uptostart.ru News. Games. Instructions. Internet. Office.
The topic of converting or upgrading failed fluorescent (energy-saving) lamps into LED lamps has been raised more than once. May the authors of these articles forgive me, but most of the proposed options are ineffective and certainly not aesthetically pleasing. This is due to the difficulties with the element base and components, as well as our mentality when we try to make a candy out of...
But thanks to the Koreans, who last year released the wonderful Seoul Semiconductors Acrich2 LED module, which connects to a 220 V AC network without an additional power source. The manufacturer guarantees that, subject to operating conditions (recommended operating temperature not higher than 70 ºС), this module will honestly work for at least 50,000 hours. We will not go into technical details, everything is clear from the picture.
As a comment
In my line of work, I have extensive experience working with various power sources. So, the power supply resource of 15,000 hours indicated by the Koreans is approximately 2 times overestimated, this is provided that high-quality electrolytes are used. Chinese consumer goods, which are now widely available, clearly do not fall into the category of quality goods.
So, we figured out the light source. The next step is how to cool it. Fencing a banal finned radiator is not aesthetically pleasing and inconvenient. And there was some luck here. It turns out that the AP888 radiator profile, specially designed for modules of this series, has been developed and produced in Russia.
The profile is universal, designed for installation of three types of Acriche modules: AW3221 (4 W) and Acrich2 for 8 and 12 W.
Further work to modernize the burnt out energy saving lamp It wasn’t difficult at all and only took 15-20 minutes.
1 Cut the heatsink to the size required to ensure efficient cooling of the module. The profile supplier recommends the following dimensions to ensure an operating temperature of no more than 70 ºC:
- 4 W – 10-15 mm;
- 8 W – 30-35 mm;
- 12 W – 40-45 mm.
IN in this case“You can’t spoil the porridge with oil,” and for 8 W I took a 50 mm radiator.
3 Drill holes in the cover of the plinth housing to mount the radiator.
4 All components - radiator, module and filter for the module, are ready for assembly.
5 Then everything is simple. We install the module on the radiator, do not forget about the heat-conducting paste (I recommend KTP-8). We attach the cover of the base housing to the radiator. Solder the wires to the module and filter. Then we solder everything into the base.
Currently, so-called energy-saving fluorescent lamps are becoming increasingly widespread. Unlike usual fluorescent lamps with electromagnetic ballast, energy-saving lamps with electronic ballast use a special circuit.
Thanks to this, such lamps can be easily installed in a socket instead of a conventional incandescent light bulb with a standard E27 and E14 socket. It is about household fluorescent lamps with electronic ballast that will be discussed further.
Distinctive features of fluorescent lamps from conventional incandescent lamps.
It is not for nothing that fluorescent lamps are called energy-saving, since their use can reduce energy consumption by 20 - 25%. Their emission spectrum is more consistent with natural daylight. Depending on the composition of the phosphor used, it is possible to produce lamps with different shades of glow, both warmer tones and colder ones. It should be noted that fluorescent lamps are more durable than incandescent lamps. Of course, a lot depends on the quality of the design and manufacturing technology.
Compact fluorescent lamp (CFL) device.
A compact fluorescent lamp with electronic ballast (abbreviated CFL) consists of a bulb, an electronic board and an E27 (E14) socket, with which it is installed in a standard socket.
Inside the case there is a round printed circuit board on which the high-frequency converter is assembled. The converter at rated load has a frequency of 40 - 60 kHz. As a result of the fact that a fairly high conversion frequency is used, the “blinking” characteristic of fluorescent lamps with an electromagnetic ballast (based on a choke), which operate at a power supply frequency of 50 Hz, is eliminated. The schematic diagram of a CFL is shown in the figure.
According to this concept, mostly fairly cheap models are assembled, for example, those produced under the brand Navigator And ERA. If you use compact fluorescent lamps, then most likely they are assembled according to the above diagram. The spread of the values of the parameters of resistors and capacitors indicated on the diagram actually exists. This is due to the fact that for lamps of different wattages elements with different parameters. Otherwise, the circuit design of such lamps is not much different.
Let's take a closer look at the purpose of the radioelements shown in the diagram. On transistors VT1 And VT2 a high-frequency generator has been assembled. Silicon high-voltage transistors are used as transistors VT1 and VT2 n-p-n MJE13003 series transistors in TO-126 package. Typically, only the digital index 13003 is indicated on the housing of these transistors. MPSA42 transistors in a smaller TO-92 format or similar high-voltage transistors can also be used.
Miniature symmetrical dinistor DB3 (VS1) serves to autostart the converter at the moment of power supply. Externally, the DB3 dinistor looks like a miniature diode. An autostart circuit is necessary because the converter is assembled according to a circuit with current feedback and therefore does not start on its own. In low-power lamps, the dinistor may be absent altogether.
