1, check the equipment
The LCD advertising machine to open the back cover, with a multimeter about the drive board power amplifier is powered and normal? If the power amplifier is normal, the next step to check the speaker cable is not normal?
2, replacement parts
If the LCD driver engine board amplifier is not normal, then replace the driver board; if the speaker is not normal then replace the speaker. In addition, the general LCD advertising machine speaker cable if the connection is not strong, then the most easy to fall off. If you fall off, then it will be welded with a soldering iron, if the speaker noise is great, that is, advertising machine driver board damage, immediately replace the driver board.