Converting a floor lamp reading lamp to LED. Repair of LED lamps with examples. Why is it permissible to close the terminals of burned-out LEDs in LED lamps
In this case, the finished LED strip. The basis was taken from a Chinese lamp with a fluorescent lamp, or rather its frame.
Here is such a relatively uncomplicated alteration of the lamp to an economical and , the main task is completed, heating is excluded, the service time is increased, and energy consumption is reduced.Thus, not only low-power, but also standard ceiling-mounted LDSs can be upgraded, naturally with a more powerful PSU.
Approximate calculation : look at the power of the tape per meter and the power of the ballast. It is necessary that these two values approximately coincide. That is, a ballast of 11-13 W on transistors 13001 freely feeds 2 meters of tape (9.6 W) without heating. But just in case, it is better to make a power supply with a margin.
Due to low power consumption, theoretical durability and lower prices, incandescent and energy-saving lamps are rapidly replacing. But, despite the declared service life of up to 25 years, they often burn out without even having served the warranty period.
Unlike incandescent lamps, 90% of burned-out LED lamps can be successfully repaired with your own hands, even without special training. The presented examples will help you to repair failed LED lamps.
Before undertaking repairs led lamp you need to present its device. Regardless of the appearance and type of LEDs used, all LED lamps, including filament bulbs, are arranged in the same way. If you remove the walls of the lamp housing, then inside you can see the driver, which is a printed circuit board with radio elements installed on it.
Any LED lamp is arranged and works as follows. The supply voltage from the contacts of the electric cartridge is supplied to the terminals of the base. Two wires are soldered to it, through which voltage is applied to the input of the driver. With driver supply voltage direct current is fed to the board on which the LEDs are soldered.
The driver is an electronic unit - a current generator that converts the mains voltage into the current required to light the LEDs.
Sometimes, to scatter light or protect against human contact with unprotected conductors of a board with LEDs, it is covered with a diffusing protective glass.
About filament lamps
In appearance, a filament lamp is similar to an incandescent lamp. The device of filament lamps differs from LED lamps in that they do not use a board with LEDs as light emitters, but a glass sealed bulb filled with gas, in which one or more filament rods are placed. The driver is located in the base.
The filament rod is a glass or sapphire tube with a diameter of about 2 mm and a length of about 30 mm, on which 28 miniature LEDs coated in series with a phosphor are fixed and connected. One filament consumes about 1 W of power. My operating experience shows that filament lamps are much more reliable than those made on the basis of SMD LEDs. I think over time they will replace all other artificial light sources.
Examples of repair of LED lamps
Attention, the electrical circuits of the LED lamp drivers are galvanically connected to the phase of the electrical network and therefore extreme care must be taken. Touching an unprotected part of the human body to bare parts of a circuit connected to an electrical network can cause serious damage to health, up to cardiac arrest.
LED Lamp Repair
ASD LED-A60, 11 W on SM2082 chip
Currently, powerful LED bulbs have appeared, the drivers of which are assembled on microcircuits of the SM2082 type. One of them worked less than a year and got me to repair. The light bulb flickered randomly and came on again. When tapped on it, it responded with light or extinction. It became obvious that the problem was a bad connection.
To get to the electronic part of the lamp, you need to use a knife to pick up the diffusing glass at the point of contact with the body. Sometimes it is difficult to separate the glass, since silicone is applied to the retaining ring when it is seated.
After removing the light-scattering glass, access to the LEDs and the microcircuit - the current generator SM2082 was opened. In this lamp, one part of the driver was mounted on an aluminum printed circuit board of LEDs, and the second on a separate one.
External inspection did not reveal defective rations or broken tracks. I had to remove the board with LEDs. To do this, the silicone was first cut off and the board was pushed over the edge with a screwdriver blade.
To get to the driver located in the lamp housing, I had to unsolder it, heating two contacts at the same time with a soldering iron and moving it to the right.
On one side of the driver PCB, only an electrolytic capacitor with a capacity of 6.8 microfarads for a voltage of 400 V was installed.
On the reverse side of the driver board, a diode bridge and two series-connected resistors with a nominal value of 510 kOhm were installed.
In order to figure out which of the boards was losing contact, they had to be connected, observing the polarity, using two wires. After tapping the boards with a screwdriver handle, it became obvious that the fault lies in the board with the capacitor or in the contacts of the wires coming from the LED lamp base.
Since soldering did not arouse suspicion, I first checked the reliability of the contact in the central terminal of the base. It is easily removed by prying it over the edge with a knife blade. But the contact was reliable. Just in case, I tinned the wire with solder.
It is difficult to remove the screw part of the base, so I decided to solder the solder wires suitable from the base with a soldering iron. When touching one of the rations, the wire was exposed. Found "cold" soldering. Since there was no way to get to strip the wire, I had to lubricate it with the FIM active flux, and then solder it again.
After assembly, the LED lamp emitted light steadily, despite being hit with a screwdriver handle. Checking the luminous flux for pulsations showed that they are significant at a frequency of 100 Hz. Such a LED lamp can only be installed in luminaires for general lighting.
