How Does a Microwave Work?

I was sitting with a neighbor one summer afternoon around 1989, when the neighbor asked, “Dan, do you know how a microwave works?”

I told him that I did, and asked him if he’d like me to explain it. He assented. So I considered how to explain how they work to someone with little math. And then launched into what probably was a dizzying description with hand gestures of quantum and molecular degrees of freedom, electromagnetic resonances, and a brief detour into the evolution of and differences between magnetron and Klystron tubes before finally mentioning the history of radar and the serendipitous development of the Radarange. (Now that we have the web, you can find a fit-for-non-geeks  explanation, for example, here.)

When I stopped for air, he said, “That’s all very interesting.  But I asked because I have a dead microwave that I’m throwing out, and wondered if you wanted it to take and fix it.”

Oops. My socially defective self forgets that what people ask is often only obliquely related to the question they mean to imply. When he asked if I knew how one worked, he meant, Did I know how the works fit together, how to fix one?

I told him that I’d give it a try. I had never owned a microwave, but a good rule of thumb on electric gadgets is that total failure implies simple repair. Usually an open circuit or bad switch.

So I went with him and carried it home. I was hopeful because it was a simple older model with no membrane buttons, digital display, nor processor control. Just a mechanical timer and button. I took it apart, and figured out that one of the three safety interlocks — that make sure it won’t run with an open door — was worn out. I bypassed it, leaving only two.

Occasionally one of the remaining safeties blows an internal fuse when someone tries to open the door while it is running. Then I just take it apart and replace the fuse.

This Object at Hand gets daily use, twenty-odd years since it was saved from the landfill. I may yet get another twenty years out of it.

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