Diode bridge made on elements VD1 – VD4 serves to rectify alternating current. Electrolytic capacitor C2 smoothes out the ripples of the rectified voltage. The diode bridge and capacitor C2 are the simplest network rectifier. From capacitor C2, constant voltage is supplied to the converter. The diode bridge can be designed as individual elements(4 diodes), or a diode assembly can be used.
During its operation, the converter generates high-frequency interference, which is undesirable. Capacitor C1, choke (inductor) L1 and resistor R1 prevent the spread of high-frequency interference through the electrical network. In some lamps, apparently to save money :) a wire jumper is installed instead of L1. Also, many models do not have a fuse FU1, which is indicated in the diagram. In such cases, the breaking resistor R1 also plays the role of a simple fuse. If the electronic circuit malfunctions, the current consumed exceeds a certain value, and the resistor burns out, breaking the circuit.
Throttle L2 usually assembled at Sh-figurative ferrite magnetic core and looks like a miniature armored transformer. On the printed circuit board this inductor takes up quite an impressive amount of space. The inductor winding L2 contains 200 - 400 turns of wire with a diameter of 0.2 mm. You can also find a transformer on the printed circuit board, which is indicated on the diagram as T1. Transformer T1 is assembled on a ring magnetic core with an outer diameter of about 10 mm. The transformer has 3 windings wound with mounting or winding wire with a diameter of 0.3 - 0.4 mm. The number of turns of each winding ranges from 2 - 3 to 6 - 10.
The fluorescent lamp bulb has 4 leads from 2 spirals. The leads of the spirals are connected to the electronic board using the cold twist method, that is, without soldering and are screwed onto rigid wire pins that are soldered into the board. In low-power lamps with small dimensions, the leads of the spirals are soldered directly into the electronic board.
Repair of household fluorescent lamps with electronic ballast.
Manufacturers of compact fluorescent lamps claim that their lifespan is several times longer than that of conventional incandescent lamps. But despite this, household fluorescent lamps with electronic ballast fail quite often.
This is due to the fact that they use electronic components that are not designed to withstand overloads. It is also worth noting the high percentage of defective products and low quality workmanship. Compared to incandescent lamps, the cost of fluorescent lamps is quite high, so repairing such lamps is justified at least for personal purposes. Practice shows that the cause of failure is mainly a malfunction of the electronic part (converter). After a simple repair, the performance of the CFL is completely restored and this allows you to reduce financial costs.
Before we start talking about CFL repairs, let’s touch on the topic of ecology and safety.
Despite their positive qualities, fluorescent lamps are harmful to both the environment and human health. The fact is that there are mercury vapors in the flask. If it is broken, dangerous mercury vapors will enter the environment and, possibly, the human body. Mercury is classified as a substance 1st hazard class .
If the flask is damaged, you must leave the room for 15–20 minutes and immediately forcefully ventilate the room. You must be careful when using any fluorescent lamps. It should be remembered that mercury compounds used in energy-saving lamps are more dangerous than ordinary metallic mercury. Mercury can remain in the human body and cause harm to health.
In addition to this disadvantage, it should be noted that the emission spectrum of a fluorescent lamp contains harmful ultraviolet radiation. If you stay close to a fluorescent lamp for a long time, skin irritation is possible, as it is sensitive to ultraviolet radiation.
The presence of highly toxic mercury compounds in the bulb is the main motive of environmentalists who call for reducing the production of fluorescent lamps and switching to safer LED lamps.
Disassembling a fluorescent lamp with electronic ballast.
Despite the ease of disassembling a compact fluorescent lamp, you should be careful not to break the bulb. As already mentioned, there are mercury vapors inside the flask that are hazardous to health. Unfortunately, the strength of glass flasks is low and leaves much to be desired.
In order to open the housing where the electronic circuit of the converter is located, it is necessary to release the plastic latch that holds the two plastic parts of the housing together with a sharp object (a narrow screwdriver).
Next, you should disconnect the leads of the spirals from the main electronic circuit. It is better to do this with narrow pliers, picking up the end of the spiral wire output and unwinding the turns from the wire pins. After this, it is better to place the glass flask in a safe place to prevent it from breaking.
The remaining electronic board is connected by two conductors to the second part of the housing, on which a standard E27 (E14) base is mounted.
Restoring the functionality of lamps with electronic ballast.
When restoring a CFL, the first step is to check the integrity of the filaments (spirals) inside the glass bulb. The integrity of the filaments can be easily checked using a regular ohmmeter. If the resistance of the threads is low (a few ohms), then the thread is working. If during measurement the resistance is infinitely high, then the filament has burned out and it is impossible to use the bulb in this case.
The most vulnerable components of an electronic converter made on the basis of the circuit already described (see circuit diagram) are capacitors.
If the fluorescent lamp does not turn on, then capacitors C3, C4, C5 should be checked for breakdown. When overloaded, these capacitors fail because the applied voltage exceeds the voltage for which they are designed. If the lamp does not turn on, but the bulb glows in the area of the electrodes, then capacitor C5 may be broken.
