How does a switching power supply for a satellite tuner work? Repair of power supplies for satellite tuners. On our power supply, after checking this transistor, a short circuit was discovered between its contacts. It follows from this that the transistor has “burned out”

During operation satellite receivers Globo, Bigsat, Allsat, Yumatu, Lumax, Digital, Boston and others like them, one common fault was noticed in all of them:

The tuner does not start, the LED on the front panel is on, and the digital display does not light up or flickers faintly. The reason for this behavior of the tuners was a malfunction of the power supplies in the +3.3V circuits, much less often in the +5V circuits.

In more than 90% of cases, the cause was poor quality capacitors (C15) of the power supply in circuits 3.3 volts.

It is important to remember that stabilization of the voltage group of the entire power supply is carried out precisely along the +3.3V circuit, and it is in it that the optocoupler LED (PC817) is installed.

Faulty capacitors often swell, and their end surface takes on a spherical shape. A swollen capacitor can be identified visually.

At the initial stage of drying out the capacitor (C15), the voltage +3.3V is normal ( Feedback is still able to compensate for the decrease in capacitor capacity), (but other voltages will be higher than normal). The voltages in the +5V, +12V and +22V circuits (if there is a fault in the +3.3V circuit) will be increased.(The stabilization circuit strives to maintain the voltage in the +3.3V circuit normal, while simultaneously increasing the voltage in all secondary voltage circuits)

After replacing the faulty elements, all voltages return to normal both at idle and under load.

voltage to diode D8
voltage after diode D8
voltage at the inspection line

On the oscillogram “voltage after diode D8” (there should be a straight horizontal line at +3.3 V);

Replacing faulty capacitors is usually enough to restore the tuner's functionality. motherboards This type of equipment has a fairly high reliability.

Note: Once, in addition to replacing the capacitors, it was necessary to replace the rectifying diode (D8) in the +3.3 V circuit. In some tuner models, the power supply circuit has a different numbering of elements.

In a number of cases, due to overvoltage in the network, 2 diodes in the bridge on the high-voltage side and a fuse burned out. The diodes burn out in pairs. Burnt-out diodes are short-circuited, so they only carry a fuse with them; the rest of the circuit usually remains intact.

Power supply circuit on the dmo265r chip

satellite tuners Globo, Boston, BigSAT...

F1 – fuse;
C2, LP1, C3 – prevent the penetration of RF debris from the UPS into the network;
NTC-1 – thermistor, acts as a capacitor charge current limiter when the UPS is connected to the network;
C11, R3, D5 – chain limits bursts EMF primary transformer windings at the moment of closing the power transistor (protects the power transistor of the microcircuit)
U1 – microcircuit, includes a control circuit and a power transistor;
R4 – current limiter;
C12 –
DZ1 – zener diode (not provided in the circuit recommended by the manufacturer)
U2 – optocoupler;
TR2 – transformer;
D7 – rectifier diode in the circuit +22 V;
C13, L1, C16 – filter in the circuit in the +22 V circuit;
D10 – rectifier diode in the +12 V circuit;
C19, L4, C20 – filter in the +12 V circuit;
D11 – rectifier diode in the +5 V circuit;
C1, L3, C14 – filter in the +5 V circuit;
C15, L2, C17 – filter in the +3.3 V circuit;
R15, R19, R1, R18 – load resistors(ensure voltage stability while significantly reducing the load in the circuit);
U2, U3 – KA431A2 chip. In the normal state, input 2 is 2.5 V. As the voltage in the +3.3 V circuit increases, the voltage at input 2 of the KA431A2 microcircuit also increases. In this case, the output transistor opens and the LED of optocoupler U3 (PC817) lights up;
C33, R8 – the chain prevents self-excitation of the KA431A2 microcircuit.

- when the supply voltage (310 V) appears on capacitor C1 and pin 5 of the microcircuit, capacitor C8 is charged to a voltage of 12 V through the internal current limiting circuit, built-in switch, pin 2 of the microcircuit. Then the key breaks the described circuit;

