[TMC] GPR-90 vs GPR-90RXD BFO Question

[John Poulton]

I've been working on a GPR-90RXD off and on for the
last couple of months, and am just now getting near
the end of the electrical work.  One last problem:
the BFO injection is there, but very weak.  Tube voltages
(DC) on the BFO tube differ from the ones in the manual, 
but don't appear to be so far off as to cause worry.  

But, when comparing the '90RXD to the '90, I noticed that
the BFO injection is entirely different.  In the RXD,
the BFO voltage is taken from the plate of the 6AG5 (which
is loaded with an RF choke), then capacitively coupled 
to the tap of a tapped coil operating as a step-up 
autotransformer, and finally coupled from the output of
the coil to the AM detector plate through 3 pF.  I measure
about 12 Vpp at the plate of the BFO and about 7.5Vpp
at the detector plate, after all of the tapped-coil
and coupling-capacitor shenanigans.  There's also an external
BFO input that drives the tap of the tapped coil.

In the plain '90, however, the BFO plate circuit is 
resistively loaded, and the BFO voltage is extracted from
the cathode of the BFO and applied to the grid of the last
IF through 15 pF.

So:  does anyone know why the two receivers differ in
design?  Is there any reason to think than TMC *intended*
for the BFO injection on the '90RXD to be weak?  Anyone
have a working '90RXD who can report whether the BFO
is working correctly?  If so, would you be willing to
measure the AC voltage at the BFO input jack on the back
of the radio, with a scope?

I'll be able to read email only sporadically over the
next two weeks..

Thanks and 73, John K4OZY