[Elecraft] K3 VFO A tension AND Felt Hiss - Resolved

[Gary Smith]

A follow-up

Got back to the radio after mulling the comments this weekend 
regarding this asymmetric knob issue and... the felt hiss issue. Lost 
some sleep over it as that's the time I seem to best come up with 
creative things.

So.. I made a plastic feeler gauge of the pointy bevelled end of a 
Plackers flosser stick as that won't scratch the paint. I marked 
where the gauge stopped under the narrow end of the A knob and then 
compared it to the other side 180 degrees away. A marked (no pun 
intended) difference.

I then put that A knob on the B Vfo and did the same procedure with a 
new flosser stick. and indeed there was a slight difference here as 
well but in the opposite direction.

As the knob did not wobble on either VFO but tracked poorly, I 
surmised the shaft does not innately follow the straight path when 
tightened. So I loosened both nuts and this time applied a small 
amount. of pressure on the nut driver away from the low side. That 
resolved the problem. I then did the same with VFO B's shaft though 
it wasn't presenting an issue. I do try to keep symmetry in all 
things...

Issue Resolved.

Now as to the hiss. Some really interesting ideas, especially getting 
SWMBO to give up her softer felt in exchange for a nice dinner cooked 
by HWMS. But that doesn't apply here so the idea of the Fender washer 
was a worthy possibility & I was prepared to get two Nylon washers to 
see if some combination f the 2 felt washers & 2 nylon ones would 
work well but then I thought about it while tossin' & turning last 
night & it dawned on me: Wrap the felt washer with teflon piping tape 
like it was a toroid transformer. So I ran the tape through the felt 
washer and did so all the way around till the washer had no felt 
showing but the hole was still there. I put that in place and the 
give was still there because of the felt doing its job and it was 
silent because of the teflon
.
Wala... Success on all counts! 

Now to get to the post office to send out a TenTec VFO I just sold to 
apply the $ for more K3 goodies & get a present for Mom who turns 99 
on Christmas Eve.

Thanks for the idears, they got me to the solutions!

I'll have more questions as I still have to learn how to operate the 
K3 & I have yet the sub Rx on its way & the transverter interface.

73,
Gary
KA1J

> Hi Patrick,
> 
> Indeed there was a third felt washer with mine too. Presently I do 
> have it installed with the 2nd one in place. My knob wasn't loose 
> though, it was quite firmly attached once tightened. When I first 
> felt the knob rotate properly for say, 200 degrees of rotation & then 
> bind a little for the remaining 160 degrees (making up numbers here 
> but fairly accurate), I removed the knob and saw a little circular 
> scratch on the clear plastic cover where the edge of the knob had 
> scored it. I then put the knob back in place & put the K3 on end & 
> looked from underneath along the front plane & saw the knob was 
> resting with a slight tilt. Again though, this knob wasn't loose, it 
> was firmly attached.
> 
> I removed the knob & put the 2nd felt washer on top of the first to 
> get it off the plastic and add some tension and then tried it again 
> but when rotating the knob, I could hear a felt on felt sound like 
> scuffing two chalkboard erasers face to face. Not the end of the 
> world or anything but VFO B makes only the faintest of hissss from 
> the felt and B acts perfect.
> 
> The Best tension I can get for the A knob isn't as good as the VFO B 
> which feels darned good to rotate. I did rotate each of the shafts 
> before assembly to be sure they were OK & they both rotate with zip 
> friction. 
> 
> I could forego any friction at all & it would be fine & easy to 
> rotate but it would be a constant annoyance when I bump the VFO & 
> then be moved away from a frequency I'd narrowed in on. Since I will 
> forever be using VFO A, I do need it to feel natural.
> 
> Gary
> KA1J
> 
> > Well, I'll jump in here. I had the same problem a few months ago when I
> > assembled S/N 1889. The VFO A knob was way too loose no matter what I did. I
> > had followed the instructions and installed one (1) felt washer under both
> > the VFO A and B knobs. The B knob was fine. The A knob couldn't be adjusted
> > to my liking. Then I noticed I had an extra felt washer (i.e., a total of
> > three were included in the package). I added the second washer and life is
> > good. I have it setup so I can spin it and get a nice smooth run (maybe 6 or
> > 8 turns) as it freewheels but yet for my taste it's not too loose.
> > 
> > Like everything else of course it's all a matter of taste. Two washers
> > worked for me. If it was an accident (they included too many) then it was
> > fortuitous in my case. If by chance you have a third washer install it and
> > life will be good.
> > 
> > 73/Patrick
> > W7TMT
> >   
> > 
> > 
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