GLOBO 7010A tuner power supply

F1 – fuse;
C4, C5 – capacitive voltage divider provides half of the mains voltage on the device body (implemented in almost all AV equipment to allow secure connection equipment);
C2, LF1 – prevent the penetration of RF debris from the UPS into the network;
MOV1 – varistor (210pF 470volts 10%) limits the influence of network surges on the UPS (during prolonged overvoltages, they close and burn the fuse, protecting the rest of the circuit);
D1, D2, D3, D4 – diode bridge, mains voltage rectifier;;
C1 – smoothes out the ripples of the rectified network voltage (the voltage across it is about 310 V);
C10, R3, D5 – the chain limits surges in the EMF of the primary winding of the transformer at the moment the power transistor is closed (protects the power transistor of the microcircuit)
U1 – KA5MO365R microcircuit, includes a control circuit and a power transistor;
R5, D6, C8 – power the microcircuit after startup (switching on) from the additional winding of the transformer;
C9, R6 – filter in the stabilization circuit circuit;
U2 – optocoupler;
TR1 – transformer;
D11 – rectifier diode in the +30 V circuit;
C21, R20, C22, C32 – filter in the circuit in the +30 V circuit;
D12, D13 - limit the voltage in the +30 V circuit (they can burn out when capacitors C13, C15 dry out);
D16 – rectifier diode in the -12 V circuit;
C24, R19, C27, – filter in the circuit in the -12 V circuit;
D17 - limits the voltage in the -12 V circuit (may burn out when capacitors C13, C15 dry out);
D10 – rectifier diode in the +22 V circuit;
C19, L4, C20, C30 – filter in the circuit in the +22 V circuit;
D9 – rectifier diode in the +12 V circuit;
C17, L3, C18, C29 – filter in the +12 V circuit;
D7 – rectifier diode in the +5 V circuit;
C13, L1, C14, C26 – filter in the +5 V circuit (drying of C13 causes an increase in the remaining output voltages of the power supply unit);
D8 – rectifier diode in the +3.3 V circuit;
C15, L2, C16, C31 – filter in the +3.3 V circuit (drying out C15 causes an increase in the remaining output voltages of the power supply unit);
R(D14), R12, R15, R18 – load resistors (ensure voltage stability while significantly reducing the load in the circuit);
R17, R9 – voltage divider (in normal mode it provides voltage division of 3.3 V / 2.5 V);
R10, R9 – voltage divider (in normal mode it provides voltage division 5 V / 2.5 V);
U3 – TL431 chip. In the normal state, input 2 is 2.5 V. As the voltage in the +3.3 V circuit increases, the voltage at input 2 of the TL431 microcircuit also increases. In this case, the output transistor opens and the LED of optocoupler U3 (PC817) lights up;
R7 - Limiting resistance ensures normal operation for the PC817 optocoupler LED;
C23, R8 – the chain prevents self-excitation of the TL431 microcircuit.

The microcircuit is powered as follows:

- when the supply voltage (310 V) appears on capacitor C1, capacitor C8 is charged through resistors R1, R2, supplying supply voltage to pin 3 of the microcircuit.
- the PWM generator starts and the circuit is powered through the circuit: additional winding of the transformer, R5, D6, capacitor C8.

Power supply circuit based on the STRG6351 chip

F81 – fuse;
C81, C82, L81 – prevent the penetration of RF debris from the UPS into the network;
C83, C84 – capacitive voltage divider provides half the mains voltage on the device body (110 V relative to zero and 110 V relative to phase. Implemented in almost all AV equipment to allow safe connection of equipment powered from one outlet);
RU81 – varistor limits the influence of network surges on the UPS (during prolonged overvoltages, it closes and burns the fuse, protecting the rest of the circuit);
D81, D82, D83, D84 – diode bridge, mains voltage rectifier;
MCT 100-9 – breaking resistor, acts as a charge current limiter for capacitor C85 when the UPS is connected to the network. Burns out when the STRG6351 chip is damaged;
C85 – smoothes out ripples of the rectified mains voltage (the voltage across it is about 310 V);
C86, D85, R82 – the chain limits surges in the EMF of the primary winding of the transformer at the moment the power transistor is closed (protects the power transistor of the STRG6351 microcircuit);
R81, C87 – provide supply voltage to the control circuit of the STRG6351 microcircuit at the time of startup (switching on);
IC81 - STRG6351 chip (converter) includes a control circuit and a power transistor;
R83, D86, C87 – power the control circuit of the STRG6351 microcircuit after startup (switching on) from the additional winding of the transformer;
R86, PC81, D87, C88 – part of the stabilization circuit located on the high-voltage side of the UPS. When the optocoupler LED lights up, the phototransistor opens, the voltage on capacitor C88 and pin 6 of the STRG6351 microcircuit increases, which leads to a decrease in the duration of the open state of the power transistor and a decrease in output voltages;
R85, R84, C88 – overload protection circuit. When overloaded, the current in the circuit increases: the primary winding of the transformer, the power transistor, resistance R84 > the voltage at C88 and pin 6 of the STRG63511 microcircuit increases, which leads to a decrease in the duration of the open state of the power transistor;
D26, C30 – +30 V circuit rectifier;
L26, C31 – +30 V circuit filter;
D25, C28 – +23 V circuit rectifier;
L25, C29 - +23 V circuit filter;
D23, C25 – +12 V circuit rectifier;
IC21, C26 – +12 V circuit stabilizer;
D22, C23 – +7 V circuit rectifier;
L22, C24 - +7 V circuit filter;
D21, C21 – circuit rectifier +3.3 V;
L21, C22 - circuit filter +3.3 V;
R31, R27, R22, R21 – load resistors (ensure voltage stability while significantly reducing the load in the circuit);

