Original post by: David Iwanicki ,
If the unit is no longer heating food, then the cavity magnetron has gone bad. Probably not worth trying to get it fixed, as you should be able to get a 1000w or better oven for less the a repair shop would charge to fix this one. 700w is really pretty low power anymore. Fixing it yourself would be somewhat dangerous, due to the voltages required to generate the microwave energy - failing to make a connection and energizing the unit could cause a short or fire. Were there any lightning storms around the time the microwave failed?