The specific reasons why Aiwa K580 combo is not turned on are as follows:
1. First, check the power supply circuit. You can use a multimeter to measure the DC resistance at both ends of the power plug and keep the power switch on. If the numerical display is normal, it is several hundred ohms; If the measured resistance is too small, it means that the power transformer is seriously heated, indicating that there is a local short circuit in the primary circuit of the power transformer; If the measured resistance is infinite, check whether the fuse is blown, whether the primary winding of the switch is open, and whether the power cord and plug are disconnected.
2. Some machines have added temperature protection devices. After the current fuse is connected to the primary circuit of power transformer, it will be damaged, resulting in the primary circuit or open circuit of power transformer.
3. If the resistance values at both ends of the power plug are normal, you can electrify to measure whether the output voltage of the power circuit is normal; For amplifiers using system control microprocessor or logic control circuit, it is important to check the power supply voltage of the control circuit, and the normal value is +5V. .
The maintenance method is as follows:
1. Disconnect the electrodes of the power amplifier tube, connect a resistor above100Ω/1w in series respectively, then disconnect the signal source and start measuring whether the neutral point output voltage to ground is less than 0.5V If the deviation is too large, continue to check the previous stage.
2. Measure the series resistance of the collector of the power amplifier tube100Ω. The voltage drop at both ends should be less than1v. If the voltage drop is too large and the static current is too large, it is necessary to continue to check the previous stage.
3. Measure the base bias of the two power amplifier tubes, which should be between 0.2 and 0.4 volts and basically symmetrical; If the deviation is too large, continue to check the previous stage as usual, and then adjust the base bias resistance of VT8.
4. Turn off the volume potentiometer of the power amplifier to the minimum, connect the signal source, monitor the voltage between the midpoint and the ground, instantly adjust the volume potentiometer to the maximum, and then reduce it instantly, and the medium voltage should be quickly reduced to 0.5 volts; If the neutral point voltage recovers slowly and is not used for a long time, it is easy to burn out the power amplifier tube, so it is very important to check the capacitance.
5. When the power supply is not connected, adjust the volume potentiometer of the power amplifier to the maximum, and repeat steps 3 and 2,1; If the voltage fluctuation is too large, it means that there is self-excitation, and check the source of self-excitation.