Part of the stabilization circuit located on the low voltage side of the UPS.

R53, R54 – voltage divider (in normal mode it provides voltage division of 3.3 V / 2.5 V);
IC51, C51 – TL431 chip. In the normal state, input 2 is 2.5 V. As the voltage in the +3.3 V circuit increases, the voltage at input 2 of the TL431 microcircuit also increases. In this case, the output transistor opens and the PC81 optocoupler LED lights up;
R51, PC81 – Limiting resistance ensures normal operation for the PC817 optocoupler LED.

Satellite television occupies an important place in the entertainment sector. And this is facilitated by the inexpensive price of equipment and an extensive list of channels. But all the joy can come down to “no” if the receiver does not turn on satellite television.

Everything would be fine, but there is one unpleasant moment. Chinese receivers often fail. The main cause of equipment failure is a broken power supply. This happens due to thunderstorms, voltage surges, and simply poor-quality components of this unit. In contrast, other receiver modules practically do not break. It’s about this common breakdown that we’ll talk and find out how to repair the receiver’s power supply with your own hands.

This article will provide simple and practical ways to determine the faulty part in the tuner power supply. Although the methods are simple, their use in most cases allows you to repair the power supply of the satellite television receiver yourself.

So, if your satellite TV receiver model: Gione, Cosmo Sat and the like has stopped working, then don’t rush to worry, maybe everything is not so bad. Try to find the reason yourself without the help of specialists.

What might you need? Multimeter, continuity tester, soldering iron and a little patience.

We remove the cover of the device and see a separate module. It's there pulse block nutrition. To start troubleshooting, remove it by unscrewing the screws and disconnecting the connector on system board. Now the payment is before us.

The first thing you need to do with the board is to visually determine whether there are damaged (swollen) capacitors and other circuit elements. Often this is the reason why the satellite TV receiver does not turn on.

If damage is not visible, then it is necessary to check the integrity of the cord and fuse. We put a continuity tester on the ends of the fuse, and by the reaction of the device we determine its integrity.

If the fuse is good, that's good. And if not, then do not rush to change it, since the same thing can happen to it as to the first one. It is better to solder a socket with an incandescent lamp in its place. The lamp has a power of 60 watts and a voltage of 220 volts.

Now, if in the circuit, when turned on, there will be short circuit, then the lamp will simply light up at full intensity, without causing any harm to the circuit. If the lamp does not light up when you turn it on, take a multimeter and measure the voltage on a large capacitor 47 uF * 400 volts.

The multimeter must be set to “DC voltage measurement” mode. On the contacts of the capacitor when normal operation, the voltage should be about 300 volts. If there is none, then we call along the chain, from the fuse to the diode bridge. In case of presence AC voltage at the input of the bridge, everything points to a breakdown of the diodes, and this is also one of the frequent breakdowns in which the satellite television receiver does not turn on. To determine which diode has failed, you need to unsolder one end of each.

Then, by placing a continuity tester on each diode alternately and swapping the ends, we determine their integrity. A working diode must pass current in one direction. If the diode rings equally in two positions, it means it is broken. Most often, a pair of diodes fail. Therefore, if possible, it is better to change all four at once, since after such breakdowns, even those that remain working change their parameters. As a result, partial replacement of diodes can be considered as an inferior repair of the receiver's power supply. This means that there is a high probability that one day you may again encounter a situation where you will need to eliminate this malfunction, as a result of which the satellite television receiver has stopped working.

The diodes have been replaced, now we turn it on again and measure the DC voltage on the same capacitor. It should be, as mentioned above, about 300 volts. If this is the case, then the next diagnostic step is to measure the alternating voltage on one of the primary windings of the transformer. How to do this can be seen in the photo below.

The device should show about 150 volts, and the voltage should seem to “float”, that is, change. If this does not happen, then most likely the microcircuit has failed. You can replace the microcircuit and repeat the measurements again.

