DIY LED strip repair

In detail: DIY LED strip repair from a real master for the site my.housecope.com.

LED strips are widely used in decorative lighting and functional lighting, but from time to time they fail completely or partially, in this regard, it becomes necessary to repair or replace them. Often, you can only do with replacing a small section of it, which will reduce repair costs. In this article, we will look at typical problems with a Led strip.

Before proceeding, I note that the main emphasis will be on common tapes with 12V power supply, 24V tapes are similar in design, and at the end, the features of repairing network (220V) tapes will be considered.

Design

Before considering the malfunctions, you need to figure out what the LED strip consists of and why it is flexible. The led strip can be divided into two parts:

LEDs and current limiting resistors.

The flexible PCB is coated on one side with an adhesive.

On the second side there is a metallized layer - conductive tracks. They are made in the form of thin copper strips. SMD LEDs and current limiting resistors are soldered onto the conductive tracks.

The front side can be painted white, then the tracks are not visible, they can be seen by close examination of the structure of the tape.

If we are talking about white LEDs, then a voltage of about 3V is needed for their glow, and the tape is powered by 12, how is this done? The tape consists of segments of three LEDs connected in series and 1 or more resistors.

For the operation of three series-connected LEDs, 8.5-9.5V are needed, the resistors are selected in such a way as to provide the rated current of the LEDs and burn off an extra couple of volts. Each such segment operates on a 12V voltage.

Video (click to play).

In the tape, such segments of three LEDs are connected in parallel. Therefore, it can be cut in specially marked places to any length. The cut is where the two segments meet.

Such a tape is connected to a household power supply with a voltage of 220V AC using a power supply, usually a pulsed one with an output voltage of 12V DC.

Now that you know what an LED strip is made of, let's move on to troubleshooting.

Fault # 1 - the entire tape does not burn

If, when turning on the power, it turned out that the tape does not glow at all, then you need to first of all make sure: is the power supply plugged into the outlet? Then check if there is voltage in the outlet, it is better to do this with a test lamp or a multimeter.

If you check with an indicator screwdriver, then the maximum that you can find out is the presence of a phase, and there may be no zero. Another option is to check with a two-wire voltage indicator.

If the outlet is working properly, we check if the wire through which 220V is supplied to the power supply unit is intact. To do this, measure the voltage or check its presence with a test lamp on the terminals of the power supply to which it is connected, usually these terminals are designated by the letters L (line) and N (neutral), or by the sign “

If there is voltage, then we check the 12V voltage at the output of the power supply, again with a multimeter or a 12V control lamp, for example, from the side lights of a car, as an option - with a piece of a known good LED strip.

If there is no voltage, then you need to replace or repair the power supply for the LED strip, the procedure for diagnosing and repairing it was described in the article earlier.

If there is voltage, you need to check the condition of the wire and whether there is voltage on the tape.If there is no voltage at the contacts where the wire is connected to the tape, then the wire is probably damaged, you need to either replace it, or find the damage and restore its integrity.

If the voltage comes to the tape, you need to check the quality of the contact between the wire and the contact pad of the tape. The wire can be soldered, then check the quality of the soldering, it is better to solder again, since with the visible integrity of the soldering, there may be no contact.

Or a terminal block can be used to connect the LED strip, then you need to check if there is contact between the spring-loaded plate and the contact pad, perhaps it has oxidized, then it needs to be cleaned of oxide and the structure should work.

If this does not help, the problem is in the ribbon, or rather in the flexible printed circuit board. Since the tape is not completely lit, it would be logical to conclude that the track in the first segment has burned out. To check this, you can apply power to the terminals of the second or third tape segments, and so on until it lights up. To do this, you can choose one of the options:

1. Apply power by bridging the positive contact pads with metal tweezers from those to which the power wire is connected to those that are at the junction of the first and subsequent segments. Most likely, one track burned out - plus or minus, it is unlikely that both could burn out at the same time.

2. Solder the jumper or the power wires themselves to the subsequent segments.

3. Supply power from a 12V battery, suitable from an uninterruptible power supply or auto-moto equipment.

If the tape has a protective silica coating to supply power to the contact pads, the coating must be cut or pierced with a needle.

