[Hallicrafters] SX-71 Help

[Bill Pancake]

I am hoping some of you who are very familiar with the SX-71 will be willing
to help get me overcome a troubleshooting problem.

The receiver appears to work OK when the "reception control" is in the NBFM
position. Volume is good and clear. No distortion. Station selectivity is OK
but not great.

In the NORMAL IF position the volume drops off significantly to where you
can bearly hear it in the speaker even with the volume control at maximum.
Same low volume problem in the BROAD CRYSTAL and SHARP CRYSTAL position.

I've checked for loose or broken wires & components, cleaned the wafer
switch contacts, tested all tubes for emission and mutual conductance. Even
replaced each tube with a known good tube... no change.

I've had good luck in the past with signal tracing to isolate a defective
stage. With this receiver, in the NBFM position, the signal trace is
successful from antenna to speaker. In the NORMAL IF position, the very,
very low volume (regardless of the actual position of the volume control)
remains low throughout each stage.

I'm lost... Would appreciate any suggestions as to where to start.  Thanks
in advance.
Bill  K0JWP