[Greg]

Adding a bit to what Rod said -

I'd probably first check to see if the oscillator is doing its thing when on BC. To check the oscillator, I usually put another radio (on BC) nearby to "listen" for the oscillator as I tune the radio under test across the band.

If it's not oscillating, I'd check the band switch (dirty?), BC oscillator coil bad...

I suppose it could be something before that, like the antenna transformer/related band switch... But I might expect a tiny bit of signal to find its way to the mixer.