Lincoln Electric Multi-Weld 350 Arc Converter User manual

Multi-Weld 350 Arc Converter
®
OPERATORʼS MANUAL
IM664-C
September, 2011
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 READ-
ING THIS MANUAL AND THE
SAFETY PRECAUTIONS CON-
TAINED THROUGHOUT.And,
most importantly, think before
you act and be careful.
350 340
ELECTRIC
LINCOLN
®
MULTI-WELD 350
ELECTRIC
LINCOLN
®
MULTI-WELD 350
For use with machines having Code Numbers: 10645
10736
11148
11854
• 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 © Lincoln Global Inc.

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 vaporiz-
ing 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.
i
SAFETY
i
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. A Free 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
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 can-
cer, 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

ii
SAFETY
ii
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 within applicable OSHA PEL and
ACGIH TLV limits using local exhaust or mechanical
ventilation. In confined spaces or in some circum-
stances, outdoors, a respirator may be required.
Additional precautions are also required when welding
on galvanized steel.
5. b. The operation of welding fume control equipment is affected
by various factors including proper use and positioning of
the equipment, maintenance of the equipment and the spe-
cific welding procedure and application involved. Worker
exposure level should be checked upon installation and
periodically thereafter to be certain it is within applicable
OSHA PEL and ACGIH TLV limits.
5.c. 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 prod-
ucts.
5.d. 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.e. 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.f. Also see item 1.b.

iii
SAFETY
iii
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.
WELDING and CUTTING
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 cir-
cuits. This can create fire hazards or overheat lifting chains
or cables until they fail.
6.h. Also see item 1.c.
6.I. Read and follow NFPA 51B “ Standard for Fire Prevention
During Welding, Cutting and Other Hot Work”, available
from NFPA, 1 Batterymarch Park, PO box 9101, Quincy, Ma
022690-9101.
6.j. Do not use a welding power source for pipe thawing.
Refer to http://www.lincolnelectric.com/safety for additional safety information.

iv
SAFETY
iv
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 suiv-
antes:
Sûreté Pour Soudage A LʼArc
1. Protegez-vous contre la secousse électrique:
a. Les circuits à lʼélectrode 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 sʼisoler 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 lʼeau 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 sʼapplicuent 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 nʼimporte quelle partie
du corps.
3. Un coup dʼarc peut être plus sévère quʼun coup de soliel,
donc:
a. Utiliser un bon masque avec un verre filtrant approprié
ainsi quʼun verre blanc afin de se protéger les yeux du ray-
onnement de lʼarc et des projections quand on soude ou
quand on regarde lʼarc.
b. Porter des vêtements convenables afin de protéger la
peau de soudeur et des aides contre le rayonnement de
lʻarc.
c. Protéger lʼautre personnel travaillant à proximité au
soudage à lʼaide dʼécrans appropriés et non-inflammables.
4. Des gouttes de laitier en fusion sont émises de lʼarc de
soudage. Se protéger avec des vêtements de protection libres
de lʼhuile, tels que les gants en cuir, chemise épaisse, pan-
talons 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 lʼon pique le laitier.
6. Eloigner les matériaux inflammables ou les recouvrir afin de
prévenir tout risque dʼincendie 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 dʼincendie.
8. Sʼassurer que la masse est connectée le plus prés possible
de la zone de travail quʼil est pratique de le faire. Si on place
la masse sur la charpente de la construction ou dʼautres
endroits éloignés de la zone de travail, on augmente le risque
de voir passer le courant de soudage par les chaines de lev-
age, câbles de grue, ou autres circuits. Cela peut provoquer
des risques dʼincendie ou dʼechauffement des chaines et des
câbles jusquʼà ce quʼils 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
dʼopérations de dégraissage, nettoyage ou pistolage. La
chaleur ou les rayons de lʼarc 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
lʼélectricité 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, Iʼinstallation et lʼentretien du poste seront
effectués par un électricien qualifié.
3. Avant de faires des travaux à lʼinterieur de poste, la debranch-
er à lʼinterrupteur à la boite de fusibles.
4. Garder tous les couvercles et dispositifs de sûreté à leur
place.

