The most common malfunction of digital television set-top boxes is the failure of the power supply. In such an unpleasant case, it is very good if the set-top box model was with an external adapter, buy a new one and look further! And if not! And the power supply was built into the console itself? Then you have to repair or buy a new one. But perhaps there is an easy way out!

Hello dear readers! In this article, I want to share one simple repair that anyone who knows how to hold a screwdriver and a soldering iron can do! Moreover, it is not necessary to master these tools masterfully.

I'm also not going to tell you anything overly complicated from the field of electronics repair, this is the lot of professionals. On the contrary, I will try to describe everything in such a way that even a non-specialist could cope and eliminate this malfunction.

I’ll make a reservation right away that this method is not suitable for all models of set-top boxes, but for many, since they are often made according to a very similar scheme for this case. Everything will be on a specific example of a set-top box from D-Color, namely the DC1401HD model. So by understanding this "high technology" you can repair your digital TV set-top box yourself.

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Do-it-yourself console repair

What is a sign that it is the power supply that has failed in the set-top box, and not something else? If the set-top box connected to the outlet does not show any signs of life, neither the digital indicator nor the LED on the front panel is lit, then with a probability of 99% the reason is in it, in the power supply.

If at the same time the warranty period has already expired, then you can safely do the disassembly. As experienced masters say, “An autopsy will show” I think you will deal with this part of the work without detailed description, just be careful, usually two screws on the back wall, sometimes also on the sides, allow you to release and open the top cover. Plastic latches on the sides and bottom hold the front panel, and the board itself is also fixed with screws to the bottom of the case and in the area of ​​​​the connectors on the rear wall of the case.

So, the set-top box is disassembled, the power cord is also removed from the connector, it will no longer be needed. On the bottom of the case, traces of the “fire” are visible, which was left behind by the burnt power supply.

P.S. The power supply here is not a separate unit, as you might think from the name, but a section of the board on which radio elements are located that provide the necessary supply voltage to the set-top box.

What is the transformation

I will outline big picture, and for those who are already a little versed in radio engineering, this will already be enough to catch the basis of the idea and repeat. So, the power circuits of this set-top box give out only one voltage - 5 volts. Since this circuit burned out and repair may not be feasible (in terms of the cost of radio components and repairs), that is, a simple solution. Replace the internal power supply with an external one. It's not very difficult!


In the photo above, the section of the PSU that has failed is highlighted with a yellow frame. The board has already been washed, so no traces of burning are visible. By the way - Among repairmen, the expression "Burned out" does not always mean literal burning with charring and other similar manifestations, it only means that the radio components are out of order.

For our repair, you will need to purchase an external power supply with an output voltage of 5 volts and capable of delivering a current of 1.5 or better 2 amperes. Now you can buy a lot of these and not expensive, or maybe you have a similar one, for example, an unused charger from a tablet or smartphone.

When a suitable adapter is available, it remains to find the desired point on the set-top box board and, observing the polarity, apply voltage to it from an external power supply. All! It remains to lay and secure the wire, or you can organize a detachable connection, as you like. I think the basics are clear, let's get down to the details.

A little acquaintance with the power supply circuit of the set-top box

Just a little background for those who are not in the subject, so that you can figure it out. Pay attention to the photo. Click to enlarge.



In short, the power supply consists of:

  • Primary "Hot" part - Hot it is called because it is dangerous, connected with the mains voltage of 220 volts. Please note that even after unplugging from the outlet, for some time, there is a charge that can bring brr.. 😯 unpleasant sensations if you climb there. But in our case, you don’t need to climb there and we won’t connect it to the outlet either.
  • Secondary part - It is safe there, there is a galvanic isolation from the mains. In the above example, at the points indicated in the photo, a voltage of only 5 volts comes out of the rectifier diode.

Let's get down to business

In the purchased, external power supply (at least 1.5 amperes, 5 Volts.), we bite off the plug, strip the ends of the wires and, having determined the polarity, solder them: Positive to the diode output, on the side where the strip is drawn on it, and negative to the common bus - the case of the USB port will be a convenient place for this. If you don’t know how to determine the polarity, even without a device, see the end of the article Additional materials.


We connect a new power supply to the network, remove it from standby mode, check what happened.


All OK! It remains to lay and secure the wire so as not to accidentally pull it out, put everything together and use it. In the end it will look like this.


If you need ideas on how to fix the wire to the body of the set-top box? How to determine the polarity without a device? Or how to solder a wire to the underside of the board? — Then these additional materials are further down the text.

