Where to repair a welding inverter

Repairing a welding inverter: principles and rules, how to do it yourself

Inverter-type welding machines these days are reliable assistants in the performance of work by qualified specialists . Their breakdown and subsequent repair by a technician can take a long time, and downtime can affect the efficiency of the work and loss of money. Some people resort to repairing the device themselves.

Do-it-yourself repair of inverter welding machines is quite simple if you know the typical faults and have the necessary equipment and spare parts. Both measuring equipment such as multimeters and oscilloscopes, as well as a regular powerful soldering iron, high-quality flux and solder to replace damaged elements will help here. This leads to significant savings on maintenance costs, since you will only have to contact specialized service centers in the event of major or fatal malfunctions.

How does a welding inverter work?

An inverter apparatus is a direct current source that ensures the ignition and continuity of the electric arc during welding of structures and metal products. This is achieved by high-frequency transformation of high current, which leads to a reduction in the size of the transformer and makes the output current more stable. The required current parameters are achieved in several stages:

• primary rectification of current coming from the network;
• transformation of rectified current into high-frequency current;
• an increase in current strength by a high-frequency transformer, which leads to a decrease in its voltage;
• secondary rectification to a given value.

The current is rectified using diode bridges of the required power; the frequency is regulated by high-power transformers, which, having a high frequency, provide the required output current.

Design of inverter devices

Most welding inverters have a block structure, where each of the blocks can, in turn, be divided into its own components. There are three main blocks:

• power unit;
• control unit;
• power block

The power supply stabilizes the input current. It is usually separated from other elements by a metal partition. It consists of capacitors that store charge, a choke control system assembled on diodes, and a transistor-controlled multi-winding choke.

In turn, the power unit, which controls current conversion processes , consists of such parts as:

• primary and secondary rectifiers - assembled on the basis of diode bridges, in the case of the primary one capable of withstanding a current of up to 40 amperes, a voltage of up to 250 volts and a frequency of 50 Hz, and in the case of a secondary one - powerful diodes capable of supporting a current of 250 amperes with a voltage of about 100 volts ;
• inverter converter - a power transistor with threshold values ​​of power, voltage and current power, respectively, 32 amperes, 400 volts and 8 kilowatts;
• a high-frequency transformer consisting of copper tape windings, making it possible to increase the current strength to 250 amperes with a voltage in the secondary winding of the transformer not exceeding 40 volts.

Thermal and power protection of the power unit is carried out by thermal switches and special boards built on the basis of logic chips of the 561LA7 type or its analogues (CD4011 or K176LA7, for example). Capacitors and resistors are part of high-frequency filters that protect converters and rectifiers. To cool all parts of the inverter, small-diameter fans (up to 60 mm) and radiators are used to remove heat from the hottest electronic elements of the boards.

The control unit, as a rule, is assembled on the basis of either a master oscillator or a wide-pulse modulator. It also includes resonant chokes and capacitors.

Typical inverter faults

Repairing a welding inverter with your own hands should begin with establishing the reasons for the failure of the device. There can be two such reasons: an incorrectly selected mode of operation of the device (for example, when its power is not enough to cut thick metal) or malfunctions in the power and electronic parts.

Signs of malfunction of the device help to understand the cause of the malfunction. So, if during the welding process there is instability in the combustion of the arc or metal spatters, you should check that the current value is set correctly. It must be selected for each electrode depending on its length, thickness and type. The welding speed also depends on the current strength.

If the welding electrode sticks to the surface of the part, but the current value is set in accordance with its characteristics, you should check the length and thickness of the wire of the extension cord used, since electric cables of short length, no more than 40 meters, and a cross-section of more than 4 should be used for welding square millimeters. Several other reasons for this may be a drop in network voltage, a poorly prepared welding surface, oxidation of key elements of the inverter power circuit, and poor contact of the inverter units in the panel sockets.

If the machine turns off when welding parts for a long time, it most likely needs to be allowed to cool down, as the overheating protection is triggered. Half an hour is enough to continue work.

The inability to turn on the device can indicate many problems. First of all, you should check the stability of the voltage in the network, since if it drops below 190 volts, the inverter will not work.

How to repair a welding inverter with your own hands

When starting repairs, you first need to remove the inverter housing, inspect it for dust and check the main power elements.

Signs of oxidation and darkening due to overheating on the boards of the main units, swollen capacitors, burnt out parts, grooves on the legs of electronic elements and lack of contact between the legs and the board as a result of poor-quality soldering, all this can lead to loss of performance. If it is possible to visually identify such elements, they are desoldered from the boards.

In addition to a powerful soldering iron, a solder suction, low-melting alloys to simplify the removal of some parts in the soldering of which were used, for example, lead-free solder, braids of copper threads, which allow you to remove large accumulations of solder near the legs of the elements, and, of course, high-quality flux that improves heat transfer, will be useful here and allowing the solder on the board to melt more easily.

Replacement is made with parts with the same markings or similar ones, selected by comparing the main characteristics - capacitors can be of slightly higher capacity, for example. Broken wires must be connected with similar cross-sectional thicknesses and heat-shrinkable tubes must be used at the points where two wires are soldered together.

If replacing the most visually noticeable damage to the boards does not help, you should start testing the electronic circuits. The most vulnerable place from which you should start dialing is the power unit with transistors. If the transistors do not dial in accordance with the norm, the fault could also affect the driver that drives them.

The most difficult repair that you can encounter when servicing an inverter is the repair of the key control board, which supplies control signals to the gate buses of the key block. Here it is necessary to use an oscilloscope, since only with its help can you see the presence of these signals and the stability of their passage to the control unit.

Repairing the device with your own hands, having certain skills and parts at hand, is not a problem. But if you have no experience working with a soldering iron or understanding the operating principle of radio-electronic parts, it is still better to entrust such repairs to professionals. The inverter operates with high currents and, if repaired incorrectly, can permanently fail and threaten the purchase of a new device.

Source: https://tokar.guru/svarka/remont-svarochnyh-invertornyh-apparatov-svoimi-rukami.html

Repair of welding equipment

WELDING LEAGUE | Repair of welding equipment

The company "LIGA WELDING" specializes not only in the sale of equipment, we also provide diagnostics and repair services for welding machines in Moscow. Inspection of warranty installations is carried out free of charge. Correction of defects and malfunctions identified by a specialist outside the warranty is paid for along with diagnostic work

The following units of domestic and foreign production are subject to warranty and post-warranty adjustment:

• Diesel and gasoline power plants;
• Welding generators;
• Inverters; welding inverters (MMA, TIG, MIG);
• Welding transformers;
• Air plasma cutting equipment (CUT);

Type of work Cost

Standard diagnostics of the device, including disassembly and assembly	from 500 rub
Replacing the switching element (power switch, output socket, fan)	from 400 rub
Replacing the inverter board	from 800 rub
Transformer replacement	from 1,000 rub.
Checking the device on a rheostat	from 400 rub
Checking the welding machine	from 400 rub
Power supply repair	from 2,000 rub.
Repair of output power rectifier	from 2,000 rub.
Control board repair	from 2,000 rub.
Repair of IGBT power unit - converter	from 2,000 rub.
Cleaning the device	from 500 rub
Mechanical work	from 1,500 rub.
Repair of secondary power supply	from 2,000 rub.
Oscillator board repair	from 1,200 rub.
Replacing the gas valve	from 720 RUR
Wire Feeder Repair (MIG)	from 1,500 rub.