vv
Thank You for selecting a QUALITY product by Lincoln Electric. We want you
to take pride in operating this Lincoln Electric Company product
••• as much pride as we have in bringing this product to you!
Read this Operators Manual completely before attempting to use this equipment. Save this manual and keep it
handy for quick reference. Pay particular attention to the safety instructions we have provided for your protection.
The level of seriousness to be applied to each is explained below:
WARNING
This statement appears where the information must be followed exactly to avoid serious personal injury or loss of life.
This statement appears where the information must be followed to avoid minor personal injury or damage to this equipment.
CAUTION
Please Examine Carton and Equipment For Damage Immediately
When this equipment is shipped, title passes to the purchaser upon receipt by the carrier. Consequently, Claims
for material damaged in shipment must be made by the purchaser against the transportation company at the
time the shipment is received.
Please record your equipment identification information below for future reference. This information can be
found on your machine nameplate.
Product _________________________________________________________________________________
Model Number ___________________________________________________________________________
Code Number or Date Code_________________________________________________________________
Serial Number____________________________________________________________________________
Date Purchased___________________________________________________________________________
Where Purchased_________________________________________________________________________
Whenever you request replacement parts or information on this equipment, always supply the information you
have recorded above. The code number is especially important when identifying the correct replacement parts.
On-Line Product Registration
- Register your machine with Lincoln Electric either via fax or over the Internet.
• For faxing: Complete the form on the back of the warranty statement included in the literature packet
accompanying this machine and fax the form per the instructions printed on it.
• For On-Line Registration: Go to our WEB SITE at www.lincolnelectric.com. Choose “Support” and then “Register
Your Product”. Please complete the form and submit your registration.
CUSTOMER ASSISTANCE POLICY
The business of The Lincoln Electric Company is manufacturing and selling high quality welding equipment, consumables, and cutting equip-
ment. Our challenge is to meet the needs of our customers and to exceed their expectations. On occasion, purchasers may ask Lincoln
Electric for advice or information about their use of our products. We respond to our customers based on the best information in our posses-
sion at that time. Lincoln Electric is not in a position to warrant or guarantee such advice, and assumes no liability, with respect to such infor-
mation or advice. We expressly disclaim any warranty of any kind, including any warranty of fitness for any customer’s particular purpose,
with respect to such information or advice. As a matter of practical consideration, we also cannot assume any responsibility for updating or
correcting any such information or advice once it has been given, nor does the provision of information or advice create, expand or alter any
warranty with respect to the sale of our products.
Lincoln Electric is a responsive manufacturer, but the selection and use of specific products sold by Lincoln Electric is solely within the control
of, and remains the sole responsibility of the customer. Many variables beyond the control of Lincoln Electric affect the results obtained in
applying these types of fabrication methods and service requirements.
Subject to Change – This information is accurate to the best of our knowledge at the time of printing. Please refer to www.lincolnelectric.com
for any updated information.

vi
vi TABLE OF CONTENTS
Page
Installation.......................................................................................................................Section A
Technical Specifications.......................................................................................................A-1
Product Description. .............................................................................................................A-2
Recommended Equipment and Processes ..........................................................................A-3
Multi-System Power Source..........................................................................................A-3
Distribution Box .............................................................................................................A-3
“Pig-Tail” Leads and Connectors ..................................................................................A-3
Remote Output Control Options....................................................................................A-4
CV Mode Wire WElding ................................................................................................A-4
CC Mode Stick Welding and Gouging...........................................................................A-4
Quick-Connect “Pig-Tails” ....................................................................................................A-4
Attachment and Arrangement of “Pig-Tails” .........................................................................A-4
Work Connection..................................................................................................................A-5
Case Grounding ...................................................................................................................A-5
Inter-Connection of Converters ............................................................................................A-6
Connection for Negative Polarity Welding............................................................................A-7
Power Source Setup ............................................................................................................A-7
________________________________________________________________________________
Operation.........................................................................................................................Section B
Front Panel Controls ............................................................................................................B-1
Recessed Panel Controls.....................................................................................................B-2
Paralleled Converters...........................................................................................................B-3
Remote Control of Paralleled Converters.............................................................................B-3
Transporting and Storage of the Multi-Weld 350..................................................................B-4
Cable Handling..............................................................................................................B-4
Transporting ..................................................................................................................B-4
Storage..........................................................................................................................B-4
Protection Features .............................................................................................................B-4
Fan as Needed (F.A.N.) ................................................................................................B-4
Over-Voltage Protection................................................................................................B-4
Over-Current Protection ................................................................................................B-4
Over-Temperature Shutdown........................................................................................B-5
________________________________________________________________________________
Maintenance ....................................................................................................Section D
Safety Precautions ................................................................................................D-1
Maintenance..........................................................................................................D-1
Digital Meter Calibration ...................................................................................................... D-1
Service .................................................................................................................................D-2
________________________________________________________________________________
Troubleshooting .............................................................................................................Section E
How to use Troubleshooting Guide ......................................................................................E-1
Troubleshooting Guide ...........................................................................................E-2 thru E-5
________________________________________________________________________________
Wiring Diagram and Dimension Prints..........................................................Section F
________________________________________________________________________
Parts Lists...................................................................................................P-361 Series
________________________________________________________________________

A-1
INSTALLATION
MULTI-WELD 350
A-1
TECHNICAL SPECIFICATIONS - Multi-Weld 350 (K1735-1)
PHYSICAL DIMENSIONS
TEMPERATURE RANGES
HEIGHT
11.6 in
295 mm
WIDTH
10.0 in
254 mm
DEPTH
21.5 in
546 mm
NET WEIGHT
59.5 lbs.
27.0 kg.
OPERATING TEMPERATURE RANGE
-40 to +122°F
-20 to + 50°C
STORAGE TEMPERATURE RANGE
-40 to +185°F
-40 to +85°C
ELECTRICAL SPECIFICATIONS
Output Rating @ 50ºC (122°F)
Input Rating @ 50ºC (122°F)
Max. Input Range
Max. O.C.V.
Output Preset Range
VOLTS
(DC+)
34
80
50-113 (Peak)
78
15-40
AMPS
(DC+)
350
165
30-350

