The fuse inside a Sharp microwave is a very small and inexpensive part that is critical to the operation of the microwave. When the fuse goes bad, the operation of the entire microwave is halted. The fuse could blow from something as simple as slamming the microwave door shut. Because microwaves contain a transformer that can discharge lethal amounts of electricity, even when unplugged, you should read all safety information in your owner's manual before you try to change the fuse.
Unplug the microwave and move it to a table or other location where you can access both the front and the back.
Remove the back cover. Unscrew the screws and lift off the cover. If the screws are not Phillips, you may need a Torx Security bit which can be purchased from most hardware stores. Look for the fuse. It should be a small white or clear bar with metal caps on each end, located near where the electrical cord enters the microwave.
Replace the back cover and remove the control panel if you could not locate the fuse in the back of the microwave. To remove the control panel, unscrew and remove the exhaust vent or pull off the top bar of the microwave. Unscrew the single screw holding the control panel and gently pull it up and away from the microwave. Mark all connectors to the control panel (so you do not confuse them when you reassemble it) and gently pull off the connectors. Find the fuse.
Remove the fuse. For best results, purchase a new fuse that is the same as the old fuse.
Reassemble the microwave.