MAINTENANCE MANUAL
F-15-099
January, 1994
L-TEC VI-450
WELDING POWER SOURCE
230/460/575 V ac, 60 Hz...P/N 33322
220/380/415 V ac, 50 Hz...P/N 33323
These INSTRUCTIONS are for experienced operators. If you are not fully familiar with the principles of operation
and safe practices for arc welding equipment, we urge you to read our booklet, "Precautions and Safe Practices
for Arc Welding, Cutting, and Gouging", Form 52-529. Do NOT permit untrained persons to install, operate, or
maintain this equipment. Do NOT attempt to install or operate this equipment until you have read and fully
understand these instructions. If you do not fully understand these instructions, contact your supplier for
further information. Be sure to read the Safety Precautions (Section 1) before installing or operating this
equipment.
Be sure this information reaches the operator.
You can get extra copies through your supplier.
USER RESPONSIBILITY
This equipment will perform in conformity with the description thereof contained in this manual and accom-
panying labels and/or inserts when installed, operated, maintained and repaired in accordance with the instructions
provided. This equipment must be checked periodically. Defective equipment should not be used. Parts that are
broken, missing, worn, distorted or contaminated should be replaced immediately. Should such repair or replace-
ment become necessary, the manufacturer recommends that a telephone or written request for service advice be
made to the Authorized Distributor from whom purchased.
This equipment or any of its parts should not be altered without the prior written approval of the manufac-
turer. The user of this equipment shall have the sole responsibility for any malfunction which results from improper
use, faulty maintenance, damage, improper repair or alteration by anyone other than the manufacturer or a service
facility designated by the manufacturer.
READ AND UNDERSTAND THESE INSTRUCTIONS ALONG WITH
THE SAFETY SECTIONS CONTAINED IN THIS MANUAL.
Protect yourself and others. Be sure this information reaches all operators.
ELECTRIC SHOCK can kill.
Do not touch live electrical parts or electrodes with bare skin or wear wet gloves or
wet clothing.
FUMES AND GASES can be dangerous to your health.
Keep your head out of the fumes. Use enough ventilation, exhaust at the arc, or
both, to keep fumes and gases from your breathing zone and the general area.
Where this cannot be done, use an air-supplied respirator.
If welding causes dizziness, nausea or respiratory irritation, ventilation is inade-
quate. See your supervisor. See special precautions in references below when
welding on materials containing or coated with lead, mercury, zinc, beryllium, cad-
mium, chromium, nickel or other materials with toxic properties.
ARC RAYS can injure eyes and burn skin.
Protect your eyes and body with proper welding helmet, safety glasses, eye filter
lenses, and dark protective clothing.
NOISE can damage hearing.
Wear proper hearing protection.
Read and understand these instructions and your employer's safety guidelines.
See American National Standard Z49.1, "Safety in Welding and Cutting", published by
the American Welding Society, P.O. Box 351040, Miami, Florida 33153; O.S.H.A. Safety
and Health Standards, 29 CFR 1910, available from U.S. Government Printing Office,
Washington, D.C. 20402, and the safety section in this manual.
i
2
L-TEC VI-450 Power Source
SECTION 1
SAFETY
1-1
1.1 Introduction
These safety precautions are for your protection. They
summarize precautionary information contained in the
references section below and as noted herein. Before
performing any installation or operating procedures, be
sure to read and follow the safety precautions listed
below as well as all other manuals, material safety data
sheets, labels, etc. Failure to observe safety precau-
tions can result in personal injury or death.
This symbol appearing throughout this
manual means “Attention! Be Alert! Your
safety is involved.”
The following definitions apply to WARNING and CAU-
TION symbols found throughout this manual:
USED TO CALL ATTENTION TO IMMEDIATE HAZ-
ARDS WHICH, IF NOT AVOIDED, WILL RESULT IN
IMMEDIATE, SERIOUS PERSONAL INJURY OR
LOSS OF LIFE.