A-2
INSTALLATION
MULTI-WELD 350
A-2
PRODUCT DESCRIPTION
The Multi-Weld 350 converter (K1735-1) is part of a
Multi-Weld system, ideally suited for construction site
welding, which uses a single DC power source, as the
only input supply, and provides independent full range
control of up to 350A continuous with each converter
arc for + polarity stick and wire processes, as well as
for arc-air gouging.(See Figure 1).
350 340
ELECTRIC
LINCOLN
®
MULTI-WELD 350
ELECTRIC
LINCOLN
®
MULTI-WELD 350
350 340
ELECTRIC
LINCOLN
®
MULTI-WELD 350
ELECTRIC
LINCOLN
®
MULTI-WELD 350
350 340
ELECTRIC
LINCOLN
®
MULTI-WELD 350
ELECTRIC
LINCOLN
®
MULTI-WELD 350
350 340
ELECTRIC
LINCOLN
®
MULTI-WELD 350
ELECTRIC
LINCOLN
®
MULTI-WELD 350
ELECTRIC
LINCOLN
®
MULTI-SOURCE
ELECTRIC
LINCOLN
®
MULTI-SOURCE
ELECTRIC
LINCOLN ® LN-25
ELECTRIC
LINCOLN ®
MULTI-WELD SYSTEM
MULTI-SOURCE
CONVERTER
CONVERTER
PARALLEL
CONVERTERS
DISTRIBUTION
BOX
WIRE FEEDER
WIRE
STICK
700 AMP ARC GOUGE
The Multi-Weld 350 is a DC to DC converter which
converts higher voltage/lower current input power to
lower voltage/higher current output power with over
90% efficiency.
For example; a single 600A continuous rated 70-80v
power source could supply up to five Multi-Weld 350
converters each wire welding at 300 amps, or about
ten converters for stick welding at 150 amps, with 26-
29v at the arcs.
The Arc Converter is a single "world" model built to
IEC and CSA standards and meeting the specific
needs inherent to construction site welding:
Versatile
• Constant Current (CC) mode for stick and gouging.
Includes Hot Start and Arc Force controls to opti-
mize CC performance, and can be paralleled for
higher capacity welding and arc gouging.
• Constant Voltage (CV) mode for positive polarity
cored and solid wire welding with arc-powered
feeders (such as the LN-25).
Portable
• Arcs can be moved quickly with the light weight
Converter thatʼs easy to carry, or pull, and is small
enough to fit through a 15" (38cm) diameter or 12"
x 16" (31x 41cm) elliptical man-hole.
• Converter is powered by the welding cable from
the DC power source, without the safety hazard of
high AC input supply voltages.
Figure 1

A-3
INSTALLATION
MULTI-WELD 350
A-3
• Converter welding controls are near the arc without
long control cables, and a receptacle is provided
for an optional remote for even closer user output
control.
Simple
• Easy installation with 10 ft. (3m) work clip lead and
user preference quick-connect "pigtails" for input
and electrode weld cables.
• Easy setup with only a few intuitive welding
controls and lit displays; including a single
Power/Mode switch with Input level light, and a
single presettable Output Control with separate
digital meters for Amps and Volts, featuring post-
weld five second memory display.
• Easy Service with quick to replace cable "pig-
tails"and "plug-in" assembly modules, including
accessible PC boards and interchangeable "plug-
n-play" panel instruments.
Robust
• Capacity is rated for continuous operation at 350
amps in 50°C (122°F) ambient temperature, and
can be paralleled to multiply CC mode output rat-
ing.
• Overload protection is provided with electronic lim-
iting of output current, and with thermostat and
over-voltage shutdown protection which automati-
cally reset.
• Outdoor operation protected with sealed control
and power electronics compartments, with sealed
interconnections, housing "potted" circuit boards,
and using "Central-Air" cooling with "Fan-As-
Needed" for less dirt intake.
• Handling (and mishandling protection) is enhanced
with light, but durably designed, aluminum con-
struction with front to back, top and bottom, han-
dles (also serving as "roll bar" and skid), and a
sheetmetal shell attached with 1/4" steel threaded
fasteners.
RECOMMENDED EQUIPMENT AND
PROCESSES
MULTI-SYSTEM POWER SOURCE
The Multi-Source 40KW 80VDC buss power source
(K1752-1) is recommended for use in the Multi-Weld
system. However, other DC power sources capable of
supplying the required system buss current, at above
60 volts, may be used. It is recommended that this
power source have lower output inductance (choke)
such as the Lincoln Electric DC-1000, DC-655 or DC-
600 set for max. output in CC mode. The power
source output VA capacity should be 10% greater
than the sum of the max. VA of the converter arcs
which may all be simultaneously welding or gouging:
Power Source (Volts x Amps) capacity > 1.1 x Sum
of Convertersʼ (Volts x Amps) arcs
DISTRIBUTION BOX
The Multi-Weld Distribution Box (K1736-1) is avail-
able for interconnection of the Multi-System using the
same "pig-tail" connection method provided with the
Multi-Weld 350 converter. Six cable strain-relief ports
are provided for connection of up to (12) cables for
distribution or "daisy-chain" inter-connection to other
boxes. Four "pig-tail" leads (see below) are included
with the Box.
"PIG-TAIL" LEADS AND CONNECTORS
Accessory "pig-tail" leads and Twist-Mate connectors
are available from Lincoln for extra connections to the
Muli-Weld 350 or the Distribution Box:
Order No. Description:
CL012705 22in.(56cm) long 2/0 (70mm2) cable
with 0.5in.(13mm) hole lug and cut-off
ends.
K852-70 Twist-Mate male insulated plug for
1/0-2/0 (50-70mm2) cable.
K852-95 Twist-Mate male insulated plug for
2/0-3/0 (70-95mm2) cable.
K1759-70 Twist-Mate female insulated recepta-
cle for 1/0-2/0 (50-70mm2) cable.
K1759-95 Twist-Mate female insulated recepta-
cle for 2/0-3/0 (70-95mm2) cable.

