In such cases it is not suitable to use a microwave oven to avoid damage to the magnetron. Unplug the power cord, open the door, furnace chamber observed the contamination, especially mica plate waveguide port surface contamination is particularly serious, which absorb microwave energy, causing overheating and sparking. The dirt thoroughly cleaned, usually pay attention to cleaning and maintenance, sparking phenomenon can be eliminated.H9Lservice manual download site