USED TO CALL ATTENTION TO POTENTIAL HAZ-
ARDS WHICH COULD RESULT IN PERSONAL IN-
JURY OR LOSS OF LIFE.
USED TO CALL ATTENTION TO HAZARDS WHICH
COULD RESULT IN MINOR PERSONAL INJURY.
1.2 General
PROTECT YOURSELF AND OTHERS-Some weld-
ing, cutting, and gouging processes are noisy and
require ear protection. Skin and eye burns from arc
rays can be more severe than sunburn. Hot metal
can cause skin burns and heat rays may injure
eyes. Training in the proper use of the processes
and equipment is essential to prevent accidents.
• Always wear safety glasses with side shields in
any work area, even if a welding helmet, face
shield, or goggles are also required.
• Use a face shield fitted with the correct filter and
cover plates to protect your eyes, face, neck, and
ears from sparks and rays of the arc when
operating or observing operations. WARN by-
standers not to watch the arc and not to expose
themselves to the rays of the electric-arc or hot
metal.
• Wear flameproof gauntlet type gloves, heavy
long sleeve shirt, cuffless trousers, high-topped
shoes, and a welding helmet or cap for hair
protection, to protect against arc rays and hot
sparks or hot metal. A flameproof apron may
also be desirable as protection against radiated
heat and sparks.
• Hot sparks or metal can lodge in rolled up sleeves,
trouser cuffs, or pockets. Sleeves and collars
should be kept buttoned, and open pockets elimi-
nated from the front of clothing.
• Protect other personnel from arc rays and hot
sparks with a suitable non-flammable partition or
curtains.
• Use goggles over safety glasses while chipping
slag or grinding. Chipped slag may be hot and
can travel considerable distances. Bystanders
should also wear goggles over safety glasses.
1.3 Fire and Explosion
Heat from flames and arcs can act as ignition
sources. Hot slag or sparks can cause fire and
explosions.
• Hydrogen explosions can occur when using water
tables.
• Remove all combustible materials well away
from the work area or completely cover the
materials with a protective non-flammable cover-
ing. Combustible materials include wood, cloth,
sawdust, liquid and gas fuels, solvents, paints
and coatings, paper, etc.
• Hot sparks or hot metal can fall through cracks or
crevices in floors or wall openings and cause a
hidden smoldering fire or fires on the floor below.
Make certain that such openings are protected
from hot sparks and metal.
3
L-TEC VI-450 Power Source
SECTION 1
SAFETY
1-2
connection could expose the operator or others
in the area to a fatal shock.
• Do not use worn or damaged cables. Do not
overload the cable. Use well maintained equip-
ment.
• When not operating, turn off the equipment.
Accidental overloading can cause overheating
and create a fire hazard. Do not coil or loop cable
over parts of the body.
• Be sure the proper size ground cable is con-
nected to the workpiece as close to the work area
as possible. Grounds connected to building
framework or other remote locations from the
work area increase the possibility of output cur-
rent passing through lifting chains, crane cables,
or various electrical parts.
• Keep clothing, controls, and power source dry.
Fix water leaks immediately (after shutting off
power).
• Refer to ANSI/ASC Standard Z49.1 (see listing
below) for specific grounding recommendations.
Do not mistake the work cable for a grounding
cable.
1.5 Fumes and Gases
Fumes and gases can cause discomfort and/or
harm, particularly in confined spaces. Do not
breathe fumes and gases. Shielding gases can
cause asphyxiation.
• Always provide adequate ventilation in the work
area by natural or mechanical ventilation means.
Do not weld, cut, or gouge on materials such as
galvanized steel, stainless steel, copper, zinc,
lead, beryllium, or cadmium unless positive me-
chanical ventilation is provided. Do not breathe
fumes and gases from these materials.
• Do not operate in locations close to chlorinated
hydrocarbon vapors coming from degreasing
and spraying operations. The heat or arc rays
can react with solvent vapors to form phosgene,
a highly toxic gas, and other irritant gases.