Having localized the burnt-out area, it must be replaced by joining a new piece of tape with the remaining one.

The tracks might not have burned out, but they might have been torn. The LED strip, like cable products, has such a parameter as a minimum bend radius, due to the class of flexibility. Usually about 5cm. This is especially important if the tape is mounted in such a way that it wraps around a thin pipe.

Fault # 1.2 - the tape burns to the middle

This is a special case of the situation described above. The reason is the same - a track burned out in one of the segments. The methods for diagnosing and repairing the LED strip are the same - supply power to the sections of the strip located after the place that has failed.

Fault # 2 - all or part of the tape is flickering

The entire ribbon flickering can be caused by:

1. Problems with the power supply. You need to make sure that it is working properly either by connecting the tape to a known good voltage source, or to the battery. Or, on the contrary, you can connect a known-good tape or light bulb to the power supply.

2. If the power supply is normal, then you need to make sure the quality of the contact between its terminals and the 12V wires of the LED backlight power supply. Then check the connection of the supply wires and the tape itself.

3. If this turned out to be normal, then check the condition of the tape by applying power to the other contact pads, as described above. If you manage to find a problem area, you need to replace it.

4. It may be that the LEDs are out of service due to aging, overheating, or improper power supply. Then the entire tape needs to be replaced.

Fault # 3 - one or more pieces of LED strip are off or flickering

Individual segments may shine poorly, flicker, or even go out altogether. This could be due to a burned out or damaged resistor or one of the LEDs in the series connected circuit. For the same reason, an increased brightness of a separate area can be observed. Perhaps the elements are normal, but the problems, again, are with the flexible printed paths of the board.

It is best to cut out such a site immediately and replace it with a serviceable one.

220V tape - three main differences

With a tape designed for mains power, everything is the same except for a few factors:

1. The multiplicity of the tape cut is different - 50, 100 cm.

2. Since all Led-equipment operates on direct current, a full-wave rectifier of the mains voltage is used to power the network tape - a diode bridge, usually installed near the plug in a small box. It can also fail - any one designed for a voltage of more than 400 V is suitable for replacement.

3. The rectified voltage reaches 310 Volts, do not climb with your bare hands to the tape connected to the network.

Conclusion - three main issues: quality, installation and power supplies

Tapes or their fragments often burn out without modifying the declared resource. Although LEDs can shine for 30,000 thousand hours, this number is significantly reduced if the rules for working with them are not followed. Let's summarize:

1. In cheap tapes - cheap LEDs, they shine worse, get hotter and go out faster. By the way, LEDs are catastrophically afraid of exceeding the maximum permissible operating temperature, it is better that it does not go beyond 50-60 degrees.

2. Incorrect wiring leads to overheating of the LEDs and damage to the tracks. Too tight gluing of the tape leads to the fact that the whole structure heats up more. It is necessary to leave a small gap between the adjacent strips of tape, at least 1-3 of its width.

Also, do not forget that bending of the tape with a radius of less than 5 cm should not be allowed. Moreover, avoid fractures at right angles and sharper. It is better to cut the tape, glue it to the surfaces, and make a connection at their corner, either by soldering or by clamping.

3. Do not exceed the rated supply voltage. Better, on the contrary, lower it from 12 to 11.5 - 11.7V. This can be done by rotating the trimmer, usually located near the wire terminals. The increased voltage also entails an increased current, which will heat up the LEDs, the consequences are described above.

Recently, LED products have been in very high demand on the domestic market. At the same time, LED strips are in the highest demand. Despite the abundance of offers on the market, the problem associated with the fact that the LED strip has stopped burning turns out to be relevant for many users.

Partial burnout of the LED strip

Many consumers of LED products do not think about whether an LED strip with such a low market value could burn out. As a result, they become the owners of a product with a minimum copper content or generally on foil, with low-quality diodes and resistors and a falling off adhesive layer, which was made by hardworking inhabitants of the Middle Kingdom in some basement workshop.

Recommendation: it is better to buy LED strips with one solid diode inside, and not consisting of many small elements.

