Stop opening the lid to check. There coke smell, there is a component to determine the occurrence of a short circuit ignition. Initial investigation showed no abnormalities of the electrical components, check the magnetron hands, poke two filament terminals, measuring normal filament resistance with a multimeter R × 1 files, then R × 10k files measure the resistance of the magnetron housing small. Intuitive found a pin on the shell shorted. Remove the magnetron, the pin with a screwdriver to pry open the plastic cover, to see the phenomenon of ignition internal insulator has caused charring, scraping all filled with epoxy resin and then carbonized part of the package, after curing, replacing the magnetron, seated terminals. Ohmic heating returned to normal, the magnetron can be repaired.HeKservice manual download site