![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
I received a repair request for a Songpu assembly machine 32-inch LED LCD TV. The user mentioned that there was no picture, the test machine was silent, the screen wasn’t bright, but it booted up normally. He also asked why there was no sound. I suspected the issue might be with the video signal. After unpacking and testing, I noticed that when the power was turned on, the voltage at the LED light interface rose to about 50V, but the screen remained dim. It seemed like the LED lamp beads were damaged and had triggered a protection mechanism. Using an LED test tool, I found that the lamp beads weren’t lighting up, so I concluded that one or more of them were broken. I informed the user that we would need to replace the lamp beads, though I wasn’t entirely sure if it would be worth the effort or if he would even pay for it. I advised him to order the parts, which would take around three days. After the repair, the screen turned orange, black, and brown, and there was some damage during installation, but the user agreed to leave the phone and left after the repair. After lunch, I started disassembling the screen. I had previously replaced the lamps in two 22-inch Samsung LCD monitors, so I had some experience. This was my first time working on a TV screen. I carefully removed the screws, opened the front cover, and took out the screen and other components, wrapping them in plastic to prevent dust. I examined the light strips, each containing 10 LEDs, and there were three strips in total, connected as 10x3. When I opened the lamp bead cover, I was shocked to see how small the LEDs were. They were patched, and I didn’t know how to solder them. I couldn’t even find a way to fix them. I used the LED test tool to check each light bar and found three damaged beads, one in each strip. Since I didn’t know how to solder, I looked up the model online, but there was no matching part available. I then searched for similar sizes on Taobao (TB) and found two options: 3528 and 2835. I couldn’t tell the difference between them, only that one was imported and the other domestic. However, I didn’t know the wattage of the original beads. After thinking for a while, I decided to order 2835 0.2W LED beads. The delivery came quickly. Next, I searched for videos on how to patch LED beads, but found very few useful resources. Most of the videos showed LEDs with protruding legs, which wasn’t helpful. I had to give up and look for someone else to help. Today, I received the goods and felt excited—technology always needs a breakthrough. I removed the old beads, tinned the joints, placed the new ones, and tried to solder them. The first attempt failed, but after several tries, I finally managed to get the light working. The second and third attempts were successful, and I was happy to see the light come on. I tested the board again and it worked, but when I turned it off, the lamp burned out again. I tried replacing it three times, but it still didn’t work. Was it the lamp? Or did the welding cause damage? I had no choice but to short-circuit the faulty lights. I used the LED test tool again, and all the lights were fully lit. I tested the circuit board and everything was fine. I reassembled the screen and connected it to the test machine, but the brightness didn’t seem to affect the image. I realized that the user might have been pressing random buttons to get sound, but it had no real effect. I think the AV input was not properly connected. My language is not very good, so I apologize. Here are a few questions I’d like to ask: 1. When the first welding was successful, the lamp interface voltage was 33V. According to the formula I found online, VF = 3.2V, so 10 x 3.2 = 32V. Is 33V normal? 2. What impact do the three discarded lamp beads have (not referring to the board or the beads themselves)? 3. When the three beads were removed, the interface voltage was 29V. According to the formula, 9 x 3.2 = 28.8V. Is 29V normal? If anyone has experience with this kind of repair, I’d love to hear your thoughts. A video demonstration of the soldering process would be great too.
Jiangsu D-Bees Smart Home Co., Ltd. , https://www.cI-hometheater.com