ESAB Caddy 130 User manual

0740 800 043 Valid for serial no. 301--xxx--xxxx to 220--xxx--xxxx040906
LHN 130/140/200
Caddy 130/140/200
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Service manual

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LIST OF CONTENTS Page
READ THIS FIRST 2........................................................
COMPONENT DESCRIPTION, LHN 130/140/200 4.............................
WIRING DIAGRAM LHN 130 7...............................................
WIRING DIAGRAM LHN 140 valid before ser.no. 011--xxx--xxxx 8........................
WIRING DIAGRAM LHN 140 valid for ser.no. 011--xxx--xxxx and 220--xxx--xxxx 9...............
WIRING DIAGRAM LHN 200 valid before ser.no. 011--xxx--xxxx 10........................
WIRING DIAGRAM LHN 200 valid for ser.no. 011--xxx--xxxx and 220--xxx--xxxx 11...............
COMPONENT POSITIONS, CIRCUIT BOARD AP01 12..........................
DESCRIPTION OF OPERATION, CIRCUIT BOARD AP01 14.....................
CHECKING THE GATE PULSES 19...........................................
CIRCUIT DIAGRAM, CIRCUIT BOARD AP02 20.................................
CIRCUIT DIAGRAM, CIRCUIT BOARD AP03 22.................................
MOS TESTER 24............................................................
SOFT STARTING 25.........................................................
ASSEMBLY/DISASSEMBLY 26................................................
LOAD CHARACTERISTICS 30................................................
TECHNICAL DATA 31........................................................
INSTALLATION 32...........................................................
OPERATION 33.............................................................
MAINTENANCE 34..........................................................
SPARE PARTS 35...........................................................
NOTES 35..................................................................
READ THIS FIRST
Maintenance and repair work should be performed by an experienced person, and electrical
work only by a trained electrician. Use only recommended replacement parts.
This service manual is intended for use by technicians with electrical/electronic training for
help in connection with fault--tracing and repair.
Use the wiring diagram as a form of index for the description of operation. The circuit
board is divided into numbered blocks, which are described individually in more detail in
the description of operation. All component names in the wiring diagram are listed in the
component description.
This manual contains details of all design changes that have been made up to and including
August 2004.
The manual is valid for the LHN 130, LHN 140 and LHN 200 with serial numbers:
301--xxx--xxxx, 508--xxx--xxxx, 535--xxx--xxxx, 540--xxx--xxxx, 628--xxx--xxxx,
011--xxx--xxxx and 220--xxx--xxxx.
The LHN 130, LHN 140 and LHN 200 are designed and tested in accordance with
international and European standard IEC/EN 60974--1 and EN 50199.
On completion of service or repair work, it is the responsibility of the person(s) etc.
performing the work to ensure that the product does not depart from the requirements
of the above standard.
Rights reserved to alter specifications without notice.

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WARNING
READ AND UNDERSTAND THE INSTRUCTION MANUAL BEFORE INSTALLING OR OPERATING.
ARC WELDING AND CUTTING CAN BE INJURIOUS TO YOURSELF AND OTHERS. TAKE PRECAU-
TIONS WHEN WELDING. ASK FOR YOUR EMPLOYER’S SAFETY PRACTICES WHICH SHOULD BE
BASED ON MANUFACTURERS’ HAZARD DATA.
ELECTRIC SHOCK -- Can kill
SInstall and earth the welding unit in accordance with applicable standards.
SDo not touch live electrical parts or electrodes with bare skin, wet gloves or wet clothing.
SInsulate yourself from earth and the workpiece.
SEnsure your working stance is safe.
FUMES AND GASES -- Can be dangerous to health
SKeep your head out of the fumes.
SUse ventilation, extraction at the arc, or both, to keep fumes and gases from your breathing zone and
the general area.
ARC RAYS -- Can injure eyes and burn skin.
SProtect your eyes and body. Use the correct welding screen and filter lens and wear protective
clothing.
SProtect bystanders with suitable screens or curtains.
FIRE HAZARD
SSparks (spatter) can cause fire. Make sure therefore that there are no inflammable materials nearby.
NOISE -- Excessive noise can damage hearing
SProtect your ears. Use ear defenders or other hearing protection.
SWarn bystanders of the risk.
MALFUNCTION -- Call for expert assistance in the event of malfunction.
PROTECT YOURSELF AND OTHERS!
WARNING !
STATIC ELECTRICITY can damage circuit
boards and electronic components.
SObserve precautions for handling electrostatic
sensitive devices.
SUse proper static--proof bags and boxes.
ESD

