DIY dexp TV repair

DEXP F49B7000T
matrix: K490WD7
lane: MM20-151HP102-902503
PSU: K-PL-L01 (L6562D, L6599AD, AP3041M-G1)
opened the trough, the backlight consists of 9 strings of 6 led each (3 lines * 3 strings = 9 * 6 = 54 led), all integers, the voltages on 3 lines are the same, when turned on, they jump to 68v and fall to 31v, apparently the protection is triggered, the driver AP3041M- G1, the key transistors at the output are intact, caught on the internet - turn off the protection of the AP3041 from 13pin to the ground, the LED or just close it - it does not work, the SMD elements rang out - the norm, roughened up the protection R89 = 10k replaced it with 47k. AP3041M ordered new ones on the way.
The plant does not want to, what else to dig?
I attach the diagram

lighting the backlight forcibly from a Chinese device, it is clear that the TV is working

hatsky opener
Posts: 3551

sanych75,

I didn't understand anything, how many volts of LEDs?

Do-it-yourself TV repair is a responsible business, since today a large number of different models (LCD, LSD, CRT) are presented on the market, each of which has its own technological features. Therefore, the approach to each type of TV is individual; in some cases, special skills will be required (knowledge of electronics, experience with a soldering station).

Before proceeding with the repair of television equipment, it is necessary to find out the cause of the problem.

The most common problems are:

1. TV screen does not turn on - this can happen with an old picture tube screen and with the most modern television panel. Basically, this symptom is characteristic of a blown fuse. When repairing, it should be borne in mind that the appropriate fuse must be selected for each model. And also experts recommend paying attention to the diode bridge, power supply, wire, perhaps the cause of the malfunction lies in these elements. Read also what to do if Samsung TV does not turn on.

1. Faint, barely noticeable picture - such a breakdown happens with LCD / LCD monitors. The most likely cause of the malfunction: faulty diodes, device backlighting.
2. There is no sound, the screen "wheezes" - most likely, the sound amplifier or microcircuit is out of order. Also read what to do if there is sound, but there is no picture.
3. Monitor is on, no picture - Perhaps the cause of the problem is in the video processor or in the receiving unit.

You should be aware that if a darkening of the board or rupture of elements is detected during a visual inspection of television equipment, then it is not recommended to immediately start replacing parts. Since such factors indicate a short circuit that could have occurred in another section of the TV. Therefore, if you do not eliminate the cause of the short circuit, but simply change the failed elements, then the situation will repeat itself.

To repair television equipment, the following tools and equipment may be required:

• Screwdriver Set;
• hex keys (in rare cases);
• pliers;
• soldering station (for repairing modern monitors);
• screen layout (can be downloaded on the Internet);
• multimeter;
• oscilloscope.

Many LCD screen problems can be dealt with on your own. But you should know that these screens require more careful handling than, for example, CRT TVs.

First of all, the user needs to study the instructions for his model, and only after that start repairing the LCD or LED screen. You should be aware that LCD TVs use fluorescent bulbs for backlighting, while LEDs use LEDs.

The TV may not function due to lack of power, to check this, you need to do the following:

1. Open the back cover of the LCD TV with tools.
2. Disconnect the wires that are connected to the device matrix.
3. Connect a working light bulb to the contacts.
4. Some panels have more than one light source, in which case they must be tested as well. This can be done as follows: pull out the TV matrix and connect it to the network, it will immediately become clear which lamp is out of order.

After the faulty luminaire is found, it must be replaced. This procedure should be carried out as carefully as possible. In most cases, the lamp can be taken out even without removing the matrix - you need to move the protection elements and get the burned out part using a soldering station. Then a new lamp is installed in the same way.An important rule is that the new lamp must be completely identical to the old one.

Another common problem with these models is damage to the monitor. But in this case, it is not advisable to repair LCD TVs, since it is easier to buy a new screen. This test scheme can also be used to repair plasma televisions of all types. Read also how to fix the LED backlight yourself.

Each manufacturer has its own weak points, so below is a selection of the most common LCD screen breakdowns.