When the device shows the presence of a pulsating alternating voltage on the primary winding, it is necessary to immediately measure the direct voltage at the output of the unit.

To do this, put the multimeter in the “DC voltage measurement” mode and attach the negative (black) probe to the second slot on the connector. This is the common (negative) contact. Using the other end of the device, we measure the voltages at the slots of the connector one by one.

If you turn the plug with the slots towards you and measure from left to right, then the voltages should be as follows:

general
general
3.3V

If there is no voltage, then we do the same operation with the diodes of the secondary circuit, as described above. Having identified a faulty one, we replace it. Note the larger diode. It is labeled SR-360 and the like. It fails most often. By replacing it, you can solve the problem when the satellite television receiver does not turn on. Again we measure the voltage at the terminals.

If this method does not yield anything, then most likely the microcircuit in the primary circuit, which acts as an alternating voltage generator, has “failure” high frequency. But, as practice shows, this rarely happens.

That's all I wanted to tell you about repairing the power supply of the satellite television receiver. Successful repair.

Hello, today we will try to fix the Tricolor TV receiver with our own hands. Many people have encountered this problem when the warranty (usually 12 months) has expired and the receiver suddenly breaks down. A new one is expensive, and in most cases, repairs will not be difficult and will cost pennies, if you are even a little familiar with a soldering iron, the main and most common faults are easy to fix yourself. Let's consider such a repair using the example of another receiver from the Tricolor TV company GS-8300 N. I must say, the device is not the most best quality, and the money that Tricolor TV takes for it, of course, is not worth it. But, nevertheless, the number of subscribers is large and not everyone has everything working for a long time and properly.

Power supply fault:

The main and most common malfunction of all receivers is a malfunction in the power supply circuit and voltage conversion. Also, the modulator often fails due to a short circuit in the coaxial cable from the LNB, although latest models They have good protection against short circuits in the cable, when triggered, the voltage supply to the converter simply stops until the short circuit is eliminated.

And so, our receiver does not show any signs of life, the indicators on the front panel display do not light up, and no amount of pulling the power plug from the socket and turning the toggle switch on and off helps us (at least this was the case with the device, an example of which is given in this article) . The first thing we do is unplug the plug from the network and remove top cover, we need to get to the electronic filling of the device. And here it is important to remember one thing, namely the warranty seal, which we will certainly break if we remove the cover. Therefore, make sure once again that the warranty period has definitely expired, and no one will repair it for you under warranty. If the warranty is still valid, I advise you to take the receiver to a service center and entrust this matter to a specialist.

Opening the lid we see printed circuit boards with many components interconnected by wire buses. Below are photos describing some of the devices on the board. First of all, we are interested in the power board; it is not difficult to distinguish it by the transformer installed on it and the power supply cable. And the first thing we pay attention to is the fuse. It is usually installed at the beginning of the chain. The fuse will not necessarily have the shape you are familiar with (a glass capsule with a thin conductor inside), for example, in my case the fuse is enclosed in a small plastic box, and in order to get directly to the fuse itself, the cover of this box must be removed. This is done very simply, for example with tweezers. Having reached the fuse, we check it with a tester or multimeter for a break. If the fuse burns out, which by the way happens very often, we go to a radio store, buy the same one, change it and that’s it. If this is not the case, we check the parts further along the chain. Often the transformer itself fails; we can detect such a malfunction by measuring the voltage on the secondary winding. I must say that not everyone can replace the transformer, if so, then it is better to take the receiver to a workshop, but if you are confident in your abilities, then go ahead, for example, it will not be difficult for me.

Receiver inside:

Electorolytic or oxide capacitor, standing at the entrance, often dries out and breaks down, which is also a malfunction; not everyone can find such a breakdown either, you need to have at least First level radio amateur. Typically, faulty capacitors will have a yellowish appearance, or a small brown spot on the board at the base of the legs. Also, the health of a capacitor can be determined by comparing its nominal and measured capacity.

The receiver uses direct current, which is rectified from the AC network using a diode bridge. Problems with the diode bridge also happen. Diodes are very easy to check; the main function of a semiconductor diode is to pass current in one direction and not in the other. In my case, the transistor of the primary winding of the transformer turned out to be faulty; it is not difficult to find; it usually has a radiator for heat removal. I determined the malfunction of the transistor by measuring the voltage at its emitter, it was absent there, the primary winding was not powered, and therefore everything else was de-energized. The transistor cost me 28.5 rubles. Replacing it with a soldering iron, I fixed the fault and the receiver is in working order again. I must say that such a breakdown is quite a rare occurrence; usually everything ends on the fuse.