Click on the photo! Repair dvb t2 Rexant 511

Repairing a dvb t2 set-top box is a process that takes time, tools, and knowledge. Today we will try to repair the set-top box for free digital TV. We will show how the repair process goes. It is possible that this review will help someone fix their receiver.

Repair Rexant 511

The defect lies in the fact that our prefix visually works. But after the boot message appears, our receiver does not want to show the menu and the TV picture.

Rexant 511 broke down, we are repairing it.

A splash screen appears on the TV screen and then the receiver freezes. This process goes through both the HDMI cable and the tulips. In order to find a malfunction, we disassemble our receiver. We will not talk about safety precautions, all the default standards must be observed.

Repair dvb t2 Rexant 511 using an oscilloscope.

For diagnostics, we need an oscilloscope. We turn on the devices, set the necessary modes. We take the probe from the oscilloscope and begin to check the indicators on the main board.

Repair dvb t2 receiver yourself

As a result of the diagnostics, we identify the alleged malfunction. There is a capacitor on the board, by all visual signs it is normal. After taking measurements, the capacitor shows deviations from specifications declared by the manufacturer. Accordingly, it does not perform its functions.

Repair dvb t2, capacitor check.

We solder our problem capacitor. To control, we will check the capacitor, we do it in a special device, we measure the ESR of electrolytic capacitors. We see that our diagnostics were correct, the capacity has deviations.

Repair dvb t2 set-top boxes

We take a good capacitor. We check on the device whether it can be put on the board. Solder it into our main board. It must be borne in mind that one must act carefully and observe safety rules.

dvb t2 prefix after repair.

After the capacitor has been replaced, you can turn on the console and check. We need to do this in order to check if we need to look for something else or not. In this case, you don't need to solder anything else. Our plugin works!

If you still have questions, you can watch the video.

The fleet of analog TVs is rather reluctant to give way to digital equipment, gradually taking “second” places - in the kitchen, in offices, workshops, garages, etc. At the same time, DVB-T2 set-top boxes and decoders are being transferred. We have already managed to evaluate the advantages of the latter, while some owners also appreciated the disadvantages - the rather low reliability of these devices. Usually one of the most weaknesses this kind of equipment is a switching power supply - most cases of failures are associated precisely with a malfunction of the power supply, and a malfunction of the power supply unit can lead to such serious consequences that it will be impossible to repair the device. And yet, using the example of two set-top boxes for receiving digital TV, the possibility of repairing them independently will be considered here. The first device is TVK 3101. When turned on, the image had strong distortions, periodically completely disappeared. A few days later, the set-top box began to turn off a few seconds after the manufacturer's logo appeared on the screen.

The second device is the Oriel 740 prefix. This device did not respond to commands from the remote control, the indicator barely noticeably glowed red.

After opening the cases of the set-top boxes, it turned out that in both cases the electrolytic capacitors of the secondary power filters were swollen.

It should be borne in mind that when working with the attachment, special care should be taken - the primary power supply rectifier of the power supply unit converts an alternating voltage of 220 volts into a constant value of about 300 volts, and this potential remains at the terminals of high-voltage electrolytic capacitors for some time after power is removed - up to several tens of seconds . In the pictures, they are located between the pulse transformers and the plugs of the power cords. Before working with the device board, these capacitors must be short-circuited through a resistor with a resistance of 51-62 kOhm.

Both faulty capacitors turned out to be almost the same - 1000 uF, 10 V. The picture shows one of them. The fact that its cover is barely deformed in appearance should not give you the slightest confidence that the part is in good condition - even if some part of the container has been preserved, such a part will have an increased leakage current, which is unacceptable. When replacing, you should select capacitors with the same operating voltage or with a slightly higher one, as in the picture - instead of a 10-volt part, a 16-volt part is shown, and with the same dimensions. Of course, defective parts should be replaced with new ones, not used ones - otherwise the repair will have to be repeated soon.

After the replacement, turn on the set-top box - the indicator lights up brightly, the device responds to the commands of the remote control, the image is stable. But the repair is not over yet...

Traces of flux remained on the board - solder paste, rosin ... High-frequency currents can quite easily pass through such a coating wherever they please. As a result, we can get an unstable image, noise, etc. over time. trouble. Therefore, carefully wash the board with a cotton swab moistened with alcohol or acetone. After such cleaning, wipe the board with a dry cotton swab


We install the board in place, check - it works.

Now we assemble the prefix completely and once again check the performance.

