[Ron Ramirez]

Quick answer: No, the tuning knob will not have any effect on tuning when any of the preset AM buttons are depressed. You must push in the third button from the right, which should be labeled "B.C." (broadcast) to utilize manual tuning.

Now, if you have the B.C. button pushed in and it is not tuning across the band, then you definitely have a problem...I can't say that I've ever run into an issue like that before.