Warranty repairs of welding machines are carried out only if you have a correctly completed warranty card. Welding generators that show signs of external damage or have broken seals are not covered under warranty. Diagnosis and repair of a device breakdown can last from 1 hour or more - it all depends on the degree of complexity of the damage and the need for partial or complete disassembly of the device.

Repair of welding equipment is out of warranty

The repair period and price for inverter welding machines of Russian and foreign production without a warranty card are agreed with the customer after mandatory detailed analysis and diagnostics. The welding machine must be cleaned of dust and dirt. Welding quality after repair of the welding inverter will correspond to a high level.

The most common causes of damage to generators

Statistics, which were formed on the basis of conclusions from the diagnostic results of welding equipment, indicate that the most common causes of defects in their operation are incorrect handling of the unit during operation. It is worth knowing and understanding the following:

• Typically, repairs are required for welding units, in which the established cycle of alternating welding under load and with idle speed is regularly violated. The duration of switching on the unit should not exceed the maximum value specified in the product passport.
• The power of the connected electric generator must exceed the power of the welding installation by at least 2 times. Fluctuations in the network and sudden surges in voltage cause the device to short-circuit.
• Unprofessional handling of the installation, ignoring obvious faults, untimely cleaning and purging - all this has serious consequences and has a negative impact on the final result without timely repair of the welding machine.

Welding machine service

Our company maintains an adequate and loyal pricing policy regarding the repair of welding equipment. For example, the cost of analyzing a device malfunction starts from 900 rubles (disassembly and assembly of equipment is included in the price), and replacing the inverter board starts from 800 rubles.

Source: https://www.ligasvarki.ru/info/repair.php

Do-it-yourself repair of inverter welding machines

The difference between an old welding transformer and a new inverter welder is about the same as between the first Daimler Benz cars and a modern Mercedes.

The inverter is much lighter than its heavy-duty predecessor and has built-in functions that previously could only be dreamed of, for example, the ability to control the welding current value or a function to prevent electrode sticking.

But the brilliantly conceived idea has a significant drawback - the electronic filling fails much more often than the “oldies”, and repairing inverter welding machines requires considerable knowledge and skills. Any attempt to repair equipment blindly, without preparation, is fraught with fire or even injury.

Of course, situations where an electronic welding machine burns out like a candle and cannot be repaired further are extremely rare. In practice, repairing a welding machine can be much simpler than it seemed at first. In 90% of cases, power circuits fail, and in 50%, sensitive control elements of the circuit fail. But in order to repair inverter welding machines with your own hands, desire is not enough; at a minimum, you will need the following equipment:

• A digital tester or a multimeter, it doesn’t matter which one, it is possible with the function of checking transistors;
• Soldering station, you can make it yourself, but be sure to have a temperature-controlled hairdryer and a working low-voltage soldering iron;
• Load rheostat.

In addition to the above, the work may require a syringe for pumping out solder, a brush, alcohol, a magnifying glass, a strong flashlight, an incandescent lamp with wires, and, of course, reference books for ordering spare parts.

Advice! Most professional repairmen have an oscilloscope at their disposal. For electronics repair, in fact, it is an indispensable thing when it comes to checking the operation of the device’s control system.

It’s not a fact that you will need an oscilloscope to repair a welding machine yourself, but in particularly difficult cases you simply cannot do without it.

Before opening the device and delving into the details of the breakdown, you need to find out two main details from the welder. Firstly, it is necessary to find out how and under what conditions the welding inverter broke down, and secondly, whether there were attempts to carry out repairs by other specialists.

The problem is that “hobbyists” often replace factory parts with the first components that come to hand. Without a diagram, it is very difficult to restore the value and brand of a part, which is extremely important for high-quality repair of a welding machine.

The welding machine restoration process is carried out in three stages:

Disassembling the device and inspecting internal damage;

Consistent diagnosis and elimination of identified problems;

Testing and checking the performance of the welding machine not by spark, as most amateurs do, but by a high-power ballast rheostat.

Often, amateur repairs of welding machines end with checking whether the arc lights or not. Using a rheostat allows you to check one of the main performance parameters of a welding inverter - the ability to regulate and adjust the welding current under load.

Before you begin repairs, you need to understand and find out for yourself how the device works and what are the features of its operation. For example, look at a typical diagram or block diagram, then it will become clear what and where is on the board.

Stage one, we determine the problems by external inspection of the board

To gain access to the internal filling of the welding unit, it is necessary to free the electronic board from the housing and the power cord.

Advice! If before repair the device was plugged in for testing, before disassembling the welding inverter, carefully close the output couplings under the welding hoses using a pair of wires and a regular 100-150 W incandescent lamp. This will help avoid electric shocks.

To disassemble, you need to remove two or four screw or self-tapping fastenings of the housing and pull out the wires from the connecting chips. For repairs, a bare circuit board is left, studded with electronic parts. First of all, we inspect it, trying to identify burnt or damaged elements critical for repair, burnt board tracks, black resistors and swollen capacitors.

In the vast majority of cases, the following elements of the welding machine board fail and must be repaired:

• A powerful ballast resistance that discharges capacitors in the power block of the circuit. If the power supply is working properly, then when you try to turn on the welding machine, the capacitors will instantly gain a rather large capacity and a voltage of 300V. If during repairs, in the absence of a resistor, you turn on the welding machine and accidentally touch the terminals with your hands, you will receive an extremely painful electric shock, almost like an electric shock;
• Field effect transistors. They are easy to find and are always mounted on massive aluminum radiators. If the resistance burns out, repair and replacement of at least one of the transistors is almost always required;
• If the welding current is not regulated, then most likely the driver, one of its channels, or the operational amplifier included in the control circuit will need to be repaired.

Of course, the above list for repairs is the most common, but not exhaustive. For example, a temperature sensor that monitors overheating of the welding machine, a current transformer working in tandem with an op-amp, elements of an input diode bridge, and much more may burn out. Therefore, repairing a welding machine must begin with testing the elements along the circuit.

