Do-it-yourself UPS repair schemes

In detail: do-it-yourself UPS repair schemes from a real master for the site my.housecope.com.

A friend at the company threw out a non-working uninterruptible power supply of the APC 500 model. But before putting it into spare parts, I decided to try to revive it. And as it turned out, it was not in vain. First of all, we measure the voltage on the rechargeable gel battery. For the operation of the uninterruptible power supply, but must be within 10-14V. The voltage is normal, so there is no problem with the battery.

Now let's examine the board itself and measure the power supply at key points in the circuit. I did not find a native circuit diagram of the APC500 uninterruptible power supply, but here is something similar. For better clarity, download the complete schematic here. We check powerful tin transistors - the norm. The power supply to the electronic control part of the uninterruptible power supply comes from a small 15V mains transformer. We measure this voltage before the diode bridge, after, and after the 9V stabilizer.

And here is the first swallow. The voltage 16V after the filter enters the microcircuit - the stabilizer, and the output is only a couple of volts. We replace it with a model similar in voltage and restore the power supply to the control unit circuit.

The uninterruptible power supply began to crack and buzz, but it is still not observed at the 220V output. We continue to carefully examine the printed circuit board.

Another problem - one of the thin tracks burned out and had to be replaced with a thin wire. Now the APC500 uninterruptible power supply unit worked without problems.

Experiencing in real conditions, I came to the conclusion that the built-in sounder signaling the absence of a network screams like a bad one, and it would not hurt to calm it down a little. It is impossible to turn off completely - since the state of the battery in emergency mode will not be heard (determined by the frequency of signals), but you can and should make it quieter.

Video (click to play).

This is achieved by connecting a 500-800 ohm resistor in series with the sounder. And finally, a few tips for owners of uninterruptible power supplies. If it sometimes disconnects the load, the problem may be in the computer's power supply with dried out capacitors. Connect the UPS to the input of a known good computer and see if the operation stops.

An uninterruptible power supply sometimes incorrectly determines the capacity of lead-acid batteries, showing the OK status, but as soon as it switches to them, they suddenly sit down and the load is “knocked out”. Make sure the terminals fit snugly and not loose. Do not disconnect it from the network for a long time, making it impossible to keep the batteries on a constant recharge. Do not allow deep discharges of the batteries, leaving at least 10% of the capacity, after which the UPS should be turned off until the supply voltage is restored. At least once every three months, do a "workout" by discharging the battery to 10% and recharging the battery to full capacity.

Uninterruptible voltage supplies use a closed helium or acid battery. The built-in battery is usually designed for a capacity of 7 to 8 Amperes / hour, voltage - 12 volts. The battery is completely sealed, which allows you to use the device in any condition. In addition to the battery, inside you can see a huge transformer, in this case, 400-500 watts. The transformer operates in two modes -

1) as a step-up transformer for a voltage converter.

2) as a step-down mains transformer for charging the built-in battery.

During normal operation, the load is supplied by the filtered mains voltage. Filters are used to suppress electromagnetic and interference in the input circuits. If the input voltage falls below or above the set value or disappears altogether, the inverter turns on, which is normally off.By converting the DC voltage of the batteries into AC, the inverter supplies the load from the batteries. BACK UPS of the Off-line class operate uneconomically in power grids with frequent and significant voltage deviations from the nominal value, since frequent switching to battery operation reduces the service life of the latter. The power produced by the manufacturers of Back-UPS is in the range of 250-1200 VA. The scheme of the uninterruptible voltage source BACK UPS is rather complicated. In the archive you can download a large collection of schematic diagrams, and below are several reduced copies - click to enlarge.

Here you can find a special controller that is responsible for the correct operation of the device. The controller activates the relay when the mains voltage is absent and if the UPS is on, then it will work as a voltage converter. If the mains voltage reappears, the controller turns off the converter and the device turns into a charger. The capacity of the built-in battery can be enough for up to 10 - 30 minutes, if, of course, the device powers the computer. You can read more about the operation and purpose of UPS nodes in this book.

