PLL Problems

[Michael Steel]

I am having problems with my K2 kit: S/N 030xx (bought used unassembled).

I am in alignment Test II portion of assembly, and I am having the following problems:

My PLL is reading a frequency between 04255-04265 (jumping fastly between them as well) at TP3.

At other points (including U4 pin 1) it is reading 12010.52 and is very steady.  

I have double checked all the components that were installed, but I had no luck there.  Does anyone have any advice on what might be wrong, or at least what area of components might be causing this?  

Thanks in advance!

Mike, N8VDM
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[Don Wilhelm-4]

Mike,

Your internal counter operation seems to be marginal.

There was a time (and as I recall it was near the serial number you
have) when the transistors Q9 and Q10 on the control board were weak.  
Take a look at those transistors - if they have a blue surface on them,
replace them as first recourse.  You can use 2N2222 (or PN2222)
transistors in this application, or order the proper 2N5179s from
Elecraft.  Even if they are black in color, you should still replace
them just to see if that fixes the problem.  If you need to just try the
2N2222s, there are two that you have not yet installed, being reserved
for the transmit section of the RF Board - you can 'borrow' those until
you obtain replacements.

As partial explanation - the signal from TP2 does not have as much
amplitude as the signal at TP1, so it is quite feasible for the
probe/counter to work at TP1, but fail at TP2.

73,
Don W3FPR

Michael Steel wrote:

> I am having problems with my K2 kit: S/N 030xx (bought used unassembled).
>
> I am in alignment Test II portion of assembly, and I am having the following problems:
>
> My PLL is reading a frequency between 04255-04265 (jumping fastly between them as well) at TP3.
>
> At other points (including U4 pin 1) it is reading 12010.52 and is very steady.  
>
> I have double checked all the components that were installed, but I had no luck there.  Does anyone have any advice on what might be wrong, or at least what area of components might be causing this?  
>
> Thanks in advance!
>
> Mike, N8VDM
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
> Help: http://mailman.qth.net/subscribers.htm
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>
>
>  

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[k6dgw]

Don Wilhelm wrote:

> There was a time (and as I recall it was near the serial number you
> have) when the transistors Q9 and Q10 on the control board were weak.  
> Take a look at those transistors - if they have a blue surface on them,
> replace them as first recourse.  

Had that problem, Don [S/N 5398], I may have been the first.  The
primary issue, as found by Gary in AZ was that the gain of the Motorola
transistors declined with frequency.  Worked fine at 4 MHz, sort of
lossy at 12 MHz [or whatever].  The Big E replaced them, and my K2 ran
perfectly.  I think they got it fixed by the 5500's.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2007 CQP Oct 6-7
- www.cqp.org
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