In this case, the converter is working properly, but since the capacitor is broken, a discharge does not occur in the bulb. Capacitor C5 is included in an oscillatory circuit, in which, at the moment of startup, a high-voltage pulse occurs, leading to the appearance of a discharge. Therefore, if the capacitor is broken, the lamp will not be able to switch to operating mode normally, and a glow caused by heating of the spirals will be observed in the area of the spirals.
Cold And hot mode starting fluorescent lamps.
There are two types of household fluorescent lamps:
With cold start
With hot start
If the CFL lights up immediately after switching on, then it has a cold start. This mode is bad because in this mode the cathodes of the lamp are not preheated. This can lead to burnout of the filaments due to the flow of a current pulse.
For fluorescent lamps, hot starting is preferable. During a hot start, the lamp lights up smoothly within 1-3 seconds. During these few seconds, the filaments heat up. It is known that a cold filament has less resistance than a heated filament. Therefore, during a cold start, a significant current pulse passes through the filament, which can eventually cause it to burn out.
For conventional incandescent lamps, a cold start is standard, so many people know that they burn out just the moment they are turned on.
To implement hot start in lamps with electronic ballast, the following scheme is used. A posistor (PTC - thermistor) is connected in series with the filaments. In the circuit diagram, this posistor will be connected in parallel with capacitor C5.
At the moment of switching on, as a result of resonance, a high voltage appears on the capacitor C5, and, consequently, on the electrodes of the lamp, necessary for its ignition. But in this case, the filaments are poorly heated. The lamp turns on instantly. In this case, a posistor is connected in parallel with C5. At the moment of startup, the posistor has a low resistance and the quality factor of the L2C5 circuit is significantly lower.
As a result, the resonance voltage is below the ignition threshold. Within a few seconds the posistor heats up and its resistance increases. At the same time, the filaments also heat up. The quality factor of the circuit increases and, consequently, the voltage at the electrodes increases. A smooth hot start of the lamp occurs. In operating mode, the posistor has a high resistance and does not affect the operating mode.
It is not uncommon that this particular posistor fails, and the lamp simply does not turn on. Therefore, when repairing lamps with ballast, you should pay attention to it.
Quite often, the low-resistance resistor R1 burns out, which, as already mentioned, plays the role of a fuse.
Active elements such as transistors VT1, VT2, rectifier bridge diodes VD1 - VD4 are also worth checking. As a rule, the cause of their malfunction is an electrical breakdown. p-n transitions. Dinistor VS1 and electrolytic capacitor C2 rarely fail in practice.
You need to start saving energy from the very beginning - by installing lamps that will help save energy. But unfortunately, the service life of such products is shorter than what the manufacturers indicate on the packaging. There are cases when such lamps last for about six months. Therefore, the question of repairing and converting energy-saving lamps into LEDs is very relevant in our time.
Of all the variety existing systems lighting use LED lamps remains the most effective, convenient, profitable and environmentally friendly. Therefore, they are becoming increasingly popular in our modern apartments.
How to make an LED lamp from an energy-saving lamp
Converting an energy-saving lamp into an LED lamp is possible from almost any version of an old non-working lamp. To do this, you need to remove the internal boards of the converters and replace it with a circuit to reduce the supply voltages of the LED elements. At the same time, we set the current for the LED and set the resistor to 100 to 200 Ohms.
In order to create an energy-saving LED lamp with your own hands, first, you need to disassemble the product. When disassembling, it is necessary to remove the board with converters and the lamp itself. This is best done with a small screwdriver.
Most often, breakdown of an energy-saving lamp occurs due to its burnout. After disassembly, the cartridge and base should remain. The assembled circuit with LED and reflectors is installed on them. Then LEDs with their required quantity are attached to the lamp.
When creating an LED lamp at home, it is important to use high-quality LED lamps so that they shine brightly and perform all the necessary functions.
Of course, you can buy yourself a ready-made LED product, but their cost is quite high, unlike standard incandescent, fluorescent or energy-saving lamps.
In order to create an energy-saving LED lamp with your own hands, you will need:
- Any old non-working lamp.
- Fiberglass for connecting parts together. There are other options for attaching LEDs without soldering.
- Additional elements that are in the circuit, which necessarily contain LEDs. In order to save as much as possible, use all available means.
- Capacitors that are suitable for a maximum voltage of 400 volts.
- Required number of LEDs. The more LEDs, the brighter the lamp will shine. It is important to consider the size of the room in which the lamp will be located.
- Glue for fixing LEDs. The LEDs are attached to the main lamp using heat-resistant glue. All work must be done very carefully.
It doesn’t take much time to turn an energy-saving lamp into an LED one. Everything can be done within 30 minutes. As a result, you will receive a bright and economical lamp and will be able to repair your broken product, which you no longer use. All actions must be performed carefully and slowly in order for the work to be of the highest quality.