Driver circuit diagram
LED lamp ASD LED-A60 on the chip SM2082
The electrical circuit of the ASD LED-A60 lamp, thanks to the use of a specialized SM2082 microcircuit in the driver to stabilize the current, turned out to be quite simple.
The driver circuit works as follows. The AC supply voltage is fed through fuse F to the rectifier diode bridge assembled on the MB6S microassembly. The electrolytic capacitor C1 smooths out the ripple, and R1 serves to discharge it when the power is turned off.
From the positive terminal of the capacitor, the supply voltage is applied directly to the LEDs connected in series. From the output of the last LED, the voltage is applied to the input (pin 1) of the SM2082 microcircuit, the current in the microcircuit stabilizes and then from its output (pin 2) it goes to the negative terminal of the capacitor C1.
Resistor R2 sets the amount of current flowing through the LEDs HL. The amount of current is inversely proportional to its nominal value. If the value of the resistor is reduced, then the current will increase, if the value is increased, then the current will decrease. The SM2082 chip allows you to adjust the current value from 5 to 60 mA with a resistor.
LED Lamp Repair
ASD LED-A60, 11W, 220V, E27
Another LED lamp ASD LED-A60, similar in appearance and with the same technical specifications, as above repaired.
When turned on, the lamp lit up for a moment and then did not shine. This behavior of LED lamps is usually associated with a driver malfunction. Therefore, I immediately began to disassemble the lamp.
The diffusing glass was removed with great difficulty, since it was heavily lubricated with silicone along the entire line of contact with the case, despite the presence of a retainer. To separate the glass, I had to look for a pliable place along the entire line of contact with the body with a knife, but still there was a crack in the body.
To gain access to the lamp driver, the next step was to remove the LED printed circuit board, which was pressed into the aluminum insert along the contour. Despite the fact that the board was aluminum, and it was possible to remove it without fear of cracking, all attempts were unsuccessful. The pay was held tight.
It also failed to remove the board together with the aluminum insert, since it fit snugly against the case and was planted on silicone by the outer surface.
I decided to try to remove the driver board from the side of the base. To do this, first, a knife was pulled out of the base, and the central contact was removed. To remove the threaded part of the base, it was necessary to slightly bend its upper shoulder so that the punching points disengaged from the base.
The driver became accessible and freely extended to a certain position, but it was not possible to completely remove it, although the conductors from the LED board were soldered.
There was a hole in the center of the board with the LEDs. I decided to try to remove the driver board by hitting its end through a metal rod threaded through this hole. The board advanced a few centimeters and rested against something. After further blows, the lamp body cracked along the ring and the board with the base of the base separated.
As it turned out, the board had an extension, which rested against the lamp body with its hangers. It looks like the board was shaped in such a way to restrict movement, although it was enough to fix it with a drop of silicone. Then the driver would be removed from either side of the lamp.
The voltage of 220 V from the lamp base through the resistor - fuse FU is fed to the MB6F rectifier bridge and after it is smoothed by an electrolytic capacitor. Next, the voltage is supplied to the SIC9553 chip, which stabilizes the current. Resistors R20 and R80 connected in parallel between terminals 1 and 8 MS set the amount of current to supply the LEDs.
The photo shows a typical electric circuit diagram, given by the manufacturer of the SIC9553 chip in the Chinese datasheet.
This photo shows appearance driver of the LED lamp from the side of the installation of output elements. Since space allowed, to reduce the ripple coefficient of the light flux, the capacitor at the output of the driver was soldered to 6.8 microfarads instead of 4.7 microfarads.
If you have to remove the drivers from the body of this lamp model and you cannot remove the LED board, then you can use a jigsaw to cut the lamp body in a circle just above the screw part of the base.
In the end, all my efforts to extract the driver turned out to be useful only for knowing the device of the LED lamp. The driver was correct.
The flash of the LEDs at the moment of switching on was caused by a breakdown in the crystal of one of them as a result of a voltage surge when the driver was started, which misled me. We had to ring the LEDs first.
An attempt to test the LEDs with a multimeter did not lead to success. The LEDs didn't light up. It turned out that two series-connected light-emitting crystals are installed in one case, and in order for the LED to start flowing current, it is necessary to apply a voltage of 8 V to it.
A multimeter or tester, switched on in the resistance measurement mode, outputs a voltage in the range of 3-4 V. I had to check the LEDs using a power supply, supplying 12 V to each LED through a 1 kΩ current-limiting resistor.
There was no replacement LED available, so the pads were closed with a drop of solder instead. It is safe for the driver to work, and the power of the LED lamp will decrease by only 0.7 W, which is almost imperceptible.
After the repair of the electrical part of the LED lamp, the cracked housing was glued together with Moment's quick-drying super glue, the seams were smoothed by melting the plastic with a soldering iron and leveled with sandpaper.
For interest, I performed some measurements and calculations. The current flowing through the LEDs was 58 mA, the voltage was 8 V. Therefore, the power supplied to one LED is 0.46 W. With 16 LEDs, it turns out 7.36 watts, instead of the declared 11 watts. Perhaps the manufacturer indicates the total power consumption of the lamp, taking into account losses in the driver.
