Common fault repair of multimeter AC voltage file
The principle of voltage measurement is the same as that of DC voltage measurement, both of which use the principle of voltage division, indicating that there are more rectification parts than the DC voltage measurement circuit. If the AC voltage fails, most of the rectifier diodes are damaged. The application selects a diode replacement with similar performance to the original diode. If the positive and negative resistance value of the selected rectifier diode is very different from the original tube, it may affect the accuracy of the AC voltage value of the multimeter.
So, how can we know the forward and reverse resistance value of the burned-out rectifier diode? this is very simple. Generally speaking, the AC rectifier circuit of the multimeter is a full bridge composed of four rectifier diodes. When the full bridge fails, usually only one or two rectifier diodes are burned, not all four. As long as the forward and reverse resistance values of the undamaged diodes are measured, the forward and reverse resistance values of the burned-out rectifier diodes are also known.
