entranceDvb t2 dc100 1hd wiring diagram. Set-top box for digital television - repair that is not within the power of a professional
What to do if the digital set-top box does not work?
If your DVB-T2 digital set-top box for receiving terrestrial digital TV has stopped working, then in some cases you can solve the problem yourself. In this article, we will describe the most common problems that arise when using digital set-top boxes. You will also be able to determine if the viewing problems are a defect in the set-top box itself or the problem is in the antenna or TV.
The prefix does not turn on
This is one of the most common breakdowns of digital terrestrial set-top boxes. It manifests itself, as a rule, in two versions: the receiver does not show signs of life at all, or the red indicator of the standby mode is on, but the set-top box does not go into working mode. Most receivers start working immediately after plugging into the outlet and do not need to be turned on from the remote control. If this does not happen, then it is most likely that you have a faulty power supply.
The power supply is a weak point in any technique and digital set-top boxes are no exception. The power supply unit may fail completely - in this case, not a single indicator on the set-top box lights up at all and the device does not react in any way to the connection to the 220V network. But it often happens that the power supply unit produces an underestimated voltage or current. In this case, the tuner "tries to turn on" giving some signs of life, but does not go into working mode.
Solution: If the power supply is external (as in the picture) then decide this problem uncomplicated and independently. Power supplies for consoles are usually standard and interchangeable even different models and manufacturers. You just need to make sure that the new power supply unit outputs a voltage of 5V and has the same plug at the end of the wire as the old one. You can buy it in specialized stores that sell antenna equipment. In most cases, you can ask your dealer to plug the power supply into your receiver and make sure the problem is resolved.
It is more difficult if the power supply is built into the console. A characteristic feature indoor unit power supply is a regular plug at the end of the wire. In this case, the power wire is not disconnected from the set-top box itself, as is the case in the external version. In this case, it is best to contact a service center for repair.
The image freezes shortly after turning on the set-top box
This defect is quite rare, but if it is detected, repairing the receiver is most often impractical. A clear sign of such a malfunction: the appearance of image distortion and "freezing" of the picture, which appears 5-20 minutes after turning on the digital tuner after which the problem persists. Similar symptoms occur with a weak signal from the antenna, but in the latter case, image distortions do not have a clear connection with the duration of the DVB-T2 receiver.
The problem may be the same power supply or processor overheating. If the power supply is external, you can try to connect another power supply unit. If not, then the matter is in the processor itself and the repair of the product in this case is inappropriate.
In the article, the author shares his experience in repairing a tuner for receiving broadcast programs digital television... The troubleshooting technique described by him is also applicable to other electronic products, where one or more functional units are powered from a voltage stabilizer with unknown output parameters.
The "Globo GL50" tuner 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 malfunction 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 in modern digital devices oh, there are few interesting parts for use in the future, it was decided not to disassemble the receiver into parts, but to try to repair it.
The troubleshooting was started with checking the operability of an external power supply with an output stabilized voltage of about 5.2 V at a load current of up to 1.5 A, which turned out to be serviceable. Further, on the block board (its marking - M3103-0C), integrated voltage stabilizers were checked. At the output of one of them (KV3VC - according to the U4 microcircuit scheme), a voltage of 0.537 V was present, while the microcircuit case heated up to a temperature above 100 ° C in five minutes. This regulator directly powers the tuner's central processing unit, which has remained cold. 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 was also very hot. Since no useful information It was not possible to find either the failed microcircuit or the board itself, it was necessary to find out what voltage was required for operation central processing unit experimentally. For this, the U4 microcircuit 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 terminal (the closest contact next to the inscription "U4"). At a voltage of 1.1 V or less, the tuner's processor was malfunctioning or freezing. At a voltage of 1.2 V, the processor worked without errors in all operating modes of the set-top box, consuming a current of about 0.6 A.