The second stage of repair, we check the circuits by testing

During repairs, you need to check the most loaded elements of the board. We turn it over with the back side up and use the sharp probes of the tester, piercing through the layer of protective varnish, to check for a short circuit. First, let's check whether the rectifier diode bridge at the output is broken. Repairing diodes is a rather rare thing, unless water gets inside the welding machine or a short circuit occurs on the cord. We measure the bridge at the entrance in the same way.

After the power supply, we move on to the most critical places in the power part of the circuit. This is a pair of powerful capacitors and field-effect transistor switches. To repair, it is necessary to establish the presence of resistance between the collector and the emitter, or more correctly, the drain-drain, drain-gate transitions. In 99% of cases, field-effect transistors fail first, resulting in a short circuit between the collector and drain.

Besides them, the second candidate for repair and replacement is the welding machine board driver. But repairing it will require very serious skills and knowledge. Therefore, if, after replacing the transistors, faults are identified in the driver channels, it is better to entrust its repair to a more qualified specialist.

How to check driver integrity

Looking ahead, we can say that after dismantling the keys or field-effect transistors, the need for driver repair is initially determined by the state of the reference resistors connecting the driver channel to the gate of the field-effect transistor - the switch.

To do this, simply trace the path with your finger along the board from the gate location to the first resistor.

We check it for an open circuit; if the resistances of the resistors in each channel are approximately the same, then we can assume that the control device is 99% in working condition.

Otherwise, you will have to contact a specialist to repair the welding machine.

The simplest repair of a welding machine

To repair the unit, you will need to remove the old transistors and replace them with new parts. Each key is attached to a massive aluminum radiator with a bolt. After removing the bolts, unscrew the screws securing the radiators.

For repairs, you will need to carefully desolder the field-effect transistor using a soldering station hair dryer; this is done with the utmost care so as not to damage the tracks and mounted mounting.

When soldering, the transistor must come out without force, otherwise the tracks will rise, and the cost of repairing the welding machine may jump several times. The desoldering area must be freed from solder using a blower or syringe and cleaned of burnt varnish.

Before installing new field-effect transistors - switches, you need to repair the ballast resistance. Instead of the old resistor, we solder a new part at 47 Ohm, 10 W. In addition, we call the capacitors and suppressors installed according to the scheme on the field paths.

To continue the repair, it is necessary to check the shape and size of the signal coming through each driver channel to the gates of its switch - a field-effect transistor.

Before connecting the oscilloscope, it is recommended to connect a capacitor of several hundred picofarads between the drain and the gate, thereby simulating the gate capacitance of the transistor.

This method allows, during the restoration of the welding machine board, to optimally load each driver channel, so the signal arrives in the form in which it exists in real conditions during welding work.

After soldering the capacitors, the oscilloscope probes are connected, and the power to the welding machine board is turned on.

The shape of the signal confirms that the repair was performed correctly; the gates of the transistors receive a signal from the driver of the required shape and size.

All that remains is to attach the new field-effect transistors with heat-removing paste applied to the aluminum radiators. Radiators are installed on the board, and the legs of the transistors are soldered one by one. The restoration of the welding machine is almost complete, all that remains is to test the device.

Conclusion

To do this, we connect a 40 W lamp to the output contacts of the welding machine board and turn it on; if the lamp lights up at full intensity, it means that the restoration of the output circuits has been completed successfully.

To make sure that the device is fully operational, a rheostat is connected to the welding hose couplings and the voltage at the output terminals is measured with a tester.

If by turning the knob the voltage at the clutch terminals smoothly changes from 60 V to 10 V, then the device is fully operational, otherwise the operational amplifier in the control circuit needs to be changed.

Source: https://rusolymp.ru/raznoe/remont-invertornyh-svarochnyh-apparatov-svoimi-rukami

Do-it-yourself welding inverter repair

Repair of welding inverters is important work that is carried out in most equipment repair service centers.

However, if you have the skills to maintain electrical equipment, you can perform restoration work yourself.

Let's look at the main components and service features.

General information

The inverter is a product of the development of semiconductor technologies, for example, Cascade and Laurel. Compared to transformers, they compare favorably with the following parameters:

• Light weight;
• Compact dimensions;
• Seam quality;
• Economical energy consumption;
• Additional functions.

Thanks to the last point, inverters are valued by novice welders, because they can facilitate the process of joining materials. The following functions are implemented on modern devices:

1. Hot start . Simplifies arc formation by increasing the current level before starting work.
2. Anti-stick electrode . If there is a danger of sticking, the current level is automatically reduced, allowing the connection to continue.
3. Arc Force . As the arc length increases, the automation independently regulates the current strength, preventing breakage. This function is especially useful when the seam is directed vertically.

Design and operating features

Schematic diagram of a welding inverter.

Inverters produce high-frequency current, due to which the welding arc is stable and the seam has a uniform structure . The operating principle is based on multiple conversion of electrical energy. As a result, the voltage decreases, and the current increases and rectifies, converting into direct current. It is used to perform connection work.

To repair welding machines, you need to have an understanding of the structure of the equipment. The main components of the units under consideration are:

1. Power unit . It is responsible for providing energy to the power part of the device. Consists of a rectifier, a nonlinear charging circuit and a capacitive filter.
2. Power point . Includes inverter, secondary rectifier, power transformer and output choke.

Source: https://svarka.guru/oborudovanie/vidy-apparatov/remont-invertora-svoimi-rukami.html

Do-it-yourself repair of inverter welding machines: how to repair if it doesn’t work, reasons + video

The inverter is used by experienced welders and amateurs. This is a modern and convenient welding machine. It is more compact than a welding transformer and much lighter. Thanks to this, the inverter can be easily used for field and high-altitude work. The price of the device ranges from 3,000 rubles. It's easy to use. The inverter is equipped with electronics that facilitate operation. Therefore, many beginners in welding purchase it.

Design of welding inverters

Unlike a transformer, which consists of electrical components, an inverter is equipped with electronics. The inverter transformer is very small, no larger than a pack of cigarettes. If a 160 A welding transformer weighs about 20 kg, then the same welding inverter transformer weighs 250 g, which is why the inverter is so compact and light.

Basic elements of a welding inverter

All elements are enclosed in a metal case. A wide adjustable shoulder strap is attached to the top. The device is comfortable to carry and climb to heights. The case has additional ventilation grilles for efficient cooling. The device has two connectors: “plus” and “minus”. The ground cable and the electrode holder cable are connected to them.

On the front of the case there is a control panel with a power on indicator and an overheat protection indicator, a power on button and smooth adjustment of the welding current. Models that provide different welding modes have a mode switch. The inverter is connected to the network using a power cable.

