Noblex TV 21tc678f
Where does it start to distort? Before or after coupling capacitors? Does the sound come out the same as before, that is, bass?
Are you testing it with a test amplifier? Because from the input to the integrated there are only the capacitors and the R1307 and 1308 of 100K to ground. Sometimes they bring a zener after the capacitor to ground. I don't know on your TV.
It would be good if you used an amplifier, perhaps that of an AM radio, as a dynamic analyzer, (that is, you unmask the detected audio input that goes to the end of the volume potentiometer, and to this end you weld a capacitor of 1 mf. of polyester, and at the other end of said capacitor you weld a probe). You connect the mass of the Radio to the mass of the TV and with the probe you check.
Go ahead! ... Start from the entrance to the integrated and so you will realize where it begins to distort. Don't forget to give me a like if it helped you. regards