Who thought a 60 year old radio would open such a can of worms... S curves, IF pass bands, etc.
On further reflection one thing the receiver is doing seems a little odd to me.
When the signal of the sweep frequency generator is applied to the grid of V4, the output of the discriminator transformer looks decent - when it is applied to the grid of V3, it is the same, but with more gain... when it is applied to the grid of the mixer half of V1, the signal is not much stronger than when it is applied to V3, as though there`s not much gain in that stage. I actually opened up the FM-A IF transformer, and inside the capacitors are ceramic disks, so no GE `silver mica disease` to deal with here. The IFT also tests fine for continuity, and the 17EW8 tests good. Is the mixer supposed to amplify the signal significantly, or is it normal operation what I have noticed - I wish I had a voltage chart to accompany this set, to make sure the 17EW8 is biased properly.
I found the following book, and am working my way through it, it is a good help in understanding how the receiver is supposed to function, but the description of converters is dated and doesn`t reflect how my radio is set up.
https://ia700402.us.archive.org/5/it...nReception.pdf