Good afternoon, dear radio amateurs!
Welcome to the website ““

Microcircuits

Chip (IC – Integrated Circuit, IC – Integrated Circuit, chip or microchip from English Chip, Microchip) is a whole device containing transistors, diodes, resistors and other active and passive elements, the total number of which can reach several tens, hundreds, thousands, tens of thousands or more. There are quite a lot of types of microcircuits. The most used among them are brain teaser, operational amplifiers, specialized.

Most of the chips are housed in a rectangular plastic case with flexible plate leads (see Fig. 1) located along both sides of the case. On top of the case there is a conventional key - a round or other shaped mark from which the pins are numbered. If you look at the microcircuit from above, then you need to count the pins counterclockwise, and if from below, then in the direction of clockwise movement. Microcircuits can have any number of pins.

In domestic electronics (as well as in foreign ones too), microcircuits are especially popular brain teaser, built on the basis bipolar transistors and resistors. They are also called TTL chips (TTL – Transistor-Transistor Logic). The name transistor-transistor comes from the fact that transistors are used both to perform logical functions and to amplify the output signal. Their entire operating principle is built on two conditional levels: low or high, or, equivalently, the state of logical 0 or logical 1. Thus, for K155 series microcircuits, voltages from 0 to 0.4 are taken as the low level corresponding to logical 0. V, that is, no more than 0.4 V, and for a high one, corresponding to logical 1, no less than 2.4 V and no more than the power supply voltage - 5 V, and for K176 series microcircuits, designed for power supply from a source, a voltage of 9 B, respectively 0.02. ..0.05 and 8.6. ..8.8 V.

Marking of foreign TTL microcircuits begins with the numbers 74, for example 7400. Graphic symbols of the main elements of logic chips are shown in Fig. 2. Truth tables are also given there, giving an idea of ​​the logic of the action of these elements.

Symbol logic element And the “&” sign serves(the conjunction “and” in English language) standing inside the rectangle (see Fig. 2). On the left are two (or more) input pins, on the right is one output pin. The logic of the operation of this element is as follows: a high-level voltage at the output will appear only when signals of the same level are at all its inputs. The same conclusion can be drawn by looking at the truth table characterizing the electrical state of the AND element and the logical connection between its output and input signals. So, for example, in order for the output (Out.) of the element to have a high level voltage, which corresponds to a single (1) state of the element, both inputs (In. 1 and In. 2) must have voltages of the same level. In all other cases, the element will be in the zero (0) state, that is, a low level voltage will operate at its output.
Conditional symbol of a logical element OR- number 1 in a rectangle. It, like the AND element, can have two or more inputs. An output signal corresponding to a high level (logical 1) appears when a signal of the same level is applied to input 1 or input 2 or simultaneously to all inputs. Check these logical relationships between the output and input signals of this element against its truth table.
Element symbol NOT- also a number 1 inside a rectangle. But it has one entrance and one exit. The small circle that begins the communication line of the output signal symbolizes the logical negation of “NOT” at the output of the element. In the language of digital technology, “NOT” means that the element is NOT an inverter, that is, an electronic “brick” whose output signal is opposite in level to the input one. In other words: as long as there is a low level signal at its input, there will be a high level signal at the output, and vice versa. This is also evidenced by the logical levels in the truth table of the operation of this element.
Logic element AND-NOT is a combination of elements AND And NOT, therefore, on its conventional graphic designation there is a sign “ & ” and a small circle on the output signal line, symbolizing logical negation. There is one output, but two or more inputs. The logic of the element’s operation is as follows: a high-level signal at the output appears only when there are low-level signals at all inputs. If at least one of the inputs has a low-level signal, the output of the AND-NOT element will have a high-level signal, that is, it will be in the single state, and if there is a high-level signal at all inputs, it will be in the zero state. The AND-NOT element can perform the function of a NOT element, that is, become an inverter. To do this, you just need to connect all its inputs together. Then, when a low-level signal is applied to such a combined input, the output of the element will be a high-level signal, and vice versa. This property of the NAND element is very widely used in digital technology.

The designation of logical element symbols (signs “&” or “1”) is used only in domestic circuitry.

