[dataway]

The AM radio I just got to work again did the same thing for a few minutes. Fiddled with the volume control and the tone control and started getting some actual sound. This was not mounted in a car so how the antenna was orientated also helped a lot.

After the crackling lessened I started hearing actual radio static, then I knew it was actually receiving something and it was making it to the speaker ... then a bit of fiddling with the antenna and it brought in a few stations.

Try giving the volume and tone pots a workout and see if it gets any better.

[Engine-Ear]

Actuating the brass wiper arms on the potentiometers WILL help, since you're displacing the build up of dust and nicotine a little at a time.