John,
Both frequencies are too low.
You have either too much capacitance or too much inductance in the VFO.
Count the number of times the red wire goes through the center of the T5
core - it should be 16.
Check relays K13, K14 and K15 for solder bridges.
Make sure the core of T5 is yellow.
You might have to try removing a turn from T5 if you can find no other
cause - there have been a few K2s in the long past where the
permeability if the T5 core was higher than expected, and removing 1
turn from T5 corrected things - I have not seen that recently, but I do
mention it 'just in case'.
If all else fails, you may have to "wind your way" through the relay
connections for the VFO Range Select area using the Relay Table on the
Schematic Key page as your guide for the paths through the relays.
73,
Don W3FPR
On 4/27/2019 5:37 PM, John Wingard wrote:
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 <[email protected]
<mailto:[email protected]>> 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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