The base of the device has support legs.

Inverters stop working for four reasons:

1. Failure to comply with the conditions for proper operation of the device.
2. Incorrect operating mode selected.
3. Failure of electronic components of the microcircuit.
4. Damage to electrical components of equipment, such as wires and contacts.

DIY welding inverter repair

To understand how to repair an inverter, let’s look at its circuit diagrams and operating principle.

Welding inverter circuit and principle of operation

A welding inverter consists of many elements.

Welding inverter circuit

Operating principle of the inverter:

• The 50 Hz AC input current passes through mains rectifier 1 and is converted to DC. Along the way, it is smoothed out by mains filter 2, consisting of capacitors. Welding inverter circuit
• Using a frequency converter 3, consisting of transistors, the direct current is again converted into alternating current, but with a higher frequency of up to 100 kHz.
• The resulting alternating current is transmitted to the high-frequency welding transformer 4 and then to the power rectifier 5. The voltage is reduced to the value required for welding.
• These processes are controlled by control system 6, consisting of a PWM controller microcircuit. It controls voltage, welding current, arc force, stabilization. This helps to make a quality seam.

Welding inverter device

Problems associated with operation and incorrect settings of the inverter:

• The welding arc burns unevenly or too strongly, resulting in excessive spatter of the electrode material. This occurs due to incorrectly selected welding current. When setting the current, it is necessary to take into account the thickness of the metal workpieces. Regarding this, select the type of electrode and its diameter. When purchasing electrodes, read the information on the packaging. The recommended current is indicated there. If this information is missing or the packaging is lost, then you can calculate the welding current yourself. First multiply 30, then 40 by the diameter of the electrode and get the welding current interval. For example: 30 * 3 mm = 90, 40 * 3 mm = 120. This means the current range: from 90 A to 120 A. If the welding speed is low, then the current value must be reduced.
• The welding electrode often sticks to the metal workpiece during operation. The main reason is low network voltage. If the inverter is designed to operate with low voltage, then the cause of the malfunction may be connecting a load whose level is below the minimum level. Or there is poor contact between the instrument modules in the panel sockets. Tighten the fasteners. The voltage may drop at the input of the welding machine if you use an extension cable with a cross-section of less than 2.5 square millimeters. If your extension cord is too long, more than 40 meters, then this also affects the voltage. In an electrical circuit, contacts oxidize or burn over time. This affects tension. Another reason for electrode sticking is poor preparation of metal workpieces for welding. They must be thoroughly cleaned of paint and rust with a wire brush.
• The inverter is turned on and the indicators show the same, but welding is not performed. This occurs due to overheating of the welding machine. Let it rest for at least an hour. If that doesn't help, check the wires. They could disconnect themselves or fail due to a break or short circuit.
• If the mains voltage is constantly cut off, check the characteristics of the safety device, i.e. the circuit breaker. It is designed for a certain current strength. For correct operation of the welding inverter, a current of up to 25 A is used. Automatic switch
• The machine does not turn on if the mains voltage is too low for welding work.
• During prolonged continuous welding, the inverter turns off. The device heats up to a certain level and the temperature sensor is activated. But this is not a malfunction. Turn off the inverter for 30 minutes and continue working.

Electronic components fail for the following reasons:

• Moisture penetrates into the body of the welding inverter as a result of working in rain or snow without a canopy.
• When using the device in places where construction work is taking place, a lot of dust collects under the body. This prevents the circuit's electronic components from cooling properly. Clean the inverter regularly. The smaller the device body, the smaller the cooling holes and the more often the inverter needs to be cleaned.
• Electronics fail due to ignoring the manufacturer's recommended operating instructions for the device. Read the instructions carefully and follow the rules.

Repair of inverter welding machines

Before starting to disassemble the device, check that all settings are set correctly and read the instructions. It contains not only recommendations for proper operation of the device, but also problems that can be quickly resolved on your own.

Diagnostics of the welding inverter

Unscrew the screws on the case and remove all its parts. Diagnostics begins with a superficial inspection of all elements and boards. There may be several of them:

• Board with power transistors. Board with power transistors
• Control board.
• Rectifier diode board.
• Mains voltage rectification board.

You need to carefully look for burnt tracks and damaged elements. If no damage is found, then carry out diagnostics with a multimeter:

• If the inverter does not turn on, set the multimeter to test mode and test the power cord and power button contacts. Check the charging resistor. If it is broken, the device will not work. The resistor is responsible for charging the capacitors.
• Set the multimeter to diode mode. Connect the probes to the inverter output terminals and swap them. Diodes ring in one direction, but not in the other. If the device shows ringing in both directions, it means the diodes are broken.
• Check the power transistors. On the board, place the black probe on the left leg, and the red one on the right, then swap the probes. The ringing should go in one direction.
• Place the black probe on the middle leg, and the red one on the left, then on the right. The ringing must be in both positions.

Replacing transistors

Transistors have a small resistance of hundredths of an ohm. But they pass through themselves a current of several tens of amperes. To avoid overheating, they are installed on aluminum radiators. A badly damaged transistor is usually visible.

Damaged transistor

• To replace the transistor, you first need to unscrew it from the radiator, and then remove the radiator itself from the board.
• To desolder the transistor from the board, you need to warm it up with a hairdryer. During dismantling, the tracks should not break.
• The surface of the radiator for the new transistor must be thoroughly cleaned with alcohol and polished. The surface of the transistor must be smooth. Any inclusion or grain of sand will create a gap between the transistor and the radiator. It is unacceptable. Apply a very thin layer of thermal conductive paste to the surface of the transistor that will be adjacent to the radiator. When tightening the transistor, the paste should come out slightly from under the housing. The thick layer will not come out and the transistor will be deformed. The component must be applied to the surface of the radiator and rubbed in a circular motion so that it lies across the entire area. It should stick.
• Screw the stuck transistor to the heatsink and insert it into the board. Solder the legs.

Driver board repair

If the transistor fails, it means that the elements of the driver board that drive the transistors are damaged.

Driver board

All components of the board are checked with a multimeter. Damaged ones are soldered off and replaced.

Rectifier repair

Input and output rectifiers are made in the form of diode bridges. To prevent overheating, they are installed on radiators.

Diode bridge

For diagnostics, it is unsoldered from the wires and removed from the board so as not to make a mistake in the event of a short circuit in the circuit. Faulty elements are replaced.

Diagnosis of capacitors with a multimeter

If the capacitor is discharged and we connect power to it, its resistance increases from zero. When fully charged, its resistance is infinite.

