Safety Requirements for Arc Welding Equipment part 1: EN 60974-1: 1990
Arc Welding Equipment Part 1: Welding Power Sources: IEC 974-1
(April 1995 – Draft revision)
Degrees of Protection provided by Enclosures (IP code): IEC 529: 1989
Insulation coordination for equipment within low-voltage systems:
Part 1: Principles, requirements and tests: IEC 664-1: 1992
Electromagnetic compatibility (EMC) Product standard for arc welding equipment:
EN50199: August 1995
European Contact:Mr. Luigi Vacchini, Managing Director
MILLER Europe S.P.A.
Via Privata Iseo
20098 San Giuliano
Milanese, Italy
Telephone:39(02)98290-1
Fax:39(02)98281-552
dec_con1 10/95
SECTION 1 – SAFETY PRECAUTIONS FOR SERVICING
1-1.Symbol Usage
safety_stm1 4/95
Means Warning! Watch Out! There are possible hazards with this
procedure! The possible hazards are shown in the adjoining symbols.
This group of symbols means Warning! Watch Out! possible ELECTRIC SHOCK, MOVING P ARTS,
and HOT P ARTS hazards. Consult symbols and related instructions below for necessary actions to
avoid the hazards.
Y Marks a special safety message.
. Means NOTE; not safety related.
1-2.Servicing Hazards
WARNING
The symbols shown below are used throughout this manual to call attention to and identify possible
hazards. When you see the symbol, watch out, and follow the related instructions to avoid the hazard.
Only qualified persons should service, test, maintain, and repair this unit.
During servicing, keep everybody, especially children, away.
ELECTRIC SHOCK can kill.
1. Do not touch live electrical parts.
2. Stop engine or turn OFF welding power source and
wire feeder, and disconnect and lockout input
power using line disconnect switch, circuit
breakers, or by removing plug from receptacle
before servicing unless the procedure specifically
requires an energized unit.
3. Insulate yourself from ground by standing or
working on dry insulating mats big enough to
prevent contact with the ground.
4. Do not leave live unit unattended.
5. When testing a live unit, use the one-hand method.
Do not put both hands inside unit. Keep one hand
free.
6. Disconnect input power conductors from
deenergized supply line BEFORE moving a
welding power source.
SIGNIFICANT DC VOLTAGE exists after
removal of input power on inverters.
7. Turn Off inverter, disconnect input power, and
discharge input capacitors according to
instructions in Maintenance Section before
touching any parts.
STATIC ELECTRICITY can damage
parts on circuit boards.
1. Put on grounded wrist strap BEFORE handling
boards or parts.
2. Use proper static-proof bags to store, move, or ship
PC boards.
FIRE OR EXPLOSION can result from
placing unit on, over, or near
combustible surfaces.
1. Do not place unit on, over, or near combustible
surfaces.
2. Do not service unit near flammables.
FLYING PIECES OF METAL or DIRT can
injure eyes.
1. Wear safety glasses with side shields or face shield
during servicing.
2. Be careful not to short metal tools, parts, or wires
together during testing and servicing.
HOT PARTS can cause severe burns.
1. Do not touch hot parts bare handed.
2. Allow cooling period before servicing welding gun
or torch.
EXPLODING PARTS can cause injury.
1. Failed parts can explode or cause other parts to
explode when power is applied to inverters.
2. Always wear a face shield and long sleeves when
servicing inverters.
ELECTRIC SHOCK HAZARD from
incorrect use of test equipment.
1. Turn Off welding power source and wire feeder or
stop engine before making or changing meter lead
connections.
2. At least one meter lead should be a self-retaining
spring clip such as an alligator clamp.
3. Read instructions for test equipment.
HIGH-FREQUENCY RADIATION can
interfere with radio navigation, safety
services, computers, and
communications equipment.
1. Have only qualified persons familiar with electronic
equipment perform this installation.
2. The user is responsible for having a qualified
electrician promptly correct any interference
problem resulting from the installation.
3. If notified by the FCC about interference, stop using
the equipment at once.
4. Have the installation regularly checked and
maintained.
5. Keep high-frequency source doors and panels
tightly shut, keep spark gaps at correct setting, and
use grounding and shielding to minimize the
possibility of interference.
TM-353 Page 1Syncrowave 250
FALLING EQUIPMENT can cause
serious personal injury and equipment
damage.
1. Use lifting eye to lift unit only, NOT running gear,
gas cylinders, or any other accessories.
2. Use equipment of adequate capacity to lift unit.
MAGNETIC FIELDS FROM HIGH
CURRENTS can affect pacemaker
operation.
1. Pacemaker wearers keep away from servicing
areas until consulting your doctor.
MOVING PARTS can cause injury.
1. Keep away from moving parts such as fans.
2. Keep all doors, panels, covers, and guards closed
and securely in place.
1-3.EMF Information
MOVING PARTS can cause injury.
1. Keep away from moving parts.
2. Keep away from pinch points such as drive rolls.
OVERUSE can cause OVERHEATED
EQUIPMENT.
1. Allow cooling period.
2. Reduce current or reduce duty cycle before
starting to weld again.
3. Follow rated duty cycle.
READ INSTRUCTIONS.
1. Use MILLER Testing Booklet (Part No. 150 853)
when servicing this unit.
2. Consult the Owner ’s Manual for welding safety
precautions.
3. Use only genuine MILLER replacement parts.
Considerations About Welding And The Effects Of Low Frequency
Electric And Ma g netic Fields
The following is a quotation from the General Conclusions Section of
the U.S. Congress, Office of Technology Assessment, Biological
Effects of Power Frequency Electric & Magnetic Fields – Background
Paper, OTA-BP-E-53 (Washington, DC: U.S. Government Printing
Office, May 1989): “. . . there is now a very large volume of scientific
findings based on experiments at the cellular level and from studies
with animals and people which clearly establish that low frequency
magnetic fields can interact with, and produce changes in, biological
systems. While most of this work is of very high quality , the results are
complex. Current scientific understanding does not yet allow us to
interpret the evidence in a single coherent framework. Even more
frustrating, i t does not yet allow us to draw definite conclusions about
questions of possible risk or to offer clear science-based advice on
strategies to minimize or avoid potential risks.”
To reduce magnetic fields in the workplace, use the following
procedures:
1. Keep cables close together by twisting or taping them.
2. Arrange cables to one side and away from the operator.
3. Do not coil or drape cables around the body.
4. Keep welding power source and cables as far away as
practical.
5. Connect work clamp to workpiece as close to the weld as
possible.
About Pacemakers:
The above procedures are also recommended for pacemaker
wearers. Consult your doctor for complete information.
TM-353 Page 2Syncrowave 250
SECTION 2 – DEFINITIONS
2-1.Warning Label Definitions
11.11.2
2
33.13.23.3
44.1
2.1
+
2.2
2.3
+
+
1.3
Warning! Watch Out! There are
possible hazards as shown by the
symbols.
1Electric shock from welding
electrode or wiring can kill.
1.1 Wear dry insulating gloves.
Do not touch electrode with
bare hand. Do not wear wet or
damaged gloves.
1.2 Protect yourself from electric
shock by insulating yourself
from work and ground.
1.3 Disconnect input plug or
power before working on
machine.