If you have made a choice in favor of cheap and deliberately low-quality LED products, you should not be surprised by the fact that after a short amount of time the LED strip has ceased to show signs of life. Moreover, you must be mentally prepared for the following unpleasant surprises:

variegated glow;
loss of glow brightness;
uneven glow from the beginning to the end of the tape;
poor quality of glue.

In this case, all claims against the seller will be useless. At best, he will complain about the Chinese quality, and at worst, he will simply refuse to talk.

However, the purchase of a rather expensive tape is not always a guarantee of long work. Damage can also happen to an expensive and potentially high-quality product. And the problem is often not in the use of cheap components or factory defects. Often, the problem turns out to be related to the fact that the tape chosen by the buyer does not correspond in its technical characteristics to the conditions in which it will be used.

If you do not want the LED lamp to burn out, you should follow a number of rules that will help to significantly increase the period of trouble-free operation of LED equipment:
In no case should you daisy-chain LED strips that are longer than five meters. In this case, only parallel connection of the segments is allowed. Otherwise, significant voltage drops and an increase in current on the tracks cannot be avoided. And this, in turn, will cause serious damage to the tape, up to and including its failure.
Do not operate LED strip equipment in conditions where the ambient temperature exceeds + 40 ° C.
Do not allow moisture to enter the open belts.
Under no circumstances should LED strips be immersed in water, even partially.

It is equally important and correct to mount the LED strip. Correct installation, coupled with correct operation, will significantly increase the life of LED strips.
Before proceeding with the installation of the equipment, it is strongly recommended to turn it on and check the indicated color. Unfortunately, practice shows that tapes from different batches can differ significantly in shade.
When connecting, pay particular attention to the polarity. This is especially important if you do not want the LED strip to stop burning after a couple of months.
If LED equipment is mounted on a metal or other conductive surface, it must be insulated. If this is not done, a short circuit will occur, which can lead to the most tragic consequences.
In no case should even the slightest damage to the tape path be allowed during installation. Cutting the tape is only allowed between the special areas for soldering. If you cut the equipment in other places, non-working segments will appear.

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LED strips often burn out because users plug them directly into household power supplies, which is completely unacceptable. The LED strip is designed to operate on DC 12 volts or 24 volts only.

Typically, the voltage is indicated along the entire length of the tape. A switching power supply is required to convert the voltage. This device is responsible for converting 220 V AC mains voltage. in direct current of the required value. The online calculator will help to calculate the current correctly.

Accordingly, when choosing a power supply, it is very important not only what kind of constant voltage it produces at the output, but also how much it can supply to the load. In order not to be mistaken with the choice, it is necessary to make careful calculations of the total current that the installed LED strips consume. And depending on the result obtained, choose a power supply.

In recent years, LED strips have been very often used to decorate both the interior and exterior of buildings. And every consumer who makes a choice in favor of this equipment is interested in that it will serve, without causing problems, as long as possible. It is quite possible, the main thing is to purchase products from only a reliable manufacturer and not to make mistakes during the installation and operation of the equipment.

LED strip is a convenient solution to many tasks where there is a need to illuminate an object or an entire room. The application is convenient, because installation does not require special skills and electrical engineering knowledge. The most common devices with a supply voltage of 12 volts - safe for humans. Various classes of IP-dust and moisture protection allow using the tape both at home and under water. But what if it suddenly stopped working, how to check the LED strip?First, you need to determine whether the entire LED structure is off, and then carry out diagnostics, draw conclusions about the amount of work and get down to work.Let's move from general to specific. If it all does not turn on, first you need to make sure whether the voltage comes to the 12-volt power supply. The tape connection diagram is shown below for clarity.There is no voltage - look for a fault in the outlet, wiring, network cable.Be careful when checking the mains voltage, 220 - danger to human life!Voltage present - breakdowns in low-voltage lines. To begin with, using a voltmeter, we determine the output voltage of the power supply. If 12 volts are not found, then you need to take it in for repair, if it is not repairable, replace it.Be careful, the repair of the power supply may be equal to the cost of a new one, this option is suitable for people who understand electronics and know how to fix it, I will not dwell in detail within this article, because this is a topic for a separate material.If the power supply is working properly, giving out its voltage, there is a problem with the tape or wiring leading to it. It is necessary to check the connection (soldering, connector) of the LED system, if the circuit is assembled with their help, the problem will most likely be here. There are individual situations when the live parts of the tape are damaged, but this rarely happens.The reasons for the failure of individual parts of the tape can be as follows:

power surges;

general, local overheating;

mechanical damage to the conductors.

