Marinos,
Thank you for your observations on the Omni C. I do not own one
myself, yet I am thinking someday I will want to buy a solid state
transceiver that does not require any microprocessors to continue to work
for years to come,
Ken N6KB
On Thu, Apr 11, 2024 at 11:31 PM Marinos Markomanolakis M.D. <
sv9dru@hotmail.com> wrote:
> Just my first impressions after getting my "new" Omni-C. It was brought
> from the US, full of all the options and in great shape, as part of an
> estate sale from OK, thank you Fred (SK) wherever you are !
>
> It is just such a nice rig, unbelievably quiet Rx, THE most pleasant I
> have ever used. Obviously designed by hams for hams. Too bad we have lost
> that hobby ideal over time, as a result of consumerism and falling victims
> of flashing lights, TV screens and useless gadgets in the latest and
> "greatest" radios.
>
> Besides needing some cleaning of the filter selectivity switches to bring
> it back to life, I had to deal with 2 issues and would like to share my
> experience with the group.
>
>
> 1.
> Rebuilding the PTO.
> It was working kind of ok to begin with, but with a "gummy" feel to it,
> which could get a little better with exercise, but a sure sign of its
> grease drying out. Carefully dismantling the rig to take the PTO out was
> 2/3 of the work.
>
> 1.
> The actual cleaning and regreasing it was very straight forward and fun.
> I ended up using the advice from wireless girl at
> http://www.wirelessgirl.com/Projects/SidebandRigs/TenTecPTOrebuild.html
> and not dismantling the PTO beyond what was necessary to completely clean
> the old grease before reapplying new lubricant.
> I believe the critical point is NOT to remove the (H) stop pin !
> Especially if you at least you do not have some spare new pins available.
> From the amount of force you need to exert to it with pliers in order to
> mobilize it, by the time you have taken it out, it would probably be
> damaged, and impossible to be reused. And you absolutely can do a perfect
> job in restoring the PTO without going through that step. Just take your
> time with isopropyl alcohol and Q-tips.
> For regreasing, I used PTFE lubricant, since the lithium one does have a
> tendency to become sticky over time. I did supplement the PTFE with some
> amount of white lithium grease around the ball bearings , since it can
> preserve metal to metal contacts better than PTFE.
>
>
> 1.
> A strange problem showed up when operating in the 40m band ONLY. After
> 15-30 min of warming up, a 10,55 Mhz "oscillation" appeared in TX even
> without any mic input. That would appear as a low level "carrier" less than
> 1W, coexistent with the normal SSB signal. This appeared to raise the SWR
> seen in the outboard bridge and in the rig's SWR indication, while TX ing
> in a perfectly tunned antenna.
> A lot of scenarios were considered and disproved, but then I observed a
> strange thing. This "oscillation" would completely disappear when
> activating the ATT in RX !!!
> The ATT board PIN diodes and transistors were checked ok, and finally I
> decided to check the 9 MHz trap alignment at the front end of the RX.
> It was found to be completely off, and after retuning it the problem was
> completely gone !
> So obviously, the 9 Mhz IF signal was getting through the front end and
> mixing inside the TX circuit to produce the
> creeping carrier. It probably only appeared in the 40m band, being
> filtered out from the BPF of the other bands.
>
>
> Reassembling the front panel, I replaced the burnt 6V mini -bulb with a
> 3mm bright white LED (with a 270 Ohm 1/4W resistor in series), and the
> result is extremely pleasing to the eye, especially in dark or low-level
> ambient illumination.
> It gives a very nice contrast with the display above.
>
> All in all, I am extremely happy with this new radio. I had in the past a
> Corsair - 1 and a Jupiter, but I like this Omni much better than both.
>
> Hopefully my experience can be of use to anyone servicing their 546 model.
>
> 73,
> Marinos, sv9dru / ki4gin
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