[Elecraft] [K2] PLL Reference Oscillator Question

[bviets]

Don,
I did the voltage tests and they both checked out.  U6 was at 7.4, so a
little under 8, but I would imagine that is within tolerance.  
73,
Byron 
N6UI


Don Wilhelm-4 wrote:
> 
> 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.
>>>>   
>>>>
>>>>       
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>>
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