2Breathing welding fumes can
be hazardous to your health.
2.1 Keep your head out of the
fumes.
2.2 Use forced ventilation or local
exhaust to remove the fumes.
2.3 Use ventilating fan to remove
fumes.
3Welding sparks can cause
explosion or fire.
3.1 Keep flammables away from
welding. Don’t weld near
flammables.
3.2 Welding sparks can cause
fires. Have a fire extinguisher
nearby and have a watch
person ready to use it.
3.3 Do not weld on drums or any
closed containers.
4Arc rays can burn eyes and
injure skin.
4.1 Wear hat and safety glasses.
Use ear protection and button
shirt collar. Use welding
helmet with correct shade of
filter. Wear complete body
protection.
5Become trained and read the
instructions before working on
the machine or welding.
With
PFC55(57*)64(51*)48(49*)48(49*)37(30*)34(27*)24(25*)48(49*)19(20*)11(11*)
PFC**
No
PFC
With
PFC
200V220V230V260V380V415V460V520V575
**
No
SECTION 3 – INSTALLATION
Amperes Input at AC Balanced
Rated Load Output,
50/60 Hz, Single-Phase
200 V230 V460 V575 V
106
(4.6*)
7666332615.211.4
92
(4*)
46
(2*)
37
(1.6*)21(0.89*)
Amperes Input at AC Balanced
Rated Load Output,
50/60 Hz, Single-Phase
KVAKW
11.4
(0.68*)
V
KVAKW
Amp
Range
5–310 A80 V21
8.3
(0.7*)
8.3
(0.6*)
Max
OCV
Amp
Range
5–310 A80 V21
Rating
Max
OCVIPRating
IP
3-2.Volt-Ampere Curves
A. DC Mode
The volt-ampere curves show the
minimum and maximum voltage
and amperage output capabilities of
the welding power source. Curves
of other settings fall between the
curves shown.
B. AC Mode
ssb1.1 10/91 – SB-116 199 / SB-116 200
TM-353 Page 6Syncrowave 250
3-3.Duty Cycle And Overheating
40% Duty Cycle At 250 Amperes (60 Hz Models Only)
4 Minutes Welding6 Minutes Resting
Duty Cycle is percentage of 10 mi n utes that unit can weld at rated load
without overheating.
If unit overheats, thermostat opens,
output stops, light goes on (CE
models only), and cooling fan runs.
Wait fifteen minutes for unit to cool.
Reduce amperage or duty cycle before welding.
Y Exceeding duty cycle can
damage unit and void
warranty.
Overheating
60% Duty Cycle At 200 Amperes
6 Minutes Welding4 Minutes Resting
0
15
Minutes
A
OR
Reduce Duty Cycle
duty1 4/95 / SB-116 198
TM-353 Page 7Syncrowave 250
3-4.Selecting A Location
Movement
Location And Airflow
3
5
1Lifting Eye
2Lifting Forks
Use lifting eye or lifting forks to
move unit.
1
OR
2
6
4
18 in (460
mm)
If using lifting forks, extend forks
beyond opposite side of unit.
3Rating Label (Non CE Models
Only)
4Rating Label (CE Models
Only, See Section 2-2)
Use rating label to determine input
power needs. CE label located on
rear panel.
5Plate Label (CE Models Only)
6Line Disconnect Device
Locate unit near correct input pow-
er supply.
Y Special installation may be
required where gasoline or
volatile liquids are present –
see NEC Article 511 or CEC
Section 2 0 .
18 in (460
mm)
3-5.Dimensions And Weights
A
B
C
Front
ST-800 402 / ST-117 264-F
Dimensions
Height30-3/4 in (781 mm)
D
E
F
F
G
Width19-3/4 i n (502 mm)
Length27-1/2 i n (698 mm)
A27 in (686 mm)
B26 in (661 mm)
C25-1/4 i n (642 mm)
D1-1/2 in (38 mm)
E1-1/8 (29 mm)
F17-7/8 (454 mm)
G19-1/4 (489 mm)
H1/2 in (13 mm) Dia
6 Holes
H
TM-353 Page 8Syncrowave 250
ST-154 792-B
Weight
355 lbs (161 kg)
3-6.Tipping
Y Be careful when placing or
moving unit over uneven
surfaces.
3-7.Weld Output Terminals And Selecting Cable Sizes
Y ARC WELDING can cause Electromagnetic Interference.
To reduce possible interference, keep weld cables as short as possible, close together, and down low, such as on the floor.
Locate welding operation 100 meters from any sensitive electronic equipment. Be sure this welding machine is installed
and grounded according to this manual. If interference still occurs, the user must take extra measures such as moving
the welding machine, using shielded cables, using line filters, or shielding the work area.
Total Cable (Copper) Length In Weld Circuit Not Exceeding
Weld Output
Terminals
100 ft (30 m) Or Less
Welding
Amperes
1004443211/01/0
15033211/02/03/03/0
2003211/02/03/04/04/0
250211/02/03/04/02-2/02-2/0
30011/02/03/04/02-2/02-3/02-3/0
10 – 60%
Duty
Cycle
60 – 100%
Duty
Cycle
150 ft
(45 m)
200 ft
(60 m)
250 ft
(70 m)
300 ft
(90 m)
10 – 100% Duty Cycle
350 ft
(105 m)
400 ft
(120 m)
3501/02/03/04/02-2/02-3/02-3/02-4/0
ElectrodeWork
ST-154 795-C
Weld cable size (AWG) is based on either a 4 volts or less drop or a current density of at least 300 circular mils per ampere. Contact your distributor for the mm2 equivalent weld cable sizes.S-0007-E
4001/02/03/04/02-2/02-3/02-4/02-4/0
5002/03/04/02-2/02-3/02-4/03-3/03-3/0
TM-353 Page 9Syncrowave 250
3-8.Remote 14 Receptacle
F
Socket*Socket Information
A24 volts ac.
AJ
K
B
L
C
D
*The remaining sockets are not used.
I
NH
M
G
F
E
ST-154 795-C
BContact closure to A completes 24 volts ac contactor control
CCommand reference; 0 to +10 volts dc output to remote control.
DRemote control circuit common.
A
E0 to +10 volts dc input command signal from remote control.
KChassis common.
circuit.
3-9.115 Volts AC Duplex Receptacle And Shielding Gas Connections
Y Turn Off power before
connecting to receptacle.
1115 V AC Receptacle
5
6
17
4
Receptacle is protected from overload by circuit breaker CB1 (see
Section 7-2).
2Gas Valve In Fitting
3Gas Valve Out Fitting
Fittings have 5/8-18 right-hand
threads
4Cylinder Valve
Open valve slightly so gas flow
blows dirt from valve. Close valve.
5Regulator/Flow Gauge
6Flow Adjust
Typical flow rate is 20 cfh (cubic feet
per hour) (9.4 L/min)
7High Frequency Control (see
Section 4-1)
32
Ref. ST-154 795-C / Ref. ST-157 858
TM-353 Page 10Syncrowave 250
3-10. Electrical Service Guide
NOTE
60 Hertz Models
Input Voltage
Input Amperes At Rated Output
Max Recommended Standard Fuse Or Circuit
Breaker Rating In Amperes
Min Input Conductor Size In AWG/Kcmil
Max Recommended Input Conductor Length
In Feet (Meters)
Min Grounding Conductor Size In AWG/Kcmil
Reference: 1996 National Electrical Code (NEC)S-0092-J
50 Hertz ModelsWithout Power Factor Correction
Input Voltage
Input Amperes At Rated Output
All values calculated at 60% duty cycle.