Now let's go through each of them in more detail. The likelihood that a voltage surge will occur is already reduced by using the power supply. But it is possible that as a result of such an incident, your lighting system may completely stop working or its individual sections may fail.Overheating can occur if the tape has a high power density, more than 10 watts per meter. It should be borne in mind that too tight installation - turn to turn, strip to strip - will have a bad effect on operation. Local overheating of a small piece of it may occur if the installation was carried out near heating devices, as well as areas with high temperatures, for example, over a kitchen stove.Mechanical damage can occur during installation when the tape is subjected to excessive bending. The minimum bending radius of the LED strip is about 5 centimeters, if you wrap small-sized figures with the LED strip, there is no guarantee of long-term operation.Such faults can be easily repaired. To do this, you need to cut out the part that has ceased to burn, along the marked lines for the cut. Using special connectors, connect a similar piece of suitable length, if possible, it is better to use soldering.Difficulties in such repairs can manifest themselves in situations where the breakdown site is in the line of sight, in such a situation it is necessary to cut a piece of such a length so that it is possible to hide the connections.What if the light is dim? The tape or its parts do not always go out completely, the glow is observed, but it is weak. This malfunction can be caused by two reasons.

The first one - when a separate fragment faded - most likely the LEDs simply went out of order, degraded. We must not forget about local factors such as bending, overheating, other mechanical actions, for example, some kind of physical stress on this section of the chain.

The second - the tape has faded along its entire length. Replacing the structure completely is not always the optimal solution, perhaps the reason is in the power source or in the joints between the tape and the power supply, you need to check them before changing the entire installation.

When you buy tape or repair a lighting system with such a solution, it becomes necessary to check it.To do this, you must have at least a "crown" battery, with its help you can check small areas. But in this simplest version, there is a big drawback - you will not see the full brightness of the LEDs.To turn them on at full capacity, you need a 12-volt power supply. For small pieces, the compact A23 battery is perfect for use in some remote controls and radio doorbells.For long stretches, use large batteries. For example, from an uninterruptible power supply of a computer, they have 12 volts at their terminals, a car battery will perfectly cope with this task.And, of course, no one canceled the option using a known-good power supply.To test each LED separately, you need to use a multimeter, or a 3-volt battery. How to check an LED with a multimeter is described in this video.

LED lighting products have become part of our lives

It is known that LEDs cannot work directly from a 220 V network. To do this, they need additional equipment, which, most often, fails. We will talk about him today. Consider the circuit of an LED driver, without which the operation of the lighting device is impossible. Along the way, we will conduct an educational program for those who do not understand anything in electronics.

The 220V LED lamp driver circuit consists of:

diode bridge;
resistances;
resistors.

The diode bridge serves to rectify the current (converting it from alternating to direct current). On the graph, this looks like a cut-off of a half-wave of a sine wave. Resistances limit current, and capacitors store energy by increasing the frequency. Consider the principle of operation on the circuit of a 220 V LED lamp.

Having understood the principle of operation and the driver circuit, the decision on how to fix a 220V LED lamp will no longer seem difficult. If we talk about high-quality lighting devices, then you should not expect trouble from them. They work for the entire prescribed period and do not fade, although there are "diseases" to which they are also susceptible. Let's talk about how to deal with them.

To make it easier to understand the reasons, we summarize all the data in one common table.

Good to know! Repair of LED fixtures is impossible to carry out indefinitely. It is much easier to eliminate negative factors affecting durability and not to purchase cheap products. Savings today will cost you tomorrow.As economist Adam Smith said, "I'm not rich enough to buy cheap things."

Before you repair an LED lamp with your own hands, pay attention to some details that require less labor. Checking the cartridge and the voltage in it is the first thing to do.

Important! Repair of LED lamps requires a multimeter - without it, it will not be possible to ring the driver elements. A soldering station is also required.

