1. Adjust the volume of the volume potentiometer to the lowest level, that is, there is no sound (no sound source environment). At this time, the horn speaker should have no sound. If there is a humming sound, it is the change and failure of the capacity of the electrolytic capacitor in the filter circuit of the power rectification department of the power amplifier. Or the capacity is too small, the filter capacitor should be replaced and increased; if the volume of the PA amplifier is turned up, there is a humming sound, which is caused by poor contact or open circuit of the audio input shielding end of the amplifier, and the audio input should be checked and removed. Shield fault.
2. The campus broadcast microphone is too close to the speaker, resulting in echo sound. The volume of the monitor speaker should be reduced.
3. The shell of each original must be grounded, especially the audio input line must be shielded, and the outer wire must be prepared and grounded well.
4. There is a hissing sound from the campus broadcasting speakers. In this environment, most of them are caused by poor overall shielding, or the primary and secondary windings of the power transformer are not well isolated, and the isolation layer should be grounded.
5. Turning the power plug in the campus broadcast can reduce the "hissing" sound. If it still does not work, connect two 4700P capacitors with a working voltage of 250V in series at the power input end (the power input end of the transformer), and the center tap is grounded, which can also be alleviated.
6. The individual components have virtual welding, which is easy to cause a slight vibration to cause noise. You can use chopsticks to gently tap each original one by one to check and remove.
