ER2801 multimedia active speaker speakers "hum" sound repair this fault caused: one is the power supply rectifier and filter capacitors C20 and C21 decreasing capacity or failure; the second is TDA2030A internal amplifier circuit short circuit leakage; the third is left and right channel audio input connector or plug shield open, caused by external electromagnetic interference. Maintenance check from the outside to the inside, first disable the input connection plug, if the "humming" sound, it is the input connector or plug shield overhand; if you still have a "humming" sound, immediately shut off the power supply, check the speakers internal amplifier circuit, amplifier circuit TDA2030A short circuit internal breakdown tends to have a DC voltage into the speaker, the speaker burned to the ground.gLtservice manual download site