Sharp R-1510 Start Button Not Working
This may not solve your problem, but on my Sharp R315J microwave, the little plastic pin that pushes forward on the inside of the start button, had broken off and it wouldn't start. The Minute Plus button would start the microwave, so I knew the microwave worked, so I tried to find a piece of plastic that I could glue into the start button hole, because the part doesn't exist and you have to buy the whole door for $100 plus shipping. Nothing I could find was small enough, so I started looking for a new microwave.
While ouside doing lawn work I noticed a small bird tail feather and the end looked to be the perfect size. I snipped off the pointed end and then up about 3/8" to make a little rod to replace the plastic one that broke. It fit perfectly!!! I didn't even have to glue the inside end, it stays put even after repeated door opens. This is sturdy material and looks to last a long time. When it wears out, I have a cat, there's always a few feathers around. I hope this saves someone else a hundred bucks, like it did me.