The service life of the LED lamp ASD LED-A60, 11 W, 220 V, E27, declared by the manufacturer, is very doubtful to me. In a small volume of the plastic lamp housing, with low thermal conductivity, significant power is released - 11 watts. As a result, the LEDs and the driver operate at the maximum allowable temperature, which leads to accelerated degradation of their crystals and, as a result, to sharp decline their time between failures.
LED Lamp Repair
LED smd B35 827 ERA, 7 W on BP2831A chip
A friend shared with me that he bought five light bulbs as in the photo below, and all of them stopped working after a month. He managed to throw away three of them, and, at my request, he brought two for repair.
The light bulb worked, but instead of a bright light, it emitted a flickering weak light at a frequency of several times per second. I immediately assumed that the electrolytic capacitor was swollen, usually if it fails, the lamp begins to emit light, like a stroboscope.
The light-scattering glass was removed easily, it was not glued. It was fixed by a slot on its rim and a protrusion in the lamp body.
The driver was fixed with two solders to a printed circuit board with LEDs, as in one of the lamps described above.
A typical driver circuit on a BP2831A chip taken from the datasheet is shown in the photo. The driver board was removed and all simple radio elements were checked, everything turned out to be in good order. I had to check the LEDs.
The LEDs in the lamp were installed of an unknown type with two crystals in the case and the inspection did not reveal any defects. Using the method of serially connecting the leads of each of the LEDs to each other, he quickly identified the faulty one and replaced it with a drop of solder, as in the photo.
The lamp worked for a week and again got into repair. Shorted the next LED. A week later, I had to short-circuit another LED, and after the fourth I threw out the bulb, because I was tired of repairing it.
The reason for the failure of light bulbs of this design is obvious. LEDs overheat due to insufficient heat sink surface, and their life is reduced to hundreds of hours.
Why is it permissible to close the terminals of burned-out LEDs in LED lamps
The LED lamp driver, unlike the constant voltage power supply, outputs a stabilized current value, not voltage. Therefore, regardless of the load resistance within the given limits, the current will always be constant and, therefore, the voltage drop across each of the LEDs will remain the same.
Therefore, with a decrease in the number of series-connected LEDs in the circuit, the voltage at the output of the driver will also decrease proportionally.
For example, if 50 LEDs are connected in series to the driver, and a voltage of 3 V drops across each of them, then the voltage at the output of the driver was 150 V, and if 5 of them were shorted, the voltage would drop to 135 V, and the current would not change.
But the coefficient of performance (COP) of a driver assembled according to such a scheme will be low and power losses will be more than 50%. For example, for an MR-16-2835-F27 LED bulb, you will need a 6.1 kΩ resistor with a power of 4 watts. It turns out that the driver on the resistor will consume power that exceeds the power consumption of the LEDs and it will be unacceptable to place it in a small LED lamp housing, due to the release of more heat.
But if there is no other way to repair the LED lamp and it is very necessary, then the driver on the resistor can be placed in a separate case, all the same, the power consumption of such an LED lamp will be four times less than incandescent lamps. At the same time, it should be noted that the more LEDs connected in series in the light bulb, the higher the efficiency will be. With 80 serially connected SMD3528 LEDs, you will need an 800 ohm resistor with a power of only 0.5 watts. Capacitor C1 will need to be increased to 4.7 µF.
Finding faulty LEDs
After removing the protective glass, it becomes possible to check the LEDs without peeling off the printed circuit board. First of all, a careful inspection of each LED is carried out. If even the smallest black dot is detected, not to mention the blackening of the entire surface of the LED, then it is definitely faulty.
When examining the appearance of the LEDs, you need to carefully examine the quality of the rations of their conclusions. In one of the light bulbs being repaired, four LEDs were poorly soldered at once.
The photo shows a light bulb that had very small black dots on four LEDs. I immediately marked the faulty LEDs with crosses so that they could be clearly seen.
Faulty LEDs may or may not change appearance. Therefore, it is necessary to check each LED with a multimeter or arrow tester included in the resistance measurement mode.
There are LED lamps in which standard LEDs are installed in appearance, in the case of which two crystals connected in series are mounted at once. For example, lamps of the ASD LED-A60 series. To make such LEDs ring, it is necessary to apply a voltage of more than 6 V to its terminals, and any multimeter gives out no more than 4 V. Therefore, such LEDs can only be checked by applying a voltage of more than 6 (9-12) V through a 1 kΩ resistor from the power source. .
The LED is checked, like a conventional diode, in one direction the resistance should be equal to tens of megaohms, and if you change the probes in places (this changes the polarity of the voltage supply to the LED), then it is small, while the LED may glow dimly.
When checking and replacing LEDs, the lamp must be fixed. For this you can use right size round jar.
You can check the health of the LED without additional source direct current. But such a verification method is possible if the light bulb driver is working. To do this, it is necessary to apply a supply voltage to the LED lamp base and short the leads of each LED in series with each other with a wire jumper or, for example, metal tweezers sponges.
