Headphones sound only, other output are silent, AV switch basic normal, so doubt IC2001 or mute circuit problem. Using sound channel output test, with capacitive coupling IC2001 24, 25, 33, 34, 36, 37, has audio signal output, explain IC2001 is normal, then the key suspect noise circuit, check Q2013, Q2014 base 0.7 V conduction, plug P3 line 3, 1 foot nipple, sound output is normal, follow the check Q891, Q890, found Q891 conduction, doubt its performance is bad, remove Q890, change with removed 2 sb0709 Q891 remains silent, check the peripheral circuit, doubt C892 leakage, after replace C892, troubleshooting. No action due to C892 leakage noise circuit, cause the whole machine are silent.Zm2service manual download site