This is a common problem that bears a bit of insight.
The symptoms are: You get a few stations at the right spots on the dial
(or sometimes no stations at the right spots), and you weakly get a few
strong local stations that tune in very broadly (30 to 100KC wide each).
What's happening: The local oscillator is dead, either all over the
dial, or just over one part of the dial. On the spots of the band where
the oscillator is working, you tune in stations normally.
Where the oscillator dies, the converter tube (12SA7, 12BE6) loses its
grid bias and it is now biased on a non-linear operating point. This
lets it act as a (poor) diode and/or plate detector. You now have a
poor crystal set, with only the RF tuned circuit for selectivity.
Somehow the audio gets passed on, perhaps modulating the weak background
So when you see these symptoms: very weak reception, signals tuning very
broadly, look for a dead oscillator. This is often caused by a weak
converter tube, or corroded oscillator coil, or a oscillator grid
resistor that has drifted way up in value.