If suddenly all the LEDs light up, then the shorted one is definitely faulty. This method is useful if only one LED out of all in the circuit is faulty. With this method of verification, it must be taken into account that if the driver does not provide galvanic isolation from the mains, as, for example, in the diagrams above, then touching the LED solderings with your hand is unsafe.
If one or even several LEDs turned out to be faulty and there is nothing to replace them with, then you can simply short-circuit the pads to which the LEDs were soldered. The light bulb will work with the same success, only the luminous flux will decrease slightly.
Other malfunctions of LED lamps
If the check of the LEDs showed their serviceability, then it means that the reason for the inoperability of the light bulb lies in the driver or in the places where the current-carrying conductors are soldered.
For example, in this light bulb, a cold soldered conductor was found that supplies voltage to the printed circuit board. The soot released due to poor soldering even settled on the conductive tracks of the printed circuit board. The soot was easily removed by wiping with a rag soaked in alcohol. The wire was soldered, stripped, tinned and re-soldered into the board. Good luck with this lamp.
Of the ten failed light bulbs, only one had a faulty driver, the diode bridge fell apart. The repair of the driver consisted in replacing the diode bridge with four IN4007 diodes, designed for a reverse voltage of 1000 V and a current of 1 A.
Soldering SMD LEDs
To replace a faulty LED, it must be desoldered without damaging the printed conductors. From the donor board, you also need to solder the replacement LED without damage.
Solder SMD LEDs simple soldering iron without damaging their hull is almost impossible. But if you use a special tip for a soldering iron or put on a standard tip a nozzle made of copper wire, then the problem is easily solved.
The LEDs have polarity and when replacing, you need to correctly install it on the printed circuit board. Typically, printed conductors follow the shape of the leads on the LED. Therefore, you can make a mistake only if you are inattentive. To solder the LED, it is enough to install it on a printed circuit board and heat its ends with contact pads with a soldering iron with a power of 10-15 W.
If the LED burned out on coal, and the printed circuit board under it was charred, then before installing a new LED, it is imperative to clean this place of the printed circuit board from burning, since it is a current conductor. When cleaning, you may find that the pads for soldering the LED are burned or peeled off.
In such a case, the LED can be installed by soldering it to adjacent LEDs if the printed tracks lead to them. To do this, you can take a piece of thin wire, bend it in half or three, depending on the distance between the LEDs, tin and solder to them.
Repair LED lamp series "LL-CORN" (corn lamp)
E27 4.6W 36x5050SMD
The device of the lamp, which is popularly called the corn lamp, shown in the photo below, differs from the lamp described above, therefore the repair technology is different.
The design of LED SMD lamps of this type is very convenient for repair, as there is access for LED continuity and replacement without disassembling the lamp housing. True, I still dismantled the light bulb for interest in order to study its device.
Checking the LEDs of the LED corn lamp does not differ from the technology described above, but it must be taken into account that three LEDs are placed in the SMD5050 LED housing at once, usually connected in parallel (three dark dots of crystals are visible on the yellow circle), and when checking, all three should glow.
A defective LED can be replaced with a new one or shorted with a jumper. This will not affect the reliability of the lamp, only imperceptibly to the eye, the luminous flux will decrease slightly.
The driver of this lamp is assembled according to the simplest scheme, without an isolation transformer, so touching the LED terminals when the lamp is on is unacceptable. Lamps of this design are unacceptable to be installed in fixtures that can be reached by children.
If all the LEDs are working, then the driver is faulty, and in order to get to it, the lamp will have to be disassembled.
To do this, remove the bezel from the side opposite the base. With a small screwdriver or a knife blade, you need to try in a circle to find weakness where the bezel is the worst glued. If the rim succumbed, then working with the tool as a lever, the rim will easily move away around the entire perimeter.
The driver was assembled according to the electrical circuit, like the MR-16 lamp, only C1 had a capacity of 1 µF, and C2 - 4.7 µF. Due to the fact that the wires from the driver to the lamp base were long, the driver was easily pulled out of the lamp housing. After studying his circuit, the driver was inserted back into the case, and the bezel was glued in place with Moment transparent glue. The failed LED was replaced with a good one.
Repair of LED lamp "LL-CORN" (corn lamp)
E27 12W 80x5050SMD
When repairing a more powerful lamp, 12 W, there were no failed LEDs of the same design, and in order to get to the drivers, I had to open the lamp using the technology described above.
This lamp gave me a surprise. The wires from the driver to the base were short, and it was impossible to remove the driver from the lamp housing for repair. I had to remove the plinth.
The base of the lamp was made of aluminium, rounded and held tight. I had to drill out the attachment points with a 1.5 mm drill. After that, the plinth, which was hooked with a knife, was easily removed.
But you can do without drilling the base, if you pry the edge of the knife around the circumference and slightly bend its upper edge. A mark should first be placed on the plinth and body so that the plinth can be easily installed in place. To securely fix the base after repairing the lamp, it will be enough to put it on the lamp body in such a way that the punched points on the base fall into their old places. Next, push these points with a sharp object.