Without Power Factor
Correction
200230460575200230460575
8574373055482419
125110604580703530
461010881214
173
(53)
661010881214
220260380415520220380415
7765454133643734
158
(48)
291
(89)
455
(139)
With Power Factor Correction
86
(26)
114
(35)
186
(58)
189
(48)
With Power Factor
Correction
Max Recommended Standard Fuse Or Circuit
Breaker Rating In Amperes
Min Input Conductor Size In AWG/Kcmil
Max Recommended Input Conductor Length
In Feet (Meters)
Min Grounding Conductor Size In AWG/Kcmil
Reference: 1996 National Electrical Code (NEC)S-0092-J
125100706050906050
66881061010
145
(44)
68810106810
202
(62)
291
(89)
347
(106)
372
(113)
145
(44)
291
(89)
347
(106)
TM-353 Page 11Syncrowave 250
3-11. Placing Jumper Links And Connecting Input Power
230 VOLTS460 VOLTS200 VOLTS
LLLLLL
S-083 566-C
230 VOLTS
LL
220 VOLTS
LL
260 VOLTS
LL
460 VOLTS
LL
380 VOLTS
LL
380 VOLTS
LL
1
575 VOLTS
LL
S-010 587-B
415 VOLTS
LL
S-131 783-A
520 VOLTS
LL
S-047 672-A
Connect GND/PE
Conductor First
Check input voltage available at
site.
1Jumper Link Label
Check label inside your unit–
only one label is on unit.
Y Only make connections for
the voltages shown on the label inside your unit. Do not
make connections for any
other voltages. If jumper link
label is missing from inside
2
unit, check rating label (see
Section 3 - 4 ) f o r a l lowable i nput voltages.
2Jumper Links
Move jumper links to match input
voltage.
3Input And Grounding
Conductors
Select size and length using
Section 3-10.
4Line Disconnect Device
Select type and size of overcurrent
protection using Section 3-10.
Reinstall side panel.
Y Special installation may be
required where gasoline or
volatile liquids are present –
see NEC Article 511 or CEC
Section 2 0 .
Tools Needed:
GND/PE
Earth Ground
4
L1 (U)
L2 (V)
3
Connect GND/PE
Conductor First
3/8 in
3/8, 1/2, 7/16 in
ST-117 263-K
TM-353 Page 12Syncrowave 250
4-1.Controls
6
5
4
3
2
SECTION 4 – OPERATION
1Ammeter
87
9
10
11
12
13
14
1
See Section 4-3.
2Voltmeter
See Section 4-3.
3High Frequency Switch
See Section 4-11.
4Output (Contactor) Switch
See Section 4-8.
5Spot Time Switch And Control
(Optional)
See Section 4-5.
6Preflow Time Control (Optional)
See Section 4-12.
7AC Balance Control
See Section 4-6.
8Crater Time Control And Switch
See Section 4-4.
9Amperage Adjustment Control And
Switch
See Section 4-7.
10 Arc Force (Dig) Switch And Control
See Section 4-9.
11 Postflow Time Control
See Section 4-10.
12 High Temperature Shutdown Light
(CE Models Only)
Lights when unit overheats and shuts
down (see Section 3-3).
13 Power Switch And Pilot Light
Use switch to turn unit and light On and
Off.
14 Output Selector Switch
See Section 4-2.
15 High Frequency Control
See Section 4-11.
15
Ref. ST-117 264-F / Ref. ST-154 795-C
TM-353 Page 13Syncrowave 250
4-2.Output Selector Switch
1Output Selector Switch
Y Do not use AC output in
damp areas, if movement is
confined, or if there is dan-
1
ger of falling. Use AC output
ONLY if required for the
welding process, and then
use a remote control.
Y Do not change position of
switch while welding or
while under load.
Use switch to select (DCEN) Direct
Current Electrode Negative, AC, or
(DCEP) Direct Current Electrode
Positive output without changing
weld output cable connections.
4-3.Meters
12
Ref. ST-181 675-A
1Voltmeter
Voltmeter displays voltage at the
weld output terminals, but not necessarily the welding arc due to
cable resistance, poor connections, etc.
2Ammeter
Ammeter displays weld amperage
output o f unit.
TM-353 Page 14Syncrowave 250
4-4.Crater Time Controls
1Crater Time Control
Use control to reduce current over a
set period of time (0–15 seconds) at
1
2
the end of the weld cycle when NOT
using a remote current control.
2Crater Time Switch
ON – provides crater time.
OFF – provides no crater time.
Place switch in the OFF position for
Shielded Metal Arc Welding
(SMAW).
Application:
Crater Time should be used while
GTAW welding materials that are
crack sensitive, and/or the operator
wants to eliminate the crater at the
end of the weld.
Note: This applies if the operator is
using an on/off only type control to
start and stop the welding process.
4-5.Spot Time Controls
1Spot Time Switch
Place switch in the ON position to
turn on spot weld circuitry.
2
1
The (GTAW) TIG Spot process is
generally used with a direct current
electrode negative (DCEN) set-up.
Place switch in the OFF position to
turn off spot weld circuitry. Put
switch in the OFF position while doing Shielded Metal Arc Welding
(SMAW).
2Spot T ime Control
Use control to set time (0–5.7 sec-
onds) for Gas Tungsten Arc
(GTAW) spot welds. Spot time begins at arc initiation. If the arc is broken during the spot time cycle, the
timer stops but does not reset.
When the spot time has ended,
weld output stops. Postflow starts
when the remote contactor is
opened. The spot timer resets after
the contactor opens.
Application:
TIG spot welding is used for joining
thinner materials that are in close
contact, with the fusion method. A
good example would be joining coil
ends.
TM-353 Page 15Syncrowave 250
4-6.AC Balance Control
Balanced
3
More Penetration
10
More Cleaning
0
50% Electrode
Positive
50% Electrode
Negative
32% Electrode
Positive
68% Electrode
Negative
55% Electrode
Positive
45% Electrode
Negative
1AC Balance Control
Balance Control (AC GTAW):
Control changes the AC output
square wave. Rotating the control
towards 10 provides deeper pene-
1
Output WaveformsArcSetting
tration. Rotating the control towards
0 provides more cleaning action of
the workpiece.
When the control is in the Balanced
position, the wave shape provides
equal penetration and cleaning
action.
Application:
When welding on oxide forming materials such as aluminum or magnesium, excess cleaning is not necessary. To produce a good weld, only
a minimal amount, approximately a
0.10 in (2.5mm) of etched zone
along the weld toes is required.
Set control to 7 and adjust as necessary. Joint configuration, set-up,
process variables, and oxide thickness may affect setting.
Arc rectification can occur when
welding above 200 amps and/or
while welding with helium gas. If this
condition occurs, increasing the
Balance control towards maximum
penetration, may help to restabilize
the arc.