BACK UPS can be used as a backup power source; in general, it is recommended that every home has an uninterruptible power supply. If the uninterruptible power supply is intended for household needs, then it is advisable to remove the signaling device from the board, it reminds that the device works as a converter, it makes a reminder with a squeak every 5 seconds, and this is boring. The output of the converter is pure 210-240 volts 50 hertz, but as for the pulse shape, there is clearly not a pure sine. BACK UPS can power any household appliances, including active ones, of course, if the power of the device allows it.

APC Off-line UPS includes Back-UPS models. UPSs of this class are distinguished by their low cost and are designed to protect personal computers, workstations, network equipment, trade and point-of-sale terminals. The power of the manufactured Back-UPS models is from 250 to 1250 VA. The main technical data of the most common UPS models are presented in Table 1.

Table 1. Main technical data of UPS class Back-UPS

The index "I" (International) in the names of UPS models means that the models are designed for an input voltage of 230 V, the devices are equipped with sealed lead-acid batteries with a service life of 3 ... 5 years according to the Euro Bat standard. All models are equipped with suppressor filters that suppress surges and high-frequency noise in the mains voltage. The devices give appropriate sound signals when the input voltage is lost, the batteries are discharged and overloaded. The utility voltage threshold below which the UPS switches to battery operation is set using the switches on the rear of the unit. Models BK400I and BK600I have an interface port that can be connected to a computer or server for automatic self-closing of the system, a test switch and a beep switch.

A schematic diagram of the Back-UPS 250I, 400I and 600I is shown almost completely in Fig. 2-4. The multi-tier power supply noise suppression filter consists of varistors MOV2, MOV5, chokes L1 and L2, capacitors C38 and C40 (Fig. 2). Transformer T1 (Fig. 3) is an input voltage sensor.

Its output voltage is used for battery charging (this circuit uses D4 ... D8, IC1, R9 ... R11, C3 and VR1) and analysis of the mains voltage.

If it disappears, then the circuit on the elements IC2 ... IC4 and IC7 connects a powerful inverter, powered by a battery. The ACFAIL command to turn on the inverter is generated by IC3 and IC4. The circuit, consisting of comparator IC4 (pins 6, 7, 1) and electronic key IC6 (pins 10, 11, 12), enables the operation of the inverter with a log signal. "1" going to pins 1 and 13 of IC2.

The divider, consisting of resistors R55, R122, R1 23 and switch SW1 (pins 2, 7 and 3, 6), located on the rear side of the UPS, determines the mains voltage below which the UPS switches to battery power. The factory setting for this voltage is 196 V. In areas with frequent fluctuations in the mains voltage resulting in frequent UPS switches to battery power, the threshold voltage should be set to a lower level. The fine adjustment of the threshold voltage is performed by the VR2 resistor.

All Back-UPS models, with the exception of the BK250I, have a bi-directional communication port for communication with a PC. Power Chute Plus software allows the computer to both monitor the UPS and safely shutdown the operating system (Novell, Netware, Windows NT, IBM OS / 2, Lan Server, Scounix and UnixWare, Windows 95/98) while saving user files. In fig. 4 this port is designated as J14. Purpose of its findings:

1 - UPS SHUTDOWN. The UPS shuts down if a log appears on this pin. "1" for 0.5 s.

2 - AC FAIL. When switching to battery power, the UPS generates a log on this output. "one".

3 - CC AC FAIL. When switching to battery power, the UPS generates a log on this output. "0". Open collector output.

4, 9 - DB-9 GROUND. Common wire for signal input / output. The terminal has a resistance of 20 ohms with respect to the common wire of the UPS.

5 - CC LOW BATTERY. In the event of a battery discharge, the UPS generates a log on this output. "0". Open collector output.

6 - OS AC FAIL When switching to battery power, the UPS generates a log on this output. "one". Open collector output.

Open collector outputs can be connected to TTL circuits. Their load capacity is up to 50 mA, 40 V. If you need to connect a relay to them, then the winding should be shunted with a diode.

A normal "null modem" cable is not suitable for this port, the corresponding RS-232 interface cable with a 9-pin connector is supplied with the software.

