[Elecraft] PLL Reference Oscillator Question

[Don Wilhelm]

Byron,

Yes, that prior response may be helpful, but all may not apply to your 
case - each one is different.
To be specific for your problem, first monitor the voltage from RF Board 
U5 pin 7 while in CAL FCTR mode.  When tapping BAND+, the voltage should 
go to about 4 volts and tapping BAND- should drop the voltage to near 
zero volts.
If that is OK, then move on to U6 pin 1 - tapping BAND+ should produce 
about 8 volts and BAND- should produce nearly zero volts.

Check those conditions first.  If those are all OK, then you can move on 
to the varactor tests, but if there is a problem with the voltages 
above, get back with me for additional tests and actions.

73,
Don W3FPR

bviets wrote:
> 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.
>>>   
>>>
>>>       
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>>     
>
>   
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com 
> Version: 9.0.722 / Virus Database: 270.14.120/2587 - Release Date: 12/26/09 03:27:00
>
>