Ref. S-0795-A
TM-353 Page 16Syncrowave 250
4-7.Amperage Adjustment Controls
2
1Amperage Adjustment Control
Use control to adjust amperage,
1
and preset amperage on ammeter
(see Sect i o n 4 - 3 ) . T h i s c o n t r o l m a y
be adjusted while welding.
For remote amperage control,
front panel control setting is the
maximum amperage available. For
example: I f front panel control is set
to 200 A, the range of the remote
amperage control is 5 to 200 A.
For spot welding, use Amperage
Adjust control to select from 5–310
amps of peak amperage (see Section 4-5).
2Amperage Control Switch
Use switch to select way of control-
ling amperage adjustment.
For front panel control, place switch
in the PANEL position.
For remote control, place switch in
REMOTE 14 position, and connect
remote control device (see Section
3-8).
4-8.Output (Contactor) Control Switch
Y Weld output terminals are
energized when Output
(Contactor) switch is On and
Power is On.
1
1Output/Contactor Switch
Use switch to select way of control-
ling unit output.
For front panel control, place switch
in ON position.
When On is selected, HF and gas
control are disabled.
For remote control, place switch in
REMOTE 14 position, and connect
remote control device (see Section
3-8).
TM-353 Page 17Syncrowave 250
4-9.Arc Controls
1Arc Control (Dig)
For AC And DC SMAW Welding
When set at 0, short-circuit amperage at low arc voltage is the same
1
2
as normal welding amperage.
When setting is increased, short-
circuit amperage at low arc voltage
increases.
Set at 0 for GTA W welding.
2Arc Control Switch
Place switch in the ON position to
turn on arc control circuitry. When
switch is i n the OFF position, no additional amperage is available at
low arc voltages. Place switch in
the OFF position while performing
Gas Tungsten Arc Welding
(GTAW).
Application:
Control helps arc starting or making
vertical or overhead welds by increasing amperage at low arc voltage, and reduces electrode sticking
while welding.
4-10. Postflow Time Control
1Postflow Time Control
Use control to set length of time
(0–70 seconds) gas flows after
welding stops. It is important to s e t
enough time to allow gas to flow un-
1
til after the tungsten and weld
puddle has cooled down.
Application:
Postflow is required to cool tungsten and weld, and to prevent contamination of tungsten and weld. Increase postflow time if tungsten or
weld are dark in appearance.
TM-353 Page 18Syncrowave 250
4-11. High Frequency Controls
1
2
Y Place High Frequency
switch in Off position before
using the shielded metal arc
welding (SMAW) process.
1High Frequency Switch
START – (Up position) provides H F
for arc starting only. High frequency
turns on to help start arc when output is enabled. High frequency
turns off when arc is started, and
turns on whenever arc is broken to
help restart arc.
Application:
HF Start is used when the DCEN
GTA W process is required.
OFF – provides no HF. Use OFF for
SMAW (stick electrode) welding.
CONTINUOUS – (Down position)
provides HF continuously throughout the weld.
Application:
HF Continuous is used when the
AC GTAW process is required.
2High Frequency Intensity
Control
Use control to change amount of
HF energy used to start and maintain the arc. Set as low as practical
to prevent interfering with electronic
equipment.
4-12. Preflow Time Control (Optional)
1Preflow Time Control
Use control to set the length of time
(0–15 seconds) that gas flows before an arc is started.
Application:
Preflow is used to purge the immediate weld area of atmosphere. Preflow also aids in consistent arc
starting.
1
TM-353 Page 19Syncrowave 250
TM-353 Page 20Syncrowave 250
1Input Terminal Board TE1
Provides means for operation on
different input voltages.
2Power Switch S1
Provide on/off control of unit.
3Fan Motor FM
Provides cooling of internal compo-
nents.
4Main T ransformer T1
Supplies power to weld output cir-
cuit, various control circuits, main
control board PC1, and fan motor
FM.
5Control Board PC1
Controls weld output by changing
the SCR gate pulses (conduction
times) after comparing current
feedback to selected amperage
signal.
Also provides input connections for
switches S3, S5, S6, and S7.
6Arc Control Switch S6 And
Control R2
R2 selects short-circuit amperage
when S6 i s O n , and High Frequency control R13 is Off.
7Crater Time Switch S7 And
Control R11
R11 selects crater time when S7 is
on, and Amperage Control switch
S5 is in Panel position.
8Thermostat TP1
If T1 overheats, TP1 opens stop-
ping all weld output.
9Output (Contactor) Switch S3
Selects On or remote contactor
control.
10 AC Balance Control R3
Controls changes to ac output
square wave.
11 Ammeter A1 And Voltmeter
V1
Display weld amperage and voltage while welding.
12 Amperage Control Switch S5
And Adjustment Control R1
R1 selects weld output amperage
when S5 is in Panel.
13 Remote 14 Filter Board
PC2/Remote 14 Receptacle
RC1
PC2 protects unit from high frequency, and RC1 connects remote
amperage and contactor controls to
power source.
14 Circuit Breaker CB1
Protects 115 volts ac duplex recep-
tacle RC2 from overload.
SECTION 5 – THEORY OF OPERATION
1-Phase
Input
Terminal
Board TE1
Power
Switch
S1
Main
Transformer
T1
Circuit
Breaker
CB1
115 VAC
115 VAC Duplex
Receptacle
RC2
Fan
Motor
FM
Control
Board
PC1
Arc Control
Output
Amperage
Crater Time
Switch
S6
Control
Switch S5
Switch
S7
AC
115 VAC
Thermostat
TP1
Line
Input
Power
DC
Synchronization
Signal
SCR
Gating
Signals
Main
Rectifier
SR1
1
φ1φ
124
31423
15
6
9
12
7
5
8
Arc Control
R2
Amperage
Adjustment
Control R1
Crater Time
Control
R11
AC Balance
Control
R3
10
Ammeter
A1
11
Postflow
Timer
TD1
16
Gas
Valve
GS1
17
6
12
Remote
13
Remote 14
Filter Board
PC2
13
7
1φ
, 10 VAC
(Contactor)
Switch S3
24
Background
Power
Source
Amperage
Control
♦
TM-353 Page 21Syncrowave 250
15 115 Volts AC Duplex Recep-
tacle RC2
Provides connection point for auxiliary equipment.
16 Postflow Timer TD1
Controls shielding gas and coolant
postflow time.
17 Gas Valve GS1
Provides shielding gas during the
weld cycle.
18 Preflow Timer TD3, Control
R12, And Switch S9
R12 selects time shielding gas
flows before arc starts. S9 is an integral part of R12 so that when R12
is turned past zero (0), TD3 is off.
19 Spot Timer TD2, Switch S8,
And Control R10
R10 selects time output is available
when spot welding. S8 selects Off
or spot welding with remote contactor control.
20 High Frequency Transformer
T2
Steps up input voltage and charges
capacitor C4 .
21 Spark Gaps G And High Fre-
quency Coupling Coil T3
G provides path for C4 to discharge
into T3. T3 supplies high-frequency
to welding circuit.
22 High Frequency Intensity
Control R13
Changes amount of HF energy
used to sta r t and maintain the arc.
23 Main Rectifier SR1
Changes the ac output from T1 to
ple at low weld output levels.
