Lincoln Electric SVM141-A User Manual

SVM141-A

November, 1998

Safety Depends on You

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

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

And, most importantly, think
before you act and be careful.

SERVICE MANUAL

For use with machine code numbers: 10523 & 10525

Square Wave TIG 275

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• Sales and Service through Subsidiaries and Distributors Worldwide •

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World's Leader in Welding and Cutting Products Premier Manufacturer of Industrial Motors

SQUARE WAVE TIG 275

SAFETY

i i

SQUARE WAVE TIG 275

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 weld-

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

____________________________________________________

1.d. Keep all equipment safety guards, covers

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

____________________________________________________

1.e. In some cases it may be necessary to remove safety
guards to perform required maintenance. Remove
guards only when necessary and replace them when the
maintenance requiring their removal is complete.
Always use the greatest care when working near moving
parts.

___________________________________________________

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

___________________________________________________

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

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

Read and understand the following safety highlights. For additional safety information, it is strongly recommended that you
purchase a copy of “Safety in Welding & Cutting - ANSI Standard Z49.1” from the American Welding Society , P.O. Box 351040,
Miami, Florida 33135 or CSA Standard W117.2-1974. 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

Mar ‘95

ELECTRIC AND
MAGNETIC FIELDS
may be dangerous

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

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

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

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

2.d.1.

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

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

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

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

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

possible to the area being welded.

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

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

CALIFORNIA PROPOSITION 65 WARNINGS

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

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

The Above For Diesel Engines

The Above For Gasoline Engines

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SAFETY

ii ii

SQUARE WAVE TIG 275

ARC RAYS can burn.

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

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

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

ELECTRIC SHOCK can kill.

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

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

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

• Semiautomatic DC Constant Voltage (Wire) Welder.

• DC Manual (Stick) Welder.

• AC Welder with Reduced Voltage Control.

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

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

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

3.f.

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

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

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

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

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

FUMES AND GASES
can be dangerous.

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

fumes and gases away from the breathing zone. When

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

5.b.

Do not weld in locations near chlorinated hydrocarbon

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

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

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

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

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

5.e. Also see item 1.b.

Mar ‘95

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SQUARE WAVE TIG 275

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.

iii

SAFETY

iii

Mar ‘95

WELDING SPARKS can
cause fire or explosion.

6.a.

Remove fire hazards from the welding area.

If this is not possible, cover them to prevent

the welding sparks from starting a fire.

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

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

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

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

though

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

Preparation

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

(see address above).

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

6.f.

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

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

6.h. Also see item 1.c.

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SAFETY

iv iv

SQUARE WAVE TIG 275

PRÉCAUTIONS DE SÛRETÉ

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

Sûreté Pour Soudage A L’Arc

1. Protegez-vous contre la secousse électrique:

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

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

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

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

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

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

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

refroidir.

e. Ne jamais toucher simultanément les parties sous tension

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

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

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

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

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

a. Utiliser un bon masque avec un verre filtrant approprié

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

b. Porter des vêtements convenables afin de protéger la

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

c. Protéger l’autre personnel travaillant à proximité au

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

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

5. Toujours porter des lunettes de sécurité dans la zone de
soudage. Utiliser des lunettes avec écrans lateraux dans les
zones où l’on pique le laitier.

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

7. Quand on ne soud

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

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

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

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

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

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

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

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

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

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

Mar. ‘93

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MASTER TABLE OF CONTENTS FOR ALL SECTIONS

v v

SQUARE WAVE TIG 275

Page

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

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

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

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

Input Supply Connections............................................................................................................................A-4

Input Reconnect Procedure .........................................................................................................................A-5

User Supplied Connectors...........................................................................................................................A-6

Output Connections......................................................................................................................................A-6

Work Cable Connection ...............................................................................................................................A-6

TIG Torch Connection ..................................................................................................................................A-7

Twist-Mate Adapter for LA-9 and LA-17 TIG Torch ......................................................................................A-8

Twist-Mate Adapter for LW-18 and LW-20 TIG Torch...................................................................................A-8

Stick Electrode Cable Connection................................................................................................................A-9

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

Safety Precautions.......................................................................................................................................B-2

General Description......................................................................................................................................B-3

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

Design Features and Advantages................................................................................................................B-3

Welding Capability........................................................................................................................................B-4

Limitations ....................................................................................................................................................B-4

Controls and Settings ...................................................................................................................................B-5

Welding Operation........................................................................................................................................B-6

Stick Welding................................................................................................................................................B-9

Auxiliary Power.............................................................................................................................................B-9

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

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

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

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

Overload Protection .....................................................................................................................................D-2

Fan As Needed (F.A.N.) ...............................................................................................................................D-2

Service Procedures......................................................................................................................................D-2

Component Location and Access................................................................................................................D-3

Spark Gap Adjustment .................................................................................................................................D-3

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

General Description......................................................................................................................................E-2

Input Power Circuit .......................................................................................................................................E-2

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

High Voltage / High Frequency Circuit.........................................................................................................E-4

DC Welding Output ......................................................................................................................................E-5

AC Welding Output.......................................................................................................................................E-6

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

Protective Circuits ........................................................................................................................................E-8

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

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

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

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

Test Procedures..........................................................................................................................................F-18

Oscilloscope Waveforms............................................................................................................................F-33

Replacement Procedures...........................................................................................................................F-42

Retest After Repair .....................................................................................................................................F-59

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

Parts Manual .......................................................................................................................................P316 Series

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Section A-1 Section A-1

SQUARE WAVE TIG 275

TABLE OF CONTENTS

- INSTALLATION SECTION -

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

Technical Specifications, Square Wave TIG 275 (K1617-1) .......................................................A-2

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

Select Suitable Location .....................................................................................................A-3

Stacking...............................................................................................................................A-3

Lifting and Moving...............................................................................................................A-3

Tilting ...................................................................................................................................A-3

Environmental Rating ..........................................................................................................A-3

Machine Grounding and High Frequency Interference Protection .....................................A-3

Input Supply Connections ..........................................................................................................A-4

Input Reconnect Procedure........................................................................................................A-5

User Supplied Connectors .........................................................................................................A-6

Output Connections....................................................................................................................A-6

Work Cable Connection..............................................................................................................A-6

TIG Torch Connection.................................................................................................................A-7

Twist-Mate Adapter for LA-9 and LA-17 TIG Torch....................................................................A-8

Twist-Mate Adapter for LW-18 and LW-20 TIG Torch................................................................A-8

Stick Electrode Cable Connection..............................................................................................A-9

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INSTALLATION

A-2 A-2

SQUARE WAVE TIG 275

TECHNICAL SPECIFICATIONS - Square Wave TIG 275

For all Stick, DC TIG and Balanced AC TIG

Welding at 275A 40% Duty Cycle

w/o Optional K1620-1 Power Factor Capacitors

Based on the 1996 U.S. National Electrical Code

For Unbalanced AC TIG Welding above 180A,

255A 40% Duty Cycle, Maximum Penetration

w/o Optional K1620-1 Power Factor Capacitors

Based on the 1996 U.S. National Electrical Code

INPUT - SINGLE PHASE ONLY

RECOMMENDED INPUT WIRE AND FUSE SIZES

Input

Voltage /

phase/

Frequency

208/1/60
230/1/60
460/1/60
575/1/60

Input

Amperes

111
100

50
40

Type 75°C

Copper

Ground Wire in

Conduit AWG

(IEC) Sizes

6 (13.3 mm2)
6 (13.3 mm2)
10 (5.3 mm2)
10 (5.3 mm2)

Fuse

(Super Lag)

or Breaker

Size

(1)

125
125

60
50

Type 75°C

Copper Wire in

Conduit AWG

(IEC) Sizes

40°C (104°F) Ambient

4 (21.2 mm2)
4 (21.2 mm2)

8 (8.4 mm2)

10 (5.3 mm2)

Type 75°C

Copper

Ground Wire in

Conduit AWG

(IEC) Sizes

6 (13.3 mm2)
6 (13.3 mm2)

8 (8.4 mm2)

10 (5.3 mm2)

Type 75°C

Copper Wire in

Conduit AWG

(IEC) Sizes

40°C (104°F) Ambient

3 (25.0 mm2)
3 (25.0 mm2)

8 (8.4 mm2)
8 (8.4 mm2)

Input

Amperes

130
120

61
49

Height Width Depth Weight

Power 24.06 in. 19.15 in. 28.00 in. Approx. 330 lbs.
Source

611 mm 486 mm 711 mm 150 kg.

Lift Hook add 3.57” (91 mm)

Power Source 33.40 in. 27.65 in. 40.65 in. Approx. 375 lbs.

on 848 mm 702 mm 1033 mm 170 kg.

Undercarriage

PHYSICAL DIMENSIONS

Fuse

(Super Lag)

or Breaker

Size

(1)

150
150

70
60

(1)

Also called “inverse time” or “thermal/magnetic” circuit breakers; circuit breakers which have a delay in tripping action that decreases as the magnitude of cur­rent increases.

Code

Number

10523
10525

Input Current at Input Current at Input Current at Idle Current Idle Power

40% Duty Cycle 60% Duty Cycle 100% Duty Cycle

DC AC DC AC DC AC

95/86/43 130/120/61 76/69/34 106/97/50 57/52/26 82/75/38 5/4/2 900 W Max.

43/35 61/49 34/28 50/41 26/21 38/31 2/1.5 900 W Max.

Standard

Voltage

208/230/460/1/60 (K1617-1)

460/575/1/60 (K1617-2)

RATED OUTPUT & ADDITIONAL OUTPUT CAPACITY

Duty Cycle Amps Volts at Rated Amperes Current Range Auxiliary Power

40% Duty Cycle DC TIG & AC/DC Stick 275 A 31.0 V 5-315 Amps 115 Volts AC, 10 Amps
NEMA Class II (40) AC TIG 255 A 16.1 V Grounded NEMA-5-15R

Receptacle and

60% Duty Cycle DC TIG & AC/DC Stick 225 A 29.0 V MAX O.C.V

. 10 Amp Circuit Breaker

AC TIG 200 A 15.4 V AC & DC 80V

100% Duty Cycle DC TIG & AC/DC Stick 175 A 27.0 V Normal O.C.V.

AC TIG 150 A 14.8 V 72 V (AC) 59 V (DC)

Read this entire installation section before you
start installation.

SAFETY PRECAUTIONS

ELECTRIC SHOCK can kill.

• Only qualified personnel should per­form this installation.

• Turn the input power OFF at the dis­connect switch or fuse box before
working on this equipment.

• Do not touch electrically hot parts.

• Always connect the Square Wave TIG 275 grounding
screw (located on the right rear corner of the base) to
a good electrical earth ground.

• Always connect the Square Wave TIG 275 to a power
supply grounded per the National Electrical Code and
any local codes.

SELECT SUITABLE LOCATION

Place the welder where clean cooling air can freely cir­culate in through the rear louvers and out through the
side louvers. Dirt, dust or any foreign material that can
be drawn into the welder should be kept at a minimum.
Failure to observe these precautions can result in
excessive operating temperatures and nuisance trips.

STACKING

Square Wave TIG 275’s cannot be stacked.

LIFTING AND MOVING

The Square Wave TIG 275 should be lifted with a hoist.
(It weighs approximately 330 lbs./150 kg.) An optional
undercarriage is available to easily move the unit.
Refer to the Accessories section of this manual. The
Square Wave TIG 275 is designed to be used with a
K932-1 Undercarriage. Complete installation instruc­tions are included with the K932-1 Undercarriage.
When the undercarriage is properly installed, the
Square Wave TIG 275 lift bale is nonfunctional. Do not

attempt to lift the power source with the undercar­riage attached. The undercarriage is designed for

hand moving only; mechanized towing can lead to per­sonal injury and/or damage to the Square Wave TIG

275.

TILTING

Each machine must be placed on a secure, level sur­face, either directly or on a recommended undercar­riage. The machine may topple over if this procedure is
not followed.

ENVIRONMENTAL RATING

The Square Wave TIG 275 power source carries an
IP21S environmental rating. It may be used in normal
industrial and commercial environments. It is rated for
use in damp, dirty rain-sheltered environments.

MACHINE GROUNDING AND HIGH FRE­QUENCY INTERFERENCE PROTECTION

The frame of the welder must be grounded. A

ground screw marked with the symbol is located
at the right rear corner of the base for this purpose.
See your local and national electrical codes for proper
grounding methods.

The spark gap oscillator in the high frequency genera­tor, being similar to a radio transmitter, can be blamed
for many radio, TV and electronic equipment interfer­ence problems. These problems may be the result of
radiated interference. Proper grounding methods can
reduce or eliminate radiated interference.

The Square Wave TIG 275 has been field tested under
recommended installation conditions and has been
found to comply with F.C.C. allowable radiation limits.
A certificate (S14929) is being sent with each welder
for customer convenience. If he desires or is required
to obtain certification of compliance with F.C.C. RF
Energy Radiation Limits, this certificate can be used. It
is the customer's responsibility to obtain this certifica­tion. This welder has also been found to comply with
NEMA standards for high frequency stabilized power
sources.

Radiated interference can develop in the following four
ways:

1. Direct interference radiated from the welder.

2. Direct interference radiated from the welding leads.

3. Direct interference radiated from feedback into the
power lines.

4. Interference from re-radiation of “pickup” by
ungrounded metallic objects.

Keeping these contributing factors in mind, installing
equipment per the following instructions should mini­mize problems.

INSTALLATION

A-3 A-3

SQUARE WAVE TIG 275

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WARNING

1. Keep the welder power supply lines as short as
possible and enclose as much of them as possible
in rigid metallic conduit or equivalent shielding for
a distance of 50 feet (15.2m). There should be
good electrical contact between this conduit and
the welder case ground. Both ends of the conduit
should be connected to a driven ground and the
entire length should be continuous.

2. Keep the work and electrode leads as short as
possible and as close together as possible.
Lengths should not exceed 25 ft (7.6m). Tape the
leads together when practical.

3. Be sure the torch and work cable rubber coverings
are free of cuts and cracks that allow high frequen­cy leakage. Cables with high natural rubber con­tent, such as Lincoln Stable-Arc® better resist high
frequency leakage than neoprene and other syn­thetic rubber insulated cables.

4. Keep the torch in good repair and all connections
tight to reduce high frequency leakage.

5. The work piece must be connected to an earth
ground close to the work clamp, using one of the
following methods:

a) A metal underground water pipe in direct con-

tact with the earth for ten feet or more.

b) A 3/4” (19mm) galvanized pipe or a 5/8”

(16mm) solid galvanized iron, steel or copper
rod driven at least eight feet into the ground.

The ground should be securely made and the ground­ing cable should be as short as possible using cable of
the same size as the work cable, or larger. Grounding
to the building frame electrical conduit or a long pipe
system can result in re-radiation, effectively making
these members radiating antennas. (This is not recom­mended).

6. Keep all access panels and covers securely in
place.

7. All electrical conductors within 50 ft (15.2m) of the
welder should be enclosed in grounded rigid metal­lic conduit or equivalent shielding. Flexible helical­ly-wrapped metallic conduit is generally not suit­able.

8. When the welder is enclosed in a metal building,
the metal building should be connected to several
good earth driven electrical grounds (as in 5 (b)
above) around the periphery of the building.

Failure to observe these recommended installation
procedures can cause radio or TV and electronic
equipment interference problems and result in unsatis­factory welding performance resulting from lost high
frequency power.

INPUT SUPPLY CONNECTIONS

Be sure the voltage, phase, and frequency of the input
power is as specified on the rating plate, located on the
rear of the machine.

See Figure A.1 for the location of the rating plate, the
entry hole, and the reconnect panel.

FIGURE A.1

1. Input Entry 4. 220V Receptacle & Breaker

2. Rating Plate (50/60 HZ. Machines Only.)

3. 115V Receptacle & Breaker 5. Gas Input Fitting
(60 HZ. Machines only)

Remove the right case side to reveal the reconnect
panel. Welder supply line entry provision is in the case
rear panel. Entry is through a 1.4 inch (36 mm) diam­eter hole in the case back.

All connections should be made in accordance with all
local codes and national electrical codes. Installation
by a qualified electrician is recommended.

1. Connect the terminal marked (at the base of the

welder below the reconnect panel) to an earth
ground.

2. Connect the imput leads to terminals marked L1 (U)

and L2 (V) on the reconnect panel. Use a single
phase line or one phase of a two or three phase line.

INSTALLATION

A-4 A-4

SQUARE WAVE TIG 275

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1

2

5

3

4

Fuse the input circuit with the recommended super lag
fuses or delay type1circuit breakers. Choose an input
and grounding wire size according to local or national
codes or refer to the

Technical Specifications

page at
the beginning of this section. Using fuses or circuit
breakers smaller than recommended may result in
“nuisance” tripping from welder inrush currents even if
not welding at high currents.