• Set the multimeter to 20 kOhm resistance mode.
• If the device was recently turned on, the capacitor retained its charge. To determine its performance, discharge the capacitor before testing. Using a multimeter probe, short-circuit the terminals of the capacitor.
• Connect the multimeter leads to the capacitor terminals. If the resistance was zero, then as the capacitor was charged from the multimeter it increased to infinity, the capacitor is functioning.
• But you still need to measure the voltage. Set the multimeter to DC voltage measurement mode in the range of 2000 mV. Connect the probes of the device to the terminals of the capacitor. The device should show voltage. Close the capacitor terminals and measure the voltage again. If it drops to zero, your capacitor is healthy.

Control board repair

All elements of the welding machine depend on the control board.

Control board

This is the most difficult block. It is diagnosed with an oscilloscope. Control signals are checked. If they do not arrive, all elements are checked with a multimeter and damaged ones are replaced.

Diagnostics and repair of a welding inverter - video

If you learn to independently identify and troubleshoot a welding inverter, you can avoid unnecessary repair costs at a service center.

Source: https://grounde.ru/remont-svarochnogo-invertora-svoimi-rukami.html

Repair of welding inverters and troubleshooting with your own hands: types of faults, their occurrence, repair

Quite often, home craftsmen are faced with the need to perform welding work. To do this they need special welding equipment.

Today, welding inverters are a fairly common type of similar device, which can increasingly be found among many owners. However, at a certain point this equipment may fail, which makes you think about repairs.

Moreover, in this case, it is not necessary to contact specialists; in some cases, you can return the welding machine to working condition on your own. The main thing is to know what exactly led to the malfunction and how you can eliminate it yourself without incurring unnecessary service costs.

DIY welding inverter repair diagram

When starting to repair inverter welding machines, you need to remember the following point: it is often difficult to understand, focusing only on the nature of the problem that has arisen, what exactly led to the cessation of operation of the device.

In such a situation, the owner has no choice but to check each element of the circuit . Therefore, in order for the repair to justify the effort and time spent on it and to provide the necessary result, the owner of such a device must have certain knowledge of electronics, as well as at least minimal skills in working with electrical circuits.

If he does not understand this aspect, then, having decided to independently repair the inverter welding machine, he only risks wasting energy and time without achieving his goal. It is possible that his initiative may worsen the operation of the device, and the actions he performs will cause new problems.

Basic malfunctions of welding inverters

If we consider all the problems that are diagnosed during the operation of welding inverters of any type, they can be classified into several groups:

• problems arising as a result of an illiterate choice of welding operating mode;
• problems caused by a malfunction or incorrect operation of the electronic components of the equipment.

Regardless of the nature of the malfunction, such a situation will not allow the owner to continue welding as usual. Various factors can lead to a malfunction in the operation of the welding inverter.

To determine the exact cause, it is necessary to check each of them in turn, starting with simple operations first and gradually moving towards more complex ones. After performing all the recommended diagnostic procedures, it may happen that the welding machine is still in non-operating mode.

In this case, it can be assumed that the problems are associated with a non-working electrical circuit of the inverter module. Most often, failure of an electronic circuit occurs for the following reasons:

• Penetration of moisture into the device. In most cases, precipitation contributes to this.
• If dust accumulates under the housing, favorable conditions arise to disrupt the proper cooling of the components of the electronic circuit. Equipment used on construction sites is often at greatest risk of contamination. To prevent the inverter from being damaged under such operating conditions, it should be cleaned regularly.
• Neglecting the manufacturer's recommendations regarding the appropriate mode of use of the inverter, operating without interruption. This can also be one of the reasons for malfunctions in the operation of the equipment’s electronics due to its overheating.

Common inverter faults

Typically, inverter devices fail due to exposure to external factors, as well as incorrect settings and neglect of recommendations for using the device. Among such situations, the following can most often be observed:

• The burning process of the welding arc is unstable or there is too much spattering of the electrode material. This can happen if the current was selected incorrectly. To avoid problems, you need to focus on the diameter and type of electrode, as well as the welding speed. The manufacturer solves this problem for the consumer, providing appropriate recommendations for determining the current strength on the packaging. If such information is not available, then you can use the following formula: the current is determined at the rate of 20-40 A for each millimeter of electrode diameter. If the welding speed is sufficiently slow, it is necessary to select a lower current value.
• The welding electrode is pulled away from the metal with force . This situation can arise due to several different factors. In most cases, this is caused by an extremely low supply voltage from the network to which the equipment is connected. If welding work is carried out using an inverter designed for operation at reduced voltage, then the cause of its failure may be a decrease in the voltage when a load is connected that does not exceed the level that corresponds to the minimum. Along with this, malfunctions may be associated with poor contact of the device modules in the panel sockets. To solve this problem, it is necessary to tighten the fastenings or fix the inserts much more tightly. If there is a voltage drop at the input of the device, the reason for this may be the use of a network extension cord, where a cable with a cross-section of less than 2.5 mm2 is used. Under such conditions, it is also possible to observe a decrease in the supply voltage of the welding machine during work. Equipment malfunctions can also occur due to an extension cord that is too long. You should not use a wire that is more than 40 meters in length, since in this case the device cannot operate efficiently. Otherwise, too much loss will be observed in the supply circuit. The cause of sticking may be burning or oxidation of contacts in the power circuit. Against the background of this phenomenon, tension can also, to a large extent, simply “sink.” You can encounter such a problem even when mediocre preparation of the elements to be welded has been carried out.
• When the inverter is turned on, the indicators show the operating status , but welding cannot be carried out. Typically, the cause of such a problem is overheating of the equipment, while it is quite difficult to see the glow of the control indicator or lamp, and the sound signal is not provided in the model used. Another reason for such a malfunction may be the independent disconnection of the welding wires or their damage.
• During welding, you may experience a constant power outage. Most often this is due to errors regarding the choice of circuit breaker for the electrical panel. For proper operation, this device must be designed for use with currents up to 25 A.
• The inverter cannot be turned on. You can encounter a similar problem if there is a low voltage in the network, which is not enough to create normal conditions for welding work.
• Turning off the inverter during prolonged welding work. The most likely reason for the device to stop working is the activation of temperature protection, but this should not be considered a malfunction. It is enough to take a break of 20-30 minutes, after which you can continue working.

Work technology

The DIY repair procedure consists of gaining access to the body of the device and further examining its filling. In some cases, the cause of the malfunction may be poor-quality soldering of elements, cables, and other contacts on the circuit boards.

Therefore, in such a situation, you can return the device to working condition by re-soldering . At the initial stage, you need to try to find out which elements have failed. This may be indicated by cracks, dark spots on the case or signs of burnout on the terminal board, as well as swelling of the top of the electrolytic capacitors.

