[Joeztech]

I have seen cases where the internal bobbin that holds the primary and secondary windings was loose enough that they would vibrate. Various techniques can be used to solve this. One of the easiest I saw was to shove a piece of a flat wooden toothpick into the area where there was an air gap visible. Some have used lacquer to stabilize vibrating windings. If there is an insulating gap material between leaves of the transformer that has deteriorated and fallen away that would be another possible area of vibration. I suitable piece of fish paper or other insulating material that can stand high temperatures would be the solution there. You might be able to use some Teflon tape for that situation.

Joe