Marinus Loewensteijn wrote:
I am looking for some input into solving a (potential) problem that I
have with my Omni-C.
history: I obtained this transceiver some months ago and it had been
sitting in a box for 28 years. Cosmetically immaculate but needed to
have all the 100 nF bypass capacitors replaced since these were all
cracked.
And I thought I was the only one having that problem. <grin>
I cannot find instructions for adjusting the TX mixer - what is in
the circuit diagram in the manual uses a ring mixer in a IC package
and what I have is a discrete diode ring mixer with two adjustable
potentiometers.
Similarly the SSB exiter has an adjustable coil and I cannot find
details on adjustment of that either.
My problem is that after the rebuild the audio is distorted. I wonder
if this is due to some fault in the microphone or in the SSB exiter /
TX mixer. CW works like a charm and output is fine too. Even when
transmitting on CW the current nicely increases / decreases with the
modulation, only it is garbled.
I do use this rig mainly on CW so it is not a problem but I do like
to fix this part. Where do I start?
I'm not an expert on this rig, so let me give a generic answer.
How about putting the rig on a dummy load, then setting the power for
about 10 watts out with a test tone connected to the mic input and then
using an oscilloscope stage by stage to see where the distortion enters.
Hopefully, others will have some info on how to adjust the 'mystery stages'.
Good luck,
Carter K8VT
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