Similarly, we check the second device - the device is working normally, the repair is completed.

In conclusion, I will add that the quality of the power supply of the antenna amplifier also greatly affects the operation of the set-top box. So, with insufficient capacity of the filtering capacitor, signal loss is possible - there have been cases of complete loss of the channels of the second multiplex. To recognize a malfunction of the antenna PSU, it is enough to replace it with a source direct current voltage of 9-12 volts (for example, a Krona-type battery or a battery from a computer uninterruptible power supply). If the reception quality improves, then you should replace the antenna power supply with a known good one.


In the article, the author shares his experience of repairing a tuner for receiving terrestrial digital television programs. The troubleshooting technique he described is also applicable to other electronic products where one or more functional units are powered by a voltage stabilizer with unknown output parameters.

Tuner "Globo GL50" is designed to receive DVB-T/T2 terrestrial digital television programs, as well as to play multimedia files from external media connected to the USB port of this set-top box. After working for about a year, this tuner broke down. The failure looked like a complete inoperability of the device, while the LED on the front panel glowed yellow. Repair of such devices is usually impractical, but since there are few interesting parts in modern digital devices for further use, it was decided not to disassemble the receiver into parts, but to try to repair it.

The troubleshooting was started by checking the operability of an external power supply with a stabilized output voltage of about 5.2 V at a load current of up to 1.5 A, which turned out to be serviceable. Next, on the board of the block (its marking is M3103-0C), integrated voltage stabilizers were checked. At the output of one of them (KV3VC - according to the scheme of the U4 microcircuit), there was a voltage of 0.537 V, while the microcircuit case heated up to a temperature above 100 ° C in five minutes. This stabilizer directly feeds the tuner's CPU, which remains cool. The initial version that one of the ceramic blocking capacitors C23, C24, C35 was broken was not confirmed.

Turning off the load of the stabilizer did not change the situation: the microcircuit case also got very hot. Because no useful information neither the failed microcircuit, nor the board itself could be found, it was necessary to find out what voltage is required for the operation of the central processor experimentally. To do this, the U4 chip was soldered from the board, and the output of a powerful laboratory regulated power supply was connected to the printed conductor intended for soldering its output pin (the closest contact next to the inscription "U4"). At a voltage of 1.1 V or less, the tuner processor worked with errors or hung. At a voltage of 1.2 V, the processor worked without errors in all modes of operation of the set-top box, consuming a current of about 0.6 A.

Since even if it were possible to find and purchase the same microcircuit to replace the failed one, its installation, according to the author, is devoid of practical sense (what burned out once will burn out the second and third time); It is not enough to simply fix the problem, you need to eliminate the causes of its occurrence. It is likely that the KV3VC integral stabilizer burned out from overheating - a typical malfunction of modern digital devices, ranks first in the number of failures of household and industrial devices (printed wiring is in second place, and together they "take" more than 90% of all malfunctions that did not occur due to misuse).

It was decided to replace the faulty switching stabilizer microcircuit with a linear stabilizer with an output voltage of 1.3 V on the KR142EN12A microcircuit, the circuit of which is shown in Fig. 1 (positional designations of its parts begin with the prefix 1). The output voltage is set by resistors 1R1, 1R2. The lower the resistance of the first of them (with the second unchanged), the lower the output voltage. Capacitors 1C1, 1C2 - blocking. Diodes 1VD1 - 1VD3 protect the load from damage in case of 1DA1 malfunctions. Taking into account the voltage drop on the connecting wire, the output voltage of the stabilizer turned out to be approximately 1.28 V.

Rice. 1. Stabilizer circuit

The details of the new voltage regulator are placed on a 22x22mm circuit board. The KR142EN12A chip is installed on a ribbed duralumin heat sink, which is tightly pressed against the bottom and side walls of the metal case of the attachment. Since the heat sink flange of the microcircuit is electrically connected to pin 2, it is fixed to the heat sink through an insulating gasket, a PVC tube and a getinax washer are put on the fixing screw for insulation. All mating planes are lubricated with heat-conducting paste. Instead of KR142EN12A, you can install KR142EN12B or one of the imported ***317 series in the TO-220 package (for example, LM317, KA317). The purpose of the conclusions of all these microcircuits is the same. A view of the installation of the stabilizer and the "stuffing" of the attachment is shown in fig. 2.