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COMPONENT DESCRIPTION, LHN 130/140/200
This component description relates to the wiring diagrams on pages 7 -- 11.
The LHN 130/140/200 rectifier power units are primary switched type, using parallel--
connected MOSFET transistors as switching devices. Switching frequency is 36 kHz.
The conduction interval ranges between zero and 11 µs, depending on the welding current
being supplied. The conduction time and frequency are controlled by circuit board AP01.
AP01 Main circuit board with control electronics. See the description on page 14.
AP02 Circuit board with power transistors for the positive pole:see description on
page 20.
WARNING: these transistors are at mains voltage.
AP03 Circuit board with power transistors for the negative pole:see description
on page 22.
WARNING: these transistors are at mains voltage.
AP04 Suppression circuit board and protection against transient voltages:
protects the secondary diodes against transient voltages.
Replaced by capacitors C06 from serial number 628--xxx--xxxx.
See “transient protection, rectifer unit V03, V04” on page 6.
AP05 Suppression circuit board, EMC. Protects from mains borne interference
to/from the machine. Mounted from serial no. 540--xxx--xxxx.
LHN 200: The ferrite ring cores L06 and L07 are included in AP05.
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Circuit diagram and component positions circuit board AP05
C01 Capacitor, 0.1 µF, 1000 VDC, transient protection.
C02 Capacitor, 1000 µF, buffer/smoothing capacitor. This capacitor takes about
two minutes to discharge after disconnecting the equipment from mains.
C03 See C02. Not mounted in LHN 130/140.

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C04 Capacitor, 0.1 µF, 1000 VDC, protects the equipment against RFI.
C05 2 -- capacitors, 4.7 µF: see L02. Not mounted in LHN 130.
C06 2 -- capacitors, 12 nF. Protection against transient voltages.
Replacing AP04 from serial number 628--xxx--xxxx.
See “transient protection, rectifer unit V03, V04” on page 6.
C06 is replaced by ferrite rings (L03--L05) from ser. no. 011--xxx--xxxx.
EV01 Fan, 24 VDC.
Note: The fans are different in LHN 130 and LHN 140/200.
In LHN 130 must not the same fan be used as in LHN 140/200.
HL01 Indicating lamp, 28 V, white, showing that the mains power supply is
turned on.
L01 Secondary inductor.
L02 Inductor. Not mounted in LHN 130.
Together with C05 and V06, this forms an LC circuit which reduces the
risk of the arc extinguishing at low welding currents.
Capacitor C05 in the LC circuit charges when V03 conducts. The circuit
can temporarily maintain a high output voltage at low welding current,
reducing the risk of the arc being extinguished.
Diode V06 protects capacitor C05 against negative voltage.
L03 LHN 140: Primary inductor, for improving the machine’s form factor, i.e.
reducing mains loading.
LHN 200: Ferrite ring core (from serial number 011--xxx--xxxx).
L04 LHN 200: Coil, included in conductor 013.
LHN 140: Ferrite ring core (from serial number 011--xxx--xxxx).
L05 Ferrite ring core (from serial number 011--xxx--xxxx).
L06, L07 LHN 200: Ferrite ring cores, included in AP05.
QF1 Mains switch: 2--pole in the LHN 130/140 and 3--pole in the LHN 200.
RP01 Potentiometer for adjusting welding current, 10 kΩ,2W.
RS01 Shunt, 120 mV at 130 A or 140 A or 200 A respectively.
RV01 Varistor, 275 V, transient voltage protection. Only LHN 130/140.
From serial no. 540--xxx--xxxx the transient voltage protection is included
at circuit board AP05.
RV01--RV03 Varistors, 480 V, transient voltage protection. Only LHN 200.
From serial no. 540--xx--xxxx the transient voltage protection is included at
circuit board AP05.
ST01 Thermal overload cutout, fitted in the main transformer (TC02) winding.
LHN 130/140: interrupts at 130 ˚C, recloses at 100 ˚C.
LHN 200: interrupts at 150 ˚C, recloses at 130 ˚C.
TC01 Control power supply transformer. Primary side is supplied at 230 V or
400 V respectively. Dual secondary windings supply 20.5 V and 17 V to
circuit board AP01.
TC02 Main transformer: see on page 29 for installation instructions.