Unbalanced AC TIG welding draws higher input cur­rents than those for Stick, DC TIG, or Balanced AC TIG
welding. The welder is designed for these higher input
currents. However, where unbalanced AC TIG welding
above 180 amps is planned, the higher input currents
require larger input wire sizes and fuses per the

Technical Specifications

page at the beginning of this

section.

1

Also called “inverse time” or “thermal/magnetic” circuit breakers, circuit
breakers which have a delay in tripping action that decreases as the magni­tude of the current increases.

INPUT RECONNECT PROCEDURE

On multiple input voltage welders, be sure the recon­nect panel is connected per the following instructions­for the voltage being supplied to the welder.

Designations on the reconnect panel, LOW, MID, and
HIGH correspond to the nameplated input voltages of
a triple voltage welder. Dual voltage welders use only
LOW and HIGH.

EXAMPLE: On a 208/230/460 volt welder, LOW is
208V, MID is 230V, and HIGH is 460V.

Make sure all connections are tight. Replace the case
side and all screws.

INSTALLATION

A-5 A-5

SQUARE WAVE TIG 275

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FIGURE A.2

RECONNECT PANEL INSTRUCTIONS FOR 208/230/460/Domestic model

460V

3 (MID)

4 (HIGH)

230V

power at the disconnect switch or fuse box before making any connections. Use
input and grounding lead sizes as specified in the operating manual. Failure to follow
instructions below can cause immediate failure of components within the welder.

Powered by high voltage which can kill. Turn off all input

5.

208V

2.

L1 (U)

4.

3.

2 (LOW)

1.

Connect the input power leads to the input terminals, L1 (U) and L2 (V), at the right
below. Connect the input power leads with the hardware provided. Completely
tighten all fasteners.

Connect a grounding lead to the ground stud located on the machine base near
the input terminals.

Welders are shipped connected for the highest rated single phase input voltage
with the lead marked "A" connected to the stud marked "4 (HIGH)".

For middle range input, reconnect the lead marked "A" to the stud marked "3 (MID)".

For low range input, reconnect the lead marked "A" to the stud marked "2 (LOW)".

SINGLE PHASE INPUT POWER SUPPLY CONNECTION INSTRUCTIONS:

SINGLE

PHASE

INPUT

L2 (V)

POWER FACTOR CAPACITORS

LEADS FOR OPTIONAL

208/230/460 DOMESTIC MODEL

WARNING:

USER SUPPLIED CONNECTORS

The Square Wave TIG 275 should be permanently
wired into the power system. No plugs or connectors
are necessary.

OUTPUT CONNECTIONS

To avoid being startled by a high frequency shock, keep
the TIG torch and cables in good condition.

ELECTRIC SHOCK can kill.

• Turn the power switch of the power
source “OFF” before installing
adapters on cable or when connecting
or disconnecting adapter plugs to
power source.

See Figure B.1 for the location of the work and elec­trode terminals, the gas and optional water solenoids,
and the Remote Receptacle.The Square Wave TIG
275 is equipped with Twist-Mate connectors for the
electrode and work connection.

WORK CABLE CONNECTION

The Twist-Mate connection allows fast and reliable
work cable attachment to the work terminal of the
Square Wave TIG 275 welding power supply.

Assemble the work cable by attaching the correct
Twist-Mate adapter and work clamp to an adequately­sized welding cable. The Twist-Mate cable plug includ­ed with the machine is designed to accept a welding
cable size of of #2 to #1. See Table A.1 and A.2 for rec­ommended sizes and corresponding hardware.

Assemble the correct Twist-Mate-adapter plug to the
work cable as follows:

1. Skin the cable jacket to 1.00 in (25.4 mm) for a #2
thru 2/0 (35 thru 70 mm2) cable. Skin the cable
jacket to 1.50 in (38.1 mm) for a 2/0 thru 3/0 (70 thru
95 mm2) cable.

2. If necessary , trim the cable end of the rubber boot to
match the diameter of the cable.

3. Slide the rubber boot onto the skinned cable end.
Use soap for lubricant if required.

4. Slide the copper tube into the brass plug. Insert
skinned cable into the copper tube.

5. Tighten set screw(s) to collapse copper tube.
Screw(s) must apply firm pressure against welding
cable.

6. Slide the rubber boot over the brass plug. The rub­ber boot must be positioned to completely cover all
electrical surfaces after the plug is locked into the
receptacle. For more details see S18737PRINT or
instructions included with the adapter kit.

INSTALLATION

A-6 A-6

SQUARE WAVE TIG 275

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WARNING

TABLE A.1

Cable Sizes for Combined Lengths of Copper

Electrode and Work Cable

Machine Size

Lengths up to

100 ft 100 to 200 ft 200 to 250 ft

275 Amp

40% Duty Cycle #1 (42.4mm2) 1/0 (53.5mm2) 2/0 (67.4mm2)

TABLE A.2

Recommended Work and Stick Electrode

Components

Twist Mate

Cable Plug

for Work

Lead

(#2 to #1)

Twist Mate
Cable Plug

for Work

Lead

(1/0 to 2/0)

Twist Mate

Cable Plug

for Work

Lead

(2/0 to 3/0)

Work

Clamp

Electrode

Holder

K852-50 K852-70 K852-95 K910-1 K909-4

SEE

WELDING CABLE

TRIM

ABOVE

BOOT

COPPER TUBE

SET SCREW
(70-95 SIZE MAY

HAVE 2 SET

BRASS PLUG

SCREWS)

TIG TORCH CONNECTION

The Twist-Mate connection allows fast and reliable TIG
torch attachment to the electrode terminal of the
Square Wave TIG 275 welding power supply. Twist­Mate TIG adapters are made of brass, combining high
electrical conductivity with mechanical strength. They
are available in several sizes and styles to accommo­date a wide selection of gas and water-cooled TIG
torches.

• For Air-Cooled TIG Torch connections refer to

TWIST-

MA TE ADAPTER for LA-9 and LA-17 TIG TORCH

section.

• For Water-Cooled TIG TORCH connections refer to

TWIST-MATE ADAPTER for LW-18 and LW-20 TIG
TORCH

Section.

Any torch having hoses and cables equipped with
Compressed Gas Association (CGA) style fittings can
be connected to an appropriate Twist-Mate adapter
(see

ACCESSORIES

section). The power source

must be switched off while making any of these
connections.

Do not operate a water-cooled torch without an ade­quate coolant supply. Set-ups using recirculated
coolant require that the cooler be switched on and run­ning. If the water solenoid valve option is used with a
cooler, the coolant does not flow until the solenoid is
actuated.

For set-ups using water as a single-pass through
coolant, install a strainer into the system upstream of
the Square Wave TIG 275 to reduce the concentration
of particles that could contaminate the system.
Otherwise, flow passages could become obstructed or
clogged, causing torch overheating or failure. The
optional water solenoid valve may also malfunction.

When the water solenoid valve option is installed into
the Square Wave TIG 275, connect the coolant supply
line from either cooler outlet or single-pass supply to
the “Water Inlet” fitting located on the machine’s case
front. Connect the TIG torch’s smaller water fitting to
the “Water Out” fitting also located on the case front. A
non-metallic coolant line is required between the elec­trode connection and the drain or cooler inlet. This
reduces the possibility of an electrical hazard.

TIG welding torches are available with 12.5 and 25 foot
cables (3.8m and 7.6m, respectively). Use the shorter
length whenever possible to reduce radio interference
problems.

CYLINDER could explode if
damaged.

• Keep cylinder upright and chained to a
support.

• Keep cylinder away from areas where it could be
damaged.

• Never allow the torch to touch the cylinder.

• Keep cylinder away from live electrical circuits.

• Maximum inlet pressure 150 psi.

The high-pressure cylinder of inert shielding gas must
be equipped with a flow regulator that limits the gas
pressure to 150 psi maximum at the machine’s gas
inlet. This brass inlet fitting is located on the rear panel
of the Square Wave TIG 275. Install a hose between
the gas flow meter and the inlet fitting.

For other conditions, consult the manufacturer’s
instructions for the water cooler or TIG torch being
used.

INSTALLATION

A-7 A-7

SQUARE WAVE TIG 275

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WARNING

INSTALLATION

A-8 A-8

SQUARE WAVE TIG 275

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TWIST-MATE ADAPTER FOR LA-9
and LA-17 TIG TORCH

The Twist-Mate connection allows fast and reliable TIG
torch connections to the electrode terminal of the
Square Wave TIG 275. The Twist-Mate adapter, strain
relief boot and retaining compound needed to connect
an LA-9 or LA-17 torch (or any equivalent air-cooled
TIG torch with a right-hand male 3/8-24 fitting) are
included with the Square Wave TIG 275.

Assemble the the LA-9 or LA-17 TIG torch to the Twist­Mate adapter as follows:

1. Slide the strain relief boot over the TIG torch’s
power cable with gas fitting.

2. Apply a small amount of retaining compound to the
fitting threads as shown. Thread the fitting to the
TIG adapter and tighten to ensure a sealed gas
connection and a good electrical connection. (35-45
in-lbs)

3. Hold the TIG adapter, with cable installed, firmly in
place by securing it into the Twist-Mate receptacle
on the power source or into a padded vise. Align
the hex in the boot with the hex on the adapter.
Firmly push the boot onto the adapter, rocking the
boot to assist installation. Use soap for lubricant if
required.

4. Examine the strain relief boot and TIG adapter for
correct assembly. The boot should nest into the
Twist-Mate receptacle on the power source. All
electrical surfaces should be completely covered
when in the Twist-Mate receptacle on the power
source. For more details see M191 15PRINTinclud­ed with the machine.

TWIST-MATE ADAPTER FOR LW-18
and LW-20 TIG TORCH

The Twist-Mate connection allows fast and reliable TIG
torch connections to the electrode terminal of the
Square Wave TIG 275. The Twist-Mate adapter and
strain relief boot needed to connect an L W-18 or LW-20
torch (or any equivalent water-cooled TIG torch with
the fittings shown in the diagrams under step 2 and 3)
are included with the Square Wave TIG 275.

Assemble the the LW-18 or LW-20 TIG torch to the
Twist-Mate adapter as follows:

1. Slide the strain relief boot over the TIG torch’s
power/water cable (large fitting) and gas hose
(small fitting without notches on hex). Also slide a
water hose into the strain relief boot as shown.

2. Thread the power/water cable (large fitting) from the
torch to the large port on the TIG adapter and tight­en to ensure a water tight connection. Next, thread
the gas hose (small fitting without notches on hex)
to the port marked “G” on the TIG adapter and tight­en to ensure a sealed gas connection. Next, thread
the water hose to cooler (or to water drain) to the
port marked “W” on the TIG adapter.

3. Check all connections made in step 2 for gas and
water leaks before proceeding.

TIG ADAPTER

TIG TORCH POWER CABLE WITH GAS FITING

RETAINING COMPOUND

STRAIN RELIEF BOOT

STRAIN RELIEF BOOT

TIG ADAPTER

WATER HOSE

GAS HOSE FROM TORCH

POWER/WATER CABLE FROM TORCH

COMPLETED ASSEMBLY

G

W

PORT (RH 5/8-18)

PORT (LH 5/8-18)

GAS CONNECTION

CONNECTION

POWER/WATER

PORT (LH 7/8-14)

WATER CONNECTION

W

G

"IN"

OR

COOLANT

OPTIONAL

WATER HOSE

"OUT"

COOLANT

FLOW

WATER SOLENOID KIT

WATER

(RH 5/8-18 MALE FITTING)

WATER HOSE FROM TORCH

GAS HOSE FROM TORCH

(SEPARATELY PROVIDED)

(SEPARATELY PROVIDED)

HOSE COUPLER

COOLANT

LW-18 OR LW-20

TIG TORCH

(SEPARATELY PROVIDED)

(LH 5/8-18 MALE FITTING)

"OUT"

"IN"

COOLANT

MAGNUM

CONNECTION DIAGRAM

POWER/WATER CABLE FROM TORCH

(LH 7/8-14 MALE FITTING)

WATER HOSE

(SEPARATELY PROVIDED)

WATER COOLER

4.

Hold the TIG adapter , with cables and hoses installed,
firmly in place by securing it into the T wist-Mate recep­tacle on the power source or into a padded vise.
Apply a thin film of lubricant to the boot’s lead in
chamfer area. Also apply lubricant to the lead in
chamfer and 2” diameter on the TIG adapter. Next
align the strain relief boot keys with the TIG adapter
slots. Now firmly push the boot onto the adapter,
rocking the boot to assist installation.

5. Examine the strain relief boot and TIG adapter for
correct assembly. The boot should nest into the
Twist-Mate receptacle on the power source. The
boot face will be 1/8 inch away from the machine
front. All electrical surfaces should be completely
covered when in the Twist-Mate receptacle on the
power source. For more details see M19116PRINT
included with the machine.

STICK ELECTRODE CABLE
CONNECTION

The Twist-Mate connection allows fast and reliable stick
electrode attachment to the electrode terminal of the
Square Wave TIG 275 welding power supply.

Assemble the electrode cable by attaching the correct
Twist-Mate adapter and electrode holder to an ade­quately-sized welding cable. See Table A.1 and A.2 for
recommended sizes and corresponding hardware.

Assemble the correct Twist-Mate adapter plug to the
stick electrode cable as detailed in

Work Cable

Connection.

DO NOT CONNECT A TIG TORCH AND STICK ELEC­TRODE CABLE AT THE SAME TIME. THEY WILL
BOTH BE ELECTRICALLY HOT WHENEVER THE
OUTPUT CONTACTOR IS ENERGIZED.

INSTALLATION

A-9 A-9

SQUARE WAVE TIG 275

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WARNING

COMPLETED ASSEMBLY

NOTES

A-10 A-10

SQUARE WAVE TIG 275

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Section B-1 Section B-1

SQUARE WAVE TIG 275

TABLE OF CONTENTS

- OPERATION SECTION -

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

Safety Precautions......................................................................................................................B-2

General Description ....................................................................................................................B-3

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

Design Features and Advantages...............................................................................................B-3

Welding Capability .....................................................................................................................B-4

Limitations...................................................................................................................................B-4

Controls and Settings.................................................................................................................B-5

Welding Operation ......................................................................................................................B-6

TIG Welding..........................................................................................................................B-6

TIG Welding Guidelines........................................................................................................B-6

TIG Welding Sequence of Operation (2-Step TIG Mode) ....................................................B-7

TIG Welding Sequence of Operation (4-Step TIG Mode) ....................................................B-7

Hand and Foot Amptrol Operation.......................................................................................B-8

Advanced TIG Welding Features ................................................................................................B-8

AC Wave Balance and Auto Balance™......................................................................................B-8

Stick Welding..............................................................................................................................B-9

Auxiliary Power ...........................................................................................................................B-9

60 Hertz Domestic Machines...............................................................................................B-9

50/60 Hertz European Machines..........................................................................................B-9

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OPERATION

B-2 B-2

SQUARE WAVE TIG 275

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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.

•

Read and follow “Electric Shock Warnings”
in the Safety section if welding must be per­formed under electrically hazardous condi­tions such as welding in wet areas or on or
in the workpiece.

FUMES AND GASES
can be dangerous.

• Keep your head out of fumes.

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

WELDING SPARKS
can cause fire or
explosion

• Keep flammable material away.

• Do not weld on containers that
have held combustibles.

ARC RAYS
can burn.

• Wear eye, ear and body
protection.

SAFETY PRECAUTIONS

Read and understand this entire section before operat­ing the machine.

Observe additional Safety Guidelines detailed in
the beginning of this manual.

WARNING

GENERAL DESCRIPTION

The Square Wave TIG 275 is a constant current, single
range square wave AC/DC TIG (GTAW) arc welding
power source with built-in high frequency stabilization.
It also has stick (SMAW) capability. A TIG Pulser Kit,
Power Factor Capacitor Kit, and a Water Solenoid Kit
are available as field installed options.

The Square Wave TIG 275 includes advanced features
such as Digital Voltage and Current Meters, Auto
Balance™, 2-Step/4-Step operation, adjustable Down
slope Time control and Fan as Needed. It also features
Twist Mate connections for the electrode and work
leads. In addition, fixed preflow and variable post flow
timers are included to control the shielding gas, as well
as the water flow when using the optional water sole­noid.

RECOMMENDED PROCESSES AND
EQUIPMENT

The Square Wave TIG 275 is recommended for the
TIG (GTAW) and stick (SMAW) welding processes
within its output capacity of 5 to 315 amps, on both AC
and DC polarity. It is compatible with all Magnum TIG
accessories, as well as many industry standard items,
such as TIG torches, hoses, and water coolers.

DESIGN FEATURES AND
ADVANTAGES

• Meets NEMA CLASS II (40) and IP21S environmen­tal certification. (Will be CSA NRTL/C certified in the
future.) Domestic and Canadian Models Only.

• Meets IEC-974-1 and IP21S environmental certifica­tion. (Will be CE certified in the future.) European
Model Only.

