DIY smd LED lamp repair

In detail: do-it-yourself smd LED lamp repair from a real master for the site my.housecope.com.

Can purchased LED bulbs be repaired? This question, taking into account the high cost of lamps, is quite relevant; a lot has already been written about this on Internet forums. Most often, the issues of repairing lamps bought on Aliexpress are discussed.

In the article "Shopping on Aliexpress - personal experience of shopping in a Chinese online store", among other things, it was told about the purchase of LED lamps, which are so popular recently. Actually, the article began with these lamps: the quality of these lamps left much to be desired, mainly attracted by the low price. But in some places where too much illumination is not required, these lamps came in handy.

With further use, it turned out that these lamps are not as durable as advertised. If the lamps of the Navigator trademark have been working trouble-free for the author of the article for almost two years, then the lamps bought at Aliexpress will fail in a month - another, or even earlier. An indicative case is when the lamp, replaced in the evening, simply did not turn on the next day. As a result, two faulty identical lamps.

Someone else would have just thrown away the unusable lamp, but not the radio amateur. Therefore, radio amateurs first try to find out the scale of the disaster, and, if possible, eliminate the defect. So it was this time. It's not that Chinese lamps are too expensive, but if they can be restored, then you won't have to buy another lamp. As they say, the savings are obvious.

The appearance of these lamps is shown in the figure.

This picture is taken from the Aliexpress website. Apparently, the sellers assumed that someone would disassemble and repair such lamps, moreover, repairs, as they say, are not far off. A larger board is shown in the figure below. It is easy to understand from the inscription on the board that the lamp is assembled from 34 LEDs of standard size SMD2835 (2.8 * 3.5 mm).

Video (click to play).

Disassembling the lamp revealed that there is a small power supply board inside. In the photo, only capacitors are visible, all other parts are made by SMD installation and are located on the back side of the board.

The circuit assembled on the board is shown in the figure below. It’s impossible to come up with an easier one: a conventional transformerless power supply with a quenching capacitor.

The purpose of the parts is clear: resistors R1, R3 discharge capacitors after disconnecting from the network. This is done in order not to pinch the current when you touch these capacitors with your hands. With regard to capacitor C1, everything is clear. If you unscrew the lamp from the socket, the touching of the base may not be very pleasant. It all depends on what charge remains on the capacitor C1.

The charge on the electrolytic capacitor can remain only if at least one LED is cut off. This charge can be "felt" only by disassembling the lamp. Although the resistor R3 has one more purpose.

In the event of a burnout of the LED chain (at least one LED), the voltage across the electrolytic capacitor remains at a level not exceeding the operating voltage of the electrolytic capacitor.

In the diagram, the operating voltage of the electrolyte is 250V. If we assume that the voltage drop across one LED is 3V, then 34 * 3 = 102V will drop on 34 LEDs. It turns out something like a parametric voltage regulator. Therefore, in theory, 250V is more than enough.

Apparently, the Chinese developers reasoned in a similar way: there are lamps in which the operating voltage of an electrolytic capacitor is only 100V.Basically, these are small-sized lamps with a power of 3 ... 5W, where it is difficult to hide a high-voltage capacitor. In the lamp shown in the photo, the operating voltage of the electrolytic capacitor is 400V. But the resistor R3, most likely, will not be superfluous.

Resistor R2 is designed to limit the current through the LEDs. But this is only in the diagram. In fact, there is simply none on the printed circuit board inside the lamp. The function of limiting the current through the LED chain is successfully performed by the capacitor C1. This is a variant of the scheme. Maybe other manufacturers still install this resistor.

So, as it was written a little above, two faulty lamps turned out to be available at once, each only had one LED burned out. Moreover, there were no visible defects in the form of soot on the board, destruction or blackening of the LED itself. Therefore, the faulty LED had to be found. It is quite simple to do this: when dialing with a digital multimeter, the LEDs light up weakly. Naturally, if the probes of the multimeter are connected in the forward direction.