TTL microcircuits enable the construction of a wide variety of digital devices operating at frequencies up to 80 MHz, but their significant drawback is their high power consumption.
In a number of cases, when high performance is not needed, but minimum power consumption is required, CMOS chips are used, which use field-effect transistors rather than bipolar ones. Reduction CMOS (CMOS Complementary Metal-Oxide Semiconductor) stands for Complementary Metal Oxide Semiconductor. The main feature of CMOS microcircuits is their negligible current consumption in static mode - 0.1...100 µA. When operating at the maximum operating frequency, power consumption increases and approaches the power consumption of the least powerful TTL chips. CMOS microcircuits include such well-known series as K176, K561, KR1561 and 564.

In class analog microcircuits allocate microcircuits with linear characteristics– linear microcircuits, which include OU – Operational Amplifiers. Name " operational amplifier ” is due to the fact that, first of all, such amplifiers are used to perform operations of summing signals, differentiating them, integrating, inverting, etc. As a rule, analog microcircuits are produced functionally unfinished, which opens up wide scope for amateur radio creativity.

Operational amplifiers have two inputs - inverting and non-inverting. In the diagram they are indicated by minus and plus, respectively (see Fig. 3). By applying a signal to the plus input, the output is unchanged, but amplified signal. By applying it to the minus input, the output is an inverted, but also amplified signal.

In the production of radio-electronic products use of multifunctional specialized chips requiring a minimum number of external components, allows you to significantly reduce the development time of the final device and production costs. This category of chips includes chips that are designed to do something specific. For example, there are microcircuits for power amplifiers, stereo receivers, and various decoders. They can all look completely different. If one of these chips has a metal part with a hole, that means it needs to be screwed to
radiator

Dealing with specialized microcircuits is much more pleasant than with a mass of transistors and resistors. If previously many parts were needed to assemble a radio receiver, now you can get by with one microcircuit.

There are two testing methods to diagnose a fault electronic system, device or printed circuit board: functional control and in-circuit control. Functional control checks the operation of the module under test, and in-circuit control consists of checking individual elements of this module in order to determine their ratings, switching polarity, etc. Typically, both of these methods are used sequentially. With the development of automatic testing equipment, it became possible to perform very fast in-circuit testing with individual testing of each element of the printed circuit board, including transistors, logic elements and counters. Functional control has also moved to a new qualitative level thanks to the use of computer data processing and computer control methods. As for the principles of troubleshooting themselves, they are exactly the same, regardless of whether the check is carried out manually or automatically.

Troubleshooting must be carried out in a certain logical sequence, the purpose of which is to find out the cause of the malfunction and then eliminate it. The number of operations performed should be kept to a minimum, avoiding unnecessary or pointless checks. Before checking a faulty circuit, you need to carefully inspect it for possible detection of obvious defects: burnt-out elements, broken conductors on printed circuit board etc. This should take no more than two to three minutes; with experience, such visual control will be performed intuitively. If the inspection yields nothing, you can proceed to the troubleshooting procedure.

First of all it is carried out functional test: The operation of the board is checked and an attempt is made to determine the faulty unit and the suspected faulty element. Before replacing a faulty element, you need to carry out in-circuit measurement parameters of this element in order to verify its malfunction.

Functional tests

Functional tests can be divided into two classes, or series. Tests episode 1, called dynamic tests, applied to a complete electronic device to isolate a faulty stage or block. When a specific block is found to which the fault is associated, tests are applied series 2, or static tests, to determine one or two possibly faulty elements (resistors, capacitors, etc.).

Dynamic tests

This is the first set of tests performed when troubleshooting an electronic device. Troubleshooting should be carried out in the direction from the device output to its input along halving method. The essence of this method is as follows. First, the entire circuit of the device is divided into two sections: input and output. A signal similar to the signal that, under normal conditions, operates at the splitting point is applied to the input of the output section. If a normal signal is obtained at the output, then the fault must be in the input section. This input section is divided into two subsections and the previous procedure is repeated. And so on until the fault is localized in the smallest functionally distinguishable stage, for example, in the output stage, video or IF amplifier, frequency divider, decoder or separate logic element.

