How to repair a digital terrestrial receiver. Set-top box for digital television - repair that not a professional can do

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

The "Globo GL50" tuner is designed for receiving DVB-T/T2 terrestrial digital television programs, as well as for playing multimedia files With external media, connected to the USB port of this set-top box. After working for about a year, this tuner broke. The malfunction looked like a complete inoperability of the device, while the LED on the front panel was lit yellow. Repairing such devices is usually impractical, but since in modern digital devices oh little interesting details for future use, it was decided not to disassemble the receiver into parts, but to try to repair it.

The troubleshooting began by checking the functionality 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, the integrated voltage stabilizers were tested on the block board (its marking is M3103-0C). At the output of one of them (KV3VC - according to the U4 microcircuit circuit) there was a voltage of 0.537 V, while the microcircuit body was heated to a temperature above 100 o C in five minutes. This stabilizer directly powers the tuner's central processor, which remains cold. The initial version that one of the ceramic blocking capacitors C23, C24, C35 was broken was not confirmed.

Disabling the stabilizer load did not change the situation: the chip body also became very hot. Because no useful information Neither the failed microcircuit nor the board itself could be found; we had to find out what voltage was required for operation central processor experimentally. To do this, the U4 chip was soldered from the board, and to printed conductor, intended for soldering its output pin (the closest contact next to the inscription “U4”), the output of a powerful laboratory adjustable block nutrition. At a voltage of 1.1 V or less, the tuner processor worked with errors or froze. 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.

Because even if it were possible to find and purchase the same microcircuit to replace the failed one, its installation, in the author’s opinion, is devoid of practical meaning (what burned out once will burn out a second and a third time); It is not enough to simply eliminate the malfunction; you need to eliminate the causes of its occurrence. Probably the KV3VC integrated stabilizer burned out due to overheating - typical fault modern digital devices, ranks first in the number of failures of devices for household and industrial use (in second place is printed wiring, and together they “take away” more than 90% of all failures that did not arise due to improper operation).

Faulty chip pulse stabilizer it was decided to replace it 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 less output voltage. Capacitors 1C1, 1C2 are blocking. Diodes 1VD1 - 1VD3 protect the load from damage if 1DA1 malfunctions. Taking into account the voltage drop on the connecting wire, the output voltage of the stabilizer was approximately 1.28 V.

Rice. 1. Stabilizer circuit

The parts of the new voltage stabilizer are placed on a circuit board measuring 22x22 mm. The KR142EN12A microcircuit is installed on a ribbed duralumin heat sink, which is pressed tightly to the bottom and side walls metal case consoles. 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 getina washer are put on the mounting 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 housing (for example, LM317, KA317). The purpose of the pins 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 console

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

Rice. 3. Circuit board

Rice. 4. Circuit board

The M3103-0C circuit board can be used in other models of DVB-T2 receivers. Since the author has never come across “cold” DVB-T2 set-top boxes (they all get very hot during operation), after finishing warranty period It is advisable to measure and record the input and output voltage values ​​of the stabilizers installed on the board, and also take photographs on both sides circuit board 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 generated simultaneously at the output of a pulsed integrated stabilizer. To improve cooling, you can install a small “laptop” fan inside the console.

After repair, the current consumed by the tuner from the power supply was about 0.75 A, which means that the external complete pulse block power supply with the output parameters specified at the beginning of the article is capable of providing power not only to the DVB-T2 set-top box, but also to the external device connected to it HDD form factor 2.5 inches. If the set-top box is equipped with a power supply built into its case, to reduce the load on it and, accordingly, to reduce the temperature inside the case hard disks 2.5"" is preferably powered from an external unit.

