Do-it-yourself electronic equipment repair. Troubleshooting electronic circuits

IN modern world A person is surrounded by a huge number of electrical and electronic devices. Along with the undeniable advantages of such useful inventions of the human mind, we get one big minus - expensive repairs. AND personal computer, and a laptop, and a DVD player, and satellite receiver- These are complex electronic devices, the cost of repairs of which can reach several thousand rubles. Sometimes these amounts that we pay for repairs to an electronics technician are unreasonably high. But fortunately, we have the power to learn basic diagnostic techniques, as well as simple repairs that can be done at home. This article will discuss typical breakdowns of the most common electronics, as well as ways to quickly troubleshoot problems with minimal expenditure of money and nerves.

To repair electronics yourself, you don’t have to be an ace in this matter, but certain knowledge of a school physics course is still necessary. It’s good if you attended a radio engineering club at school. If you want to repair electronics, then such concepts as electrical resistance, current, emf, inductance, capacitance should not be unclear to you. Some experience in soldering radio components is required, as well as minimal skills in using an electrical tester or multimeter.

What kind of damage can you fix yourself?

Some beginners mistakenly believe that a personal computer can only be repaired under conditions service center. Practice shows that most breakdowns can be fixed at home using simple equipment. But it’s worth making a reservation that replacing any microcircuit with motherboard You most likely won't be able to use a computer. Although you can replace electrolytic capacitors on the same motherboard at home, armed with some simple soldering iron. Therefore, you should immediately understand which breakdowns you can fix yourself, and which ones you can only fix in the service.

How to fix an electronic device that won't turn on

If you plug the device into a 220V power supply, but there is no reaction: there is no light or sound indication of operation, then most likely the power supply has stopped working. We recommend connecting any device that does not respond adequately when plugged into the network in series with a powerful incandescent lamp so as not to cause a short circuit. If the switching power supply of the device is working, then the incandescent lamp will not light up, but if there is a short circuit on the input of the unit, then the incandescent lamp will perform a protective function and will burn at full intensity.

How to check a switching power supply

In fact, the switching power supply has an almost standard design in many electrical devices. First, we check it for the most commonplace possible breakdowns - broken network cables and blown fuses. You can significantly speed up diagnostics if you measure the voltage across the largest capacitor in the switching power supply. As a rule, it is installed after the diode assembly and after the surge protector. If it has approximately 300V DC voltage, then you will automatically know that both the fuse and the power filter, and network cable, and the input chokes are fully operational. There are blocks where instead of one huge 400V capacitor there are two. In such blocks, the voltage on each capacitor is approximately 150V. If there is no voltage, then it is best to check everything separately: ring the network cable, check each rectifier diode, fuse, capacitors, chokes, etc. Moreover, fuses can be very insidious: outwardly they look quite serviceable, but when tested they have an infinitely high resistance. This is due to the fact that in fuses, a break or burnout can occur in a place that is not at all visible.

Electrolytic capacitors are the weakest point of modern switching power supplies. A decrease in capacity and an increase in the ESR value leads either to a complete failure of the power supply unit or to a violation of the output voltage parameters. All swollen capacitors must be replaced. Also, take the time to check the ESR parameter, as well as the capacitance value of all suspicious capacitors. The compact device ESR-micro v4.0s copes best with this task. Fortunately, capacitors are not expensive, so you can simply replace any suspect capacitors with known good ones. The reliability and quality of repairs will only benefit from this. The main thing to remember is that electrolytic capacitors have polarity, therefore, they must be soldered strictly according to the loop. After replacing the capacitors, most units begin to operate normally, unless, of course, there are problems with PWM chips, diodes, output stabilization circuits, etc.

How to find a short circuit if the power supply goes into protection mode

It happens that a switching power supply starts to work normally only when disconnected from the main board. For example, the computer power supply turns on only when it is disconnected from the motherboard and “started up” using a jumper that connects the green and black wires. To find a place or radio element that provokes a short circuit, you need to spend a lot of time. To simplify this task as much as possible, we recommend applying a current-limiting constant voltage from a laboratory power supply to the problem line in the motherboard. Using touch, as well as using fax paper, we find the area where there is the highest heating. Therefore, this is where the faulty element is located. Finding and fixing the problem takes no more than 15 minutes.

