[MrFixr55]

Is it possible that the 1st IF currently installed is not designed for 460KHz?  Is the existing 1st IF xformer trimmer tuned, slug tuned or neither?  Maybe hook up the sig generator to the convertor tube and adjust the freq of the sig gen till you peak an output on the secondary of the 1st IF xformer.  Maybe lead dress may be an issue.  ensure thet the wire to the grid cap for the IF tube is not running too close to then IF can or tube shield (if used. )Also, how good is the IF tube.  If the sig gen is not attenuated, you could be blasting through a bad tube.  Also check the wiring and parts in the AVC circuit. an open may cause grid rectification and low gain.

Good luck