Hi Jim, I don't know about the 24V furnace transformer, sincce I got that second hand.
I had a local noise problem here in the house that I traced to mu door bell transformer with a transistor radio. I disconnected the primary it and the noise went away. No problem with the new transformer. I suspect some kind of internal arcing possibly due to a partially open winding, but the thing would still ring the bell. Possibly there was a similar problem in that furnace tranny. I guess the moral of this story is that if you have strange noises creeping into your receiver, don't rule anything out. 73, John, W4AWM