25 Stabilizer Z1
Smooths dc welding current.
26 Hall Device HD1
Provides current feedback signal to
PC1 through line filter FL1.
27 Line Filter FL1
Filters current feedback signal.
28 Output Selector Switch S4
Provides either AC or DC and out-
put polarity.
29 Integrated Rectifier SR2
Provides dc voltage feedback to
PC1.
30 Electrode And Work W eld
Output Terminals
Provide weld output.
Hall Device
HD1
Optional
AC Or DC Control
External Circuits
Weld Current Circuit
Stabilizer
Z1
Work Weld
Electrode
Output
Terminal
Weld Output
Terminal
High
Frequency
Coupling
Coil T3
Current Feedback
Voltage Feedback
High
Frequency
Intensity
Control R13
Spark Gaps G
High
Frequency
Transformer
T2
♦
1φ Power
25
26
28
30
21
30
22
21
20
Capacitor
C4
Integrated
Rectifier
SR2
29
Line
Filter
FL1
Preflow
Timer
TD3
Preflow Time
Control
R12
Switch
S9
♦
♦
Spot
Timer
TD2
Spot Time
Control
R10
♦
♦
Voltmeter
V1
18
18
19
19
11
27
115 VAC
Spot Time
19♦
Switch
S8
Output
Selector
Switch
S4
Voltage Feedback
♦
SECTION 6 – TROUBLESHOOTING
6-1.Troubleshooting Table
. See Section 6-2 for test points and values and
Section 10 for parts location.
. Use MILLER Testing Booklet (Part No. 150 853)
when servicing this unit.
TroubleRemedy
Prior to Serial No. KG164875, no weld
output; unit completely inoperative –
Effective with Serial No. KG164875,
no weld output; unit completely inoperative; PL2 off.
Replace building line fuse(s) or reset circuit breaker(s) if open.
Check for proper electrical input connections (see Section 3-11).
Check for proper jumper link position (see Section 3-11).
Check Power switch S1 and replace if necessary.
Prior to Serial No. KG164875, no weld
output; fan runs – Effective with Serial
No. KG164875, no weld output; fan
runs; PL2 on.
Check, repair or replace remote control device.
Allow a cooling period of approximately 15 minutes. If thermostats TP1 remain open, check continuity
Check circuit breaker CB1, and reset if open (see Section 7-2).
Place Output Selector switch S4 in desired position (see Section 4-2).
Check optional preflow timer board TD3, and replace if necessary.
Check optional spot timer relay TD2 for proper connections and resistance. Replace TD2 if
Check continuity of Spot Time switch S8. Check condition of contacts. Repair or replace S8 if neces-
Check SR1, and replace necessary components. If components are replaced, check capacitors C7
Unit provides only minimum weld
output.
Check control board PC1 and connections, and replace if necessary.
Unit provides only maximum weld
output.
Check connections for continuity to shunt device on units with Serial No. prior to KB110695.
TM-353 Page 22Syncrowave 250
Be sure line disconnect switch is in the On position.
If using remote control, place Output (Contactor) switch S3 in Remote 14 position, and connect remote control to Remote 14 receptacle RC1 (see Sections 3-8 and Section 4-8). If remote is not being
used, place Output switch S3 in On position.
and replace if necessary (see Section 3-3).
necessary.
sary.
thru C10. Replace capacitor(s) if necessary.
Check control board PC1 and connections, and replace if necessary.
Effective with Serial No. KB1 10695, check resistance and connections of HD1; HD1 is 1600 ohms
±10% between pins 1 and 3 of plug PLG3. Check input and output voltages. Replace HD1 if
necessary.
Check position of Amperage Control switch S5 (see Section 4-7).
Increase Amperage Adjustment control R1 setting if a remote control is used (see Section 4-7).
Check, repair or replace remote control device.
Check resistance and connections of Amperage Adjustment control R1; R1 is 1000 ohms ±10%.
Replace R1 if necessary.
Check SCRs in main rectifier SR1, and replace if necessary. If any SCRs are replaced, Check capacitors C7 through C10 for a short or open, and check for proper connections. Replace C7 through C10
if necessary.
Effective with Serial No. KB1 10695, check resistance and connections of HD1; HD1 is 1600 ohms
±10% between pins 1 and 3 of plug PLG3. Check input and output voltages. Replace HD1 if
necessary.
Check Amperage Adjustment control R1 for proper connections and resistance; R1 is 1000 ohms
±10%. Replace R1 if necessary.
Effective with Serial No. KB1 10695, check resistance and connections of HD1; HD1 is 1600 ohms
±10% between pins 1 and 3 of plug PLG3. Check input and output voltages. Replace HD1 if
necessary.
Check bypass capacitors C13, C14, C16, C17, C18, and C19 for broken leads, shorts, and leakage.
Replace if necessary.
TroubleRemedy
Check SCRs in main rectifier SR1, and replace if necessary. If any SCRs are replaced, Check capacitors C7 through C10 for a short or open, and check for proper connections. Replace C7 through C10
if necessary.
Check control board PC1 and connections, and replace if necessary.
Check connections to line filter FL1. Check input to PC1. Replace FL1 if necessary.
Erratic weld output.
No or limited ac balance control.Check AC Balance control R3 for proper connections and resistance; R3 is 5000 ohms ±10%.
Check control board PC1 and connections, and replace if necessary.
Check SCRs in main rectifier SR1, and replace if necessary. If any SCRs are replaced, Check capac-
No crater fill time.Check position of Crater switch S7 (see Section 4-4).
Be sure arc voltage is below 24 volts (see Section 3-2. Volt-Ampere Curves).
Check position of Amperage Control switch S5, S5 must be in Panel position (see Section 4-7).
Check control board PC1 and connections, and replace if necessary.
Crater fill time too long or does not
time out.
Check for poor or improper input or output connections. See Sections 3-11 and 3-8.
Replace electrode.
Check torch assembly, and replace if necessary.
Check fuse F2 in rectifier SR3 circuit, and replace if necessary.
If Amperage Control switch S5 is in the Remote position check, repair, or replace remote amperage
control device if necessary.
Check connections for continuity to shunt device on units with Serial No. prior to KB110695.
Check Amperage Adjustment control R1 for proper connections and resistance; R1 is 1000 ohms
±10%. Replace R1 if necessary.
Check bypass capacitors C13, C14, C16, C17, C18, and C19 for broken leads, shorts, and leakage.
Replace if necessary.
Check SCRs in main rectifier SR1, and replace if necessary. If any SCRs are replaced, Check capac-
itors C7 through C10 for a short or open, and check for proper connections. Replace C7 through C10
if necessary.
Check control board PC1 and connections, and replace if necessary.
Replace R3 if necessary.
itors C7 through C10 for a short or open, and check for proper connections. Replace C7 through C10
if necessary.
Check position of Crater control R11 (see Section 4-4).
Check position of Crater control R11 (see Section 4-4).
Check resistance and connections of Crater control R11; R11 is 5 meg ohms ±10%. Replace R11 if
necessary.
Check control board PC1 and connections, and replace if necessary.
No arc control.
Lack of high frequency at tungsten
electrode; difficulty in starting an arc.