Example 1. Radio receiver (Fig. 38.1)

The most appropriate first division of the radio receiver circuit is the division into the AF section and the IF/RF section. First, the AF section is checked: a signal with a frequency of 1 kHz is supplied to its input (volume control) through an isolation capacitor (10-50 μF). A weak or distorted signal, as well as its complete absence, indicates a malfunction of the AF section. We now divide this section into two subsections: the output stage and the preamplifier. Each subsection is checked starting from the output. If the AF section is working properly, then a pure tone signal (1 kHz) should be heard from the loudspeaker. In this case, the fault must be looked for inside the IF/RF section.

Rice. 38.1.

You can very quickly verify the serviceability or malfunction of the AF section using the so-called "screwdriver" test. Touch the end of a screwdriver to the input terminals of the AF section (after setting the volume control to maximum volume). If this section is working properly, the loudspeaker hum will be clearly audible.

If the fault is determined to be within the IF/RF section, it should be divided into two subsections: the IF section and the RF section. First, the IF section is checked: an amplitude-modulated (AM) signal with a frequency of 470 kHz 1 is supplied to its input, i.e., to the base of the transistor of the first amplifier 1 through an isolation capacitor with a capacity of 0.01-0.1 μF. FM receivers require a frequency modulated (FM) test signal at 10.7 MHz. If the IF section is working properly, a clean tone signal (400-600 Hz) will be heard in the loudspeaker. Otherwise, you should continue the procedure of splitting the IF section until a faulty cascade is found, for example an amplifier or detector.

If the fault is within the RF section, then this section is divided into two subsections if possible and checked as follows. An AM signal with a frequency of 1000 kHz is supplied to the input of the cascade through an isolation capacitor with a capacity of 0.01-0.1 μF. The receiver is configured to receive a radio signal with a frequency of 1000 kHz, or a wavelength of 300 m in the mid-wave range. In the case of an FM receiver, a test signal of a different frequency is naturally required.

You can also use an alternative verification method - method of step-by-step signal transmission testing. The radio turns on and tunes in to a station. Then, starting from the output of the device, an oscilloscope is used to check the presence or absence of a signal at the control points, as well as the compliance of its shape and amplitude with the required criteria for a working system. When troubleshooting some other electronic device, a nominal signal is applied to the input of that device.

The discussed principles of dynamic tests can be applied to any electronic device, provided that the system is correctly partitioned and the parameters of the test signals are selected.

Example 2: Digital frequency divider and display (Fig. 38.2)

As can be seen from the figure, the first test is performed at the point where the circuit is divided into approximately two equal parts. To change the logical state of the signal at the input of block 4, a pulse generator is used. The light emitting diode (LED) at the output should change state if the clamp, amplifier and LED are working properly. Next, troubleshooting should continue in the dividers preceding block 4. The same procedure is repeated using a pulse generator until the faulty divider is identified. If the LED does not change its state in the first test, then the fault is in blocks 4, 5 or 6. Then the pulse generator signal should be applied to the input of the amplifier, etc.

Rice. 38.2.

Principles of static tests

This series of tests is used to determine the defective element in the cascade, the malfunction of which was established at the previous stage of testing.

1. Start by checking static modes. Use a voltmeter with a sensitivity of at least 20 kOhm/V.

2. Measure voltage only. If you need to determine the current value, calculate it by measuring the voltage drop across a resistor of a known value.

3. If direct current measurements do not reveal the cause of the malfunction, then and only then proceed to dynamic testing of the faulty cascade.

Testing a single-stage amplifier (Fig. 38.3)

Typically nominal values constant voltages at the control points of the cascade are known. If not, they can always be estimated with reasonable accuracy. By comparing the actual measured voltages with their nominal values, the defective element can be found. First of all, the static mode of the transistor is determined. There are three possible options here.

1. The transistor is in a cutoff state, not producing any output signal, or in a state close to cutoff (“goes” into the cutoff region in dynamic mode).

2. The transistor is in a state of saturation, producing a weak, distorted output signal, or in a state close to saturation (“goes” into the saturation region in dynamic mode).

$11.Transistor in normal static mode.

Rice. 38.3. Rated voltages:

V e = 1.1 V, V b = 1.72 V, V c = 6.37V.

