nut in the cover.
B. Install the eyebolt and fully tighten with a suitable
tool.
Customers Fused Line
Disconnect Switch
(See Table 2.1 for
recommended fuses)
Figure 2.1 Primary Voltage Diagram

10
SECTION 2 INSTALLATION
TABLE 2.1 Recommended Input Fuse Size
Full
Primary Load
Input Line Fuse
Volts Amperes Size
208 52 90
230 58 90
380 36 50
400 34 50
415 32 50
460 31 40
575 25 30
2.2.2 INPUT CONDUCTOR CONNECTIONS
Theunitisprovidedwithathreeconductorprimaryinput
cablewithoutplug.Thegroundlead(green)ofthiscable
should be connected to a reliable ground and the two
remaining wires (black and white) should be connected
totheseparatelyfusedlinesofthedisconnectorbreaker.
SeeTable 2.1 forrecommendedfuse sizes touseinthe
disconnect.
All units leave the factory with their primary electrical
input requirements internally-connected for the highest
voltage rating available (e.g.: 460-volt for the 200/230/
460-volt units; and 575-volt for the 230/460/575-volt
units).
Remove right side panel from unit and locate the input
terminal board (see Figure 2.2). If the unit is to be
operated from another input voltage, the links on the
inputterminalboardmustberesetforthatparticularinput
voltage. Always verify the input voltage and check the
link arrangement regardless of factory setting. The volt-
agelinks aresetupby reconfiguringthecopper linkbars
to the silkscreened voltage designation for the desired
voltage.
2.3 OUTPUT WELDING CONNECTIONS
(SECONDARY)
Beforemakinganyconnectionstothepowersource
output terminals, make sure that all primary input
power to the machine is off.
The output terminals are located on the front panel
(Figure 2-3). Two output terminals are provided. The
NEGATIVE(-)terminalislocatedontheleftsideandthe
POSITIVE (+) terminal is located on the right side. The
outputcableconnectionswilldependonthematerialsto
beweldedandontheweldingprocessdesired.Table2-
2 provides the recommended cable output sizes. Keep
welding cables as short as possible.
Table 2-2. Output Cable Sizes (Secondary)
Welding Total Length (Feet) of
Current Cable in Weld Circuit*
50 100 150 200 250
100 6 4 3 2 1/0
150 4 3 1 1/0 2/0
200 3 1 1/0 2/0 3/0
250 2 1/0 2/0 3/0 4/0
300 1 2/0 3/0 4/0 4/0
400 2/0 3/0 4/0 4/0 2-2/0
500 3/0 3/0 4/0 2-2/0 2-3/0
* Total cable length includes work and electrode cables. Cable size
is based on direct current, insulated copper conductors, 100-
percentdutycycleandavoltage dropof4orlessvolts. The welding
cable insulator must have a voltage rating that is high enough to
withstand the open circuit voltage of the machine.
2.4 CONTROL CONNECTIONS
Refer to Figure 2-3.
2.4.1 Wire Feeder Control
TheWirefeedercontrol cableconnectionis providedby
a 19-pin receptacle (J1) located at the center of the
power source front panel. This receptacle will operate
ESAB wire feeders with 19 pin control cables including
the Mig 2E, Mig 4HD, Mobile Master 2cv and Mobile
Master 2cvcc.
2.4.2 - 42V Circuit Breaker (CB2)
The 42V resettable circuit breaker (CB2) located on the
powersourcefrontpanelprotectsthe42voltwirefeeder/
controlcircuitryagainstovercurrent.(Table5-1provides
troubleshootinginformation).
2.4.3 - 24V Circuit Breaker (CB1)
The24Vresettablecircuit breaker located on the power
source front panel (CB1) protects the 24 volt control
circuitryagainstovercurrent.(Table5-1providestrouble-
shootinginformation.
DANGER
HIGH
VOLTAGE
Figure 2.2 - Input Terminal Board
208/230/460V Illustrated in the 460 Volt Configuration)
* Double Links