• Built in Digital Ammeter and Voltmeter for precise
process control. This includes a persistence feature
which captures and continues to display the peak
welding current and it’s corresponding voltage for five
seconds after the weld is completed.

• AC Wave Balance control knob provides flexibility to
the customer. Set it to the Auto Balance position and
the circuitry automatically provides the proper amount
of cleaning and penetration for normal AC TIG weld­ing. For special applications simply dial in the amount
of cleaning and penetration needed.

• Fan As Needed (FAN) circuit turns ‘ON’ the fan only
when cooling is needed. FAN minimizes the amount
of dust, dirt, and other foreign material drawn into the

machine. A build up of these materials can cause
excessive operating temperatures and nuisance shut
downs.

• 2-STEP/4-STEP TIG/STICK mode control switch. 4­STEP mode requires the use of an optional Arc Start
Switch. This welding mode reduces fatigue by elimi­nating the need to manually control the weld current
during the weld.

• Down Slope Time control is active in 4-STEP TIG
mode. It controls the amount of time (approximately
1 to 10 seconds) it takes the weld current to ramp
down from the Preset level to 25% ±10% of that level.

• Post Flow Time control is active in the 2 and 4-STEP
TIG modes. It controls the amount of time (approxi­mately 5 to 50 seconds) the shielding gas flows after
the weld is completed.

• Robotic Interface connection on the PC board can be
connected to the machines Remote Receptacle for
automated welding procedures. This interface allows
remote control of the trigger and output current of the
machine as well as providing a signal when the weld
is established. (For details contact the Lincoln Automation Center)

• Built in High Frequency Generator automatically per­forms in the correct mode. If the machine is in STICK
mode, the HF stays ‘OFF’. IF the machine is in DC
TIG mode, the HF comes ‘ON’ and stays on until the
arc is established. IF the machine is in AC TIG mode,
the HF comes ‘ON’ and stays on continuously to sta­bilize the arc.

• Automatic Local/Remote current selection. The
machine automatically senses if an Amptrol, Arc Start
Switch or TIG Pulser is plugged in and transfers cur­rent control from local to remote.

• Built in preflow time of 0.5 seconds. Preflow time is
eliminated if welding restarts during the pervious
weld’s post flow. This avoids unnecessary delays
when making repeated welds.

• Simple dial and switch design provides the customer
with flexible control of the welding process without
unnecessary complication. Controls which are not
needed in the weld mode selected are automatically
locked out.

• Twist Mate connectors are provided for the electrode
and work connections. This style connector makes
the gas and current connections for the TIG torch at
the same time. (Adaptor plugs are provided)

• DC+/AC/DC- Polarity Switch allows the welder to
change polarity without reconnecting leads.

OPERATION

B-3 B-3

SQUARE WAVE TIG 275

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OPERATION

B-4 B-4

SQUARE WAVE TIG 275

• Provides excellent arc starting and stability through­out the machines wide current range (5 to 315 Amps)
to handle the vast majority of TIG welding applica­tions.

• Simple output current dial allows the user to preset
the peak current within the full output range of the
machine.

• Highly resistant to AC arc rectification.

• Thermostatically protected to prevent equipment
damage.

• No tungsten spitting within current range of electrode.

• Designed to make maintenance and servicing easy.

• 115 Volt Receptacle with 10 Amp Circuit Breaker.
Domestic and Canadian Models Only.

• 220 Volt European (Schuko) type Receptacle with 2
Amp Circuit Breaker. European Model Only.

• Low Voltage Trigger Circuit (18 VAC) for maximum
operator safety.

• Remote Receptacle for Amptrol or Arc Start Switch
connection.

• Gas Valve Inlet fitting conforms to Compressed Gas
Association (CGA) standards.

WELDING CAPABILITY

The Square Wave TIG 275 is rated at 275 amps, 31
volts, at 40% duty cycle on a ten minute basis for DC
TIG and AC/DC stick processes. It is capable of high­er duty cycles at lower output currents. If the duty
cycle(s) are exceeded, the thermostatic protection will
shut off the output until the machine cools to a normal
operating temperature.

LIMITATIONS

The Square Wave TIG 275 is not recommended for AC
TIG welding when high concentrations of helium gas
are used for shielding. This causes starting and arc
rectification problems. Also the Square Wave 275 is
not recommended for arc gouging due to it's limited
output capacity. The Square Wave TIG 275 is also not
recommended for pipe thawing.

OPERATION

B-5 B-5

SQUARE WAVE TIG 275

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1. Current Control - This knob is used to set the
welding current from 5 to 315 amps. Read the
complete Operating Instructions section for more
information on Local and Remote setting of cur­rent.

2. AC Wave Balance Control - This knob is active in
the AC TIG mode only. It is used to set the amount
of cleaning and/or penetration produced during an
AC TIG weld. Auto Balance™ automatically sets
the AC Wave balance according to the welding cur­rent. If manual adjustment is desired, the balance
can be adjusted from +0 (maximum cleaning)
to +10 (maximum penetration). Read the
Advanced Features section for a complete expla­nation of the AC Wave Balance.

3. Post Flow Time Control - This knob is active in
the TIG mode only. It adjusts the post flow time
from 5 to 50 seconds for shielding gas. It also
adjusts cooling water flow when the optional
K1621-1 Water Solenoid Kit is used.

4. Down Slope Time Control - This knob is active in
4-Step TIG mode only. It adjusts the time (from 0.5
to 10 seconds) the welding output takes to ramp
down from the preset level to 25% of that level.

5. 2-Step/4-Step TIG/Stick Mode Control Switch -
This switch selects the welding mode desired: TIG
2-Step, TIG 4-Step, or Stick. Read the complete
Operating Instructions section for more information
on TIG 2-Step and TIG 4-Step.

6. Trimmer Potentiometers - Allows the meters to be

calibrated in the field.

7. Digital Ammeter - The ammeter displays actual

welding current during a weld cycle and displays the
peak current for approximately 5 seconds after
welding is complete. Read the complete Operating
Instructions section for more information on the
Ammeter.

10

6

5

7 8

6 9

11

12

13

14

15

1

2

3

4

1. Output Control Knob

2. AC Wave Balance Knob

3. Post Flow Knob

4. Down Slope Time Knob

5. Mode Switch

6. Trimmer Potentiometer

7. Digital Ammeter

8. Digital Voltmeter

9. Thermal Protection Light

10. Power Switch

11. Polarity Switch

12. Electrode Connection (Twist-Mate Connector)

13. Work Connection (Twist-Mate Connector)

14. Remote Control Amphenol

15. Water Solenoid (Optional)

CONTROLS AND SETTINGS

All operator controls and adjustments are located on the case front of the Square Wave TIG 275. Refer to Figure
B.1 and corresponding explanations following.

FIGURE B.1 - CONTROL PANEL

8. Digital Voltmeter - This meter displays welding
voltage, as measured on the output studs of the
Square Wave TIG 275. After welding is complete,
the meter displays the welding voltage corre­sponding to the peak welding current and displays
this value for approximately 5 seconds.

9. Thermal Protection Light - A yellow light which
only lights when an over temperature situation
occurs. See the

Maintenance Section

for more

information on thermostatic protection.

10. Power Switch - Controls the input power to the
Square Wave TIG 275.

11. Polarity Switch - Selects DC+, AC or DC- welding

polarity without reconnecting leads. DO NOT
SWITCH WHILE WELDING.

12. Twist Mate Electrode and

13. Work Connections - Easy to connect electrode
and work connections. This style Electrode
Connection makes the gas and current connec­tions for the TIG torch at the same time. (Adapter
plugs are provided with the machine.)

14. Remote Receptacle - For Amptrol, Arc Start
Switch or Robotic Interface connection.

15. Optional Water Solenoid Connections - Easy to
install this optional feature which allows for water
flow control for water cooled torches.

WELDING OPERATION

TIG WELDING

Familiarize yourself with the Controls and Settings
Section before attempting operation of the Square
Wave TIG 275.

TIG WELDING GUIDELINES

TIG welding can be done in either the TIG 2-Step or
the TIG 4-Step Weld Mode. TIG 2-Step is typically
used with Hand or Foot Amptrols, with Remote Current
control. TIG 4-Step typically uses an Arc Start switch
and Local Current Control, because it provides a very
brief current upslope, and a .5 to 10 second adjustable
current downslope. TIG 4-Step also functions like a
trigger interlock, making it unnecessary to hold down
the Arc Start switch during a weld. This feature
requires that the remote control device in use must
have separate Arc Start and Output Control mecha­nisms. Read the TIG Welding Sequence of Operation
sections for more details on 2-Step and 4-Step opera­tion.

Recommended tungsten electrode sizes, stickouts,
currents, cup or nozzle sizes are shown in Table B.1.
SINCE WELDING APPLICATIONS CAN VARY, THIS
CHART IS INTENDED AS A GUIDE ONLY.

OPERATION

B-6 B-6

SQUARE WAVE TIG 275

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(1) When used with argon gas. The current ranges shown must be reduced when using argon/helium or

pure helium shielding gasses.

(2) Tungsten electrodes are classified as follows by the American Welding Society (AWS):

Pure . . . . . . . . . . . . . . . EWP

1% Thoriated . . . . . . . . EWTh-1

2% Thoriated . . . . . . . . EWTh-2

Though not yet recognized by the AWS, Ceriated Tungsten is now widely accepted as a substitute for
2% Thoriated Tungsten in AC and DC applications.

(3) DCEP is not commonly used in these sizes.

(4) TIG torch nozzle “sizes” are in multiples of 1/16ths of an inch:

#4 = 1/4 in. (6 mm)
#5 = 5/16 in. (8 mm)
#6 = 3/8 in. (10 mm)
#7 = 7/16 in. (11 mm)
#8 = 1/2 in. (12.5 mm)

#10 = 5/8 in. (16 mm)

(5)

TIG torch nozzles are typically made from alumina ceramic. Special applications may require lava nozzles,
which are less prone to breakage, but cannot withstand high temperatures and high duty cycles.

TABLE B.1 TYPICAL CURRENT RANGES FOR TUNGSTEN ELECTRODES

(2)

.010 (.25)

0.020 (.50)

0.040 (1.0)
1/16 (1.6)
3/32 (2.4)

1/8 (3.2)
5/32 (4.0)

3/16 (4.8)
1/4 (6.4)

2-15
5-20

15-80

70-150

150-250
250-400

400-500
500-750

750-1000

(3)
(3)
(3)

10-20
15-30

25-40
40-55

55-80

80-125

2-15
5-15

10-60

50-100

100-160
150-210

200-275
250-350
325-450

2-15
5-20

15-80

70-150

140-235
225-325

300-400
400-500
500-630

2-15
10-20
20-30

30-80

60-130

100-180
100-240

190-300
250-400

---

5-20

20-60

60-120

100-180
160-250

200-320
290-390
340-525

3-8 (2-4)
5-10 (3-5)
5-10 (3-5)

5-10 (3-5)
13-17 (6-8)

15-23 (7-11)

21-25 (10-12)
23-27 (11-13)

28-32 (13-15)

3-8 (2-4)
5-10 (3-5)
5-10 (3-5)

9-13 (4-6)
11-15 (5-7)

11-15 (5-7)
13-17 (6-8)

18-22 (8-10)

23-27(11-13)

#4, #5, #6

#5, #6

#6, #7, #8

#8, #10

1%, 2%
Thoriated
Tungsten

1%, 2%
Thoriated
Tungsten

Pure

Tungsten

1%, 2%

Thoriated

Tungsten

Zirconiated

Pure

Tungsten

1%, 2%
Thoriated
Tungsten

Zirconiated Aluminum

Stainless

Steel

Tungsten
Electrode
Diameter

in. (mm)

TIG Torch

Nozzle

Size

(4), (5)

DCEN (-) DCEP ( +)

Unbalanced Wave Balanced Wave

AC Approximate Argon

Gas Flow Rate
C.F.H. (1/min.)

TIG WELDING SEQUENCE OF OPERATION
(2-Step TIG Mode)

1. Connect an Arc Start Switch or an Amptrol to the
Remote Amphenol.

2. Turn the welder, gas supply and water supply (if
equipped), on. The digital ammeter/voltmeter dis­plays will illuminate when the power is on.

3. Select the 2-Step TIG Mode with the 2-Step/4-Step
TIG/Stick switch.

4. Set the maximum output current using the output
control knob.

5. Select AC or DC- electrode polarity. See Table B.2.

6. If welding with AC polarity, set the AC Wave
Balance Knob to Auto Balance™. This gives the
optimum ratio between cleaning and penetration,
automatically adjusted of the AC Wave Balance is
desired, adjust the wave balance to the desired
settings. See the Advanced Features section for
more information on setting and using the AC
Wave Balance.

7. Set the post flow time with the post flow knob. Post
flow control knob adjusts the time that the shielding
gas flows (and cooling water flow, if the optional
water solenoid is used) after the weld cycle. Use
short post flow times with low currents and small
tungstens, use long post flow times at high output
currents with large tungstens.

8. Press and release the Arc Start Switch, and set the
gas flow meter. The welder is now ready for weld­ing.

9. Position the tungsten electrode at the start of the
weld at a 65° to 75° angle with the horizontal so
that the electrode is approximately 1/8” (4 mm)
above the work piece. Press the Arc Start Switch.
This opens the gas (and optional water solenoid)
valves to automatically purge air from the hose and
torch. After a 0.5 second preflow time, the high fre­quency becomes available to strike the arc.

10. Hold the Arc Start Switch or Amptrol down until an
arc is established. If using an Amptrol, read the
Section on Hand and Foot Amptrol Operation.
Release the Arc Start Switch or Amptrol to stop the
arc and start the Post Flow timer. After the Post
Flow time has expired, the gas and (optional water
solenoid) valves will close. To make another weld,
repeats steps 9 and 10.

TIG WELDING SEQUENCE OF OPERATION
(4-Step TIG Mode)

1. Connect an Arc Start Switch to the Remote
Amphenol.

2. Turn the welder, gas supply and water supply (if so
equipped), on. The digital ammeter/voltmeter dis­play will illuminate when the power is on.

3. Select the 4-Step TIG Mode with the 2-Step/4-Step
TIG/Stick switch.

4. Set the maximum output current using the output
control knob.

5. Select AC or DC- electrode polarity. See Table B.2.

6. If welding with AC polarity, set the AC Wave
Balance Knob to Auto Balance™. This gives the
optimum ratio between cleaning and penetration,
automatically adjusted for the output current. If
manual adjustment of the AC Wave Balance is
desired, adjust the wave balance to the desired
settings. See the Advanced Features section for
more information on setting and using the AC
Wave Balance.

7. Set the Post Flow time with the Post Flow knob.
Post Flow time provides shielding gas flow (and
cooling water, if used) after the weld. Use short
Post Flow times with low currents and small tung­stens and long Post flow times at high output cur­rents and large tungstens.

8. Set the Downslope Time with the Downslope Time
Knob. This will adjust the time of the crater fill peri­od.

9. Press and release the Arc Start Switch, to set the
gas flow meter if necessary. The welder is now
ready for welding.

10. Position the tungsten electrode at the start of the
weld at a 65° to 75° angle with the horizontal so
that the electrode is approximately 1/8” (4 mm)
above the work piece. Press the Arc Start Switch.
This opens the gas and water valves to automati­cally purge air from the hose and torch. After a 0.5
second preflow time, the high frequency becomes
available to strike the arc.

OPERATION

B-7 B-7

SQUARE WAVE TIG 275

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TABLE B.2

RECOMMENDED POLARITY

SETTINGS FOR TIG WELDING

Type of Welding

Electrode

Polarity

Stainless Steel

Aluminum & Magnesium

Other Metals

DC-

AC

DC-

11. Hold the Arc Start Switch down until an arc is
established. The arc will start at a low current
value that is equal to 25% of the preset current
established in Step 4. It will remain at this current
as long as the Arc Start Switch is closed. Release
the Arc Start Switch. At this point, the Square
Wave TIG 275 will quickly ramp up to the preset
maximum welding current, (0.5 seconds upslope
time) and the weld will continue indefinitely. Press
the Arc Start Switch a second time to initiate the
Downslope time. The current will go down to a
crater fill current that is equal to 25% of the weld­ing current. Release the Arc Start Switch to stop
the arc and start the Post flow timer. After the Post
flow time has expired, the gas and optional water
valves will close. To make another weld, repeat
steps 10 and 11.

HAND AND FOOT AMPTROL OPERATION

Both the Hand and Foot Amptrol work in a similar man­ner. They are meant to be used for remote current con ­trol. The TIG 2-Step mode must be selected when
using an Amptrol for remote current control.

For simplicity , the following explanation will refer only to
"Amptrols", meaning both Foot and Hand models. The
term "minimum" refers to a Foot pedal in the "up" posi­tion, as it would be with no foot pressure, or a Hand
Amptrol in the relaxed position, with no thumb pres­sure. "Maximum" refers to a fully depressed Foot
Amptrol, or a fully extended Hand Amptrol.