• If you develop momentary eye, nose, or throat
irritations while operating, this is an indication
that ventilation may not be adequate. Stop work
and take necessary steps to improve ventilation
• Do not weld, cut, or perform other hot work until
the workpiece has been completely cleaned so
that there are no substances on the workpiece
which might produce flammable or toxic vapors.
Do not do hot work on closed containers. They
may explode.
• Have fire extinguishing equipment handy for
instant use, such as a garden hose, water pail,
sand bucket, or portable fire extinguisher. Be
sure you are trained in its use.
• After completing operations, inspect the work
area to make certain there are no hot sparks or
hot metal which could cause a later fire. Use fire
watchers when necessary.
• For additional information refer to NFPA stan-
dard 51B, “Fire Prevention in Use of Cutting and
Welding Processes”, which is available from the
National Fire Protection Association,
Batterymarch Park, Quincy, MA 02269.
1.4 Electrical Shock
Contact with live electrical parts can cause severe
burns to the body or fatal shock. Severity of
electrical shock is determined by the path and
amount of current through the body. The higher
the voltage, the greater the hazard.
• Never allow live metal parts to touch bare skin or
any wet clothing. Be sure gloves are dry.
• When standing on metal or operating in a damp
area, make certain that you are well insulated.
Wear dry gloves and rubber-soled shoes and
stand on a dry board or platform.
• Do not stand on the plate or parts being cut during
the cutting process.
• Do not touch the plate or pick up cut parts while
cutting is in progress.
• Always ground the power source by connecting
a ground wire between the power source and the
ground system of the input power.
• Always make sure that the workpiece is con-
nected to a good earth ground.
• It is especially important with plasma cutting
equipment to be sure that the work cable is
connected to the workpiece. A poor or missing
4
L-TEC VI-450 Power Source
SECTION 1
SAFETY
1-3
in the work area. Do not continue to operate if
physical discomfort persists.
• Refer to ANSI/ASC Standard Z49.1 for specific
ventilation recommendations.
1.6 Equipment Maintenance
Faulty or improperly maintained equipment can
result in poor work, but more importantly, it can
cause physical injury or death through fires or
electrical shock.
• Always have qualified personnel perform the
installation, troubleshooting, and maintenance
work. Do not perform any electrical work unless
you are qualified to perform such work.
• Before performing any maintenance work inside
a power source, disconnect the power source
from the electrical power supply.
• Maintain cables, grounding wire, connections,
power cord, and power source in safe working
order. Do not operate any equipment in faulty
condition.
• Do not abuse any equipment or accessories.
Keep equipment away from heat sources such
as furnaces, wet conditions such as water
puddles, oil or grease, corrosive atmospheres
and inclement weather.
• Keep all safety devices and cabinet covers in
position and in good repair.
• Use equipment for its intended purpose. Do not
modify it in any manner.
1.7 Cylinders
Cylinders, if mishandled, can rupture and violently
release gas. Sudden rupture of cylinder, cylinder
valve, or relief device can injure or kill.
• Use the proper gas for the process and use the
proper pressure reducing regulator designed to
operate from the compressed gas cylinder. Do
not use adapters. Maintain hoses and fittings in
good condition. Follow manufacturer’s operating
instructions for mounting regulator to a com-
pressed gas cylinder.
• Always secure cylinders in an upright position by
chain or strap to suitable handtrucks, undercar-
riages, benches, walls, post, or racks. Never
secure cylinders to work tables or fixtures where
they may become part of an electrical circuit.
• When not in use, keep cylinder valves closed.
Have valve protection cap in place if not con-
nected for use. Secure and move cylinders by
using suitable hand trucks. Avoid rough handling
of cylinders.
• Locate cylinders away from heat, sparks, or
flame of a welding, cutting, or gouging operation.
Never strike an arc on a cylinder.
• For additional information, refer to CGA Stan-
dard P-1, “Precautions for Safe Handling of
Compressed Gases in Cylinders”, which is avail-
able from Compressed Gas Association, 1235
Jefferson Davis Highway, Arlington, VA 22202.