Due to low energy consumption, theoretical durability and lower prices, incandescent and energy-saving lamps are rapidly replacing them. But, despite the declared service life of up to 25 years, they often burn out without even serving the warranty period.
Unlike incandescent lamps, 90% of burnt-out LED lamps can be successfully repaired with your own hands, even without special training. The examples presented will help you repair failed LED lamps.
Before you start repairing an LED lamp, you need to understand its structure. Regardless of the appearance and type of LEDs used, all LED lamps, including filament bulbs, are designed the same. If you remove the walls of the lamp body, you can see the driver inside, which is a printed circuit board with radio elements installed on it.
Any LED lamp is designed 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 supplied to the driver input. From the driver supply voltage DC supplied to the board on which the LEDs are soldered.
The driver is an electronic unit - a current generator that converts the supply voltage into the current required to light the LEDs.
Sometimes, to diffuse light or protect against human contact with unprotected conductors of a board with LEDs, it is covered with diffusing protective glass.
About filament lamps
By appearance A filament lamp is similar to an incandescent lamp. The design of filament lamps differs from LED lamps in that they do not use a board with LEDs as light emitters, but a sealed glass flask 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 attached 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 believe that over time they will replace all other artificial light sources.
Examples of LED lamp repairs
Attention, the electrical circuits of LED lamp drivers are galvanically connected to the phase of the electrical network and therefore care should be taken. Touching exposed parts of a circuit connected to an electrical outlet may result in electric shock.
LED lamp repair
ASD LED-A60, 11 W on SM2082 chip
Currently, powerful LED light bulbs have appeared, the drivers of which are assembled on SM2082 type chips. One of them worked for less than a year and ended up being repaired. The light went out randomly and came on again. When you tapped it, it responded with light or extinguishing. It became obvious that the problem was poor contact.
To get to the electronic part of the lamp, you need to use a knife to pick up the diffuser glass at the point of contact with the body. Sometimes it is difficult to separate the glass, since when it is seated, silicone is applied to the fixing ring.
After removing the light-scattering glass, access to the LEDs and the SM2082 current generator microcircuit became available. In this lamp, one part of the driver was mounted on an aluminum LED printed circuit board, and the second on a separate one.
An external inspection did not reveal any defective soldering or broken tracks. I had to remove the board with LEDs. To do this, the silicone was first cut off and the board was pryed off by the edge with a screwdriver blade.
To get to the driver located in the lamp body, I had to unsolder it by heating two contacts with a soldering iron at the same time and moving it to the right.
On the one side printed circuit board In the driver, only an electrolytic capacitor with a capacity of 6.8 μF for a voltage of 400 V was installed.
A diode bridge and two series-connected resistors with a nominal value of 510 kOhm were installed on the reverse side of the driver board.
In order to figure out which of the boards the contact was missing, we had to connect them, observing the polarity, using two wires. After tapping the boards with the handle of a screwdriver, it became obvious that the fault lies in the board with the capacitor or in the contacts of the wires coming from the base of the LED lamp.
Since the soldering did not raise any suspicions, I first checked the reliability of the contact in the central terminal of the base. It can be easily removed if you pry 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 use a soldering iron to solder the soldering wires coming from the base. When I touched one of the soldering joints, the wire became exposed. A “cold” solder was detected. Since there was no way to get to the wire to strip it, I had to lubricate it with FIM active flux and then solder it again.
Once assembled, the LED lamp consistently emitted light despite being hit with the handle of a screwdriver. Examination luminous flux on pulsations showed that they are significant with a frequency of 100 Hz. Such an LED lamp can only be installed in luminaires for general lighting.
Driver circuit diagram
LED lamp ASD LED-A60 on SM2082 chip
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 supplied through fuse F to the rectifier diode bridge assembled on the MB6S microassembly. Electrolytic capacitor C1 smoothes out ripples, and R1 serves to discharge it when the power is turned off.
From the positive terminal of the capacitor, the supply voltage is supplied directly to the LEDs connected in series. From the output of the last LED, the voltage is supplied to the input (pin 1) of the SM2082 microcircuit, the current in the microcircuit is stabilized and then from its output (pin 2) goes to the negative terminal of capacitor C1.
Resistor R2 sets the amount of current flowing through the HL LEDs. The magnitude of the current is inversely proportional to its rating. If the value of the resistor is decreased, the current will increase; if the value is increased, the current will decrease. The SM2082 microcircuit allows you to adjust the current value with a resistor from 5 to 60 mA.
LED lamp repair
ASD LED-A60, 11 W, 220 V, E27
Another ASD LED-A60 LED lamp was repaired, similar in appearance and with the same technical characteristics, as above, renovated.
When turned on, the lamp came on for a moment and then did not shine. This behavior of LED lamps is usually associated with a driver failure. So I immediately started disassembling the lamp.