Rice. 38.4. Resistor break R 3, transistor

is in cut-off state: V e = 0.3 V,

V b = 0.94 V, V c = 0.3V.

After the real operating mode of the transistor has been established, the cause of cutoff or saturation is determined. If the transistor is operating in normal static mode, the fault is due to the passage of an alternating signal (such a fault will be discussed later).

Cutoff

The cutoff mode of the transistor, i.e., the cessation of current flow, occurs when a) the base-emitter junction of the transistor has zero bias voltage or b) the current flow path is broken, namely: when the resistor breaks (burns out) R 3 or resistor R 4 or when the transistor itself is faulty. Typically, when the transistor is in cut-off state, the collector voltage is equal to the power supply voltage V CC . However, if the resistor breaks R 3, the collector “floats” and theoretically should have base potential. If you connect a voltmeter to measure the voltage at the collector, the base-collector junction falls into forward bias conditions, as can be seen in Fig. 38.4. Along the "resistor" circuit R 1 - base-collector junction - voltmeter” current will flow, and the voltmeter will show a small voltage value. This indication is entirely related to internal resistance voltmeter.

Similarly, when the cutoff is caused by an open resistor R 4, the emitter of the transistor “floats”, which theoretically should have the base potential. If you connect a voltmeter to measure the voltage at the emitter, a current flow path is formed with a forward bias of the base-emitter junction. As a result, the voltmeter will show a voltage slightly higher than the rated voltage at the emitter (Fig. 38.5).

In table 38.1 summarizes the malfunctions discussed above.

Rice. 38.5.Resistor breakR 4, transistor

is in cut-off state:

V e = 1.25 V, V b = 1.74 V, V c = 10 V.

Rice. 38.6.Transition short circuit

base-emitter, the transistor is in

cut-off state:V e = 0.48 V, V b = 0.48 V, V c = 10 V.

Note that the term “high V BE" means exceeding the normal forward bias voltage of the emitter junction by 0.1 - 0.2 V.

Transistor fault also creates cutoff conditions. The voltages at the control points depend in this case on the nature of the fault and the ratings of the circuit elements. For example, short circuit emitter junction (Fig. 38.6) leads to cutoff of transistor current and parallel connection of resistors R 2 and R 4 . As a result, the base and emitter potential is reduced to the value determined by the voltage divider R 1 – R 2 || R 4 .

Table 38.1. Cutoff conditions

Malfunction		Cause
1. V e V b V c V BE	Vac	Resistor break R 1
V e V b V c V BE	High Normal V CC Low	Resistor break R 4
V e V b V c V BE	Low Low Low Normal	Resistor break R 3

The collector potential in this case is obviously equal toV CC . In Fig. 38.7 considers the case of a short circuit between the collector and the emitter.

Other cases of transistor malfunction are given in table. 38.2.

Rice. 38.7.Short circuit between collector and emitter, transistor is in cut-off state:V e = 2.29 V, V b = 1.77 V, V c = 2.29 V.

Table 38.2

Malfunction		Cause
V e V b V c V BE	0 Normal V CC Very high, cannot be kept functioning pn-transition	Base-emitter junction break
V e V b V c V BE	Low Low V CC Normal	Discontinuity of the base-collector transition

Saturation

As explained in Chap. 21, the transistor current is determined by the forward bias voltage of the base-emitter junction. A small increase in this voltage leads to a strong increase in the transistor current. When the current through the transistor reaches its maximum value, the transistor is said to be saturated (in a state of saturation). Potential

Table 38.3

Malfunction		Cause
1. V e V b V c	High ( V c) High Low	Resistor break R 2 or low resistor resistanceR 1
V e V b V c	Low Very low	Capacitor short circuitC 3

The collector voltage decreases with increasing current and, when saturation is reached, is practically equal to the emitter potential (0.1 - 0.5 V). In general, at saturation, the potentials of the emitter, base and collector are approximately at the same level (see Table 38.3).