The Amptrol is capable of controlling the output current
from 5 amps to the preset current on the output control
knob. For example, if the preset is at 200 amps, the
Amptrol, when depressed just past its minimum posi­tion, will cause the Square Wave TIG 275 to weld at 5
amps. At the Amptrol's maximum position, the output
will be near 200 amps.

It is important to note that, for many applications, the
tungsten will not start an arc at only 5 amps. (Refer to
the TIG Welding Guidelines for recommended tungsten
currents.) T o start an arc reliably, it is important to
depress the Amptrol far enough so that the machine
output current is near the tungsten operating range. In
the example above, a 3/32" tungsten may be used on
DC- to weld near 200 amps. To start the weld, the
operator may have to depress the Amptrol approxi­mately 1/4 of the way down, or to nearly 50 amps, in
order to start the arc. Merely depressing the Amptrol to
its 5 amp minimum position will not start the arc.

ADVANCED TIG WELDING FEATURES

AC WAVE BALANCE AND AUTO BALANCE™

The AC Wave Balance feature is unique to the Square
Wave TIG 275. It is active only in AC TIG mode. It con­trols the amount of positive and negative current in the
AC output.

The Square Wave TIG 275 allows the operator to
select Auto Balance™. This selection provides auto­matic adjustment of the AC Wave Balance; it is suitable
for most welding conditions. Auto Balance™ gives the
ideal amount of cleaning and penetration, based on the
welding current output.

Manual adjustment of the AC Wave Balance is also
possible. Manual Balance settings vary from 0 (maxi­mum cleaning) to 10 (maximum penetration). Asetting
of 3 yields a balanced output (equal amounts of clean­ing and penetration). Use the following as a guide
when setting the Balance manually:

BALANCED (3): The amounts of positive and negative

are the same.

CLEANING (0 to 2): Provides more positive current

than negative current. Since the positive cur­rent produces the "cleaning" or oxide removal
on aluminum, this setting is used for welding on
heavily oxidized aluminum.

PENETRATION (4 to 10): Provides more negative cur-

rent than positive. The arc plasma will be more
concentrated and more easily directed to where
the heat is needed. Higher penetration settings
allow a given size of tungsten to carry more cur­rent.

CAUTION: Use only the amount of cleaning required
because the greater amount of positive current will
heat the tungsten more and possibly cause it to melt or
"spit". Also, the arc is usually more flared and less sta­ble with more cleaning current.

In general, use just enough "cleaning" to remove
oxides and to give good wetting of the puddle.

OPERATION

B-8 B-8

SQUARE WAVE TIG 275

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STICK WELDING

1. Turn the welder “on”. The digital ammeter/volt-

meter will illuminate when the power is on.

2. Set the Mode Switch to “STICK”. Set the output

current using the Output Control Knob. No other
functions or adjustments operate in the Stick
Mode.

3. Select the desired DC+/AC/DC- electrode polarity.

4. Clamp the electrode in the electrode holder, start

the weld by lightly touching the electrode to the
work. Stop the weld by pulling the electrode away
from the work piece.

AUXILIARY POWER

60 HERTZ DOMESTIC MACHINES

The Square Wave TIG 275 machines rated for 60 Hz
operation provides 10 amps of 115 volt AC power at a
standard NEMA5-15R receptacle, located on the lower
case back of the machine. This circuit is protected
from shorts and overloading by a 10 amp circuit break­er, located next to the receptacle. The auxiliary circuit
is intended for running water coolers and small power
tools, whose current draw is within the 10 amp rating.
Note that some types of equipment, especially pumps
and large motors, have starting currents which are sig­nificantly higher than their running current. These high­er starting currents may cause the circuit breaker to
open. If this situation occurs, the user should refrain
from using the Square Wave TIG 275 auxiliary for that
equipment.

50/60 HERTZ EUROPEAN MACHINES

The Square Wave TIG 275 machines rated for 50/60Hz
operation provides 2 amps of 220 volt AC power at a
continental European (Schuko) type receptacle, locat­ed on the lower case back of the machine. This circuit
is protected from shorts and overloading by a 2 amp
circuit breaker, located above the receptacle. The aux­iliary circuit is intended for running water coolers whose
current draw is within the 2 amp rating of the recepta­cle. Note that some types of equipment, especially
pumps and motors, have starting currents which are
significantly higher than their running currents. These
higher starting currents may cause the circuit breaker
to open. If this situation occurs, the user should refrain
from using the Square Wave TIG 275 auxiliary for that
equipment.

OPERATION

B-9 B-9

SQUARE WAVE TIG 275

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NOTES

B-10 B-10

SQUARE WAVE TIG 275

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TABLE OF CONTENTS

- ACCESSORIES -

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

Accessories Included with Machine ............................................................................................C-2

Optional Accessories ..................................................................................................................C-2

Section C-1 Section C-1

SQUARE WAVE TIG 275

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ACCESSORIES INCLUDED WITH
MACHINE

K852-50 - Twist Mate Cable Plug for #2 to #1 Work

Lead.

K1622-1 - Twist Mate Adapter Kit for LA9 and LA17

Torches.

K1622-2 - Twist Mate Adapter Kit for LW18 and LW20

Torches.

OPTIONAL ACCESSORIES

Any necessary installation instructions are included for
the following accessories:

K963-1, -2 - Hand Amptrol
K870 - Foot Amptrol
K814 - Arc Start Switch
K559-2 - Magnum®Cooler Mounting Bracket
K932-1 - Undercarriage
K1619-1 - TIG Pulser Kit
K1620-1 - Power Factor Capacitor Kit
K1621-1 - Water Solenoid Kit
K1622-3 - Twist Mate Adapter Kit for LA26 Torch
K852-70 - Twist Mate Cable Plug for 1/0 to 2/0 Work

Lead

K852-95 - Twist Mate Cable Plug for 2/0 to 3/0 Work

Lead

K932-1 Undercarriage. When the undercarriage is
properly installed, the Square Wave TIG 275 lift bail is
nonfunctional. Do not attempt to lift the power source
with the undercarriage attached. THe undercarriage is
desinged for hand moving only; mechanized towing
can lead to personal injury and/or damage to the
Square Wave TIG 275.

K1622-1 Twist-Mate Adapter Kit for LA9 & LA17
Torches (Included with machine)

K1622-2 Twist Mate Adapter Kit for LW18 & LW20
Torches (Included with machine)

K852-50 Twist-Mate Cable Plug for #2 to #1 Work Lead
(Included with machine)

ACCESSORIES

C-2 C-2

SQUARE WAVE TIG 275

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Section D-1 Section D-1

SQUARE WAVE TIG 275

TABLE OF CONTENTS

- MAINTENANCE SECTION -

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

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

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

Overload Protection....................................................................................................................D-2

Fan As Needed (F.A.N.)..............................................................................................................D-2

Service Procedures.....................................................................................................................D-2

Component Location and Access...............................................................................................D-3

Control PC Board.................................................................................................................D-3

Display PC Board, Arc Starter/Bypass PC Board................................................................D-3

Spark Gap Assembly, High Voltage Transformer.................................................................D-3

Main Rectifier........................................................................................................................D-3

Spark Gap Adjustment................................................................................................................D-3

SAFETY PRECAUTIONS

ELECTRIC SHOCK can kill.

• Only qualified personnel should per­form this maintenance.

• Turn the input power OFF at the dis­connect switch or fuse box before
working on this equipment.

• Do not touch electrically hot parts.

To avoid receiving a high frequency shock, keep the
TIG torch and cables in good condition.

ROUTINE AND PERIODIC
MAINTENANCE

Very little routine maintenance is necessary to keep
your Square Wave TIG 275 running in top condition.
No specific schedule can be set for performing the fol­lowing items; factors such as hours of usage and
machine environment should be considered when
establishing a maintenance schedule.

1. Periodically blow out dust and dirt which may accu­mulate within the welder using an air stream.

2. Inspect welder output and control cables for fray­ing, cuts, and bare spots.

3. Inspect the spark gap at regular intervals to main­tain the recommended spacing. See the Service
Procedures Section for complete information on
spark gap settings.

4. The fan motor has sealed ball bearings which
require no maintenance.

OVERLOAD PROTECTION

This welder has thermostatic protection from excessive
duty cycles, overloads, loss of cooling, and high ambi­ent temperatures. When the welder is subjected to an
overload or loss of cooling, a thermostat will open.
This condition will be indicated by the illumination of
the yellow Thermostatic Protection Light on the case
front . The fan will continue to run to cool the power
source. No welding is possible until the machine is
allowed to cool and the Thermostatic Protection Light
goes out.

FAN AS NEEDED (F.A.N.)

The Square Wave TIG 275 has the F.A.N. circuit fea­ture, which means the cooling fan will operate only
while welding, then for about 6 minutes after welding
has stopped. The cooling fan will operate conintuous­ly if the yellow Thermstatic Protection Light in “ON.”

SERVICE PROCEDURES

Use extreme caution when working with the secondary
circuit of the high frequency transformer. Turn the input
power off using the disconnect switch or fuse box
before working inside the machine. This is particularly
important when working on the secondary circuit of the
high voltage transformer (T3) because the output volt­age is dangerously high.

DO NOT APPLY POWER TO THE SQUARE WAVE
TIG 275 WITH THE SIDES AND ROOF REMOVED.

The case front and case back assemblies tend to lean
in towards the center assembly; there is a danger of a
short circuit when this occurs. If you must troubleshoot
the machine with power applied, do so with the roof in
place, and check for shorts before applying power.

Operation of the Square Wave TIG 275 should be trou­ble-free for the life of the machine. Should a malfunc­tion occur, however, the following procedures will be
useful to trained service personnel with experience in
repairing arc welding equipment.

MAINTENANCE

D-2 D-2

SQUARE WAVE TIG 275

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WARNING

WARNING

WARNING

COMPONENT LOCATION AND
ACCESS

CONTROL PC BOARD

Remove the left case side. Use a 3/8" Nut Driver or
other suitable tool.

NOTE: The Case side can be removed while roof is in
place, as long as the three screws which secure the
roof to the case side are removed. The PC Board is
mounted on left divider assembly and can be removed
with a phillips head screwdriver.

DISPLAY PC BOARD, ARC
STARTER/BYPASS PC BOARD

Remove the roof and both case sides. Use a 3/8" Nut
Driver or other suitable tool. These PC Boards are
located on the inside case front of the machine.

SPARK GAP ASSEMBLY, HIGH VOLTAGE
TRANSFORMER

Remove the right case side. Use a 3/8" Nut Driver or
other suitable tool. The high voltage transformer is
mounted to the base. The spark gap assembly is locat­ed on the inside case front.

MAIN RECTIFIER

Remove the roof and both case sides. Next, remove
the case back assembly . Use a 3/8" Nut Driver or other
suitable tool. The main rectifier is mounted to the main
transformer, in front of the cooling fan.

SPARK GAP ADJUSTMENT

The spark gap is set at the factory to a gap of 0.015
inches (0.4 mm). This setting is adequate for most
applications. Where less high frequency is desired, the
setting can be reduced to 0.008 inches (0.2 mm).

To adjust the spark, first be sure that the input power to
the machine is ‘OFF’ AT THE DISCONNECT SWITCH
OR FUSE BOX. The high voltages developed in the
high frequency circuit can be lethal. Next, remove the
right case side. Use a 3/8" Nut Driver or other suitable
tool. Check the spark gap spacing with a feeler gauge.
If adjustment is required, pull off one of the two leads
going to the aluminum spark gap blocks. Adjust the
gap by loosening the Allen head screw, reset the gap
and tightening the screw in the new position. Reattach
the lead removed earlier, and reinstall the case side.

MAINTENANCE

D-3 D-3

SQUARE WAVE TIG 275

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FIGURE D.1 SPARK GAP

.015 Spark Gap

RIGHT SIDE VIEW OF MACHINE

MAINTENANCE

D-4 D-4

SQUARE WAVE TIG 275

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4

3

5

12

11

2

1

9

8

13

10

7

6

SQUARE WAVETIG 275

FIGURE D.2 - MAJOR COMPONENT LOCATIONS

1. CASE FRONT (WITH DISPLAY BOARD)

2. INTERNAL DIVIDER
(WITH CONTROL BOARD)

3. CASE SIDES

4. CASE TOP

5. CASE BACK

6. FAN MOTOR ASSEMBLY

7. RECONNECT PANEL

8. BASE

9. HIGH VOLTAGE TRANSFORMER

10. MAIN TRANSFORMER

11. CHOKE

12. OUTPUT RECTIFIER BRIDGE

13. HIGH FREQUENCY UNIT
(SPARK GAPASSEMBLY)

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Section E-1 Section E-1

SQUARE WAVE TIG 275

TABLE OF CONTENTS

- THEORY OF OPERATION SECTION -

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

General Description ....................................................................................................................E-2

Input Power Circuit......................................................................................................................E-2

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

High Voltage/High Frequency Circuit ..........................................................................................E-4

DC Welding Output.....................................................................................................................E-5

AC Welding Output .....................................................................................................................E-6

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

Protective Circuits.......................................................................................................................E-8

Thermal Protection ...............................................................................................................E-8

Overload Protection..............................................................................................................E-8

INPUT
POWER
SWITCH

MAIN

TRANSFORMER

POLARITY

SWITCH

SCR

BRIDGE

X1

X2

AC

AC

DC+

DC-

CONTROL

BOARD

18VAC

18VAC

115VAC

FAN

REMOTE

RECEPTACLE

H1

H2
H3

SHUNT

115VAC

HIGH VOLTAGE

TRANSFORMER

CIRCUIT

BY-PASS

BOARD

HI-FREQUENCY
TRANSFORMER

C
H
O
K
E

WORK

ELECTRODE

THERMAL

LIGHT

GAS
VALVE

OUTPUT
CONTROL

MODE

SWITCH

F
E
E
D
B
A
C
K

H4

"A"

RECONNECT

PANEL

23VAC

DOWNSLOPE

CONTROL

POSTFLOW
CONTROL

BALANCE
CONTROL

THERMOSTATS

115VAC

RECEPTACLE

FIGURE E.1 - SQUARE WAVE TIG 275 BLOCK LOGIC DIAGRAM

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GENERAL DESCRIPTION

The Square Wave TIG 275 machine is a constant cur­rent, single range square wave AC/DC TIG (GTAW) arc
welding power source with built-in high frequency sta­bilization. It also has stick welding (SMAW) capability.
The machine includes advanced features such as
Digital Voltage and Current Meters, Auto Balance, 2­Step/4-Step operation, adjustable Downslope Time
Control and Fan as Needed. The Square Wave TIG
275 is recommended for the TIG (GTAW) and stick
(SMAW) welding processes within its output capacity of
5 to 315 amps, on both AC and DC polarities.

INPUT POWER CIRCUIT

The desired single-phase input power is connected to
the TIG 275 through the reconnect panel to the input
power switch located in the front panel of the machine.
The machine can be configured for any one of three
input voltages (208 V AC, 230 VAC or 460 VAC) by con­necting the “A” lead to the appropriate terminal on

the reconnect panel. When the input power switch is
turned “on,” the input voltage is applied directly to the
primary winding of the main transformer.

The main transformer changes the high voltage, low
current input power to a low voltage, high current out­put available at the main secondary winding (X1 and
X2). This 78 VAC winding supplies power to the weld­ing arc. In addition, four auxiliary windings are incor­porated in the main transformer. The 115 VAC winding
supplies power to the 115 VAC receptacle. Through
the control board, it also powers the gas solenoid, the
high voltage transformer, and the cooling fan. The
cooling fan is activated only when welding current is
sensed. The 23 VAC winding provides power for the
DC background current. This circuit is active in the DC
welding mode. Two 18 VAC windings are included in
the main transformer assembly. One 18 VAC winding
is rectified on the control board and is used in the trig­ger circuitry. The other 18 VAC winding is used by the
control board for phase detection. This voltage is also
rectified and regulated to +15 VDC and +5 VDC power
supplies that operate the circuitry on the control board.

THEORY OF OPERATION

E-2 E-2

SQUARE WAVE TIG 275

FIGURE E.2 – MAIN TRANSFORMER AND INPUT POWER

NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

INPUT

POWER
SWITCH

MAIN

TRANSFORMER

POLARITY

SWITCH

SCR

BRIDGE

X1

X2

AC

AC

DC+

DC-

CONTROL

BOARD

18VAC

18VAC

115VAC

FAN

REMOTE

RECEPTACLE

H1

H2
H3

SHUNT

115VAC

HIGH VOLTAGE
TRANSFORMER

CIRCUIT

BY-PASS

BOARD

HI-FREQUENCY
TRANSFORMER

C
H
O
K
E

WORK

ELECTRODE

THERMAL

LIGHT

GAS
VALVE

OUTPUT
CONTROL

MODE

SWITCH

F
E
E
D
B
A
C
K

H4

"A"

RECONNECT

PANEL

23VAC

DOWNSLOPE

CONTROL

POSTFLOW
CONTROL

BALANCE
CONTROL

THERMOSTATS

115VAC

RECEPTACLE

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OUTPUT RECTIFICATION,
CONTROL BOARD AND FEEDBACK

The AC output from the main transformer secondary is
rectified and controlled through the SCR bridge.
Output current is sensed at the shunt as a low voltage
signal and fed back to the control board. The control
board senses the status and settings of the various
operator controls such as the mode switch, the output
control, the remote control receptacle, the downslope
control, the balance control and the postflow control.
Circuitry on the control board evaluates these com­mands, compares them to the feedback information
received from the shunt and sends the appropriate gate
firing signals to the output SCR bridge. The control
board regulates the firings of the output SCRs, which
control the output of the machine. See

SCR

Operation.

