Jim,
Hammerlunch receivers are very popular in AM circles. I run an HQ-129X at my station, and am always on the lookout for an HQ-170A or HQ-180.
I can almost guarantee you'll find someone in your area who can fix it (or give you whatever you need to fix it yourself) on amfone.net. I would try the technical forum first. Good bunch of folks with gallons of know-how.
Good luck!
Thom, KA1ZGC