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Sharp Microwave Oven R-520KS

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I had a recent problem electric arcs and sparking with my Sharp Microwave Oven, Model number R-520KS. I've owned this oven since 2005, and I've enjoyed its easy features and quick cooking. Recently while just trying boil some water in a ceramic, non-metalic cup, the oven started sparking and I could see electrical sparks showing right through a metal plate on the right side of the inside of the oven. I later found out this plate is called a waveguide cover. All the literature says don't touch it. So here I am with a broken fire hazard facing tossing it to buy another one, so what do I do? I decide to take it apart, starting with the waveguide cover. I unplugged the oven. I didn't have any manual to help, but I noticed the plate was held in place with two metal flange tabs. I thought maybe I pry these flanges open to release the plate. I couldn't get a screwdriver behind the tabs to pry them up, so I tried a razor blade, and to my surprise, the "metal plate" flexed when I was prying at the tab. Working on just the cover I was able to free the waveguide cover quite easily. This is when I find out it is not metal, but appear to be paper-like and silvered. When looking it up on line I find the part is made of Mica and runs about $17 or $18 dollars, plus shipping. (Some outlets sell the raw material and you cut it to size. Probably with an exacto knife and the old one as a guide.) Examining the plate I see where the scorch marks are from the electrical arcing. I see a bit of gunk on the inside surface of the plate. So I scrub off the gunk with a plastic sink scour pad, and actually cleaned the inside very well. I note that where the gunk was a small hole is now, near the top of the cover. I tried to get the waveguide cover back on, but it is not as flexible as it appears and I accidently bend it. It doesn't break, but a crease appears, I smoothed the crease out, and finally got the cover back under the flange tabs. I positioned the cover under the tabs up to the top so the metal edge of the opening actually covers the hole. I plugged it back in, placed my ceramic, non-metallic cup of water in and turned it on. Success. Hot water. This appears to me to be a design flaw, since it doesn't just happen to me, I've looked on the internet and many others have had a similar problem with their Sharp microwave ovens. This same part is used in a number of other Sharp Microwave ovens. I asked Sharp to address the design flaw, but just received what appeared to be, an automated response, asking me to call them by phone. I believe their automation couldn't figure out an answer to give me, from the context of my message.

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It's not a design flaw. It's a user not cleaning the splatter build-up away from around wave guide cover.

You don't want to be abusive with it but a gentle cleaning, (especially around the edges where splatter can accumulate), will keep the wave guide mica cover from burning up.

What actually happens is the old food splatter keeps cooking and eventually turns to carbon which attracts the microwaves creating excessive heat in the area and then finally burning thru the mica shield.

You shouldn't have to bend the shield at all to remove or install. Some have a screw at one end which when removed will let the cover slide out from under the tabs. Some just have a raised metal lip in the oven cavity that the cover slides over when engaging into the tabs then snaps past raised lip which holds it in place.

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