Moribund Microwave Oven

by admin on December 6, 2017

Way back when, before wife and kids, after college, 1985 to be exact I bought a microwave oven. It was a Sharp model with a rotating carousel. The carousel was rather unique, and most ovens didn’t have one. You were required to stop cooking and rotate the food periodically to ensure even heating. The carousels rotation helped to minimize that. It was a 600 watt model and it served me well for several years and then my family for many years. We got rid of it after twelve years because of low or changing power. Some times it seemed to cook with it’s usual gusto other times it was downright anemic.

It was Replaced by a Panasonic Turbo Inverter.
An unusual thing was that it would sometimes change rotation directions. Not always and not consistently. Believe it must had a “synchronous” motor I’ve seen that before, but doubt they would put such a motor in a microwave. I mean, why??

Just after two years, a switch went bad and it would no longer turn on. I opened it up to find not 1, not 2, but 3?! switches wired in series with the door. It wasn’t like there was one switch for the top of the door and one for the bottom or different physical locations. They were all fairly close to each other and in the same relative area. After figuring out which swtich was bad, I found out that the one I needed to replace was the $28 one. The other two were more reasonably priced at $5. I decided two was more than enough and jumpered around the broken one rather than paying $28 for a replacement switch. Everyone in the household was instructed to not use the door switch to turn off the microwave. Stop it from the control panel then open the door. That lasted about another year.

Died on 3/23/2011. arcing sounds heard and the burning phenolic odor was prolific. Came home and tested it ran about 12 seconds and then made a couple of snap crackles and then shut off. Disassembly revealed plenty of burned up stench though I couldn’t see anything obvious other than several connections that had been severely overheated. (blackened plastic and oozing pools of goo)

Wife went out and bought a new one, a Sharp carousel. This one is rated at 1100Watts (IEC) and the first check by me was 952 watts. (12oz water from 59F to boiling in 2 min 10 seconds)
I’ll try that again with a styrofoam cup as it is lower mass.

Disassembly was sad as the “inverter” meant there was no big transformer for all my “someday” High voltage experiments.

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