Weird K2 tuning thing (hand capacitance)

[TJ Campie]

Something seems weird with my K2 - when I put my hand near the front left of the face the frequency of signals on the band swing around wildly (sometimes I can get the signal to go outside of a 500 hz passband). Sometimes it settles back down to where it was before but sometimes not. It also happens if I push on the top of the cover on the top left too. I'm not sure if its a shielding issue or what but I took the cover off and stuck my hand in that corner and could not get it to act up until I put the cover back on.
I couldn't find anything in the manual about this type of behavior so hopefully somebody on the list knows of a way to fix this as it is getting a bit annoying.
Thanks! 73 de W0EA
TJ
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[Don Wilhelm-4]

  TJ,

That is indeed weird behavior for the K2.  I would suspect a solder
connection problem somewhere inside the K2.

If not a solder problem --
Did you flush cut the leads below the BFO inductor L33?  If not, the
toroid may be sitting too high and contacting the bottom cover.  And did
you put tape on the bottom cover where L33 is located to assure that the
toroid cannot make contact with the bottom cover?

73,
Don W3FPR

On 5/4/2011 7:50 PM, TJ Campie wrote:

> Something seems weird with my K2 - when I put my hand near the front left of the face the frequency of signals on the band swing around wildly (sometimes I can get the signal to go outside of a 500 hz passband). Sometimes it settles back down to where it was before but sometimes not. It also happens if I push on the top of the cover on the top left too. I'm not sure if its a shielding issue or what but I took the cover off and stuck my hand in that corner and could not get it to act up until I put the cover back on.
> I couldn't find anything in the manual about this type of behavior so hopefully somebody on the list knows of a way to fix this as it is getting a bit annoying.
> Thanks! 73 de W0EA
> TJ
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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[TJ Campie]

Thanks Don - I did not build my K2 but I checked L33 and it looks good. It seems the problem is more prominent when I push on the top cover anyway, which makes me think that L33 isn't the problem. Are there any specific components in the front left of the RF board I should look for specifically for bad solder joints?

--
TJ Campie, w0ea
On Wednesday, May 4, 2011 at 7:16 PM, Don Wilhelm wrote:

>  TJ,
>
> That is indeed weird behavior for the K2. I would suspect a solder
> connection problem somewhere inside the K2.
>
> If not a solder problem --
> Did you flush cut the leads below the BFO inductor L33? If not, the
> toroid may be sitting too high and contacting the bottom cover. And did
> you put tape on the bottom cover where L33 is located to assure that the
> toroid cannot make contact with the bottom cover?
>
> 73,
> Don W3FPR
>
> On 5/4/2011 7:50 PM, TJ Campie wrote:
> > Something seems weird with my K2 - when I put my hand near the front left of the face the frequency of signals on the band swing around wildly (sometimes I can get the signal to go outside of a 500 hz passband). Sometimes it settles back down to where it was before but sometimes not. It also happens if I push on the top of the cover on the top left too. I'm not sure if its a shielding issue or what but I took the cover off and stuck my hand in that corner and could not get it to act up until I put the cover back on.
> > I couldn't find anything in the manual about this type of behavior so hopefully somebody on the list knows of a way to fix this as it is getting a bit annoying.
> > Thanks! 73 de W0EA
> > TJ
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
>

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[K1FFX]

I had a problem with my K2 in the weeks after I built it that sounds similar to what
you describe, namely a significant change in frequency when pressing down on
the top of the case.

I posted here about it and Don (and others) suggested that I have a look at L33.

Visually, it looked OK, but I was reluctant to remove the part and try to clear
more of the soldered joints underneath the rubber insulator ... so I didn't go
there.

What I did do was (a) remove the tilt stand, which relieved a pretty severe
twisting pressure on the case and (b) put some additional spacers, in the form
of left-over washers, on each of the stand-offs on the bottom-side of the K2
to move the bottom panel further away from L33.

While this was not proof that L33 was the problem, it did make the problem go
away.

Cheers -

Bruce