Radio dial moves, but AM station does not change

[DirtFarmer]

Hello, newbie here. I am enjoying my "new" 1961 Magnavox FM-47 "Grand Classic" radio, and it has been working great. But now suddenly I cannot change the AM stations. The dial marker moves left and right just fine, but it stays on the same station no matter how far I move the dial. FM works just fine.

Can someone tell me what may be causing this? Is it an easy fix for a newbie? Honestly, the only thing I am capable of doing inside of this thing is change tubes. Would it be as simple as a bad tube?

Thanks in advance.