ATTACHMENT AND ARRANGEMENT OF
"PIG-TAILS"
To best suit the desired inter-connection of the
Converters the "pig-tail" cables may be routed into the
front cable channels, and/or into the back for single or
double "pig-tail" cables to the bottom-accessed cov-
ered cable connection studs. (See below and refer to
Figures 1 and 2.):
To connect the "pig-tail" cables to the Converter:
1. Stand the Converter vertically on its rear handle
and skid to gain access to the bottom stud
covers, then remove the two 0.25"(6.3mm)
screws securing each cover and fold out the
cover insulation.
2. Route the appropriate "pig-tail" cable lug ends
under the skid rail (for strain-relief) through the
desired front and/or rear corner channels to the
exposed 0.5"(13mm) stud, and remove the flange
nut with a .75"(19mm) wrench. Note: Input supply
cable(s) must connect through "INPUT +" labeled
channels, and output weld cable(s) must connect
through "ELECTRODE +" labeled channels.
3. Slip the "pig-tail" cable lug(s) over the stud and
re-secure the flange nut, making sure that lug(s)
nowhere touch any sheet metal of the stud hous-
ing, then fold back the cover insulation and
replace the stud cover.
BOTTOM VIEW
TO ELECT.
TO ELECT.
TO
WORK
TO POWER
SOURCE
TO POWER
SOURCE
+
INPUT
+
ELECTRODE
ELECT.
+
ELECT.
+
+
IN
+
IN
A-4
INSTALLATION
MULTI-WELD 350
A-4
REMOTE OUTPUT CONTROL OPTIONS
The Multi-Weld 350 is provided with a 6-pin remote
receptacle to permit use with the 25ft.(7.6 m) K857 or
100ft.(30.4 m) K857-1 Remote Output Control options,
or with the LN-25 equipped with the K444-1 Remote
Control option. These Remotes have single-turn reso-
lution on a Min to Max numbered dialplate.
CV MODE WIRE WELDING
The Converter in CV mode was designed for use with
an arc-powered wire feeder like the LN-25. The
Converter output is always "hot" when the mode
switch is not OFF, so it is recommended that the LN-
25 model be equipped with the internal contactor in
order to have a "cold" electrode when the gun trigger
is released.
The CV mode recommended processes are positive
(+) polarity wire welding within the output capacity of
the Converter, including:
CC MODE STICK WELDING
AND GOUGING
The CC mode recommended processes are positive
(+) polarity stick and arc gouging within the output
capacity of single, or paralleled, Converters; including:
QUICK-CONNECT "PIG-TAILS"
The Multi-Weld 350 is factory provided with two 21
in.(53 cm) long 2/0 AWG (70mm2 ) "pig-tail" cables
with their 0.5"(13mm) hole lug ends routed through
the "INPUT + "(on back) and "ELECTRODE + "(on
front) cable channels of the Converter and attached to
the bottom-accessed covered cable connection studs.
Attach the preferred standard user-provided Quick-
connect terminal (such as Lincoln Twist-Mate or
Tweco 2-MPC type) to the cut-off end of these cables.
Use the female connector on the "ELECTRODE +"
cable and the male connector on the "INPUT +" cable.

A-5
INSTALLATION
MULTI-WELD 350
A-5
ELECTRIC SHOCK can kill.
Be sure to follow the safety practice to
use the female connector on the cable
which would normally be electrically
"hot" (supply lead) if disconnected when
the system is energized, and the male on
the normally "cold" (load lead) side. If practical, shut
off power before connecting or disconnecting termi-
nals.
------------------------------------------------------------------------
WORK CONNECTION
Each Converter in the Multi-Weld System must have its
individual “Work” lead connected (clipped) to work. The
#3 AWG (27mm2) Work clip lead must have clean metal
connection to the work to complete the DC input supply
and output power circuits of the Multi-Weld 350.
ELECTRIC SHOCK can kill.
Do not disconnect the Work clip lead
without first switching OFF the
Converter panel switch. Failure to do
so will allow the work lead clip to be
electrically "hot" to work, and "hot" to
the electrode, through the circuit of the Converter
for about 5 seconds until the input contactor
opens.
------------------------------------------------------------------------
CASE GROUNDING
As shipped, the case of the Multi-Weld 350 is isolated
from all of the DC input and output welding terminals,
and is equipped with a grounding terminal screw (.31”
/ 7.9mm) marked with the symbol located on the
bottom rear of the Base assembly. ( Refer to the bot-
tom view figure.) In order to comply with CSA and UL
case grounding specifications, this terminal is provid-
ed for connection to weldment work which must be
properly grounded per methods meeting local and
national electrical codes. Refer to “Safety in Welding,
Cutting and Allied Processes”, ANSI Z49.1 (US) and
W117.2 (Canada).
Since any case fault would only involve the DC weld-
ing circuit, the size of the grounding lead should have
the capacity to ground the potential fault current with-
out burning open. Use at least #6AWG (13mm2), but
do not exceed the size of the input cable suppled with
the Multi-Weld 350.
Connect the Multi-Weld grounding lead to the work
piece separately from the Work clip. If the same clip is
used for both ground and work connection, the Multi-
Weld case will be electrically “hot” to the work if the
clip is removed without first switching OFF the panel
switch. ( Refer to the Work clip WARNING above).
WARNING
WARNING