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V01, V02 Mains rectifier diode bridge, 35 A, 1200 V. After replacing the rectifier
bridges, the machine must be soft--started: see instructions on page 25.
Rectifier bridge V02 is only mounted in LHN 200.
V03, V04 Rectifier and freewheel diodes.
V03 rectifies the welding current.
During the time interval between two voltage pulses from transformer
TC02, the freewheel diodes V04 maintain the welding current from
inductor L01.
Before serial number 628--xxx--xxxx:
V03 consists of six parallel--connected diodes, and V04 consists of eight
parallel--connected diodes. V03 and V04 are mounted on the same cooling
fins. If any of the diodes is/are faulty, the entire cooling fin unit must be
replaced, as the diodes are soldered to it. For spare parts see the spare parts
list item 430 (LHN 140/200) and item 830 (LHN 130)
From serial number 628--xxx--xxxx:
A new rectifier unit is introduced. On the cooling fins in LHN 130/140 is
one diode module mounted and in LHN 200 are two diode modules
mounted. Each diode module has two diodes.
See page 27 for fitting instructions.
V05 LED, yellow.
Lit when thermal overload cutout ST01 opens due to high temperature.
V06 Diode: see L02. Not mounted in LHN 130.
X01 Mains terminal block: 4--pole or 8--pole respectively. Replaced by circuit
board AP05 from serial no. 540--xxx--xxxx.
XS01--XS13 Sleeve connectors.
XS11 LHN 140/200: 12--pole connector for connection of remote control unit.
XS12 Welding terminals (2 -- OKC connectors).
TRANSIENT PROTECTION, RECTIFIER UNIT V03, V04
C06
LHN 130/140 LHN 200
before serial number 628--xxx--xxxx
LHN 130/140/200
with serial number 628--xxx--xxxx
and 220--xxx--xxxx

WIRING DIAGRAM LHN 130
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WIRING DIAGRAM LHN 140 valid before ser.no. 011--xxx--xxxx
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WIRING DIAGRAM LHN 140 valid for ser.no. 011--xxx--xxxx and 220--xxx--xxxx
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WIRING DIAGRAM LHN 200 valid before ser.no. 011--xxx--xxxx
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WIRING DIAGRAM LHN 200
valid for ser. no. 011--xxx--xxxx and 220--xxx--xxxx
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COMPONENT POSITIONS, CIRCUIT BOARD AP01
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Circuit board AP01 0481 870 880, fitted before serial number 220--xxx--xxxx
Circuit board AP01 0481 870 885, fitted before serial number 220--xxx--xxxx

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Circuit board AP01 0486 886 880, fitted from serial number 220--xxx--xxxx
WARNING: high voltage in the shaded areas
From serial number 220--xxx--xxxx circuit board 0486 886 880 is fitted in the machines. The
circuit board versions are fully interchangeable and can be used in any of the machines.

