It should be determined first whether the noise comes from the front stage or the back stage circuit. The signal connection plugs of the front and rear stages can be removed. If the noise significantly decreases, it indicates that the fault is in the front stage circuit;

When the machine has no output or when the output volume is high or low

After prolonged use of the machine, dust and usage environment can cause oxidation of the volume adjustment potentiometer,

Cooling fan slow or stalled

Whether the heat dissipation fan of the power amplifier is working properly plays a crucial role in ensuring the operation of the machine. So when the fan speed is slow or not running, the power amplifier should not continue to be used,