'49 Admiral audio problem

[kbmuri]

With the generator's amplitude turned down, I'm clearly zero-beating the video at exactly 61.25 MHz. This makes sense to me because the TV is obviously processing the 61.25 MHz video signal perfectly, so it must be tuned there exactly. The picture is crystal clear. The zero-beat is when the generator perfectly matches the video signal -- the TV under test isn't really part of THAT experiment. We just demonstrated (again) that my frequency counter is very nicely accurate.

The fine tuning knob doesn't change the local oscillator 6 MHz, but the oscillator tuning slug A14 sure does. I was able to put the Ch3 video on channel 2 and channel 4 with it. I watched the video signal come down from the topside to Ch2, and up from the bottomside to channel 4, and all across the slug's range on channel 3. Volume at max, not one peep of audio signal. I even turned the generator's tone modulation on, set it at exactly 65.75 MHz, and tuned the slug for maximum sound. Turned the generator off, STILL no audio. The generator tone is apparently only getting thru because it's AM. Completely assuming the audio of my Rat Shack receiver is accurate, at 65.75 MHz, and present. Just doesn't get thru the system. Only difference is AM vs. FM.

I didn't see any point in messing with the coarse-tuning slugs in the tuner turret. Those are for adjusting a single channel once A14 gets most of them right, if one or two is off. The sweep of A14 ruled that out to my satisfaction.

Still stumped.