1.8 References
For more information on safe practices for setting up
and operating electric welding and cutting equipment
and on good working habits, ask your ESAB supplier for
a copy of “Precautions and Safe Practices for Electric
Welding and Cutting”, Form 52-529.
The following publications, which are available from the
American Welding Society, 550 LeJuene Road, Miami,
FL 33126, are recommended to you:
• ANSI/ASC Z49.1 - “Safety in Welding and Cut-
ting”
• AWS C5.1 - “Recommended Practices for
Plasma Arc Welding”
• AWS C5.2 - “Recommended Practices for
Plasma Arc Cutting”
• AWS C5.3 - “Recommended Practices for Air
Carbon Arc Gouging and Cutting”
• AWS C5.5 - “Recommended Practices for Gas
Tungsten Arc Welding”
• AWS C5.6 - “Recommended Practices for Gas
Metal Arc Welding”
• AWS SP - “Safe Practices” - Reprint, Welding
Handbook.
5
L-TEC VI-450 Power Source
SECTION 2
MAINTENANCE
2-1
2.1 General
If this Power Source does not operate properly, stop
work immediately and investigate the cause of the
malfunction. Maintenance work must be performed by
an experienced person, and electrical work by a trained
electrician. Do not permit untrained persons to inspect,
clean, or repair this Power Source. Use only recom-
mended replacement parts.
BE SURE THAT THE BRANCH CIRCUIT OR MAIN
DISCONNECT SWITCH IS OFF, OR ELECTRICAL
INPUT FUSES ARE REMOVED, BEFORE ATTEMPT-
ING ANY INSPECTION OR WORK INSIDE THE
POWER SOURCE. PLACING THE POWER SWITCH
IN THE OFF POSITION DOES NOT REMOVE ALL
POWER FROM INSIDE THE POWER SOURCE.
2.2 Cleaning
Periodically, remove the cover from the Power Source
and blow accumulated dust and dirt from the air pas-
sages and interior components by using clean low
pressure air. The frequency of cleaning required de-
pends upon the environment in which the Power Source
is used.
It is imperative that all air passages be kept as clean as
possible in order to allow adequate air flow to provide
proper cooling.
After cleaning with low pressure air, check for and
tighten any loose hardware, including all electrical
connections. Check for frayed and/or cracked insula-
tion on all power cables and replace if necessary.
FAILURE TO REPLACE WORN OR DAMAGED
CABLES MAY RESULT IN A BARE CABLE TOUCH-
ING A GROUND SURFACE. THE RESULTING ELEC-
TRICAL ARC MAY DAMAGE UNPROTECTED EYES
AND WILL PRESENT A SERIOUS FIRE HAZARD.
BODY CONTACT WITH A BARE CABLE, CONNEC-
TOR, OR CONDUCTOR MAY RESULT IN SEVERE
ELECTRICAL SHOCK, CAUSING SERIOUS BURNS
OR DEATH.
2.3 Inspection and Service
Regularly, check cylinder valves, regulators, hoses,
and gas connections for leaks using a soap solution or
a leak test solution.
Keep the Power Source dry, free of oil and grease, and
protected at all times from damage by hot metal and
sparks.
2.3.1 Fan Motor
Keep the fan motor free of accumulated dust and lint by
using low pressure air. Lubricate the motor every three
months with a few drops of SAE-20 non-detergent oil.
2.3.2 Transformer
Other than periodically cleaning the dust and dirt from
the transformer as described above, no maintenance is
required. Ensure that only clean, dry, low-pressure air
is used.
2.3.4 Wire Feeder and Control Circuits
These circuits are protected by two 10 amp fuses
mounted in the rear panel fuse holder (CB1, 2). If these
fuses fail, the contactor, shielding gas, and wire feeder
will not operate.
When replacing a fuse in the welding Power Source,
ensure that the proper size fuse is used as a
replacement.