The control board also monitors the ther­mostats and controls the gas solenoid, the thermal light
and the cooling fan.

THEORY OF OPERATION

E-3 E-3

SQUARE WAVE TIG 275

FIGURE E.3 – OUTPUT RECTIFICATION, CONTROL BOARD AND FEEDBACK

INPUT
POWER
SWITCH

MAIN

TRANSFORMER

POLARITY

SWITCH

SCR

BRIDGE

X1

X2

AC

AC

DC+

DC-

CONTROL

BOARD

18VAC

18VAC

115VAC

FAN

REMOTE

RECEPTACLE

H1

H2
H3

SHUNT

115VAC

HIGH VOLTAGE

TRANSFORMER

CIRCUIT

BY-PASS

BOARD

HI-FREQUENCY
TRANSFORMER

C
H
O
K
E

WORK

ELECTRODE

THERMAL

LIGHT

GAS
VALVE

OUTPUT
CONTROL

MODE

SWITCH

F
E
E
D
B
A
C
K

H4

"A"

RECONNECT

PANEL

23VAC

DOWNSLOPE

CONTROL

POSTFLOW
CONTROL

BALANCE
CONTROL

THERMOSTATS

115VAC

RECEPTACLE

THEORY OF OPERATION

E-4 E-4

SQUARE WAVE TIG 275

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HIGH VOLTAGE / HIGH FREQUENCY
CIRCUIT

The control board passes the 115 VAC voltage to the
primary of the high voltage transformer. The secondary
of the high voltage transformer is coupled to a spark
gap generator and also to the high frequency trans­former. The high frequency transformer transfers the
high frequency “spark” to the electrode terminal, which
is coupled to the TIG torch.

NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

FIGURE E.4 – HIGH VOLTAGE / HIGH FREQUENCY CIRCUIT

INPUT
POWER
SWITCH

MAIN

TRANSFORMER

POLARITY

SWITCH

SCR

BRIDGE

X1

X2

AC

AC

DC+

DC-

CONTROL

BOARD

18VAC

18VAC

115VAC

FAN

REMOTE

RECEPTACLE

H1

H2
H3

SHUNT

115VAC

HIGH VOLTAGE

TRANSFORMER

CIRCUIT

BY-PASS

BOARD

HI-FREQUENCY
TRANSFORMER

C
H
O
K
E

WORK

ELECTRODE

THERMAL

LIGHT

GAS
VALVE

OUTPUT
CONTROL

MODE

SWITCH

F
E
E
D
B
A
C
K

H4

"A"

RECONNECT

PANEL

23VAC

DOWNSLOPE

CONTROL

POSTFLOW
CONTROL

BALANCE
CONTROL

THERMOSTATS

115VAC

RECEPTACLE

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THEORY OF OPERATION

E-5 E-5

SQUARE WAVE TIG 275

FIGURE E.5 – DC WELDING OUTPUT

FIGURE E.6 – DC WELDING CURRENT GENERATION

DC WELDING OUTPUT

When the polarity switch is placed in either DC position,
the AC voltage from the main transformer secondary is
applied to the SCR bridge. The SCR bridge and choke
circuits are connected in a conventional full wave
bridge and filter configuration, resulting in a controlled
DC output. Since the choke is in series with the nega­tive leg of the bridge and also in series with the weld­ing load, a filtered DC is applied to the output terminals.
The bypass board protects the internal circuitry from
interference.

INPUT
POWER
SWITCH

MAIN

TRANSFORMER

POLARITY

SWITCH

SCR

BRIDGE

X1

X2

AC

AC

DC+

DC-

CONTROL

BOARD

18VAC

18VAC

115VAC

FAN

REMOTE

RECEPTACLE

H1

H2

H3

SHUNT

115VAC

HIGH VOLTAGE
TRANSFORMER

CIRCUIT

BY-PASS

BOARD

HI-FREQUENCY
TRANSFORMER

C
H
O
K
E

WORK

ELECTRODE

THERMAL

LIGHT

GAS
VALVE

OUTPUT
CONTROL

MODE

SWITCH

F
E
E

D

B

A

C

K

H4

"A"

RECONNECT

PANEL

23VAC

DOWNSLOPE

CONTROL

POSTFLOW
CONTROL

BALANCE
CONTROL

THERMOSTATS

115VAC

RECEPTACLE

CHOKE

ELECTRODE

DC

WORK

PRIMARY

1Ø

AC WELDING OUTPUT

Rotating the polarity switch to the AC position changes
the welding power circuit. One lead (X1) of the main
transformer secondary is connected to the machine’s
output work terminal. The other secondary lead (X2) is
connected to one of the AC connections of the SCR
bridge. The electrode terminal is connected to the
other AC side of the bridge. The choke is now electri­cally across the negative and positive SCR bridge con­nections. With the ability of the choke to store energy
and the SCRs to turn on at the appropriate times, an
AC square wave is developed and applied to the out­put terminals.

THEORY OF OPERATION

E-6 E-6

SQUARE WAVE TIG 275

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FIGURE E.7 – AC WELDING OUTPUT

FIGURE E.8 – AC SQUARE WAVE WELDING CURRENT GENERATION

INPUT
POWER
SWITCH

MAIN

TRANSFORMER

POLARITY

SWITCH

SCR

BRIDGE

X1

X2

AC

AC

DC+

DC-

CONTROL

BOARD

18VAC

18VAC

115VAC

FAN

REMOTE

RECEPTACLE

H1

H2
H3

SHUNT

115VAC

HIGH VOLTAGE
TRANSFORMER

CIRCUIT

BY-PASS

BOARD

HI-FREQUENCY
TRANSFORMER

C
H
O
K
E

WORK

ELECTRODE

THERMAL

LIGHT

GAS
VALVE

OUTPUT
CONTROL

MODE

SWITCH

F
E
E
D
B
A
C
K

H4

"A"

RECONNECT

PANEL

23VAC

DOWNSLOPE

CONTROL

POSTFLOW
CONTROL

BALANCE
CONTROL

THERMOSTATS

115VAC

RECEPTACLE

CHOKE

DC

WORK

PRIMARY

1Ø

ELECTRODE

SCR OPERATION

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

When an AC supply voltage is applied to the SCR, the
device spends a certain portion of the AC cycle time in
the on state and the remainder of the time in the off
state. The amount of time spent in the ON state is con­trolled by the gate.

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

THEORY OF OPERATION

E-7 E-7

SQUARE WAVE TIG 275

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FIGURE E.9 – SCR OPERATION

ANODE

CATHODE

OUTPUT

GATE

GATE

INPUT

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

PROTECTIVE CIRCUITS

Protective circuits are designed into the Square Wave
TIG 275 to sense trouble and shut down the machine
before the trouble damages the internal machine com­ponents. Both thermal protection and current overload
are included.

THERMAL PROTECTION

Thermostats protect the machine from excessive oper­ating temperatures. Excessive operating temperatures
may be caused by a lack of cooling air or by operating
the machine beyond the duty cycle and output rating.
If excessive operating temperature should occur, caus­ing a thermostat to open, the Thermal Light will illumi­nate, the fan will continue to run and welding output will
be disabled. Once the machine cools sufficiently, the
thermostats are self-resetting. If the shutdown is
caused by excessive output or duty cycle and the fan
is operating normally, the power may be left on and the
reset should occur within a 15 minute period. If the fan
is not functioning properly or the air intake louvers are
obstructed, the input power must be removed and the
fan problem or air obstruction corrected.

OVERLOAD PROTECTION

The machine is electronically protected from producing
excessively high output currents. The output is limited
to 350 amps.

THEORY OF OPERATION

E-8 E-8

SQUARE WAVE TIG 275

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Section F-1 Section F-1

SQUARE WAVE TIG 275

TABLE OF CONTENTS

- TROUBLESHOOTING & REPAIR SECTION -

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

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

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

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

Test Procedures

High Frequency Circuit Disable Procedure ........................................................................F-18

T1 Main Transformer Test...................................................................................................F-20

Gas (Water) Solenoid Test..................................................................................................F-24

Static SCR Test...................................................................................................................F-26

Active SCR Test ..................................................................................................................F-29

Oscilloscope Waveforms

Normal Open Circuit Voltage Waveform—AC TIG Mode...................................................F-33

Normal Open Circuit Voltage Waveform—DC TIG Mode ...................................................F-34

Normal Open Circuit Voltage Waveform—AC Stick Mode.................................................F-35

Normal Open Circuit Voltage Waveform—DC Stick Mode.................................................F-36

Typical Output Voltage Waveform—Machine Loaded—AC TIG Mode..............................F-37

Typical Output Voltage Waveform—Machine Loaded—DC TIG Mode..............................F-38

Typical Output Voltage Waveform—Machine Loaded—AC Stick Mode.............................F-39

Typical Output Voltage Waveform—Machine Loaded—DC Stick Mode............................F-40

Abnormal Open Circuit Voltage—DC TIG Mode—One Output SCR Not Functioning.......F-41

Replacement Procedures

High Voltage Transformer Removal and Replacement ......................................................F-42

SCR Bridge Assembly Removal and Replacement............................................................F-45

Polarity Switch Removal and Replacement........................................................................F-49

Main Transformer and Output Choke Assembly Removal and Replacement....................F-54

Retest After Repair....................................................................................................................F-59

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HOW TO USE TROUBLESHOOTING GUIDE

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

TROUBLESHOOTING & REPAIR

F-2 F-2

SQUARE WAVE TIG 275

CAUTION

WARNING

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

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

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

Step 3. RECOMMENDED COURSE OF ACTION.

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

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

WARNING

If for any reason you do not understand the test procedures or are unable to perform the test/repairs
safely, contact the Lincoln Electric Service Department for electrical troubleshooting assistance before
you proceed. Call 216-383-2531 or 1-800-833-9353.

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and wave form checks with high frequency circuit OFF. Perform High Frequency

Disable Procedure.

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ELECTRIC SHOCK can kill.

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

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

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

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

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

PC Board can be damaged by static electricity.

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

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

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

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

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

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

4. Test the machine to determine if the failure symp-

tom has been corrected by the replacement PC
board.

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

NOTE: Allow the machine to heat up so that all electri­cal components can reach their operating temperature.

5. Remove the replacement PC board and substitute

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

a. If the original problem does not reappear

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

b. If the original problem is recreated by the

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

6. Always indicate that this procedure was followed

when warranty reports are to be submitted.

NOTE: Following this procedure and writing on the
warranty report, “INSTALLED AND SWITCHED PC
BOARDS TO VERIFY PROBLEM,” will help avoid
denial of legitimate PC board warranty claims.

TROUBLESHOOTING & REPAIR

F-3 F-3

SQUARE WAVE TIG 275

PC BOARD TROUBLESHOOTING PROCEDURES

WARNING

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

Reusable
Container
Do Not Destroy

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TROUBLESHOOTING & REPAIR

F-4 F-4

SQUARE WAVE TIG 275

Observe Safety Guidelines TROUBLESHOOTING GUIDE
detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

OUTPUT PROBLEMS

The machine is dead. No weld out­put - no 115 VAC at the receptacle.
(220 VAC receptacle on European
models only).

1. Check the input voltage. The
input voltage must match the
rating plate and the voltage con­nection. Refer to

Reconnect

Procedure

in the Installation

section of this manual.

2. Make sure the input power
switch is in the “ON” position.

3. Check for blown or missing
fuses in the input lines.

1. Check the input power switch,
reconnect panel and associated
wires for loose or faulty connec­tions.

2. The input power switch may be
faulty.

3. Perform the

T1 Transformer

Test.

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TROUBLESHOOTING & REPAIR

F-5 F-5

SQUARE WAVE TIG 275

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 216­383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

OUTPUT PROBLEMS

No welding output. The 115 VAC is
present at the receptacle. (220
VAC receptacle on European mod­els only).

1. Make sure the polarity switch is
in the proper position and func­tioning correctly.

2. One of the thermostats may be
tripped. Allow the machine to
cool. The thermal light will be
on.

3. Make sure the welding cables,
torch and connections are in
good operating condition.

1. Check for loose or faulty con­nections on the heavy current
carrying leads. (Polarity switch,
output choke, output terminals,
etc.)

2. Check for faulty connections or
a defective thermostat. Check
leads #313, #314,.#315 and
#316. See the Wiring Diagram.
The thermal light will be on.

3. Perform the

T1 Transformer

Test.

4. Perform the

SCR Bridge Test.

5. Check the current control R1 for
proper operation. Normal resis­tance is 10,000 ohms. Also
check associated leads for
loose or faulty connections.

6. The control board may be faulty.

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TROUBLESHOOTING & REPAIR

F-6 F-6

SQUARE WAVE TIG 275

Observe Safety Guidelines TROUBLESHOOTING GUIDE
detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

OUTPUT PROBLEMS

No output from the machine in either Stick or TIG modes. The thermal light is on.

1. The welding application may
have exceeded the recom­mended duty cycle. Allow the
fan to cool the unit until the ther­mal light is off.

2. The air louvers may be blocked.
Remove the air obstruction and
allow the unit to cool.

1. One of the thermostats may be
faulty. Check or replace. See
the Wiring Diagram.

2. Check for loose or faulty wires
on the thermostats and associ­ated circuitry. See the Wiring
Diagram.

3. The fan motor may be faulty or
mechanically obstructed. The
fan should run when welding or
when a thermostat is open.

4. The control board may be faulty.

The machine does not respond (no
gas flow, no high frequency and no
open circuit voltage) when the arc
start switch or Amptrol is activated.
The thermal light is not lit.

1. Make certain the machine is in
the TIG mode.

2. The Amptrol or arc start switch
may be defective. Check for
continuity (zero ohms) between
pins “D” and “E” on the cable
connector when the Amptrol or
arc start switch is pressed.

1. Check the continuity (zero
ohms) of the leads between the
remote receptacle and plug J7
on the control board. See the
Wiring Diagram.

2. Perform the

T1 Transformer

Test.

3. The control board may be faulty.

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TROUBLESHOOTING & REPAIR

F-7 F-7

SQUARE WAVE TIG 275

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call 216­383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

OUTPUT PROBLEMS

The machine does not have weld­ing output in the Stick mode. The
machine operates correctly in the
TIG mode.

1. Check the electrode cable and
holder for loose or faulty con­nections.

2. Make sure the Stick/TIG switch
(S3) is in the proper position
and operating correctly.

1. Check the Stick/TIG switch (S3)
and associated leads. See the
Wiring Diagram.

2. The control board may be faulty.

The machine welds at a very low output regardless of the current control setting.

1. If welding in the TIG mode, the
remote control device may be
defective.

2. Make certain the input line volt­age is correct for the machine’s
reconnect configuration.

3. Check the welding cables
and/or torch for loose or faulty
connections.

1. Check the polarity switch and
associated leads.

2. Check the interior connections
of the heavy current carrying
leads.

3. Perform the

SCR Bridge Test.

4. Perform the

T1 Transformer

Test.

5. Check the current control for
proper operation. Normal resis­tance is 10,000 ohms. See the
Wiring Diagram.

6. The control board may be faulty.

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TROUBLESHOOTING & REPAIR

F-8 F-8

SQUARE WAVE TIG 275

Observe Safety Guidelines TROUBLESHOOTING GUIDE
detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

OUTPUT PROBLEMS

The machine welds at a very high output regardless of the current control setting.

1. If welding in the TIG mode, the
remote control device may be
defective.

1. Perform the

SCR Bridge Test.

2. Perform the

T1 Transformer

Test.

3. Check the current control for
proper operation. Normal resis­tance is 10,000 ohms. See the
Wiring Diagram.

4. Check leads #221 and #222
between the output shunt and
the control board. See the
Wiring Diagram.

5. The control board may be faulty.

Accessories plugged into the 115
volt receptacle do not work. (220
VAC receptacle on European mod­els only).

1. Make sure the accessory, plug
and associated leads are in
good working condition.

2. Make certain the correct input
voltage is being applied to the
machine. (The reconnect lead
must be in the correct position.)

3. The circuit breaker may be
tripped. Reset if necessary.

1. The circuit breaker (CB) may be
faulty.

2. Check the receptacle and asso­ciated leads for loose or faulty
connections.

3. Perform the

T1 Transformer

Test.

