According to the fault analysis of phenomena, mostly 220V electricity does not enter the microwave or low-voltage power circuit control board has failed. Detection fuse and thermostat ST FU were normal , high-voltage transformer T1 primary pull connectors at both ends XT1 and XT2, power input AC 220V between ① terminal 1 and terminal board through ⑤ side ( see above Figure ) , low-voltage transformer T2 through two low-voltage power conversion to ( see below ) , a group through a rectifier VD1 ~ VD4 bridge rectifier , the C8, C9, R8, L1 consisting of high and low frequency filtering. +12 DC power supply output relay K1 ~ K4 and buzzer circuit power supply. The other group VD5 ~ VD8 rectifier bridge rectifier , the C4, C5, + IC3 (7806), C6, VD9, C7 composed of high- voltage and low-pass filtering the output +5.3 V for a microprocessor IC1 (HD4074054), anti- phase drive integrated circuit IC2 (2003), show the power supply circuit and other circuits . Detecting a first set of +12 V DC power supply is normal. DC power supply and then detect the second group of about + lV ( normal to +5.3 V), measure the DC voltage IC3 ① feet about +10 V, description regulator circuit problem. Power, check the C6, VD9, C7 were normal , thus causing damage to the internal circuit judge IC3 said fault . Replace the IC3 (7806) , the power test machine , it lost excluded.w5fservice manual download site