To set the frequency of the output voltage, connect an oscilloscope or frequency meter to the UPS output. Turn the UPS into battery mode. When measuring the frequency at the UPS output, adjust the VR4 resistor to set 50 ± 0.6 Hz.

Turn the UPS into battery mode without load. Connect a voltmeter to the UPS output to measure the effective voltage value. By adjusting the VR3 resistor, set the voltage at the UPS output to 208 ± 2 V.

Set switches 2 and 3 on the rear of the UPS to OFF. Connect the UPS to a LATR-type transformer with continuously variable output voltage. Set the voltage at the LATR output to 196 V. Turn the VR2 resistor counterclockwise until it stops, then slowly turn the VR2 resistor clockwise until the UPS switches to battery power.

Set the UPS input to 230 V. Disconnect the red wire to the positive battery terminal. Using a digital voltmeter, adjust the VR1 resistor to set the voltage on this wire to 13.76 ± 0.2 V relative to the common point of the circuit, then restore the connection to the battery.

Typical malfunctions and methods for their elimination are given in table. 2, and in table. 3 - analogs of the most frequently failing components.

Table 2. Typical Back-UPS 250I, 400I and 600I Faults

The function performed by the uninterruptible power supply (abbreviated - UPS, or UPS - from the English Uninterruptible Power Supply) is fully reflected in its very name. As an intermediate link between the mains and the consumer, the UPS must maintain the power supply to the consumer for a certain time.

Uninterruptible Power Supplies indispensable in cases where the consequences of a power outage can be extremely unpleasant: for backup power supply of computers, video surveillance systems, circulation pumps of heating systems.

More about UPS

The principle of operation of any uninterruptible power supply is simple: as long as the mains voltage is within the specified limits, it is supplied to the UPS output, while the charge of the built-in battery is maintained from an external power supply by the charging circuit.In the event of a power failure or a strong deviation from the rating, the UPS output is connected to its built-in inverter, which converts direct current from the battery into alternating current to supply the load. Naturally, UPS runtime is limited by battery capacity, inverter efficiency and load capacity.

There are three design types of uninterruptible power supplies:

We offer you to familiarize yourself with the UPS device using the example of the APC Back-UPS RS800 model

Since uninterruptible power supplies are mainly used to back up computers, they often have USB ports for connecting to a PC, which allows the computer to automatically go into a low power mode when switching to backup power. To do this, simply connect the UPS to an available port on the computer and install the drivers from the included disk. Old models of uninterruptible power supplies can use a COM port for this, which has practically disappeared on a PC.It must be remembered that the power of the load in watts connected to the uninterruptible power supply must be at least one and a half times less than its rated power in volt-amperes, multiplied by 0.7 (power factor, which determines the losses in the source itself) to prevent overloading the inverter. For example, an inverter with a power of 1 kVA can supply a load of no more than 470 watts without overloading, and up to 700 watts at its peak.An example of a possible connection diagram: Image - DIY UPS repair schemes

Since the batteries built into the UPS are automatically kept charged, no need for additional charging... If the battery has been completely discharged, a number of UPS models at the moment of switching on may indicate a battery malfunction, however, as it gets charged, the indication will stop.

Typically, when the UPS is turned on for the first time, it needs 5-6 hours to fully charge the battery. A number of operating nuances depend on the type of battery used:

The cheapest batteries made using AGM technology (mistakenly or deliberately can be called gel by sellers) are not recommended to be left discharged for a long time, as this leads to their degradation and loss of capacity. If the UPS is not being used for a long time, it is a good idea to run it idle regularly to maintain the battery charge.
Real gel batteries are more expensive, but they tolerate prolonged deep discharge without consequences. At the same time, they are more sensitive to overcharging, which can occur if batteries with a capacity less than designed are installed in the UPS.

If there is a need to charge the battery from an external charging source, it is extremely important to limit the charging current to no more than 10% of the nominal capacity (for example, a 4 A * h battery can be charged with a current of no more than 0.4 A).

