【Panasonic Microwave Oven】Operates with a low sound, Midea microwave oven after-sales service telephone in Beijing, does not heat.
Beijing Panasonic microwave oven repair phone - published on August 20, 2011.
【Warm Reminder】The relay on the computer control board of the microwave oven usually has four welding pins. The two pins in parallel with the diode are the two ends of the coil. The other two pins are the fusing point switch pins. The two terminals of the relay coil, the terminal connected to the positive electrode of the diode is the drive end (directly or through a resistor below 100Ω to the transistor); the terminal connected to the negative electrode of the diode is the power end. The transistor connected to the relay coil is the drive transistor, its B terminal is directly or through a resistor connected to the microwave control foot of the CPU. After the microwave starts, the BE junction voltage should be 0.6V~0.7V. Using the above logical relationship, all computer-type microwave oven computer control boards can be easily repaired without blueprints.
【Fault Symptoms】Microwave oven operates with a low sound, does not heat.
【Cause of Fault】Leakage between the collector and base of the transistor on the computer control board.
【Analysis and Maintenance】When the microwave oven works, except for the sound generated by the TT synchronous motor driving the tray and the FM fan motor driving the fan blades, the high-voltage transformer and the components on the right side that make up the microwave system will produce a relatively loud sound. After opening the shell of the microwave oven, the fan runs, and the measured voltage between the primary ends of the high-voltage transformer is 0V (AC), which should normally be the same as the grid voltage, i.e., about 220V (AC). Upon inspection, it was found that the large-volume power relay switch on the computer control board was open. The DC voltage between the two ends of the power relay coil was measured to be 0V, which should normally be above 8V. Upon checking the coil and the transistor connected to it, it was found that there was leakage in the BE junction of the transistor. After replacing the transistor, the fault was eliminated.