[pic][pic][size=5][color=Red] Skyworth Cool TV, when the user pulls the image to full screen, the image flickers up and down, like an old TV with poor synchronization.
I opened the power board on the side and checked the small signal voltage on the digital board, which was basically normal. This is my usual habit when repairing TVs—no matter what the issue is, I always measure the key points. However, I couldn't find any problem there. Then I measured the logic board voltage and noticed that it was fluctuating along with the screen. It looked like there was an issue with the logic board. So, I decided to remove the upper right screen cable for testing. After doing so, the right side of the screen turned black, but the left side still flickered. I reconnected the left cable and pulled it out again. The screen showed a faint blue color with visible vertical lines, but I hadn’t measured the VGH voltage yet. When both upper screen cables were disconnected, there was no VGH voltage. I thought maybe the logic board was faulty. I had previously repaired a 40-inch LCD in the store, and I tried removing the upper screen cable again. The measurement still showed 15 volts. All signs pointed to a faulty logic board.
I ordered a new logic board and after a few days, installed it for testing. Suddenly, I felt a chill—there was still a sound, but the screen was frozen. Was it hanging? But it didn’t feel quite right. I carefully measured the logic board voltage again. Except for the 12-volt power supply, there was no stable voltage on the board. When I removed the upper screen cable, the logic board had almost no voltage at all. That was strange. According to measurements from another logic board, the board should have had at least a stable 15-volt signal for the screen. Even though the boards weren’t exactly the same, they should have functioned similarly. It seemed this TV was really problematic, and I decided to give up.
It’s hard not to feel frustrated after such a long repair. I kept thinking about this TV. I started to believe it wasn’t just the screen itself. As I reviewed the entire repair process, a bold idea popped into my mind: Could the logic board be directly generating VGL and VGH voltages? I unplugged the two flexible cables on the screen, and the main chip on the logic board had no basic power. Based on my assumption, there should be a chip on the screen that works with the logic board. The principle should be that the motherboard sends 12 volts through the logic board to power the circuit on the screen. Once the chip is working, it outputs the voltage back to the logic board to power its own components. Then, it can generate various voltages and send them to the screen.
My idea was clear. I decided to remove the screen and carefully take off the outer casing and bezel. I saw a chip-centered circuit on the left board. After testing, I found that the chip directly generated VGL and VGH voltages, but they were fluctuating. The diodes and capacitors didn’t show obvious damage. I suspected the chip was faulty. Then I remembered that I hadn’t checked the upper screen cable. I removed the copper foil at the connector and found a circular pit in the middle caused by the pressure of the bayonet. The adjacent copper foils were not properly connected. I trimmed the two flat-wire heads by 2 mm with scissors and reinstalled them. The fault was resolved.
After the repair, the logic board had a stable 15-volt output, and the second step of the screen boosted it to 25 volts. This confirmed that my theory was correct—the logic board chip was controlled by the on-screen chip.
ELCB is an acronym for Earth leakage circuit breaker, which is a device placed inside a water heater, commonly referred to as ELCB electric leakage breaker. This circuit breaker has the function of disconnecting the device from the circuit whenever an electrical leak occurs through the human body when touching the electrical parts of the device.
ELCB is to limit the incident of electric shock inside the machine, disconnecting the power when there is a problem, ensuring safety for human life as well as fire and explosion prevention.
How many types of ELCB?
ELCB is often used in both civil and industrial applications.
For the domestic electricity system, the installation problem is not difficult, but in industry, the anti-shock for workers and the prevention of electrical leakage for electrical equipment with large capacity requires a bridge. Automatic anti-shock, high-power leakage protection, and often has a much higher price.
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