A car is a complex technical device in which many systems interact. Despite the high technology and reliability of a modern car, vehicle breakdowns periodically occur. Even the owner of a new car is not insured against malfunctions, and the warranty period is evidence of this.
When a malfunction occurs, two questions arise:
- fault determination (diagnostics);
- troubleshooting (repair).
Let's try to answer both questions.
The process of assessing the technical condition of a car and identifying faults is called diagnostics. The quality of the diagnostics determines the volume of repair work and, consequently, the cost of its implementation. Depending on the method of carrying out, the following types of diagnostics are distinguished:
- diagnosis by external signs (indirect diagnosis);
- technical diagnostics (direct diagnostics).
A car enthusiast, endowed with knowledge of car design, is able to independently carry out diagnosis by external signs. This is doubly true if you are on the road and the nearest car service center is many kilometers away.
Carrying out technical diagnostics requires special knowledge and skills, as well as the use of various instruments. For this reason, technical diagnostics are usually carried out in specialized centers. A type of technical diagnostics is computer diagnostics. Using special software, the functionality of the electronic components of the car is checked.
An experienced driver carries out indirect diagnostics of the car constantly - from the moment he gets into the car until the final stop. This happens almost automatically. While driving, the main attention is paid to the readings of instrumentation, as well as the characteristics of movement: engine operating mode, stability, smoothness, ease of control, braking efficiency. Deviations from standard parameters usually indicate a malfunction.
When diagnosing faults, you must be guided by the following principles:
- identifying and taking into account all obvious facts, in other words, establishing all external signs of a malfunction;
- Carrying out diagnostics from simple to complex, consistently eliminating possible malfunctions.
As practice shows, a car system malfunction rarely occurs unexpectedly. External signs of a malfunction appear gradually. It must be remembered that major malfunctions can be avoided if minor problems are diagnosed and corrected in a timely manner.
Signs of trouble, corresponding to certain human senses, can be divided into the following types:
- acoustic (hearing);
- visual (vision);
- operational (smell and touch).
A specific malfunction may have several external signs. These can be either signs of one type or a combination of them. For example, damage to the fuel system is accompanied by increased fuel consumption, as well as the smell of gasoline in the cabin and leaks under the car.
On the other hand, several faults may have similar external signs. For example, increased fuel consumption indicates a malfunction of the injectors, as well as incorrect setting of the ignition timing, low tire pressure, etc.
The largest group is acoustic signs of faults: all kinds of noises, knocks, squeaks, hums, rattles, crackles, etc. The sources of extraneous sounds are numerous, but the main ones are malfunctions of the engine, transmission, chassis and steering. There is a popular saying among motorists: “A good knock will always come out.” Many people understand it literally and operate the car until a specific breakdown occurs. At the same time, the meaning of the saying is somewhat different - every extraneous sound in the car indicates an incipient malfunction. And the sooner we install it, the less consequences there will be for the car and, accordingly, for our wallet. The most important thing is not to miss the diagnosis.
When extraneous sounds appear in the car, the driver must clearly understand in the presence of which sounds (read: malfunctions) it is possible to continue driving, and in which movement is strictly prohibited. For example, most extraneous sounds in the engine do not imply further operation of the car.
For fault diagnosis by sound it is necessary to establish the nature of the sound, the source of propagation, as well as the change in sound with increasing speed and changing direction of movement. The sound should be audible both inside the car and outside, including in the engine compartment.
Visual fault diagnosis is carried out based on the readings of instrumentation on the control panel, as well as through an external inspection of the vehicle. When conducting an external inspection, special attention is paid to the presence of smudges under the car, the serviceability of tires, and external lighting fixtures. An external inspection of systems and mechanisms in the engine compartment is periodically carried out. The oil level and special fluids are checked, the presence of leaks on the engine and gearbox, the integrity of the air pipes and electrical wiring.
TO operational signs of malfunctions include signs determined by smell and touch. Odors play an important role in diagnosing vehicle system malfunctions. So, the smell of gasoline in the cabin indicates a malfunction of the fuel system, the smell of exhaust gases (if it is not a KamAZ ahead) indicates a malfunction of the exhaust system, the smell of burnt engine oil indicates a malfunction of the lubrication system. A sweet chemical aroma appears when coolant leaks - a malfunction of the cooling system. A burnt catalytic converter will smell like rotten eggs. The melting wiring of the electrical equipment of the car also has its own specific smell.
The human body is also actively involved in diagnosing malfunctions: arms, legs, “fifth point”, skin. Many faults can be identified using touch. For example, jerking while driving indicates a malfunction of the ignition system. Difficulty shifting gears occurs when the gearbox is faulty. Malfunctions of suspension elements (springs, shock absorbers) are accompanied by sagging of the car. Increased brake pedal travel indicates a malfunction of the brake system, etc.