A soldering station is required for the repair of LED chandeliers and lighting fixtures. After all, overheating of their elements leads to failure. The heating temperature during soldering should be no higher than 2600, while the soldering iron heats up more. But there is a way out. We use a piece of copper core with a cross section of 4 mm, which is wound around the tip of the soldering iron with a tight spiral. The more you lengthen the sting, the lower its temperature. Convenient if the multimeter has a thermometer function. In this case, it can be adjusted more precisely.

But before you repair LED spotlights, chandeliers or lamps, you need to determine the cause of the failure.

One of the problems that a novice home craftsman faces is how to disassemble an LED light bulb. To do this, you need an awl, solvent and a syringe with a needle. The diffuser of the LED lamp is glued to the body with a sealant that must be removed. Passing carefully along the edge of the diffuser with an awl, inject the solvent with a syringe. After 2 ÷ 3 minutes, lightly twisting, the diffuser is removed.

Checking the disassembled LED bulb. You shouldn't do this - it's dangerous.

Some lighting fixtures are made without gluing with a sealant. In this case, it is enough to turn the diffuser and remove it from the housing.

Having disassembled the lighting fixture, pay attention to the LED elements. Burned is often identified visually: there are burn marks or black dots on it. Then we change the faulty part and check the functionality. We will describe the replacement in detail in the step-by-step instructions.

If the LED elements are in order, go to the driver. To check the performance of its parts, you need to solder them from the printed circuit board. The value of the resistors (resistances) is indicated on the board, and the parameters of the capacitor are indicated on the case. When dialing with a multimeter in the appropriate modes, there should be no deviations. However, often failed capacitors are determined visually - they swell or burst. The solution is to replace it with a suitable one in terms of technical parameters.

The LED can be ringed with a multimeter without unsoldering from the printed circuit board

Replacing capacitors and resistances, unlike LEDs, is often performed with a conventional soldering iron. In this case, you should be careful not to overheat the nearest contacts and elements.

If you have a soldering station or a hair dryer, this job is simple. It is more difficult to work with a soldering iron, but it is also possible.

Good to know! If there are no working LED elements at hand, you can install a jumper instead of the burnt one. Such a lamp will not work for a long time, but it will be possible to win some time. However, such repairs are made only if the number of elements is more than six. Otherwise, the day is the maximum work of the repair product.

Modern lamps run on SMD LED elements that can be soldered out of an LED strip. But it is worth choosing those that are suitable for technical characteristics. If there are none, it is better to change everything.

Chinese driver - these guys love minimalism

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For the correct choice of LED devices, you need to know not only the general LED characteristics... Information about modern models, electrical circuits of working devices will come in handy. In this article, you will find answers to these and other practical questions.

If the driver consists of smaller SMD components, use a copper wire soldering iron on the tip. A visual inspection revealed a burnt element - we solder it and select the one that matches the marking. No visible damage is more difficult.We'll have to solder all the details and ring them separately. Having found the burnt one, we change it to a workable one and mount the elements in place. It is convenient to use tweezers for this.

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Useful advice! Do not remove all elements from the PCB at the same time. They are similar in appearance, you can later confuse the location. It is better to solder the elements one at a time and, after checking, mount them in place.

Repairing an LED tube in the form of a fluorescent lamp is no different from working with a simple

When installing lighting in rooms with high humidity (bathroom or kitchen), stabilizing power supplies are used, which lower the voltage to a safe one (12 or 24 volts). The stabilizer can fail for several reasons. The main ones are excessive load (power consumption of the luminaires) or the wrong choice of the degree of protection of the unit. Such devices are repaired in specialized services. At home, this is unrealistic without the availability of equipment and knowledge in the field of radio electronics. In this case, the power supply unit will have to be replaced.

The power supply for the LEDs looks like this

Very important! All work on replacing the stabilizing LED power supply is carried out with the voltage removed. Do not rely on the switch - it may be incorrectly wired. The voltage is disconnected in the distribution board of the apartment. Remember that touching live parts with your hand is life-threatening.

You need to pay attention to the technical characteristics of the device - the power must exceed the parameters of the lamps that are powered from it. Having disconnected the failed unit, we connect a new one according to the diagram. It can be found in the technical documentation of the device. This is not difficult - all wires are color-coded, and the contacts are letter designation.