2.3.5 Over-Temperature Protection
If the Power Source reaches an abnormally high inter-
nal temperature, the thermal protection relay will
deenergize, shutting down the Power Source but leav-
ing the cooling fan on. After the Power Source has
cooled to a safe level, this relay will be energized and
normal operation will be restored. While deenerigized,
the contactor, shielding gas, and wire feeder cannot be
operated.
6
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-1
3.1 General
DISCONNECT PRIMARY POWER AT WALL
SWITCH, OR CIRCUIT BREAKER, BEFORE AT-
TEMPTING INSPECTION OR WORK INSIDE THE
POWER SOURCE.
If the Power Source is operating improperly, the follow-
ing troubleshooting information may be used to locate
the source of the trouble.
Check the problem against the symptoms in the follow-
ing troubleshooting guide. The remedy for the problem
may be quite simple. If the cause cannot be quickly
located, open up the unit and perform a simple visual
inspection of all the components and wiring. Check for
proper terminal connections, loose or burned wiring or
components, blown fuses, bulged or leaking capaci-
tors, or any other sign of damage or discoloration.
3.2 Testing and Replacing Bridge Assem-
bly Components
The silicon diodes and SCRs used in the Power Source
are devices which allow current to flow in only one
direction. The diodes and SCRs are designed to
provide long trouble-free operation; however, should a
failure occur, they may require replacement.
A. Testing SCRs.
1. Locate the main rectifier assembly containing
the silicon diodes and SCRs.
2. Remove top and right side panel from the
Power Source.
3. Electrically isolate main bridge assembly by
disconnecting the capacitor bank and resistor
R5.
4. With the ohmmeter on RX1 scale, place the
positive lead on the anode (end of SCR with
screw threads) and the negative lead on the
cathode (positive output terminal on the front
panel). The meter should read 30-50 ohms
(high resistance).
5. Reverse leads and check each SCR. All
readings should again show high resistance.
The SCRs are bad if they show low resistance
in either direction.
6. Check the gate circuit on the SCRs by jumpering
the gate lead to the anode of the SCR. The
meter should read less than 5 ohms. Remove
the jumper from the gate. The meter reading
should increase (30-50 ohms).
When replacing diodes on SCRs, make sure mount-
ing surfaces are clean. Coat mounting surfaces
with Alcoa No. 2 EJC Electrical Joint Compound.
Use a torque wrench to tighten diodes and SCRs.
Recommended torques are 20-30 in-lbs for diodes;
125-150 in-lbs for SCRs.
7
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-2
Table 3-1. PCB Voltage Tests*
NOTE
All voltage readings are taken with the front access
panel open.
ELECTRICAL SERVICE AND REPAIR SHOULD BE
ATTEMPTED ONLY BY A TRAINED ELECTRICIAN.
SCR VOLTAGES (INPUT)
FROM TO READING
P1-8 P1-9 115 V ac
P2-8 (SCR1)
P2-7 (SCR2)
P2-3 (SCR3)
P2-6 (SCR4)
P2-1 (SCR5)
P2-4 (SCR6)
OTB+ (Flat) 14 V ac
SCR VOLTAGES (OUTPUT)
FROM TO READING
P1-11 OTB+ (Flat) +10 V dc
P1-4 OTB+ (Flat) 0-10 V dc**
P2-5 (SCR1)
P2-2 (SCR2)
P2-12 (SCR3)
P2-9 (SCR4)
P2-10 (SCR5)
P2-11 (SCR6)
OTB+ (Flat) .3 V dc with
contactor on
*Refer to Schematic Diagram
**Varies with VCP (R1)
8
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-3
9
Table 3-2. Troubleshooting Guide
CONDITION ACTION
Unit inoperative A.
B.
C.
D.
E.
F.
No input power. Check main line (user's) switch fuses -- replace if needed.
Poor or improper input (terminal board) connections.
Defective ROS switch on front panel -- replace.
Main transformer overheating. Also check for proper cooling, proper primary
hookup, or shorted turn on secondary.
Fan motor not operating -- check motor and leads. Remember, this is normal when
the thermal fan control circuit is activated.
Main contactor defective -- check for proper operation.
