I baked a potato in the microwave this way once. I had meant to press
5:55 but had pressed 55:55 instead, then I got engrossed in something
and just forgot about it until I smelled something funny, went running
into the kitchen and saw flames shooting out of the microwave.

Funny thing is, while I never got all the burn marks out, the microwave
has been going fine since - and it's been 6 years. It's been doing much
better on a low-carb diet; potatoes spike my microwave.

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http://www.ornery-geeks.org/consulting/