The main failure of the uninterruptible power supply that you have to deal with is due to the fact that UPS does not go offline... It can be caused by the following reasons:

Subject to the rules for operating an uninterruptible power supply, all its maintenance will be reduced to the timely replacement of batteries.

The complete lack of information about such common devices as uninterruptible power supplies is surprising. We are breaking through the information blockade and are starting to publish materials on their construction and repair. From the article you will get a general idea of the existing types of UPS and a more detailed, at the level of a schematic diagram, about the most common Smart-UPS models.
The reliability of computers is largely determined by the quality of the electrical network. Power interruptions, such as surges, booms, sags, and power outages, can result in keyboard locks, data loss, system board damage, and more. Uninterruptible power supplies (UPS) are used to protect high-value computers from mains-related troubles.The UPS eliminates problems associated with poor quality power or temporary lack of power, but is not a long-term alternative power source like a generator.

Rice. 1. Block diagram of an off-line UPS

Rice. 2. Block diagram of a Line-interactive UPS

Rice. 3. Block diagram of the UPS class On-line

Rice. 5. Input circuits

Rice. 6. Turn on the processor

Rice. 7. Output inverter

An uninterruptible power supply can deal with the following power problems: complete disconnection of the supply network, high-voltage impulse noise, long-term and short-term voltage surges; high-frequency noise or interference occurring in the mains, frequency deviation of more than 3 Hz.

Important parameters of the UPS are the time of transferring the load to power supply from the storage batteries and the time of autonomous operation from the storage battery.

Redundant UPS design in the operating mode, the load is powered from the electrical network, which the uninterruptible power supply filters for high-voltage pulses and electromagnetic interference with passive filters.

When the mains voltage deviates beyond the standardized values, the load is automatically connected to battery power using the inverter circuit, which is available in each UPS. As soon as the mains voltage returns to normal, the uninterruptible power supply will switch the load to mains power.

UPS interactive diagram is similar to the backup circuit, but in addition, a step voltage stabilizer based on an autotransformer is installed at the input, which makes it possible to regulate the output voltage. During normal operation, the UPS operating on the interactive circuit does not regulate the frequency, but in the absence of voltage, it starts to be powered by an inverter with a battery. The advantage of this scheme is the shorter switching times. In addition, the inverter is synchronized with the input voltage.

UPS double conversion circuit works as follows: Input AC voltage is converted to DC, then using the inverter back to AC. In the absence of an input voltage, the load is switched to power supply from the batteries instantly, since the batteries are permanently connected to the circuit.

The main blocks and nodes that can be part of the UPS:

Input mains voltage 220V, 50Hz is supplied through the switching device and the mains filter to the charger. The mains filter is necessary to exclude the ingress of noise into the mains, the charger charges the battery provided the mains voltage is available.

The inverter is part of any UPS. It is built on the basis of a semiconductor converter of AB DC voltage into AC voltage supplied to the load. The inverter often combines the functions of both the actual inverter and the charger. Depending on the type of UPS, the inverter generates different voltage shapes

Bypass is a switching device. This device is used to directly link the input and output of the UPS, excluding the power redundancy scheme.

The bypass performs the following functions:

turn the UPS on or off

transfer of the load from the inverter to the bypass in case of overloads and short circuits at the output

transfer of the load from the inverter to the bypass in order to reduce power losses

The static bypass is assembled on the basis of a thyristor switch made of counter-parallel connected thyristors. Key management comes from the UPS management system

The switching power supply was taken ready-made for 28 V, 50A, but you can assemble and there are a great many circuits yourself. Two 12-volt car batteries connected in series are connected to the switching power supply. The inverter was also used ready-made, because the price of its components is almost two times higher than the finished device.This UPS is enough for almost a day the energy consumption of a small private house. In the event of a long shutdown, and this often happens in our Siberian expanses, I turn on the diesel generator for 6 hours.

Our UPS is designed for the following capabilities: direct conversion from 12 VDC to 220 VAC at 50 Hz. The maximum power of this UPS circuit is 220 W. The reverse conversion is used to charge the battery. The charge current is 6 A. The circuit provides fast switching from direct conversion to reverse mode.

