How to check the backlight of the LCD TV

Today, a modern LCD TV can be found in almost any home. It is a source of information and entertainment, so it is very unpleasant when the TV fails. Most often, in such a technique with a liquid crystal display, the backlight of the matrix breaks, but this malfunction is easily eliminated if you know the basic principles of diagnosis and repair.

How to check the LED backlight of the TV?

The malfunction of the LED backlight of the TV matrix has a number of signs that you should definitely pay attention to before starting the analysis:

• When you press the appropriate button on the remote control or the front panel, the TV turns on, the sound goes on, but the image is missing.
• The included TV responds to pressing the buttons on the remote control, switches channels, adds volume, but the screen remains dark.
• If you look closely at the screen matrix, you can see a very dim image on it.

The presence of such factors allows us to talk about the failure of any of the line of LEDs or the backlight control driver. In any case, you will need to disassemble the TV to fix the defect and restore performance.

Dismantling the device: nuances and features

The range of modern LCD TVs is incredibly extensive, but in most cases their design is quite typical, and they are disassembled on a single principle. The disassembly procedure takes place in several stages:

• Preparation of the workplace. You should first take a set of tools, several tables for laying the matrix and scattering films, a soldering iron, antistatic gloves and napkins.
• Removing the back cover. As carefully as possible, the TV should be placed with the matrix on the table, remove the stand, unscrew all the bolts holding the cover.
• Dismantling the T-con board. Easily removed after disconnecting loops and unscrewing the bolt.
• Removing metal protection and unscrewing the decoder unit.
• Removing the front frame of the TV by unscrewing the mounting bolts around the perimeter of the device.
• Dismantling of decoders from rubber mounts.

ATTENTION. Decoders are very fragile and critical devices, so they should be removed with extreme caution!

• The matrix remains on the table and you can proceed directly to the search and replacement of faulty LEDs or the controller in the backlight system.

LED fault detection

The reason for the lack of backlighting on the LCD TV display may be the failure of the driver or the LEDs themselves. You can determine which device has broken in the following ways:

• If the driver fails, any voltage is absent on the diodes - this can be checked by connecting a multimeter.
• If the LED bar is faulty, then a voltage of 150-200V will be applied to the power terminal. You can also check each of the diodes with a multimeter.

Replacing LEDs in the backlight

Having identified the faulty LED-lamps in the matrix illumination, they should be replaced with new ones. They are dismantled quite simply - you need to peel the bar from the case using a building hair dryer, as well as remove the lenses. Next, you can start soldering the LED itself and soldering a new one. It is imperative to wipe the diode against flux and carbon deposits well, as otherwise, the image on the TV display may be distorted.

If several LED elements burned out on the diode backlight strip at once, then you can replace the strip with a new one. The procedure is also performed by soldering, but takes much less time.

Final stage

After soldering new diodes instead of burned ones, you should build the driver and check how the backlight works. If everything is normal and within a few minutes the LEDs do not start to turn off or blink, you can start assembling the TV.

Particular attention should be paid to connecting all buses and loops, doing this as carefully as possible, being careful not to damage the connectors. When the assembly is completed, it is necessary to turn the TV on and off several times with the matrix installed and all the blocks, thereby giving an intense load to the driver and the LED elements themselves.