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TROUBLESHOOTING & REPAIR

F-9 F-9

SQUARE WAVE TIG 275

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

OUTPUT PROBLEMS

The machine makes a very loud
buzzing noise in DC Stick or in DC
TIG modes. There is no current
draw from the machine’s output ter­minals. (The machine is not exter­nally loaded).

1. Inspect the output terminal insu­lators for cracks or signs of
overheating.

1. Diode D1 may be shorted.
Check and replace if necessary.

2. Check the polarity switch (S2)
for proper function and correct
connections.

3. Perform the

SCR Bridge Test.

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TROUBLESHOOTING & REPAIR

F-10 F-10

SQUARE WAVE TIG 275

Observe Safety Guidelines TROUBLESHOOTING GUIDE
detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

TIG WELDING PROBLEMS

The machine output is intermittent­ly lost. Gas flow and high frequen­cy are also interrupted.

1. The problem may be caused by
high frequency interference.
Make sure that the machine is
grounded properly according to
the installation instructions. If
there are other high frequency
sources in the area, make cer­tain that they are grounded
properly.

2. Make sure the Amptrol is oper­ating properly.

3. Check to make sure that the
input voltage is correct for the
machine to reconnect configura­tion. Refer to

Reconnect

Procedure

in the Installation

section of this manual.

1. Check for loose or faulty con­nections on the leads between
the remote receptacle and plug
J7 on the control board. See
the Wiring Diagram.

2. Check the plugs on the control
board for loose connections.

3. The control board may be faulty.

No gas or water flow (with optional
water solenoid) when the arc start
switch or Amptrol is activated in the
TIG mode. All other machine func­tions are normal.

1. The gas (or water) supply is
either empty or not turned on.

2. The flow regulator may be set
too low.

3. Check the supply hoses for
kinks or blockages.

4. The filters may be blocked.

1. Perform the

Gas Solenoid

Test.

2. The control board may be faulty.

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TROUBLESHOOTING & REPAIR

F-11 F-11

SQUARE WAVE TIG 275

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

TIG WELDING PROBLEMS

No high frequency . The machine is in the TIG mode and has normal output.

1. If the machine is in a highly dirty
environment with conductive
contaminants, check and clean
the spark gap with a low pres­sure air stream per the mainte­nance instructions.

2. Check the spark gap operation
and setting. Normal is (0.015”).
Refer to the

Maintenance

Section

of this manual.

1. Check the high voltage trans­former (T2). The normal resis­tance of the secondary winding
is 12.5k ohms.

ELECTRIC SHOCK
CAN KILL. When

115 VAC is applied to
the primary of T2, a

very high voltage is
developed on the secondary wind­ing. For assistance, call the
Lincoln Electric Service Depart­ment. (216-383-2531 or 1-800­833-9353 (WELD).

2. Check R5, C6, C5, L3 and L4.

Replace if defective.

3. The control board may be faulty.

WARNING

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F-12 F-12

SQUARE WAVE TIG 275

TROUBLESHOOTING & REPAIR

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

TIG WELDING PROBLEMS

The high frequency “spark” is pre­sent but weak.

1. The spark gap may be too
large. Check and reset per
instructions in the

Maintenance

Section

of this manual.

2. The work and/or torch cables
may be in poor condition allow­ing the high frequency to “lead”
to ground. Use good quality
cables, preferably those with a
high natural rubber content and
as short as possible.

3. If helium shielding gas is being
used, reduce the percentage of
helium.

4. Make sure the tungsten elec­trode is the correct size for the
process.

1. The high voltage transformer
(T2) may be faulty.

2. Capacitor C5 may be faulty.

3. The high frequency transformer
(T3) may be faulty.

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TROUBLESHOOTING & REPAIR

F-13 F-13

SQUARE WAVE TIG 275

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

TIG WELDING PROBLEMS

The high frequency “spark” is pre­sent at the tungsten electrode, but
the operator is unable to establish
a welding arc. The machine has
normal open circuit voltage. Refer
to

Technical Specifications

in the

Installation section.

1. The torch may be faulty. Check
or replace.

2. The current control may be set
too low.

3. The tungsten electrode may be
contaminated. Replace or
sharpen.

4. The electrode may be too large
for the process.

5. If a helium blend is being used
as a shielding gas, reduce the
percentage of helium.

6. Check the welding cables for
loose or faulty connections.

1. Check spark gap adjustment.
See the

Maintenance

section.

2. This may be a welding proce­dure problem.

Contact the Lincoln Service
Department [phone] or
1-800-833-9353 (WELD).

When AC TIG welding, the arc is
erratic and there is a loss of “clean­ing” of the work piece.

1. The tungsten electrode may be
small for the process. Use a
larger diameter tungsten or a
pure tungsten.

2. If a helium blend is used as a
shielding gas, reduce the per­centage of helium.

1. Check components R5 and C6
in the high voltage transformer
primary circuit.

2. Perform the

SCR Bridge Test.

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TROUBLESHOOTING & REPAIR

F-14 F-14

SQUARE WAVE TIG 275

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

STICK WELDING PROBLEMS

The stick electrode “blasts-off” when touched to the work piece.

1. The welding current may be too
high for the electrode size.
Reduce current control setting
or use a larger diameter elec­trode.

1. Perform the

SCR Bridge Test.

2. The control board may be faulty.

V ariable or sluggish welding arc when welding in the Stick mode.

1. Check the work and electrode
cables for loose or poor connec­tions.

2. The welding cables may be too
small or too long to permit the
desired current to flow.

3. The welding current may be set
too low.

1. Check the polarity switch for
excessive wear or faulty con­nections.

2. Check the interior heavy current
carrying leads and connections.

F-15 F-15

SQUARE WAVE TIG 275

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TROUBLESHOOTING & REPAIR

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

FUNCTION PROBLEMS

The control panel displays do not function correctly.

1. The displays will read “000” until
the torch trigger is activated
and/or the welding arc is estab­lished. The voltmeter will nor­mally display open circuit volt­age in the Stick mode before
the arc is established.

1. Check the connections and
associated leads between the
display board and the control
board. (Plugs P4, P20 and
P21). See the Wiring Diagram.

2. The display board may be
faulty.

3. The control board may be faulty.

The voltmeter always reads “000” but the welding output is normal.

1. None 1. Check the continuity (zero
ohms) of leads #252 and #253
between the polarity switch and
plug J6 on the control board.
See the Wiring Diagram.

2. Check for open circuit voltage at
leads #252 to #253 at plug J6
on the control board. If open
circuit voltage is present, also
check for same voltage at plug
J4 pin-8 to pin-5. If the same
voltage is NOT present at plug
J4, the control board may be
faulty.

3. If the correct voltages are pre­sent in Step #2, check the
leads, plugs and connections
between the control board and
the display board.

4. The display board may be
faulty.

F-16 F-16

SQUARE WAVE TIG 275

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TROUBLESHOOTING & REPAIR

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

FUNCTION PROBLEMS

The ammeter display reads “000.” The machine has output but no control.

1. None 1. Check leads #221 and #222
between the output shunt and
plug J2 on the control board.
See the Wiring Diagram.

2. The control board may be faulty.

One of the display meters is blank. 1. None 1. Check the leads and connec-

tions between the display board
and the control board. See the
Wiring Diagram.

2. The display board may be
faulty.

INSTALLATION

F-17 F-17

SQUARE WAVE TIG 275

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TROUBLESHOOTING & REPAIR

TROUBLESHOOTING GUIDE Observe Safety Guidelines

detailed in the beginning of this manual.

CAUTION

If for any reason you do not understand the test procedures or are unable to perform the test/repairs safely, con­tact the Lincoln Electric Service Department for electrical troubleshooting assistance before you proceed. Call
216-383-2531 or 1-800-833-9353.

PROBLEMS
(SYMPTOMS)

POSSIBLE AREAS OF
MISADJUSTMENT(S)

RECOMMENDED
COURSE OF ACTION

FUNCTION PROBLEMS

The AC wave balance control does not function properly.

1. The AC wave balance control is
operational only in the TIG
mode.

1. Check the AC balance control
(R2) and associated leads for
loose or faulty connections.
See the Wiring Diagram.

2. The control board may be faulty.

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TROUBLESHOOTING & REPAIR

F-18 F-18

SQUARE WAVE TIG 275

HIGH FREQUENCY CIRCUIT DISABLE PROCEDURE

WARNING

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

If for any reason you do not understand the test procedures or are unable to perform the
test/repairs safely, contact the Lincoln Electric Service Department for electrical trou­bleshooting assistance before you proceed. Call 216-383-2531 or 1-800-833-9353
(WELD).

TEST DESCRIPTION

This procedure will disable the high frequency circuit. The technician will then be able to
take voltage measurements without the possibility of high frequency damage to his test
equipment.

MATERIALS NEEDED

3/8" Nut driver
Electrical insulating tape

This procedure takes approximately 8 minutes to perform.

WARNING

HIGH VOLTAGE IS STILL PRESENT IN THE HIGH FREQUENCY CIRCUIT.

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TROUBLESHOOTING & REPAIR

F-19 F-19

SQUARE WAVE TIG 275

LEADS
ATTACH
HERE

.015 Spark Gap

RIGHT SIDE VIEW OF MACHINE

FIGURE F.1 – SPARK GAP ASSEMBLY

HIGH FREQUENCY CIRCUIT DISABLE PROCEDURE (continued)

PROCEDURE

1. Remove the input power to the TIG 275
machine.

2. Using the 3/8” nut driver, remove the right
side case cover.

3. Locate the Spark Gap Assembly at the lower
right side of the machine. See Figure F.1.

4. Carefully remove the two leads and washers
from the Spark Gap Assembly.

5. Insulate the leads from each other and from
the case.

When power is applied to the
machine there is a very high
voltage present at these leads.

6. When voltage testing and scope measure­ments are complete, attach the two leads
and washers to the Spark Gap Assembly.
NOTE: Make sure insulation is still in place.

7. Reassemble the right side case cover.

WARNING

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TROUBLESHOOTING & REPAIR

F-20 F-20

SQUARE WAVE TIG 275

WARNING

T1 MAIN TRANSFORMER TEST

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

If for any reason you do not understand the test procedures or are unable to perform the
test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshoot­ing assistance before you proceed. Call 216-383-2531 or 1-800-833-9353 (WELD).

TEST DESCRIPTION

This test will determine if the correct voltage is being applied to the primary of the T1 trans­former and also if the correct voltages are being induced on the secondary windings of the
transformer.

MATERIALS NEEDED

Volt/Ohmmeter (Multimeter)
TIG 275 Wiring Diagrams
3/8” Nut driver

This procedure takes approximately 15 minutes to perform.

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TROUBLESHOOTING & REPAIR

F-21 F-21

SQUARE WAVE TIG 275

T1 MAIN TRANSFORMER TEST (continued)

FIGURE F.2 – PLUG J8 LOCATION ON CONTROL BOARD

S-W TIG 275 CONTROL

J8PIN 14 (LEAD #212)

PIN 12 (LEAD #232A)

PIN 9 (LEAD #209)

PIN 1 (LEAD #210)

PIN 2 (LEAD #231)

PIN 6 (LEAD #201)

PIN 4 (LEAD #204)

PIN 13 (LEAD #211A)

G3360-[ ]

TEST PROCEDURE

1. Remove main supply power to the machine.

2. Using the 3/8” nut driver, remove the case
left and right side covers.

3. Locate plug J8 on the control board. See
Figure F.2.

ELECTRIC SHOCK can
kill.

• With input power ON, there are
high voltages inside the
machine. Do not reach into the
machine or touch any internal
part.

4. Carefully apply the correct input power mak­ing certain the reconnect configuration at the
reconnect panel is correct for the input volt­age applied. Turn the TIG 275 ON.

5. Using the voltmeter, carefully test for the cor ­rect transformer secondary voltages per
Table F.1.

WARNING

TROUBLESHOOTING & REPAIR

F-22 F-22

SQUARE WAVE TIG 275

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T1 MAIN TRANSFORMER TEST (continued)

6. If all of the secondary voltages are correct, the
T1 transformer is functioning properly.

a. If all of the secondary voltages are missing

or incorrect, make certain that the correct
input voltage is being applied to the correct
primary leads. See Table F.1.

b. If the correct input voltage is being applied

to the primary leads and any or all of the
secondary voltages are incorrect, the T1
transformer may be faulty. See

Main
Transformer and Output Choke
Removal and Replacement.

Also check
the leads for broken or loose connections
between plug J8 and the T1 transformer.

7. Replace the case side covers.

TROUBLESHOOTING & REPAIR

F-23 F-23

SQUARE WAVE TIG 275

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T1 MAIN TRANSFORMER TEST (continued)

TABLE F.1.

T1 TRANSFORMER VOLTAGES

TEST POINTS ACCEPTABLE VOLTAGES

SECONDARY WINDINGS SECONDARY VOLTAGES

PLUG J8 PIN 1 (LEAD #210)

TO

PLUG J8 PIN 9 (LEAD #209) 18 VAC

PLUG J8 PIN 6 (LEAD #201)

TO

PLUG J8 PIN 4 (LEAD #204) 18 VAC

PLUG J8 PIN 2 (LEAD #231)

TO

PLUG J8 PIN 12 (LEAD #232A) 115 VAC

PLUG J8 PIN 13 (LEAD #211A)

TO

PLUG J8 PIN 14 (LEAD #212) 23 VAC

X1 TO X2 78 VAC

PRIMARY WINDINGS

1

PRIMARY VOLTAGES

H1 TO H2 208 VAC
H1 TO H3 230 VAC
H1 TO H4 460 VAC

NOTE: If the input voltages vary, the secondary voltages will vary accordingly.

1

Based on 208/230/460 models. For other voltage models refer to appropriate wiring diagram.

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TROUBLESHOOTING & REPAIR

F-24 F-24

SQUARE WAVE TIG 275

WARNING

GAS (WATER) SOLENOID TEST

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

If for any reason you do not understand the test procedures or are unable to perform the
test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshoot­ing assistance before you proceed. Call 216-383-2531 or 1-800-833-9353 (WELD).

TEST DESCRIPTION

This procedure will help the technician to determine if the solenoid is receiving the correct volt­age and also if the solenoid is functional.

MATERIALS NEEDED

3/8” Nut driver
Volt/Ohmmeter (Multimeter)
Isolated 115 VAC power supply

This procedure takes approximately 10 minutes to perform.

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TROUBLESHOOTING & REPAIR

F-25 F-25

SQUARE WAVE TIG 275

GAS (WATER) SOLENOID TEST (continued)

FIGURE F.3 – GAS SOLENOID LOCATION

GAS
SOLENOID

CASE BACK

LEFT SIDE
INTERNAL
PANEL

CONTROL
BOARD

TEST PROCEDURE

1. Remove input power to the TIG 275
machine.

2. Remove the left case side.

3. Perform the

High Frequency Circuit

Disable Procedure.

4. Locate the gas solenoid. See Figure F.3.

5. Put the mode switch S3 in the 2-Step TIG
position.

ELECTRIC SHOCK can
kill.

• With input power ON, there are
high voltages inside the
machine. Do not reach into the
machine or touch any internal
part.

6. Apply the correct input power to the TIG

275.

7. Activate the torch trigger and check for
approximately 115 VAC at the solenoid

leads (#234 and #235). If the correct volt­age is present, the solenoid should activate
and gas should flow.

8. If voltage is present at leads #234 and #235
and the solenoid does not activate, the
solenoid may be defective. The solenoid
can be further checked by removing leads

#234 and #235 from the solenoid and
applying the external isolated 1 15 VAC sup­ply to the solenoid terminals. If the solenoid
activates with the external supply but not
when powered by the control board, the
problem may be in the control board. If you
hear solenoid activation but there is still no
gas flow, check for restrictions in the line.

9. When the test is complete, replace leads
#234 and #235.

10. Reassemble the two leads previously
removed in the

High Frequency Circuit

Disable Procedure.

11. Reassemble the left case side.

12. If a water solenoid is used, it can be tested
using the same procedures.

WARNING

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TROUBLESHOOTING & REPAIR

F-26 F-26

SQUARE WAVE TIG 275

WARNING

STATIC SCR TEST

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

If for any reason you do not understand the test procedures or are unable to perform the
test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshoot­ing assistance before you proceed. Call 216-383-2531 or 1-800-833-9353 (WELD).

TEST DESCRIPTION

The Static SCR Test is a quick check to determine if an SCR is shorted or “leaky.” See
machine waveform section for normal and abnormal SCR waveforms.

MATERIALS NEEDED

Analog Ohmmeter (Multimeter)
TIG 275 Wiring Diagrams
SCR Heat Sink Assembly Drawing
3/8” Nut driver

This procedure takes approximately 12 minutes to perform.