A very common problem is a firmware crash. The firmware often crashes, this is usually evidenced by complete freeze receiver In this case, “reflashing” will help. I would also like to say about another cause of malfunction, which may arise due to poor-quality installation. Water in the cable. If the external insulation of the cable is broken, then water from precipitation can get inside and easily enter the receiver like a hose, sometimes flooding all its insides. The condition of the cable must be monitored throughout the entire service life of the device.

Electronic devices surround us everywhere: on the street, at work, at home. With the rapid growth and accessibility of satellite television to the masses, there is now a wide range of satellite equipment available to the public. These are satellite receivers, conditional access modules, antennas, converters, etc. Whether we like it or not, sooner or later breakdowns happen to them, which make us feel like we have lost our favorite thing.

There is no need to despair - for this purpose there are service centers that you can contact and they will help you bring your equipment back to life.

Equipment breakdowns occur for various reasons - voltage surges, failure of various components, wear and tear of the equipment itself from its venerable age, you can also note the incompetence of the owners themselves, for example, incorrect replacement software in satellite and cable receivers.

A power supply failure is perhaps the most common type of malfunction of digital terminals. It occurs for various reasons: poor-quality power supply (see photo), low-quality radio components are used, especially this is de facto in Chinese technology.

This also includes improper operation, dust, dirt, and as a result, incorrect thermal conditions (see photo).

Service center is structural subdivision within the company. He is responsible not only for the repair and maintenance of products sold by our company, but also for the repair (including warranty) of satellite equipment from other companies. Our clients are not only individual users, but also equipment dealers who strive to relieve their customers from the problems associated with the repair and maintenance of receivers. A flexible policy towards corporate customers allows us to provide adequate service and satisfy the interests of all customer groups. This is more than 1000 units of equipment per month. It is, of course, possible to carry out such large volumes due to the professionalism of the employees and the equipment service center professional equipment, tools and technical documentation. Therefore, our service center carries out highly complex repairs: for example, replacing processors in BGA cases. Repairs take place in the shortest possible time.

The supply department, in addition to its main function - purchasing equipment, also deals with the needs of the service center, purchasing components necessary for repairs. And here it is worth noting that the selection and purchase of components for repairs occurs according to the following criterion: the quality of the parts comes first, their price comes second, but due to the large volumes of supplies of parts, the price ultimately remains low.
All orders are processed in in electronic format and is registered in the database. This makes it easy to track the various stages of the repair process. A guarantee is provided for the work performed.

Of course, unforeseen moments happen - for some reason the repair is delayed. This usually happens due to the absence of some scarce radio component. Sometimes repairs require a complete replacement of the motherboard, and this repair part is not always available. In this case we are trying to find some acceptable solution together with the client, taking into account his wishes, combined with our capabilities.

The receiver died after a power surge.

Upon opening, the following were found to be out of order:
- network capacity C5 - 47µFx400V
- Q1 - CS2N60F
- R8, R11, R13 - each with a nominal value of 3 Ohm (size 1206)
- R9 - 47 Ohm (1206)
- U1 - it was not possible to determine its type based on the markings on the case.

According to the table for identification and selection of analogues, the last part was replaced with SG6848 with minimal intervention in the factory circuit.
Dismantling: (circled in red in the photo)
- U1
- R8, R11, R13 - 3 Ohm (1206)
- R3, R6 (one of them is possible) - 1 MOm (1206)
- C3 - 68nF
- R25 - 3.6 kOm (0805)
- R26 - 10 kOm (0805)
Install:
- instead of U1 - SG6848
- instead of R8, R11, R13 - one resistor 1.8 Om x 0.5W (regular output, because I didn’t have the required smd value))
- instead of C3 there is a 100 kOm resistor (1206)
- instead of R26 there is a 33 kOm resistor
- instead of R25, we select a resistor in the range of 10-12 kOm, controlling the 3V3 voltage at the VD8 cathode. I settled on a nominal value of 11 kOm, U=3.36V (at 10 kOm U=3.28V, at 12 kOm U=3.41V)

Instead of the burned out Q1, an SSS4N60B (TO-220F body) was installed

GS-8300 power supply diagram

Telesputnik posted a power supply diagram.