Often, users of this brand are faced with such a problem that when turned on, the device beeps without interruption. This symptom usually indicates that a leak has occurred. It is recommended to try replacing the preout stage diode.

Another common problem is that the monitor turns on and off itself. The main reason for this breakdown is a failed transistor, it is necessary to replace it. It is recommended that such malfunctions be eliminated on their own only by people who have experience in repairing television equipment.

DIY Philips TV repair is recommended if the problem is minor: settings are lost, cable replacement is required.

If the breakdown is complex, then it is better to entrust its elimination to specialists who will not only professionally perform repairs, but also issue a guarantee. Therefore, if the repaired screen stops working again, the user may demand a refund.

LG flat screen owners may have a problem saving settings. Such a problem does not require contacting the masters, you can repair the LG TV yourself. It is enough to switch the device to another operating mode, and all settings will be saved.

As well as in the case of other LCD models, if the problem is serious, then it is not recommended to repair an LG TV with your own hands, it is better to contact a specialist.

Despite the fact that today the majority of consumers prefer the most modern plasmas, CRT screens are still in demand. These TVs have their advantages: they are inexpensive, easy to operate, and the quality of the transmitted picture is still high.

The main problems with CRT devices:

• the CRT TV does not turn on - just like on devices of a different type, first of all, you need to check the integrity of the fuses;
• a diode bridge malfunction is a common problem with CRT receivers, you can fix the TV only after making a "ringing", you will need a multimeter from the equipment;
• breakage of the posistor is considered the most serious problem; in order to check, it is necessary to turn off the power circuit of the TV, then start it again. After, observe the lamp, if it goes out, it means that the posistor is out of order. First of all, you need to adjust the resistance of the network, and then replace the part;
• burnout of a transistor or capacitor - such a malfunction can be easily replaced by visual inspection (on black carbon parts), repair is carried out by replacing the part.

Below is a list of problems encountered by owners of CRT TVs.

1. The Rubin TV buzzes loudly when connected - most likely, the photodetector needs to be replaced.
2. The ruby ​​does not turn on, the indicator does not light up - voltage surges in the transistor.

1. The Horizon TV does not have a blue tint, as well as the white balance is disturbed - this is mainly due to a break in the resistor.
2. There is sound, no image - the cause of the problem lies in poor contact of the power connector of the screen board. It is recommended to use a soldering iron to solder the harness into the Horizon TV board.

1. The screen does not turn on - there is a problem with the power supply.
2. A horizontal strip appears on the monitor - repairing a Vityaz TV consists in fixing a problem in the frame scan microcircuit.

Since the malfunction of the power supply is one of the most common problems of all types of TVs, it is necessary to study it in more detail.

Since all models of LCD monitors do not have fundamentally different design differences, therefore, the diagram below can be applied to all TVs (Toshiba, Horizon, Samsung, Sony, Rubin).

Repair of monitors equipped with a picture tube, for example, such as (ruby, sharp 2002sc, sony trinitron, vvk), as well as repair of Samsung TV, Panasonic. always starts checking the power supply.

Testing is carried out using an incandescent lamp, but before performing the procedure, it is necessary to disconnect Sharp c2002sc, Samsung or another screen from the load (horizontal cascade). The horizontal scan voltage can vary from 110 to 150 V, it depends on the size of the picture tube. It is required to find a sweep filter capacitor in the TV circuit. Next, you will need to connect a light bulb, in order to remove the load, it is necessary to unsolder the choke and the fuse through which the JV element consumes power. This scheme is used for sharp screens since 2002sc.

After that, connect the power adapter to electricity and measure the voltage, if the values ​​exceed the norm, you will have to check the feedback circuit of the power supply. If the power supply unit is in good condition, then the light bulb is removed and all the elements are soldered into place. This is the basic information on how to repair a TV with your own hands.

It is no secret that a breakdown of a television receiver can ruin the mood of any owner. The question arises, where to look for a good master, do you need to take the device to a service center? You need to spend your time on this, and what is important - money. But, before calling the master, if you have basic knowledge of electrical engineering and know how to hold a screwdriver and a soldering iron in your hands, then repairing the TV with your own hands in some cases is still possible.

