Common failure of the power amplifier of professional audio: the failure of the whole machine does not work is that the amplifier is powered on without any display, each function keys are invalid, and without any sound, like when it is not powered on. 

The power supply circuit should be checked first during maintenance. A multimeter can be used to measure the DC resistance values at both ends of the power plug (the power switch should be switched on), and should normally have hundreds of ohms of resistance values. If the measured resistance value is much smaller, and the power transformer is seriously heated, it means that the primary circuit of the power transformer has a local short circuit; If the measured resistance value is infinite, check whether the fuse is fused, whether the transformer primary winding is open, and whether between the power supply line and the plug. 

Some machines have added a temperature protection device, in the primary circuit of the power transformer connected with a current fuse (usually installed in the power transformer, the insulation paper outside the transformer can be seen), it after damage will also make the power transformer primary circuit open. If the resistance value of both ends of the power plug is normal, measure whether the output voltage of the power supply circuit is normal. For an amplifier using a system control microprocessor or a logic control circuit, mainly check whether the power supply voltage (usually +5V) of the control circuit is normal. If there is no +5V voltage, measure whether the input voltage of the integrated circuit 7805 is normal. If the input voltage is abnormal, the rectification and filter circuit should be checked. If the 7805 input end voltage is normal, and the output end has no +5V voltage or low voltage, the load can be disconnected to see whether the +5V end voltage can return to normal. If the +5V voltage is normal, the fault is in the load circuit; if the +5V voltage is still abnormal, the fault is in the 7805 itself. If the +5V power supply voltage of the system control circuit is normal, check whether the clock and reset signal of the microprocessor are normal, and whether the keyying and display drive circuit is damaged. 

Guangdong Wanchang Technology Industrial Co., Ltd. has 18 years of industry experience and perfect service system, from product consulting, engineering design, guidance and debugging, user training, maintenance, system upgrading and other links to form a professional service mode. Its independent brand JSL Jazz Dragon Sound has won the top ten professional sound expansion system (national) brands for 14 consecutive years. In the future, it will continue to focus on quality and innovation, inherit and carry forward the brand concept of "listen to the good voice, gather positive energy", and strive to create infinite space in the sound world.