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Re: [TenTec] Omni C question

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Omni C question
From: Jeramy Ross <w5xtl@filexiii.org>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Mon, 10 May 2010 21:16:07 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
I'd like to thank everyone for their replies.  Loads of good
information, ranging from there will be minimal issues to there are
some parts that will fail and you need to start stocking up on those
parts now.  Quite a range!  A few trends seem to have emerged when
combining this with posts in the list archive and various sources on
the net.

1)  If you operate this rig conservatively, then everything should
hold up quite well over time, and you should have a great rig that
will probably out last the majority of people on this list.  If you
operate this rig like a DX crazed contester, slamming the switches and
spinning the knobs like a wildman in a DX induced fit of madness,
things will wear out, break, etc.  The same goes for abusing the rig
in any way.  (this pretty much goes without saying for any rig out

2)  There are some problem areas that seem to pop up with a bit of frequency:

     A)  The Resonate control (RX preselector) seems to become loose
and "wobbly" with time and use.  I am unsure of the mechanism of wear
here as the fixes are as varied as the symptoms mentioned.  From
fitting with felt washers, to actually going in and "rebuilding" the
control (which unfortunately there were no details in this "rebuild"
with that post on the internet so that didn't shed any light on

     B) Obvious risks of PA damage from either not using a ps designed
to work with this rig or not using an alternative protection device
(fast acting circuit breaker or other current limiting circuit).  All
examples of PA failure I have drug up from the depths of the internet
involved failure that would, it seems, have been prevented had the
operator had one of the aforementioned protection mechanisms in place.
 Also, the PA transistors and drivers are still available, and for
reasonable prices from many vendors and Ten-Tec themselves.

     C) Bandswitch components are getting hard to find, and with
abuse, can become loose, worn, and inoperable with time.  A parts rig
or two with good bandswitch components should mitigate this failure
for a very long time.  Also, again, this seems to be an area where the
type of use was directly proportional with the failure rate.  Ten-Tec
themselves mentioned that wear in this area of the radio was mainly
seen in rigs that were "used hard."  Being a former Kenwood Hybrid man
(collected, restored, repaired, and sold them), the bandswitch in
those rigs (except for the section in the PA cage) seemed to be of a
more delicate design and had issues of a different sort (dissimilar
metal junctions that caused a nearly guaranteed corrosion issue at
some point in the rigs lifetime and a weak shaft coupler design in the
later rigs of that series... both easily fixed).  Even with those
issues in mind, I had never seen nor heard of a worn out bandswitch in
those rigs (other than from blatant abuse and ignorance when trying to
work on one).  With that in mind, and those being contemporaries of
each other, I am not worried about the bandswitch all that much.  I am
assuming one will see similar lifetime and performance.  Also, have
not seen any examples of this being a failure mode of these radios
anywhere on the net, which seems to back up this assumption.

     D)  Display controller chip.  Obsolete and long out of
production.  However, it, and compatible variants were used in other
rigs (both Ten-Tec and those of other manufacturers.  Yaesu FT-902DM
(and 101ZD in later production models) used a similar IC with similar
issues, and identical lack of availability.  A gentleman in JA land
was able to produce a replacement with a programmable PIC and a
handful of parts that assembled on a nice and neat daughter card that
went into a socket that was put in place of the original chip.  It
shouldn't be much harder to do the same for the Omni-C.  Even so,
again, this is a mentioned point of failure, but little mention of
actual failures in this area out there on the net.  Potentially a
problem in the future, but not likely on any given rig.  Most mentions
of failure also came with mentions of over/under voltage conditions or
some other form of PS issue.  I believe there to be a relationship

     So, armed with that knowledge, I believe I have put most of my
fears at rest, and am satisfied with my rig choice and fully expect it
to last as long as I do with little issue.  The only area I still have
questions is the resonate control wear.  It seems to be the most
common issue.  What is the mechanism of the wear?  Is it merly a issue
of things getting loose with use and out of adjustment?  Actual part
wear?  Combination of the two?  What is the best fix?  I'm not a fan
of the fiber washer fix so often mentioned as it seems like more of a
band aid if there is an actual way to repair the cause of the problem
(i.e. adjustment, mechanical parts replacement or refurbishment,
etc.).  Thoughts, advice, knowledge happily accepted!

Thanks again,
Jeramy / W5XTL
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