Thus, many faults can be identified by external signs, but not all, especially in electronics. In many cases, a modern car requires technical diagnostics.
Each driver solves the problem of eliminating the identified malfunction independently. Troubleshooting some problems does not require special skills. However, it is better to trust serious repair work to specialists.
» How to identify malfunctions of the car chassis
Operating a car on poor-quality roads often causes wear and tear on many parts. It is the chassis that has the hardest time - it takes all the “blows” of the domestic road. The suspension performs the most important tasks in the operation of a car. It distributes dynamic loads, improves traction, absorbs vibrations and noise, and adapts the chassis to a variety of road surfaces.
Violation of the integrity and performance of even one small element entails disruption of the entire chassis, which, in most cases, leads motorists to a service center. In the worst case scenario, safe driving may be compromised due to loss of control of the vehicle, and this already creates a serious risk of getting into a traffic accident.
There are many reasons that can cause such problems, and it is very important to notice the signs of chassis malfunctions in time.
- The car deviates to the left or right from straight-line movement
Reason: wheel alignment violations, difference in air pressure in tires, severe differences in wheel wear, difference in tread height.
If, after diagnosing and troubleshooting the problem, the problem of the car's drift does not disappear, then a full check of the chassis is necessary to identify the real causes of the problem. They can be: deformation of the front suspension arm, difference in the stiffness of the strut springs, violation of the parallelism of the axles, incomplete release of the wheel,
- The car sways when turning and braking
Reason: failure or malfunction of shock absorbers or springs, wear of anti-roll bar bushings, weakening or breakage of springs and suspension parts.
- Increased vibration when driving a car
Reason: tire pressure that does not meet the standards, damage to the springs, improper wheel balancing, loose wheel nuts, wheel damage (or deformation).
- Suspension noise and knocking
Reason: the shock absorber has failed, wear of the ball joints, wear of the silent blocks of the levers, damage to the strut of the levers, failure of the steering rack elements.
- Knock of shock absorbers
Reason: body geometry is broken, shock absorber leakage, suspension arm deformation, brake system malfunction, incorrect wheel alignment, shock absorber support wear.
- Creaking noises when braking on corners
Cause: faulty shock absorber struts, damage to anti-roll bar bushings.
- Frequent “punching” of the suspension
Cause: tires or wheels are deformed, shock absorbers are faulty, suspension arms are deformed.
- Wheel tire wear is uneven or increased
Reason: loose piston fastening, faulty shock absorber parts.
- Fluid leakage from shock absorber struts
Reason: there is too much fluid in the shock absorber, the rod seal is faulty, nicks have formed on the rod.
Alas, no driver is insured against damage to the car's chassis. Only careful driving on a good road will help you avoid trouble. The second condition is difficult to fulfill, given the seasonal damage to the road surface, so preventing damage would be a better option than costly repairing it at a car service center.
The chassis, like other elements of the car, needs care and timely inspection. The main thing in this matter is regularity, because the safe functioning of the entire car depends on regular diagnostics. A small deviation from the norm in work often leads to serious problems, and therefore it is not worth waiting for a nuisance to turn into a risk.
To do this, every car owner should know what points an inspection of the car’s chassis parts includes:
- — checking threaded connections (if necessary, they are tightened)
- — lubrication of parts of the front and rear suspensions according to the lubrication diagram of the vehicle
- — checking the amount of fluid in the shock absorber struts (if necessary, add fluid)
- — bearing adjustment control
- — checking the front wheels, if necessary, adjusting and balancing them
- — measuring the pressure in the tires (carried out using a tire pressure gauge)
- — the obligation to check the integrity and serviceability of the frame itself
- - replace stabilizer rods and bushings once every 30 thousand kilometers
- — driving onto an overpass will not be superfluous, since checking the suspension from below will be more productive. You should also check whether oil or other technical fluids are leaking anywhere.
A timely inspection, although it will take a certain amount of your time, will never be superfluous. This way you can prevent unpleasant surprises or sending your car to a car repair shop. Good luck on the roads!
Knock in the front suspension - suspension design and repair 
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Ball joint - purpose and design, causes of failure, diagnostics
What is diagnosing cell phone faults? This is a complete check of the functionality of all modules and functions with subsequent identification of faulty ones. Diagnostics can be divided into: primary (preliminary) and detailed. Primary diagnostics allows you to identify faults “on the fly”, i.e. without completely disassembling the phone. For example, malfunctions related to sound (speaker wheezes), image (display is broken), etc. Detailed diagnostics are carried out by disassembling the phone, thoroughly inspecting the board and all functional devices, as well as taking the necessary measurements and replacing faulty components.
When diagnosing, the first thing (MANDATORY!) is to check with the owner of the phone about the possible cause of the malfunction. For example, the phone fell, or the phone was flooded, etc. Conscientious people can tell the full biography of their phone, which greatly helps the repairman. And the majority either simply hide the fact of their guilt, or generally mislead, trying to deny guilt or begin to shift responsibility to children, friends, etc.
