Is 12V obtained at IC251 pin#34? NO YES Check POWER circuit.
Is 5V obtained at IC251 pin#40?
NO Is Audio signal at IC251 pin#8, 9? Check Input AV2 JACK
YES Is Audio signal output at IC251 pin#19, 20? YES Is Audio signal output at IC601 pin NO #3, 13? Comparing with switching table, are SWA, B CTL SIGNAL right at IC601 pin #9,10? YES Replace IC601. Check Output JACK. NO Check IC501. NO Are CLK and DATA obtained at IC251 pin#42,43? YES Replace IC251.