After it has been possible to install the faulty components, they must be desoldered, and then parts that are identical or similar in characteristics to them must be installed in their place. When choosing replacement parts, you must pay attention to the markings on the body or use tables. When removing damaged elements, it is recommended to use a soldering iron with suction. This will allow you to complete the job with minimal time and avoid serious problems.

In some cases, the examination may not yield results. In such a situation, it makes sense to start ringing the elements using an ohmmeter or multimeter. Transistors have the lowest level of protection. For this reason, when repairing a device, it is necessary to first inspect them and check their functionality.

For the most part, power transistors are highly reliable. And if they nevertheless turn out to be faulty, then most often the contributing factor is the failure of the elements of the circuit “swinging” them. The elements of the latter need to be checked at the very beginning.

After completing the test, it is necessary to subject other elements of the board to testing.

When examining the board, you should pay attention to the condition of each printed conductor , where you need to make sure that they do not have breaks or burns. If burnt areas are found, they need to be removed and jumpers soldered. This operation is performed with your own hands according to the same scheme as when the PEL cable is damaged. If necessary, the contacts of each of the connectors present in the device should be checked. In some cases they will have to be cleaned.

DIY welding inverter repair

A welding machine is an integral tool when carrying out installation work that involves metal profiles. Heavy transformer welders have been replaced by inverter welders.

They are light in weight and more mobile, which is why they are loved by many craftsmen. During operation, typical and atypical breakdowns may occur, so it is important to know whether it is possible to repair the welding inverter yourself.

What is needed for this and how the troubleshooting process goes will be discussed in this article.

What is the difference between a welding inverter

The inverter welding machine got its name due to the transformations that occur in the circuit. The mains current that enters it has a frequency of 50 Hz, which means that the pulse changes 50 times per second. At the output of the inverter welder, the current frequency is close to constant, i.e., an equalization process occurs.

To achieve this, several modules are used, which are assembled into one or more circuits. At the input there is a primary block that performs equalization; it consists of a diode bridge. After the pre-rectifier, the current enters the inverter unit.

This is where transistor switches come into play; they ensure the conversion of direct current into high-frequency current, its maximum value reaches 100 kHz.

High frequency current flows from the transistor assembly to the transformer. A high-frequency transformer is mounted in this block, which reduces the voltage. This produces an increase in current strength, which is important for normal combustion of the electrode. In some models of inverter welding machines, the output current can reach 300 amperes.

The final module is another rectifier module, after which the current goes to the electrodes. This module is also assembled on a diode bridge. In this case, high power semiconductors are used.

In addition to the main elements, there are also additional ones, for example, all electronics need constant cooling, so a high-speed fan is provided that provides air exchange.

Causes of malfunctions

The lion's share of breakdowns of inverter welding machines occurs due to their improper operation. In some cases, the inverter welding machine may be stored in an inappropriate room where there is high humidity. If it gets on the electronics, it will short-circuit the components and cause them to fail.

Also, do not use the inverter welding machine during rain or immediately after it. Each inverter welding machine is designed for a rated load and exceeding it can lead to failure of the power modules. This reason may, for example, lie in the processing of thick metal with high currents.

This will lead to overheating and burnout of transistor assemblies or other elements.

Most inverter welding machines cope well with low voltage, but in some cases it can cause failure of one of the modules. It is worth remembering that when the voltage is reduced, the power of the inverter unit also drops, which reduces its efficiency, since part of the power is spent on increasing the output current.

In some cases, the cause of the breakdown may be poor fastening of the working or supply cable. If the contact is unreliable, then overheating occurs in these nodes, which can also cause a short circuit.

Insufficient cooling due to failure of the fan or covering of the ventilation holes also leads to failure of the circuit.

Note! Units may fail again after welding inverters have been repaired. This is due to the use of low-quality components. They should always be ordered from trusted sellers who provide wholesale supplies.

Common faults

There are a number of malfunctions that are encountered when working with an inverter welding machine. They are eliminated quite simply, so it is worth dwelling on them in more detail.

Unstable arc

Arc instability in an inverter welding machine can manifest itself in metal spattering or burning of the surface being processed. The reason for this is the incorrect selection of the output current for the thickness of a particular metal and electrode.

Some electrode manufacturers indicate on the packaging what current can be applied to a particular electrode. The appropriate value can be selected experimentally by simply turning the knob down.

If you are confident that the current readings on the output display of the inverter welding machine are correct, then you can use the table below.

In some cases, frequent sticking of the electrode to the workpiece may occur. This phenomenon is usually observed among beginners who do not have sufficient experience working with an inverter welding machine. But there is another reason for this process, it lies in the reduced voltage at the input.

In this case, the unit is not able to produce the required current for a specific electrode; it heats up and simply sticks, and the arc does not even begin to burn. It is also worth checking the reliability of the connection of the working cables.

In some cases, poor contact can cause the electrode to stick to the workpiece surface.

The problem can be eliminated by cleaning the bayonet fastenings of the working cables. To do this, you can use a solvent or fine sandpaper. It is important to check the extension cord with which the welding unit is connected to the power supply. If the conductor cross-section is narrowed, it may cause a voltage drop. This can be detected by heating the cable. Typically, for such purposes, an extension cord with a cable cross-section of at least 2.5 mm2 is selected.

It is also worth remembering that with a length of over 30 meters, losses are observed on the conductors, so either a larger cross-section or a shorter length is necessary. Another reason for electrode sticking is the quality and preparation of the workpieces for welding. If there is a large amount of rust on them, then it is better to clean it off with a grinder before work.

Below is a table that will allow you to select the wire cross-section and machine rating for the specific current strength of the welder.

No current output

The problem may manifest itself in the fact that there is power in the network, but there is no current at the output of the inverter unit, although all the signal lights may be on. In this case, it is worth paying attention to the condition of the unit.

If the light next to the thermometer icon on the control panel lights up, then the device has simply overheated. Therefore, it is worth waiting until the fan cools the internal components sufficiently.

It is important to carefully inspect the working cables; if they show signs of breaking or strong bending, then such a problem should be localized immediately by replacing the cable or cutting out the damaged part.

Sudden shutdown

Another unpleasant malfunction that can occur during a critical process is the random shutdown of the welding unit. The problem may not lie in the welding machine itself, but in the circuit breaker that is installed in the power supply.

If the permissible current is exceeded during consumption, it is triggered, stopping the supply. In some cases, the fuse of the welding unit itself may fail. This occurs due to sudden surges in the power supply.

You can install a bug if the task is urgent, but it is better to replace the fuse with a new one.

A sudden shutdown can also occur after prolonged operation. This may indicate non-compliance with the welding-rest regime. If this is the case, then the temperature sensor is triggered and simply stops supply due to overheating. It will not be possible to continue the work by force, so you will need to wait a cooling period.