A clock generator is made on the radio components VT3, VT4, R3 ... R6, C5, C6, which generates pulses with a repetition rate of 50 Hz. The generator sets the operating mode of the bipolar transistors VT1, VT6. Windings IIa, IIb of the transformer are connected to their collector circuit. The mains filter is assembled on the passive components C1, C2, L1, and the clock generator filter on the radio elements VD1, C3, C4.

As a transformer, you can use any transformer, with two voltages of 10V and with a load current of up to 10 A. The L1 coil is assembled on a K28x16x9 M2000NM ferrite ring. We wrap the ring with varnished cloth, and then we wind 10 turns of wire with a diameter of 0.55 ... 0.70 mm. for 2 windings.

In urban conditions, the need for backup sources rarely arises, but in the realities of rural areas, power outages often occur. In this situation, emergency power from a car battery with a voltage converter from 12 to 220 volts can help. The reserve capacity of a good battery is enough for hours of backup power supply for your apartment.

DIAGRAM UPS REPAIR DESCRIPTION

A UPS is a very complex device that can be conditionally divided into two units - a converter and a charger that performs the opposite function. In most cases, UPS repair is very problematic and expensive. But it's still worth trying - sometimes the problem is simple and literally lies on the surface.

The company threw out the non-working uninterruptible power supply of the APC500 model. But before putting it into spare parts, I decided to try to revive it. And as it turned out, it was not in vain. First of all, we measure the voltage on the rechargeable gel battery. For the UPS to function, it must be in the range of 10-14 V. The voltage is normal, so the problem with the battery disappears.

Now let's examine the board itself and measure the power supply at key points in the circuit. I did not find a native circuit diagram of the APC500 uninterruptible power supply, but here is something similar. For better clarity, download the complete schematic here. We check powerful field-effect transistors - the norm. The power supply to the electronic control part of the uninterruptible power supply comes from a small 15 V mains transformer. We measure this voltage before the diode bridge, after and after the 9 V stabilizer.

And here is the deviation. A voltage of 16 V after the filter enters the microcircuit - a stabilizer, and at the output there is only a couple of volts. We replace it with a model similar in voltage and restore the power supply to the control unit circuit.

Another problem - one of the thin tracks burned out and had to be replaced with a thin wire. Now the APC500 uninterruptible power supply unit worked without problems.

The UPS sometimes incorrectly determines the capacity of the lead batteries showing the OK status, but as soon as it switches to them, they suddenly go down and the load is “knocked out”. Make sure the terminals fit snugly and not loose. Do not disconnect it from the network for a long time, making it impossible to keep the batteries on a constant recharge. Avoid deep discharges of the batteries, leaving at least 10% capacity, then turn off the UPS until the supply voltage is restored.

I have a Value 600E uninterruptible power supply for my computer, I bought it for a long time, it served correctly, although I changed the battery several times, but this is normal. And then the moment came, in the morning, as usual, I wanted to turn it on in order to work at the computer, but the uninterruptible power supply did not turn on, in response, there is not even a squeak, the relays do not click.

I had to untwist and figure out what happened.

value-600e indicated places for self-tapping screws

I checked the mains voltage, then the battery is all right. I completely unscrewed the board to make an external inspection, but everything was fine. I began to ring the chain and as a result I discovered broken capacitor 0.01 μF 250V on the C4 circuit (103k) and in cliff resistor 1.5 kOhm 2W in R5

I made a screen from the diagram (below is a link to the complete schematic diagram of the Value 600E) indicated the culprits with red arrows:

I replaced the burnt out elements, I put it on and it worked (repaired), I hope my experience will be useful.

admission: on the capacitor such marking is F .01J / PD 250V

Most modern consumer electronic equipment has in its design independent or located on a separate board electronic modules that reduce and rectify the mains voltage.

There are several reasons for this, but the main ones are:

fluctuations in the mains voltage, for which these step-down-rectifier devices are not designed;
non-observance of operating rules;
connecting a load for which the devices are not designed.