Publication date: 20.01.2016

Readers' opinions

• Genn / 11/12/2017 - 07:30
  Well told - thank you
• admin / 10/31/2017 - 10:17
  Unfortunately, there is no diagram!
• ALEXANDER / 10.30.2017 - 19:00
  Globo GL50 diagram where to find
• Victor / 03/19/2017 - 11:47
  Thank you! Interesting. Educational.
• Vladimir Vasilievich / 29.12.2016 - 13:59
  I’m 69. And I’m still interested. I liked the site and the sections. Since I’m still doing repair work. since 1967.Thank you 73.
• Guest / 02/07/2016 - 20:23
  The article will be useful to a certain circle of people, I liked it.

Since the circuits in free access they don’t and apparently won’t, manufacturing plants respond with silence or replies about certified centers that are licensed to repair a particular brand. 1. THE RECEIVER DOES NOT TURN ON; The LED blinks or dimly lights, or does not light up at all - Apply 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 whether the receiver starts, if so, then we repair the power supply unit. Most often the output capacitor of the power supply requires replacement, we install a new 1000 uF 16 V, although more often they cost 1000 uF 10 V 2. There is 5 volts, the receiver does not start - we check the secondary power converters (five legs with inductors nearby), we measure on inductances 3.3 1 ,8 1.15 volts, if missing, change the microcircuit Information on “five-legged” devices can be found on sites such as monitor, etc. 3. If there is voltage on all stabilizers, as well as in cases where the inscription ASH appears, cyclic reboot, freezes during loading, etc. (the firmware has crashed) - flash the chip flash memory 25Q32 4. DOES NOT PICK CHANNELS - reset settings to factory settings, re-search, change quartz resonator in the tuner (if available), after making sure that the antenna is working properly. If it doesn’t help, most likely the problem is in the tuner, demodulator or processor chip; repair is impractical, especially for non-professionals, it will be scrapped... DO NOT HURRY TO CHANGE THE FIRSTWARE, in this case you can get unnecessary problems on your own, without experience this often leads to a programmer. 5. NO COLOR AT ANALOG OUTPUT - change the quartz near the processor. 6. The image jumps and twitches, the color is distorted - change the capacitor located at the rear wall near the analog outputs. 7. No signal through analog output, but via hdmi there is, the cord is fine, the socket is also - most often associated with burnout of the outputs analog signals from the processor in the absence of buffer protective elements of the circuit. if there are buffer elements (usually installed according to audio channels) - check their serviceability. If there are none, then either viewing via HDMI, or scrap, 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 during inactivity, can be called differently! 9. When you try to update the firmware over the air, the receiver freezes - leave it on for half an hour, the receiver, not finding the update, will reboot and continue working as usual. 10. The receiver reboots when trying to search for channels or install a USB drive into it - most likely, the problem is in the secondary converters “five-legged” and the quality of their wiring, a good voltmeter and oscilloscope is desirable.

Click on the photo! dvb repair t2 Rexant 511

Repairing a dvb t2 set-top box is a process that requires time, tools, and knowledge. Let's try to repair the set-top box for free digital television today. We will show you how the repair process goes. It is possible that this review will help someone fix their receiver.

Rexant 511 repair

The defect is that our console visually works. But after the boot message appears, our receiver does not want to show the menu and television picture.

Rexant 511 is broken, we are repairing it.

A splash screen appears on the TV screen and then the receiver freezes. This process passes through HDMI cable, and through tulips. In order to find the fault, we disassemble our receiver. We won’t talk about safety precautions; all standards must be observed by default.

Repair dvb t2 Rexant 511 using an oscilloscope.

For diagnostics we need an oscilloscope. We turn on the devices and set the necessary modes. We take the probe from the oscilloscope and start checking the indicators on the main board.

Repairing a dvb t2 receiver yourself

As a result of the diagnosis, we identify the suspected malfunction. There is a capacitor on the board, which by all visual signs is normal. After measurements, the capacitor shows deviations from technical characteristics declared by the manufacturer. Accordingly, he does not fulfill his functions.

Repair dvb t2, checking the capacitor.

We solder our problem capacitor. To control, let's check the capacitor, do this in special device, we carry out ESR measurements electrolytic capacitors. We see that our diagnosis was correct, the capacity has deviations.