Use shortest possible cables (see Section 3-7).
Check cables and torch for cracked or deteriorated insulation or bad connections. Repair or replace
Be sure to disconnect SMAW electrode cable from weld output terminal when GT AW welding.
Decrease gas flow setting.
Use properly prepared tungsten.
Increase setting of High Frequency Intensity control R13 (see Section 4-11).
Check spark gaps G, and readjust if necessary (see 7-4).
Place Arc Control switch S6 in the On position.
Place High Frequency switch S2 in the Off position.
Be sure arc voltage is below 24 volts (see Section 3-2. Volt-Ampere Curves).
Check position of Arc Control R2 (see Section 4-9).
Check fuse F1 in rectifier SR3 circuit, and replace if necessary.
Check resistance and connections of Arc control R2; R2 is 1000 ohms ±10%. Replace R1 if
necessary.
Check control board PC1 and connections, and replace if necessary.
Use proper size tungsten for welding application.
necessary parts.
TM-353 Page 23Syncrowave 250
TroubleRemedy
No high frequency at spark gaps G.
No preflow time (optional).Place Output (Contactor) switch S3 in Remote position and be sure remote control is connected to
Check continuity of Preflow Time switch S9. Check condition of contacts. Repair or replace S9 if nec-
Remove jumper link 1 on terminal strip 1T.
Check optional preflow timer board TD3, and replace if necessary.
Optional spot timer relay TD2 does not
time out.
Remove jumper link 2 from terminal strip 1T.
Place Spot Time control R10 in desired position.
Check coil voltage and connections of spot timer relay TD2. Check continuity of coil and condition of
Check coil voltage and connections of control relay CR3. Check continuity of coil and condition of
Check coil voltage and connections of control relay CR1. Check continuity of coil and condition of
Postflow timer does not time out.Check position of Postflow Time control setting (see Section 4-10).
Check Control relay CR5 contacts 2 and 5 for proper operation. Replace CR5 if necessary.
Check coil voltage and connections of gas valve GS1. Check continuity of coils. Replace GS1 if nec-
Check control board PC1 and connections, and replace if necessary.
No postflow time.Check position of Postflow Time control setting (see Section 4-10).
Place Output(Contactor) switch S3 in the Remote position, and connect a remote control to recep-
Check coil voltage and connections of control relay CR5. Check continuity of coil and condition of
Check control board PC1 and connections, and replace if necessary.
No gas flow.Place Output(Contactor) switch S3 in the Remote position, and connect a remote control to recep-
TM-353 Page 24Syncrowave 250
Check position of High Frequency switch S2 (see Section 4-11).
Place Output (Contactor) switch S3 in Remote position and be sure remote control is connected to
Remote receptacle RC1 (see Section 3-8).
Check circuit breaker CB1, and reset if open (see Section 7-2).
Check fuse F1 in rectifier SR2 circuit, and replace if necessary.
Check coil voltage and connections of contactor control relay CR1. Check continuity of coil and con-
dition of contacts. Replace CR1 if necessary.
Check coil voltage and connections of contactor control relay CR5. Check continuity of coil and con-
dition of contacts. Replace CR5 if necessary.
Check spark gaps G, and readjust if necessary (see Section 7-4).
Check resistance and connections of High Frequency Intensity control R13; R13 is 1.5 ohms ±10%.
Replace R1 if necessary.
Check capacitor C4 for a short or open, and check for proper connections. Replace C4 if necessary.
Check transformer T2 for signs of winding failure. Check continuity across windings, and check for
proper connections. Check secondary voltages. Replace T2 if necessary.
Check coupling coil T3 for signs of winding failure. Check continuity across windings, and check for
proper connections. Replace T3 if necessary.
Check control board PC1 and connections, and replace if necessary.
Remote receptacle RC1 (see Section 3-8).
Check position of Preflow Time control R12.
essary.
Place Spot Time switch S8 in the On position.
contacts. Replace TD2 if necessary.
contacts. Replace CR3 if necessary.
contacts. Replace CR1 if necessary.
essary.
Check input voltage and connections to Postflow timer board TD1. Check continuity of contacts. Re-
place TD1 if necessary.
tacle RC1 according to Section 3-8.
contacts. Replace CR5 if necessary.
Check coil voltage and connections of gas valve GS1. Check continuity of coils. Replace GS1 if nec-
essary.
Check input voltage and connections to Postflow timer board TD1. Check continuity of contacts. Re-
place TD1 if necessary.
tacle RC1 according to Section 3-8.
Check circuit breaker CB1, and reset if open (see Section 7-2).
TroubleRemedy
Check Control relay CR2 contacts 4 and 7 for proper operation. Replace CR2 if necessary.
Check coil voltage and connections of gas valve GS1. Check continuity of coils. Replace GS1 if nec-
No power output at 115 volts ac receptacle RC1; weld output available.
Fan motor FM does not run; weld output available. Effective with Serial No.
KG164875, unit is equipped with FanOn-Demand, which only runs when
cooling is required.
Check coil voltage and connections of fan motor FM, and replace if necessary.
Line fuse opens immediately when
solid-state contactor SR1 turns on in
DC mode only.
Check SCRs in main rectifier SR1, and replace if necessary. If any SCRs are replaced, Check capac-
No control of weld output.Check position of Amperage Control switch S5 (see Section 4-7).
Check control board PC1 and connections, and replace if necessary.
Tungsten electrode oxidizing and not
remaining bright after conclusion of
weld.
Check and tighten all gas fittings if necessary.
Increase gas flow setting.
Properly prepare tungsten.
Wandering arc - poor control of direction of arc.
Controls connected to Remote 14
receptacle RC1 do not work properly.
Ammeter A1 not displaying correct
weld output amperage.
Voltmeter V1 not displaying correct arc
voltage.
Electronic equipment in welding area
not working properly.
essary.
Check circuit breaker CB1, and reset if open (see Section 7-2).
Check and clear fan blade obstruction.
Check diode D1, and replace if necessary.
itors C7 through C10 for a short or open, and check for proper connections. Replace C7 through C10
if necessary.
Check resistance and connections of Amperage Adjustment control R1; R1 is 1000 ohms ±10%.
Replace R1 if necessary.
Check, repair or replace remote control device.
Effective with Serial No. KB1 10695, check resistance and connections of HD1; HD1 is 1600 ohms
±10% between pins 1 and 3 of plug PLG3. Check input and output voltages. Replace HD1 if
necessary.
Check position of Postflow Time control R12 (see Section 4-10).
Shield weld zone from drafts.
Place High Frequency switch S2 in Start or Continuous position.
Use proper size tungsten for welding application.
Properly prepare tungsten.
Check, repair or replace remote control device.
Check Amperage Control switch S5 position (see Section 4-7). Check and replace S5 if necessary.
Check Output (Contactor) switch S3 position (see Section 4-8). Check and replace S3 if necessary.
Check position of jumper links 1 and 2 on terminal strip 1T according to Section 6-2.
Check coil voltage and connections of control relay CR2. Check continuity of coil and condition of
contacts. Replace CR2 if necessary.
Prior to Serial No. KF959379, check choke RFC1 connections. Check continuity of RFC1. Replace if
necessary. Effective with Serial No. KF959379 check remote 14 filter board PC2 (see Section 6-6).
