[SignalOne] Question re alignment of 30.1mhz mixer in cx7a/b

[David Bertman]

Hi Folks --

      I have been chasing an issue with alignment of the mixer
that produce output from pto's and 34.2 mhz osc.

      The problem is getting sufficient output at the if board
test point (specified as 600 mv).  I can get that number with pto a
and the OFFSET 34.2 mhz osc, but not with either pto and the
"normal" 34.2 osc.  The level adjust is c20, c71 for this purpose.

      I have already aligned both mixer bandpasses with a
sweep generator.  I am looking at output with pto's set at midrange
(500 khz) as per directions.

      The best I can get is about 380 mv for pto A, 200 mv for
pto B.  Checking pto's, I notice that the pto B output is less by
about the proportionate amount.  I have othe pto's, and testing these
and all possible bias tweaks it looks like my pto B output is probably
in range, so I should forget about pto tweaking and look elswhere.

      The bias control used for "dual" pto activation seems ok,
yielding simiar (low) output for pto A and B selection via the pot
to control mix of pto's.  So the mixers seem to be working ok, or at
least the same.  I have not yet checked voltage levels to the mixers,
and will do so tonight.

      I am thinking now that the 34.2 mhz osc output is low and
that is the problem.

      But I thought, what the heck:  might as well ask these people
with all the knowhow what they think b4 continuing on.

      Does anyone have a comment on this area?

      Thanks much

      73,  Dave/AB7B