Modern LCD TVs have become more compact and easier to repair. Of course, there are breakdowns that are difficult to detect without special diagnostic equipment. But most often there are malfunctions that can be detected even visually, for example, swollen capacitors... With such a breakdown, it is enough to evaporate them and replace them with new ones with the same parameters.

All TV sets are the same in their structure and consist of a power supply unit (PSU), a motherboard and an LCD backlight module (lamps are used) or LED (LEDs are used). It is not worth repairing the motherboard on your own, but the power supply unit and screen backlight lamps are quite possible.

As already mentioned, the design and principle of operation of LED and LCD TVs, regardless of the manufacturer, are the same. Of course, there are some differences, but they do not play a significant role in the diagnosis of faults. Often, in the event of a problem with the power supply, the LCD TV does not turn on at all, while there is no indication, or it turns on for a while and turns off spontaneously. Using an example, the repair of a DAEWOO LCD power supply unit (can be applied to plasma) is considered, which is not much different from repairing an LG TV, as well as Toshiba, Sonya, Rubin, Horizon and similar models.

1. First of all, before you repair the TV, you need to remove the back panel of the device with a screwdriver by unscrewing the screws. On some models, the rear wall may be latches installedwhich must be handled with care so as not to break them.
2. After removing the cover, you will see the power supply unit, consisting of several modules on the left, and the motherboard on the right.
3. 
4. On the power supply board you can see 3 transformers: the bottom one is the mains rectifier choke, the top one on the left (large) feeds the inverter, and on the right is the standby power supply transformer. You need to start checking with it, since it turns on the standby mode of the TV receiver.
5. Duty transformer when the device is connected to the network, it should give out a voltage of 5 V. In order to correctly find the wire on which you need to measure the voltage, you can use the diagram, or you can see the markings on the case. In this case, opposite the required contact is written - 5 V.
   

Measurement is taken first open circuitby connecting one probe to the found contact, and the other to the cathode of the diode on the radiator. In this case, there is no break.

Further, one tester probe can be attached to the body of the device, the other to the previously selected contact, and measure the voltage, having previously connected the telly to the network. In this case, the device shows 1.5 V, instead of the required 5 V. Such readings of the transformer indicate that it is working, but not at full strength. The reason may be dry condenserlocated below, or swollen - above the transformer.

To remove the parts that have become unusable, it is necessary to remove the power supply board. To do this, first disconnect all wires and the matrix cable coming from the inverter and the system board. So that in the future, after repairing the power supply, you do not get confused where what is connected, you can take a picture of them before disconnecting the wires and loops.

Now you can remove the entire LCD TV power supply by unscrewing the 4 screws. After removing it, it is very important discharge all capacitorsto avoid electric shock.

We solder the defective capacitors and replace them with new ones, observing the polarity.

The assembly of the device takes place in the reverse order: the board is screwed into place, all connectors and cables are connected, the rear panel of the unit is closed.

We again measure the voltage on the transformer of the TV's power supply (the device should turn on) and see that it has become 5v. When you unfold the repaired TV receiver, you will see that it works.

As you can see from the review presented above, repairing TV power supplies with your own hands is not such an overwhelming task. Following this description, you can also repair plasma TVs.

Do-it-yourself TV repair with a kinescope, for example, such as: Rubin, Horizon, Sharp 2002sc, LG TVs, as well as repair of the Vityaz TV, begins with checking the power supply unit for operability (this is done if the unit does not turn on). It is checked using incandescent bulbs for 220 V and a power of 60-100 W. But before that, be sure to disconnect the load, namely the horizontal output stage (SR) - connect a lamp instead. The CP voltage ranges from 110 to 150 V, depending on the size of the tube. Must be found in the secondary circuit SR filter capacitor (its values ​​can be from 47 to 220 microfarads and 160 - 200 V), which stands behind the SR power rectifier.

