I have a transformer labeled F 78 D on the bottom. It has a center tapped primary and a center tapped secondary. Both sets of windings have a couple hundred ohms resistance making me think its a modulation transformer or an interstage driver transformer. There is no manufacturer label on it and I don't know if someone painted it and covered up the manufacturer name. I googled it but could not find anything on it. Does anybody Have any data for this/ Sincerely Steve, N1BUS.