Rice. 2. View of the installation of the stabilizer and the "stuffing" of the attachment

The input of the stabilizer is connected to the fusible insert F1 (Fig. 3, red wire), the output is connected to the inductor L4 (Fig. 4, green wire), and the common wire is connected to the negative plate of the capacitor C35 (Fig. 4). Instead of diodes 1N4001, you can use any of KD208, KD243, KD247, 1 N4002-1 N4007.

Rice. 3. Circuit board

Rice. 4. Circuit board

M3103-0C circuit board can be used in other DVB-T2 receiver models. Since the author has never come across "cold" DVB-T2 set-top boxes (all of them get very hot during operation), after the end of the warranty period, it is advisable to measure and record the input and output voltage values ​​​​of the stabilizers installed on the board, and also photograph the circuit board from both sides so that all the inscriptions are visible, this can be useful when repairing a failed device. Keep in mind that several operating voltages can be simultaneously formed at the output of a pulsed integral stabilizer. To improve cooling inside the console, you can install a small "laptop" fan.

After the repair, the current consumed by the tuner from the power source was about 0.75 A, which means that the external bundled switching power supply with the output parameters indicated at the beginning of the article is able to provide power not only to the DVB-T2 set-top box, but also to the external connected to it. 2.5" form factor hard drive. If the set-top box is equipped with a power supply built into its case, in order to reduce the load on it and, accordingly, to reduce the temperature inside the case, it is advisable to power 2.5 "" hard drives from an external unit.


Publication date: 20.01.2016

Readers' opinions
  • genn / 12.11.2017 - 07:30
    Well said - thanks
  • admin / 31.10.2017 - 10:17
    Unfortunately, there are no diagrams.
  • ALEXANDER / 30.10.2017 - 19:00
    Globo GL50 diagram where to find
  • Victor / 19.03.2017 - 11:47
    Thank you! Interesting. Informative.
  • Vladimir Vasilievich / 29.12.2016 - 13:59
    I'm 69. I'm still interested. I liked both the site and the sections. since 1967. Thank you 73.
  • Guest / 07.02.2016 - 20:23
    The article will be useful to a certain circle of people, I liked it.

06.01.2017

Denis Bolshekov

If you wondered: Why does the digital set-top box not show or show poorly? You are at the address.

Let's look into this situation.

Doesn't show digital DVB-T2 TV and what to do about it?

First you need to make sure that you are in the zone of reliable DTV reception. If the prefix used to show and then abruptly stopped, possible reason in the wrong connection of the antenna equipment. Or the DVB-T2 receiver is outdated, this is solved by downloading a new firmware from the manufacturer's website.

We will assume that the prefix is ​​in full working order. In this article, we will configure only the prefix itself and the antenna.

Problem: not all channels were scanned and caught

You have done an auto search and your set-top box has not found all the channels - you need to manually search for channels. Most likely, the set-top box did not receive the second multiplex signal, and you will need the frequencies of the nearest transmitting tower.

If the TV shows nothing at all

You have selected the wrong output or have not switched the TV to AV or HDMI. Or they simply did not turn on the prefix, it should have an indicator that lights up green when turned on. The set-top box is turned on either with a button on it or from the remote control.

The set-top box is on, but the TV says "No signal"

If this happens, the antenna is most likely turned off, or the amplifier is not turned on in it. Check if the antenna is connected, maybe it has moved away, pull it out and insert it back. Try auto search again.

The prefix says "No services" autosearch did not find anything

If the channels stopped showing and the set-top box writes "No services", then it's a bad signal. You need to repeat the search manually. The fact is that with a weak signal, auto search can skip channels. On the contrary, a manual frequency search will show the strength of the signal, even a very weak one.

Picture with squares "friezes"

We need to check the signal strength. Press INFO on the remote control. The same behavior of Katrinka digital set-top box observed if you are far from the tower, or a large building interferes with signal reception.

Here the solution is that it is necessary to amplify the signal using an active antenna, or put the antenna outside, raise it higher, and the like.

If the quality of the signal and picture is poor, we adjust the antenna

If the signal intensity is high but the picture quality is not very good, then you must either replace or try to tune the antenna. In the literal sense, turn the antenna in different directions. The mustache is responsible for the meter range, and the ring for the decimeter range. Here is the ring and twist in different directions. It is advisable to move around the room or put an antenna on the windowsill.

Digital TV works great with a reflected signal. But it is very sensitive to obstacles from reinforced concrete walls, plastic window frames.

As a result, we get

If you need to understand why it doesn't work digital television? If the signal is weak, then it must be amplified, using an amplifier or an active antenna. Find the optimal location of the antenna in the room, "turn" it.