SECTION 3 OPERATION
11
Figure 3.1 - Control and Cable Connections
3.1 CONTROLS (See Figure 3.1)
3.1.1 POWER SWITCH (ON-OFF) (I-O)
The power switch on the front panel energizes the
primary of the main transformer and the low voltage
circuity with the switch in the "ON" ("I") position. The
white READY light will light up.
When the unit overheats or exceeds the duty cycle, the
white light will shut off and output operations will shut
down.The fan will continueto run to coolthe unit down.
3.1.2 CONTACTOR CONTROL
The solid state contactor is used to energize the output
terminals.Thiscontactoriscontrolledonandoffwiththe
torch trigger.
Because of the charged capacitor bank in the sec-
ondary circuit, the output voltage will take a few
seconds before falling to zero volts.
3.1.3 VOLTAGE, PANEL/REMOTE SWITCH
Withthis switch inthe"Panel" position, outputvoltageis
controlled by adjusting the voltage control knob on the
front panel to the desired output. In the "Remote" posi-
tion, output is controlled at the wire feeder or remote
control.
3.1.4 VOLTAGE CONTROL
This control allows the operator to adjust the output
voltage. Placing the Panel/Remote switch in the "Re-
mote" position disables the voltage control on the front
panel
3.1.5 FEEDER SELECTOR SWITCH
This switch selects the control for either a wire feeder
connected to receptacle J1 or the spool gun connected
to J2.
Powersourcecontactorbecomesenergizedthemo-
ment the torch trigger is depressed. Arcing can
occurifthewireisbroughttoagroundorworkpiece.
Always keep the torch away from ground or the
workpiece until welding is to begin.
P WER
N/ FF
SWITCH
READY
LIGHT
UTPUT
V LTAGE
C NTR L
NEGATIVE
UTPUT CABLE
C NNECTI N
5A CIRCUIT BREAKERS
L CATI N F R PTI NAL
METER KIT
SP L GUN/
WIRE FEEDER SWITCH
PANEL/REM TE
SWITCH
3A FUSE
SP L GUN C NNECTI N
WIRE FEEDER
C NTR L CABLE
C NNECTI N
P SITIVE
UTPUT CABLE
C NNECTI N

SECTION 3 OPERATION
12
3.2 OPERATING PROCEDURES
3.2.1 OPERATING SAFETY PRECAUTIONS
Co ply with all ventilation, fire and other safety require-
ents for arc welding as established in the SAFETY
Section at the front of this anual.
Also re e ber the following:
A. Because of the radiant energy of the welding arc and
the possibility of drawing an arc before the hel et
is lowered over the face, the operator should
wear flash goggles with filter lenses under his hel-
et. The hel et filter plate should be shade
nu ber 11 (nonferrous) or 12 (ferrous). All those
viewing the arc should use hel ets with filter plates,
as well as flash goggles. Nearby personnel should
wear flash goggles.
B. The radiant energy of the arc can deco pose
chlorinated solvent vapors, such as trichloroethyl-
ene and perchlorethylene, to for phosgene,
even when these vapors are present in low concen-
trations. DO NOT weld where chlorinated solvents
are present in at ospheres in or around the arc.
C. DO NOT touch the electrode, nozzle or etal parts
in contact with the when power is ON: all are
electrically energized (HOT) and can possibly cause
a fatal shock. DO NOT allow electrode to touch
grounded etal: it will create an arc flash that can
injure eyes. It ay also start a fire or cause other
da age.
D. When working in a confined space, be sure it is safe
to enter. The confined space should be tested for
adequate oxygen (at least 19%) with an approved
oxygen easuring instru ent. The confined space
should not contain toxic concentrations of fu es or
gases. If this cannot be deter ined, the operator
should wear an approved air supplied breathing
apparatus.
Avoid gas leaks in a confined space, as the leaked
gas can dangerously reduce oxygen concentration
in the breathing air.
DO NOT bring gas cylinders into confined spaces.
When leaving a confined space, shut OFF gas
supply at the source to prevent gas fro leaking into
the space, if the switch is accidently kept depressed.
Check the breathing at osphere in the confined
space to be sure it is safe to reenter.
E. Never operate the equip ent at currents greater
than the rated a pere capacity. Overheating will
occur.
F. Never operate equip ent in a da p or wet area
without suitable insulation for protection against
shock. Keep hands, feet and clothing dry at all
ti es.
G. Whenever the equip ent is left unattended, turn all
control and power source switches and gas supplies
OFF and open the ain line switch.
H. Wear dark substantial clothing to protect exposed
skin fro arcburn, sparks and flying hot etal.
I. Turn off welding power before adjusting or replacing
electrodes.
Never operate the weldi g machi e with a y portio
of the outer e closure removed. I additio to a
electrical shock hazard, improper cooli g may result
i damage to the weldi g tra sformer a d the weld-
i g machi e compo e ts. Warra ty is void if the
machi e is operated with a y portio of the outer
e closure removed.
3.2.2 PRE-WELD REQUIREMENTS
Before welding co ences, with all power OFF, check
the following:
A. All safety require ents have been read and under-
stood.
B. All hoses and cables are in good condition, safely
insulated and securely connected.
C. Turn on gas supply by slowly opening cylinder valve
to full ON.
D. Correct size wire accessories have been installed on
the wire feeder, wire pressure set, and guide tube is
installed for type and size wire you plan to use, refer
to Tables 1.2 and 1.3.
E. Spool of correct size wire is locked in place, brake
tension is set, and wire is properly threaded through
the inlet guide to the torch tip.
F. Make sure that the etal to be welded is properly
prepared:
a. Re ove loose surface rust, scale or paint with
wire brush or sander.

