Skyworth LCD TV 37L28RM light is not on boot maintenance examples (with picture drawings) - appliance repair - Huaqiang electronic network

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Today, I was working on a Skyworth 37L28RM LCD TV that wouldn't turn on properly. The green indicator light was on, but the TV didn't respond at all. The standby button didn't change its state, and after checking the power board, the 5V, 12V, and 24V outputs were normal, which meant the motherboard was receiving the correct power-on signal. However, the main chip's 1.8V voltage wasn't being output, and other voltages like 1.25V, 1.8V, and 3.3V were also missing. The 5V voltage is generated by U28 (a DC-DC converter), and when I checked it, the output was only around 1V—clearly abnormal. After testing the circuit, I couldn’t find any obvious issues. To quickly determine the problem, I used an external 5V power supply to test the circuit. When I applied the 5V, the backlight turned on for a few seconds, confirming that the rest of the motherboard was functioning correctly. This indicated that the issue was in the 5V power supply circuit. I then focused on checking the U28 power supply circuit. I found that the voltage on pin 1 was very low, only a few volts. Since this pin is controlled by an external resistor and capacitor, I suspected the capacitor C381 might be faulty. Upon testing, I confirmed that the capacitor was leaking. After replacing it, the 5V voltage returned to normal, and the TV worked as expected.








Skyworth 32L28RM (8G20 model) LCD motherboard schematic.pdf

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