Background
These transformers are specially designed tuned circuit in RFI-tight groundable metal packages for narrow bandwith IF application. They are called IF cans. As shown in the 1968 specification sheet of figure at right, this unit includes a 125-pF capacitor, and the arrow between primary and secondary indicates that the tuning is attained by tuning-tool (a non methallic screwdriver) adjustment of the ferrite core (slug). The purpose of the primary winding tap is to increase the effective Q of the collector circuit in the narrowband IF of the standard broadcast receiver.