I have a Sharp Carousel Microwave , Model R-8350. Serial 01091. Recently I set the cooking time on a small pizza for 10 minutes when it should have been 1.5 minutes. The pizza burned in the oven I have cleaned the entire oven, and in doing so found am oblong piece of cardboard like paper with a shine, perhaps 3" x 6" at the top right hand side of the nside oven top. The material on the cardboard had bubbled. I removed this cover and wonder how to get a new one. I have no idea if it is a waveguide cover, but in my manual there appears to be an arrow in a diagram pointing to it as such. The Microwave appears to work well, but I am uncomfortable with replacing this cover with the damage done to it. Considerable smoke damage occurred in the kitchen but the Microwave seems to be unharmed except for this piece of cardboard like paper which covers something in the inside top of the unit.