[Elecraft] K2 build - VCO Test / Alignment issue

Don Wilhelm w3fpr at embarqmail.com
Tue Jun 10 19:12:24 EDT 2008


JH,

It may be time to take a break and build the RF probe from the parts 
included with your K2.
What I am suggesting is that knowing the RF voltage levels at TP1 and 
other places in the VFO circuit would be informative and help us to 
assist you in your troubleshooting quest.

At this point, about the only thing I can suggest is that you check the 
soldering, and then re-check the soldering, and when that is done - 
check the soldering.  Soldering is the most frequent cause of failure.  
Oh, yes, toroid lead tinning is the second most frequent problem, so 
check the leads of T5 carefully and re-tin if necessary.  Check all 
active devices (diodes included) for correct orientation - the parts 
placement diagrams in the back of the manual are handy for checking 
orientation.

Look at the schematic for the RF Board sheet 1 to identify the 
components that are of interest for your problem.   Everything on the 
upper portion of that sheet to the right of U4 is on the suspect list.

73,
Don W3FPR

John Hoaglun wrote:
> I have entered the Alignment and Test Part II portion of my K2 build.
>  
> The "PLL reference oscillator range test" seems to check out fine. But when
> I run the "VCO test" (which is 80m @ 4000.10khz @ TP1 = 8-10MHz) I am not
> seeing much of anything on the frequency counter. (I see readings on TP2 and
> TP3 but not TP1.)
>  
> Any suggestions from others that have seen issues at this step in the check
> out process?
>  
> Thanks, JH
>  
> -----------------------------
> John Hoaglun
> NG0R - EN25
> http://www.hoaglun.com
>  
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