1. The speaker wiring is broken or the crossover is abnormal. After the speaker wiring is broken, the speaker unit has no excitation voltage, which will cause a silent failure. The frequency divider is generally not easy to break, but the lead joints are de-soldered, the frequency dividing capacitor is short-circuited and other faults may occur.

2. Broken voice coil. Use the multimeter R×1 gear to measure the solder lugs of the speaker lead wires. If the resistance value is ∞, use a knife to scrape the sealing paint of the leads at both ends of the voice coil to expose the bare copper wires. Broken wire; if the measurement has been passed and there is a "click" sound, it means that the voice coil lead is broken, you can solder the wire end, and then use another piece of enameled wire similar to the voice coil winding to solder it properly.

3. Speaker lead is broken. Because the speaker cone vibrates frequently, the braided wire is easily broken, and sometimes the wire is broken, but the cotton core wire remains connected. This braided wire is not readily available and can be replaced by a slightly longer flexible wire.

4. Voice coil burned out. Use the multimeter R×1 to measure the speaker leads. If the resistance is close to 0Ω and there is no "click" sound, it means that the voice coil is burned out. Before replacing the voice coil, you should first remove the debris in the magnetic gap, then carefully place the new voice coil into the magnetic gap, straighten the voice coil, and fix the upper and lower positions of the voice coil with super glue while listening. After positioning, use super glue to fill the gap between the voice coil and the paper cone to about half, seal the dust cover after Z, and put the speaker cone up, and it can be used normally after a day.