[Elecraft] Re: K2: Frequency Counter Problem (Was PLL Ref Oscillator Problem)

Sun Oct 5 21:36:33 EDT 2008

I had the subject wrong when I wrote my first post on this.  It is the Frequency Counter that's a problem and not the PLL Ref Oscillator.

I've checked my soldering and all is okay.  Where possible, I've also run continuity tests, and all is okay.  In addition, I've checked to make sure that I've used the correct components for the Frequency Counter.  

We had this discussion about soldering when I was building my K1, and the problem turned out to not be my soldering.

I have tested the 4MHz crystal with an HT by holding the HT's antenna right near the 4MHz crystal.  The HT was picking up a signal at 4MHz when near the 4MHz crystal (a trick you taught me).

I'm in the processing of borrowing a signal generator and a frequency counter from another ham, and possibly an oscilloscope.  Can I use them for the testing and aligning in place of the internal frequency counter, or is the frequency counter being used in other ways?

 The manual says that there may be a frequency counter probe problem.  I've cut the shrink wrap off the probe to check it, but don't see anything wrong.  Any suggestions as to what I should look for or test in the construction of the probe?

Assuming that I've soldered everything correctly, what other possibilities are there that might be causing the frequency counter problem?  What else can I test?

I did notice one strange thing -- when I tested RP5, I tested all the pairs, even though some are not used for the frequency counter.  Pairs 7&8 and 9&10 each tested out at 248 ohms and not 470 ohms.  Pairs 1&2, 3&4, and 5&6 did test out at 470 ohms.  I have to admit to being rusty at reading complex schematics like the K2, but I don't see anything that would cause pairs 7&8 and 9&10 to test out at 248 ohms when mounted on the Control Board (especially because the Control Board was NOT plugged into the RF board when I tested the resistance in RP5).  Is this a problem?

Jon
KB1QBZ

--- On Sat, 10/4/08, Don Wilhelm <w3fpr at embarqmail.com> wrote:

From: Don Wilhelm <w3fpr at embarqmail.com>
Subject: Re: [Elecraft] K2: PLL Reference Oscillator Problem
To: jperelst at yahoo.com
Cc: "elecraft reflector" <elecraft at mailman.qth.net>
Date: Saturday, October 4, 2008, 12:03 AM

Jon,

That check of the 4 MHz reference is there to help you determine the 
correct functioning of the internal counter probe - it has nothing to do 
with the frequency, but the reading should be steady at 4000.00 MHz 
(plus or minus 1 count in the last digit).

Since your results were variable (it should show a rock solid 4 MHz), 
something is wrong with your probe or with Control Panel Q9 or Q10 and 
their associated components.  Check your soldering carefully.  If you do 
not know what a good solder connection looks like, I refer you to the 
soldering article on the Elecraft website.  A good solder connection 
looks like a 'mountain' with a concave slope to it.  If your solder 
connections are convex (look more like 'balls of solder', then the 
solder pads did not receive enough heat and you have applied excess 
solder.  Wick away the excess and be sure the solder tapers off to an 
almost invisible edge on both the solder pad and the component lead.  I 
mention this repeatedly because the most common cause of builder failure 
is excessive solder and inadequate heating of both the solder pad and 
the component leads.

You must get a good reading at the 4 MHz reference oscillator test 
before proceeding to anything else.

Yes, you could have a bad component, but that is way down on the list of 
failures.  Check the values of  RP4 and RP5 on the Control Board, and Q9 
and Q10.

73,
Don W3FPR

Jon Perelstein wrote:
> On page 47 of the manual, I was testing the frequency counter.  I put 
> the counter probe tip to the left side of C22 (actually, it wasn't 
> clear which left side, but I put it to the left facing the panel as it 
> is mounted in the radio).  The LCD was jumping all over the place, 
> from about 00200 to about 04200.  As I held it there, it tended to 
> move toward the area of 04000, but it never stabilized in any way.
>  
> I went ahead and built more of the radio to get to page 63.  When I 
> attempted the 4MHz Oscillator Calibration on pg 63, I got 0000.00.
>  
> I'm not sure where to proceed from here.  Help!!
>  
> Jon
> KB1QBZ 
>  
>
>
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