Hi,
Sorry to break the bad news, but you are better off getting a new microwave. The problem is that you need a new magnetron; this device is what excites the H2O molecules inside the food/beverage, etc. and heats the food. Magnetrons can be expensive, and the replacement procedure can be costly as well.
Oh, and did I mention that the circuitry is a shock hazard waiting to happen? I'm a consumer electronics technician, and even _I_ hate working on the things!
Jim Lee- technician, Graham's TV Service (W. Columbia, SC)
May 2004
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix microwaves.