Two wires were connected to the thread with a clamp, and the other two were pressed into the central contact of the base. I had to cut these wires.
As expected, there were two identical drivers, feeding 43 diodes each. They were covered with heat shrink tubing and taped together. In order for the driver to be placed back into the tube, I usually carefully cut it along the printed circuit board from the side where the parts are installed.
After repair, the driver is wrapped in a tube, which is fixed with a plastic tie or wrapped with several turns of thread.
In the electrical circuit of the driver of this lamp, protection elements are already installed, C1 for protection against impulse surges and R2, R3 for protection against current surges. When checking the elements, resistors R2 were immediately found on both drivers in the open. It appears that the LED lamp was supplied with a voltage exceeding the allowable voltage. After replacing the resistors, there was no 10 Ohm at hand, and I set it to 5.1 Ohm, the lamp worked.
Repair LED lamp series "LLB" LR-EW5N-5
The appearance of this type of light bulb inspires confidence. Aluminum case, high-quality workmanship, beautiful design.
The design of the light bulb is such that it is impossible to disassemble it without the use of significant physical effort. Since the repair of any LED lamp begins with checking the health of the LEDs, the first thing that had to be done was to remove the plastic protective glass.
The glass was fixed without glue on a groove made in the radiator with a shoulder inside it. To remove the glass, you need to use the end of a screwdriver, which will pass between the radiator fins, to lean on the end of the radiator and, as a lever, lift the glass up.
Checking the LEDs with a tester showed their serviceability, therefore, the driver is faulty, and you need to get to it. The aluminum board was fastened with four screws, which I unscrewed.
But contrary to expectations, behind the board was the plane of the radiator, lubricated with heat-conducting paste. The board had to be returned to its place and continue to disassemble the lamp from the side of the base.
Due to the fact that the plastic part to which the radiator was attached was very tight, I decided to go the proven way, remove the base and remove the driver for repair through the hole that opened. I drilled out the punching points, but the base was not removed. It turned out that he was still holding on to the plastic due to the threaded connection.
I had to separate the plastic adapter from the radiator. He held, as well as protective glass. To do this, washed down with a hacksaw at the junction of the plastic with the radiator and by turning a screwdriver with a wide blade, the parts were separated from each other.
After soldering the leads from the printed circuit board of the LEDs, the driver became available for repair. The driver circuit turned out to be more complex than previous light bulbs, with an isolation transformer and a microcircuit. One of the 400 V 4.7 µF electrolytic capacitors was swollen. I had to replace it.
A check of all semiconductor elements revealed a faulty Schottky diode D4 (pictured below left). There was a SS110 Schottky diode on the board, I replaced it with the existing analog 10 BQ100 (100 V, 1 A). The forward resistance of Schottky diodes is two times less than that of ordinary diodes. The LED lamp lit up. The same problem was with the second bulb.
Repair LED lamp series "LLB" LR-EW5N-3
This LED lamp is very similar in appearance to the "LLB" LR-EW5N-5, but its design is somewhat different.
If you look closely, you can see that at the junction between aluminum radiator and spherical glass, unlike LR-EW5N-5, there is a ring in which the glass is fixed. To remove the protective glass, just use a small screwdriver to pick it up at the junction with the ring.
There are three nine crystal superbright LEDs on the aluminum circuit board. The board is screwed to the heatsink with three screws. Checking the LEDs showed their serviceability. Therefore, you need to repair the driver. Having experience in repairing a similar LED lamp "LLB" LR-EW5N-5, I did not unscrew the screws, but soldered the current-carrying wires coming from the driver and continued to disassemble the lamp from the side of the base.
The plastic connecting ring of the plinth with the radiator was removed with great difficulty. At the same time, part of it broke off. As it turned out, it was screwed to the radiator with three self-tapping screws. The driver is easily removed from the lamp housing.
The self-tapping screws that screw the plastic ring of the base cover the driver, and it is difficult to see them, but they are on the same axis with the thread to which the adapter part of the radiator is screwed. Therefore, a thin Phillips screwdriver can be reached.
The driver turned out to be assembled according to the transformer circuit. Checking all the elements, except for the microcircuit, did not reveal any failed ones. Therefore, the microcircuit is faulty, I did not even find a mention of its type on the Internet. The LED bulb could not be repaired, it will come in handy for spare parts. But studied her device.
Repair LED lamp series "LL" GU10-3W
It turned out, at first glance, that it was impossible to disassemble a burned-out GU10-3W LED bulb with a protective glass. An attempt to remove the glass led to its puncture. With the application of great effort, the glass cracked.
By the way, in the marking of the lamp, the letter G means that the lamp has a pin base, the letter U means that the lamp belongs to the class of energy-saving light bulbs, and the number 10 means the distance between the pins in millimeters.
LED bulbs with a GU10 base have special pins and are installed in a socket with a turn. Thanks to the expanding pins, the LED lamp is clamped in the socket and is held securely even when shaking.