How to fix a device that turns on but does not work correctly

The most difficult problem is a fault that appears and disappears. The sudden nature of the occurrence and the inexplicability of the disappearance of a malfunction of electronic equipment can baffle even an experienced technician. If you notice that your computer suddenly turns off after several hours of playing, but after waiting 20-30 minutes, it is ready to work again, then you should look for a malfunction in the thermal regime, as well as in broken contacts. First of all, check which microcircuits or radio components are particularly hot. If you do not have a special temperature probe, you can simply measure the temperature by touch. Insufficient cooling, dried thermal paste, dust - these are the main causes of overheating, leading to unstable operation.

Today we will discuss radios. Look at YouTube for a video about an old car radio made in 1960 from the Volga; modern foreign semiconductor equivalents differ only in their elemental base. Lamp technology is good, giving a person an idea of ​​​​the principle of operation of the device. Repairing a radio receiver with your own hands turns into a useless, hopeless task if the technician is unable to understand the steps. A person is not so surprised that dental crowns serve as a detector of a strong radio signal with a column in the ear in the form of an anvil, if they are aware of the concept of amplitude modulation, they serve as the basis for supplying information to an analogue broadcasting channel of a station. Without insight into the circuitry of a typical radio receiver, the text would turn into reading material for specialists with a narrow focus, without being of interest to a wide range of readers.

The structure of a typical radio receiver

The receiver catches the wave and amplifies it. Extracts useful information and sends it to the speaker. Designs are created according to the criteria:

• economic feasibility;
• quality;
• reliability.

Resonant circuit of a radio receiver

The radio receiver begins with an input stage that is tuned to the desired wavelength. The antenna is considered a relatively broadband device; it picks up a large number of channels. In order to find what you need among the mess, you need some kind of gate that allows the useful signal to pass through. The resonant circuits will serve as the portal. The theory is not important, readers will benefit from knowing the following facts:

1. The resonant circuit transmits a narrow section from the mass of the spectrum, the width of which is adjusted to the band occupied by the channel. For example, with amplitude modulation 10 kHz, approximately. The level of characteristics at level 0.7 of the normalized graph demonstrates the indicated size along the horizontal axis. The shape of the amplitude-frequency response is determined by the type of circuit.
2. In the simplest case, a resonant circuit is formed by inductance and capacitance connected in parallel. Not the only option. The circuit is adjusted to the frequency using varicaps (a capacitor with variable capacitance). Rough channel selection is performed using a mechanical switch and transistor switches. The resonant circuits of LW, MW, VHF are different in physical terms; none of them can be adjusted to all ranges by changing the capacitance of the varicap.
3. The resonant circuit is considered a passive element that does not carry a large electrical load and rarely breaks down. Let's trace the breakdown simply:

• Only one range stopped working, the problem is here, before the mixer (read below about the amplifier high frequency);
• if, on the contrary, only one range works, the switch is broken: mechanics, transistor switch.

The difficulty is the same: the high-frequency output voltage of the resonant circuits can hardly be measured; a typical multimeter is not designed for such an application.

The radio frequency (high frequency) amplifier is fitted with a shield, reducing losses

Radio high frequency amplifier

A high-frequency amplifier increases the amplitude of the incoming signal to a level normal operation mixer The original frequency travels along the path, the wave differs by an order of magnitude for DV and VHF; it is impossible to create an electronic circuit for a radio receiver on a single transistor or microcircuit. It is customary to divide the input stages for FM and other frequencies. However, this applies to old models and modern ones. The high-frequency amplifier is not recognized as a selective circuit - a broadband device. It's easy to explain. If a section of the radio receiver path contained filters, the cascades would need to be rebuilt in parallel with the input resonant circuits. Makes design difficult electrical diagram.

Mixer, radio intermediate frequency amplifier

For normal operation of the detector, it is necessary to receive a signal of a fixed frequency. For FM – 10.9 MHz (frequency modulation), for LW, MW – 450 kHz (amplitude modulation). The input wave is mixed with the frequency of the local oscillator (high frequency reference oscillator), the output gives the difference, the values ​​​​are indicated above. The local oscillator and mixer will essentially become amplifiers on a transistor or microcircuit, the first one is configured with a generation mode, the second one operates in a linear mode. The receiver is built on cascades of this type. This includes the considered high-frequency amplifiers and intermediate-frequency amplifiers, which we will discuss below.