Normal static mode

The coincidence of the measured and nominal DC voltages and the absence or low level of the signal at the amplifier output indicate a malfunction associated with the passage of an alternating signal, for example, an internal break in the coupling capacitor. Before replacing a capacitor suspected of a break, make sure it is faulty by connecting a working capacitor of a similar rating in parallel with it. Break in the decoupling capacitor in the emitter circuit ( C 3 in the diagram in Fig. 38.3) leads to a decrease in the signal level at the amplifier output, but the signal is reproduced without distortion. A large leak or short in this capacitor will usually change the DC behavior of the transistor. These changes depend on the static modes of previous and subsequent cascades.

When troubleshooting, you need to remember the following.

1. Do not make hasty conclusions based on a comparison of the measured and nominal voltages at only one point. It is necessary to record the entire set of measured voltage values ​​(for example, at the emitter, base and collector of the transistor in the case of a transistor cascade) and compare it with the set of corresponding nominal voltages.

2. With accurate measurements (for a voltmeter with a sensitivity of 20 kOhm/V, an accuracy of 0.01 V is achievable), two identical readings at different test points in the vast majority of cases indicate a short circuit between these points. However, there are exceptions, so all further checks must be performed to reach a final conclusion.

Features of diagnostics of digital circuits

In digital devices, the most common fault is the so-called “sticking”, when a logic 0 (“constant zero”) or a logical 1 (“constant one”) level is constantly present at an IC pin or circuit node. Other faults are also possible, including broken IC pins or short circuits between PCB conductors.

Rice. 38.8.

Diagnosis of faults in digital circuits is carried out by applying logical signals pulse generator to the inputs of the element being tested and observing the impact of these signals on the state of the outputs using a logic probe. To fully check a logical element, its entire truth table is “traversed”. Consider, for example, the digital circuit in Fig. 38.8. First, the logical states of the inputs and outputs of each logic gate are recorded and compared with the states in the truth table. The suspicious logic element is tested using a pulse generator and a logic probe. Consider, for example, a logic gate G 1 . At its input 2, a logical level of 0 is constantly active. To test the element, the generator probe is installed at pin 3 (one of the two inputs of the element), and the probe probe is installed at pin 1 (the output of the element). Referring to the truth table of the NOR element, we see that if one of the inputs (pin 2) of this element has a logical level of 0, then the signal level at its output changes when the logical state of the second input (pin 3) changes.

Element truth tableG 1

Conclusion 2	Conclusion 3	Conclusion 1

For example, if in the initial state there is a logical 0 at pin 3, then at the output of the element (pin 1) there is a logical 1. If you now use a generator to change the logical state of pin 3 to logical 1, then the output signal level will change from 1 to 0, which and register the probe. The opposite result is observed when, in the initial state, logical level 1 operates at pin 3. Similar tests can be applied to other logical elements. During these tests, it is imperative to use the truth table of the logical element being tested, because only in this case can you be sure of the correctness of the testing.

Features of diagnostics of microprocessor systems

Diagnosing faults in a bus-structured microprocessor system takes the form of sampling the sequence of addresses and data that appears on the address and data buses and then comparing them with a well-known sequence for the running system. For example, a fault such as a constant 0 on line 3 (D 3) of the data bus will be indicated by a constant logic zero on line D 3. The corresponding listing, called condition listing, obtained using a logic analyzer. A typical status listing displayed on the monitor screen is shown in Fig. 38.9. Alternatively, a signature analyzer can be used to collect a stream of bits, called a signature, at some circuit node and compare it to a reference signature. The difference between these signatures indicates a malfunction.

Rice. 38.9.

This video talks about a computer tester for diagnosing faults personal computers IBM PC type:

Microcircuits are the closest thing to being called a “black box” - they are truly black, and their insides remain a mystery to many.

Today we will lift this veil of secrecy, and sulfuric and nitric acid will help us in this.

Attention! Any operations with concentrated (and especially boiling) acids are extremely dangerous, and you can only work with them using appropriate protective equipment (gloves, goggles, apron, hood). Remember, we only have 2 eyes, and one drop is enough for each: therefore, everything that is written here is not worth repeating.

Opening

We take the microcircuits we are interested in and add concentrated sulfuric acid. Bring to a boil (~300 degrees), do not stir :-) Baking soda is poured at the bottom to neutralize the spilled acid and its vapors.

