http://elecraft.85.s1.nabble.com/K2-VCO-Alignment-Issue-tp7651214p7651222.html
> Hi Don,
>
> Thanks for the quick response. I did check C72 again. It is a 271
> value. I then spread the red turns on T5 as far as I could. I'd say
> they cover about 90+% of the toroid. I put the L30 slug at mid-point
> of travel and measured voltage at R30 and it is still right at 8.37
> V. While there I checked the frequency at TP1 and it was 8247.90,
> which is considerably lower than the 8913 that you expected.
>
> Next I went up to 7100 and measured the voltage at R30. Still right at
> 8.37 V, no change. Frequency at TP1 @ 7100 was 11558.11.
>
> So, it appears that the frequency at 4000 is not within the expected
> range, and likely not at 7100 as well. Hope this tells you something
> because I'm stumped.
> I've got some plans for this evening so I may not get back on it until
> tomorrow afternoon, but if you've got any more things for me to try I
> will do them then.
>
> John, WB4GLJ
>
> On Sat, Apr 27, 2019 at 1:57 PM Don Wilhelm <
[hidden email]
> <mailto:
[hidden email]>> wrote:
>
> John,
>
> That high voltage is trying to reduce the capacity of the varactors.
> Which means there is either too much capacity or too much
> inductance in
> the circuit.
>
> Check the value of C72 first - it should be marked "271". Then set
> the
> L30 slug to about mid-position and spread the red turns of T5
> enough so
> the starting and ending turns are adjacent. What is the voltage when
> tuned to 4000 kHz? Measure the frequency at TP1 - it should be near
> 8913 kHz.
>
> Then change to 40 meters - 7100 kHz - What is the R30 voltage and
> what
> is the VFO frequency measured at TP1.
>
> The answer to those questions will help in determining what to do
> next.
>
> 73,
> Don W3FPR
>
> On 4/27/2019 1:32 PM, John Wingard wrote:
> > Working on my 2nd K2 (S/N 7869) and have run into a problem with
> the VCO
> > alignment. I'm getting a constant 8.37 V at R30 at 4.000 MHz..
> I cannot
> > change it with the full range of L30. Correct type inductor is
> installed at
> > L30. Dropping the VFO down to 3.500 doesn't change it either. I
> have gone
> > back through the archives and read just about every post
> concerning this
> > problem but nothing I have tried has made any difference. I have
> double
> > checked all correct parts placements and orientations, re-flowed all
> > connections in the quadrant of the board around the VCO section.
> T5 is
> > wound as per the manual (from the Toroid Guy) and installed
> correctly. I
> > have tried both spreading and compressing the turns on T5 with
> no change
> > either way.
> >
> > Regarding the thermistor board, I have 4.18 V on pin 5 of U6.
> >
> > Test in the previous section were within specs:
> >
> > 4 MHz Oscillator Cal using CAL FCTR was 12099.61 and confirmed
> with an
> > external counter.
> > Range of the PLL reference oscillator: 12099.61 - 12086.01 =
> 13.59 kHz
> > VCO oscillator test: 8162.60 MHz
> >
> > I'm about out of ideas at this point. What should I start
> checking next?
> >
> > Thanks for any help!
> >
> > 73 de John, WB4GLJ
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