According to the symptom analysis, fault may be in the control circuit or microwave door interlock switch S2. Computer control panel of local circuit as shown , ICl use of computer chips TMP47C400RN-FD31, when the door is closed, the door interlock switch S2 is closed through the ground , Q3 is turned on , +5 V voltage through R8 to IC1 (13) feet to provide high level , to judge the door is closed, so that the internal switch is closed ⑩ feet , ready to start the program execution . When you press the fire button , set the time, press the start button , IC1 (14) pin output start command , so that by D11 Q13, Q14 is turned on , but also by R12 so Q6 is turned on, and then the D10, S2 to ground for Q4, Q5 ready to prepare the program execution .mrqservice manual download site
 mrqservice manual download site
When setting the microwave heating , IC1 (15) feet microwave output control signal, the R17 makes Q4 conduction, microwave relay RY3 pull, turn on low-voltage circuits , 220V mains added to T1, MAG -emitting microwaves heat food . Open the keypad housing , unplug the keypad lock key connector , remove the computer control panel , check the various components of the circuit is not abnormal , then unplug the connector S2 (S2 mounted on the right side of the cavity ) , close door , when measured with a multimeter on when S2 barrier, thereby confirming , S2 microwave control circuits caused by poor contact caused the malfunction does not work . Remove S2, pry open the cover , the two contacts with fine sandpaper black oxide , then S2 embedded back into place , plugged in line fittings, power test machine , microwave everything is normal, troubleshooting.mrqservice manual download site