First of all…an older unit, this should be a simple fix. There are two coils one for AM one for FM. I have seen this problem many times. The first, is to turn the unit over. There should be a cover to remove, and expose all of the soldering area. Chances are you do not know where to find the coil (coils), may have three or five pins. Don’t worry about this for now. Have a hobbiest solder any and all broken grounds. A broken ground is when you see cracked rings around any pins or tiny posts protruding from the electronic board. Solder all power transistors, heat sinks and large ICs. This is called shot gunning. You will undoubtedly resolder the coil. Chances are good AM will return. One must note as well…..if your fuse or fuses are good in this unit, chances of fixing are very good! Thanks for asking, Matt of Martins TV Repair.