The investigation leads between the magnetron filament and the shell has been shorted. After pry open the shell at the filament, fixed plastic pin has found carbonized filament lead short to ground. Shave the part of carbonization, the metal filament pin fixed to pry away the shell of about 10mm, and then between the metal casing painted with color TV repair high pressure cap 704 silicone insulation and fixed, to be silicone dry, replace the shell, try machine, everything is normal.gVPservice manual download site