TV model: Haier L32R1B LCD TV
[attach]494741[/attach][attach]494741[/attach]
Symptom: Everything is normal after booting. After working for a period of time (10-20 minutes), the screen starts to appear interference lines, and more and more, the image cannot be seen at the end, and the sound is always normal.
Overhaul process: Disassemble the rear casing of the TV, access the video signal, test the machine to wait for the fault to appear, and measure the voltage of each group of the main board and the power board. Everything is normal. No capacitance pregnancy is found. The voltages are stable. It seems that there is only static fault. Appeared, 1 hour... 2 hours... Half a day... One day passed, the fault did not appear, the TV has been normal, strange, and puzzling.
No way, I have to install the back shell, and then send it to the customer tomorrow. After I installed it, I wanted to try TV again. I used the signal to watch TV while I was busy with other activities. After ten minutes, strange things happened. There was another interference line on the TV screen. It was the same as the original fault. what happened.
Think carefully before and after the fault, it is just the back cover of the TV and the cover. The rest is the same. If it has a relationship with the back shell, there is only one possibility. After the cover is closed, the internal heat dissipation is affected. Some components have poor thermal stability, immediately disassemble the back shell test machine, everything is normal, use the heat gun to warm the various components of the motherboard, the fault does not appear, the motherboard has no problem, only the logic board, the LCD screen and logic board of this TV is Integral, the logic board is hidden in the top frame of the screen. Only a small gap can see the logic board. The heat gun is used to warm the logic board from the gap. Only 10 seconds of trouble occurs, and the heart is overjoyed, and the faulty part is locked. Only the screen is removed.
Open the screen frame, expose the logic board, power on the test machine again, use the soldering iron to heat the parts, determine the fault point. When the main chip AUO11401 is heated, the fault occurs quickly, and the faulty parts are found, but the heart is mixed. The faulty component, the worry is that this chip is surrounded by 100 pins, the pin spacing is very dense, there is no such a chip, but do not want to give up such learning opportunities, everything has the first time, made up their minds Immediately online shopping for 3 chips, the price is not expensive, in the days of waiting for parts, on the Internet to find out how to replace this chip, learned the drag welding technology, using the used circuit board in the hands of many exercises, found Some tips, another buy a bottle of high-concentration alcohol, used to clean the circuit board, also made a small bottle of rosin alcohol solution, also bought a magnifying glass, used to observe the quality of welding, everything is available, only the parts.
After the part arrives, first confirm that the part model is correct. Since the AUO11401 has two versions, it cannot be interchanged. The model is correct. After following the knowledge learned on the Internet, the chip is blown off with a heat gun. After cleaning the pad, the soldering iron and the heat gun combination are used for the soldering. And carefully observe the phenomenon of no pin adhesion.
With the excitement of the power test machine, the gray screen appeared, measuring the voltage, only the VGH voltage is not normal, the VGH voltage of the observation circuit is controlled by the main chip, it seems that the main chip is damaged when soldering, it does not matter, also There are 2 spare parts, continue to replace, considering that the damage may be caused by excessive soldering temperature, it is decided that the chip grounding is no longer soldered, and thermal grease is applied between the chip and the circuit board to facilitate heat dissipation, and welding is performed by drag welding. After the completion of the test machine troubleshooting, in order to reduce the temperature of the chip, a heat-dissipating aluminum plate was installed on the top of the chip, and after installing the back cover, the test machine was completed for one day without failure.
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