Two examples of Galanz WP700 microwave oven repairs - kitchen appliances

[Example 1] Fault phenomenon: The lighting in the furnace comes on after turning on the machine. The turntable operates fine but does not heat. Analysis and maintenance: The reason may be no microwave output due to high-voltage circuit failure or magnetron failure.

Open the casing and check and find that the high voltage fuse has blown. According to the analysis of the circuit diagram of the machine (see attached picture), the high-voltage fuse is blown, indicating that the high-voltage current is overloaded. The possible reasons are breakdown of high-voltage capacitor C, breakdown of high-voltage diode D or breakdown of magnetron. Check that the high-voltage diode is normal, and then check the high-voltage capacitor c. It is found that it has broken down. After replacing it, test the machine and eliminate the fault.

[Example 2] Fault phenomenon: The microwave oven does not work after being turned on.

Analysis and maintenance: Open the furnace cover and find that the power fuse has blown out and turned black, indicating that the current in the machine is overloaded. Check that there is no short-circuit fault at the power input terminal and high-voltage output circuit. After replacing the power fuse, the test machine is normal, and then it is handed over to the user. But the fault reoccurred the next day. After checking, the power fuse was blown again. According to users, the machine can work normally when cooking for the first time after being repaired. However, when the oven door is opened after heating is completed, a bright light flashes behind the machine and it cannot be used in the future. According to the circuit diagram analysis, the timer switch s4 has been turned off after heating is completed, so the short circuit fault cannot occur in the circuit after s4, but may occur in the first door lock pin switch s1 and the door monitoring switch S3. Under normal circumstances, when opening the furnace door, S1 should be opened first, and then the monitoring switch S3 should be closed again. Repeatedly open and close the furnace door and check that the interlocking actions of S1 and S3 are normal. No short circuit was found at the power input end. Reinstall the fuse, put in a cup of water and test heating for one minute, then opened the furnace door and no fault occurred. However, when the furnace door was opened after 6 to 7 minutes of heating, the fuse blew out again. It can be inferred that S1 lasts for a longer time. It heats up and deforms after work. When the furnace door is opened, although the door switch interlocking mechanism operates normally. However, its contacts may be adhered, so that S1 is not disconnected when S3 is closed, causing a short circuit of the 220V power supply. After replacing S1 and testing the machine for a long time, the fault no longer occurs. After using it, the user confirmed that the fault has been eliminated.