Konka color TV lightning fault repair example - Appliances

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Due to time constraints, I skipped the power supply section repair, which included components like the fuse, FET, and A06. After fixing the power supply, the TV had a grating but showed a black band about 5 cm wide on the left side. There were characters displayed, the buttons worked normally, and no image appeared when video signal was added. However, the grating slightly shrank towards the right, and a black line moved from bottom to top. I removed the speaker during the process but didn't check for sound. The black band on the left made me suspect the line pulse circuit. I checked the high-voltage package at pin 10 (AFC) of the 44th pin on the 76931 chip and found nothing wrong. Since it was struck by lightning, the memory chip was the first to be affected. After several attempts, the data issue remained unchanged, so I concluded that the main chip was faulty. I ordered three replacement chips online. After a few days, the chips arrived. I soldered the socket, inserted the new chip, and the TV had a grating, but the field was only about 10 cm wide, not linear. The lines looked normal, and when I added the video signal, an image appeared—but the new chip was defective. Trying all three chips resulted in the same problem. It's unlikely all three chips failed. Could I have damaged them during installation? Reinserting the original chip restored the previous fault: the field was normal, but there was still a black band on the left. I couldn’t figure out the issue for a while, checked the pulse circuit and power supply again, but found nothing. I had no choice but to place the TV aside. Fortunately, the chips weren’t too expensive, so I ordered three more. This time, the TV returned to its original state—same grating, with a black band on the left, and the field was normal. I was completely stuck. Could it be that seven chips were bad? The amplitude of the three chips wasn’t normal, but the four blocks also didn’t work properly. The code word was too slow, and it was already 3 AM. I decided to call it a day and write down what I found: this TV was caused by two capacitors, C404 and C408, being struck by lightning. When I replaced C404 but not C408, the first three chips worked mostly fine, but the image was shaky. With the second batch of four chips, there was no image, but the display was otherwise normal except for a 3 cm black band on the left. After replacing C408, all seven chips worked correctly. Not replacing C404 had little effect on the image. The 76813 chip had no pulse at the 44th pin, and the fault resembled Figure 1, but there were no characters. I tested it on two P21SA387 units. I bought the first chip model 76931 H7L57L2E online. The second one, 76931 7L57L2-E, was suspected to be faulty at the time. Because C404 and C408 failed, their symptoms were different. After repairing the TV, I tried the 76931 7L55N7-E chip.