No Output -- Fan
Running
A.
B.
C.
D.
E.
Poor or improper electrical input -- check input connections on TB.
Poor connections at output terminals/work station -- check, tighten or replace.
Main transformer overheating -- thermal switches tripped due to restricted cooling
air. Let unit cool down.
Solid-state breaker tripped due to current overload.
PC board defective or loose PC board connector(s) -- if loose, reinsert; if defective,
replace.
Limited Output or Low
Open-Circuit Voltage
A.
B.
C.
D.
Input voltage jumper links on terminal board improperly set -- check for proper
voltage.
Poor output connections. Take apart, clean, and reassemble.
Unit may be single-phasing -- check incoming power for three phases.
Panel-Remote switch in Remote position and remote voltage pot disabled.
Erratic Weld Current A.
B.
C.
D.
E.
F.
Welding cable size too small -- use correct cables.
Loose welding cable connection (will usually get hot) -- tighten all connections.
Improper wire feeder setup.
Defective SCR in bridge rectifier.
PC board defective -- replace.
Unit may be single phasing -- check the incoming power for three phases.
High Output, No
Voltage Control
PC board defective or loose -- reset and/or replace board.
No 115 Volt ac Output A.
B.
Check secondary of control transformer (T2) for 115 V ac.
Circuit breaker tripped -- reset.
Line Fuse Blows When
Power Source is First
Turned On
A.
B.
Shorted SCR in Main Bridge -- replace.
Shorted capacitor in Capacitor Bank.
Wire Sparks and
Sticks to Workpiece at
End of Weld
A.
B.
Allow 2 to 4 seconds for capacitor banks to discharge after completing the weld and
before touching wire to workpiece.
If doubling the discharge rate is desired (twice as fast) and the thermal fan circuit is
not activated (generate excessive heat), change R5 (16 ohm, 300 watt) resistor to 8
ohm, 300 watt resistor (P/N 17300008). To quadruple the discharge rate (four
times as fast), two 8 ohm resistors may be connected in parallel in place of R5.
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-4
10
Figure 3-1. L-TEC VI-450 Power Source Schematic Diagram - 60 Hz (Sheet 1 of 2)
NOTE: Recent modifications to the power source may not be reflected in this
schematic. For up-to-date information on your model, refer to the schematic
on the inside cover of the power source or contact the factory.
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-5
Figure 3-1. L-TEC VI-450 Power Source Schematic Diagram - 60 Hz (Sheet 2 of 2)
11
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-6
12
Figure 3-2. L-TEC VI-450 Power Source Wiring Diagram - 60 Hz (Sheet 1 of 4)
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-7
Figure 3-2. L-TEC VI-450 Power Source Wiring Diagram - 60 Hz (Sheet 2 of 4)
13
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-8
Figure 3-2. L-TEC VI-450 Power Source Wiring Diagram - 60 Hz (Sheet 3 of 4)
14
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-9
15
Figure 3-2. L-TEC VI-450 Power Source Wiring Diagram - 60 Hz (Sheet 4 of 4)
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-10
Figure 3-3. L-TEC VI-450 Power Source Schematic Diagram - 50 Hz (Sheet 1 of 2)
16
NOTE: Recent modifications to the power source may not be reflected in this
schematic. For up-to-date information on your model, refer to the schematic
on the inside cover of the power source or contact the factory.
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-11
Figure 3-3. L-TEC VI-450 Power Source Schematic Diagram - 50 Hz (Sheet 2 of 2)
17
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-12
18
Figure 3-4. L-TEC VI-450 Power Source Wiring Diagram - 50 Hz (Sheet 1 of 4)
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-13
Figure 3-4. L-TEC VI-450 Power Source Wiring Diagram - 50 Hz (Sheet 2 of 4)
19
L-TEC VI-450 Power Source
SECTION 3
TROUBLESHOOTING
3-14
20
Figure 3-4. L-TEC VI-450 Power Source Wiring Diagram - 50 Hz (Sheet 3 of 4)
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