Radio detector

Following frequency stabilization, the radio receiver extracts useful information from the broadcast station from it. Carried out in detectors. Both cascades are built on diodes, transistors, microcircuits, the difference is in the use of oscillations. With amplitude modulation useful information is determined by the voltage range. Consequently, the simplest diode cuts off the negative part, the envelope is obtained after filtering by an RC circuit. This is how a simple amplitude detector works. The frequency option is organized, for example, by a discriminator. A device whose peak amplitude-frequency response occurs at resonance (10.9 MHz) declines towards the edges. The result is a useful signal.

To avoid distortions and signal distortion, it must be 100% symmetrical with respect to the carrier. In reality, the vehicle is moving, the Doppler effect, and other nuances shift the signal. Automatic frequency adjustment comes into play. The cascade acts on resonant circuits, local oscillators, keeping reception normal. The operating principle is based on assessing the symmetry of the incoming signal. The spectrum is reflected specularly from the carrier (in both directions). There are exceptions with one sideband; it is rarely used in consumer radios.

To save transmitter energy, the carrier is often cut off, leaving a pilot signal; this is usually not done for peaceful purposes; the design of the receiver becomes more complicated. The method is progressive, points to the future. The receiver restores the carrier, the missing part of the spectrum according to the rule indicated above.

Radio low frequency amplifier

The low frequency amplifier is the responsible part, low speech and music are not needed by customers. The radio cascade is easy to find; here are located powerful chips, transistors equipped with hefty aluminum radiators. Regardless of the elemental base, you can achieve a screaming radio receiver by spending power; a certain part is dissipated by heat. Overheating is blocked by radiators.

Important! Germanium is afraid of temperatures above 80 degrees Celsius. Semiconductor p-n junctions have advantageous characteristics. It is necessary to cool the power elements with radiators.

Radios have two or more channels. In case of stereo reception. The division of channels into right and left is common in broadcasting with frequency modulation, VHF range, including FM. The method of encrypting information is different, it doesn’t matter when it’s time to independently repair radios. The low-frequency amplifier is a common cascade, where information is supplied immediately from the amplitude detector, and from the frequency detector - through a circuit for determining the presence of stereo.

Radio repair

IN general case it is necessary to split the radio receiver into cascades. The purpose of the circuits was described. We forgot power supplies for a reason, we discussed the topic with reviews. Tube radios require a larger number of ratings. The cathodes of the lamps are heated with an alternating voltage of 6.3 V. By the way, the performance of the cascades can be assessed by the glow of the electrodes in the dark. You need to wait until the radio warms up, then check for reddish reflections by turning off the light. You can easily understand the location of the breakdown. The bulbs of burnt lamps turn black. They can glow in a completely ordinary style. Repair tube radio simpler than the modern one.

The device is visually divided into logical parts; the fault can be roughly localized. The radio receiver device often contains control contacts; where to find the information is another matter. We believe that if desired, information can be found on a specialized forum or in a technical library. Nowadays it is not customary, remembering the good old days, to supply a radio receiver with a detailed electrical circuit, everyone who knows how to do it. In the case of hybrid electronics, the device may be a single microcircuit, the low-frequency amplifier is separate. We'll have to find a new radio.

In other cases, you can repair transistor radios or repair tube radios. Stop discounting the latter. Musicians still prefer tube amplifiers.

So, self-repair of the radio is carried out according to the indicated scheme:

1. Disassembly of the device to assess the internal condition, inspection.
2. Dividing an electrical circuit into logical parts.
3. Search for documentation for the radio receiver using available channels.
4. Survey of radio amateurs on forums on the subject.

We are talking about old devices - first of all we clean off the dust, look at the installation, check the tracks. If a light tap on the device results in a crackling sound from the radio speakers, the issue is a broken contact. Solder cracks, peeling of tracks, breaks - to be eliminated, take the trouble to re-check the functionality. Soviet-era car radios use an inverter, the noise of which you will hear after turning it on. Repairing old radios is useful for beginners, allowing them to learn how to handle the equipment. Masters practice every day. They study the types of radios and repair methods.

In the life of every home craftsman who knows how to hold a soldering iron and use a multimeter, there comes a time when some complex electronic equipment breaks down and he is faced with a choice: send it to a service center for repairs or try to repair it himself. In this article we will look at techniques that can help him with this.

So, your equipment is broken, for example an LCD TV, where should you start repairing it? All craftsmen know that it is necessary to start repairs not with measurements, or even immediately resolder the part that aroused suspicion of something, but with external examination. This includes not only examining the appearance of the TV circuit boards, removing its cover, looking for burnt radio components, and listening to hear a high-frequency squeak or click.