A-6
INSTALLATION
MULTI-WELD 350
A-6
INTER-CONNECTION OF CONVERTERS
The input and electrode cables of the Multi-Weld 350
Converters may be inter-connected in a Multi-Weld
System using any combination of Distribution Box(es)
(see Figure 1), paralleling ( CC mode only) and
"daisy-chaining" (see Figure 2) which best fits the
field application setup within the capacity of the power
source supplying the system:
Power Source (Volts x Amp) capacity > 1.1 x Sum of
Convertersʼ (Volts x Amps) arcs
For Converters (operating at rated output) less than
200ft. (61m) from the power source, the following mini-
mum cable sizes are recommended for the indicated
quantity of Converters supplied by the input cable run to
keep cable temperature and voltage drop within accept-
able limits: (See Table.1)
DAISY CHAIN OPERATION
FIXED PARALLEL OPERATION
TO
WORK
T
O POWER
SOURCE
TO WORK
TO ELECT.
TO POWER
SOURCE
TO WORK
TO ELECT.
TO WORK
TO ELECT.
SEPARABLE PARALLEL OPERATION
TO WORK
TO WORK
TO POWER
SOURCE
TO POWER
SOURCE
TO WORK
TO ELECT.
TO ELECT.
PARALLEL
JUMPER
+
IN +
IN
ELECT.
+
+
IN
+
IN
ELECT.
+
+
IN +
IN
ELECT.
+
+
IN
ELECT.
+
+
IN
+
IN
ELECT.
+
ELECT.
+
ELECT.
+
ELECT.
+
Figure 2
ELECTRIC SHOCK can kill.
Paralled units may be powered
from more than one source.
Disconnect all inputs, including
outputs from other sources before
working on the equipment. Before
removing the parallel jumper be sure both
Converters are switched OFF. If not, the male
side of the first disconnection will be electri-
cally "hot" to work.
------------------------------------------------------------------
WARNING

A-7
INSTALLATION
MULTI-WELD 350
A-7
Table .1
Converters Cable Size
on Cable AWG (mm2 )
1 1/0 (50)
2 2/0 (70)
3 3/0 (95)
4 4/0 (120)
5 2x3/0 (2x95)
The output "Electrode" cable should be 2/0 AWG
(70mm2) if sized for rated output up to 200 ft.(61m)
from the Converter. If paralleled, the output cable to
the arc should be 4/0(120mm2).
ELECTRIC SHOCK can kill.
Do not disconnect the Work clip lead
without first switching OFF the
Converter panel switch. Failure to do
so will allow the work lead clip to be
electrically "hot" to work, and "hot" to
the electrode, through the circuit of
the Converter for about 5 seconds until the input
contactor opens.
------------------------------------------------------------------------
CONNECTION FOR NEGATIVE
POLARITY WELDING (See Figure 2A)
A Multi-Weld 350 may be used for Negative (straight)
polarity CV (Innershield) or CC processes if
connected per the diagram shown below:
No more than one Multi-Weld 350 may be
connected to a power source for Negative Polarity
welding. Multiple units connected to the same
power source may cause damage to the Multi-
Weld 350.
------------------------------------------------------------------------
This connection method will only permit using one
Multi-Weld arc on one power source, and cables have
to be run to the Multi-Weld from both (+) and (-) output
studs of the power source. This is required so that the
(-) electrode has a return path to both the Multi-Weld
and the Power Source, just like the normal (+)polarity
connection has a (-) return path to both the Multi-Weld
(through the Work Clamp) and to the Power Source
(through work connections). Both cable sizes are the
same, with capacity as recommended for normal (+)
connection.
If the power source itself can not perform the CV
negative welding process, the Multi-Weld is basically
serving very well as a process converter (ei; CV from
a CC power source), as well as a remote output
control. The advantage is that the same equipment
(Multi-Welds and CC Power Sources) is used for all
weld process applications.
POWER SOURCE SETUP
Refer to the Instruction Manual provided with the
Multi-Source power source, or other DC power source
being used, for input power supply connections,
output connections and controls setup.
In general:
1. Connect the positive (+) output connection terminal
to the input supplying the Multi-Weld system, and
the negative (-) output connection terminal to the
work. (see Figure 1).
2. If not using a Multi-Source power source;
a If an inductance control, or tap, is selectable,
use lowest inductance.
b. Use CC (Constant Current) mode, for maximum
supply voltage.
c. Set panel output control to maximum, for maxi-
mum current capacity.
d. Activate output with the "output terminals on"
switch, or jumper (2-4 on LE Co terminal strips).
WARNING
-+
W
W
or
ork
W
or
ork
LN-25 Wire
LN-25 Wire
Feeder
Feeder
W
W
or
ork
MW
MW
-3
-35
0
0
(-)
(-) Work Le
ad
ad
to
(-)
(-)
P
P
ow
owe
r
rS
ou
ou
rc
rce
s
s
tu
tud
a
nd
nd
(-)
(-) E
lectrode Lead
lectrode Lead
MW-
35
35
0
0(+
)
)Out
pu
put
Lea
Lead
t
o
oWork
MUL
MULT
I-WELD 350
I-WELD 350
Negative Polarity
Negative Polarity
DC
DC
POWER
POWER
SOURCE
SOURCE
CAUTION
Figure 2A

