Repair the LED back light. LED TV - Extra Know

Repair the LED back light. LED TV

Repair the LED back light. LED TV

Hi guys!
Sometimes, when repairing, it is difficult to get what you need for LCD back lighting. A luminous (CCFL) lamp. In this case, you can put the lamp back on the LED. This change is not difficult and spare parts have no particular problems.
This article suggests the principles of such reconstruction in the form of specific education.
  Replacement work LCD backlight on led:


   1.  Disassemble the monitor or TV. Carefully remove the wire from the board after removing the plastic case, remove the metal frame from the LCD module and remove the matrix. Be very careful not to damage the fragile connection loops when using the matrix. If everything is done correctly, full access to electronic boards, power inverters and lighting elements opens.
2. Canister separation lamp If installed without a canister in the matrix or lamp itself.
3. Remove and dispose of the old bulb. Be very careful because the element contains CCFL mercury.
4. Go to the replacement step. To replace all lamps (to measure lamp length and multiply by number), you must purchase an LED strip with margin. It should be as narrow as possible and have at least 120 LEDs. To make the backlight easier to see, it is better to light the LED white.
5. The tape with the LED needs to be attached to the double-sided tape where the lamp was. The wires of the old lamp are then soldered to the contact terminals of the tape and insulated with hot melt adhesive. You can immediately see the performance of this design by connecting the wires to an external power source.
6. You should now connect the back light to the power board of your monitor or TV. To do this, find the jumper labeled "12 V" and solder the back light wires, taking into account the polarity. Reassemble the monitor in reverse order and enjoy the invention.
The backlight will work if the device is connected to the network.
You have to work hard to control the backlight and operate it in normal mode. The wires to the LEDs must be powered in such a way that the backlight can be turned on when the brightness is adjusted by pressing the On / Off button. There are two options for this.
1. Create your own power schemes and adjust the backlight brightness.


    On a monitor or TV power supply chip, we are looking for a plastic box (connector) with a signed wire removed from each socket on the board.
    Here we are interested in the conclusion "DIM". He is responsible for signal ON / OFF and adjusts the brightness by changing the duty cycle of the PWM controller. The pulse duty cycle changes until the desired brightness level is set, and the threshold value exactly matches the switch on and off.
    Now an N-channel field effect transistor (field) is required. The wires of the minus LED strip are soldered to the drain, the common wire of the backlight is connected to the source (gate), the gate (gate) is connected through a 100-200Ω resistor, and all wires are connected to the "DIM" pin .
It is still good to solder the jumper from the inverter power supply of the old lamp, so the backlight is controlled by the new inverter.


Over time, it seems that the newly purchased equipment is already broken. So I worked 10,000 hours and ordered the monitor lamp to live for a long time (AOC 2216Sa). Initially, the backlight was not turned on for the first time (the backlight turns off after a few seconds after turning on the monitor). Turn the monitor off / on after 3 seconds, turn off the monitor after 5 seconds, wait 10 seconds, then turn the monitor on and off. You can not turn on the backlight already, regardless of how many times you turn on the power. The lamp of God who took it to the world turned out to be black and legally scrapped. The replacement lamp (if you purchased a new lamp of the correct size) did not succeed (the monitor was able to turn on the backlight several times, but quickly returned to the on-off mode). And if you find out why your monitor's electronics already have a problem, you'll get an idea. It's easier to assemble your own monitor backlight into an LED than to repair an inverter circuit for a conventional CCFL lamp. Especially since the network has already found an article that shows the fundamental possibility of such a replacement.
We disassemble the monitor.
  I have already written a few articles about the disassembly of monitors, and all monitors are very similar, so I'll briefly explain.
  1. Turn off the only bolt on the floor that holds the monitor shipping lock and the back wall of the case
 The backlight unit is disassembled in the same way. Instead of a metal frame, the backlight is held in place by a plastic frame, which simultaneously places the plexiglass that is used to scatter the backlight. Most latches are on the side and similar to the metal frame of the matrix (opened by a flat screwdriver). There are several latches on the opening side inside (the latch must be screwed into the case).
  Initially, we memorized the location of all parts to be removed, but found that they were not correctly assembled, and that the latches on the other side of the metal frame and the locking projections of the plastic frame, which retained the backlight, The distance of these is "wrong".
  That's all. We dismantled the monitor.
LED strip lights

Initially it was decided to use white LED 3528 ~ 120 LED to make backlight of LED strip. The first thing that turns out is that the width of the tape is 9mm and the width of the backlight lamp (and the position of the tape) is 7mm (actually there are 2 standard 9mm and 7mm backlights, but in my case it was 7mm). So after examining the tape, I decided to cut 1 mm from each corner of the tape. This does not affect the conductive tracks on the front of the tape (and does not lose 1 mm of characteristic from the 475 mm backlight length because of the small current behind the entire tape). High-done:
Likewise, the LED strips are neatly arranged along the entire length (what happened before and after the trimming in the picture).
  We need two 475mm tapes (19 strips with three LEDs).
  I wanted to have the monitor backlight function the same way as a standard backlight (ie, the monitor controller is turned on and off), but like previous CRT monitors, I wanted to adjust the "manual" brightness. This is a frequently used feature and I was tired of scrolling the screen menu each time (the left and right keys on the monitor do not adjust the monitor mode, but the volume of the built-in speakers must be changed each time through the menu). To do this, my monitor's documentation is found on the network (attached at the end of the article) and appears on the page with the power board according to the useful + 12V, On, Dim and GND schemes.
  Advantages :

    Bright enough
    The step-down regulator does not heat up and does not heat the monitor.
    Since there is no PWM, no frequency blinks.
    Analog (manual) brightness adjustment
    There is no limit to the minimum brightness (for those who want to work at night)

  Disadvantages :

    The white balance moves slightly to the green tone (but not much)
    At low brightness (very low), variations in the parameters will show LED lighting irregularities in other assemblies

Improvement options:

    White balance is adjusted in monitor settings and in almost all video card settings.
    You may want to insert another LED that does not noticeably drop the white balance
    To avoid uneven LEDs at low luminance, you can use: a) PWM (always use nominal voltage to adjust brightness using PWM) or b) connect all LEDs in series and supply power with an adjustable current source. (If all 180 LEDs are connected in series, 630V 20mA), the same current must pass through all the LEDs, each LED has its own voltage, and the brightness is adjusted by changing the current rather than the voltage.
    If you want to create a PWM circuit for the LM2576, you can use a NAND circuit on the On / Off input of this step-down controller (similar to the LM2941 circuit), but it is better to place the dimmer in the gap of the negative LED wire through the logic level MOSFET

Hi All repair LG 32LB582V malfunctioning led TV today "no back light." According to the owner, the TV worked in the evening and in the morning you could make the sound of the program, but there is no image.


Disassembly and defect detection.

To disassemble the TV, you need to loosen the two legs of the stand and loosen the bolts along the outline of the TV. After that, the back cover should be easily removed, if this does not happen, the bolt is hidden somewhere else.

After removing the cover, three boards with a power supply on the left are located on the right side of the main board at the bottom center of the T-con board.

TV set

Since there is no backlight, turn on the TV immediately and measure the voltage from the backlight connector

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