Be that as it may, you always need to check the current state of the phone in full detail and immediately, without delay, notify the owners so that later problems do not arise, such as: “before your repair, everything worked there!!!” And then it turns out that the phone was flooded with water and was simply dried out (at best) or sprinkled with sugar/salt and even put on charge. And then they bring it to repair and with a surprised face they say: “What are you doing? - Can't be!" etc. In such cases, it is best to immediately show the condition and appearance of the phone from the inside. Most questions disappear on their own.
Actually, closer to diagnosis
To begin with, I would like to list a few points that you need to know when starting diagnostics:
All modern phones have a nominal operating voltage of 3.6V - 3.7V. At the same time, the same voltage and sometimes battery capacity are also indicated on the battery. But, it should be remembered that a fully charged battery has a voltage of 4.2V - 4.3V. And at a nominal 3.6V, most phones will signal that the battery is low and ask you to charge the battery. Based on this, it becomes clear that a voltage of 3.6V or even a little less is sufficient to turn on and normal operation of the phone (some models work properly with a supply voltage of 3.3V - 3.4V but with a constant low-battery message). Many will switch off on their own. Therefore, for the normal diagnostic and repair process, you should connect a power source of at least 3.7V - 3.8V, and preferably 4.0V - 4.2V.
Most phones can be turned on by powering them from the power supply. It is enough, observing the polarity, to connect the corresponding clamps of the supply wires to the contacts of the connector (connector/terminal block) of the battery and, as usual, start the phone with the power button. And then you can see the following:
A) the phone will turn on normally and function;
B) the phone will turn on and swear like “Invalid battery” or “Unknown battery”, etc.;
C) the phone will turn on, but will ask you to install a SIM card, even if it is installed (true for NOKIA phones);
D) the phone will either turn on for a short time and turn off again or not turn on at all.
In all points except a), the culprit is the missing “3rd” contact of the battery temperature sensor (see above for the description of the battery device). In cases a) and b) you can carry out a full diagnosis of the phone, except for charging, because For these purposes it is necessary to connect the battery accordingly. For point c) you can connect the middle contact of the battery connector to the negative one. After which the phone will start properly from the power button and will safely see the SIM card. For point d) you will have to connect only a charged battery or cheat with the middle contact by selecting a resistor whose resistance value corresponds to the resistance on the electronics board of the standard battery and connect it to the middle contact relative to the “-” terminal.
What is the difference between connecting a phone to a power supply or a standard battery? There is no fundamental difference for a telephone. But you can find out a few things.
Option 1 - turning on the phone from the standard battery:
If the phone turns on normally and shows normal battery charge, but turns off very quickly, especially when registering on the network, then this may be a sign of one of the malfunctions:
The phone battery has lost its capacity and under load its voltage drops below the set level. Consequently, the phone cannot operate at a supply voltage below the permissible one. This battery is considered faulty and must be replaced.
The phone has increased current consumption. This indicates a faulty phone board. This malfunction may occur as a result of exposure of the phone to moisture or shock.
The malfunction can be more accurately determined through detailed diagnostics.
Option 2 - turn on the phone from the power supply:
The most important advantage of a power supply unit (PSU) is its versatility, i.e. You can power any phone from it, and it is always ready to work, unlike a dead battery at the most inopportune moment. And if it is also equipped with an ammeter (with a possible lower division of the measuring scale), then a lot can be said about the operation of the phone based on the readings of this device. The ammeter reading just shows the current consumption of the phone. What consumption is considered normal? - It is different for each phone, but it is within approximately the same limits. For clarity: when turned off (provided it is in full working order), the phone does not consume energy. Well, to be absolutely precise, it’s very little, which is comparable to the self-discharge of a battery. Energy is spent on powering the processor clock generator and/or power controller and a small part of RAM for the normal operation of the “clock/date/alarm clock” and some other phone service processes. When you turn it on and continue working, a lot of phone devices go into active mode and consumption increases. The following components consume the most energy in a phone:
Keyboard and display backlight ~ 70 – 300 mA (for different models) in active mode. On average up to 150 - 200 mA.
GSM module power amplifier (PA – Power Amplifier). It varies for different phones + this parameter depends on the signal level of the cellular network coverage. The weaker the signal, the more energy is consumed. On average up to 200mA. Some older phones from previous generations typically consume up to 400 mA.
Audio Power Amplifier. Depends on the output signal level. On average up to ~100 mA.
If the phone is turned on and in standby mode (i.e. none of the above modules is currently active), the consumption is very small and amounts to a few milliamps. Bursts periodically occur during the exchange of data between the phone and the base station. If the consumption in standby mode is constant and amounts to more than a milliampere, there is something wrong with the phone. The battery of such a phone will discharge prematurely. Most often this happens as a result of moisture or the phone has been hit or dropped as a result of which some elements have failed.