Since even if it was possible to find and purchase the same microcircuit instead of a failed one, its installation, in the author's opinion, is devoid of practical sense (what burned out once will burn out the second and third time); it is not enough just to eliminate the malfunction, you need to eliminate the causes of its occurrence. Probably, the KV3VC integral stabilizer burned out from overheating - typical malfunction modern digital devices, ranks first in terms of the number of failures of household and industrial devices (in second place is printed wiring, and together they "take" more than 90% of all faults that have arisen not due to improper operation).
It was decided to replace the faulty pulse stabilizer microcircuit with a linear stabilizer with an output voltage of 1.3 V on the KR142EN12A microcircuit, the diagram of which is shown in Fig. 1 (reference designations of its parts begin with the prefix 1). The output voltage is set by resistors 1R1, 1R2. The less the resistance of the first of them (with the second unchanged), the less output voltage... Capacitors 1C1, 1C2 - blocking. Diodes 1VD1 - 1VD3 protect the load from damage in case of 1DA1 faults. Taking into account the voltage drop across the connecting wire, the output voltage of the stabilizer turned out to be approximately 1.28 V.
Rice. 1. Stabilizer circuit
The parts of the new voltage regulator are located on a 22x22 mm circuit board. The KR142EN12A microcircuit is installed on a ribbed duralumin heat sink, which is tightly pressed against the bottom and side walls metal case prefixes. 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 greased with heat-conducting paste. Instead of KR142EN12A, you can install KR142EN12B or one of the imported *** 317 series in a TO-220 package (for example, LM317, KA317). The pin assignment of all named 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 link F1 (Fig. 3, red wire), the output is connected to the choke 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 mounting plate can be used in other models of DVB-T2 receivers. Since the author has never come across a "cold" DVB-T2 set-top box (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, as well as photograph the circuit board on both sides like this so that all the inscriptions are visible, this can be useful when repairing a failed device. Please note that several operating voltages can be simultaneously formed at the output of the switching integral stabilizer. To improve cooling, a small "laptop" fan can be installed inside the console.
After the repair, the current consumed by the tuner from the power source was about 0.75 A, which means that the external complete 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 one connected to it. HDD form factor 2.5 inches. If the set-top box is equipped with a power supply unit built into its case, to reduce the load on it and, accordingly, to reduce the temperature inside the case hard drives It is desirable to supply 2.5 "" from an external unit.
Date of publication: 20.01.2016
Readers' opinions
- gene / 12.11.2017 - 07:30
Well told - thanks - admin / 31.10.2017 - 10:17
Unfortunately, there is no scheme! - ALEXANDER / 10/30/2017 - 19:00
Globo GL50 schematic where to find - Victor / 03/19/2017 - 11:47
Thank you! Interesting. Informative. - Vladimir Vasilievich / 29.12.2016 - 13:59
I'm 69. and still wondering. I liked the site and the sections. Since I'm still doing the repair of the r.ap. 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.
The most frequent malfunction set-top boxes for digital television is a failure of the power supply. In such an unpleasant case, it is very good if the model of the set-top box was with an external adapter, bought a new one and look further! And if not! And the power supply was built into the box itself? Then you have to repair or purchase a new one. But maybe there is an easy way out!
Hello dear readers! In this article, I want to share one simple repair method 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 in 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 consoles, but for many, since they are often made according to a scheme very similar for this case. Everything will be on specific example set-top boxes from the D-Color company, namely the DC1401HD model. So by understanding this "high technology" you can repair your digital TV box yourself.
Fast navigation through the article
DIY console repair
What is a sign that it is the power supply unit that has failed in the console, 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 the experienced masters say, "An autopsy will show" I think you can deal with this part of the work without detailed description, just be careful, usually two screws on the back panel, 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 back of the case.
So, the set-top box is disassembled, the power cord is also removed from the connector, it is no longer needed. On the bottom of the case you can see traces of a "fire" that left behind a burnt-out power supply unit.
P.S. The power supply unit here is not a separate unit, as you might think from the name, but a section of the board on which radioelements are located that provide the required power supply voltage for the set-top box.