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TROUBLESHOOTING & REPAIR

F-27 F-27

SQUARE WAVE TIG 275

STATIC SCR TEST (continued)

FIGURE F.4 – PLUG J1 LOCATION ON CONTROL BOARD

S-W TIG 275 CONTROL

G3360-[ ]

J1

J8

TEST PROCEDURE

1. Remove main supply power to the TIG 275
and remove the case top and left side.

2. Locate and remove plug J1 from the control
board. See Figure F.4.

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TROUBLESHOOTING & REPAIR

F-28 F-28

SQUARE WAVE TIG 275

STATIC SCR TEST (continued)

3. Using an analog ohmmeter, test the resis­tance from anode to cathode of SCR1.
Reverse the meter leads and check from
cathode to anode of SCR1. See Figure F.5.
If a low resistance is indicated in either
direction, SCR1 is faulty. Replace the SCR
Bridge Assembly. See

SCR Bridge

Assembly Removal and Replacement.

4. Repeat Step #3 testing SCR2, SCR3 and
SCR4.

5. To further check the SCR’s functions, use an
SCR tester and proceed to the

Active SCR

Test.

NOTE: Also check diode D1.

6. Replace plug J1 on the control board.

7. Replace the case top and left side.

FIGURE F.5 – SCR TEST POINTS

SCR4 CATHODE

SCR1 / SCR2 CATHODE

SCR3 CATHODE

SCR2 ANODE

SCR1 ANODE

SCR3 / SCR4 ANODE

DIODE D1

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TROUBLESHOOTING & REPAIR

F-29 F-29

SQUARE WAVE TIG 275

WARNING

ACTIVE SCR TEST

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

If for any reason you do not understand the test procedures or are unable to perform the
test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshoot­ing assistance before you proceed. Call 216-383-2531 or 1-800-833-9353 (WELD).

DESCRIPTION

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

MATERIALS NEEDED

An SCR tester as outlined in this procedure
TIG 275 Wiring Diagram
3/8” Nut driver

This procedure takes approximately 20 minutes to perform.

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TROUBLESHOOTING & REPAIR

F-30 F-30

SQUARE WAVE TIG 275

ACTIVE SCR TEST (continued)

FIGURE F.6 – PLUG J1 LOCATION ON CONTROL BOARD

S-W TIG 275 CONTROL

G3360-[ ]

J1

J8

TEST PROCEDURE

1. Remove main supply power to the TIG 275
machine.

2. Locate and remove plug J1 from the control
board. See Figure F.6.

3. Perform the following test for all four SCRs.
See

Figure F.8.

4. Construct the circuit outlined in

Figure F.7.

One 6V lantern battery can be used.
Resistor values are ± 10%. The voltmeter
scale should be low, approximately 0-5 or 0­10 volts.

5. Battery Test – Check the battery by shorting
leads (A) and (C) and then close switch SW-

1. Replace the battery if voltage is less than

4.5 volts.

TROUBLESHOOTING & REPAIR

F-31 F-31

SQUARE WAVE TIG 275

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ACTIVE SCR TEST (continued)

FIGURE F.7 – ACTIVE SCR TEST SETUP

R2

SW2

SW1

V

R1

6volt
Lantern
Battery

A

G

C

SCR
under
test

R1 = 4 ohms / 10 watts
R2 = 3 ohms / 10 watts
Resistor valves are ± 10%

TROUBLESHOOTING & REPAIR

F-32 F-32

SQUARE WAVE TIG 275

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ACTIVE SCR TEST (continued)

FIGURE F.8 – SCR GATE LOCATIONS

SCR4 CATHODE

SCR1 / SCR2 CATHODE

SCR3 CATHODE

SCR2 ANODE

SCR1 ANODE

SCR3 / SCR4 ANODE

DIODE D1

6. Connect SCR into the test circuit as shown in

Figure F.7

: (A) lead to anode (C) lead to cath-

ode and (G) lead to the gate.

7. Close switch SW-1 (Switch SW-2 should be
open). The voltmeter should read zero. If the
voltmeter reads higher than zero, the SCR is
shorted.

8. With switch SW-1 closed, close switch SW-2
for two seconds and release. The voltmeter
should read 3 to 6 volts before and after
switch SW-2 is released. If the voltmeter does
not read, or reads only while SW-2 is
depressed, the SCR or battery is defective.
(Repeat Battery Test Procedure described in
Step 5.)

9. Open switch SW-1, disconnect the gate lead
(G) and reverse the (A) and (C) leads on the
SCR. Close switch SW-1. The voltmeter
should read zero. If the voltage is higher
than zero, the SCR is shorted.

10. Replace the SCR Bridge Assembly if any
SCRs do not pass the test in Step #3. See

SCR Bridge Assembly Removal and
Replacement.

11. Replace plug J1 on the control board.

12. Replace the case sides and top.

TROUBLESHOOTING & REPAIR

F-32 F-32

SQUARE WAVE TIG 275

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TROUBLESHOOTING & REPAIR

F-33 F-33

SQUARE WAVE TIG 275

This is the typical AC output voltage
waveform generated from a properly
operating machine. Note that each
vertical division represents 50 volts
and that each horizontal division rep­resents 2 milliseconds in time.

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

NOTE: AC balance control set at
“Balanced” position.

SCOPE SETTINGS

Volts/Div....................50 V/Div.

Horizontal Sweep.....2 ms/Div.

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

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

NORMAL OPEN CIRCUIT VOLTAGE WAVEFORM

AC TIG MODE

0 V

50 V

2 ms

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and waveform checks with high frequency circuit OFF.

• Perform High Frequency Disable Procedure.

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TROUBLESHOOTING & REPAIR

F-34 F-34

SQUARE WAVE TIG 275

This is the typical DC (+) output volt­age waveform generated from a prop­erly operating machine. Note that
each vertical division represents 50
volts and that each horizontal division
represents 2 milliseconds in time.

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

SCOPE SETTINGS

Volts/Div....................50 V/Div.

Horizontal Sweep.....2 ms/Div.

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

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

NORMAL OPEN CIRCUIT VOLTAGE WAVEFORM

DC TIG MODE

0 V

2 ms

50 V

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and waveform checks with high frequency circuit OFF.

• Perform High Frequency Disable Procedure.

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TROUBLESHOOTING & REPAIR

F-35 F-35

SQUARE WAVE TIG 275

This is the typical AC output voltage
waveform generated from a properly
operating machine. Note that each
vertical division represents 50 volts
and that each horizontal division rep­resents 2 milliseconds in time.

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

SCOPE SETTINGS

Volts/Div....................50 V/Div.

Horizontal Sweep.....2 ms/Div.

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

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

0 V

2 ms

50 V

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and waveform checks with high frequency circuit OFF.

• Perform High Frequency Disable Procedure.

NORMAL OPEN CIRCUIT VOLTAGE WAVEFORM

AC STICK MODE

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TROUBLESHOOTING & REPAIR

F-36 F-36

SQUARE WAVE TIG 275

NORMAL OPEN CIRCUIT VOLTAGE WAVEFORM

DC STICK MODE

This is the typical DC (+) output volt­age waveform generated from a prop­erly operating machine. Note that
each vertical division represents 50
volts and that each horizontal division
represents 2 milliseconds in time.

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

SCOPE SETTINGS

Volts/Div....................50 V/Div.

Horizontal Sweep.....2 ms/Div.

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

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

0 V

2 ms

50 V

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and waveform checks with high frequency circuit OFF.

• Perform High Frequency Disable Procedure.

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TROUBLESHOOTING & REPAIR

F-37 F-37

SQUARE WAVE TIG 275

TYPICAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED

AC TIG MODE

MACHINE LOADED TO 255 AMPS
AT 30 VAC.

This is the typical AC output voltage
waveform generated from a properly
operating machine. Note that each
vertical division represents 20 volts
and that each horizontal division rep­resents 2 milliseconds in time. The
machine was loaded with a resistance
grid bank.

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

NOTE: AC balance control set at
“Balanced” position.

SCOPE SETTINGS

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

Horizontal Sweep.....2 ms/Div.

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

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

0 V

2 ms

20 V

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and waveform checks with high frequency circuit OFF.

• Perform High Frequency Disable Procedure.

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TROUBLESHOOTING & REPAIR

F-38 F-38

SQUARE WAVE TIG 275

MACHINE LOADED TO 275 AMPS
AT 31 VDC.

This is the typical DC (+) output volt­age waveform generated from a prop­erly operating machine. Note that
each vertical division represents 20
volts and that each horizontal division
represents 2 milliseconds in time. The
machine was loaded with a resistance
grid bank.

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

SCOPE SETTINGS

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

Horizontal Sweep.....2 ms/Div.

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

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

0 V

2 ms

20 V

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and waveform checks with high frequency circuit OFF.

• Perform High Frequency Disable Procedure.

TYPICAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED

DC TIG MODE

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TROUBLESHOOTING & REPAIR

F-39 F-39

SQUARE WAVE TIG 275

MACHINE LOADED TO 275 AMPS
AT 31 VDC.

This is the typical AC output voltage
waveform generated from a properly
operating machine. Note that each
vertical division represents 20 volts
and that each horizontal division rep­resents 2 milliseconds in time. The
machine was loaded with a resistance
grid bank.

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

SCOPE SETTINGS

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

Horizontal Sweep.....2 ms/Div.

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

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

0 V

2 ms

20 V

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and waveform checks with high frequency circuit OFF.

• Perform High Frequency Disable Procedure.

TYPICAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED

AC STICK MODE

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TROUBLESHOOTING & REPAIR

F-40 F-40

SQUARE WAVE TIG 275

MACHINE LOADED TO 275 AMPS
AT 31 VDC.

This is the typical AC output voltage
waveform generated from a properly
operating machine. Note that each
vertical division represents 20 volts
and that each horizontal division rep­resents 2 milliseconds in time. The
machine was loaded with a resistance
grid bank.

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

SCOPE SETTINGS

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

Horizontal Sweep.....2 ms/Div.

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

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

0 V

2 ms

20 V

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and waveform checks with high frequency circuit OFF.

• Perform High Frequency Disable Procedure.

TYPICAL OUTPUT VOLTAGE WAVEFORM - MACHINE LOADED

DC STICK MODE

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TROUBLESHOOTING & REPAIR

F-41 F-41

SQUARE WAVE TIG 275

This is NOT the typical DC (+) output
voltage waveform. One output SCR is
not functioning. Note the “gap” in the
waveform. One SCR gate was dis­connected to simulate an open or non­functioning output SCR. Note that
each vertical division represents 50
volts and that each horizontal division
represents 2 milliseconds in time.

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

SCOPE SETTINGS

Volts/Div....................50 V/Div.

Horizontal Sweep.....2 ms/Div.

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

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

0 V

2 ms

50 V

CAUTION

HIGH VOLTAGE / HIGH FREQUENCY can damage test equipment.

• Perform all voltage and waveform checks with high frequency circuit OFF.

• Perform High Frequency Disable Procedure.

ABNORMAL OPEN CIRCUIT VOLTAGE - DC TIG MODE

ONE OUTPUT SCR NOT FUNCTIONING

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TROUBLESHOOTING & REPAIR

F-42 F-42

SQUARE WAVE TIG 275

WARNING

HIGH VOLTAGE TRANSFORMER REMOVAL

AND REPLACEMENT

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

If for any reason you do not understand the test procedures or are unable to perform the
test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshoot­ing assistance before you proceed. Call 216-383-2531 or 1-800-833-9353 (WELD).

DESCRIPTION

This procedure will aid the technician in the removal and replacement of the high voltage
transformer.

MATERIALS NEEDED

3/8” Nut driver
Needle nose pliers
Phillips head screw driver
Wire cutters

This procedure takes approximately 25 minutes to perform.

TROUBLESHOOTING & REPAIR

F-43 F-43

SQUARE WAVE TIG 275

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HIGH VOLTAGE TRANSFORMER REMOVAL

AND REPLACEMENT (continued)

FIGURE F.9 – SECONDARY LEADS AT HIGH FREQUENCY STARTER BOARD

TRANSFORMER
SECONDARY
LEADS

SQUARE

W

A

VE

TIG

275

REMOVAL PROCEDURE

1. Remove input power to the TIG 275 machine.

2. Using the 3/8” nut driver, remove the case
sides.

3. With the needle nose pliers, remove the two
secondary leads from the quick-connects on
the high frequency arc starter board assem­bly. See Figure F.9.

4. Disconnect the in-line splice quick connect
from one primary lead to lead #238. Cut any
necessary cable ties.

5. Remove the lead splice from the other prima­ry lead that is connected to lead #237, C6
capacitor and R5 resistor. See the Wiring
Diagram. Cut any necessary cable ties.

6. Using the phillips head screw driver, remove
the front mounting screw from the base of the
high voltage transformer. Take note of insula­tor placement for reassembly.

7. With the phillips head screw driver, loosen the

two rear mounting screws.

8. Carefully slide the transformer forward and
remove it from the TIG 275 machine.

TROUBLESHOOTING & REPAIR

F-44 F-44

SQUARE WAVE TIG 275

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HIGH VOLTAGE TRANSFORMER REMOVAL

AND REPLACEMENT (continued)

FIGURE F.10 – HIGH VOLTAGE TRANSFORMER MOUNTING INSULATORS

FRONT MOUNTING
INSULATOR

SLOTTED REAR
MOUNTING INSULATORS

REPLACEMENT PROCEDURE

1. Carefully position the new high voltage trans­former in place in the two rear mounting insu­lators. See Figure F.10.

2. Install the front mounting insulator and mount­ing screw.

3. Using the phillips head screw driver , tighten all
three mounting screws making certain the
insulators are positioned correctly.

4. Reconnect the two primary leads.

5. Reconnect the two secondary leads to the
high frequency arc starter board assembly.

6. Replace any previously removed cable ties.

7. Replace the case sides.

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TROUBLESHOOTING & REPAIR

F-45 F-45

SQUARE WAVE TIG 275

WARNING

SCR BRIDGE ASSEMBLY REMOVAL AND REPLACEMENT

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

If for any reason you do not understand the test procedures or are unable to perform the
test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshoot­ing assistance before you proceed. Call 216-383-2531 or 1-800-833-9353 (WELD).

DESCRIPTION

The following procedure will aid the technician in removing the SCRs from the output rectifier
heat sink for maintenance or replacement.

MATERIALS NEEDED

3/8” Nut driver
1/2” Wrench
7/16” Wrench
3/8” Wrench
Penetrax A13 joint compound

This procedure takes approximately 40 minutes to perform.

TROUBLESHOOTING & REPAIR

F-46 F-46

SQUARE WAVE TIG 275

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SCR BRIDGE ASSEMBLY REMOVAL AND REPLACEMENT (continued)

FIGURE F.11 – RECEPTACLE/CIRCUIT BREAKER LEADS

CIRCUIT
BREAKER

RECEPTACLE

CASE BACK SCREW

CASE
BACK

CASE BACK
SCREW

PROCEDURE

NOTE: “Left” and “right” are from the rear of the

machine looking in.

1. Remove input power to the TIG 275 machine.

2. Using the 3/8” nut driver, remove the case
sides and top.

3. Using the 3/8” nut driver, remove the nine
screws from the case back.

4. Carefully remove the case back and set aside.
NOTE: The receptacle and circuit breaker
leads will still be attached. See Figure F.11.

5. With the 3/8” nut driver, remove the three
screws mounting the fan motor bracket
assembly to the internal glastic divider panel.
See Figure F.12.

6. Carefully pull the fan assembly away to allow
access to the SCR Bridge Assembly. Support
the fan assembly so as not to stress the fan
motor leads. It is not necessary to disconnect
the fan motor leads.

FIGURE F.12 – FAN MOTOR BRACKET ASSEMBLY MOUNTING

SQUARE WAVETIG 275

FAN
MOTOR
BRACKET
ASSEMBLY

MOUNTING
SCREWS
(3)

INTERNAL
GLASTIC
DIVIDER

TROUBLESHOOTING & REPAIR

F-47 F-47

SQUARE WAVE TIG 275

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SCR BRIDGE ASSEMBLY REMOVAL AND REPLACEMENT (continued)

FIGURE F.13 – SCR BRIDGE CONNECTIONS

X2 LEAD LOCATION
(STEP 10)

LEAD #216

SHUNT & #220 LEAD
LOCATIONS (STEP 11)

"NEG" IN SLEAVING
(STEP 8)

"B"
(STEP 12)

LEAD
#217

"POS" LEAD (STEP 7)

For Steps 7-13, see Figure F.13.

7. Using the 7/16” wrench, label and remove the
“POS” lead from the left side heat sink assem­bly . It is not necessary to remove the #218
lead.

8. Using the 7/16” wrench, label and remove the
“NEG” lead from the D1 diode pigtail.
NOTE: It will be necessary to remove the
sleeve insulation to gain access to the con­nection.

9. Remove plug J1 from the control board. Also
remove the plug and lead harness from the
internal divider panel.

10. With the 1/2” wrench, remove the X2 trans-

former secondary lead from the right side
heat sink assembly. It is not necessary to
remove the jumper lead or the #216 lead.