There are inaccuracies:
1. The bottom terminal of the primary winding must be connected
to the connection point between anode D6 and drain Q1
2. The position designation of C2 and C3 is incorrect. C3 should be connected to the 3rd pin
U1, C2 to 4th pin of U1.
3. Rating C3=68nF
4. There are two capacitors C1 in the diagram
5. No C12
6. Primary land is designated in the same way as secondary.
7. Missing C8
8. Q2 - MOSFET NTD14N03R
9. Rating C11=2200pF
10. Type D8=SR560
11. The position designation of U3 and U4 is incorrect - they need to be swapped.
12. Rating C5=47µF

If the AV output does not work

Question:

The receiver turns on, there is 18 volts on the LNB. There is no video signal, it gets very hot (can’t hold your finger) stv 6419..could there be no video because of it? Is there no other point? (I mean, there’s nowhere else to get a video signal from?) The receiver switches channels..

Receiver GS 8300N there is no video and audio signal through scart to the TV, channels are switched on the receiver panel.

Solution:

the video signal from the STi5119ALC processor arrives, you can check it with an oscilloscope at the test point opposite the capacitor C117, then it comes to the resistor R87 and is transmitted to the capacitor C129 and then goes to the STV6419 chip; on the 3rd leg of STV6419, the 12 volt zener diode D3 near the power connector is faulty

There was this answer: if you use only a composite video signal, most likely you can simply throw it away (replace it with a jumper). Where should I put the jumper? if this is the right advice...

VD3 (VD3 12 V zener diode) on the motherboard next to the power connector is faulty.

Zener diode brand and parameters:

Power supply +12V to the 3rd leg STV6419...
Along the chain: connector XP5 9th leg ---> R81 (300 Om) + zener diode VD3 (12V) = stabilizer +12V ---> L3 ---> 3rd leg STV6419.

Zener diode analogue:

I couldn’t find a similar VD3 STV6419 zener diode (SMD). Put 0.5 watt glass zener diode the size of a diode kd522 . So far the flight is normal.

If replacing the zener diode does not help:

After the thunderstorm, 6419 swelled. After the replacement, the image did not appear, but when checking the wiring, two resistors turned out to be broken, R91, R95. Replaced it and everything worked.

One more problem:

And yet, instead of 13, 18 Volts, the LNB received 24V. Needed replacement DA1 (LM317T). And that's it, the flight is normal

The same situation for the GS-8304 receiver:

After 5 years of operation, the GS-8304 suddenly stopped broadcasting, although the display was working properly.
The zener diode has broken through to short circuit... Zener diode brand MMZE5242B...

During operation satellite receivers Globo, Bigsat, Allsat, Yumatu, Lumax, Digital, Boston and others like them, one common fault was noticed in all of them:

In more than 90% of cases, the cause was poor quality capacitors (C15) of the power supply in circuits 3.3 volts.

Faulty capacitors often swell, and their end surface takes on a spherical shape. A swollen capacitor can be identified visually.

At the initial stage of drying out the capacitor (C15), the voltage of +3.3V is normal (the feedback is still able to compensate for the decrease in capacitor capacity), (but other voltages will be higher than normal). The voltages in the +5V, +12V and +22V circuits (if there is a fault in the +3.3V circuit) will be increased.(The stabilization circuit strives to maintain the voltage in the +3.3V circuit normal, while simultaneously increasing the voltage in all secondary voltage circuits)

After replacing the faulty elements, all voltages return to normal both at idle and under load.

voltage to diode D8
voltage after diode D8
voltage at the inspection line

On the oscillogram “voltage after diode D8” (there should be a straight horizontal line at +3.3 V);

Replacing faulty capacitors is usually enough to restore the tuner's functionality. Motherboards of this type of equipment have fairly high reliability.

Power supply circuit on the dmo265r chip

satellite tuners Globo, Boston, BigSAT...

F1 – fuse;
C2, LP1, C3 – prevent the penetration of RF debris from the UPS into the network;
NTC-1 – thermistor, acts as a capacitor charge current limiter when the UPS is connected to the network;
C11, R3, D5 – the chain limits surges in the EMF of the primary winding of the transformer at the moment the power transistor is closed (protects the power transistor of the microcircuit)
U1 – microcircuit, includes a control circuit and a power transistor;
R4 – current limiter;
C12 –
DZ1 – zener diode (not provided in the circuit recommended by the manufacturer)
U2 – optocoupler;
TR2 – transformer;
D7 – rectifier diode in the +22 V circuit;
C13, L1, C16 – filter in the circuit in the +22 V circuit;
D10 – rectifier diode in the +12 V circuit;
C19, L4, C20 – filter in the +12 V circuit;
D11 – rectifier diode in the +5 V circuit;
C1, L3, C14 – filter in the +5 V circuit;
C15, L2, C17 – filter in the +3.3 V circuit;
R15, R19, R1, R18 – load resistors (ensure voltage stability while significantly reducing the load in the circuit);
U2, U3 – KA431A2 chip. In the normal state, input 2 is 2.5 V. As the voltage in the +3.3 V circuit increases, the voltage at input 2 of the KA431A2 microcircuit also increases. In this case, the output transistor opens and the LED of optocoupler U3 (PC817) lights up;
C33, R8 – the chain prevents self-excitation of the KA431A2 microcircuit.