You should always pay attention to this parameter, otherwise the phone will definitely be returned to you after repair with the remaining increased consumption.
Further. Never succumb to provocations from phone owners who are in a panic and want to urgently flash their phone because it is BUGGY! I can’t stand this word, because it usually means ANYTHING and instead of clearly explaining a specific malfunction of the phone, they simply say IT’S GLUGGY! YOU GIVE IT TO ME! But in fact, it turns out that the phone was damaged, and through the fault of the user. For example, the battery quickly discharges, communication is lost, the keyboard does not work, and the like. They listen to each other and read a lot on the Internet, and then take them anywhere, just to flash them. What type of repair to carry out on the phone - to flash it or not to flash it - should be decided by YOU after a detailed diagnosis!
When starting diagnostics, in addition to the necessary equipment and materials, you must have a minimum (to begin with) set of spare parts - displays, cables, bells, speakers, microphones, etc. It's obvious. An equally important point is the presence of an electrical circuit diagram with the arrangement of elements on the printed circuit board, preferably together with disassembly/assembly instructions. After all, you can figure it out blindly only with experience and subject to frequent repairs of certain models. In such cases, the location of the elements on the board is stored in the head, which greatly speeds up the troubleshooting process. You can find diagrams of mobile phones on the Internet on thematic sites, forums, etc. There are situations when you cannot find a circuit diagram for your phone. Most often on very new phone models. In this case, you can almost always find a service manual (from English Service-manual) - service instructions. As a rule, it contains instructions for disassembling/assembling the phone and fragments of an electrical circuit diagram, and also indicates (not always) a troubleshooting algorithm for the main categories (does not turn on, speaker/microphone does not work, does not see the SIM card, etc. .)
Electronics accompany modern people everywhere: at work, at home, in the car. When working in production, no matter what specific field, you often have to repair something electronic. Let’s agree to call this “something” a “device”. This is such an abstract collective image. Today we’ll talk about all sorts of repair tricks, which, having mastered, will allow you to repair almost any electronic “device”, regardless of its design, operating principle and scope of application.
Where to begin
There is little wisdom in re-soldering a part, but finding the defective element is the main task in repair. You should start by determining the type of fault, since this determines where to start the repair.
There are three types:
1. the device does not work at all - the indicators do not light up, nothing moves, nothing buzzes, there is no response to control;
2. any part of the device does not work, that is, part of its functions is not performed, but although glimpses of life are still visible in it;
3. The device mostly works properly, but sometimes it makes so-called malfunctions. Such a device cannot yet be called broken, but still something prevents it from working normally. Repair in this case consists precisely in searching for this interference. This is considered to be the most difficult repair.
Let's look at examples of repairs for each of the three types of faults.
First category repair
Let's start with the simplest one - the first type of failure is when the device is completely dead. Anyone can guess that you need to start with nutrition. All devices living in their own world of machines necessarily consume energy in one form or another. And if our device does not move at all, then the probability of the absence of this very energy is very high. A small digression. When troubleshooting in our device, we will often talk about “probability”. Repair always begins with the process of identifying possible points of influence on the malfunction of the device and assessing the probability of each such point being involved in a given specific defect, followed by turning this probability into a fact. At the same time, to make a correct, that is, with the highest degree of probability, assessment of the influence of any block or node on the problems of the device will help the most complete knowledge of the design of the device, the algorithm of its operation, the physical laws on which the operation of the device is based, the ability to think logically and, of course , His Majesty's experience. One of the most effective methods of repair is the so-called elimination method. From the entire list of all blocks and assemblies suspected of involvement in a device defect, with varying degrees of probability, it is necessary to consistently exclude the innocent ones.
It is necessary to start the search accordingly with those blocks whose probability of being the culprits of this malfunction is the highest. Hence it follows that the more accurately this degree of probability is determined, the less time will be spent on repairs. In modern “devices” the internal nodes are highly integrated with each other, and there are a lot of connections. Therefore, the number of points of influence is often extremely large. But your experience also grows, and over time you will identify the “pest” in a maximum of two or three attempts.
For example, there is an assumption that block “X” is most likely to blame for the malfunction of the device. Then you need to carry out a series of checks, measurements, experiments that would confirm or refute this assumption. If after such experiments there remains even the slightest doubt about the non-involvement of the block in the “criminal” influence on the device, then this block cannot be completely excluded from the list of suspects. You need to look for a way to check the suspect’s alibi in order to be 100% sure of his innocence. This is very important in the elimination method. And the most reliable way to check a suspect in this way is to replace the unit with a known good one.
Let us return to our “patient”, in whom we assumed a power failure. Where to start in this case? And as in all other cases - with a complete external and internal examination of the “patient”. Never neglect this procedure, even when you are sure that you know the exact location of the breakdown. Always inspect the device completely and very carefully, without rushing. Often during an inspection you can find defects that do not directly affect the fault being sought, but which may cause a breakdown in the future. Look for burnt electrical components, swollen capacitors, and other suspicious-looking items.
