I am just getting to grips with a new Omni VI Plus that I have very
recently acquired. It is in almost as new condition and generally works
very well.
I decided to listen to the Omni's keying on my TS990 and found that it is
very hard and slightly clicky and also has the beginnings of a very slight
chirp. In addition, the mark/space ratio of the keying is shortened so that
I need to increase the weighting of my external keyer. The mark/space ratio
of the sidetone with the external keyer is however not shortened but with
the internal keyer both the keying and the sidetone are shortened.
I looked at the manual and decided it was time to adjust R24 on the Control
Board. I poked my screwdriver down through the bottom screening plate hole
identified as R24 but I couldn't find anything. So off came the screening
plate and indeed there is no R24.
Moreover, the board is not populated by discrete components as shown in the
manual illustrations but it is all SMD. There is stencilled on the upper
side "R24 CW Shape" with a couple of very small holes through the PCB but
nothing in them.
Anyway with an illuminated magnifying glass, I have managed to trace the
circuitry and component values around the shaping circuitry involving Q12,
Q13, Q14 and Q15. All seems OK and corresponds to the values in the manual
circuit EXCEPT R23 which is a 10k SMD resistor (instead of 4.7K)and R24
which is another 10K fixed resistor but with leads and soldered to the
upper side of the board.
So the situation is that I have a fixed value of 20K whereas I should have
4.7K to 14.7K variable. I am guessing that with the resistance set to 4.7K
(ie the normal 10K pot at zero resistance) as per the manual circuit, the
keying would be at its softest (which is what I want) whereas I have 20K
fixed so I am guessing that is why the keying is hard and the mark/space
ratio is shortened.
Before I start some minor sugery on the board to restore the values to the
manual circuitry, is there anyone (a) who understands from my laboured
explanations what I am talking about 😊 and (b) can confirm that my
assumptions are on the right lines.
Thanks in anticipation of some knowledgeable responses.
Barry Simpson VK2BJ
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