Gerd:
I found this in the archives. It may or may not help. 73
*2/14/99*
Several weeks ago, someone on the list indicated that they could not rid
their Omni Six of audible "clicks" while listening with headphones. I
suggested removing plug 52 on the AF/IF Circuit board, but apparently, this
did not help.
After making yet another mod to my Omni Six last weekend, I noticed the
same problem for the first time: I was hearing audible clicks, to the point
of being annoying regardless of any front panel setting, including power
and AF loudness.
This weekend, I jumped in to find the cause. On my particular Omni Six,
several areas were contributing to the clicks. Through a combination of
regrounding, using shielded audio cable, and rerouting cables, I have my
Omni back to the point where no or clicks thumps are heard whatsoever. The
following steps may be of help to those who wish to minimize clicks in
their Omnis:
1) I'm a firm believer in removing plug 52 from the IF/AF circuit board.
Pull it, and tie-wrap it out of harms way.
2) Ground the heatsink tab of U8, the audio power amplifier. By pushing U8
against the side chassis, a hole can be drilled for placement of a #4 screw
which now grounds and heat-sinks U8 to the chassis.
3) Many audio cables use ribbon cable. I replaced several of these with
single-pair shielded cable to the AF pot, FIXED AUDIO Plug 57, and cut two
audio circuit traces on the AF/IF Board that were running too close to
other witching circuitry.
4) Cut the nylon tie-wrap that holds the cable bundle along side the
chassis near U8, separate and twist the wires, finding the right
combination that minimizes the clicks.
On Mon, Nov 21, 2016 at 1:22 PM, gerd Groos <df9ts.cw@gmail.com> wrote:
> Hello,
> I friend borrowed me an Omni VI, which is producing very disturbing
> audio-clicks in fast QSK mode, at any CW speeds, even with very slow
> keying.
>
> The clicks are louder than the received signal and quite distracting.
>
> I am including symptoms below for those who want to read on. Any ideas, and
> suggestions highly welcome.
>
> 73
>
> Gerd DF9TS.
>
> ===
>
> The TRX is click-free when connected to a dummy load. Symptoms appear with
> antenna signal (or white noise) on the receiver input.
>
> The clicks are produced in fast QSK only on key release ("key up") only.
> "Key down" is not producing clicks.
> TX signal is ok and click-less and without chirp (as verified with 2nd
> receiver). RX audio signal is with these clicks.
>
> I verified the "TD". "T" and "R" signals generated for internal tx/rx
> switching with a scope. They look similar to a quick Spice simulation I did
> of the circuit. I did however not see a lag between "T" going down and "R"
> going up.
>
> Slow QSK is without such clicks.
>
> On "slow QSK" the RX audio comes back up slowly on "key up".
> On "fast QSK" the RX audio comes back immediately on "key up".
>
> This makes me wonder if the cause is a timing issue on "key up".
>
> I did align the TRX following the manual, twice. BFO is well aligned also.
> The rig behaves as expected. Sensitivity and filters ok.
>
> Removing connector 52, extensively discussed in this list, makes no
> difference for this OMNI VI´s clicking.
>
> The clicks are present on Loudspeaker as well as on "Audio Out" cinch
> socket.
>
> Tnx for reading this far ;-)
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