After 30-40 minutes, carbon remains from the plastic:

We take it out and choose what will go for another life-giving acid bath, and what is already ready:

If pieces of carbon are firmly stuck to the crystal, they can be removed with boiling concentrated nitric acid (but the temperature here is much lower, ~110-120C). Dilute acid will eat up the metallization, so concentrated acid is needed:

Let's look

Pictures are clickable (5-25MB JPEGs). Some of you may have already seen some of my photos.
Colors are traditionally “enhanced” to the maximum - in reality the riot of colors is much less.

PL2303HX- USB converter<>RS232, these are used in all sorts of Arduino and others like them:

LM1117- linear power regulator:

74HC595- 8-bit shift register:

NXP 74AHC00
74AHC00 - 4 NAND (2AND-NOT) elements. Looking at the gigantic crystal size (944x854 µm) it becomes obvious that the “old” micron technologies are still in use. It is interesting to see the abundance of “reserve” vias to increase the yield.

Micron MT4C1024- dynamic memory chip, 1 Mebibit (2 20 bits). Used during the times of 286 and 386. Crystal size - 8662x3969µm.

AMD Palce16V8h
GAL (Generic array logic) chips are the predecessors of FPGA and CPLD.
AMD Palce16V8h is a 32x64 array of AND elements.
Crystal size - 2434x2079µm, 1µm technology.

ATtiny13A- one of the smallest Atmel microcontrollers: 1kb of flash memory and 32 bytes of SRAM. Crystal size - 1620x1640 µm. Technological standards - 500nm.

ATmega8- one of the most popular 8-bit microcontrollers.
Crystal size - 2855x2795µm, technological standards 500nm.

KR580IK80A(later renamed KR580VM80A) is one of the most popular Soviet processors.

It turned out that, contrary to popular belief, it is not a layer-by-layer copy of the Intel 8080/8080A (some blocks are similar, but the layout and location of the contact pads are significantly different).

The thinnest lines are 6µm.

STM32F100C4T6B- the smallest microcontroller based on the ARM Cortex-M3 core produced by STMicroelectronics. Crystal size - 2854x3123µm.

Altera EPM7032- CPLD has seen a lot, and is one of the few that worked on 5V power. Crystal size - 3446x2252µm, technological standards 1µm.

The black box is now open :-)
PS. If you have microcircuits of historical significance (for example, T34VM1, Soviet 286, foreign chips that are old and unique for their time), send them and we’ll see what’s inside.

Photos are distributed under license

Electronics accompanies modern man 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 conducting repairs is the so-called method of elimination. 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 exact location breakdowns. 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.

If mechanical components are worn out by friction, then 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 detailed description locks 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, short circuit in the power supply and in the power section, and others possible malfunctions, which 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 bear 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. Peculiarities external examination in this case, it involves combining the search for the possible cause of the failure with carrying out preventive maintenance. 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 way repair is a 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, ROM with different versions firmware 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.

In this article we will talk about microcircuits, what types there are, how they are designed and where they are used. In general, in modern electronic technology it is difficult to find a device that does not use microcircuits. Even the cheapest Chinese toys use various planar, compound-filled chips that are assigned control functions. Moreover, every year they become more and more complex on the inside, but easier to operate and smaller in size on the outside. We can say that there is a constant evolution of microcircuits.

A microcircuit is an electronic device or part of it capable of performing a particular task. If it were necessary to solve such a problem, which is solved by many microcircuits, using discrete elements, using transistors, then the device, instead of a small rectangle measuring 1 centimeter by 5 centimeters, would occupy an entire cabinet and would be much less reliable. But this is what they looked like computing machines half a hundred years ago!

Electronic control cabinet - photo

Of course, for a microcircuit to operate, it is not enough to simply supply power to it; you also need a so-called " body kit”, that is, those auxiliary parts on the board, together with which the microcircuit can perform its function.

Chip body kit - drawing

In the figure above, the microcircuit itself is highlighted in red; all other parts are its " body kit" Very often, microcircuits heat up during their operation; these can be microcircuits for stabilizers, microprocessors and other devices. In this case, to prevent the microcircuit from burning out, it must be attached to a radiator. Microcircuits that must heat up during operation are designed immediately with a special heat sink plate - a surface usually located on the back side of the microcircuit, which must fit tightly to the radiator.

