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[TenTec] Omni C new owner thoughts

To: "tentec@contesting.com" <tentec@contesting.com>
Subject: [TenTec] Omni C new owner thoughts
From: Marinos Markomanolakis M.D. <sv9dru@hotmail.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 12 Apr 2024 09:30:37 +0000
List-post: <mailto:tentec@contesting.com>
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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