I think you just turned the light on for me. I have been sweeping
through a much broader range and this is what was causing the BFO to
swing through 0hz. I have an HP606a and am monitoring with a 5245L, so
I can move in small increments. I will watch much closer and try more
subtle movements. I also will give the AVC a try, as that would
eliminate any audio frequency related swing in output level from the
equation.

I did try a sweep last night and it worked very well on normal IF
setting... a beautiful textbook curve. With the crystal filter engaged
(it has two settings, broad and sharp) and the phasing set at zero it
just about wipes out the signal. You can get it back in by turning the
phasing, but then I got the oscillation type of ringing that you
mentioned would likely happen with a 60hz sweep. Thus, I could not get
a clean curve with the filter on using the sweep. I was going to
trying better connections tonight, but perhaps it is inherent in the
crystal.

There is conflicting information in my 3 sources (Sams, the manual,
and a tech bulletin on alignment) that I am still unclear about: The
tech bulletin mentions to set the phasing control to have the plates
1/2 meshed during this procedure and to reset the knob so that this
becomes zero. The other sources don't even mention where to set the
phasing at all... yet it has a big impact. So should the filter put
the null in the center of what the IF is passing or off to one side
(my gut says to one side, but I have no reference)? Where would "zero"
on the knob normally be in relation to all this?

Using this radio has been a lot of fun. I figured out how to use the
BFO to bring in SSB transmissions, and of course it is great for CW.
The phasing and BFO combined with some strange signals out there can
create some incredible 50s science fiction sound effects... I guess I
am easily entertained. After aligning the am is working the best I
have ever heard, and I am getting commercial broadcasts from literally
all over. I might be getting the HAM bug.

Dan