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DESCRIPTION OF OPERATION, CIRCUIT BOARD AP01
This description refers to the wiring diagrams on pages 7--11 and to the component position
diagrams on pages 12 and 13. Only those items connected to the circuit board inputs and
outputs are described here. If the circuit board is faulty, it must be replaced.
There are three versions of the circuit board, this description applies to all versions. The
circuit boards are fully interchangeable.
After replacing the circuit board, the machine must be soft--started, as described on page 25.
1 Power supply
Rectifier bridge D1--D4 is supplied at 20.5 V from transformer TC01. The rectified voltage
is stabilised by voltage regulator VR1 to +20 ±1 V. All circuits on the circuit board except
the current reference (6) and the gate circuit (9) are supplied from VR1.
Connections A05 -- A06 supply 26 V DC ±2.5 V to the cooling fan.
The fan is not the same in LHN 130 as in LHN 140/200, see the spare parts list.
2 Thermal shutdown
This circuit interrupts the gate pulses from the pulse width modulator if the machine is
overloaded. When it has not operated due to high temperature, the thermal overload cutout
normally short--circuits inputs B01 and B02. If the cutout contact opens, IC1 lights LED
V05 and the pulse width modulator (8) blocks the gate pulses. See also ST01 in the
component description.
The reference voltage to IC1, +ref., is generated by IC3: see page 17.

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3 Under voltage detector
This circuit senses if the mains power supply voltage is too
low. Loss of mains power supply for more than 10 ms, or low
voltage, results in the pulse width modulator (8) blocking the
gate pulses.
The reference voltage to IC1, +ref., is generated by IC3:
seepage17.
4a Current detector
Valid for circuit board 481 870 880
Inputs B04 and SH2 sense the voltage across
welding inductor L01. Input SH2 is the zero
point for the control amplifier. On no--load, the
voltage is close to zero. During welding, the
voltage between B04 and SH2 consists of short
pulses at a potential of about --70 V.
This voltage is rectified and smoothed by D7, R11 and C10, to provide a voltage after
R11 of +3 to +3.5 V at no--load and --10 to --50 V when welding. This signal interrupts
the Hot Start (starting current boost), the length (200 ms) of which is controlled by the
control amplifier (7).
4b Open--circuit voltage detector
Valid for circuit boards 481 870 885 and 486 886 880
Voltages above 65V are defined
as open--circuit voltage.
Voltages below 45V are defined
as welding voltages.
When the machine is in
open--circuit mode the current
limit is at a low rate and the
unit is ready for Hot Start.
5 Arc voltage limitation
This circuit, which restrict the arc voltage and open--circuit voltage, assists in limiting the
arc length when welding in the 20 -- 50 A current range.

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6 Current reference
This circuit supplies a signal voltage to the current setting potentiometer and remote
control unit. It also modifies the current reference signal to a suitable level for the control
amplifier (7).
Connections A01 and A02 are supplied at 17 V from transformer TC01. This supply is
rectified and smoothed for supply to voltage regulator VR2. Potentiometer R21 adjusts
the output voltage from VR2 for correct maximum current value from the current
reference and control amplifier. After adjustment, the voltage between connection C03
and C05 must be 14 -- 15 V.
Q10, R76 and R77 limit the current from VR2 to 60 mA. The current limit protects the
circuit board in the event of a short circuit in the cable to the remote control unit.
The reference input has a separate power supply and high--impedance input to the
control amplifier, protecting it against short circuits between the remote control unit
cable and the welding circuit.
Changeover to remote control is arranged by short--circuiting connections D01 and
D02 through insertion of the plug into the socket for the remote control unit. The short
circuit is in the form of a link between L and M in the plug.
The current reference signal is connected to C04 or D04. The reference signal voltage
is 0 V at minimum current and 14 -- 15 V at maximum current. If inputs D01 and D02
are linked, but no remote control unit is fitted, resistor R74 holds the reference signal
to the minimum level.
LHN 130 has no remote control connection.

