Anyone familiar with the Heathkit AJ-1600 Tuner?

Ask Van Alstine. Try VanAlstine Audio on the internet. He is competent and probably has serviced
or rebuilt these Heath models. As I recall, they were
good units, but not exceptional. (I may be misspelling
his name; so try some variations.)

I don't recall this model, but there are some things to consider. First of all, this tuner would have to be pretty old since Heathkit has been out of business for many years. There would be no source for service.

Secondly, the tuner quality depends on the skills of the assembler. These could be all over the map.

I hold a ham license and built my share of Heath gear in the late '60's and '70's. Parts quality was average at best, and product architecture sometimes suffered due to the requirement that it be buildable in the field. Many assembly techniques that work well on an automated assembly line don't translate to the consumer bedroom.

Bottom line: I'd pass. There are lots of reasonable quality tuners available at your price point.

In fact