It was decided to use one lamp for spare parts, remove the LED from it and re-solder it to another. Attempts to unsolder the LED using a hot air gun were unsuccessful: the LED did not want to be unsoldered.

The fact is that on the reverse side of the printed circuit board there is an aluminum heatsink, because LEDs, like all semiconductor devices, do not like high temperatures very much. But even without a heatsink, the process of soldering parts from a printed circuit board is much more complicated and dramatic than soldering new parts onto a board.

Repair should be started by finding a faulty LED if the lamp went out completely and immediately. If the lamp starts blinking, or just shines faintly, then the malfunction lies in the power supply. Most often this happens due to a malfunction of the capacitor C1.

The easiest repair option is to replace capacitor C1 with a known good one. A faulty electrolytic capacitor can almost always be identified by eye by a swollen bottom. This is how modern explosion-proof electrolytes behave.

After detecting a faulty LED, it is easiest to unsolder it as follows. The first thing to do is to remove the yellow elastic filter with a thin screwdriver or needle. There will be a metal surface with a crystal under it. Put a piece of solder and a small amount of gelatinous flux on this surface. With a well-heated soldering iron with a power of at least 60 ... 80W, warm up this "sandwich" until the LED is unsoldered from the board.

Somewhat better results can be achieved by using a low-melting alloy such as Wood's alloy instead of solder. Such an alloy in the form of small cakes is sold on radio markets. When mixed with a base solder, usually lead-free, Wood's alloy lowers the melting point of the lead-free solder. Therefore, the desoldering process becomes easier and faster, the likelihood of overheating the printed circuit board is significantly reduced.

Another way to unsolder a faulty LED is with hot tweezers. But not everyone has this tool, and it is hardly worth buying it for a one-time use. Therefore, it is better to make a U-shaped sting, or use the homemade sting shown in the figure below.

After the faulty LED is sealed off, it remains to replace it with a new one. LEDs of standard sizes 2835 or 5730 can be ordered in the same place where the lamps were purchased on Aliexpress. They are quite inexpensive there, about 50 rubles per hundred pieces.

Judging by the price, these are not the best LEDs, but the lamps were still repaired, and the glow of these LEDs is no worse than those that were originally.

Soldering a new LED to the board is not difficult. This can be done with a regular soldering iron. Remains of old lead-free solder should be removed from the board.This is best done with a wire braid with shielded wire.

The braid must be impregnated with flux, in the simplest case, with rosin. Then, with a well-heated soldering iron, pass through the braid along the contact pads, the solder is absorbed into the braid. Then irradiate the contacts of the board with POS 61 solder or the like.

Now it remains only to solder the LED installed on the contact pads. It is imperative to cover the LED contacts with a layer of flux, better than a gel-like one. After that, it is enough to touch the ends of the LED with a soldering iron to melt the solder remaining on the contacts of the board. Soldering is so fast that the finger holding the LED on the board does not feel any temperature rise.

With a variety of lighting devices on the counters of the country, LEDs remain out of competition due to their efficiency and durability. However, a high-quality product is not always purchased, because in a store you cannot disassemble the goods for inspection. And in this case, it is not a fact that everyone will determine from what parts it is assembled. Lamps burn out, and it becomes expensive to buy new ones. The solution is to repair LED lamps with your own hands. This work is within the power of even a novice home craftsman, and the details are inexpensive. Today we will figure out how to check the lighting device, in what cases the product is repaired and how to do it.

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.

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 the 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 and regulating device) works on a similar principle, which allows the capacitor to store energy.

Read also: DIY airbrush repair

It is these light sources that are preferred today by residents of many countries of the world, however, mass production also generates great demand. Not all manufacturers are conscientious about technologies and recommendations, which leads to rapid burnout of products. Constantly buying new devices is more expensive. In such situations, DIY repair of LED lamps is required.

Do not be intimidated and immediately close the article - after reading the information below, you will understand that even an unskilled person without work experience can handle such work. An assembled LED lamp or lamp is an expensive product, but it will not be difficult to buy a burned-out part separately.