- when the supply voltage (310 V) appears on capacitor C1 and pin 5 of the microcircuit, capacitor C8 is charged to a voltage of 12 V through the internal current limiting circuit, built-in switch, pin 2 of the microcircuit. Then the key breaks the described circuit;

GLOBO 7010A tuner power supply

F1 – fuse;
C4, C5 – capacitive voltage divider provides half the mains voltage on the device body (implemented in almost all AV equipment to allow safe connection of equipment);
C2, LF1 – prevent the penetration of RF debris from the UPS into the network;
MOV1 – varistor (210pF 470volts 10%) limits the influence of network surges on the UPS (during prolonged overvoltages, they close and burn the fuse, protecting the rest of the circuit);
D1, D2, D3, D4 – diode bridge, mains voltage rectifier;;
C1 – smoothes out the ripples of the rectified network voltage (the voltage across it is about 310 V);
C10, R3, D5 – the chain limits surges in the EMF of the primary winding of the transformer at the moment the power transistor is closed (protects the power transistor of the microcircuit)
U1 – KA5MO365R microcircuit, includes a control circuit and a power transistor;
R5, D6, C8 – power the microcircuit after startup (switching on) from the additional winding of the transformer;
C9, R6 – filter in the stabilization circuit circuit;
U2 – optocoupler;
TR1 – transformer;
D11 – rectifier diode in the +30 V circuit;
C21, R20, C22, C32 – filter in the circuit in the +30 V circuit;
D12, D13 - limit the voltage in the +30 V circuit (they can burn out when capacitors C13, C15 dry out);
D16 – rectifier diode in the -12 V circuit;
C24, R19, C27, – filter in the circuit in the -12 V circuit;
D17 - limits the voltage in the -12 V circuit (may burn out when capacitors C13, C15 dry out);
D10 – rectifier diode in the +22 V circuit;
C19, L4, C20, C30 – filter in the circuit in the +22 V circuit;
D9 – rectifier diode in the +12 V circuit;
C17, L3, C18, C29 – filter in the +12 V circuit;
D7 – rectifier diode in the +5 V circuit;
C13, L1, C14, C26 – filter in the +5 V circuit (drying of C13 causes an increase in the remaining output voltages of the power supply unit);
D8 – rectifier diode in the +3.3 V circuit;
C15, L2, C16, C31 – filter in the +3.3 V circuit (drying out C15 causes an increase in the remaining output voltages of the power supply unit);
R(D14), R12, R15, R18 – load resistors (ensure voltage stability while significantly reducing the load in the circuit);
R17, R9 – voltage divider (in normal mode it provides voltage division of 3.3 V / 2.5 V);
R10, R9 – voltage divider (in normal mode it provides voltage division 5 V / 2.5 V);
U3 – TL431 chip. In the normal state, input 2 is 2.5 V. As the voltage in the +3.3 V circuit increases, the voltage at input 2 of the TL431 microcircuit also increases. In this case, the output transistor opens and the LED of optocoupler U3 (PC817) lights up;
R7 - Limiting resistance ensures normal operation for the PC817 optocoupler LED;
C23, R8 – the chain prevents self-excitation of the TL431 microcircuit.

The microcircuit is powered as follows:

- when the supply voltage (310 V) appears on capacitor C1, capacitor C8 is charged through resistors R1, R2, supplying supply voltage to pin 3 of the microcircuit.
- the PWM generator starts and the circuit is powered through the circuit: additional winding of the transformer, R5, D6, capacitor C8.

