[Elecraft] [K2] PLL Reference Oscillator Question

[bviets]

Don,
I also took the liberty to do the checks on: RP2 pin 2, and the cathodes on
D16 and D17 and they all behaved like U6 pin 1: 7.4 and zero when switching
between BAND+ and BAND-.
73,
Byron
N6UI


bviets wrote:
> 
> 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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