I was working on a Changhong LCD TV model LED50C2000 that had a "three no" fault—no power, no picture, and no sound. After performing a teardown test, the primary voltage on the power board was normal, but there was no 12V output on the secondary side. When I unplugged the motherboard's 12V connector, the power board started providing normal 12V. This indicated that the motherboard was causing a short to ground on the 12V line.
Further investigation confirmed that the 12V line was shorted to ground. I disconnected the 12V power supply and replaced the 4803A component with a known good one for testing.
After replacing it, there was still no sound, which made me think it might be an issue with the audio module. However, the sound was very weak and not directly connected to the input port. It was likely due to a faulty audio block, so I decided to remove it.
Re-soldering the original audio block was a bit tricky, but I managed to fix it. At the C827 position, I installed a 0.1 microfarad capacitor, and the test machine worked normally again. The TPA3110 chip still delivered strong performance, proving that sometimes simple fixes can make a big difference.
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