My 12 year old microwave quit heating today. I was warming some soup and
set it for the required time. When the cycle ended, the soup was warm,
but not hot. I ran the MW another minute and the soup did not get any
warmer. I tried yet another minute. It never got hot. The MW runs,
the timer works the platter rotates, but it just dont heat. I noticed
that it makes a loud hum, much louder than it did before.

I suspect that the heating element burned out, and probably costs more
for the parts to repair it, than to buy a new MW. But I thought I'd ask
if there could be something else that failed?

Is it normal to make a loud hum when they fail?