RST Engineering wrote:
There are two adjustment controls on the rear. The top center one is
labeled LOC and the bottom right one is labeled VOR.

In the lower left corner there is what we call a "cannon" plug, about 1.25"
diameter and with 14 male pins inside the plug housing.

That what you've got?

Yup.

Now, as I said, this one was working 20 years ago when I took it out to
replace it with the RST navcom(s). If it is DOA when you get it, start
thinking that perhaps it is the radio that drives the heads rather than the
heads themselves. What radio is driving the head?

The TKM is driving the VOR head. And your diagnosis is right on the mark.
I'll be out at the airport tomorrow to check on the radio nav itself.
It may be bad connections/wiring. The instrument shop (yes, I broke down
and took the VOR head over there today) claims that the narcos are
practically bullet proof, and the odds are 90% in my favor that if the
radio works, there's probably bad wiring or connectors.

If the radio is good, and this one doesn't work, I'll look around for the
other head.

Wait until I see what's happening with the one I've got here.

tanks!