Frequency Counter Probe not working S/N 5567

[McMillan, Terry]

Hello



I've been busy building my K2.  I have completed the control and front panel boards with all checks reading as they should.  Have just completed Part I of the RF board and everything checks out fine except when I test the frequency counter probe on the left side of C22 the display does not change from 00000.00.  Tried both sides but nothing reads on counter.



Checked the archive and found that Tim Soxman describes the same problem and found a short on his probe coax.  I have checked for continuity between the two pins in the crimp housing with the results being wide open.



Robert C Reisenweber also describes the problem and found it to be a bias voltage on Q10 that touching up solder joint fixed.  I have re-examined all solder joints in the area.



My questions are:



Is there something I can do to isolate the problem to either the probe or the control board?



How do I check the bias voltage on Q9 and Q10 ?



What can I do to isolate the failing component?



Thanks for your help.



Oh, one last thing.  Can I carry on with building Part II or will that get in the way of troubleshooting this problem.  Can I power up the radio again without completing part II.



Terry

VA6MAC



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[Don Wilhelm-3]

Terry,

Is there a possibility that you have the pins in the housing reversed?  The
shield should be closest to the side panel.

There is just not much to the frequency probe - a piece of coax with a 10 pf
capacitor in series with the center conductor, so not really much to go
wrong.

To test the counter (without the probe), you can connect a clip lead with a
series 10 pf capacitor from the counter input to the control board (pin
furtherest away from the side panel) to C22 (any 10 pf cap will do - use one
from the kit, or a 12 pf if you can't find a 10 pf) - if you find a reading
anywhere near 4 MHz, then the counter is working and you will find your
trouble in the probe - or there is a chance that the reference oscillator is
not working (and that is a bigger problem).  If you have another receiver,
connect a short antenna wire and put it close ot C22 to see if you can
detect a 4 MHz signal present.  But then, if the microprocessor is
responding and you have an LCD display, then the 4 MHz oscillator is likely
working.

You can continue building, but you will need the counter probe when you
begin the Alignment and Test II.
I would hesitate to say that you should power up the K2 during the process
of building the Part II stuff - if something goes wrong, it is difficult to
predict what the problem may be.  Normally, passing the resistance checks is
an indicator that it is OK to apply power.

73,
Don W3FPR

> -----Original Message-----
>
> I've been busy building my K2.  I have completed the control and
> front panel boards with all checks reading as they should.  Have
> just completed Part I of the RF board and everything checks out
> fine except when I test the frequency counter probe on the left
> side of C22 the display does not change from 00000.00.  Tried
> both sides but nothing reads on counter.
>
> My questions are:
>
>
> Is there something I can do to isolate the problem to either the
> probe or the control board?
>
>
> How do I check the bias voltage on Q9 and Q10 ?
>
>
> What can I do to isolate the failing component?
>
>
> Thanks for your help.
>
>
> Oh, one last thing.  Can I carry on with building Part II or will
> that get in the way of troubleshooting this problem.  Can I power
> up the radio again without completing part II.
>
>
> Terry
>
> VA6MAC
>

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