Other faults

There are other breakdowns that do not have external manifestations. To identify them, there is a general algorithm that should be followed. First of all, the welding unit is inspected visually. Damage to the housing is detected, as well as traces of burnouts that can occur during a short circuit.

Next, all detachable connections are clamped and regulators and switches are checked. The fuse of the welding unit is inspected. It does not always look like a transparent flask with a thread. If the problem has not been resolved, then further inspection after disassembly will be required.

The metal case is dismantled to provide access to the internal components. They also need to be inspected visually.

Faulty elements are usually immediately noticeable. These could be swollen capacitors or melted elements. It is worth paying attention to the darkening that is on the board. In some cases, an item may appear normal on the outside but may actually be faulty. Next, the presence of voltages that should be on the circuit is checked. The presence of voltage at the input and after each block is checked.

To do this, you will need a high-quality multimeter that can withstand high currents. When the culprit block is identified, it is necessary to carry out testing and measurements of each individual element in order to determine the culprit. In this regard, repairing the Resanta welding inverter may be the most affordable and simplest. For welders from the company Resanta 220 and others, there are many freely available diagrams that can be used to determine the structure.

Several videos about repairing an inverter unit can be viewed below.

Summary

Self-repair of an inverter welding machine requires basic knowledge of circuitry, electronics and the laws of physics. Otherwise, it will be difficult to understand the main components and the reasons for their failure. In most cases, the failure of any component of an inverter welder is due to a malfunction of other components that do not clearly exhibit deficiencies.

Source: http://obrawa.ru/remont-svarochnyh-invertorov/

Do-it-yourself welding inverter repair: diagrams and diagnostics, how to repair

In a short time, inverter welding machines have gained unprecedented popularity among specialists. Despite the reliability of the power supply, repair of a welding inverter may sometimes still be necessary.

Diagnosis of a malfunction and replacement of a failed part, if you have some skill, can be done at home. To carry out repairs, you must first familiarize yourself with the design of the device and only then proceed with the repairs.

Common causes of breakdowns

Do-it-yourself repair of welding inverters is possible for the following faults:

1. Unstable welding arc.
   In most cases, such a malfunction is associated with an incorrect choice of the inverter operating mode. To select the optimal current strength, you can follow the rule: 20 to 40 amperes of current should be supplied per 1 millimeter of electrode diameter.
2. The appearance of forces when separating the electrode from the metal.
   A typical malfunction that occurs due to low voltage coming to the electrodes. The simplest way to solve this problem is to clean the contacts of the power supply from oxides and carbon deposits.
3. No welding jet.
   If there is no power when you turn the toggle switch to turn on the device, you should check the voltage in the electrical network.
4. Inverter shutdown during prolonged operation.
   As a rule, such behavior of the inverter can be associated with overheating. The way out is simple: let the device cool down and start working again after 30 minutes.

Scheme of an inverter welding machine.

When diagnosing a welding machine, the following faults may be detected:

• arising as a result of incorrect choice of welding mode;
• arising as a result of failure of electronic components of equipment.

In any of the above cases, you can repair the welding inverter yourself.

Most malfunctions of this welding machine unit are associated with the failure of electronic components.

The main types of electronic circuit faults are presented:

1. Moisture entering the inverter housing.
   Oxidation of conductive paths due to moisture ingress can cause a breakdown in contact between the main components of the device.
2. Formation of a large amount of dust on the main working elements.
   Excessive dust contamination of inverter elements can disrupt the natural circulation of air in the housing and lead to overheating of electronic components.
3. Selecting the wrong operating mode for the inverter, resulting in overheating of electronic components.
   Inverter failure due to overheating of electronic components is one of the most common failures.

Most inverters use:

• input rectifier;
• output rectifier;
• key control unit;
• cooling system.

General procedure for diagnosing welding inverters

Before repairing the device, you should check the functionality of the cooling system. Cooling radiators clogged with dust remove heat from the power elements much worse, which means the fins should be completely cleaned of dust and other debris.

Repair of inverter welding machines should begin with diagnosing the input rectifier.

To fully check this node you should:

• disassemble the module;
• remove the radiator;
• remove the diode bridge;
• ring the contacts of the diode bridge.

If no problems with the diode bridge are identified, you should move on to the next module - the output rectifier.

Typical inverter faults.

The functionality of the output rectifier is checked using the following algorithm:

• disassemble the module;
• unsolder the diode assemblies;
• ring the diodes.

In addition to diodes, the output rectifier circuit contains radiators that should be installed back after repairing the module.

After examining the output rectifier, you should proceed to diagnosing the key module.

This inverter module consists of:

• four groups of transistors;
• key control boards;
• smoothing rectifiers.

The procedure for examining the key module is as follows:

1. Checking transistors.
   As a rule, a faulty element is clearly visible to the naked eye. If this is not the case, then you should check the sequence of all available transistors with a tester.
2. If measurements with a tester do not produce results, you need to diagnose the transistor assemblies using an avometer, measuring the resistance.
3. If all components appear to be in good working order, all transistors should be unsoldered one by one.
   This diagnostic method is suitable if there is a short circuit on the board.

Most inverter problems can be diagnosed by carefully inspecting the electronic components. If defective parts are identified, you should immediately remove them and replace them with similar characteristics.

Repair of inverter power unit

Electrical circuit of a welding inverter.

To repair the inverter power unit, the following tools may be required:

• pliers;
• two soldering irons with a power of 40 and 100 watts;
• screwdrivers of various types;
• wrenches and socket wrenches;
• knife;
• wire cutters;
• tester for electrical network;
• oscilloscope;
• calipers;
• micrometer.

The most typical breakdown of the power unit of a welding inverter is the failure of a powerful transistor. In most cases, a damaged transistor can be identified visually: it has defects, burnouts or deformation. Repairing an inverter if a defective transistor is detected is reduced to replacing it.

There are many cases when a transistor breakdown is only a consequence and not a cause. With this development of events, replacing the transistor assembly may not give a visible effect.

Before repairing the diode bridge, you should check the functionality of all elements. This can be done by alternately measuring the resistance on the legs of the elements. If the resistance between the multimeter probes located on the diode legs is zero or infinity, then this element should be replaced.

New transistors or diodes should be selected from analogs with similar characteristics. As a rule, analogues of the vast majority of models of electronic components are available for sale.

Components of a welding inverter.

When repairing the inverter power unit, you should adhere to the following rules:

1. Do not use an electrical appliance with an open insulating casing.
2. Diagnostics and replacement of all electronic components must be carried out on a de-energized welding machine.
3. It is best to remove accumulated dust and debris from the device using a compressor or a can of compressed air.
4. Cleaning the board from sticky traces and used flux should be done using plastic-neutral solvents. It is recommended to use a special brush for cleaning electronic components.
5. A working device should be stored in a disconnected state and with the casing completely closed.

