[TenTec] Model 234 Speech Proc: Help- Passband problem

[Barrett M. Thompson]

I have a model 234 Speech Processor in use with my OMNI-D.  The processor
seems to work fine (increases average power on the wattmeter) however while
listening to the OMNI-D/Processor combination in a second receiver, I
realized that the Passband control has no effect on the audio
characteristics.  Microphone is non-amplified D-104.

According to the 234 manual, the Passband control sets bias to a varactor
diode which acts to shift the BFO frequency slightly.  I checked this bias
voltage and it ranges from approx. 0.2 - 7.5v over the full excursion of the
Passband control, so now I suspect the Varactor diode itself.  Should I be
looking elsewhere?  Any special tests required to confirm a varactor diode
is behaving correctly?

Many thanks,

Barrett Thompson / KE4R
Fayetteville, GA
KE4R@arrl.net