故障现象:无伴音。出现此类故障时,首先检查扬声器或耳机是否有问题,若耳机有问题,则检查耳机功放电路LM833(见图1)是否有问题;若扬声器有问题,则更换扬声器。若以上均正常,则检查30V供电电压是否有问题。若30V供电电压有问题,则检查电源板30V供电回路是否有问题;若30V供电电压正常,则检 Symptoms: no sound. When such a fault occurs, first check the speaker or earphone for any problem. If there is a problem with the earphone, check the earphone amplifier circuit LM833 (see Figure 1) for any problems; if there is a problem with the speaker, replace the speaker. If the above are normal, then check the 30V supply voltage is there any problem. If there is a problem with the 30V supply voltage, check if there is a problem with the 30V power supply circuit of the power supply board. If the 30V supply voltage is normal,