This failure , the CPU can be determined essentially normal operating conditions , the fault should be associated with the startup circuit :SVgservice manual download site

( 1 ) Start button is bad, can not be +5 v power input of the CPU ( 14 ) feet. CPU can not perform the cooking process ; multimeter Rxl block measuring start button ends when the start button is pressed , the resistance should be 0Ω normal, or damaged.SVgservice manual download site

( 2 ) resistors R40, R55 short-circuit breakdown .SVgservice manual download site

If a good start button , press this button, measured with a multimeter ( 14 ) pin voltage should be +5 v; such as ov, and then measure the resistance value of R40 off , if lOOkΩ as normal, if 0Ω is shorted , the CPU internal circuit is not switched on , ( 1 ) a ( 3 ) there is no output pin low (<0.5V), the relay can not pull the fan wheel does not turn , the microwave does not heat . R55 also caused a short circuit if the same fault . Replace the same resistance available .SVgservice manual download site

( 3 ) The second door interlock switch S2 is bad , ablation is not energized , so that the base of Q3 circuit unreasonable. Q3 is not turned on ( 13 ) +5 v pin not high, so that the CPU can not detect the open or closed state of the door . Therefore, the key is invalid , microwave does not work.SVgservice manual download site