I think it's better to leave the actual fixing of your microwave's electronics to professionals, otherwise you risk being struck by electricity, because even unplugged oven stores thousands of volts of electricity in its capacitor, which can be a pretty painful bite. I have a Egyptian friend, who's got hit a pretty nearly by electricity while trying to fix a microwave. He should have known there are are
Microwave Maintenance Centers who can fix a microwave and pretty much anything else in the blink of an eye.
What you yourself can do is clean the of your microwave's inner chamber on a minimum of weekly basis.
Many pieces of food and splatters partly absorb the microwave energy which instead should work on cooking your food, and not burn the walls of your oven. If you search for a new microwave, I suggest you try stainless steel interior, it will be easier to clean. Use microfiber cloth for best results.
ميكرويف شارب R212
مكرويف اولمبيك 42 لتر موديل رقم KOR-167H