If the external and internal examination does not bring any results, then pick up a multimeter and get to work. I hope there is no need to remind you about checking the presence of mains voltage and fuses. Let's talk a little about power supplies. First of all, check the high-energy elements of the power supply unit (PSU): output transistors, thyristors, diodes, power microcircuits. Then you can start sinning on the remaining semiconductors, electrolytic capacitors and, last of all, on the remaining passive electrical elements. In general, the probability of failure of an element depends on its energy saturation. The more energy an electrical element uses to operate, the greater the likelihood of its failure.
While mechanical components are worn out by friction, electrical components are worn out by current. The higher the current, the greater the heating of the element, and heating/cooling wears out any materials no worse than friction. Temperature fluctuations lead to deformation of the material of electrical elements at the micro level due to thermal expansion. Such variable temperature loads are the main reason for the so-called material fatigue effect during the operation of electrical elements. This must be taken into account when determining the order of checking elements.
Don’t forget to check the power supply for output voltage ripples or any other interference on the power buses. Although not often, such defects can cause the device to not work. Check whether the power actually reaches all consumers. Maybe due to problems in the connector/cable/wire this “food” does not reach them? The power supply will be in good working order, but there will still be no energy in the device blocks.
It also happens that the fault lies in the load itself - a short circuit (short circuit) is not uncommon there. At the same time, some “economical” power supplies do not have current protection and, accordingly, there is no such indication. Therefore, the version of the short circuit in the load should also be checked.
Now the second type of failure. Although here everything should also begin with the same external-internal examination, there is a much greater variety of aspects that should be paid attention to. - The most important thing is to have time to remember (write down) the whole picture of the state of the sound, light, digital indication of the device, error codes on the monitor, display, the position of alarms, flags, blinkers at the time of the accident. Moreover, it must be done before it is reset, acknowledged, or turned off! It is very important! Missing some important information will certainly increase the time spent on repairs. Inspect all available indications - both emergency and operational, and remember all the readings. Open the control cabinets and remember (write down) the state of the internal indication, if any. Shake the boards installed on the motherboard, cables and blocks in the device body. Maybe the problem will go away. And be sure to clean the cooling radiators.
Sometimes it makes sense to check the voltage on some suspicious indicator, especially if it is an incandescent lamp. Carefully read the readings of the monitor (display), if available. Decipher the error codes. Look at the tables of input and output signals at the time of the accident, write down their status. If the device has the function of recording processes occurring with it, do not forget to read and analyze such an event log.
Don't be shy - smell the device. Is there a characteristic smell of burnt insulation? Pay special attention to products made of carbolite and other reactive plastics. It doesn’t happen often, but it happens that they break through, and this breakdown is sometimes very hard to see, especially if the insulator is black. Due to their reactive properties, these plastics do not warp when exposed to high heat, which also makes it difficult to detect broken insulation.
Look for darkened insulation on the windings of relays, starters, and electric motors. Are there any darkened resistors or other electrical and radio elements that have changed their normal color and shape?
Are there any swollen or cracked capacitors?
Check if there is any water, dirt or foreign objects in the device.
Look to see if the connector is skewed, or if the block/board is not fully inserted into its place. Try taking them out and reinserting them.
Perhaps some switch on the device is in the wrong position. The button is stuck, or the moving contacts of the switch are in an intermediate, not fixed position. Perhaps the contact has disappeared in some toggle switch, switch, potentiometer. Touch them all (with the device de-energized), move them, turn them on. It won't be redundant.
Check the mechanical parts of the executive bodies for jamming - turn the rotors of electric motors and stepper motors. Move other mechanisms as necessary. Compare the force applied with other similar working devices, if of course there is such a possibility.
Inspect the insides of the device in operating condition - you may see strong sparking in the contacts of relays, starters, switches, which will indicate an excessively high current in this circuit. And this is already a good clue for troubleshooting. Often the cause of such a breakdown is a defect in a sensor. These intermediaries between the outside world and the device they serve are usually located far beyond the boundaries of the device body itself. And at the same time, they usually work in a more aggressive environment than the internal parts of the device, which are somehow protected from external influences. Therefore, all sensors require increased attention. Check their performance and take the time to clean them from dirt. Limit switches, various interlocking contacts and other sensors with galvanic contacts are high priority suspects. And in general any “dry contact” i.e. not soldered, should become an element of close attention.
And one more thing - if the device has served for a long time, then you should pay attention to the elements that are most susceptible to any wear or change in their parameters over time. For example: mechanical components and parts; elements exposed to increased heat or other aggressive influences during operation; electrolytic capacitors, some types of which tend to lose capacity over time due to drying of the electrolyte; all contact connections; device controls.
