The afternoon before yesterday, two people brought up a Changhong TV to repair, the model is as shown below. When the power is turned on, the panel indicates that the red light is on. After pressing the power button, the indicator light flashes several times and then shuts down! Aluminum Electrolytic Capacitors/ Ceramic Capacitors Aluminum Electrolytic Capacitors/ Ceramic Capacitors Aluminum Electrolytic Capacitors,Electrolytic capacitor,Ceramic Capacitor YANGZHOU POSITIONING TECH CO., LTD. , https://www.pst-thyristor.com
It is estimated that the Y board burned out. First, the price was raised: the green black and brown were repaired, and the customer promised to leave the phone and left. Remove the back cover and measure the VS voltage to 0V. Then remove the Y board after power off, connect the upper bulb to the VS and the ground at the power board, power on the test machine, the light bulb is lit, the indicator light on the logic board is also lit, and the TV startup screen is heard. Sound, indicating that the power board is normal, the Y board or the sustain board may be broken.
Measure the resistance between VS and ground on the sustaining board, there is no short circuit phenomenon; then measure the removed Y board, the resistance between VS terminal and ground is 0 ohm, which means that the Y board is indeed short-circuited!
The Y board, also known as the scan driver board. The function is to convert the scan control signal sent by the logic board to the scan buffer board after being converted by the FET (Field Effect Transistor) to generate a scan drive waveform. The buffer board receives the driving signal of the scanning board, and sequentially supplies the scanning waveform to the scanning electrode of the panel through the IC on the buffer board. And divided into two upper and lower buffer boards.
If the scanning board is damaged, all black screens will usually appear, or the black screen in the upper half and the black screen in the lower half; there will be a flower screen (the image is disorderly) and so on. And burn the upper and lower scan buffer board!
Knowing this principle, it is not sloppy to repair the Y board. First look at each small Ceramic Capacitor on the Y board and find a C419:331/1KV burned a hole! Replace it with 471/2KV. Continue to measure the FET, this check does not matter, catch a lot!
First check the VS plug side, Q412: FGPF4536 small tube; Q410: RJP30E2 large tube full short circuit burned out. Also check the other side of the scanning board, (on the side of the buffer board) Q409: SMK1360; Q407, Q408: FGPF4536; quick recovery tube D416: 20F40HF is basically reimbursed! After measuring other components, no signs of burnout were found.
Through the TB network, I bought the original accessories, and installed them one by one today. I wanted to power on the test machine, but my heart was uneasy. A little mistake, the components that have been replaced can be sacrificed! I want to think about it, I am afraid I have to test it!
Immediately press the power button, hear the sound of the TV startup screen, erect the TV and look at the screen, shocked: white screen! How to do it? Is there any place that has not been found? Put down the TV and take a closer look: God, it turned out that the plug wire to the site driver board was not plugged in! A false alarm!
Immediately power off, connect the plug to the location driver board, and then power on, this time see the normal screen for a long time. On the signal line, the picture is normal.
Ok, so much, maybe look at the picture above:
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