Replace PC2 if necessary.
Check control board PC1 and connections, and replace if necessary.
Calibrate ammeter as instructed in Section 6-8.
Check ammeter A1 voltage; +1 millivolts dc per 3 ampere of weld output. Replace A1 if necessary.
Check control board PC1 and connections, and replace if necessary.
Effective with Serial No. KB1 10695, check resistance and connections of hall device HD1; HD1 is
1600 ohms ±10% between pins 1 and 3 of plug PLG3. Check input and output voltages. Replace HD1
if necessary.
Check connections for continuity to voltmeter V1. Replace V1 if necessary.
HF interference problem. Check for proper installation, and correct problem (see Section 8).
TM-353 Page 25Syncrowave 250
TM-353 Page 26Syncrowave 250
6-2.Troubleshooting Circuit Diagram For Welding Power Source
Y Disable high frequency by placing High Frequency
switch S2 in Off position before testing unit.
R1
V2
V3
V1
V4
V5
V6
V13
V14
V15
V16
Link 1 Link 2
V7
V8
V9
V10
V11
V17
V12
R1
R1
See Section 3-8
for RC1
information
TD1 begins to time out
when CR5 deenergizes
TD3 begins to time out
when CR4 energizes
See Figure 9-19
for PC3 circuit
CR3 energizes during spot time
when an arc is detected
CR4 energizes when remote contactor
switch closes
CR2 energizes when
remote contactor
switch closes
See Section 6-6
for PC2 data
R1
V25
TM-353 Page 27Syncrowave 250
SC-188 161
Test Equipment Needed:
V24
V22
V21
R3
R2
V20
A
A
A
A
R1
V25
Resistance Values
a)Tolerance – ±10% unless specified
b)Turn Off unit and disconnect input
power before checking resistance
R1All values for T1, Z1, and T3 are less
than 1 ohm
R25.3 ohms
R36.1 K ohms
Voltage Readings
a)Tolerance – ±10% unless
specified
b) Reference – to circuit
common (lead 42) unless
noted
c)Wiring Diagram – see
Section 10
V1230 volts ac
V277 volts ac
V382.5 volts ac
V457 volts ac
V5, V6115 volts ac
V724 volts ac
V8, V918 volts ac
V1010 volts ac
V1180 volts dc
V12. V13, V14115 volts ac
V15, V16, V1724 volts ac
V18115 volts ac with S2
in Start or Continuous
V190 to +10 volts dc
with contactor on
V20, V2124 volts dc
V220-80 volts dc (rec-
tified arc voltage)
V23maximum 80 volts
ac/dc
V2424 volts dc
V2516.5 millivolts dc
per 1 ampere of
weld output
CR1 energizes
when open-circuit voltage
is present; denergizes
when an
arc is struck
See Figure 10-1 for
HD1 location
No calibration available
for voltmeter V1
R1
V23, B,
C, D, E
See Section 6-3
for waveforms
B, C, D, E
See also
Sections 6-4 and 6-5
for PC1 data
CR5 energizes when
contactor is on
See Section 6-8
for ammeter A1
calibration
V19
V18
See Section 6-3
for waveform A
TM-353 Page 28Syncrowave 250
6-3.Waveforms For Section 6-2
Waveforms shown are for 60 Hertz models;
waveforms for 50 Hertz models are similar.
5 ms 1 V
A. SR1 Gate Pulse With Respect To Cathode
At No Load
5 ms 50 V
B. DC Open-Circuit Voltage With Amperage
Adjustment Control At Maximum
5 ms 20 V
C. DC Output, 100 Amperes, 24 Volts DC
(Resistive Load)
5 ms 50 V
D. AC Open-Circuit Voltage With Amperage
Adjustment Control At Maximum
gnd
gnd
gndgnd
TM-353 Page 29Syncrowave 250
Test Equipment Needed:
5 ms 50 V
E. AC Output, 100 Amperes, 24 Volts AC (Re-
sistive Load)
gnd
6-4.Control Board PC1 Testing Information (Use With Section 6-5)
Y Disable high frequency by
Be sure plugs are secure before
testing. See Section 6-5 for specific
values during testing.
placing High Frequency
switch S2 in Off position
before testing unit.
4
6
5
Test Equipment Needed:
SB-178 976-A / ST-800 344-A
TM-353 Page 30Syncrowave 250
6-5.Control Board PC1 Test Point Values
PC1 Voltage Readings
ReceptaclePinValue
RC51118 volts ac input
218 volts ac input
3+10 volts dc output
4Circuit common
5Not used
6Not used
RC521Circuit common
2+1 millivolt dc per 3 ampere of weld output
RC531Gate pulse for SCR1 with respect to pin 2 (see Section 6-3)
2Reference for gate pulse to SCR1
3Gate pulse for SCR3 with respect to pin 4 (see Section 6-3)
4Reference for gate pulse to SCR3
a) Tolerance –
±10% unless
specified
b) Reference – to circuit common
(lead 42) unless noted
5Gate pulse for SCR2 with respect to pin 6 (see Section 6-3)
6Reference for gate pulse to SCR2
7Gate pulse for SCR4 with respect to pin 8 (see Section 6-3)
8Reference for gate pulse to SCR4
RC541Not used
20 to +10 volts dc input from min. to max. of Amperage Adjustment control R1 with Amperage Control
30 volts with Output (Contactor) switch S3 in On position or +7.8 volts dc with S3 in Remote position
40 to +10 volts dc input from min. to max. of Crater Control R11 with Crater Fill switch S7 in On posi-
5+10 volts dc output with Output (Contactor) switch S3 in On position
6–24 volts dc
7–24 volts dc with contactor on or off
80 to +10 volts dc input from min. to max. of Amperage Adjustment control R1 with contactor on
90 to +10 volts dc input from min. to max. of Amperage Adjustment control R1 with contactor on
10Circuit common
11+24 volts dc
switch S5 in Panel position, and contactor on
tion, or +10 volts dc with S7 in Off position
120 volts during open-circuit voltage condition; +24 volts with arc on or contactor off
TM-353 Page 31Syncrowave 250
ReceptacleValuePin
RC551Circuit common
2+1.65 volts dc per 100 amperes of weld output with respect to pin 1
3–15 volts dc output
40 to +4 volts dc input from min. to max. of Arc Control R2 with Arc Control switch S6 On
510 volts ac input for synchronization
6+5.8 volts dc output
7–15 volts dc input from Max. Penetration setting of AC Balance control R3 to +5.8 volts dc input at
80 to 80 volts dc voltage feedback signal (rectified arc voltage) with respect to pin 9
90 to 80 volts dc voltage feedback signal (rectified arc voltage) with respect to pin 8
100 to +4 volts dc input from min. to max. of Arc Control R2 with Arc Control switch S6 Off
Max. Cleaning setting of R3
TM-353 Page 32Syncrowave 250
6-6.Remote Board PC2 Testing Information (Use With Section 6-7)
Y Disable high frequency by
Be sure plugs are secure before
testing. See Section 6-7 for specific
values during testing.
1Remote 14 Filter Board PC2
2Remote 14 receptacle RC1
See Section 3-8 for information.