Almost all types of “dry” contacts lose their reliability over time. Particular attention should be paid to silver-plated contacts. If the device has been operating for a long time without maintenance, I recommend that before starting an in-depth troubleshooting, you do preventive maintenance on the contacts - lighten them with a regular eraser and wipe with alcohol. Attention! Never use abrasive sandpaper to clean silver-plated or gold-plated contacts. This is certain death for the connector. Plating with silver or gold is always done in a very thin layer, and it is very easy to erase it down to copper with an abrasive. It is useful to carry out the procedure for self-cleaning the contacts of the socket part of the connector, in the professional slang of “mother”: connect and disconnect the connector several times, the spring contacts are slightly cleaned from friction. I also advise that when working with any contact connections, do not touch them with your hands - oil stains from your fingers negatively affect the reliability of the electrical contact. Cleanliness is the key to reliable contact operation.
The first thing is to check the operation of any blocking or protection at the beginning of the repair. (In any normal technical documentation for the device there is a chapter with a detailed description of the interlocks used in it.)
After inspecting and checking the power supply, figure out what is most likely broken in the device, and check these versions. You shouldn’t go straight into the jungle of the device. First, check all the periphery, especially the serviceability of the executive bodies - perhaps it is not the device itself that has broken down, but some mechanism controlled by it. In general, it is recommended to study, albeit not to the subtleties, the entire production process in which the device in question is a participant. When the obvious versions have been exhausted, then sit down at your desk, brew some tea, lay out diagrams and other documentation for the device and “give birth” to new ideas. Think about what else could have caused this device illness.
After some time, you should have a certain number of new versions. Here I recommend not to rush to run and check them. Sit somewhere calm and think about these versions regarding the magnitude of the probability of each of them. Train yourself in assessing such probabilities, and when you gain experience in such selection, you will begin to make repairs much faster.
The most effective and reliable way to check the functionality of a suspected unit or device assembly, as already mentioned, is to replace it with a known good one. Do not forget to carefully check the blocks for their complete identity. If you connect the unit under test to a device that is working properly, then if possible, be on the safe side - check the unit for excessive output voltages, a short circuit in the power supply and in the power section, and other possible malfunctions that can damage the working device. The opposite also happens: you connect a donor working board to a broken device, check what you wanted, and when you return it back, it turns out to be inoperative. This doesn't happen often, but keep this point in mind.
If in this way it was possible to find a faulty unit, then the so-called “signature analysis” will help to further localize the search for a fault to a specific electrical element. This is the name of the method in which the repairman conducts an intelligent analysis of all the signals with which the tested node “lives”. Connect the unit, node, or board under study to the device using special extension cords-adapters (these are usually supplied with the device) so that there is free access to all electrical elements. Lay out the circuit and measuring instruments nearby and turn on the power. Now compare the signals at the control points on the board with the voltages and oscillograms on the diagram (in the documentation). If the diagram and documentation do not shine with such details, then rack your brains. Good knowledge of circuit design will come in handy here.
If you have any doubts, you can “hang” a working sample board from the working device on the adapter and compare the signals. Check with the diagram (with documentation) all possible signals, voltages, oscillograms. If a deviation of any signal from the norm is found, do not rush to conclude that this particular electrical element is faulty. It may not be the cause, but simply a consequence of another abnormal signal that forced this element to produce a false signal. During repairs, try to narrow your search and localize the fault as much as possible. When working with a suspected node/unit, come up with tests and measurements for it that would rule out (or confirm) the involvement of this node/unit in this malfunction for sure! Think seven times when you exclude a block from being unreliable. All doubts in this case must be dispelled by clear evidence.
Always do experiments intelligently; the “scientific poke” method is not our method. They say, let me poke this wire here and see what happens. Never be like such “repairers”. The consequences of any experiment must be thought out and provide useful information. Pointless experiments are a waste of time, and besides, you can break something. Develop your ability to think logically, strive to see clear cause-and-effect relationships in the operation of the device. Even the operation of a broken device has its own logic, there is an explanation for everything. If you can understand and explain the non-standard behavior of the device, you will find its defect. In the repair business, it is very important to clearly understand the operating algorithm of the device. If you have gaps in this area, read the documentation, ask everyone who knows something about the issue you are interested in. And don’t be afraid to ask, contrary to popular belief, this does not reduce your authority in the eyes of your colleagues, but on the contrary, smart people will always appreciate it positively. It is absolutely unnecessary to memorize the circuit diagram of the device; paper was invented for this purpose. But you need to know the algorithm of its operation by heart. And now you have been “shaking” the device for several days now. We have studied it so much that it seems like there is nowhere else to go. And they have repeatedly tortured all suspected blocks/nodes. Even seemingly the most fantastic options have been tried, but the fault has not been found. You are already starting to get a little nervous, maybe even panic. Congratulations! You have reached the climax of this renovation. And the only thing that can help here is... rest! You're just tired and need to take a break from work. As experienced people say, your eyes are blurry. So quit work and completely disconnect your attention from the device in your care. You can do another job, or do nothing at all. But you need to forget about the device. But when you rest, you yourself will feel the desire to continue the battle. And as often happens, after such a break you will suddenly see such a simple solution to the problem that you will be incredibly surprised!
