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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