The light-diffusing glass was removed with great difficulty, since along the entire line of contact with the body it was, despite the presence of a retainer, generously lubricated with silicone. To separate the glass, I had to look for a pliable place along the entire line of contact with the body using 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 along the contour into the aluminum insert. Despite the fact that the board was aluminum and could be removed without fear of cracks, all attempts were unsuccessful. The board held tight.
It was also not possible to remove the board together with the aluminum insert, since it fit tightly to the case and was seated with the outer surface on silicone.
I decided to try removing the driver board from the base side. To do this, first, a knife was pryed 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 flange so that the core points would disengage from the base.
The driver became accessible and was freely extended to a certain position, but it was not possible to remove it completely, although the conductors from the LED board were sealed off.
The LED board had a hole in the center. I decided to try to remove the driver board by hitting its end through a metal rod threaded through this hole. The board moved a few centimeters and hit 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 whose shoulders rested against the lamp body. It looks like the board was shaped this way to limit movement, although it would have been enough to fix it with a drop of silicone. Then the driver would be removed from either side of the lamp.
The 220 V voltage from the lamp base is supplied through a resistor - fuse FU to the MB6F rectifier bridge and is then smoothed out 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 pins 1 and 8 MS set the amount of LED supply current.
The photo shows a typical electrical circuit diagram provided by the manufacturer of the SIC9553 chip in the Chinese datasheet.
This photo shows the appearance of the LED lamp driver from the installation side of the output elements. Since space allowed, to reduce the pulsation coefficient of the light flux, the capacitor at the driver output was soldered to 6.8 μF instead of 4.7 μF.
If you have to remove the drivers from the body of this lamp model and cannot remove the LED board, you can use a jigsaw to cut the lamp body around the circumference just above the screw part of the base.
In the end, all my efforts to extract the driver turned out to be useful only in understanding the structure of the LED lamp. The driver turned out to be OK.
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. It was necessary to ring the LEDs first.
An attempt to test the LEDs with a multimeter was unsuccessful. The LEDs did not light up. It turned out that two light-emitting crystals connected in series 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 turned on in resistance measurement mode produces a voltage within 3-4 V. I had to check the LEDs using a power supply, supplying 12 V to each LED through a 1 kOhm current-limiting resistor.
There was no replacement LED available, so the pads were shorted with a drop of solder instead. This is safe for driver operation, and the power of the LED lamp will decrease by only 0.7 W, which is almost imperceptible.
After repairing the electrical part of the LED lamp, the cracked body was glued together with quick-drying “Moment” superglue, the seams were smoothed by melting the plastic with a soldering iron and smoothed with sandpaper.
Just for fun, I did 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 was 0.46 W. With 16 LEDs, the result is 7.36 W, instead of the declared 11 W. Perhaps the manufacturer has indicated the total power consumption of the lamp, taking into account losses in the driver.
The service life of the ASD LED-A60, 11 W, 220 V, E27 LED lamp declared by the manufacturer raises serious doubts in my mind. In the small volume of the plastic lamp body, with low thermal conductivity, significant power is released - 11 W. As a result, the LEDs and the driver operate at the maximum permissible temperature, which leads to accelerated degradation of their crystals and, as a consequence, to a sharp reduction in their time between failures.
LED lamp repair
LED smd B35 827 ERA, 7 W on BP2831A chip
An acquaintance shared with me that he bought five light bulbs like in the photo below, and after a month they all stopped working. He managed to throw away three of them, and, at my request, brought two for repairs.
The light bulb worked, but instead of bright light it emitted a flickering weak light with a frequency of several times per second. I immediately assumed that the electrolytic capacitor had swollen; usually, if it fails, the lamp begins to emit light like a strobe.
The light-scattering glass came off easily and was not glued. It was fixed by a slot on its rim and a protrusion in the lamp body.
The driver was secured using two solders to a printed circuit board with LEDs, as in one of the lamps described above.
A typical driver circuit on the BP2831A chip taken from the datasheet is shown in the photograph. The driver board was removed and all simple radio elements were checked; they all turned out to be in good order. I had to start checking the LEDs.
The LEDs in the lamp were installed of an unknown type with two crystals in the housing and inspection did not reveal any defects. By connecting the leads of each LED in series, I quickly identified the faulty one and replaced it with a drop of solder, as in the photo.
The light bulb worked for a week and was repaired again. Shorted the next LED. A week later I had to short-circuit another LED, and after the fourth I threw out the light bulb because I was tired of repairing it.
Reason for light bulb failure similar design obvious. LEDs overheat due to insufficient heat sink surface, and their service life is reduced to hundreds of hours.
Why is it permissible to short-circuit the terminals of burnt-out LEDs in LED lamps?