Of course, it can be very offensive when you need to do urgent work, and the power module of the computer is faulty, or while watching your favorite TV show, this device fails.

Do not immediately panic and go to a repair shop or rush to an electronics supermarket to purchase a new unit. Often, the reasons for inoperability are so trivial that they can be eliminated at home, with minimal expenditure of financial resources and nerves.

Of course, in order to try not only to repair the switching power supply, but also to determine its malfunction, you must have basic knowledge of electronics and have certain electrical skills.

As part of any power supply, whether built-in, like in a TV or installed as a separate device, like in a desktop computer, there are two functional blocks - high-voltage and low-voltage.

In the high-voltage side, the mains voltage is converted by the diode bridge into a constant voltage, and smoothed on the capacitor to the level of 300.0 ... 310.0 volts. Constant, high voltage is converted into a pulse voltage with a frequency of 10.0 ... 100.0 kilohertz, which makes it possible to abandon massive low-frequency step-down transformers, replacing them with small-sized pulse ones.

In the low-voltage unit, the impulse voltage is lowered to the required level, straightened, stabilized and smoothed out. At the output of this unit, there is one or more voltages required to power household appliances. In addition, various control circuits are mounted in the low-voltage unit, which make it possible to increase the reliability of the device and ensure the stability of the output parameters.

Visually, on a real board, it is quite easy to distinguish between the high-voltage and low-voltage parts. The network wires are suitable for the first, and the supply wires go from the second.

Switching regulator in the transistor power supply

A person who is going to try to repair a power supply unit for household electronic equipment must be prepared in advance that not every power supply device can be repaired. Today, some manufacturers produce electronics, the blocks of which are not subject to repair, but complete replacement.

Not a single master will undertake the repair of such a power supply unit, because initially it is intended for the complete dismantling of the old device with replacement with a new one. Often, such electronic devices are simply filled with some kind of compound, which immediately removes the question of its maintainability.

As statistics show, the main malfunctions of the power supply are caused by:

malfunction of the high-voltage part (40.0%), which are expressed by the breakdown (burnout) of the diode bridge and the failure of the filter capacitor;
breakdown of a power field-effect or bipolar transistor (30.0%), which forms high-frequency pulses and is located in the high-voltage part;
breakdown of the diode bridge (15.0%) in the low-voltage part;
breakdown (burnout) of the choke windings of the output filter.

In other cases, the diagnosis is quite difficult and without special devices (oscilloscope, digital voltmeter) it will not be possible to perform it. Therefore, if the malfunction of the power supply is not caused by the four above-mentioned main reasons, you should not engage in home repairs, but immediately call a master for replacement or purchase a new power supply device.

Faults in the high-voltage section are easy enough to detect. They are diagnosed by a blown fuse and a lack of voltage after it. The third and fourth cases can be assumed if the fuse is good, the voltage at the input of the low-voltage unit is present, and the input voltage is absent.

It is advisable to check all the details at the same time. If several electronic elements are burned out, when one of them is replaced with a serviceable one, it may burn out again due to a complex malfunction that has not been eliminated.

After replacing parts, you must install a new fuse and turn on the power supply. As a rule, after this, the power supply begins to work.

If the fuse has not blown, and there is no voltage at the output of the power supply, then the cause of the malfunction is the breakdown of the rectifier diodes of the low-voltage part, the burnout of the inductor or the output of the electrolytic capacitors of the secondary rectifier unit.

Malfunction of capacitors is diagnosed when they are swollen or fluid leaks out of their body. The diodes must be evaporated and checked with a tester in the same way as checking the high-voltage part. The integrity of the choke winding is checked by a tester. All defective parts must be replaced.

If you cannot find the desired choke, then some "craftsmen" rewind the burned-out one, picking up a wire of a suitable diameter and determining the number of turns. Such work is quite painstaking and is usually performed only for unique power supplies, it is difficult to find an analogue for which.

As already mentioned, most power supplies for modern computers and TVs are built according to a typical scheme. They differ in the size of the electronic parts used and in the output power. The diagnostics and troubleshooting procedures for these devices are identical.