We connect the device to the network

To begin with, you just need to turn on the TV to the network and see: how it behaves after turning it on, whether it responds to the power button, or the standby mode LED is blinking, or the image appears for a few seconds and disappears, or there is an image but there is no sound, or vice versa. Based on all these signs, you can obtain information from which you can build upon for further repairs. For example, by blinking an LED at a certain frequency, you can set a fault code, self-testing of the TV.

TV error codes by LED blinking

After the signs have been established, you should look for a schematic diagram of the device, or better yet, if a Service manual for the device has been issued, documentation with a diagram and a list of parts, on special websites dedicated to electronics repair. It will also not be amiss in the future to enter the full name of the model into the search engine, with brief description breakdown, conveying in a few words its meaning.

Service manual

True, sometimes it is better to search for a diagram by the device chassis, or the name of the board, for example a TV power supply. But what if you still couldn’t find the circuit, and you are not familiar with the circuitry of this device?

Block diagram of LCD TV

In this case, you can try to ask for help from specialized specialists, after conducting a preliminary diagnosis yourself, in order to collect information from which the specialists helping you can build on. What stages does this preliminary diagnosis include? First, you must make sure that power is supplied to the board if the device does not show any signs of life at all. This may seem trivial, but it wouldn’t hurt to test the power cord for integrity using the audio test mode. how to use a regular multimeter.

Tester in audio mode

Then the fuse is tested in the same multimeter mode. If everything is fine here, we should measure the voltage at the power connectors going to the TV control board. Typically, the supply voltages present on the connector pins are labeled next to the connector on the board.

TV control board power connector

So, we measured and there is no voltage at the connector - this indicates that the circuit is not functioning correctly, and we need to look for the reason for this. The most common cause of breakdowns found in LCD TVs are banal electrolytic capacitors, with high ESR, equivalent series resistance. About ESR.

Capacitor ESR Table

At the beginning of the article, I wrote about a squeak that you may hear, and so, its manifestation, in particular, is a consequence of the overestimated ESR of small-value capacitors located in the standby voltage circuits. To identify such capacitors, a special device is required, an ESR meter, or, in the latter case, the capacitors will have to be unsoldered for measurement. I posted a photo of my ESR meter that allows me to measure this parameter without soldering below.

My ESR meter

What to do if such devices are not available, and suspicion falls on these capacitors? Then you will need to consult on repair forums and clarify in which node, which part of the board, the capacitors should be replaced with ones that are known to work, and only new (!) capacitors from a radio store can be considered as such, because used ones have this parameter, ESR may also be off the charts or already on the verge.

Photo - swollen capacitor

The fact that you could unsolder them from a device that previously worked in in this case does not matter, since this parameter is important only for operation in high-frequency circuits; accordingly, earlier, in low-frequency circuits, in another device, this capacitor could function perfectly, but have an ESR parameter that was very high. The work is greatly facilitated by the fact that high-value capacitors have a notch in their upper part, along which, if they become unusable, they are simply opened, or a swelling forms, a characteristic sign of their unsuitability for anyone, even a novice master.

Multimeter in Ohmmeter mode

If you see blackened resistors, you will need to test them with a multimeter in ohmmeter mode. First, you should select the 2 MOhm mode; if the screen shows values ​​that differ from unity, or the measurement limit is exceeded, we should accordingly reduce the measurement limit on the multimeter to establish its more accurate value. If there is one on the screen, then most likely such a resistor is broken and should be replaced.

Color coding of resistors

If it is possible to read its denomination by the markings on its body, it’s good to otherwise You can't do without a diagram. If the circuit is available, then you need to look at its designation and set its rating and power. If the resistor is precision, its (precise) value can be set by connecting two ordinary resistors in series, a larger and a smaller value, the first we set the value roughly, the last we adjust the accuracy, and their total resistance will add up.

Transistors are different in the photo

Transistors, diodes and microcircuits: it is not always possible to determine the malfunction with them appearance. You will need to measure with a multimeter in audio testing mode. If the resistance of any of the legs, relative to some other leg, of one device, is zero, or close to it, in the range from zero to 20-30 Ohms, most likely such a part must be replaced. If it is a bipolar transistor, you need to call it according to the pinout, it p-n junction s.

