Fan turntable motor coil short , high voltage transformer primary winding short circuit , high voltage breakdown microwave system components , power transformers burnt varistor RV1 and breakdown can cause this failure. Disconnect the power , measured with a multimeter R xl0k block no short circuit coil fan motor , turntable motor coil is also about 6kΩ resistance , high voltage transformer primary winding resistance measurements around 2Ω, the secondary winding resistance is lOOΩ ~ 150Ω,. In case of power failure , the measurement of microwave system circuit . With RxlOOk block measuring Vl, positive resistance is 150kΩ, the reverse is infinite, normal ; then measure the resistance between the two pins C is 9MΩ,, for housing without leakage, the magnetron is not damaged , you can exclude the microwave heating circuit failure. Plug and unplug all computers connected to the control panel , to provide computer control panel AC220V power alone , with a multimeter to measure voltage block +12 V, +5 v voltage across both 0V,应属power short circuit . Measuring the power fuse (0.5A), has been blown, then load sensitive resistors RV1 both ends of the resistor value of about 2Ω, close to 0Ω. And the surface has black carbon points , indicating that the breakdown has been shorted . Replace the varistor and insurance , troubleshooting.Ae3service manual download site