The LED lamp driver, unlike a constant voltage power supply, produces a stabilized current value at the output, not a voltage. Therefore, regardless of the load resistance within the specified limits, the current will always be constant and, therefore, the voltage drop across each of the LEDs will remain the same.
Therefore, as the number of series-connected LEDs in the circuit decreases, the voltage at the driver output will also decrease proportionally.
For example, if 50 LEDs are connected in series to the driver, and each of them drops a voltage of 3 V, then the voltage at the driver output is 150 V, and if you short-circuit 5 of them, the voltage will drop to 135 V, and the current will not change.
But the efficiency of a driver assembled according to this scheme will be low and power losses will be more than 50%. For example, for an LED light bulb MR-16-2835-F27 you will need a 6.1 kOhm resistor with a power of 4 watts. It turns out that the resistor driver will consume power that exceeds the power consumption of LEDs and placing it in a small LED lamp housing, due to the release of more heat, will be unacceptable.
But if there is no other way to repair an LED lamp and it is very necessary, then the resistor driver can be placed in a separate housing; anyway, the power consumption of such an LED lamp will be four times less than incandescent lamps. It should be noted that the more LEDs connected in series in a light bulb, the higher the efficiency will be. With 80 series-connected SMD3528 LEDs, you will need an 800 Ohm resistor with a power of only 0.5 W. The capacitance of 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 blackening of the entire surface of the LED, then it is definitely faulty.
When inspecting the appearance of the LEDs, you need to carefully examine the quality of the soldering of their terminals. One of the light bulbs being repaired turned out to have four LEDs that were poorly soldered.
The photo shows a light bulb that had very small black dots on its four LEDs. I immediately marked the faulty LEDs with crosses so that they were clearly visible.
Faulty LEDs may not have any changes in appearance. Therefore, it is necessary to check each LED with a multimeter or pointer tester turned on in resistance measurement mode.
There are LED lamps in which standard LEDs are installed in appearance, in the housing of which two crystals connected in series are mounted at once. For example, lamps of the ASD LED-A60 series. To test such LEDs, it is necessary to apply a voltage of more than 6 V to its terminals, and any multimeter produces no more than 4 V. Therefore, checking such LEDs can only be done by applying a voltage of more than 6 (recommended 9-12) V to them from the power source through a 1 kOhm resistor .
The LED is checked like a regular diode; in one direction the resistance should be equal to tens of megaohms, and if you swap the probes (this changes the polarity of the voltage supply to the LED), then it should be small, and the LED may glow dimly.
When checking and replacing LEDs, the lamp must be fixed. To do this, you can use a suitable sized round jar.
You can check the serviceability of the LED without an additional DC source. But this verification method is possible if the light bulb driver is working properly. To do this, it is necessary to apply supply voltage to the base of the LED light bulb and short-circuit the terminals of each LED in series with each other using a wire jumper or, for example, the jaws of metal tweezers.
If suddenly all the LEDs light up, it means that the shorted one is definitely faulty. This method is suitable if only one LED in the circuit is faulty. With this method of checking, it is necessary to take into account that if the driver does not provide galvanic isolation from the electrical network, as for example in the diagrams above, then touching the LED solders with your hand is unsafe.
If one or even several LEDs turn out to be faulty and there is nothing to replace them with, then you can simply short-circuit the contact 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 checking the LEDs showed their serviceability, then the reason for the light bulb’s inoperability lies in the driver or in the soldering areas of the current-carrying conductors.
For example, in this light bulb a cold solder connection was found on the conductor supplying power to the printed circuit board. The soot released due to poor soldering even settled on the conductive paths 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. I was lucky with the repair of this light bulb.
Of the ten failed bulbs, only one had a faulty driver and a broken diode bridge. The driver repair consisted of 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. The LED from the donor board also needs to be desoldered for replacement without damage.
It is almost impossible to desolder SMD LEDs with a simple soldering iron without damaging their housing. But if you use a special tip for a soldering iron or put an attachment made of copper wire on a standard tip, then the problem can be easily solved.
LEDs have polarity and when replacing, you need to install it correctly on the printed circuit board. Typically, printed conductors follow the shape of the leads on the LED. Therefore, a mistake can only be made if you are inattentive. To seal an LED, it is enough to install it on a printed circuit board and heat its ends with the contact pads with a 10-15 W soldering iron.
If the LED burns out like carbon, and the printed circuit board underneath is charred, then before installing a new LED, you must clean this area of the printed circuit board from burning, since it is a current conductor. When cleaning, you may find that the LED solder pads are burnt or peeled off.
In this case, the LED can be installed by soldering it to adjacent LEDs if the printed traces lead to them. To do this, you can take a piece of thin wire, bend it in half or three times, depending on the distance between the LEDs, tin it and solder it to them.
Repair of LED lamp series "LL-CORN" (corn lamp)
E27 4.6W 36x5050SMD
The design of the lamp, which is popularly called a corn lamp, shown in the photo below is different 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, since there is access to test the LEDs and replace them without disassembling the lamp body. True, I still disassembled the light bulb for fun in order to study its structure.