In order to disassemble this LED light bulb, I had to drill a hole with a diameter of 2.5 mm in its aluminum case at the level of the surface of the printed circuit board. The drilling location must be chosen in such a way that the drill does not damage the LED when exiting. If there is no drill at hand, then the hole can be made with a thick awl.
Next, a small screwdriver is threaded into the hole and, acting like a lever, the glass is lifted. I removed the glass from two light bulbs without problems. If the test of the LEDs by the tester showed their serviceability, then the printed circuit board is removed.
After separating the board from the lamp housing, it immediately became obvious that the current-limiting resistors burned out in both one and the other lamp. The calculator determined their denomination from the bands, 160 ohms. Since the resistors burned out in LED bulbs of different batches, it is obvious that their power, judging by the size of 0.25 W, does not correspond to the power released when the driver is operating at maximum ambient temperature.
The printed circuit board of the driver was solidly filled with silicone, and I did not disconnect it from the board with LEDs. I cut off the leads of the burnt resistors at the base and soldered more powerful resistors to them, which were at hand. In one lamp, a 150 Ohm resistor with a power of 1 W was soldered, in the second two in parallel 320 Ohm with a power of 0.5 W.
In order to prevent accidental contact with the output of the resistor, to which the mains voltage is suitable with the metal body of the lamp, it was insulated with a drop of hot melt adhesive. It is waterproof and an excellent insulator. I often use it for sealing, insulating and securing electrical wires and other parts.
Hot melt adhesive is available in the form of rods with a diameter of 7, 12, 15 and 24 mm different colors, transparent to black. It melts, depending on the brand, at a temperature of 80-150 °, which allows it to be melted with an electric soldering iron. It is enough to cut off a piece of the rod, place it in the right place and heat it up. The hot melt will take on the consistency of May honey. After cooling it becomes solid again. When reheated, it becomes liquid again.
After replacing the resistors, the performance of both bulbs was restored. It remains only to fix the printed circuit board and the protective glass in the lamp housing.
When repairing LED lamps, I used liquid nails "Installation" moment to fix printed circuit boards and plastic parts. The glue is odorless, adheres well to the surfaces of any materials, remains plastic after drying, has sufficient heat resistance.
It is enough to take a small amount of glue on the end of a screwdriver and apply it to the places where the parts come into contact. After 15 minutes, the glue will already hold.
When gluing the printed circuit board, in order not to wait, holding the board in place, as the wires pushed it out, fixed the board additionally at several points with hot glue.
The LED lamp began to flash like a strobe
I had to repair a pair of LED lamps with drivers assembled on a microcircuit, the malfunction of which consisted in flashing light at a frequency of about one hertz, like in a strobe.
One instance of the LED lamp began to flash immediately after being turned on for the first few seconds and then the lamp began to glow normally. Over time, the duration of the lamp flashing after switching on began to increase, and the lamp began to flash continuously. The second copy of the LED lamp began to flash continuously all of a sudden.
After disassembling the lamps, it turned out that the electrolytic capacitors installed immediately after the rectifier bridges failed in the drivers. It was easy to determine the malfunction, since the capacitor cases were swollen. But even if the capacitor looks without external defects in appearance, it is still necessary to start repairing the LED light bulb with a stroboscopic effect by replacing it.
After replacing the electrolytic capacitors with serviceable ones, the stroboscopic effect disappeared and the lamps began to shine normally.
Online calculators for determining the value of resistors
by color coding
When repairing LED lamps, it becomes necessary to determine the value of the resistor. According to the standard, the marking of modern resistors is carried out by applying colored rings to their cases. 4 colored rings are applied to simple resistors, and 5 to high-precision resistors.
LED lamps in many respects correspond to fluorescent lamps: dimensions and appearance, brightness of the glow, the same base. LEDs differ from fluorescent lamps in their long service life, light source and no need for special disposal.
Thanks to this similarity, it became possible to save money - to replace only the light source in failed or obsolete lamps, leaving the old frame.
Replacing fluorescent lamps with LED ones does not require special skills - if there is an algorithm of actions, the home master will also cope with the alteration on his own.
Rework Benefits
The minimum value of the duration of the LED lamp, declared by the manufacturers, is 30,000 hours. Much depends on light elements and electronic ballast. But the benefit of redesigning a fluorescent lighting fixture is obvious for a number of reasons.
Consider which is better - LED lamps or fluorescent lamps:
- The main difference between fluorescent lamps and LED lamps is energy consumption. Fluorescent fixtures use 60% more electricity.
- LED lighting fixtures are more durable in operation. The average value of the service life is 40-45 thousand hours.
- LEDs do not need maintenance and revision, it is enough to remove dust and sometimes change tubes.
- LED tubes do not blink, it is advisable to install them in children's institutions.
- The tubes do not contain toxic substances, do not require disposal after the end of their service life.
- LED analogues of fluorescent lamps also work with voltage drops in the network.
- The next advantage of LEDs is the availability of models designed to operate on supply voltages from 85 V to 265 V. A fluorescent lamp requires uninterrupted power supply of 220 V or close to it.