But with a third type of malfunction, everything is much more complicated. Since malfunctions in the operation of the device are usually random, it often takes a lot of time to catch the moment the malfunction occurs. The peculiarities of the external inspection in this case consist in combining the search for a possible cause of the failure with carrying out preventive work. For reference, here is a list of some possible causes of failures.
Bad contact (first of all!). Clean the connectors all at once in the entire device and carefully inspect the contacts.
Overheating (as well as overcooling) of the entire device, caused by increased (low) ambient temperature, or caused by prolonged operation with high load.
Dust on boards, components, blocks.
Cooling radiators are dirty. Overheating of the semiconductor elements they cool can also cause failures.
Interference in the power supply. If the power filter is missing or has failed, or its filtering properties are insufficient for the given operating conditions of the device, then malfunctions in its operation will be frequent guests. Try to associate the failures with the inclusion of some load in the same electrical network from which the device is powered, and thereby find the culprit of the interference. Perhaps it is the network filter in the neighboring device that is faulty, or some other fault in it, and not in the device being repaired. If possible, power the device for a while from an uninterruptible power supply with a good built-in surge protector. The failures will disappear - look for the problem on the network.
And here, as in the previous case, the most effective method of repair is the method of replacing blocks with known good ones. When changing blocks and assemblies between identical devices, carefully ensure that they are completely identical. Pay attention to the presence of personal settings in them - various potentiometers, customized inductance circuits, switches, jumpers, jumpers, software inserts, ROMs with different firmware versions. If there are any, then make the decision to replace it after considering all the possible problems that may arise due to the risk of disruption to the operation of the unit/assembly and the device as a whole, due to differences in such settings. If there is still an urgent need for such a replacement, then reconfigure the blocks with a mandatory recording of the previous state - this will be useful when returning.
It happens that all the boards, blocks, and components that make up the device have been replaced, but the defect remains. This means that it is logical to assume that the fault is lodged in the remaining periphery in the wiring harnesses, the wiring inside some connector has come off, there may be a defect in the backplane. Sometimes the culprit is a jammed connector pin, for example in a card box. When working with microprocessor systems, running test programs several times sometimes helps. They can be looped or configured for a large number of cycles. Moreover, it is better if they are specialized test ones, and not working ones. These programs are able to record a failure and all the information accompanying it. If you know how, write such a test program yourself, focusing on a specific failure.
It happens that the frequency of a failure has a certain pattern. If the failure can be timed to the execution of a specific process in the device, then you are in luck. This is a very good lead for analysis. Therefore, always carefully monitor device failures, notice all the circumstances under which they occur, and try to associate them with the performance of some function of the device. Long-term observation of a faulty device in this case can provide a clue to solving the mystery of the failure. If you find the dependence of the occurrence of a malfunction on, for example, overheating, an increase/decrease in supply voltage, or vibration, this will give some idea of the nature of the malfunction. And then - “let the seeker find.”
The control replacement method almost always brings positive results. But the block found in this way may contain many microcircuits and other elements. This means that it is possible to restore the operation of the unit by replacing only one, inexpensive part. How to localize the search further in this case? All is not lost here either; there are several interesting techniques. It is almost impossible to catch a failure using signature analysis. Therefore, we will try to use some non-standard methods. It is necessary to provoke a block to fail under a certain local influence on it, and at the same time it is necessary that the moment of manifestation of the failure can be tied to a specific part of the block. Hang the block on the adapter/extension cord and start torturing it. If you suspect a microcrack in the board, you can try to fix the board on some rigid base and deform only small parts of its area (corners, edges) and bend them in different planes. And at the same time observe the operation of the device - catch a failure. You can try tapping the handle of a screwdriver on parts of the board. Once you have decided on the area of the board, take the lens and carefully look for the crack. Not often, but sometimes it is still possible to detect a defect, and, by the way, a microcrack is not always the culprit. Soldering defects are much more common. Therefore, it is recommended not only to bend the board itself, but also to move all its electrical elements, carefully observing their soldered connection. If there are few suspicious elements, you can simply solder everything at once so that there are no more problems with this block in the future.
