Samsung ue32f5300ak no image, backlight available. Why does the backlight disappear on a Samsung UE32F6200AK TV?

Hello, Ivan! You did not say how long you have had the TV in use. The malfunction you described usually occurs 1.5-2 years after purchase. If you are knowledgeable in electronics or have a suitable friend, then you can try to solve the problem yourself. What blocks and parts are to blame for the malfunction you described?

Panel CY-HF320BGSV1V

When an image appears and disappears almost instantly, you should first check the electrolytic capacitors of the filter that powers the LED driver, as well as those in the secondary rectifiers of the power module. It may also happen that there is a break in the LED lines. You can try to identify this problem without disassembling the panel, but for this you need a source direct current several tens of volts (a regular tester is not enough - its voltage is too low and the diode junctions simply will not open). But sometimes you can’t do without opening the panel.

To solve the problem you will have to disassemble the LCD TV

LEDs

They are most often to blame for the absence or periodic disappearance of the image. To reveal the truth, you will have to open the panel. If several faulty LEDs are found, then you should pay attention to the protective zener diodes. It is they who, after thermal breakdown, “pass” current to the LEDs, which also become unusable. Moreover, if one LED breaks down, the TV will continue to work as before: its lenses will mask the dark spot, and the owner will not know anything until the LEDs begin to fail one after another. As a result, TV may not even last up to a year and a half of work. What can be done?

Finalization

Even the manufacturer himself sends recommendations to its authorized centers on how to correct this shortcoming of its products. In this case, it is enough to reduce the current supplied to the LEDs by 10%. This can be done by increasing the value of the corresponding resistor. As a result, the brightness will not decrease, and the TV will work longer.

Samsung ue39f5000ak no image, dark screen . Is there sound. If you illuminate it with a flashlight, you can see the image, therefore no backlight.
From time to time the image appears, sometimes the entire screen is illuminated evenly, sometimes one part is darker, then again it disappears completely.

In modern LCD TVs with LED backlighting, the loss of this backlight is already a typical defect. There are several reasons for this.
1. Poor quality LEDs.
2. The caring attitude of equipment manufacturers towards their customers.
3. Deliberately reducing the service life of devices by introducing “errors” into the design.

Samsung, specifically regarding the defect of this model, as well as other similar ones, issued a bulletin for warranty repair of TVs, but they didn’t even mention it to their customers. Many thousands of televisions were produced. During the warranty period, the defect appeared in a maximum of 10 percent, the rest will shell out money, paying service centers to eliminate the factory defect. In fact, Samsung is engaged in obvious fraud. In the automotive industry, it is common practice to recall a defective batch. This practice does not exist in electronics. I hope someday they will be sued and forked out a tidy sum.

To eliminate the defect we will need:

1. Disassemble the TV.
2. Remove the matrix and

get to the LED strips.
3. Find all faulty LEDs and replace them, or replace the entire strips.
4. Eliminate the root cause of the defect - reduce the current passed through the LEDs.
5. Assemble the TV.

For those who have never done anything like this and want to repair their TV, I’ll write right away - there are many chances to kill the matrix. Can crack during removal and installation. You can accidentally break one of the cables. They are quite fragile.

Based on this similar work It's quite expensive. To roughly understand what I’m writing about, before you start repairing, ask about the cost of a new similar device. If you ruin your TV, you'll have to buy a new one. If you kill someone else's, you will also have to fork out money. It all depends on how the master agreed with the owner of the TV. If the master takes a significant amount, he is responsible for the device. If he does it inexpensively, then of course the master will not want to take responsibility for pennies.

On this moment time, end of June 2016, the cheapest Samsung from 39″ on Rozetka and in regular stores costs more than 12,000 hryvnia. Accordingly, it is advisable to charge an amount of 2000 hryvnia for this repair. Which is generally beneficial for the owner.
There are amateurs who take it for a smaller amount. It's the owner's business. Apparently they have never been hit before.

1. Disassembling the TV is not difficult.
2. Be careful when removing the matrix. I do this on a large table on which I lay a cloth so as not to scratch the display and front panel.

Samsung is so poor that they didn't have enough money for four extra bolts. For such a price...
There are also side loops on the matrix. Be careful when removing glass. By the way, the matrix glass is quite thin and sags under its own weight. I usually put it on the table, resting it against the wall, and prop it up from below with something heavy and unstable, like a thick book, so that it doesn’t fall.

Two boards are connected to the matrix via cables, which are secured with latches. Snap off very carefully! The trains are flimsy!
The latch is slightly upward, carefully lift the board and move it slightly in the direction of the arrow. Then the other edge. Then pull out the board completely.