B-1
OPERATION
MULTI-WELD 350
B-1
FRONT PANEL CONTROLS
These few instruments are basic to the operation and
monitoring of the Converter. They are intuitively laid
out so that the panelʼs left side is weld current related,
and the right side is weld voltage related:
(1) Input Power/ Mode Switch has three positions:
Center is OFF which shuts off input power to the
Converter.
• Neither displays nor output is on if in OFF
position.
Left is on for CC (constant current) welding mode.
• Only AMPS digital meter is lit displaying the
preset current setting
• Output will be on at o.c.v. (open circuit voltage).
Right is on for CV (constant voltage) welding
mode.
• Only VOLTS digital meter is lit displaying the
preset voltage setting
• Output will be on at the output voltage setting.
(2) Output Control has 3-3/4 turn resolution with
slip-clutch to prevent control pot damage.
In CC mode it presets AMPS (30-350A range)
when not welding, and adjusts actual arc current
while welding .
In CV mode it presets VOLTS (15-40v range)
when not welding, and adjusts actual arc voltage
while welding.
(3) AMPS Digital Meter is a 3-1/2 digit LED meter
which displays:
Preset Amps in CC mode when not welding.
"Blank" in CV mode when not welding.
Actual Amps while welding in both CC and CV
modes.
1
2
34
56
7
8
9
10
INPUT
WORK
ELECTRODE
+
+
+
Figure 3
The numbered items of Figure 3, above, match the numbered items described below:

B-2
OPERATION
B-2
Average Amps for about 7 seconds after welding
stops in CC and CV modes .
• The 7 second memory display is indicated by
the displayʼs left-most decimal point blinking,
and is interrupted if arc is restarted.
Accuracy of Actual Amps is within 3%, and typi-
cally within 10 amps of Preset.
• An Actual Amps meter calibration adjustment
trimmer is provided. (See MAINTENANCE sec-
tion).
Two front screws secure the meter bezel which
holds a replaceable spatter shield lens (Lincoln
part no. T14807-9).
(4) VOLTS Digital Meter is a 3-1/2 digit LED meter
which displays:
Preset Volts in CV mode when not welding.
"Blank" in CC mode when not welding.
Actual Volts while welding in both CV and CC
modes.
Average Volts for about 7 seconds after welding
stops in CV and CC modes .
• The 7 second memory display is indicated by
the displayʼs left-most decimal point blinking,
and is interrupted if arc is restarted.
Accuracy of Actual Volts is within 3%, and typical-
ly within 1 volt of Preset.
• An Actual Amps meter calibration adjustment
trimmer is provided. (See MAINTENANCE
section).
Two front screws secure the meter bezel which
holds a replaceable spatter shield lens.
(5) Thermal Shutdown (yellow) Light turns on if out-
put is shutdown because internal overheating has
occurred. (See OVER TEMPERATURE SHUT-
DOWN in this section).
(6) Input Voltage (green) Light indicates appropriate
level of input supply voltage:
"On" for adequate input voltage over 50v for CC
or CV mode.
"Off" for inadequate input voltage under 50V, no
input or Power Switch OFF.
Note: If green light is "blinking" the input voltage may
be drifting above and below the 50V level due to loads
on supply and cables.
RECESSED PANEL CONTROLS
These instruments are recessed behind a screw
secured hinged cover panel, and are not typically
required for normal operator access. They may be left
covered, as factory set, or setup as desired with or
without the hinged cover secured:
(7)
Hot Start Control is provided to enhance arc start-
ing in both CC and CV modes with an extra output
"boost" at the arc strike that returns to the setting
level in less than a second (about 0.30 sec. in CC
mode, and 0.045 sec. in CV mode). This extra Hot
Start amplitude is adjustable from "0" (no extra) to
"10" (100% of setting extra), with the factory set "5"
(center) position typically good for most weld start-
ing.
(8) Arc Force Control in the CC mode with
Stick/Gouge slope.(See below). Arc Force prevents
"stubbing" of the electrode by providing extra weld
current if the arc voltage drops below about 14V.
This extra weld current is adjustable from "-10" (no
extra) to "+10" (60% of setting extra), with the fac-
tory set "0" (center) position typically good for most
welding.
In CV mode this control functions like an induct-
ance (or “pinch”) control to provide a “softer” less
penetrating arc when set toward “+10”, or a
“harsher” more penetrating arc when set toward
“-10”.
(9) CC Slope Switch is provided to enhance stick
welding on "fast-freeze" type electrodes (such as
E6010 and E7010) typically used on pipe welding
applications for fast root pass vertical down "drag"
technique (not "whipping"). If using this type of
application improved operating appeal may be
obtained if the CC Slope is switched from the fac-
tory set STICK / GOUGE position to the PIPE
position.
Note: The PIPE position uses a "drooping" type slope
(~22v/100A), so preset current (not actual cur-
rent) accuracy may be affected if arc length
voltage is not maintained at the typical 28V
used for these electrodes. Typically this error
should not be more than about 10 A.
(10) Remote Control Receptacle is provided to per-
mit the use of an optional Remote output control
to provide operator control even closer to the arc.
Connecting the Remoteʼs plug to this receptacle
automatically transfers output control from the
panel Output Control (item (2) above) to the
Remote pot control, which will function the same,
but with only single-turn resolution.
MULTI-WELD 350