- LED counterparts have practically no drawbacks, with the exception of the high cost of premium models.
Luminaires with electromagnetic control gear
When converting a fluorescent device into an LED one, pay attention to its design. If you're redoing old lamp times Soviet Union with a starter and electromagnetic ballast (ballast), almost no upgrade is required.
The first step is to pull out the starter, pick up the LED of the required size and insert it into the housing. Enjoy bright and economical lighting.
If the starter is not dismantled, replacing fluorescent lamps with LED ones may cause a short circuit. Throttle does not need to be removed. LED current consumption - an average of 0.15 A; the part will serve as a jumper.
After replacing the lamps, the luminaire will remain the same, there is no need to change the ceiling mount. The handsets are equipped with built-in drivers and power supplies.
Alteration of the lamp with electronic control gear
If the illuminator model is more modern - electronic ballast choke and no starter - you will have to make an effort and change the connection diagram of the LED tubes.
Components of the lamp before replacement:
- throttle;
- wires;
- pads-cartridges located on both sides of the body.
We get rid of the throttle first of all, because. without this element, the design will become easier. Unscrew the mount and disconnect the power wires. Use a screwdriver with a narrow tip or pliers for this.
The main thing is to connect 220 V to the ends of the tube: apply the phase to one end, and zero to the other.
LEDs have a feature - 2 contacts on the base in the form of pins are rigidly interconnected. And in fluorescent tubes, the contacts are connected by a filament, which, when heated, ignites mercury vapor.
In lighting devices with electronic gear, no filament is used, and a voltage pulse breaks through between the contacts.
It is not so easy to apply 220 V between contacts with a hard connection.
Use a multimeter to verify that the voltage is being applied correctly. Set the device to the resistance measurement mode, touch the measuring probes to two contacts and take measurements. The multimeter display should show a zero value or close to it.
In LED lamps, between the output contacts there is a filament, which has its own resistance. After applying voltage through it, the filament heats up and sets the lamp to work.
Further connection of the LED lamp is recommended to be done by 2 methods:
- without dismantling cartridges;
- with dismantling and installation of jumpers between contacts.
without dismantling
Refusing to dismantle the cartridge is an easier way: there is no need to understand the circuit, make jumpers, climb into the middle of the cartridge and fiddle with the contacts. Before dismantling, you need to buy a few Wago clamps. Remove the wires leading to the cartridge at a distance of 1-2 cm. Insert them into the Wago clamp.
Do the same on the other side lighting device. It remains to apply a phase to the terminal block on one side, and zero on the other. If it was not possible to purchase clamps, twist the wires under the PPE cap.
With the dismantling of cartridges and the installation of jumpers
This method is more meticulous, but does not require the purchase of additional parts.
Action algorithm:
- Carefully remove the covers from the sides of the lamp.
- Dismountable cartridges with insulated contacts located inside. There are also springs inside the cartridge, which are necessary for better fastening of the lamp.
- 2 power wires lead to the cartridge, which are fastened in special contacts without screws by snapping. Scroll them clockwise and counterclockwise. After that, by force we get one of the wires.
- Because the contacts are isolated, when dismantling one of the wires, the current will pass through only one socket. This will not affect the performance of the lamp, but it is better to put a jumper and thereby improve the device.
- Thanks to the jumper, you do not need to try to catch the contact by turning the LED tube to the sides.
- It is recommended to make a fixture from the extra supply wires of the main lighting fixture, which will remain after the work of replacing the lamps.
- The next step is to check for continuity between the isolated connectors after the jumper is installed. We perform similar actions on the other side of the lamp.
- Follow the rest of the power wire. It should be zero, not phase. Remove the rest with pliers.
Fluorescent lamps for two, four or more lamps
If you are converting the lamp to 2 or more lamps, it is recommended to apply voltage to each of the connectors with different conductors. The design has a drawback when installing a jumper between multiple cartridges. If the first tube is installed in the wrong place, the second one will not light up. You take out the first tube - the second goes out.
On the terminal block, to which the phase, zero, ground are connected in turn, bring the conductors that supply voltage.
Before attaching the luminaire to the ceiling, check the operation of the lamps. Apply voltage; adjust outgoing contacts if necessary.
LED lamps give out a directional beam of light, unlike daylight devices, in which illumination occurs 360 °. But the function of turning 35 ° in the base and the rotation of the base itself will help to adjust and direct the flow of light in the right direction.
Not every base in the lamp is equipped with this function. In this case, move the chuck holder 90°. After checking, fix the device in the right place.
The benefits of replacing lamps are clear:
- rework methods do not require special skills and knowledge, in addition, they are cheap;
- more economical energy consumption;
- the illumination is higher than that of fluorescent devices.
Extend the life of outdated fixtures and enjoy and benefit from bright, affordable lighting.