Power supply circuit based on the STRG6351 chip

F81 – fuse;
C81, C82, L81 – prevent the penetration of RF debris from the UPS into the network;
C83, C84 – capacitive voltage divider provides half the mains voltage on the device body (110 V relative to zero and 110 V relative to phase. Implemented in almost all AV equipment to allow safe connection of equipment powered from one outlet);
RU81 – varistor limits the influence of network surges on the UPS (during prolonged overvoltages, it closes and burns the fuse, protecting the rest of the circuit);
D81, D82, D83, D84 – diode bridge, mains voltage rectifier;
MCT 100-9 – breaking resistor, acts as a charge current limiter for capacitor C85 when the UPS is connected to the network. Burns out when the STRG6351 chip is damaged;
C85 – smoothes out ripples of the rectified mains voltage (the voltage across it is about 310 V);
C86, D85, R82 – the chain limits surges in the EMF of the primary winding of the transformer at the moment the power transistor is closed (protects the power transistor of the STRG6351 microcircuit);
R81, C87 – provide supply voltage to the control circuit of the STRG6351 microcircuit at the time of startup (switching on);
IC81 - STRG6351 chip (converter) includes a control circuit and a power transistor;
R83, D86, C87 – power the control circuit of the STRG6351 microcircuit after startup (switching on) from the additional winding of the transformer;
R86, PC81, D87, C88 – part of the stabilization circuit located on the high-voltage side of the UPS. When the optocoupler LED lights up, the phototransistor opens, the voltage on capacitor C88 and pin 6 of the STRG6351 microcircuit increases, which leads to a decrease in the duration of the open state of the power transistor and a decrease in output voltages;
R85, R84, C88 – overload protection circuit. When overloaded, the current in the circuit increases: the primary winding of the transformer, the power transistor, resistance R84 > the voltage at C88 and pin 6 of the STRG63511 microcircuit increases, which leads to a decrease in the duration of the open state of the power transistor;
D26, C30 – +30 V circuit rectifier;
L26, C31 – +30 V circuit filter;
D25, C28 – +23 V circuit rectifier;
L25, C29 - +23 V circuit filter;
D23, C25 – +12 V circuit rectifier;
IC21, C26 – +12 V circuit stabilizer;
D22, C23 – +7 V circuit rectifier;
L22, C24 - +7 V circuit filter;
D21, C21 – circuit rectifier +3.3 V;
L21, C22 - circuit filter +3.3 V;
R31, R27, R22, R21 – load resistors (ensure voltage stability while significantly reducing the load in the circuit);

Part of the stabilization circuit located on the low voltage side of the UPS.

R53, R54 – voltage divider (in normal mode it provides voltage division of 3.3 V / 2.5 V);
IC51, C51 – TL431 chip. In the normal state, input 2 is 2.5 V. As the voltage in the +3.3 V circuit increases, the voltage at input 2 of the TL431 microcircuit also increases. In this case, the output transistor opens and the PC81 optocoupler LED lights up;
R51, PC81 – Limiting resistance ensures normal operation for the PC817 optocoupler LED.

A good thing is an external computer TV tuner. In my small room there was no place for a TV and a computer monitor - and now they are not needed. After all, with the help of such the most useful device As a TV tuner, you can turn absolutely any monitor into a TV. Either an old CRT or a modern LED.

Moreover, I recommend buying an external tuner, which does not require turning on the tuner itself. system unit computer (for example Grand ua40ext.). such a TV tuner works autonomously and is a kind of signal switch - when it is inactive, the image from the video card is sent to the monitor, and when we turn on the tuner with the remote control, the signal from the computer is automatically turned off and the TV signal is sent to the monitor. Or you can listen to FM, or input a video signal from a miniature video peephole on the front door, or place this video camera in the nursery, and monitor the situation in another room (kitchen).

But recently a problem arose: after turning on the TV tuner, it worked for a couple of minutes and then turned itself off. Turning it on again led to a similar result.

In general, we begin the autopsy. Naturally, the first and of course the correct thought is nutrition problems. I will say without exaggeration that faults with power supplies or supply voltage are the cause of radio equipment breakdowns in half of the cases.

To power the tuner, use a small pulse external adapter for 5 volts and half ampere. We measure the voltage at the input of the power plug - only 3.8V!

Of course, not a single digital TV processor chip will tolerate this. This is where the device turns off.

But what’s interesting is that at idle the adapter shows the required 5 volts. You'll have to open up the power supply as well.

The Chinese were too lazy to provide screws to the power supply housing, so we’ll do something radical - we’ll use a cutting tool.

Inside is a small scarf, in the style charger for mobile. Represents electronic transformer with output voltage stabilization.

We are conducting an inspection. The electrolyte at the power output looks very suspicious. It even seemed to be swollen and depressurized.

Having found a similar 470 µF capacitor, we replace it. You first need to measure it with an ESR meter, but my device is not finished yet, so I’m skipping this point :)

The test showed that now the voltage of 5 volts does not drop even under load. We connect the power supply to the TV tuner and see that the output voltage is almost normal.

Now you can close the TV tuner housing and connect it to the monitor. We check - everything works fine. Two months have passed since then, and no such defect has occurred again.

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