I have a Sharp micro wave model R-1492. It turns on, but nothing cooks. Do you think I may need to replace the magnatron

Sounds like the inverter (power supply for cooking) or the magnatron which does the work----neither are cheap parts.

1st check the temperature fuse ( item 1-3 on this diagram)
If fuse is good have the HV rectifier item 1-1 checked.
If both check out good the most likely problem after that is the magnatron item # 1-8

http://www.searspartsdirect.com/partsdirect/part-model/Sharp-Parts/Microwave-Parts/Model-R1491/0958/0123370/P0101308/00001?blt=06&prst=0&shdMod=R-1491

Either the power board to supply the magnatron or the magnatron is defective.
Check or have someonr check the output of power supply. If ther is a hi reading, then change magnatron

Replace the HV capacitor

With micro waves, this could be a number of things. They are hard to diagnose using this forum but I'll try. There are three things you can check. One being the thermal fuse. On some models, when it goes bad it put some things out. with others it puts every thing out.
if it's good, check the mag tube (Magnatron). Most of the time, it will be burned on the end if it's bad. tube. The last thing would be the fuse. It is made of ceramic and is a 20amp. It looks like a old round car fuse but it's not. It's made just for micro waves. Honestly, if the thermal fuse and the round 20 amp fuse is not the problem, you may be able to replace the micro wave cheaper than replacing the parts.
Thermal fuse $28.99.
Round 20amp fuse $1.53
Transformer $100.00.
Mag tube $87.00
Capacitor $45.00
Go to www.appliancepartspro.com and enter your model number. This will pull up every part in the micro wave and their prices. Then you will ba able to decide if you want to replace the parts. With yours being one that's built-in over the stove. These cost more and are worth putting more into. If I can help any more comment back and I'll do what I can.
Please rate solution

open the door and look on the middle top right inside the microwave is it burned or blackend?You have a faulty magnatron.if it is.

this sounds like either a capacitor, transformer, or magnatron. Mags unually don't go bad. Either one can go bad and blow a fuse or other safety device. If one shorts, it could burn a section of the circuit board.

I would think about calling a tech and have him diagnose the problem. Tell him you can't fix it now but will in a month or two. Have him write down the things you need so when you do want it fixed, you do not have to start all over again. Then order the parts and fix yourself.

Micro waves can be dangerous and cause burns, so if you think this is not for you, go buy a new one.

You probably have a burnt wave guide cover. Look inside the microwave either on the side or on the top, it's a square piece of mica board, and you should see a burnt spot on it. You should be able to replace it fairly easy with the model number I can check on a replacement for you.

This is almost certainly a blown high voltage diode.

Please reply back with your brand and model number so we can help you.

the buzzing is the magnatron tube juicing too thousands of volts before emmitting the micro-wave radiation to what your cooking that turns molecules 180 degrees around... guess that friction is what really heats it.
radar ovens is what they use to call em and even people would stand in front of big ones to warm up long ago...lol canibles will love that.