First, we attempted to repair it. My husband is an electrical engineer who designs circuit boards for a living. So, we have a strong advantage here. As soon as the machine began giving us a failure signal he attempted to de-bug the problem. This involved removing the screws and the outside enclosure. Once inside he discovered schematic drawings. This machine was built to be repaired, not just tossed. Unfortunately, no problem (a.k.a. short) could not be found. Stumped, he put it back together and brought it back to the kitchen.
There it sits, unplugged except for when we need to use it. You see, it still works. We just can't leave it plugged in. If we do, it will start beeping after about 2 minutes. And the clock no longer works. But, it gets the job done.
Knowing it needs to be replaced, I've begun gathering data. We know we want a machine that has at least 1000 watts of power; this one has 1500 watts. Target had "college" versions on sale but they were either 700 watt for $49 or 900 watt for $69. I wasn't impressed by the power or price. So, on my next trip to a thrift store I'll be scouting the aisles for a "new" microwave. Until then, we'll plug ours in when needed.