Decoding of IP protection degrees for electrical appliances

Plays the role and degree of protection of the device (IP). For a bathroom, the device must be marked at least IP45.

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In order for the lighting to be stable, and the installed products to serve as long as possible, you should choose the right 12V power supply for LED strip... In this publication, we will consider the types of devices, how to calculate them correctly, how to do it yourself, how to connect, popular models.

If the reason for the flickering of the LED lamp is the failure of the capacitor (it needs to be replaced), then periodic blinking when the light is off is easier to solve. The reason for this "behavior" of the luminaire is the backlight-indicator on the switch key.

The capacitor located in the driver circuit accumulates voltage, and when the limit is reached, it gives out a discharge. The key backlight transmits a small amount of electricity, which does not in any way affect incandescent bulbs or "halogens", but this voltage is enough for the capacitor to start accumulating it. At a certain moment, it gives out a discharge to the LEDs, after which it switches back to accumulation. There are two ways to solve this problem:

We take out the key from the switch and turn off the backlight. The method is simple, but indications that add value to the switch are no longer useful.
We disassemble the chandelier and change the phase wire with zero places on each cartridge. The method is more complicated, but it retains the functionality of the switch. In the dark, you can see it well, and this is a plus.

Such a switch can cause the LEDs in the device to flash.

Not only LED lamps, but also CFLs are susceptible to flashing. The device of their PRU (starting-regulating device) works on a similar principle, which allows the capacitor to store energy.

Consider an example of a simple LED lamp repair:

LED strips, being very effective and practical lighting devices, have become more and more firmly in our lives.With their help, you can create illumination of incredible beauty, both at home and on the street. But in order for the operation of the LED strip to be possible, you need to connect a power supply unit (PSU) to it. But it is this component that is the weak link of the entire connection scheme, since due to the fact that the power supply unit converts the voltage of the 220 V network into 12 V, it often burns out.

LED strip power supply

In order not to spend money on buying a new device, you can fix it yourself. This article will tell you how the repair of this device is carried out.

LED strips are characterized by a low voltage (24 or 12V). In this regard, a power supply is required for their operation. When creating your own backlight using LED strips, you need to remember that you need to choose the right power supply.

Note! The most important parameter for choosing a power supply for LED strips is their power. To calculate the power of the power supply, you need to know the density of the arrangement of diodes on one meter of tape, as well as the total length of the backlight.

The service life of the converter will depend on how correctly the power supply was calculated for a particular LED strip.
To reduce the risk of premature failure of a power supply suitable for an LED strip, you need to choose it according to the appropriate parameters:

Note! The most popular are tapes designed for 12 V.

12V LED strip

cooling method. It can be active (the unit is equipped with a fan) and passive (the unit has a grill at the top of the case). Converters with an active cooling system are considered more profitable;
the material from which the body is made. For a power supply unit, the case can be made of aluminum, metal or plastic. Models made of aluminum or metal are considered to be of higher quality.

In addition, you need to remember that cheap Chinese converters will not work for long. Their repair may already be needed after just a couple of months of work. But the products of well-known manufacturers will serve all the life allotted for it.

Since LED strips for 12 V and 24 V are connected to the 220 V network through the power supply, they very often burn out due to rapid wear. Indeed, a large voltage passes through the converter, and low-quality radio components often burn out from a high load.

LED lighting in the house

In addition, improper operation of lighting products can lead to premature damage to the power supply for LED strips.

Note! In 70% of cases, the reason for the breakdown and the need to repair the converter is the fault of people who violate the operating conditions of both the tape and the power supply.

The following points can lead to damage to this type of converter:

moisture on the case of the device;
accumulation of dust and dirt inside the power supply;
incorrect calculation of the total power of the tape;
wrong selection of power supply unit. For example, a margin of 20-30% of the total backlight power was not taken.

In addition, poor-quality components of the electrical circuit can lead to damage to the power supply unit. This situation is often typical for converters made in China, which are actively sold today on any radio market.
Do-it-yourself repair depends on what was the cause of the breakdown. Therefore, before proceeding with it, it is necessary to conduct a visual inspection of the burned-out power supply unit.

