Don't make it simple to complicate - Home Appliances

One-piece inductor

I was called to repair a Konka 32-inch LCD TV. The model is forgotten, but the issue is clear: there's sound, the remote works, but the screen is dark and only faintly visible in a dark room. The user had previously taken it to after-sales service, but the problem returned within two days. He was frustrated and cut off contact with the service team. When he brought it back, I tested it on the bench and found it working fine—so he wasn't lying. After a quick pulse check, I suspected the backlight voltage was too low. The next step was to discuss the cost with the user, which I'll skip for now. Then I opened the chassis and saw that this TV uses a three-in-one board. Here’s a picture of the board: Powering it on, since the issue was related to brightness, I measured the main voltage and skipped the smaller ones. The results were as follows: This 97V is from the backlight boost circuit, which is normal. But when I rechecked the voltage after boosting (the actual backlight LED power supply), it was only 105V—way below the normal range of 135–150V depending on the model. Here’s the image: Even though there was 105V, the backlight circuit seemed to be working, so I turned the board over and noticed something strange. It was the legendary protection circuit. I decided to restore the original look first. After powering on again, the backlight voltage was still 105V. I then tested the filter capacitor in the backlight power supply (22UF/250V). In the forward direction, it showed a fixed resistance of about 7K, and in reverse, it didn’t charge or discharge. Everything looked good. I removed the 22UF/250V capacitor and replaced it with a new one. Here’s the result: After replacing the capacitor, I powered it on again. The result was promising: Finally, the last image shows the completed repair: Great success! If this case was simple, the next one might be more complex. I’ll take time to organize and share the details soon.