3. We turn the latches and remove the white reflector in order to get to the LEDs.

4. In my case, three LEDs and six SMD zener diodes on a common strip were faulty. One LED was clearly black, I looked for the rest using a power supply on which I set it to 3 volts. Somewhere I connected it to existing contact pads, somewhere I stripped the traces down to copper and connected them.

LEDs can be broken or shorted. Therefore, it is easier to judge by the glow than by the resistance. Although from a regular ohm tester the LEDs also light up. Only weaker.
5. If there is somewhere to order entire strips, it is better to order and replace them. In this case, I didn’t find any similar ones, so I replaced the LEDs.
6. Button lens it is pryed up and removed with a screwdriver, flux and low-melting solder are applied to the LED, and removed with a regular soldering iron. Sometimes I use two soldering irons at the same time. I take LEDs either from disassembly or from replaced strips. As a rule, out of 5-10 diodes on them, only one or two die on the bar. I cut the live LED with ordinary metal scissors along with a piece of the board, I also glue it entirely to a previously prepared place, on double-sided tape and solder it. It holds up perfectly, the LED does not overheat when soldering, the glow remains the same uniform.

7. Zener diodes SMD, judging by the designation, 12 and 24 volts connected in series. I set two to 18. The voltage when working on two zener diodes is 20 volts. They are there as varistors. They break through when the voltage is exceeded. They should have) But they made it after the LEDs.

8. Modification of power supply L42SFV_DSM (BN44-00609F) old name in brackets.
In order for the TV to become more reliable, it is necessary to limit the current through the LEDs by at least 20%. To do this, we will modify the power supply. Two 4.7 ohm SMD resistors connected in parallel are responsible for the current. R9209, R9210. With the native resistance of the resistors, the current is approximately 280 mA. As a rule, it is written on the board what current is for what diagonal.
In order to reduce the current, we will replace the resistors from 4.7 to 5.6 ohms. The current should drop by about 20%. This is visually noticeable by a slightly weaker glow, but I was not able to really measure it. My instruments showed anything but current. The pulse component of the PWM converter introduces distortions into the device readings.

If If you have any questions, ask and we will answer. Little details can be found here in the comments.
If the question is more serious, go to the forum

Repair of electronic equipment usually begins with its external inspection and fault diagnosis. In this case, you should inspect everything internal components TV SAMSUNG UE32F5300AK. Many visible changes in the state of elements make it possible to determine the further direction of troubleshooting.
If the UE32F5300AK TV does not turn on, does not make any sounds when turned on, and no indicators on the front panel light up or blink, there is a high probability of a malfunction in the power module BN44-00605A, which is made on the same board with a power converter for backlight LEDs (LED driver).
The 220V AC mains voltage is rectified by a diode bridge and filtered by electrolytic capacitors, which result in a DC voltage of about 300V. Flyback converter controlled by PWM controller S3310, provides the necessary rectified voltages in the secondary circuits of the pulse transformer to power the MainBoard and LED driver. To correct the Power Factor, a passive filter of two back-to-back chokes is used at the network input.
If the mains fuse is broken, it is necessary to check first the power semiconductor elements - rectifier diodes and transistors, which are often found in a state of breakdown in such situations.

Mos-Fet switches used in switching power supplies (SMPS) extremely rarely fail for no reason, which must be looked for by checking other elements of the circuit. Often a breakdown is caused by malfunctions of electrolytic capacitors or semiconductor elements in the primary circuit, or by broken resistors in stabilization circuits. The PWM controller chip can also be the cause of breakdown of the converter power switch.

If the SAMSUNG UE32F5300AK does not have an image, there is sound and the channels are switched, there is a possibility of a malfunction in the LED circuit of the HF320BGA-B1 panel backlight, or in their power converter - the LED driver, which is a step-up flyback. DC-DC converter. The LED current is stabilized by a PWM controller SEM5027A.
Sometimes, when you turn it on, the image appears and immediately disappears. In such cases, it is necessary to check the electrolytic capacitors of the driver power filter, including those in the secondary rectifier of the main power supply.
In most cases where there is no backlight, it becomes necessary to disassemble the panel in order to check the LEDs, connectors, cables and all contact connections. If only one or several LEDs in one line do not work, then they are broken and should be replaced.
To check the LED strips for breaks without disassembling the panel, for example, a current source will help. It is impossible to open series-connected PN junctions with a simple multimeter; a voltage of the order of several tens of volts will be required.

Repair motherboard BN41-01958A must begin with diagnosing and testing all linear stabilizers or power converters of its microcircuits. Sometimes an update may be required software(BY) - flashing FLASH or EEPROM.

If you suspect a malfunction of the DNTS403EH105A (BN40-00262A) tuner, first of all you need to make sure that there is power at the corresponding pins and exchange via the I2C control bus.

Remember! Attempts at self-repair by users of the SAMSUNG UE32F5300AK TV without the appropriate qualifications and necessary experience can lead to serious negative consequences!