When starting to repair something, first you should carefully study the device and the principle of operation of the equipment. Regardless of the appearance and the LEDs used, each lamp, including the filament, is designed according to the same electrical circuit. Remove the case of the product and inside you will see a driver - an electronic board to which various radio components are attached.

Any LED lamp functions according to the same principle. The supply voltage is supplied to the contacts of the electric socket and is transmitted to the output of the conventional lamp base (E27 or other format). There can be several such conclusions. Two wires are soldered to them, through which the voltage goes to the input of the electronic board. The driver converts the AC voltage to DC, usually lowering it, and then transfers it to another electronic board with LEDs.

A driver is an electronic unit that generates and converts current with voltage into those values that are sufficient for the operation of LEDs. In more expensive products, the board is hidden under diffusing glass for protection.

The most simple circuit for a LED lamp connected to a 220 V network includes a driver consisting of two damping resistors that stabilize the voltage. The LED diodes are connected in different directions, which guarantees perfect protection against reverse voltage. In this case, the flicker frequency increases from 50 to 100 Hz.

For example, to connect the LED strip to the base, two wires are soldered. The ends of these wires are subsequently connected to the ends of the LED strip. The electric circuit of the positive wire includes a capacitor with a parallel connected resistor and passes through the positive part of the diode bridge, and the negative wire circuit - a resistor and is connected to the negative part of the diode bridge. A second "capacitor-resistor" unit is installed between the diode bridge and the LED strip, connected to both wires.

Simply put, the supply voltage passes through a limiting capacitor and enters the diode bridge, and from there to the LED elements. By replacing the LED with a rectifier diode, you will not double, but will lower the voltage - from 50 to 25 Hz.In this situation, the flickering of the product will become sensitive, harmful to the visual organs, leading to rapid fatigue and migraines.

Not all products are easy and simple to disassemble without damaging the component parts. Try to rotate the top of the case. If all else fails, you will have to use a solvent. Draw some solvent into a syringe and squeeze out along the seam through a needle. Wait about 5 to 10 minutes, then repeat the operation.

Repeat the steps at least three times, then start twisting the upper body in different directions to swing it. When the bulb is removed, clean the inner walls by removing the sealant and degreasing the surfaces. If the device will be used in a room with a low level of humidity, no sealant will be applied.

The service life of any product, including LED lamps, depends on the conditions of use, compliance with the rules and recommendations prescribed by the manufacturers.

There are many reasons due to which the service life specified by the manufacturer does not correspond to reality: the use of low-quality crystals and an incorrect assessment of the performance, since the conditions of real operation almost always differ from the potential ones.

Let's list the main reasons for the failure of LED products:

To extend the life of LED lamps and improve the quality of the glow, try to eliminate or reduce to a minimum the influence of the above factors. Entrust the installation of electrical wiring to the masters, create the most comfortable and acceptable conditions for using the products.

A good device will have straight edges. It is not always possible to assess the quality of the crystals used, so try to buy lamps in trusted stores from brand manufacturers.

Another option to extend the life of an LED light bulb is to use a dimmer that regulates the luminous flux. It is important to buy dimmable devices in advance or upgrade existing ones yourself. A dimmer will allow you to lower the starting current: the lower the value, the better.

The LED lamp can be repaired regardless of the cause of failure. To do this, you need to disassemble the product into parts and get to the filling. To begin with, a diffuser is removed, which performs several functions. The component is either secured to the base through a sealant or held in place with a snap. If the element will rotate separately from the body, it is enough to press in the right place to remove it.

Above, it was described what to do if the diffuser is securely glued to the body. Add to the use of a solvent the ability to remove the case with a thin screwdriver: gently pry it off without applying great force.

LED lamps with glass bulbs are unrepairable, since it is almost impossible to remove such a diffuser without damage.

In rooms with a high level of humidity, low voltage lighting devices are used - 12 or 24 V, which are connected to a general electrical network of 220 V. To reduce the high voltage of alternating current to the required constant values, stabilizing power supplies are used, which may fail.