Checking the transistor with a multimeter

Most often, such a check is enough to consider the transistor to be working. Better method. For diodes, we also cause a p-n junction, in the forward direction, there should be numbers of the order of 500-700 when measured, in the reverse direction one. The exception is Schottky diodes, they have a lower voltage drop, and when calling in the forward direction, the screen will show numbers in the range of 150-200, and in the reverse direction it will also be one. , field effect transistors, you can’t check this with a regular multimeter without soldering; you often have to consider them conditionally working if their terminals do not short-circuit with each other, or have low resistance.

Mosfet in SMD and regular housing

It should be taken into account that mosfets have a built-in diode between the Drain and the Source, and when dialing, the readings will be 600-1600. But there is one nuance here: if, for example, you call the mosfets on the motherboard and at the first touch you hear beep, do not rush to write the mosfet into the broken one. Its circuits contain electrolytic filter capacitors, which, when charging begins, are known to behave for some time as if the circuit were short-circuited.

Mosfets on PC motherboard

This is what our multimeter shows, in audible dialing mode, with a squeak for the first 2-3 seconds, and then increasing numbers will appear on the screen, and the unit will be set as the capacitors charge. By the way, for the same reason, in order to save the diodes of the diode bridge, a thermistor is installed in switching power supplies that limits the charging currents of electrolytic capacitors at the moment of switching on, through the diode bridge.

Diode assemblies on the diagram

Many acquaintances of novice repairmen who seek remote advice from VKontakte, it’s shocking - you tell them to ring the diode, they ring it and immediately say: it’s broken. Here, as a standard, an explanation always begins that you need to either lift, unsolder one leg of the diode, and repeat the measurement, or analyze the circuit and board for the presence of parallel-connected parts in low resistance. These are often the secondary windings of a pulse transformer, which are connected parallel to the terminals of the diode assembly, or in other words, a dual diode.

Parallel and series connection of resistors

Here it is best to remember once, the rule of such connections:

1. When two or more parts are connected in series, their total resistance will be greater than the greater resistance of each individually.
2. And with a parallel connection, the resistance will be less than the smaller of each part. Accordingly, our transformer winding, which has a resistance of 20-30 Ohms at best, by shunting, imitates for us a “broken” diode assembly.

Of course, unfortunately, it is impossible to reveal all the nuances of repairs in one article. For preliminary diagnosis of most breakdowns, as it turned out, a conventional multimeter used in the voltmeter, ohmmeter, and audio test modes is sufficient. Often, if you have experience, in the event of a simple breakdown and subsequent replacement of parts, the repair is completed, even without a diagram, carried out by the so-called “scientific poking method”. Which, of course, is not entirely correct, but as practice shows, it works, and, fortunately, not at all as shown in the picture above). Successful repairs to everyone, especially for the Radio Circuits website - AKV.

Discuss the article DIAGNOSTICS AND REPAIR OF ELECTRONICS WITHOUT DIAGRAMS

R section Workshop compiled for beginner radio amateurs who want not only to assemble and make homemade products, but also to independently repair household electronics.

Z here You will find articles on repairs, starting with devices such as CD/MP3 players and ending with household compact fluorescent lamps. You will learn how to properly disassemble/assemble a CD deck of a car player and how to restore the functionality of a portable audio speaker. The main points of the repair are also discussed and high-quality photographs are provided for clarity.

N and pages This section contains information on how to repair a DVD player and stereo system. We talk about such typical malfunctions of modern color TVs, such as the appearance of colored spots on the kinescope screen. There are also articles about modern portable technology - MP3 players, portable sound speakers and small-sized LCD TVs.

D la For a more complete assimilation of information, high-quality photographs of the repaired devices and their components are provided. In some cases, circuit diagrams, photographs of radio components and their pinouts. All information provided is based solely on personal experience in repairing consumer electronics.

To go to the article you are interested in, click the link or miniature picture icon located next to the brief description of the material.

Happy renovation!

Television equipment repair

What should you do if your LCD TV has lost its firmware and won’t turn on? We reflash SPI Flash memory 25 series. Detailed manual for beginner radio mechanics and electronics engineers.

On Erisson TVs, a common fault is the 2SB764 transistor in the vertical scanning circuits. However, the fault appears again even after replacing the faulty transistor with a new one. The cause of the malfunction is a “bug”, an error in the design of the device. The article discusses in detail an example of eliminating this defect when repairing Erisson TVs models 1401 and 2102.

