Re: PLL Reference Oscillator Question

Posted by bviets on Dec 27, 2009; 2:38am
URL: http://elecraft.85.s1.nabble.com/PLL-Reference-Oscillator-Question-tp4219007p4219481.html

Hi Don,
Thank you for your response.  When I try the freq. range test, there is no freq. change.  I searched the reflector and found an earlier email response authored by yourself with the subject of: K2 PLL range test SN 05233.  That person had a similar issue, so it would seem I can start tracking down the problem based on your diagnosis in that email.
73,
Byron
N6UI

Don Wilhelm-4 wrote

Byron,

Don't be too concerned about the 4 MHz oscillator calibration at this
point in your assembly process.  Once you have completed your K2, you
can refine the calibration - see the K2 Dial Calibration article on my
website www.w3fpr.com for "the rest of the story".

Yes, 12650 is higher than the high end of the range should be, but
please tell me what the low range is - while in CAL FCTR, tap BAND+ and
tell me what the frequency is, then tap BAND- and again tell me what the
displayed frequency is.  Perhaps I can craft an answer to the possible
trouble spots from that information.

73,
Don W3FPR

Byron Viets wrote:
> Hello everyone.  I purchased my K2 kit about 4 years ago and as life would
> have it, I rarely have time to work on the beast except during holidays etc.
>  More time for amateur radio would sure be nice, but I'm not near retirement
> and for some reason I keep getting pesky bills in the mail.  Anyway here is
> my situation:
>
> 1) I am at the Alignment and Test, Part II portion and trying to get through
> the 4 MHz Oscillator Calibration section.
> 2) When I take a freq. measurement at TP3 for the PLL with the frequency
> probe, I get a reading of ~12650, obviously way too high.
> 3) I inspected parts, soldering etc and cannot find a fault.
> 4) Decided to do some signal tracing and performed a measurement of the
> reference oscillator signal on pin 1 of U4.  My reading is .51, instead of
> the expected 0.8-1.8. Vrms.
>
> So my question is this:
>
> It seems that the 12650 measurement is so high that it may be an indicator
> that the X1 crystal in the PLL oscillator is defective. However, with the
> low reading on pin 1 of U4 I'm not so sure about the crystal.  Could the
> increased frequency reading at TP3, cause the voltage drain on the U4 or am
> I barking up the wrong tree?
>
> I've looked through the email archives and haven't found anything quite
> similar to my issue.  I hate to start pulling stuff apart if the crystal is
> the issue and would like to hear what others think of the problem.
>  
>
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