So...my question for those of you that have R-390As or know them well,
when I tune "through" a CW signal, should I hear a nice DC note all
the way through or should it warble and show some distortion.

I had an identical problem with another boatanchor receivers.

In my case the problem was with one of the anti-backlash gears driving the VFO.
The spring was not in tension enough.

73

Tony I0JX