During the repair of a Toshiba LCD TV model 32AV550C, the user reported that the speaker produced a harsh self-excitation sound with low volume. Initially, I tried using a signal injection method and replaced the power amplifier IC R2A15112 with R2A15213. After this replacement, the sound became louder at 12.25 volts, but the self-excited noise was still present. Further investigation led me to check the audio processing block. I noticed that the input and output capacitors were not functioning properly, so I replaced them with 1µF electrolytic capacitors. This helped reduce the self-excitation sound significantly.
However, the issue wasn't fully resolved until I replaced the 1-pin capacitor with a 10µF capacitor. Once this change was made, the self-excited noise disappeared completely, and the TV functioned normally again. This case highlights how even small components like capacitors can have a major impact on the performance of an electronic device. It's always important to carefully test and replace capacitors when dealing with audio-related issues in TVs or other electronics.
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