[Elecraft] K3 intermittent receive issue

[Ian White]

"Any or all of the above" - several people have suggested good ideas.
The strongest possibilities are a loose TMP connector or a multi-way
connector that needs re-seating.  Since the faulty connection is "right
on the edge" between working and not working, even a very gentle tug on
a TMP connector or a gentle jiggle of a board should reveal the problem.

The best tool that I have found for inserting, checking and removing the
TMP connectors is a pair of artery forceps. The finger loops and the
click lock give far better control than long-nosed pliers (smart people,
those surgeons!). Forceps are available in several different sizes and
shapes, and probably the best choice for working inside the K3 is the
straight 6-7in pattern. They are cheap and easy to find on eBay, and
well worth trying.

Since Chris is in the UK, a good alternative to Deoxit for treatment of
connector pins is Contralube 770 which is available from Maplin.

Regarding the rear-panel SO239, I was the person who suggested making a
direct ground return between the connector flange and the KANT3 or KAT3
board. OK, so "it works already" and "7999 other K3s can't be wrong"...
but it still isn't good practice to make a single-wire link to the
center pin while leaving the equal and opposite return current to find
its own way back to the board through a single-point connection between
the rear panel followed by a long, thin support pillar. The new
connection is made by attaching a solder tag under the 4-40 screw (as
seen in the Assembly Manual, Figure 29) and another tag to the nearest
point on the flange of the SO239. No wire is needed; the two tags are
simply bent until they overlap, and then soldered to make a shortest
possible return connection. Ohm's law dictates that this will now be the
preferred return path, so the poorer path through the metalwork is the
one that becomes redundant.


73 from Ian GM3SEK

>-----Original Message-----
>From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of
>Jim LeFevre
>Sent: 21 April 2014 21:03
>To: elecraft at mailman.qth.net
>Subject: Re: [Elecraft] K3 intermittent receive issue
>
>I recently corrected a similar problem on the K3 I put together. Same
>symptoms, and I found when moving the coaxial cable on the main antenna
>on the outside of the radio, I could duplicate the problem. I replaced
my
>exterior rg-58 cable/connector three times without relief, then found
that
>the SO-259 on the radio was the problem as it makes its shield
connection
>by mechanical contact with the case. Cleaned all, tightened, all works
good
>now. I think someone had posted that they made a redundant jumper to
tie
>the connector to the antenna shield by way of one of the connector nuts
to
>prevent this problem. Good luck. Jim WN8A
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