Examination LEDs The corn lamp is no different from the technology described above, but we must take into account that the SMD5050 LED housing contains three LEDs at once, usually connected in parallel (three dark dots of the crystals are visible on the yellow circle), and when checked, all three should light up.
A faulty LED can be replaced with a new one or short-circuited with a jumper. This will not affect the reliability of the lamp, only the luminous flux will decrease slightly, unnoticeably to the eye.
The driver of this lamp is assembled according to the simplest circuit, without an isolating transformer, so touching the LED terminals when the lamp is on is unacceptable. Lamps of this design must not be installed in lamps that can be reached by children.
If all the LEDs are working, it means the driver is faulty, and the lamp will have to be disassembled to get to it.
To do this, you need to remove the rim from the side opposite the base. Using a small screwdriver or a knife blade, try in a circle to find the weak spot where the rim is glued the worst. If the rim gives way, then using the tool as a lever, the rim will easily come off around the entire perimeter.
The driver was compiled using electrical diagram, 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 going from the driver to the lamp base were long, the driver was easily removed from the lamp body. After studying its circuit diagram, the driver was inserted back into the housing, and the bezel was glued into place with transparent Moment glue. The failed LED was replaced with a working 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, we had to open the lamp using the technology described above.
This lamp gave me a surprise. The wires leading from the driver to the socket were short, and it was impossible to remove the driver from the lamp body for repair. I had to remove the base.
The lamp base was made of aluminum, cored around the circumference and held tightly. I had to drill out the mounting points with a 1.5 mm drill. After this, the base, pryed off with a knife, was easily removed.
But you can do without drilling the base if you use the edge of a knife to pry it around the circumference and slightly bend its upper edge. You should first put a mark on the base and body so that the base can be conveniently installed in place. To securely fasten 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 the old places. Next, press 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 pulse surges and R2, R3 for protection against current surges. When checking the elements, resistors R2 were immediately found to be open on both drivers. It appears that the LED lamp was supplied with a voltage that exceeded the permissible voltage. After replacing the resistors, I didn’t have a 10 ohm one at hand, so I set it to 5.1 ohms, and the lamp started working.
Repair of LED lamp series "LLB" LR-EW5N-5
The appearance of this type of light bulb inspires confidence. Aluminum body, high quality workmanship, beautiful design.
The design of the light bulb is such that disassembling it without the use of significant physical effort is impossible. Since the repair of any LED lamp begins with checking the serviceability of the LEDs, the first thing we had to do was remove the plastic safety glass.
The glass was fixed without glue on a groove made in the radiator with a collar inside it. To remove the glass, you need to use the end of a screwdriver, which will go between the fins of the radiator, to lean on the end of the radiator and, like a lever, lift the glass up.
Checking the LEDs with a tester showed that they are working properly, therefore, the driver is faulty and we need to get to it. The aluminum board was secured with four screws, which I unscrewed.
But contrary to expectations, behind the board there was a radiator plane, lubricated with heat-conducting paste. The board had to be returned to its place and the lamp continued to be disassembled from the base side.
Due to the fact that the plastic part to which the radiator was attached was held very tightly, I decided to go the proven route, remove the base and remove the driver through the opened hole for repair. I drilled out the core points, but the base was not removed. It turned out that it was still attached to the plastic due to the threaded connection.
I had to separate the plastic adapter from the radiator. It held up just like the protective glass. To do this, a cut was made with a hacksaw for metal 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 unsoldering the leads from the LED printed circuit board, 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 an SS110 Schottky diode on the board, which was replaced with an 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 light came on. The second light bulb had the same problem.
Repair of 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 slightly different.
If you look closely, you can see that at the junction between the aluminum radiator and the spherical glass, unlike the LR-EW5N-5, there is a ring in which the glass is secured. To remove the protective glass, just use a small screwdriver to pick it up at the junction with the ring.
Three nine crystal super-bright LEDs are installed on an aluminum printed circuit board. The board is screwed to the heatsink with three screws. Checking the LEDs showed their serviceability. Therefore, the driver needs to be repaired. Having experience in repairing a similar LED lamp "LLB" LR-EW5N-5, I did not unscrew the screws, but unsoldered the current-carrying wires coming from the driver and continued disassembling the lamp from the base side.
The plastic connecting ring between the base and 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 was easily removed from the lamp body.
The screws that fasten the plastic ring of the base are covered by the driver and are difficult to see, but they are on the same axis with the thread to which the adapter part of the radiator is screwed. Therefore, you can reach them with a thin Phillips screwdriver.
The driver turned out to be assembled according to a transformer circuit. Checking all elements except the microcircuit did not reveal any failures. Consequently, the microcircuit is faulty; I couldn’t even find a mention of its type on the Internet. The LED light bulb could not be repaired; it will be useful for spare parts. But I studied its structure.