B-3
OPERATION
B-3
Disconnecting the Remoteʼs plug from this recep-
tacle automatically transfers output control back
to the panel Output Control (item (2) above).
Remote output On/Off switching can also be
done thru this Remote Control receptacle. by per-
forming the following wiring changes:
1. Making sure the input to the Converter is
removed, remove the case wraparound.
2. Locate the 4-pin plug (P21) on the back
panel of the control box module, and cut the
jumper lead looping from the back of the
plug. (Refer to the Wiring Diagram in this
manual.) Insulate the cut lead ends and
leave long enough to possibly splice back
together again at some future time.
3. Replace the case wraparound.
4. Connect a user-provided remote switch
between pins D and E of an MS3106A-18-
12P plug (Lincoln part no. S12020-27 with
S12024-1 cable clamp). See diagram
below:
Pin: Remote Function:
A Max. of 10K pot
B Wiper of 10K pot
C Min. of 10K pot
D Output Switch
E Output Switch
F No connection
5. Connect this switch plug to the Multi-Weld
350 Remote Control Receptacle (10) with
switch opened. Closing the switch activates
the Converter output.
PARALLELED CONVERTERS
Multi-Weld 350 converters that are paralleled (see
INTER-CONNECTION OF CONVERTERS in the
INSTALLATION section) must each be set up in the
same manner in order to manage the arc current
drawn from each:
1) Set to CC mode with CC SLOPE switch set to
STICK/GOUGE.
2) Preset Output Controls of both paralleled
Converters to ~1/2 desired total Amps.
If arc current from each Converter gets too out of bal-
ance (primarily a problem if trying to use CV mode)
the hotter running Converter could go into current-lim-
iting and/or Thermal shutdown (See OVER-TEMPER-
ATURE SHUTDOWN in the INSTALLATION section),
which might then overload the other, or at least inter-
rupt the operatorʼs process. However, no damage will
occur to the Converters.
REMOTE CONTROL OF
PARALLELED CONVERTERS
(FOR CC STICK/GOUGE MODE ONLY)
Full Range remote control can be accomplished with a
separate optional Remote output control (see
INSTALLATION section) connected to each
Converter. The current contribution of each Converter
will depend on its remote output setting.
Partial Range remote control can be accomplished
with a single Remote Control connected to the output
Converter with the input Converter preset with its
panel Output Control to below the minimum desired
output range. The Remote Control, connected to the
output Converter, will control its output to add to the
preset level.
Remote Output On/Off switching maybe setup for
each of the paralleled Converters, but isolated, or
double-pole, switches must be used to activate each
separately but simultaneously.
MULTI-WELD 350

B-4
OPERATION
B-4
TRANSPORTING AND STORAGE
OF THE MULTI-WELD 350
CABLE HANDLING
The input and electrode cables are easily disconnect-
ed from the quick-connect "pig-tails", and the Work
lead can be reeled around the Multi-Weld 350 case
cradled by the base skid handles, to which the clip
can be secured.
TRANSPORTING
The Converter may be carried by one or two persons
using the front and rear top and bottom handles. It can
also be set vertically on a two wheel cart, or horizon-
tally on a wagon, to convey it longer distances.
STORAGE
The Multi-Weld 350 may be set on a floor, or shelf,
horizontally on its skid, or vertically standing on its
rear top and bottom handles.
PROTECTION FEATURES
The Multi-Weld 350 design features electronic protec-
tion systems to help assure reliable operation even
under adverse conditions. These systems include:
FAN AS NEEDED (F.A.N.)
The cooling fan will turn on when the arc starts and
remain on for about a minute after the arc is out to
cool down the power components.
This feature electronically controls the fan so it does
not run continuously when the power switch is turned
on. This will minimize the amount of contaminate and
clogging debris which may be drawn into the
Converter, in addition to the "Central-Air" system
design which intakes lower velocity air through the
higher side louvers and blows out through the lower
back louvers with higher velocity.
OVER-VOLTAGE PROTECTION
Average Input Voltage Protection
The Multi-Weld 350 input contactor will open if the
average input supply voltage is above 113VDC, and
will automatically reclose if the voltage drops back
below. During Over-Voltage Shutdown the panel dis-
plays will be as appropriate for the non-welding mode.
(See FRONT PANEL CONTROLS in this section).
When the contactor recloses the output of the
Converter will reactivate. Switching OFF input
power prevents unexpected reactivation.
------------------------------------------------------------------------
Peak Input Voltage Protection
The Chopper PC Board will stop switching and inter-
rupt the machine output whenever the input voltage
across the input capacitors exceeds their 150 volt rat-
ing. The Thermal Shutdown (yellow) panel light will be
lit when this protection is activated (Refer to OVER-
TEMPERATURE SHUTDOWN Section), and resets
when the voltage level drops below the protection
level. The input contactor also opens during this shut
down, until reset.
These features protects internal components of the
Converter from excessive voltage levels.
OVER-CURRENT PROTECTION
The max. output current of the Multi-Weld 350 is elec-
tronically limited, to protect internal power compo-
nents, so as not to exceed about 375 amps average
and 500 amps peak. When the current load starts to
exceed these limits the output is reduced (lower volt-
age) to sustain these max. levels, until the current is
reduced. even to a shorted output.
Prolonged output at this max. current limit level may
eventually overheat the Converterʼs internal power
components causing over-temperature shutdown.
(See following section).
Short circuit protection is also provided to reduce max.
output current to about 200 amps if the output voltage
is reduced, by loading or current limiting (see above),
to below 14 volts for over 7 seconds (indicating a
shorted output). The output current must be interrupt-
ed to reset this reduced protective level.
MULTI-WELD 350
CAUTION