However, a high-quality repair requires an appropriate tool, the range of which includes:

soldering iron (preferably with adjustable power);
solder, flux, alcohol or refined gasoline (Galosha);
device for removing molten solder (desoldering pump);
Screwdriver Set;
side cutters (nippers);
household multimeter (tester)
tweezers;
100.0 watt incandescent lamp (used as ballast load).

In principle, simple TVs can be repaired without a circuit, but the main difficulty in repairing some models is that the power supply device generates the entire range of voltages - including the high-voltage used to scan the kinescope.The power supplies for household computers are made according to the same type of scheme. Let us consider separately the methodology for determining the malfunction and repairing the TV and desktop.

The failure of the TV power supply module is first of all evidenced by the absence of the "sleep" mode diode glow. The first repair operations are:

check for the integrity (absence of breakage) of the supply voltage cord;

disassembly of the television receiver and release of the electronic board;

inspection of the power supply board for the presence of externally faulty parts (swollen capacitors, burnt spots on the printed circuit board, burst cases, charred surface of resistors);

checking the soldering points, with special attention paid to soldering the contacts of the pulse transformer.

If it was not possible to visually establish the defective part, then it is necessary to sequentially check the performance of the fuse, diodes, electrolytic capacitors and transistors. Unfortunately, if the control microcircuits are out of order, their malfunction can be established only indirectly - when, with completely serviceable discrete elements, the operational state of the power supply does not occur.The most common reasons for the inoperability of television units are:

breakage of ballast resistance;

inoperability (short circuit) of the high voltage filter capacitor;

malfunction of the secondary voltage filter capacitors;

breakdown or burnout of rectifier diodes.

All these parts (except for rectifier diodes) can be checked without removing them from the board. If it was possible to identify the faulty part, then it is replaced and they begin to check the repair performed. To do this, an incandescent lamp is installed in place of the fuse and the device is connected to the network.There are several possible options for the behavior of the repaired device:

The light flashes and goes out, the sleep mode LED lights up, a raster appears on the screen. In this situation, the line scan voltage is measured first. If its value is too high, it is necessary to check and replace electrolytic capacitors with guaranteed serviceable ones. A similar situation occurs in the event of a malfunction of the optocouplers.

If the lamp flashes and goes out, the LED does not light up, the raster is absent, then the pulse generator does not start. In this case, the voltage level on the electrolytic capacitor of the filter of the high-voltage part is checked. If it is below 280.0 ... 300.0 volts, then the following malfunctions are most likely:

one of the rectifier bridge diodes is broken;
large capacitor leakage (the capacitor is "old").

If there is no voltage, it is necessary to re-check the continuity of the supply circuits and all diodes of the high voltage rectifier. If the light is high, you must immediately disconnect the power module from the network and re-check all electronic parts.The above sequence and test scheme allow you to identify the main malfunctions of the power supply device of the television receiver. Image - DIY UPS repair schemes

Today, ATX devices of various power are most widely used for powering desktop (desktop) designers. The reason for their repair should be:

the motherboard does not start (the computer is completely inoperative);
the cooling fan of the device itself does not rotate;
the block “tries” to start itself many times.

Before starting the repair of ATX devices, it is necessary to assemble the load circuit (figure). The repair is carried out in the following sequence:

the device is removed from the computer and the cover is removed from it;
a vacuum cleaner and a brush removes dust from electronic boards and surfaces of parts;
external examination of electronic elements and printed circuit boards;
a load device is connected.

If, when turned on, the lamp flashes brightly and continues to burn, then the diode bridge in the high-voltage part or the filter capacitor is out of order.Burnout of the high-voltage transformer is possible.

If the fuse is intact, then the reason for inoperability may be:

failure of the transistors of the pulse generator;
malfunction of the PWM controller.

In these cases, it is easier to purchase a new device, which, depending on the capacity, costs from 600 to 800 rubles.

Video (click to play).

With repeated self-starting of the device, the reason for inoperability is usually the failure of the reference voltage stabilizer. In this case, the computer system cannot pass the self-test mode, it turns off and turns on the power module.

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