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Good evening, this means the microwave is overheating from the high voltage transformer or the magnetron. Neither of which are available any longer. I hate giving people bad news I'm sorry. Even if the parts were still available it would cost more to repair this than replace it. most people opt to replace the microwave. the average price for just the high voltage transformer is around $165.00 or sometimes a lot more. New microwaves have come down so much you could replace this for $150.00 - $200.00. hope this info helps, thanks , Bryan.