Repair of LED lamp series "LL" GU10-3W
At first glance, it turned out to be impossible to disassemble a burnt-out GU10-3W LED light bulb with protective glass. An attempt to remove the glass resulted in its chipping. When great force was applied, the glass cracked.
By the way, in the lamp marking, 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 light bulbs with a GU10 base have special pins and are installed in a socket with a rotation. Thanks to the expanding pins, the LED lamp is pinched in the socket and 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 you don’t have a drill at hand, you can make a hole with a thick awl.
Next, a small screwdriver is inserted into the hole and, acting like a lever, the glass is lifted. I removed the glass from two light bulbs without any problems. If checking the LEDs with a tester shows their serviceability, then the printed circuit board is removed.
After separating the board from the lamp body, it immediately became obvious that the current-limiting resistors had burned out in both one and the other lamp. The calculator determined their nominal value from the stripes, 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 operates at the maximum ambient temperature.
The driver circuit board was well filled with silicone, and I did not disconnect it from the board with the LEDs. I cut off the leads of the burnt resistors at the base and soldered them to more powerful resistors that were on hand. In one lamp I soldered a 150 Ohm resistor with a power of 1 W, in the second two in parallel with 320 Ohms with a power of 0.5 W.
In order to prevent accidental contact of the resistor terminal, to which the mains voltage is connected, 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 in different colors, from transparent to black. It melts, depending on the brand, at a temperature of 80-150°, which allows it to be melted using an electric soldering iron. It is enough to cut a piece of the rod, place it in the right place and heat it. Hot-melt glue will acquire the consistency of May honey. After cooling it becomes hard again. When reheated it becomes liquid again.
After replacing the resistors, the functionality of both bulbs was restored. All that remains is to secure the printed circuit board and protective glass in the lamp body.
When repairing LED lamps, I used liquid nails “Mounting” to secure printed circuit boards and plastic parts. The glue is odorless, adheres well to the surfaces of any materials, remains plastic after drying, and 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, since the wires were pushing it out, I additionally fixed the board at several points using hot glue.
The LED lamp began to flash like a strobe light
I had to repair a couple of LED lamps with drivers assembled on a microcircuit, the fault of which was that the light blinked at a frequency of about one hertz, like in a strobe light.
One instance of the LED lamp began to blink immediately after being turned on for the first few seconds and then the lamp began to shine normally. Over time, the duration of the lamp's blinking after switching on began to increase, and the lamp began to blink continuously. The second instance of the LED lamp suddenly began blinking continuously.
After disassembling the lamps, it turned out that the electrolytic capacitors installed immediately after the rectifier bridges in the drivers had failed. It was easy to determine the malfunction, since the capacitor housings were swollen. But even if the capacitor looks free of external defects in appearance, it is still a repair LED light bulb with a stroboscopic effect, you need to start by replacing it.
After replacing the electrolytic capacitors with working ones, the stroboscopic effect disappeared and the lamps began to shine normally.
Online calculators for determining resistor values
by color marking
When repairing LED lamps, it becomes necessary to determine the resistor value. According to the standard, modern resistors are marked by applying colored rings to their bodies. 4 colored rings are applied to simple resistors, and 5 to high-precision resistors.
I bought 10 W 900 lm warm white LEDs on AliExpress to try. The price in November 2015 was 23 rubles per piece. The order arrived in a standard bag, I checked everything was in good order. 
To power LEDs in lighting devices, special units are used - electronic drivers, which are converters that stabilize the current rather than the voltage at their output. But since the drivers for them (I also ordered on AliExpreess) were still on the way, I decided to power them from ballast from energy-saving lamps. I've had several of these faulty lamps. whose filament in the bulb burned out. As a rule, the voltage converter for such lamps is working properly, and it can be used as a switching power supply or LED driver.
We disassemble the fluorescent lamp. 
For the conversion, I took a 20 W lamp, the choke of which can easily deliver 20 W to the load. For a 10W LED, no further modifications are required. If you plan to power a more powerful LED, you need to take a converter from a more powerful lamp, or install a choke with a larger core.
Installed jumpers in the lamp ignition circuit. 
I wound 18 turns of enamel wire around the inductor, solder the terminals of the wound winding to the diode bridge, apply mains voltage to the lamp and measure the output voltage. In my case, the unit produced 9.7V. I connected the LED through an ammeter, which showed a current passing through the LED of 0.83A. My LED has an operating current of 900mA, but I reduced the current to increase the resource. I assembled the diode bridge on the board using a hinged method.
Remodeling scheme. 
I installed the LED using thermal paste on a metal lampshade of an old table lamp. 
I installed the power board and diode bridge into the body of a table lamp. 
When working for about an hour, the LED temperature is 40 degrees. 
To the eye, the illumination is like that of a 100-watt incandescent lamp. 
