Posted 28 November 2010 - 01:05 PM
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.