[amptramp]

Nostalgiaair shows a different schematic.  I assume this one uses the capacitance between the parallel plates of the dual diode to couple IF into the second plate.  The schematic from the link above has the disadvantage of still back-biasing the detector.  I was using this:

http://www.nostalgiaair.org/pagesbymodel...013329.pdf

What circuit do you actually have?