The article discusses the repair of a portable LCD TV Prology HDTV-909S. Malfunction - the TV does not turn on. During the repair of the portable TV, the 2SA2039 transistor was replaced with a domestic analogue, which did not in any way affect the performance of the Prology LCD TV.

Repair of equipment with a laser optical drive

The main part of any disk device is the laser drive. A little knowledge about repairing and eliminating the causes of failures of these devices will not hurt, especially for novice radio mechanics!

Basic malfunctions of DVD players and methods for eliminating them (No disk and Error). The most vulnerable parts of DVD players are the laser reader, spindle drive, driver and main processor. Recommendations for repairing and replacing faulty parts and components of DVD players.

How to quickly replace the optical laser unit in a DVD? A simple step-by-step technique will relieve novice radio mechanics from the painstaking work of disassembling a DVD drive and replacing the laser in it.

When repairing car CD/MP3 players, it is sometimes necessary to clean the lens of the optical laser unit and replace the spindle motor in the CD drive. How to properly and quickly disassemble/assemble a CD drive? The article discusses a step-by-step method for disassembling a CD drive; for clarity, many photographs are provided.

Is your portable CD/MP3 player having trouble playing disc recordings? Learn how to troubleshoot your CD/MP3 player when playing a disc. An example from real-life repair practice, plus some tips on how to troubleshoot a portable CD/MP3 player.

Repair of sound-reproducing equipment

With this article we will begin our acquaintance with the device, circuitry, as well as the “components” of a car amplifier. Despite the apparent differences, all car amplifiers have a similar design and circuitry. The material presented in the article will help novice radio mechanics understand the structure of any car amplifier.

This article describes the device and repair speaker system SVEN IHOO MT5.1R. The information will be of interest to all those who are interested self-repair sound amplification equipment. An example of a real malfunction and repair methods. Attached is an archive with a schematic diagram of the device.

Despite the complexity of the circuitry of modern music centers, their malfunctions are quite typical. The practice of repair is shown using the example of troubleshooting a Samsung MAX-VS720 music center - hoarse and quiet sound. Find out now!

Simple repair of the Xcube player. The most common malfunctions of miniature MP-3 players are mechanical breakdowns associated with intensive use of these popular devices.

Once they brought me a Bluetooth speaker for repair. JBL Charge 3, but it turned out not to be her... An example of repairing a cheap copy of one of the popular wireless speaker systems.

IN lately Portable speaker systems, in English terminology - Portable Speakers, have become widespread. Portable speaker systems are especially in demand among young people. Portable speaker systems are small in size, good quality sound reproduction, autonomous power supply. What is the “electronic content” of these devices?

In repair practice, there are often cases when repairing a device is impossible due to the impossibility of replacing any electronic component. In such cases, you have to look for the most suitable replacement for the faulty part. The article discusses the repair of a portable speaker system. Instead of the faulty PAM8403 chip, the TDA2822 chip was quite successfully integrated.

According to the statistics of car radio malfunctions, in first place are breakdowns associated with the power circuits of these devices. A simple repair of the Mystery MCD-795MPU car radio is considered - the protective fuse has burned out, the radio does not turn on. This repair technique is useful when repairing any car radios: cassette, disk, diskless (with USB).

Repair of various household radio electronics

This article describes the design and repair of an electric thermos kettle. The design and purpose of specific parts and electronic components are examined in detail.

This article discusses the concept of a thermopot. The main electrical components, as well as electronic components that are used in thermopots from different companies, are examined in detail. The information will certainly be useful to all those who want to repair a faulty thermos kettle themselves.

Instead of ordinary household incandescent lamps, compact energy-saving lamps come, which can be installed in a standard E27 (E14) socket. Despite the fact that energy-saving lamps are more durable than conventional incandescent lamps, they also fail. The cost of energy-saving lamps is quite high and their repair is justified at least for personal purposes. Especially when you consider the fact that in most cases the lamp itself is working, but the high-frequency converter fails, which is easy to repair.

SMD installation is one of the most difficult to repair, especially in the absence of special equipment and necessary spare parts. Each radio mechanic solves the problem of replacing SMD components for himself. Here is one example...

Electrical safety during maintenance and repair of radio-electronic equipment

When repairing electrical installations, electronic devices and electrical wiring, you must follow simple electrical safety rules. The article briefly describes some of the techniques and rules that radio amateurs and electricians use in everyday practice.

