This is our microwave. I was aking Ginny today how long we have had it. Well, we got it in December 1982. So we got to talking about it for a while. Then it started making a different noise. Ginny said the fan wasn't working properly. So I hauled it out ot he hangar for some maintenance. I could find nothing wrong with it. The fan was working just fine and it heated stuff just fine. It is now back in the kitchen, still sounding a bit different, but also still heating stuff up.
John, I tried to donate our microwave of the same vintage to a thrift store when we moved a few years ago. It worked fine but we had no need of it in the house we were moving to. Was politely told they had no need of such old technology.