The reason for the breakdown of the power supply may be an increased load (if the total power of the used lamps exceeds the allowable for the stabilizer) or an incorrectly selected degree of protection against the ingress of dust and moisture (IP). To fix these products, you should contact specialized service centers, since it is unrealistic to restore them in a domestic environment (certain equipment and knowledge of radio electronics are required). The only option is to change the power supply.

When replacing the stabilizer, the LED lamp must be completely disconnected from the power supply - wires are cut or terminals are disconnected.Don't rely solely on the switch. Be sure to disconnect the voltage through the distribution board of the apartment.

The power for the stabilizing power supply must be higher than the total value of the connected lamps. After disconnecting the failed element, connect a new one in accordance with the switching diagram. You can find it in the technical documentation for the equipment. The process is as simple as possible, since the wires are color-coded and the contacts are letter-coded.

The degree of protection against dust and moisture for the bathroom must be at least IP45.

To make the procedure as easy as possible, use a soldering station / hairdryer. The soldering iron is more difficult to operate, but it is possible.

Most devices consist of several LEDs connected in series. If even one fails, the whole group or the entire light source stops working. In this case, if there is no suitable LED at hand, the burned-out one can be replaced with a regular jumper. Remember that because of the jumper, the lamp will not work for long, but this way you can buy a little time to buy the desired element. The fewer the total number of LEDs, the faster the jumper lamp will fail.

Modern lighting fixtures use SMD diodes, which can be soldered from tape. When replacing, be sure to buy a part with identical specifications.

If the driver fails, study its design. An electronic board can consist of several SMD diodes, the size of which is much smaller than that of a soldering iron tip. In this case, you need to choose a soldering iron with copper wire on the tip. Solder the burned-out element and select the appropriate one according to characteristics or marking.

When no visible faults are found, the task becomes more difficult. We'll have to solder each part separately and ring it. As soon as a burnt component is found, replace it with a new one and return all the elements to their places. Use tweezers to simplify the work.

Never remove all parts from the board at once. You may not remember their correct location and later confuse them. Proceed as follows: evaporate one diode, check its performance, and then put it back in place. Repeat the same for the rest of the elements.

"Kukuruza" is one of the types of LED lamps, named because of its shape and arrangement of semiconductors.

Serving such products is as easy as shelling pears! The LEDs are located on top and are not protected by anything, therefore, when replacing them, it is not necessary to disassemble the device and climb into its filling.

Call each element separately and replace the failed ones. The defective component can be replaced with a conventional jumper. The presence of such slightly reduces the life of the "corn", but does not affect the stability and reliability of the device. This is only relevant for lamps of this type!

In parallel with lamp repair, you can experiment a little with LEDs. This is done due to the fact that the same LEDs (in type and brightness) with different color temperatures (warm yellow and cold white glow) differ in price by 3-4 times. Despite this, commercially available warm glow LEDs, which are considered the most expensive compared to a conventional incandescent lamp, have a bluish tint.

Cheaper factory lamps come without a rectifier or smoothing capacitor. You can install it yourself at home using a regular soldering iron. There are usually no elements in Chinese products, the manufacturers of which simply connect pairs of LEDs connected in different directions and add a ballast capacitor. The flickering of the lamp increases 2 - 3 times, which negatively affects human health.

The main reason LED bulbs flicker is when a weak capacitor is used or not. The problem is solved quite simply - by installing a more powerful component.If the voltage of the capacitor is 102 V, and the LEDs - 180 V, the value of the first should be increased by 1.5 - 2 times.

Install a similar capacitor, but with a larger capacity. Simply re-solder the old capacitor by replacing it with a new one. Another output is to connect a second capacitor in parallel to increase the total capacitance and power.

Despite the gradual decline in the cost of LED lamps, their price is still high. Not everyone can afford to buy consistently high-quality products, but cheap products will not last long.

Video (click to play).

In case of breakdowns, do not rush to the store. Perhaps the problem is not as bad as it seems, and you will get by with a banal replacement of the power supply unit or a burnt-out LED. Do not forget about observing the rules and operating conditions of the lamps, which will ensure their durability.