Disassembly and refinement of Chinese LED lamps
On our site there are enough publications devoted to light sources. These are, first of all, incandescent lamps; here we found a solution how to protect them from burning out and extend their service life. Perhaps, they still remain the most massive source of light, and the reason here is not only in availability, but also in the fact that the spectrum of their radiation is most pleasing to the eye. In addition to conventional light bulbs, the so-called "energy-saving" - compact fluorescent lamps - are popular. We gave a description of the repair and modification methods that also increase the service life. However, LED light sources should also be considered as gaining popularity.
An LED lamp consists of several LEDs (or an LED matrix) with a power supply circuit enclosed in a base. Proper nutrition LEDs are a whole science, since there are plenty of power supply drivers, from specialized microcircuits to simple circuits on two transistors. However, manufacturers very rarely use the achievements of circuitry and modern electronics, preferring to feed the LEDs out of habit - through a ballast (quenching) capacitor.
For the study, three 3W LED lamps manufactured in China were purchased at a price of 35 rubles per piece.
The case is made of plastic, the diffuser in the form of a hemisphere is also made of plastic, it is attached without glue, it simply snaps into place. To disassemble the LED lamp, it is enough to pry the diffuser in a circle and disengage it from the lamp body. This releases the printed circuit board with parts.
In two out of three lamps, one wire is not soldered, otherwise the installation is more or less neat. The quenching capacitor marked 824 is at 820nF (0.82uF), 400V. 9 LEDs of size similar to 3528, only thinner, connected in series. The bridge is assembled from four diodes marked M7.
One such lamp shines very weakly. With a lamp power of 3W, its light should be comparable to an incandescent lamp with a power of 20-25W. These lamps shine more dimly, which, as it were, hints at the need for measurement, which will soon be done, at the same time the need for improvement will be clarified - is there a significant current surge when turned on, do the LEDs work, as they say, "with overheating"?
The scheme of the LED lamp is simple. As already mentioned, the LEDs are powered through a quenching capacitor.
The simulation shows that the current flowing through the LEDs is 32mA, the total voltage drop across the chain of nine LEDs is 26V, so the power consumed by them is 0.8W, which is three times less than the declared one.
These lamps are sold as three-watt. Of course, their real power is three times less. Each lamp has 10 2835 LEDs. Judging by the datasheets, these LEDs allow current up to 150mA with good heat dissipation. In this particular case, the whole thing is powered through a ballast capacitor with a capacity of 0.82 microfarads and a 100 ohm resistor connected in series. Closing the resistor does not significantly affect the brightness of the glow. The lamps are very dim.
It is disassembled by simply tilting the matte diffuser to the side. The LED board is fixed with silicone glue.
The following alteration was planned: to increase the capacity of the ballast capacitor in order to increase the current. For testing, a capacitor with a capacity of 1.5 microfarads was installed. At the same time, the aluminum substrate of the LEDs heated up excessively. Therefore, the refinement of these lamps was impossible.
The following lamps are uncle Liao's more honest products. The lamp is designed to be powered by 12 volts (halogen power supplies). The case is also a radiator made of honest aluminum.
The lamps are made on the basis of 1 watt LEDs connected in series. Inside the base there is an ultra-compact stabilizer of who knows what, which (attention!) Does not work. The brightness of the lamps varies depending on the supply voltage. And this despite the fact that under the heat shrink in one of the lamps the famous MC34063 and XL6001 are hidden in the other.
It is disassembled by unscrewing the upper and lower parts.
Possible alteration: convert to 220 volts and a "human" base. In this case, a redesign of the lamp design is required.
Finishing large corn. The lamps themselves are easy to disassemble - by removing the plastic ring at the end. It is fixed with small rods, some of which can be glued. They will have to be torn off. When the ring is removed, a round platform with LEDs will be released. Inside the lamp there is a small board with a capacitor ballast, on which an electrolytic capacitor with a capacity of 4.7 microfarads is installed. This capacity is clearly not enough for a given lamp power, resulting in a flicker that is invisible to the eye. There is another, not obvious drawback: the small capacity of this electrolyte is an insufficient load for the capacitor ballast at the beginning of work. As you know, a discharged capacitor has zero resistance and when the lamp is turned on, a voltage jump occurs, which may well burn out some LED. To protect against this unpleasant phenomenon, a larger capacitor should be installed, which will provide the necessary voltage drop when turned on, or shunt the LEDs with a zener diode. The second option is more complicated (you also need to find a zener diode at a relatively high voltage) and does not get rid of flicker, so the obvious refinement is to install electrolytic capacitor greater capacity.
Initially, the payment is not received, because. connected by short wires to the lamp base. Pulling it out as much as possible, solder the wires. It is quite possible to do so. We solder the 4.7 uF capacitor and install a more capacious one in its place, in this case, 68 uF 450V. The place inside the lamp allows you to install it from the back of the board. We don’t install the zener diode yet - we drive the lamp like this.
Everything is assembled in reverse order. It should also be remembered that a lamp with a capacitor ballast is galvanically connected to the network and is dangerous. Therefore, it will not be superfluous to stick or draw the appropriate symbols to avoid touching live parts. Actually, almost the entire lamp - and there are such parts. When installing or removing it, you need to hold it very carefully, by the plastic ring.