SECTION 3 OPERATION
13
Power source solid state co tactor becomes e er-
gized the mome t the torch trigger is depressed.
Arci g ca occur if the wire is brought to a grou d.
Keep the torch away from grou d u til weldi g is to
begi .
C. To start the weld, hold the torch so the welding wire
is approxi ately 1/4-in. fro the work, then press
the torch trigger.
D. The welding wire should be pointed into the joint
at angles of approxi ately 45° for fillet welds, and
approxi ately 90° for butt welds, (Fig 3.2).
E. The torch angle relative to the length of the weld
should be approxi ately 10° fro the vertical (Fig.
3.3).
F. When welding in the vertical position, traveling either
up or down, it is very i portant to keep the arc on the
leading edge of the puddle to ensure co plete pen-
etration.
G. So e welders who are accusto ed to welding with
stick electrodes ay tend to push the torch into the
weld. This is neither necessary nor desirable, since
the wire electrode is being echanically fed into the
weld.
H. To stop the weld, release the trigger and pull the torch
fro the work. When leaving equip ent unattended,
always shut OFF and disconnect all input power and
shut off shielding gas at source.
This equip ent is provided with a ther ostat in the
transfor er windings which will open and prevent the
contactor fro closing if the transfor er windings are
overheated. If the ther ostat opens, the ready light will
go out. Allow the equip ent to idle with fan running until
the light co es back on before atte pting to weld again.
b. Atte pting to weld over grease or oil can cause
weld defects.
c. Before welding on alu inu , be sure to clean
surface thoroughly using a stainless steel brush.
3.2.3 SET-UP PROCEDURE
A. Deter ine the base plate aterial, wire type and
plate thickness to be welded.
B. Set VOLTAGE control and WIRE FEED speed con-
trol (ip ) on the wire feeder to the reco ended
settings. If fine tuning is required while welding,
adjust the VOLTAGE control.
O ly qualified perso el should make these cha ges.
Make certai the primary power has bee disco -
ected a d all safety procedures have bee followed
before proceedi g with these i structio s.
3.2.4 WELDING OPERATION
A. Turn Power switch (on unit) to ON (I) position -- be
careful not to operate the torch switch.
NOTE: The 251cv features an automatic fan that ener-
gizes only to protect components from over-
heating. The fan will continue to run until the
components are coole sufficiently.
B. Before starting the weld, the welding wire should
extend about 1/2-inch beyond the end of the nozzle.
Adjust this length by either clipping off the end of the
wire with insulated cutters or by using the torch
switch.

SECTION 3 OPERATION
14
Figure 3.2 - Continuous Weld Conditions
Figure 3.3 - Angle of Welding Wire with Joint
FILLET WELD BUTT WELD
45°
90°
10° 10°
TRAVEL TRAVEL