3Receptacle RC2
4Receptacle RC3
placing High Frequency
switch S2 in Off position
before testing unit.
1
4
3
2
Test Equipment Needed:
ST-157 960-B / ST-800 344-A
TM-353 Page 33Syncrowave 250
6-7.Remote 14 Filter Board PC2 Test Point Values (Use With Section 6-2 And Section 6-6)
PC2 Voltage Readings
ReceptaclePinValue
RC1A24 volts ac
BContact closure to A completes 24 volts ac contactor control circuit
CCommand reference; 0 to +10 volts dc output to remote control
DRemote control circuit common
E0 to +10 volts dc input command signal from remote control
KChassis common
RC21Command reference; 0 to +10 volts dc output to remote control
3Contact closure to A completes 24 volts ac contactor control circuit
4Remote control circuit common
50 to +10 volts dc input command signal from remote control
624 volts ac
RC31Chassis common
a) Tolerance –
±10% unless
specified
b) Reference – to circuit common
(lead 42) unless noted
TM-353 Page 34Syncrowave 250
6-8.Meter Calibration
No calibration available for ammeter
offset, or for voltmeter V1.
Be sure plugs are secure before
calibrating meter.
1Control Board PC1
2Voltmeter V1
3Ammeter A1
1
Top View
R19
Amperes
Adjust R19 for amperage gain to
match external calibrated meter
using load bank set at desired
load.
1Circuit Breaker CB1
If CB1 opens, output to the 115 volts
ac duplex receptacle, high frequency, and gas flow stop. Press button
to reset breaker.
CB1
1
Ref. ST-154 795-C
TM-353 Page 37Syncrowave 250
7-3.Fuses F1 And F2
1Fuse F1 (See Parts List For
Rating)
Fuse F1 (between leads 50 and
150) protects wiring harness from
1
2
Tools Needed:
3/8 in
shorted SR2. If F1 opens, you may
experience problems with arc starting and arc performance in the DC
TIG mode.
2Fuse F2 (See Parts List For
Rating)
Fuse F2 (between leads 22 and
149) protects wiring harness from
shorted SR3. If F2 opens, you may
experience problems with arc control, and no high frequency in start
high frequency.
7-4.Adjusting Spark Gaps
4
3
2
Tools Needed:
Y Turn Off power before
adjusting spark gaps.
4
3
1
Open access door.
1Tungsten End Of Point
Replace point if tungsten end dis-
appears; do not clean or dress
tungsten.
2Spark Gap
Normal spark gap is 0.008 in (0.203
mm).
If adjustment is needed, proceed as
follows:
3Adjustment Screws
Loosen screws. Place gauge of
proper thickness in spark gap.
4Pressure Point
Apply slight pressure at point until
gauge is held firmly in gap. Tighten
screws to 12 in/lbs torque (overtightening will deform plastic base). Adjust other gap.
Close access door.
Ref. ST-154 795-C / Ref. S-0043
TM-353 Page 38Syncrowave 250
SECTION 8 – HIGH FREQUENCY (HF)
8-1.Welding Processes Using HF
1
WorkWork
1HF V oltage
GTAW – helps arc jump air gap
between torch and workpiece and/
or stabilize the arc.
SAW – helps arc reach workpiece
2
1
through flux granules.
2Flux
Gas Tungsten Arc
Welding (GT AW)
Submerged Arc
Welding (SAW)
8-2.Sources Of HF Radiation From Incorrect Installation
Weld Zone
11, 12
50 ft
(15 m)
10
9
8
7
3
13
1
2
high_freq1 7/95 – S-0693
14
Sources Of Direct HF Radiation
1HF source (welding power source with
built-in HF or separate HF unit)
2Weld Cables
3Torch
4Work Clamp
456
5Workpiece
6Work Table
Sources Of Conduction Of HF
7Input Power Cable
8Line Disconnect Device
9Input Supply Wiring
S-0694
Sources Of Reradiation Of HF
10 Ungrounded Metal Objects
11 Lighting
12 Wiring
13 Water Pipes And Fixtures
14 External Phone And Power Lines
TM-353 Page 39Syncrowave 250
8-3.Correct Installation
5
7
50 ft
(15 m)
Ground All
Metal Objects
And All Wiring
In Welding Zone
Using #12 AWG
Wire
Nonmetal
Building
1
Weld Zone
3
Ground
Workpiece
If Required
By Codes
6
50 ft
(15 m)
4
2
7
8
1HF Source (Welder With Built-In HF Or
Separate HF Unit)
Ground metal machine case, work output
terminal, line disconnect device, input
supply, and worktable.
2Welding Zone And Centerpoint
A circle 50 ft (15 m) from centerpoint
between HF source and welding torch in all
directions.
3Weld Output Cables
Keep cables short and close together.
4Conduit Joint Bonding And Grounding
7
10
9
Electrically join (bond) all conduit sections
using copper straps or braided wire. Ground
conduit every 50 ft (15 m).
5Water Pipes And Fixtures
Ground water pipes every 50 ft (15 m).
6External Power Or Telephone Lines
Locate HF source at least 50 ft (15 m) away
from power and phone lines.
7Grounding Rod
Consult the National Electrical Code for
specifications.
7
Metal Building
Ref. S-0695 / Ref. S-0695
8Metal Building Panel Bonding Methods
Bolt or weld building panels together, install
copper straps or braided wire across seams,
and ground frame.
9Windows And Doorways
Cover all windows and doorways with
grounded copper screen of not more than
1/4 in (6.4 mm) mesh.
10 Overhead Door Track
Ground the track.
TM-353 Page 40Syncrowave 250
SECTION 9 – ELECTRICAL DIAGRAMS
. The circuits in this manual can be used for troubleshooting, but there might be minor circuit differences from your machine. Use circuit inside
machine case or contact distributor for more information.
The following is a list of all diagrams for models covered by this manual.
ModelSerial Or Style NumberCircuit DiagramWiring Diagram
+When ordering a component originally displaying a precautionary label, the label should also be ordered.
BE SURE TO PROVIDE MODEL AND SERIAL NUMBER WHEN ORDERING REPLACEMENT PARTS.
+When ordering a component originally displaying a precautionary label, the label should also be ordered.
♦OPTIONAL
BE SURE TO PROVIDE MODEL AND SERIAL NUMBER WHEN ORDERING REPLACEMENT PARTS.
TM-353 Page 72Syncrowave 250
Item
No.
Dia.
Mkgs.
Part
No.
DescriptionQuantity
Figure 10-3. Rectifier, Si Diode (Fig 10-1 Item 2)
*Recommended Spare Parts
♦♦Effective with Serial No.LA337284, Spark Gap Assembly 020 623 consisting of: Base 095 621, Holder 020 622,
and Points 020 603, is no longer available. If replacement parts are needed for any units with a Serial No. prior to
LA337284, you must first order and install Spark Gap Assembly Service Kit 203 419. To replace spark gap parts in
units with Serial No. LA337284 and following, or for units with Spark Gap Assembly Service Kit 203 419 installed, order
appropriate spark gap parts listed above as, eff/w Serial No. LA337284.
BE SURE TO PROVIDE MODEL AND SERIAL NUMBER WHEN ORDERING REPLACEMENT PARTS.