Repair of dvb t2 set-top box

Take a good capacitor. We check on the device whether it can be installed on the board. We solder it into our main board. It is important to remember that you must act carefully and follow safety rules.

dvb t2 set-top box after repair.

After replacing the capacitor, you can turn on the set-top box and check. We need to do this in order to check whether we need to look for something else or not. IN in this case, you don’t need to solder anything else. Our device is working!

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

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 whether viewing problems are a defect in the set-top box itself or whether it is an issue with the antenna or TV.

The set-top box does not turn on

This is one of the most common digital failures. broadcast consoles. It manifests itself, as a rule, in two variants: the receiver shows no signs of life at all, or the red standby indicator is on, but the set-top box does not go into operating mode. Most receivers start working immediately after being plugged in and do not require turning on from the remote control. If this does not happen, then it is most likely that your power supply is faulty.

Power unit - weakness in any technique and digital set-top boxes are no exception. The power supply 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 being connected to a 220V network. But it often happens that the power supply produces too low voltage or current. In this case, the tuner “tries to turn on” by showing some signs of life, but does not go into operating mode.

Solution to the problem: If the power supply is external (as in the picture), then solve this problem easy and on your own. Power supplies for set-top boxes are usually standard and interchangeable even different models and manufacturers. You just need to make sure that the new power supply produces a voltage of 5V and has the same plug at the end of the wire as the old one. You can buy one of these in specialized stores that sell antenna equipment. In most cases, you can ask the seller to connect the power supply to your receiver and make sure that the problem is resolved.

It is more difficult if the power supply is built into the console. A characteristic feature indoor unit The power supply is a regular plug at the end of the wire. In this case, the power cord is not disconnected from the set-top box itself, as is the case with the external version. In this case, it is best to contact a service center for repairs.

The image freezes shortly after turning on the console

This defect is quite rare, but if it is detected, repairing the receiver is most often impractical. A clear sign such a malfunction: the appearance of image distortion and “freezing” of the picture, which appears 5-20 minutes after switching on digital tuner , after which the problem does not disappear. Similar symptoms occur with weak signal from the antenna, but in the latter case, image distortion does not have a clear connection with the operating time of the DVB-T2 receiver.

The problem could be the same power supply or overheating of the processor. If the power supply is external, you can try connecting another power supply. If not, then the problem is in the processor itself and repairing the product in this case is impractical.

Repair manual for digital TV set-top boxes Reflect Digaital

1 – Problems with the image on the AV output (no image, noise in the picture), sound clicking.
8 – Does not start – hangs on boot; the splash screen appears, and then again blue screen. In this case, the capacitance, when measured, can correspond to the nominal value (low ESR of the capacitor).
9 – Doesn’t turn on – no image at all
13 – seems to slow down too
14 – the picture slows down, the image blurs.
15 is the same as 14, but 14 is more important.
“does not pick up channels” - quartz between C13 – C15

Capacitors in the power supply:


These two capacities affect the performance of the power supply. The power supply either does not work at all (output voltage is 0V) or gives low voltage 1.7V.
Container 2 swells - you can see the insides coming out from below.

Voltage measurements:


1. PSU output – 5V
2. Output AMS1117 – 1.8 V, if there is no such value – go to point 3
3. There should be 3.3V, if not, then the problem is in the capacitor nearby or in the AS11D itself
4. There should be 1.34 V here, but even if there is that much, the problem is still most likely in the capacitor - it’s better to change it. In this case, nodes 2 and 3 show normal voltage values. This is the case when the receiver starts to load and cannot completely do it - the problem is in the capacitor of node 4. We cannot exclude AS11D in this node, but the probability of its malfunction is very small, compared to the probability of a bad capacitance.
THE BIGGEST NUMBER OF PROBLEMS ARE CONNECTED WITH TANK 8 AND 9 (SEE 1 PHOTO) IF THEY ARE NOT EVEN THE PROBLEM, THEN WE CHANGE THEM AS A PREVENTION.