Skyworth LCD TV 42E65SE (8R68) motherboard repair examples - appliance repair - Huaqiang electronic network

The customer sent a Skyworth LCD TV model 42E65SE for repair. The issue was that the green power indicator light would not turn on, and there was no display or sound when trying to power it up. After disassembling the case, we checked the power supply section. When pressing the remote's standby button repeatedly, the BL terminal always showed 0V. However, the output voltage from the power board was normal. Then we moved to the motherboard and measured several key voltages: U24/3.3V was 3.38V, U20/1.2V was 1.29V, U18/1.8V was 1.79V, and U19/5.0V was 4.98V. We also checked the main chip RTD2692D (a 296-pin chip) for power, clock, and reset signals but found nothing suspicious. Initially, we thought the problem might be with the motherboard (model 5800-A8R632-0P20) or possible virtual soldering on the RTD2692D. Then, suddenly, the backlight turned on, and the speaker produced boot music. The TV could even play programs when connected to a video source. At first, I thought this was just a temporary glitch, possibly related to the flash memory or software. But after testing multiple times, the issue returned. I decided to use an oscilloscope to check the LDO outputs on the motherboard. During the scan, I noticed a noise spike at U24, and the noise was even more significant when moving the probe to U20. After some research and analysis, I concluded that the issue was likely caused by poor-quality electrolytic capacitors. I replaced both the U24 and U20 filter capacitors—originally 100U/16V orange capacitors—with higher-quality 200U/16V blue ones. After replacement, the oscilloscope showed clean voltage outputs: U24 was 3.28V and U20 was 1.19V. I let the TV cool down for 2–3 hours and tested it again. This time, everything worked perfectly. The TV played programs without any issues, and the system ran smoothly. This repair highlights the importance of checking power supply stability, especially when dealing with intermittent faults. Sometimes, even small components like capacitors can cause major problems. I hope this case helps others facing similar issues. Orange capacitor 100U 16V 1.jpg Has changed blue 200U 16V capacitor 1.jpg QQ picture 20161010092000.png Repair the test chart 8R68.jpg

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