SECTION 4 MAINTENANCE
15
.1 GENERAL
Be sure the bra ch circuit or mai disco ect switch
is off or electrical i put circuit fuses are removed
before attempti g a y i spectio or work o the
i side of the weldi g machi e. Placi g the power
switch o the weldi g machi e i the OFF positio
does ot remove all power from i side of the equip-
me t.
I spectio , troubleshooti g a d repair of this equip-
me t may ordi arily be u dertake by a compete t
i dividual havi g at least ge eral experie ce i the
mai te a ce a d repair of semi-co ductor elec-
tro ic equipme t. Mai te a ce or repair should ot
be u dertake by a yo e ot havi g such qualificatio s.
Shut OFF shielding gas supply at source.
To aid in checking and servicing, use Sche atic, Figure
5.1.
.2 INSPECTION AND SERVICE
Keep Equip ent in clean and safe operating condition
free of oil, grease, and (in electrical parts) liquid and
etallic particles which can cause short-circuits.
Regularly check cylinder valves, regulators, hoses, and
gas connections for leaks with soap solution.
Check for and tighten loose hardware including electrical
connection. Loose power connections overheat during
welding.
I ediately replace all worn or da aged power cables
and connectors. Check for frayed and cracked insula-
tion, particularly in areas where conductors enter Equip-
ent.
The electrode wire and all etal parts in contact with it
are electrically energized while welding. Inspect these
parts periodically for defective insulation and other elec-
trical hazards.
If u i sulated cable a d parts are ot replaced, a
arc caused by a bared cable or part touchi g a
grou ded surface may damage u protected eyes or
start a fire. Body co tact with a bared cable, co ec-
tor, or u covered co ductor ca shock, possible
fatally.
Keep power cables dry, free of oil and grease, and
protected at all ti es fro da age by hot etal and
sparks.
Clean dirt and etal particles fro drive roll groove
weekly; replace roll if badly worn.
.3 POWER SOURCE
It is reco ended that the rectifier be cleaned occasion-
ally by blowing it out with co pressed air. This cleaning
operation is necessary so that axi u cooling will be
acco plished by the air strea . This should be done
periodically, depending upon the location of the unit and
the a ount of dust and dirt in the at osphere.
The her etically sealed silicon rectifiers are specially
designed for welding achine use and will not age or
deteriorate in use. The diodes are ounted on a heat
sink. A periodic cleaning of dust and dirt fro these is
necessary to insure cooling of the rectifiers. Access is by
re oval of top cover and side panels. Should any rectifier
accidentally be da aged and need replace ent, it can
be quickly re oved fro the heat sink. The replace ent
should be of the sa e type as the one re oved, and
should be locked securely to the sink, preferably with a
torque wrench set for axi u of 25 ft. lbs. and a
ini u of 20 ft. lbs. Excessive torque will distort the
echanical structure and ay break the her etic seal,
whereas too little torque will result in i proper electrical
connections.
4.3.1 FAN MOTOR
All odels are equipped with an exhaust fan and rely on
forced draft for adequate cooling for high duty cycles and
overloads.
4.3.2 TRANSFORMER
Occasional blowing out of the dust and dirt fro around
the transfor er is reco ended. This should be done
periodically depending upon the location of the unit and
the a ount of dust and dirt in the at osphere. The
welding achine case cover should be re oved and a
clean, dry air strea should be used for this cleaning
operation.
If it should become ecessary to replace this or a y
other circuit breaker i the weldi g machi e, e sure
that the proper size is used as a replaceme t.
4.3.3 OVER-TEMPERATURE PROTECTION
The achine is equipped with 2 over-te perature ther-
ostats. On continued high current application, if a
ther ostat reaches an abnor ally high te perature, it
will deenergize the contactor, the READY light on the
front panel will go off and the fan will continue to run. This
ther ostat will reset itself auto atically after the trans-
for er windings have cooled to a safe level and the
READY light will co e back on. While deenergized,
neither the contactor nor wire feeder can be operated.

SECTION 5 TROUBLESHOOTING
16
5.1 GENERAL TROUBLESHOOTING
If welding equip ent doesnt work right despite co pli-
ance with checklist inspect as follows:
A. With all power controls ON and other operating
controls at required settings, visually check all power
cables and connections for evidence of overheating
or sparking.
To avoid shock, do NOT touch electrode wire or
parts i co tact with it, or u i sulated cable or
co ectio s.
B. Isolate trouble to one part of the welding installation:
pri ary power supply, power source, Feeder or wire
guide train (casing, drive rolls, liners and contact tip).
If this inspection indicates trouble in the Feeder, use
Troubleshooting Guide, in the feeder anual.
Ma y troubleshooti g situatio s require that the
power remai O a d that power termi als i the
equipme t carry voltage. Exercise extreme cautio
whe worki g o LIVE equipme t. Avoid co tact
with electrical compo e ts, except whe testi g
with a appropriate i strume t.
Do ot make a y repairs to equipme t u less you are
fully qualified, as described i the mai te a ce sec-
tio .