B-5
OPERATION
B-5
OVER-TEMPERATURE SHUTDOWN
The Multi-Weld 350 has a temperature sensing ther-
mostat on the input diode heatsink to protect the
power components within the Converter from over-
heating. If this thermostat temperature exceeds
about95°C (203°F) the Converter will electronically
shut off the output,and turn on the Thermal Shutdown
(yellow) Light until the thermostat is cooled to reset.
A second over-load protection switch in the Imbalance
Protector Module is added to Multi-Weld 350 models
with codes 10736, and higher, but may be retrofitted
to original code 10645 models with the parts order
kit.This module senses for an imbalance of current
between the paralleled Chopper boards by sensing
the differential choke voltage. If this voltage exceeds
1V for a sustained time the Imbalance Protector will
also activate over-temperature shut down to protect
the higher current Chopper board from over heating.
Machines with code 11148, or higher, which use the
G4662-[ ] Peripheral PC Board, also include Peak
Input Voltage Protection that also lights the the
Thermal Shutdown (yellow) panel light if the unit out-
put is shutdown (See OVER-VOLTAGE PROTEC-
TION Section.).
When the thermostat resets the output of the
Converter will reactivate. Switching OFF input
power prevents reactivation, but also shuts off the
cooling fan which prolongs the reset time.
------------------------------------------------------------------------
During Over-Temperature Shutdown the panel dis-
plays will be as appropriate for the non-welding mode.
(See FRONT PANEL CONTROLS in this section),
except the fan will remain running and the Thermal
Shutdown (yellow) Light will be lit until reset. Typically,
If shutdown occurs repeatedly below 300 amps output
with fan running, imbalance of the Chopper board cur-
rent may likely be the cause.
MULTI-WELD 350
CAUTION

D-1
MAINTENANCE
D-1
3. Holding the unit by the front handles, so the
back is facing down, shake the loose debris out
of the unit. Raking out the heatsink fins may be
necessary for jammed debris.
4. If necessary, remove the case wraparound cover
and using the skid handles to hold upside down
carefully dump out any remaining loose debris,
or carefully blow out using low pressure air.
5. Reassemble the cleaned out Converter by
reversing the above steps.
DIGITAL METER CALIBRATION
If calibration of either digital meter is ever necessary,
meter calibration adjustment trimmers are provided on
the Weld Control PC board inside the Control Module
(see Figure 5). Calibration must be done with an
Output current load, so meters are displaying Actual
(not Preset) values. It is recommended that the cali-
bration levels be near the rating plate values, for best
accuracy, and compared to "master" meters with bet-
ter than 2% accuracy.
The accuracy of Actual AMPS meter should be within
3% of the welding amps monitored. The AMPS meter
trimmer (R561) is located near the center of the Weld
Control PC board just below the VOLTS meter trim-
mer (R562). Clockwise rotation of the trimmer adjust-
ment screw will decrease the meter reading.
The accuracy of Actual VOLTS meter should be within
3% of the welding volts monitored. The VOLTS meter
trimmer (R562) is located near the center of the Weld
Control PC board just above the AMPS meter trim-
mer (R561). Clockwise rotation of the trimmer adjust-
ment screw will decrease the meter reading. The
"master" voltmeter should be connected as close as
possible to the "ELECTRODE +" stud and "WORK-"
lead bolt, for best accuracy.
MULTI-WELD 350
SAFETY PRECAUTIONS
Have qualified personnel do the maintenance
work.
Always use the greatest care when working near
moving parts.
If a problem cannot be corrected by following the
instructions, take the machine to the nearest
Lincoln Field Service Shop.
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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.
------------------------------------------------------------------------
WARNING
MAINTENANCE
The only maintenance which may be required for the
Multi-Weld 350 is to clean out any accumulated dirt
and debris which could contaminate internal compo-
nents, or obstruct proper cooling of the power compo-
nents resulting in premature over-temperature shut-
down.
The recommended cleaning procedure is as follows:
1. Be sure to disconnect the Converterʼs input
cable to remove its input power.
2. Remove the four screws securing the rear louver
panel, and remove the panel to expose the cool-
ing tunnel heatsinks. (See Figure 4 below):
Figure 4