The Skyworth LCD TV model 46E60HR belongs to the 8R80 series. During testing, the backlight turned on, but there was no sound and a gray screen appeared during boot-up. There were no characters or logo displayed on the screen. Initially, it was suspected to be an issue with the display panel or the logic board. After opening the cover and measuring the voltage, it was found that the logic board had no 12V supply. The resistance between 12V and ground was normal, and the fuse resistor wasn’t blown.
By tracing the LVDS cable, the power supply chip U2 (5800-H8K800-0000) for the screen on the motherboard was located. However, the output from the 12V input was 0V. At first, it seemed like the problem was due to a faulty power supply chip. But after checking the short-circuit between the input and output of U2, the screen remained dark, which made things more confusing. It turned out that the issue wasn't just about the screen power supply.
After some careful thinking, the power supply for the LVDS large chip was checked, and no voltage was detected. This gave a new direction. Then, the LDO-U6 chip was tested, and it also showed no input or output voltage. Without a schematic diagram, the circuit was traced back to the DC-DC switching power supply chip U1, which was identified as P3482. According to the data sheet, it's an 8-pin DC switching power supply chip. Pin 2 is the 12V input, and pin 3 provides 3.3V at 3A for the LDO and other components. Pin 7 is the EN pin connected directly to 12V high level. It was clear that U1 was definitely damaged.
Since there was no P3482 chip available, a similar replacement was used—FR9888—with comparable functions and parameters. After replacing it, the output of U1 was restored to 3.3V. The screen power supply chip U2 then provided 11.88V to the logic board. Finally, the long-awaited Skyworth logo appeared on the screen, confirming that the repair was successful.
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