Fault phenomenon 4: the volume is not adjustable or adjust the volume when there is noise.

Analysis and maintenance: the volume can not be adjusted to adjust the volume of open circuit. The volume adjustment potentiometer "hot" side of the open circuit is silent, "cold" end open circuit sound is the largest and can not be adjusted. Adjust the volume when a noise for duplex potentiometer bad contact inside, off the speaker power, repeated several large angle rotation potentiometer can often will potentiometer movable contact of dirt to get rid of, improved, if there is noise, had another new potentiometer.

Fault phenomenon 5: horn "hum" hum.

Analysis and maintenance of: the fault reasons: a power rectifier filter capacitor C20, C21 capacity decreases or failure; the second is power amplifier circuit TDA2030A internal short circuit leakage; the third is the left and right channel audio input connection plug wire or shielding layer open, resulting in external electromagnetic interference. Maintenance from outside to inside are examined, disconnect the input plug connection, if the "hum" sound disappeared and is connected to the input plug wire or shield wire breakage; if there is still a "hum" sound, please immediately shut off the power, check the speaker internal power amplifier circuit, because power amplifier circuit TDA2030A internal short circuit breakdown often into DC voltage loudspeaker, loudspeaker burned.