I am a complete idiot. Yesterday I was out all day and came back very tired, so I reached into the fridge for a plate of leftovers and shoved them in the microwave, then rushed to the loo. When I came out I smelled a sort of burning and found to my horror that my dinner was in a metal bowl and I hadn't noticed (shows what a state I was in!). There was arcing going on all over the microwave. I switched it off and hoped for the best but today when I turned it on (using a conventional plastic plate), there was still arcing and the funny smell. Looking it up online I think I may have damaged the magnetron through a combination of factors - the metal bowl which reflects the waves back at the magnetron, and no water in the bowl to absorb the waves. Any ideas/experience before I have to take it in to the repairers?