Kenmore microwave oven model 665 4438955 just

I am not familiar with this particular model, however there are a few things you could check. Do you get any lights or indications at all? Inside (unplug before removing cover) there is probably a fuse. If it is blown, you can replace it as it might have been blown by a power surge, however you should check to see if there is another bad component, especially if it blows a second time. There is generally a transformer, a capacitor and a diode in the power supply, and a magnetron that does the real work. If anything is burned or blackened, this may be your problem, or it could merely be an indication of another shorted component. Using a multimeter, you can check the magnetron. Measuring between the two terminals, you should see very low resistance. This is the filament. From either pin to ground you should see infinite resistance. Anything less and your magnetron is bad. The diode should measure relatively low in one direction and infinite or close to it in the other. The capacitor should start low and build to infinite (as it charges). Most people should just replace the fuse, if bad, and let a technician find any other problem. My built in was worth ordering a new magnetron. Some of the cheaper counter top units might not be worth fooling with. I hope this has helped you.