Open the lid and the power supply fuse has blown black , indicating that the machine current overload . Check the power input and high voltage output circuit no short-circuit fault , replace the power fuse test machine properly, but the next day the fault recurs . The investigation power fuse has blown. According to the user to reflect , for the first time after the machine repaired cooking can work , open the door when finished to be heated , the machine has a flash of light , the future can not be used. According to the circuit diagram analysis, completed after heating timer switch S4 is turned off, it can not happen in the short circuit fault circuit S4 after the first joint sales may occur in the door switch S1 and S3 door monitoring switch part . Under normal circumstances, when you open the door S1 should be disconnected, and then monitor the switch S3 is closed again . Repeatedly and check the door switches S1 and S3 interlocking actions were normal , the measured power input also found no short circuit. Replace the fuse , try a glass of water into the heated one minute after opening the door no failure , but heat 6 to 7 minutes after opening the door burst off the instant they occur fuse failure . By inference , S1 fever after working a long time deformation , although when you open the door switch in the door interlock mechanism is operated properly. But the contacts adhesions may occur , resulting in the closure S1 S3 still disconnected , causing a short circuit 220V power . After replacing the S1 test machine a long time, the fault no longer occurs .VHjservice manual download site