1. The audio circuit is disconnected or the frequency divider is abnormal. After the audio line is disconnected, the speaker unit does not have excitation voltage, which will cause a silent fault. The voltage divider is generally not easy to disconnect, but the lead joint may be soldered off, and the capacitor of the voltage divider may be short circuited.

2. The voice coil is broken. Using a multimeter R × 1. Measure the solder pad of the speaker lead. If the resistance is ∞, use a small knife to scrape off the sealing paint on the leads at both ends of the voice coil, expose the bare copper wire, and then re measure. If it still does not work, it indicates that the internal wire of the voice coil is disconnected; If the measurement is open and there is a "click" sound, it indicates that the voice coil wire is open. Weld the wire head and then weld it to another section of enameled wire near the voice coil winding.

3. The speaker wire of the professional audio equipment is broken. Due to frequent vibration of the speaker paper pot, the braided wire is easily broken, and sometimes the wire has already broken, but the cotton core wire still remains connected. This type of braided wire is not easy to buy and can be replaced with longer flexible wires.

4. The voice coil is burnt out. If the resistance of the speaker lead is close to 0 Ω and there is no "click" sound, it indicates that the voice coil is burnt out. Before replacing the voice coil, first remove the impurities in the magnetic gap, then carefully put the new voice coil into the magnetic gap, straighten the voice coil, and use super glue to fix the voice coil up and down while listening. After the voice coil is in place, fill the gap between the voice coil and the paper basin with glue, and apply super glue to about half of it, then seal the dust cover, put the speaker paper basin on it, and it can be used normally one day later.