I've hooked up an antenna and AM is still really bad. I can tune in a few stations, but they are very garbled and noisy.
Since the AM/FM circuits share so many parts there isn't much to check.
First, I checked the tubes. The 19T8 combo FM descriminator, AM detector and audio amp was weak so I replaced it.
No change.
Moving on the the other tubes I was surprised to discover a 12BA6 in the place of a 6BH6! That's the limiter and since FM is working fine it must be a valid substitute.
I popped in a 6BH6 and there was no noticeable difference. I suppose a 12 volt filament tube might be good to keep in there to compensate for higher AC outlet voltages
Next, I checked the two AM IF cans and their associated resistors and caps. They all check out including the IF windings. All measure around 15 ohms as indicated on the schematic.
Then, I tried a little aligning by ear but got no improvement. That leads me to suspect bad mica caps inside the IF cans. I popped the shield off one and discovered they are riveted to the bottom.
Retrochad repaired IF transforms just like this in a recent YouTube so I have a good idea what's involved. Only one problem - the values are not marked on the schematic or caps
I do have a part # at least M76J433-1 188. Does anyone know what those caps values might be ? Is suppose I could determine them experimentally if it came to that.
