[Elecraft] K2 VCO Alignment only 0.02V @ R30

[Don Wilhelm]

Jeremy,

I did some "playing with numbers" in the VFO resonant circuit, and I am 
coming to the conclusion that L30 and T5 are not connected together.  If 
my speculation is correct, you will find a break in the PC board or 
something not soldered.
With the K2 upside-down, look at the bottom of L30.  There is a row of 3 
pins.  The leftmost pin connects to the adjacent lead of T5.
Solder a wire across those two points as a test.  Then check the 
resistance to ground at the rightmost end of that row of 3 pins - it 
should be zero.

Let me know what you find.

73,
Don W3FPR

On 2/2/2013 2:48 PM, JeremyJones wrote:
> Hi Don,
>
> I set C22 to midway.
> PLL @ TP3 is 12099.12 - 12086.32.
> T5 is a yellow core, wound with 15 turns red and 4 green. I had to bring it
> down to 15 turns as recommended by Gary to get 8253.86khz @ TP1 when tuned
> to 4000.10 for the VCO test.  It was around 7694.39 with 16 turns.
> L30 is the correct part, and all diodes have been checked to ensure the
> correct part and placement.
> Soldering has been checked.
> Verified C67, C65, C64, C68, D13, Q18 for value and orientation.
> Relays click when changing bands.
>
> Still getting the following readings.
> 3500 = 8248.42
> 7000 = 12010.78
> 10100 = 14157.67
> 14000 = 16976.67
> 18068 = 18878.23
> 21000 = 15211.55
> 24890 = 16977.38
> 28000 = 18878.84
>
> I am at a loss for what to look for next. Everything seems to check out, but
> my readings are still off. Anyway I can try to isolate a faulty component?
>
>