We carry out welding inverter repairs on our own

Any equipment breaks down at some point, this also applies to welding equipment, which is sometimes operated in extreme conditions. But repairing such welding machines in a workshop can be quite expensive.

In addition, during operation, prompt repair of breakdowns is required. Fixing a fault with your own hands is both faster and cheaper; you just need to know the principle of operation of the device and the semiconductor element base.

We will tell you in detail how to correctly determine the malfunction of the welding unit and how to repair it with a minimum of equipment.

Operating principle of a welding inverter

The breakdown of complex electronic equipment requires a quick response, and professional repairs are expensive and slow. You can repair inverter welding machines yourself if you have certain knowledge in the field of radio electronics and the principles of operation of such equipment.

It is necessary to have a multimeter with a resistance measurement mode, as well as a dual-beam oscilloscope, which will allow you to make final adjustments or identify a malfunction.

Often the cause of a breakdown is on the surface and can be determined by visual inspection after opening the case, but there are also more complex faults.

Opening the case and visual inspection is possible only after disconnecting the device from the electrical network; remember that after dismantling you lose the right to warranty repairs.

Before you start repairing a welding machine, you need to understand what parts and functional elements it consists of. To effectively repair it, you need to know the ratio of input, output voltages and signal shapes on each component of the product.

The inverter welding machine consists of the following elements:

• low-frequency rectifier unit with a filter that converts alternating mains voltage 220/380 V into direct voltage;
• inverter circuit that converts direct voltage into high-frequency alternating voltage up to 100 kHz;
• high-frequency step-down transformer, which provides welding current up to 300 A;
• output rectifier for welding in MMA mode;
• a control device that provides, through feedback, stable characteristics when welding in different modes;
• welding wire feed unit for MIG/MAG modes;

A malfunction can occur in each of these components, so the repair of welding machines should begin with a progressive analysis of the operation of its components. First, you need to read the instructions, where possible breakdowns and how to fix them can be explained. You also need to familiarize yourself with the operation of the automatic protection of the device and the operating voltage limits.

It is important to remember that the inverter is a source of increased danger, and careless handling of it can lead to electric shock, therefore, if you are not confident in your abilities, it is better not to start repairs.

Diagnosis of hardware faults

A very common cause of problems is failure to comply with the operating conditions recommended by the manufacturer. Some products can operate over a wide range of temperatures and voltages, but this is the exception rather than the rule. Various malfunctions of welding inverters occur quite rarely, thanks to an effective protection system against short circuit currents when electrodes stick and from gross mistakes by an inexperienced welder.

Therefore, the following circumstances may be the cause of incorrect operation:

1. discrepancy between single-phase or three-phase voltage recommended by the technical characteristics of the inverter;
2. safety circuit breaker less than 25 A;
3. an extension cord longer than 30 m is used;
4. cross-section of the supply wire is less than 2.5 mm2;
5. poor contact of the negative wire with the part being welded;
6. the welding current is incorrectly selected;
7. dustiness of the radiators of the cooling system of power elements, which leads to the activation of temperature protection;
8. penetration of moisture into the housing;
9. non-compliance with the load duration regime.

If all of the above reasons are absent, and the equipment does not work, then you will have to open the case. The next stage of repairing a welding inverter with your own hands is an external inspection, which may allow you to localize the fault.

Traces of burnt tracks may be found on the boards, indicating failure of resistances, capacitors or semiconductor elements. Here, to replace it, you need to use a soldering iron, and it is possible that the reason for the failure of parts is a breakdown of semiconductors subsequent to the circuit. In this case, you will need a multimeter with resistance measurement mode.

The resistance of the parts is measured with the power off and you will need to unsolder the power diode or transistor for a more accurate and reliable result.

A zero or infinite resistance value indicates that it is faulty and needs to be replaced. You need to desolder the transistors very carefully first, unscrewing them from the radiator and ensuring the integrity of the conductive paths on the board. Some types of faults are quite difficult to determine, since the failure of one element of the circuit solution leads to disruption of the operation of other parts.

Therefore, diagnosing and repairing welding inverters with your own hands requires good knowledge and skills. To more accurately determine the causes of malfunction, you will need to use a dual-beam oscilloscope. It is needed to localize the faulty unit by examining the amplitude and shape of the input and output voltage.

Repair methods for welding inverters

The reliability of the semiconductor elements of the welding machine and the efficiency of the protective systems practically eliminate their failure. But if this did happen, then most likely the cause was moisture getting into the device or foreign metal objects causing a short circuit. In this case, repairing a welding inverter consists of diagnosing the breakdown, drying the device and removing foreign objects, as well as replacing faulty parts.

https://www.youtube.com/watch?v=I6aDV1yFyjE

For repairs you will need the following tools and equipment, namely:

• screwdriver and wrenches;
• soldering iron, solder, flux or rosin;
• excess solder suction device;
• multimeter with resistance, current and voltage measurement modes;
• dual-beam oscilloscope for diagnostics and final adjustment;
• electrical diagram of the faulty product or similar;
• heat-conducting paste;
• means for washing contacts, conductive paths and radiators;
• a board made of non-conducting material for easy diagnostics of boards when the mains voltage is turned on.

It is important to take into account that failure of the power elements of the device entails possible burnout and malfunction of adjacent capacitors, resistors and stabilizers, as well as control microcircuits.

After identifying a malfunction of the power elements or control circuits, you should disconnect the parts from the radiators and unsolder them from the boards. In this case, you need to use a device for suctioning excess solder to make it easier to dismantle the element and preserve the board tracks from deformation.

Otherwise, you will have to install additional buses, which does not improve the performance of the board. Then it is necessary to clean the dismantling site from flux and scale, and the radiators from the remnants of old thermal paste and possible carbon deposits.

Make sure that the components closest to the circuit are in good condition and, if necessary, replace them.

After installing and assembling new semiconductor or other parts, you need to be sure of the integrity of the conductive paths, and if they are damaged, take measures to eliminate the deficiencies. Apply a new layer of thermal paste to the cleaned radiators and secure the power radio components. Then, using a tester, make sure that the connection is working properly and turn on the power supply to the inverter.

Let's sum it up

Thus, if you have certain qualifications, it is quite possible to repair welding inverters yourself. This will allow you to save time and a lot of money. But in case of difficulties, you should always turn to reference literature and consult professionals. Joint efforts will always ensure a positive result.

Source: https://electrod.biz/apparat/remont-svarochnogo-invertora.html