My home-used Aote Bluestar ADA885 stereo for many years suddenly screamed in the subwoofer. I don't know where it can be repaired in Shanghai, so I can take it to Baoshan Central Shopping Mall for repair. Hello! First, the horn is ringing. That's because the coil of the woofer is faulty or scraped the horn core obliquely. Under normal circumstances, it is not necessary to repair it. Just buy a new one and replace it (100 yuan or so), because it needs professional replacement, and the sound quality is not as good as the original one after straightening or replacement. Second, there is something wrong with the bass knob or volume knob, which causes the horn to ring. Just change it to a new one (within five yuan).