[MrFixr55]

OOps, started the above post and had to leave before sending. The fact that you received at least one AM station means that you are getting close. Dittos on David's comments on the 12AT7. Emissions tests essentially test the tube as a rectifier. Consider replacing the tube. Also make sure that it is a 12AT7 and not a 12AU7. 12AT7, 12AU7 and 12AX7s al have the same pinouts but only the 12AT7 was designed to operate ate VHF frequencies. The 12AT7 was a somewhat early (but not the earliest) tube for oscillator / mixer or RF amp stages in early post-war TV sets. Consider replacing the 12BA6 and 12AU6s. You can borrow a 12BA6 from any 1960s AA5 set. The 12AU6s are a little harder to find in the average hobbyist workshop unless they have this, a Zenith or RCA tabletop AM FM set of this vintage. However, these tubes are available NOS (New, Old Stock) rather cheap and used rather cheaper.

Consider making voltage measurements, particularly for the plate and cathode.

The other step is rather dangerous, and that is adjusting the trimmer caps (little screws) on the AM Oscillator and RF sections of the tuning cap. Dangerous as adjustment usually calls for a signal generator and VTVM. Again, caution, as you are working on a HOT CHASSIS set. The AM sections have many more plates than the FM sections. Mark or photograph the positions prior to attempting adjustment.