What is the rework
I will outline the general picture, and for those who are already a little versed in radio engineering, this will already be enough to grasp the basis of the idea and repeat. So, the power supply circuits of this set-top box give out only one voltage - 5 Volts. Since this circuit has burned out and repair may be impractical (in terms of the total 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, with a yellow frame, a section of the power supply unit that has failed is highlighted. The board has already been washed, so no traces of burning are visible. By the way - Among the repairmen, the expression "Burnt 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 there are a lot of similar ones and can be purchased not expensively, 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 the external power supply. Everything! 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 bit of basics 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:
- The primary "Hot" part - Hot, it is called because it is dangerous, connected to 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 there is no need to climb there and we will not connect it to the outlet either.
- Secondary part - Safe there, there is a galvanic isolation from the mains. In the given example, at the points indicated in the photo, a voltage of only 5 Volts comes out from 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, clean the ends of the wires and, having determined the polarity, we solder them: Positive to the diode terminal, on the side where the strip is drawn on it, and the negative to the common bus - frame USB port will be a convenient place for this. If you do not know how to determine the polarity, even without a device, see additional materials at the end of the article.
We connect new block power supply to the network, take it out of standby mode, check what happened.
All OK! It remains to lay and secure the wire so as not to accidentally pull it out, collect everything in a heap and use it. In the end, it will look like this.
If you need ideas on how to attach the wire to the box? How to determine polarity without a device? Or how to solder the wire from the bottom of the board? - Then these additional materials are further in the text.
Since there are no schemes in the public domain for them, and apparently there will not be, manufacturers answer with silence or with unsubscriptions about certified centers that have a license to repair a particular brand. 1. THE RECEIVER DOES NOT TURN ON; The LED is blinking or dimly lit, or not lit at all - We supply 5 volts with external source(with an output current of at least 1.5 amperes) to the output capacitor of the power supply unit, observing the polarity, we see if the receiver starts up, if so, then we repair the power supply unit. Most often, the output capacitor of the PSU requires replacement, we put a new 1000 microfarad 16 V, although more often they stand at 1000 microfarads 10 v 2.5 volts are available, the receiver does not start - we check the secondary power converters (five-legged with inductances nearby), we measure on inductances 3.3 1 , 8 1.15 volts, if not, we change the microcircuit Information on "five-legged" can be found on sites such as a monitor, etc. NS. (the firmware has flown) - we are stitching flash chip memory 25Q32 4. DON'T CATCH CHANNELS - reset to factory settings, search again, change the quartz resonator in the tuner (if available), after making sure that the antenna is in good working order. If it does not help, most likely the problem is in the microcircuit of the tuner, demodulator or processor, repair is inappropriate, especially for non-professionals, for scrap ... DO NOT HURRY TO CHANGE THE FIRMWARE, in this case you can get unnecessary problems on your head, without experience this often leads to the programmer ... 5. NO COLOR ON ANALOG OUTPUT - change the quartz near the processor. 6. The image jumps and twitches, the color is distorted - we change the capacitor located at the back wall near the analog outputs. 7. There is no signal through the analog output, but through the hdmi there is, the cord is in order, the jack is also - most often associated with the burnout of the outputs analog signals from the processor in the absence of buffer protective elements of the circuit. in the presence of buffer elements (more often installed via sound channels) - check their serviceability. If there are none, then either viewing via HDMI, or junk, well, or replacing the processor ... Do not connect the set-top box to the TV while it is on! 8. The receiver turns off by itself - look in the menu in additional settings the item responsible for the sleep timer, or shutdown when idle, can be called differently! 9. When you try to update the firmware from the air, the receiver freezes - leave it on for half an hour, the receiver, not finding the update, will reboot and continue to work as usual. 10. The receiver reboots when trying to search for channels or install a USB drive into it - most likely, the matter is in the secondary converters "five-legged" and the quality of their strapping, a good voltmeter and an oscilloscope is desirable.