To simulate the load, you need to connect a lamp in parallel to it. To remove the load, for example, in the popular Sharp 2002sc model, it is necessary to find and unsolder the inductor (located after the capacitor), the fuse and the limiting resistance through which the CP stage receives power.

Now you need to connect the power supply to the power supply unit, and measure the voltage under load. The voltage should be between 110 and 130 V if the CRT has a diagonal of 21 to 25 inches (as in the 2002sc model). With a diagonal of 25-29 inches - 130-150 V, respectively. If the values ​​are too high, then it will be necessary to check the feedback circuit and the power supply circuit (primary).

It should be noted that electrolytes dry out during prolonged operation and lose capacity, which, in turn, affects the stability of the module and contributes to an increase in voltage.

When the voltage is too low it is necessary to test the secondary circuits to exclude leaks and short circuits. After that, the diodes for the protection of the power supply of the SR and the diodes for the power supply of the vertical scan are checked. If you are convinced that the power supply unit is working properly, then you need to disconnect the lamp and solder all the parts back. This check can also come in handy when doing DIY Philips TV repairs.

Another common breakdown of the TV that can be eliminated is the burnout of the backlight lamp. In this case, the TV receiver, after switching on, flashes the indicator several times and does not turn on... This means that after self-diagnosis, the device notices a malfunction, after which the protection is triggered. That is why there is no image on the screen.

For example, a Sharp LSD TV receiver with this malfunction was taken, although in this way it is possible to repair Samsung TVs, Sony Trinitron, Rubin, Horizon, etc.

To fix the TV, you need to remove the back cover from the TV. This requires a screwdriver or screwdriver.

Next, you need to be careful disconnect loops from the matrix.

The next step is to detach the control panel from the case. You do not need to remove it, you will still need it to turn on the device.

The remaining loops also need to be disconnected. Then it is necessary to remove the housing on which the electronic boards are fixed.

Before removing the matrix, unscrew front frame... We remove the matrix itself and filters, snap off the side mounts.

We connect the power and hold down a few keys to enter service menu... This will keep the lamps on for a while.

The figure below shows that after turning on the lamps, the 5th from the top turned out to be inoperative. Disconnect it and replace it with a new one - now all the lamps are on when checking.

The assembly takes place in the reverse order.

After that, you need to turn on the TV receiver and enter the service menu for reset lamp error counter... If this is not done, the device will not work. Entering the menu, you need to find the corresponding line and reset by selecting ok. Now the repair of the LCD TV set is finished. Tests show that the unit is operating normally.

Thus, you can repair the Philips and LG TV with your own hands, and other LCD panels, as well as devices with LED backlight (LED). Owners of the latter type of devices should read the article on repairing LED backlighting, where the whole process is described in detail using the example of an LG TV.

Among the typical and simple reasons that the TV set does not turn on, there may be a remote control or a lack of signal from the antenna cable.

If the TV does not turn on with the remote control, first, you need to make sure the batteries are good. If they are shrunken, replace them. Often the TV set cannot turn on due to contamination of contacts under the buttons. To do this, you can disassemble it yourself, and clean the contacts with a soft cloth from accumulated dirt. If your remote control has been dropped, it is possible damage to the quartz emitter... In this case, it must be replaced. Well, if you filled the remote control with water or some other liquid, and it did not work after disassembling and drying, then it will have to be replaced with a new one.

You can learn more about fixing the remote control in the following video or article.

When repairing TVs LG, Sharp with LCD, Rubin, Horizon with the same screens, a situation often arises when it does not turn on when the device is in good working order.It turns out that the reason may be no TV signal in the antenna cable. This happens due to the operation of the noise suppression protection (in Rubin TVs, they began to install it not so long ago), and the unit goes into standby mode. Therefore, if you find your TV set inoperative, you should not panic, but you need to check the presence of a signal from the transmitting station.

In conclusion, we can say that when you decide to repair a TV set yourself, you should soberly assess your abilities and knowledge in this matter. If you do not feel confident, then it is better to entrust this matter to a telemaster, especially since nobody canceled 220 V, and ignorance of basic safety rules can entail unpleasant consequences.