11. With the 7/16” wrench, remove the shunt and
one #220 lead from the right side negative
heat sink assembly. It is not necessary to
remove the other #220 lead.

12. Using the 1/2” wrench, remove the “B” lead

from the AC left side heat sink. It is not nec­essary to remove the copper jumper or the
#217 lead.

13. Using the 3/8” wrench, remove the four

mounting screws holding the SCR Bridge
Assembly to the transformer iron assembly.

14. Carefully remove the SCR Bridge assembly

from the machine.

TROUBLESHOOTING & REPAIR

F-48 F-48

SQUARE WAVE TIG 275

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SCR BRIDGE ASSEMBLY REMOVAL AND REPLACEMENT (continued)

REPLACEMENT PROCEDURE

Refer to Figures F.11 - F.13.

1. Carefully place the new SCR bridge assembly
in position in the TIG 275.

2. Using the 3/8” wrench, install the four mount­ing screws.

Use Penetrox A13 joint compound on all alu­minum connections.

3. Assemble lead “B” onto the AC left heat sink.

4. Assemble the shunt to the right side negative
heat sink.

5. Assemble the X2 transformer secondary lead
onto the right side heat sink.

6. Feed the J1 plug and harness through the
internal divider and install the plug into the
control board.

7. Assembly the “NEG” lead to the D1 diode pig­tail. Replace and secure sleeve insulation.

8. Assemble the “POS” lead to the left side heat
sink.

9. Carefully position the fan motor assembly into
place.

10. Attach the fan motor assembly onto the glas-

tic divider using the three screws previously
removed.

11. Carefully position the case back into place,

being careful not to disconnect the leads
from the circuit breaker or receptacle.

12. Secure the case back with the nine screws

previously removed.

13. Assemble the case sides and top.

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TROUBLESHOOTING & REPAIR

F-49 F-49

SQUARE WAVE TIG 275

WARNING

POLARITY SWITCH REMOVAL AND REPLACEMENT

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

If for any reason you do not understand the test procedures or are unable to perform the
test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshoot­ing assistance before you proceed. Call 216-383-2531 or 1-800-833-9353 (WELD).

DESCRIPTION

This procedure will aid the technician in the removal and replacement of the polarity switch.

MATERIALS NEEDED

3/8” Nut driver
1/2” Wrench
7/16” Wrench
Phillips head screw driver
5/64” Allen type wrench
Needle nose pliers
Slot head screw driver (2 required)
Wiring diagram

This procedure takes approximately 60 minutes to perform.

TROUBLESHOOTING & REPAIR

F-50 F-50

SQUARE WAVE TIG 275

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POLARITY SWITCH REMOVAL AND REPLACEMENT (continued)

FIGURE F.14 – NAMEPLATE REMOVAL

SQUARE WAVETIG 275

REMOTE

TO

WORK

ELECTRODE

WATER OUT
WATER IN

AMPERAGE

AC WAVE

BALANCE

POST FLOW

DOWN SLOPE

TIME

AMPS

VOLTS

THERMAL

PROTECTION

POWER

ON

OFF

CASE FRONT P ANEL

CONTROL
KNOBS

OUTPUT
CONTROL
KNOB

ALLEN
SCREW

NAMEPLA TE

POLARITY
SWITCH
HANDLE

SCREW

POLARITY
SWITCH

PROCEDURE

1. Remove the input power to the TIG 275
machine.

2. Using the 3/8” nut driver, remove the case
sides and top.

For Steps 3-8, see Figure F.14.

3. Using the 5/64” allen type wrench, remove the
output control knob.

4. Using the phillips head screw driver, remove
the screw from the polarity switch handle.

5. With the 2 slot head screw drivers, carefully
pry the polarity switch handle from the shaft.

6. Using the small slot head screw driver,
remove the three small control knobs.

7. Remove the seven plastic snap rivets holding
the nameplate to the case front.

8. Remove the nameplate.

TROUBLESHOOTING & REPAIR

F-51 F-51

SQUARE WAVE TIG 275

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POLARITY SWITCH REMOVAL AND REPLACEMENT (continued)

FIGURE F.15 – POLARITY SWITCH CONNECTIONS

253

X1

MICRO SWITCH
LEADS

B

POS

NEG

CHOKE

TROUBLESHOOTING & REPAIR

F-52 F-52

SQUARE WAVE TIG 275

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POLARITY SWITCH REMOVAL AND REPLACEMENT (continued)

FIGURE F.16 – POLARITY SWITCH WIRING DIAGRAM

232A

211A

R8

232

211B

211

B 232

211 X5

23VAC

212

X6

B 231

B X4

231B

115VAC

232B

B X3

W X8

W 204

18VAC

R 210

B X9
W X7

W 201

18VAC

W X10

W 209

H1

H2 (208V)

H3 (230V)

H4 (460V)

S
F

S
F

78VAC

X1

X2

E

F

D

B

C

B

A

X1

POS

B

FRONT GANG

POLARITY SWITCH MICRO SWITCH
AC A-C, D-E, B-F OPEN
DC+ B-D, C-E, A-F, G-H CLOSED
DC- B-D, A-E, C-F, G-H CLOSED

REAR GANG

MICRO-SWITCH

312

275C

NO

NC

D2

S2A

H

G

NEG

S2

POLARITY

SWITCH

(REAR VIEW, SHOWN

IN AC POSITION)

POS

(-)

SCR3

SCR4

D1

R7

X2

NEG

G1

G2

218

G3

217

220

220A

(+)

G4

216

L1

115VAC

CB

CB232C

C7

W 221

R 222

R6

253

252

BYPASS /

STABILIZER

PC BOARD

WORKELECTRODE

247

S

SPARK
GAP

F

ARC STARTER AS'BLY

115VAC

C5

L3

T2

L4

T1

SCR2

SCR1

T3

TROUBLESHOOTING & REPAIR

F-53 F-53

SQUARE WAVE TIG 275

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POLARITY SWITCH REMOVAL AND REPLACEMENT (continued)

For Steps 9--17, see Figure F.15 and F.16.

9. With the 1/2” wrench, remove the “POS” flex
lead from the polarity switch. See the Wiring
Diagram. Label lead and connection point
for reassembly.

10. With the 1/2” wrench, remove the “B” flex
lead from the polarity switch. This lead con­nects to the AC plate on the SCR bridge.
See Wiring Diagram. Label lead and con­nection point for reassembly.

11. Using the 1/2” wrench, remove the “NEG”

flex lead from the rear gang of the polarity
switch. This lead connects to the D1 diode
on the SCR bridge. See the Wiring Diagram.
Label lead and connection point for reassem­bly . Also label and remove the D2 diode heat
sink assembly.

12. Using the 1/2” wrench, remove the flex lead
from the polarity switch. This lead connects
to the high frequency transformer coil and
the by-pass board. See the Wiring Diagram.
Label lead and connection point for
reassembly. Also remove lead #252.

13. Using the 1/2” wrench, remove the other flex
lead from the polarity switch. This lead con­nects to the upper terminal on the by-pass
and the “work” output terminal lead. See the
Wiring Diagram. Label lead and connection
point for reassembly. Also remove lead
#253.

14. Using the 1/2” wrench, remove the choke
lead from the polarity switch. See the Wiring
Diagram. Label lead and connection point
for reassembly.

15. With the 1/2” wrench, remove the X1 sec­ondary lead from the polarity switch. See the
Wiring Diagram. Label lead and connection
point for reassembly.

16. Carefully unsolder the two leads (#275C and
#312) from the microswitch located on the
polarity switch assembly. See the Wiring
Diagram. Label leads and connections
points for reassembly.

17. Remove the cable tie that holds the thermal
protection light leads to the polarity switch.

18. With the 7/16” wrench, remove the two nuts
and washers that hold the polarity switch to
the front panel. See

Figure F.14.

19. Carefully remove the polarity switch assem­bly from the machine.

Replacement Procedure

Refer to Figures F.14 - F.16.

1. Mount the polarity switch to the front panel

with two nuts and washers.

2. Replace the cable tie holding the thermal pro-

tection light leads to the polarity switch.

3. Resolder leads #275C and #312 to the

microswitch.

4. Attach the following leads to the polarity

switch. See

Figures F.15 and F.16.

• X1 secondary lead

• choke lead

• #253 and flex lead

• #252 and flex lead

• NEG lead (at rear gang)

• POS lead

• B lead

5. Install the nameplate with 7 rivets.

6. Re-install and secure the three small plastic

control knobs.

7. Install the polarity switch handle with the

phillips head screw.

8. Install the output control knob with the allen

screw.

9. Install the case top and sides.

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TROUBLESHOOTING & REPAIR

F-54 F-54

SQUARE WAVE TIG 275

WARNING

MAIN TRANSFORMER AND OUTPUT CHOKE ASSEMBLY

REMOVAL AND REPLACEMENT

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

If for any reason you do not understand the test procedures or are unable to perform the
test/repairs safely, contact the Lincoln Electric Service Department for electrical troubleshoot­ing assistance before you proceed. Call 216-383-2531 or 1-800-833-9353 (WELD).

DESCRIPTION

This procedure will aid the technician in the removal and replacement of the main transformer
and choke assembly.

MATERIALS NEEDED

3/8” Nut driver
5/16” Nut driver
1/2” Wrench
Wire cutters
Molex extraction tool # HT60630B

This procedure takes approximately 2 hours to perform.

TROUBLESHOOTING & REPAIR

F-55 F-55

SQUARE WAVE TIG 275

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MAIN TRANSFORMER AND OUTPUT CHOKE ASSEMBLY

REMOVAL AND REPLACEMENT (continued)

FIGURE F.17 – PLUG J8 LOCATION ON CONTROL BOARD

S-W TIG 275 CONTROL

J8PIN 14 (LEAD #212)

PIN 12 (LEAD #232A)

PIN 9 (LEAD #209)

PIN 1 (LEAD #210)

PIN 2 (LEAD #231)

PIN 6 (LEAD #201)

PIN 4 (LEAD #204)

PIN 13 (LEAD #211A)

G3360-[ ]

PROCEDURE

1. Remove the input power to the TIG 275
machine.

2. Perform the

SCR Bridge Assembly Removal

Procedure.

3. Label and remove lead #232B from the circuit
breaker located on the case back.

4. Label and remove lead #231B from the recep­tacle located on the case back.

5. Remove Plug J8 from the control board. See
Figure F.17.

6. Using the mini-molex extraction tool, remove
the following six leads from plug J8. See
Figure F.17 for lead locations. Cut any nec­essary cable ties. Note lead and pin place­ment for reassembly.

#212, #201, #204, #209, #210, #231

7. Disconnect lead #232Aat the quick-connect.

8. Disconnect lead #211 at the quick-connect.

9. Feed the disconnected leads through the
internal baffle along with leads #232B and
231B.

TROUBLESHOOTING & REPAIR

F-56 F-56

SQUARE WAVE TIG 275

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MAIN TRANSFORMER AND OUTPUT CHOKE ASSEMBLY

REMOVAL AND REPLACEMENT (continued)

FIGURE F.18 – TRANSFORMER CONNECTIONS

SQUARE WAVETIG 275

LIFT BAIL
BAFFLE

GLASTIC CHOKE
BAFFLES

TRANSFORMER
MOUNTING
STUD (4)

CHOKE
LEAD

SCREW (2)

LEFT SIDE
INTERNAL
PANEL

H1 PRIMARY LEAD
CONNECTION AT
INPUT LINE SWITCH
(LOCATION)

SCREW (1)

TRANSFORMER
PRIMARY LEADS ­CONNECTION
POINTS

GLASTIC
RECONNECT
PANEL
(LEFT SIDE)

10. Using the 7/16” wrench, disconnect the
transformer primary leads from the recon­nect studs. See the Wiring Diagram and
Figure F.18. Label the leads for reassembly.

11. Using the 5/16” nut driver, remove the one
screw from the lower front corner of the glas­tic reconnect panel.

12. Remove the H1 capacitor lead from the
capacitor terminal.

13. Using the 5/16” nut driver, remove the four
screws from the glastic choke baffles.

14. Remove the glastic reconnect panel by lifting
up on the choke baffle and sliding the recon­nect panel away from the machine. (Clear
all leads.)

15. Clear the glastic choke baffle and associated
leads for transformer removal.

16. With the 3/8” wrench, disconnect the H1 pri­mary lead from the input line switch.

17. Using the 1/2” wrench, disconnect the choke
lead from the polarity switch. See the Wiring
Diagram and

Figure F.19.

Label for

reassembly.

18. Using the 1/2” wrench, disconnect the X1
transformer secondary lead from the polarity
switch. Label for reassembly. See

Figure

F.19

.

19. Using the 3/8” nut driver, remove the screw
holding the left side internal panel to the
metal lift bail baffle. See Figure F.18.

TROUBLESHOOTING & REPAIR

F-57 F-57

SQUARE WAVE TIG 275

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MAIN TRANSFORMER AND OUTPUT CHOKE ASSEMBLY

REMOVAL AND REPLACEMENT (continued)

20. Using the 3/8” wrench, remove the two
screws holding the left side panel to the base
of the machine. See

Figure F.18.

21. With the 1/2” wrench, disconnect the shunt
assembly from the choke lead.

22. Carefully slide the panel away from the
transformer about two inches.

23. Remove the left side choke glastic baffle.

24. Remove leads #314 and #316 from the
choke thermostat. See the Wiring Diagram.

25. Remove lead #315 and #316 from the X1
secondary lead thermostat. See the Wiring
Diagram.

26. Disconnect the primary thermostat lead
splices #313 and #315. See the Wiring
Diagram.

27. With the 9/16” wrench, remove the four nuts
from the transformer mounting studs. See

Figure F.18.

28. Carefully lift the transformer and choke
assembly from the machine base. Clear all
leads.

FIGURE F.19 – POLARITY SWITCH CONNECTIONS

253

X1

MICRO SWITCH
LEADS

B

POS

NEG

CHOKE

TROUBLESHOOTING & REPAIR

F-58 F-58

SQUARE WAVE TIG 275

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MAIN TRANSFORMER AND OUTPUT CHOKE ASSEMBLY

REMOVAL AND REPLACEMENT (continued)

Reassembly Procedure

Refer to Figures F.17 - F.19.

1. Set the transformer onto the four mounting
studs on the base. Attach the four nuts.

2. Connect the lead splices to the three ther­mostats:

• #313 and #315 to the primary thermostat.

• #315 and #316 to the X1 secondary ther­mostat

• #314 and #316 to the choke thermostat.

3. Attach the shunt assembly to the choke lead.

4. Attach the lead side panel to the base with
two screws.

5. Attach the left side panel to the metal lift bail
baffle.

6. Connect the X1 transformer lead and the
choke lead to the polarity switch.

7. Connect the H1 primary lead to the input line
switch.

8. Fit the choke baffle and glastic reconnect
panel together and attach them with screws.

9. Attach the H1 capacitor lead to the capacitor
terminal.

10. Connect the transformer primary leads to the
reconnect panel studs.

11. Feed the following leads through the internal

panel and attach them as follows:

• #211 and #232A at the quick-connects

• #231B to the receptacle

• 232B to the circuit breaker

• #212, #201, #204, #209, #210, #231 at
molex plug J8. See

Figure F.17.

• Install plug J8 into the control board.

12. Install necessary cable ties.

13. Perform the

SCR Bridge Assembly

reassembly procedure.

RETEST AFTER REPAIR

Should a machine under test be rejected for any reason requiring the removal of any mechanical part that could
affect the machine’s electrical characteristics, or if any electrical components are repaired or replaced, the machine
must be retested.

INPUT IDLE AMPS

Input Volts/Hertz Maximum Idle Amps Maximum Idle Amps

(without PFC) (with PFC)

208/60 5 38
230/60 4 35
460/60 2 18

OPEN CIRCUIT VOLTAGES

STICK MODE OCV AC 70 - 74 VAC

DC 56.5 - 61.5 VDC

TIG MODE OCV AC 70 - 76 VAC

DC 59 - 67 VDC

MAXIMUM ACCEPTABLE OUTPUT VOLTAGE -

AT MINIMUM OUTPUT SETTINGS

DC TIG Mode 5 Amps @ 13 Volts

MINIMUM ACCEPTABLE OUTPUT VOLTAGE -

AT MAXIMUM OUTPUT SETTING

DC TIG Mode 300 Amps @ 32 Volts

RECOMMENDED METERS FOR MACHINE OUTPUT TESTS

VOLTMETER: AC and DC True RMS Meter - Fluke 8922A or equivalent

AMMETER: Columbia Type AX AC or DC Tong Ammeter

IMPORTANT: IF OTHER TYPE METERS ARE USED, RESULTS MAY NOT BE ACCURATE.

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TROUBLESHOOTING & REPAIR

F-59 F-59

SQUARE WAVE TIG 275

NOTES

F-60 F-60

SQUARE WAVE TIG 275

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