To find out the reason why the power supply for LED strips is not working, you need to open its case. By opening the transducer, you can visually assess its performance. The fact that it has clearly burned out will be evidenced by the following points:

a burnt smell, which intensifies when the case is opened;
the presence of burnt and blackened parts;

Burnt out part in the power supply

some parts may swell.Capacitors very often swell;
there was a breakage of contacts and tracks between the elements of the electrical circuit.

Note! If, after opening the case, a hole is found in a burned-out board, and some parts are generally torn, then repairing such a converter with your own hands will be unprofitable. It's easier to buy a new power supply and connect it to the backlight.

At the same time, if only a couple of burnt parts were found, then self-repair will save you enough money. After all, individual parts are much cheaper than a full-fledged device.

When the cause of the breakdown has been found, then repairs can begin. To do this with your own hands, you need a converter circuit. In PSUs designed to connect LED strips, a typical circuit is often used.

In such devices, the following components most often fail:

TL494 or PWM controller IC. Its analogues are M1114EU, IR3M02, MV3759, KA7500, etc .;
key transistors T10 and T11;
capacitors C22 and C23, as well as C30-C33;
dual diode D33.

All other elements of this scheme burn out very rarely. But when troubleshooting, they also need to be checked. After all, if you turn on the power supply with at least one defective part, it will burn out again. In this case, previously capable components of the electrical circuit can also burn out.

To identify problems in the power supply that are not visually detected, it is necessary to do the following manipulations:

we open the block;
we inspect to protect ourselves and apply voltage to capacitors C22 and C23. Normally, it will be in the region of 310 V. This voltage indicates that the rectifier and the mains filter are in good working order;

then, at rated load, we check the capacitors. Their voltage should be about 150 volts;
after that we check the TL494 microcircuit (analogue of the KA7500).

To check the TL494 with our own hands, do the following:

turn off the voltage at 220 V;
on the power supply unit, we apply a voltage of 12-15 V to pin 12 (+) and 12 V to pin 7 (-). Further, all voltages will be given relative to pin 7;

Note! A voltmeter should be used to check the voltage.

after that we check the voltage at output 14. Normally, it should show about + 5V (-5%) and be stable when the voltage value changes from + 9V to + 15V at pin 12. If this condition is not met, then the internal stabilizer has burned out and the microcircuit must be replaced;
using an oscilloscope, the sawtooth voltage is checked, which should be at pin 5. If it is distorted or absent altogether, then timing elements C35 and R39 or the built-in generator are damaged. Again, such a microcircuit needs to be replaced;
then we check for the presence of rectangular pulses at the terminals 8 and 11. They appear only in a situation where the power supply is turned on or off. If they are present, then the microcircuit is considered to be in good order;
to see the increase in pulse width at pins 8 and 11, you need to connect pin 7 to the 4th lead. If pin 4 is connected to the 14th, then the pulses should disappear. If this does not happen, then the microcircuit needs to be changed;
if you lower the voltage of the external source to 5V, then the pulses should disappear. When the voltage rises + 9V ... + 15V - they should appear. If this does not happen, then the voltage relay can be considered faulty. This again leads to the replacement of the microcircuit.

Thus, you can check the performance of this microcircuit with your own hands.

If, when the power supply is turned on, it is intended for LED strips, it starts to "chirr", then this is an obvious problem in the PWM modulator. In such a situation, it does not start at all.
If a blown fuse was found during the check, then do not rush to replace it. Instead, you can connect a simple incandescent light bulb of about 60-100 watts. After that, a voltage of 220 V should be applied to the unit. Thus, you can check the serviceability of the mains filter and rectification.If the bulb flashes and immediately goes out, then they are in good working order. In this case, the key transistors are not punctured.

After the punched elements have been identified, the do-it-yourself repair can be considered almost complete. It remains only to solder out all the faulty elements and solder new and workable parts in their place.

Test-ready power supply

After that, we close the converter housing and check it for operability. After you are convinced of its serviceability, you can connect LED backlighting to it.

In order to repair a power supply unit for LED strips, you need to open its case and check all the elements of the electrical circuit for serviceability. Replacing several parts will cost several times less than buying a new converter. The main thing is to correctly identify all device malfunctions and eliminate them at the same time.

Video (click to play).