Electrical equipment of vehicles

This article is devoted to the electrics and electrical equipment of an ordinary Chinese scooter. Almost all elements of the electrical circuit of the scooter, their purpose and features are described. The information will be of interest to all owners of Chinese scooters who are not familiar with the electrical equipment of the scooter, but want to know more about it.

A malfunction of the scooter relay regulator leads to undesirable consequences: the lighting lamps burn out and fail battery, over time, the battery charge decreases and you have to start the scooter with a kickstarter. You can check the relay regulator on a scooter using a multimeter. Read about how to do this here.

Power supply repair

The second part is a continuation of the first part and examines the composition and operation of the circuit management and control welding inverter.

5 parts are devoted to the circuitry of PC power supplies. Each of them talks about one of the electronic components of a switching power supply (UPS). Schematic diagrams are provided, as well as circuit solutions used in a specific circuit and possible malfunctions are described.

This series of articles will help those novice radio amateurs who want to learn how to repair, upgrade and independently analyze the circuitry of real power supplies. And although diagrams of electronic components of AT form factor UPSs are given as examples, the information provided will help you understand the principle of operation of a computer UPS and further understand the design of more complex ATX format UPSs.

Most floor scales are made according to the same principle, so they experience the same breakdowns. To find out how to fix electronic scales floor-mounted, you will need to study several important nuances.

Device of electronic floor scales

The product consists of several elements. As a rule, experts distinguish the following parts of it:

• display;
• frame;
• printed circuit board with various microcircuits;
• strain gauges.

You need to start diagnosing a device by looking for simple problems.

The device is made of tempered glass, which rarely fails due to the high strength of the case

The process of operating a bathroom scale involves constant pressure on its surface. After this, the load will be evenly distributed across the sensors. Metal strain gauges can fail due to the passage of time. If one of them sends the wrong value, .

If the scales do not work, then repairing the scales yourself is a difficult procedure. To fix most problems, you need to use a special tool. You also need to have skills, for example, to cope with replacing and soldering a new contact.

To diagnose a breakdown, you will need to check each element of the product. If the scales are completely turned off and do not turn on, you need to disassemble them and check the integrity of all wires. If they show incorrect data, then you need to look for a problem among the strain gauges.

Elimination of the most common breakdowns

To successfully repair, you will need to follow a simple algorithm of actions. If a person wants to know how to repair electronic floor scales, he should familiarize himself with step by step instructions repairs.

Sensor repair

If the scales break due to sensors, first of all you will need to establish the type of problem (sensor bending, wire breakage, complete breakdown). If the malfunction is related to the curvature of the structure, it will need to be straightened. Most often, one of the load cells fails. In this case, you will need to perform the following steps.

1. Check the functionality of the sensors. To do this, you need to press your hands on each of them. Even with slight pressure on only 1 sensor, the scale should turn on.
2. Disassemble the scales and carefully examine the wiring.
3. If there is a break (near the board or the sensor itself), it will need to be repaired. To do this you will need to use a soldering iron.
4. In some cases, the break is hidden behind the adhesive base. It is necessary to carefully open it and check the reliability of the connection.

Wires connected to the strain gauge

If the sensor is completely broken, it is replaced. Finding and buying a suitable spare part on your own is quite problematic. When looking for a new load cell, you need to pay attention to its compatibility with the device. It is better to purchase it in specialized stores. When purchasing, you must use the help of consultants. The new sensor will need to be secured in the mounting location, and the wires will also need to be soldered to it.

Repairing the cable

Loop repair is usually required when the numbers on the display are not fully displayed. A cable is a set of wires that connects the display and the board inside the device. To assess the condition of this element and carry out repairs, perform the following steps:

1. Complete disassembly of the case. Checking the integrity of the loop.
2. If the numbers are not fully displayed, this means that the cable is coming off.
3. Elements that move away from the board are securely soldered.

Fuzzy display of numbers on the display (example in the picture) may be due to its breakdown or poor-quality wire connection

You can use a special conductive glue to press the cable and all contacts to the board. After this, the problem should disappear. All gluing or soldering work must be carried out with great care. There is a possibility of damage to the board due to careless actions.

Device calibration

In some cases, the malfunction is due to incorrect setting sensors Incorrect data may appear on the display if for some reason calibration has not been performed. Modern scales automatically calibrate every time they are placed in a new location.