I've repaired and tuned many tubed radios, but not a transistorized tuner.
(It's the only schematic I could find. It's kinda hard to read. Hit the magnifier to slightly blow it up)
I have good AM, but no FM. Using a oscope, I have very little into IC1 (on the FM IF strip). I have:
0.1 volts out of IC1 and into the 1st filter and about 0.05 out.
0.25 volts out of IC2 and into the 2nd filter and about 0.12 out.
0.6 volts out of IC3 and through C11 to IC4, but out of C11 the modulation looks to be cut in half.
1.5 volts out of IC4 and into the discriminator/detector transformer, but with very little modulation.
0.1 volts of audio out of the detector diodes.
Ed posted a link to David Eaton's schematic of a AF-6.
http://www.davidreaton.com/Dynaco_AF6.htm