[R-390] Technical Question somewhat related to R-390s

[Barry]

I have an old radio that I'm trying to fix.  The secondary of the 1st IF won't peak like it should.  Thinking it could be caps in the can, etc., I pulled it and started testing it out of the circuit.

I connected the function generator to the primary and the scope to the secondary.  In this configuration, adjusting the primary core shows almost no effect; however, adjusting the secondary core shows a very nice resonance at the IF frequency.

If I reverse the setup, the adjusting the secondary core shows almost no effect and adjusting the primary core shows resonance at the IF frequency.

I think the transformer is fine but in the setup described above, why are there not peaks on both coils?  I expected to be able to adjust both cores and see each side resonate but that wasn't the case and since it does this in both setups (only the coil not connected to the generator peaks in each setup instead of both in the same setup) I assume it is the expected behavior but don't know why.

Is it possible the low impedence of the function generator is preventing the "primary" side from resonating?  Would coupling it differently allow both circuits to resonate in the same setup?

Thanks for listening.

Barry - N4BUQ