But in the connection, even with a carefully polished radiator and plate, there will still be microscopic gaps, as a result of which heat from the microcircuit will be less efficiently transferred to the radiator. In order to fill these gaps, heat-conducting paste is used. The same one that we apply to the computer processor before fixing the radiator on top of it. One of the most widely used pastes is KPT–8.

Amplifiers on microcircuits can be soldered in literally 1-2 evenings, and they begin to work immediately, without the need for complex setup and highly qualified tuners. Separately, I would like to say about car amplifier microcircuits; sometimes there are literally 4-5 parts from a body kit. To assemble such an amplifier, with some care, you don’t even need a printed circuit board (although it is desirable) and you can assemble everything using a surface-mounted installation, directly on the pins of the microcircuit.

True, after assembly, it is better to immediately place such an amplifier in a housing, because such a design is unreliable, and in the event of an accidental short circuit of the wires, the microcircuit can easily be burned. Therefore, I recommend that all beginners spend a little more time making a printed circuit board.

Regulated power supplies based on stabilizer chips are even easier to manufacture than similar ones based on transistors. Look how many parts a simple LM317 microcircuit replaces:

Microcircuits on printed circuit boards in electronic devices can be soldered either directly to print tracks or placed in special sockets.

Socket for deep chip - photo

The difference is that in the first case, in order to replace the microcircuit, we will have to desolder it first. And in the second case, when we put the microcircuit in the socket, we just need to remove the microcircuit from the socket, and it can be easily replaced with another one. A typical example of replacing a microprocessor in a computer.

Also, for example, if you are assembling a device on a microcontroller on a printed circuit board, and have not provided for in-circuit programming, you can, if you soldered into the board not the chip itself, but the socket into which it is inserted, then the chip can be removed and connected to a special programmer board .

Such boards already have sockets soldered into different microcontroller housings for programming.

Analog and digital microcircuits

Microcircuits are produced various types, they can be either analog or digital. The former, as the name implies, work with an analog signal form, while the latter work with a digital signal form. An analog signal can take different forms.

A digital signal is a sequence of ones and zeros, high and low level signals. A high level is ensured by applying 5 volts or a voltage close to it to the pin, a low level is the absence of voltage or 0 volts.

There are also microcircuits ADC (analog to digital converter) And DAC (digital - analog converter) which converts the signal from analog to digital, and vice versa. A typical example of an ADC is used in a multimeter to convert measured electrical quantities and display them on the multimeter's screen. In the figure below, the ADC is a black drop with tracks approaching from all sides.

Microcontrollers

Relatively recently, in comparison with the production of transistors and microcircuits, the production of microcontrollers was launched. What is a microcontroller?

This is a special chip, can be produced in both Dip so in SMD execution, in the memory of which a program can be written, the so-called Hex file. This is a compiled firmware file that is written in a special editor program code. But it’s not enough to write the firmware; you need to transfer it, flash it into the microcontroller’s memory.

Programmer - photo

Serves for this purpose programmer. As many people know, there are many different types microcontrollers - AVR, PIC and others, for different types we need different programmers. There is also, and everyone will be able to find and make one that is suitable for their level of knowledge and capabilities. If you don’t want to make a programmer yourself, you can buy a ready-made one in an online store or order it from China.

The figure above shows a microcontroller in an SMD package. What are the advantages of using microcontrollers? Previously, when designing and assembling a device using discrete elements or microcircuits, we specified the operation of the device through a specific, often complex connection on a printed circuit board using many parts. Now we just need to write a program for a microcontroller that will do the same thing programmatically, often faster and more reliably than a circuit without the use of microcontrollers. The microcontroller is whole computer, with I/O ports, the ability to connect a display and sensors, as well as control other devices.

Of course, the improvement of microcircuits will not stop there, and we can assume that in 10 years there will actually be microcircuits from the word " micro" - invisible to the eye, which will contain billions of transistors and other elements, several atoms in size - then the creation of the most complex electronic devices will really become accessible even to not very experienced radio amateurs! Our brief review has come to an end, we were with you AKV.

Discuss the article MICROCIRCUITS