SECTION 5 TROUBLESHOOTING
17
TABLE 5.1 TROUBLESHOOTING GUIDE
WELD CONDITION POSSIBLE CAUSE REMEDY
1. No weld or control power. a. Pri ary input power not available. a. Check for Voltage at pri ary input.
b. Faulty connection, pri ary input b. Repair or replace cable or switch
cable, or power switch as necessary.
c. Blown line fuse. c. Replace fuse. If it blows again,
contact ESAB representative.
2. No welding power. a. Ther ostat has opened. a. Wait 15 inutes with fan running. If
still no power, contact ESAB repre-
sentative.
b. Shorted S.C.R. in ain rectifier. b. Check S.C.R. and replace if reqd.
c. Open in wiring c. Check all wiring.
3. Fan does not run. No a. See Weld Condition 1. a. Repair or replace cable or switch
proble - ther ostatically as necessary.
controlled fan.
b. Defective fan otor (MTR1) b. Replace fan otor (MTR1).
4. Erratic welding current. a. Poor workpiece connection. a. Check workpiece connection.
b. Loose welding connections. b. Check all connections.
c. Wrong polarity. c. Check for correct polarity.
5. Welding output Voltage a. Low line Voltage. a. Use correct voltage.
and/or current too low. b. Welding cables too long or too b. Use correct cable size.
s all.
c. Loose connection. c. Check all welding cable
connections.
d. Defective capacitor bank. d. Check capacitors for low
leakage resistance.
6. Stringy irregular bead, a. Torch oved too fast. a. Move torch slower along sea s.
poor penetration. b. Controls are not set properly for b. Reset control properly.
etal gauge thickness.
c. Wrong polarity. c. Check for correct polarity.
7. Bead not centered. a. Nozzle not aligned. a. Move torch nozzle parallel to
and centered over sea .
8. Bead too large. a. Torch oved too slowly. a. Move torch faster along sea .
9. Unstable arc, excess a. Incorrectly set controls. a. Reset controls.
spatter, weld porous.
b. Shield gas flow is too low or b. See Condition 10.
stopped.
c. Torch nozzle is too far fro work. c. Maintain 1/4" (6 ) wire
tip to work; hold closer to work.
d. Faulty regulator or adapter. d. Check flow at outlet;
replace faulty ite .
e. Faulty gas solenoid valve. e. Replace solenoid valve.
f. Wrong polarity. f. Check polarity.

SECTION 5 TROUBLESHOOTING
18
WELD CONDITION POSSIBLE CAUSE REMEDY
10.Shield gas flow low or a. Cylinder valve closed. a. Turn off regulator. Slowly open
stopped cylinder valve, until regulator gauge
indicates pressure.
b. Cylinder e pty. b. Replace cylinder if gauge so indicates.
c. Faulty regulator or adaptor. c. Check flow at outlet; replace
faulty ite .
d. Faulty gas solenoid valve. d. Replace solenoid valve.
11.Wire stubs on work a. Controls not set properly for a. Reset controls properly.
while welding. etal gauge, thickness.
12.Wire burns back into a. Contact tip loose. a. Fir ly tighten with pliers.
contact tip. b. Tip too close to work. b. Maintain 1/4" (.6 c ) wire
protrusion; hold Torch further
fro work.
c. Wire feed slipping. c. Increase pressure on pressure
roll by adjusting pressure knob.
d. Contact tip da aged. d. Tri back tip 1/16" (1.6 c ) ax.
Replace if still faulty.
e. Voltage setting too high. e. Adjust setting.
f. Drive or pressure roll dirty or worn. f. Clean rolls or replace.
13.Wire does not feed; otor a. Kink, etc. in wire, or wire bound a. Straighten; or feed wire until
running (drive roll turns). on reel. clear and cut off.
b. Wire freezing to contact tip b. Free freeze, or re ove contact
(burnback). tip feed wire until clear cut end free,
and replace tip.
c. Clogged liner. c. Replace liner.
14.Wire does not feed; a. Motor a. With wire speed dial on 700,
otor NOT running press trigger. If voltage
(drive roll does not turn). appears across otor leads
but otor does not run, check
otor gears and co utator
areas.
b.Power switch SW1 and fuses. b. With SW1 ON, if voltage
across ter inal 1 and 3 is 24 VAC,
switch and fuses are good.
c. Speed Potentio eter. c. Check for 10K oh s across
POT outside ter inals.
d. Malfunctioning ain control board. d. Replace ain control board.
15.Wire feed does not stop. a. Torch trigger switch. a. Check continuity of Torch trigger
circuit; check to see if trigger lever
is stuck in ON position.
b. Main PCB. b. Check for proper operation.
16.Gas continues to flow a. Gas solenoid valve stuck open. a. Tap solenoid or click on and off
after trigger release. to clear valve.
TABLE 5.1 TROUBLESHOOTING GUIDE (co t.)

19
D-37309-B
Figure 5.1 - Schematic Diagram, 251cv Power Source, All Models

20
D-37310-B
Figure 5.2 - Wiring Diagram, 251cv Power Source, All Models