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7 Control amplifier
The control amplifier sets a suitable welding current in relation to the current setting
and arc voltage. The circuit can be divided up into three main parts:
SAverage current control
SStarting current control
SShort--circuit current limit
8 Pulse Width Modulator
The pulse width modulator determines the frequency and pulse time of the control
pulses to the MOSFET transistors.
Pulse frequency is adjusted to 36.5 kHz 0.5 kHz.
Maximum pulse time is 41% ±1.5% of the cycle time. Maximum pulse time results in
maximum current and arc voltage. When no pulses are supplied by the pulse width
modulator, no welding current will flow.
IC3 controls the pulse frequency, pulse time and blocking of pulses. The reference
voltage from IC3 is +5.1 V on circuit board 0486 886 880.
On circuit boards 0481 870 880 and 0481 870 885 the voltage is +2.5 V.
Transistor Q5 controls the primary winding of the pulse transformer.
NOTE:
The frequency and pulse time are very important parameters. If incorrectly ad-
justed, they can result in transistor failure in the main circuit.

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9 Gate circuit
The driver stage for the MOSFET transistors provides control pulses to the gate--source
of the power transistors. There is a separate output for each switching unit.
All gate circuits are galvanically isolated from other circuits on the board.
The insulation voltage between the pulse width modulator and the gate circuits is 4 kV.
WARNING: the gate circuits are at mains voltage.
The two gate circuits are identical, and so only one is described here.
When Q5 conducts, a voltage pulse appears at the secondary winding of the
transformer. This pulse is led via D21, D22 and connection E01 to the gate of the
MOSFET transistors. It returns via the source, connection E02, D24 and C46. The peak
gate -- source voltage is 14 V.
The presence of the gate pulse between connections E01 and E02 charges capacitor
C46 to 3.3 V. When Q5 is turned off, the voltage from the pulse transformer changes
polarity, resulting in transistors Q6 and Q7 starting to conduct. This results in a gate
voltage of --3.3 V, turning off the MOSFET transistors.

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CHECKING THE GATE PULSES
If circuit board AP02 or AP03 has failed, the gate pulses must always be checked. Remove
connections XS04 and XS05 (gate pulses), and connect a gate load to connections E01 and
E02 and to F01 and F02.
Gate load
IMPORTANT: never check the gate pulses when AP02 and AP03 are connected:
always use a dummy gate load.
The gate pulse minimum level must be --2 to --4 V, and the maximum level 13.5 to 16.5 V.
Frequency must be 36.5 kHz ±0.5 kHz. Check that the maximum pulse time, measured at a
voltage level of +5 V, is 41% ±1.5% of the cycle time.
If the gate pulses are not within these tolerances, AP01 must be replaced.
After replacing AP01, the machine must be soft--started, as described on page 25.
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Gate pulses as measured across the dummy gate load on circuit board AP01 between
connections F01 and F02.

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CIRCUIT DIAGRAM, CIRCUIT BOARD AP02
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AP02 (POSITIVE) CIRCUIT BOARD 481 803 --880 / --882 / --889
The --880 variant is used in the LHN 140, the --882 variant in the LHN 200 and the --889
variant in LHN 130.
The --889 variant has the same design as the --880 variant, the only difference is that transistor
Q6 isn’t mounted at the --889 variant.
Individual transistors must not be replaced: if the circuit board is faulty, it must be replaced
in its entirety. In addition, circuit board AP03 must also be replaced.
Instructions on removing and fitting the circuit board are to be found on page 28.
A01,A02 Connections A01 -- A02 are for the gate pulses from circuit board AP01.
D1--D3 Transient voltage protection.
D5 Back--emf protection diode (squelch diode) for main transformer TC02 when
the transistors turn off.
F1 Fuse, for protection of circuit board AP01 if circuit board AP02 fails.
Q1--Q8 MOSFET transistors. These require a special instrument
(see MOS TESTER on page 24) for testing.
Due to a change to transistors with higher current rating, the circuit board may
have one transistor less than specified in the diagram above.