But if any semiconductor element of the board is suspected as the cause of the failure, it will not be easy to find it. But here, too, you can say that there is a somewhat radical way to provoke a failure: in working condition, heat each electrical element in turn with a soldering iron and monitor the behavior of the device. The soldering iron must be applied to the metal parts of electrical elements through a thin mica plate. Heat to about 100-120 degrees, although sometimes more is required. In this case, of course, there is a certain probability of additionally damaging some “innocent” element on the board, but whether it’s worth the risk in this case is up to you to decide. You can try the opposite, cooling with ice. Also not often, but you can still try this way, as we say, “pick out a bug.” If it’s really hot, and if possible, of course, then change all the semiconductors on the board. The order of replacement is in descending order of energy and saturation. Replace several blocks at a time, periodically checking the operation of the block for failures. Try to thoroughly solder all the electrical elements on the board, sometimes just this procedure alone returns the device to a healthy life. In general, with a malfunction of this type, complete recovery of the device can never be guaranteed. It often happens that while troubleshooting you accidentally moved some element that had a weak contact. In this case, the malfunction has disappeared, but most likely this contact will manifest itself again over time. Repairing a malfunction that rarely occurs is a thankless task; it requires a lot of time and effort, and there is no guarantee that the device will be repaired. Therefore, many craftsmen often refuse to undertake the repair of such capricious devices, and, frankly, I don’t blame them for this.
PC Troubleshooting- some useful tips that will allow you to correctly diagnose and repair computers yourself at home.
- You can carry out diagnostics very efficiently, without resorting to the services of professionals for money. Each computer failure manifests itself differently, and sometimes it is not so easy to identify it.
For example, the mouse does not respond when you click on Start, and all attempts to turn off the computer are in vain. Or, at startup, some important functions remain unavailable, the browser does not work, there is no Internet or a blue screen, etc.
One way or another, you first need to try to figure out the causes of the malfunction yourself. Check basic functions, visually inspect the motherboard for swollen capacitors, whether all parts of the system unit are tightly inserted, whether it is possible to enter the BIOS, and so on.
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If something doesn’t work out, move on to another diagnostic procedure, and return to the one that didn’t work out later. This will help you more accurately understand what exactly is not working and, if necessary, tell the technician in more detail about the malfunction upon arrival, so that he understands where to start looking at the problem.
1.Does not respond to the power button on the system unit.
- The computer simply does not turn on, there are no signs of performance. In this situation it is necessary check all batteries, the entire chain, starting from the power supply and ending with the motherboard.
Check all cables and cables, inspect the power supply to see if there is a burning smell. And it is important to check the button on the power supply that supplies and disconnects electrical current to the power supply.
It might just be turned off (this happens sometimes). If the visual inspection does not reveal any obvious defects, then we proceed to inspect the motherboard. Usually the connectors that power the motherboard and processor are checked. If the plugs are disconnected or torn off, they must be carefully connected to the correct sockets and connectors.
- If this diagnostic does not produce tangible results, then you should disconnect all plugs from the motherboard. Then you need to use a screwdriver to bridge the contacts on the system board that are responsible for starting, usually power sw.
If after closing the computer started, then this means that The power button may be faulty on the body. To get out of the situation, you can do this. For example, there is a second button on your case - Reset.
You can assign the computer to start with this button. We connect the Reset sw connectors to the Power sw connectors. Now you can use the Reset button to turn on the computer. Since we are talking about this button, I would like to remind you that during normal computer operation it is highly not recommended to use this button, as it harms the hard drive.
- You can check whether the problem is in the power supply or not. To do this, as you guessed, you just need to connect another power supply. If everything worked, then the problem was in the power supply.
If the above measures do not help, this may indicate motherboard malfunction. In this case, PC diagnostics and repairs on your own will not help. You need to diagnose the system board in a service center or replace it.
2.The image does not appear on your computer monitor.
If the monitor does not display an image, but it is clear from the operation of the LEDs on the motherboard and the operation of the fans that the computer is working, then you should understand the devices responsible for outputting the image to the monitor.
- In this situation, you need to check the monitor itself for functionality. Connect it to another working device.
Very often, when the video signal stops reaching the monitor, the system reports this with appropriate signals. In this case, you need to have with you decoding BIOS signals for your motherboard.
This symptom also appears if there is a short circuit inside the Reset button itself.
- Also, the lack of a picture on the monitor also happens due to incorrect settings of the BIOS itself. To do this, you need to reset the settings to factory settings. This can be done using a jumper or in the BIOS itself. The motherboard usually has a Clear Cmos jumper. You just need to close it and return it to its normal position. You can also remove the battery for 1-2 minutes.
- Sometimes it happens that the image disappears due to non-working RAM. You need to try to start the computer alternately with one or the other (if there are 2 of them). If there is only one bar, then you need to try to insert another bar of the same type and try to launch with it.
- A faulty video card can be identified by replacement with another. If everything works with another card, then that was the problem.
- Sometimes the image is not displayed on the monitor due to the processor. This happens sometimes too. Therefore, you can also try as an option replace processor.
Now you know how to carry out PC troubleshooting. If you have done all of the above and the picture still does not appear, then most likely there is a problem with the computer’s motherboard. More detailed diagnostics only in a service center.
