[Elecraft] [K2] VCO Not Oscillating

[Don Wilhelm]

Joseph,

The first thing to check is T5.  The direction of the windings is 
critical, and the leads must be in the proper holes as shown in the 
diagrams in the manual.  In other words, the sense (direction) of the 
green wire turns on T5 must be the same as the direction of the red wire 
winding.

If that is correct, the VCO will oscillate, and things usually fall 
'into line' after that once L30 is adjusted for the proper voltage at 
the left end of R30.

73,
Don W3FPR

On 4/28/2014 8:22 PM, Joseph Baxley via Elecraft wrote:
> Hi,
>
> I've been trying for the last four days to figure out what is wrong with my
> rig.  I'm at Phase 2 Test and Alignment and got to testing the frequency of
> the VCO.  It had a reading of 00000.  Also the voltage on R30 was 7.87V.
> This is consistent with the VCO not oscillating.  The reference oscillator
> works fine and was within the expected ranges when I looked at it.  What I
> was able to notice was that U4 on the RF board has two pins with voltage
> values that are out of spec.  Pin 1 has 0.9V and pin 13 has 0V.  If I read
> the table they should be 2.1 and 4V respectively.  It also seems that the 0V
> on pin 13 is causing a 0V reading on pin 6 of U6.  Otherwise U6 is in spec.
> I got out my oscilloscope and got a Vrms of 1.13V on U4 pin 1.  There wasn't
> anything on pins 3 or 6 of U3.  The voltages for Q17, Q16, and Q18 are as
> follows:
>
> Q17   E: 0V
>           B: 7.13V
>           C: 0.08V
>
> Q16   E: 0V
>           B: 0V
>           C: 7.13V
>
> Q18   G: 0.08V
>           S: 6.64V
>           D: 0V
>
> I have been measuring and testing voltages and components for the last four
> days and have run out of things to look at for the moment.  If any of you
> can help me with what my problem is, I would be most grateful.
>
> Sincerely,
> Joseph
> KI4ITG
>
>
>
> --
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