K2 BFO problem - need suggestions

[wa4ywm]

Greetings everyone,
    I have a 4+ year old K2 which has provided spotless service for me until
recently. I began to have an audio issue in that on power up I would not
have audio. I could get it back intermittently by either powering down and
back up or by switching through the modes.
    In doing some basic troubleshooting I discovered that by touching the
L33 coil in the BFO I would have audio again. While checking the BFO
frequency using the internal frequency counter I discovered that when I did
not have audio the frequency was reading either 4.5 or 5.5 Mhz depending on
the sideband selected. After regaining audio the frequency would be back at
4.9 MHz.
    Thus, it appears the oscillator is oscillating but at an incorrect
frequency until I introduce my body capacitance.
    Can anyone help me in troubleshooting so that I could isolate the
component or does anyone know of the most likely cause of such a problem?
Thanks fo your help,
Jim WA4YWM

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[Don Wilhelm-4]

Jim,

That behavior is indicative of a bad solder connection.  The main
components in the BFO area are X3 and X4, C173 and C174, D37 and D38,
L33, and RP6.  The path to the TP2 BFO counter probe also includes Q24,
C169, R98 and C168, but since the  problem seems to be frequency
oriented, I would suggest that the last list is only of secondary concern..

On a 4 year old K2, I believe you have the yellow core toroid at L33.  
You may do well to upgrade with the BFOMDKT which will provide an extra
degree of temperature stability for the BFO.  If you have the L33 toroid
wound with #36 wire (many turns, comes pre-wound), then you already have
that mod installed.

It is also possible that you have a bad BFO crystal, but check out the
other possibilities before reaching that conclusion.  Of course, if you
have to order parts from Elecraft, it is probably more economical to
just order the BFO crystals at the same time whether they are needed or not.

73,
Don W3FPR

Elmore's wrote:

> Greetings everyone,
>     I have a 4+ year old K2 which has provided spotless service for me until
> recently. I began to have an audio issue in that on power up I would not
> have audio. I could get it back intermittently by either powering down and
> back up or by switching through the modes.
>     In doing some basic troubleshooting I discovered that by touching the
> L33 coil in the BFO I would have audio again. While checking the BFO
> frequency using the internal frequency counter I discovered that when I did
> not have audio the frequency was reading either 4.5 or 5.5 Mhz depending on
> the sideband selected. After regaining audio the frequency would be back at
> 4.9 MHz.
>     Thus, it appears the oscillator is oscillating but at an incorrect
> frequency until I introduce my body capacitance.
>     Can anyone help me in troubleshooting so that I could isolate the
> component or does anyone know of the most likely cause of such a problem?
> Thanks fo your help,
> Jim WA4YWM
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>  

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Help: http://mailman.qth.net/mmfaq.htm
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Please help support this email list: http://www.qsl.net/donate.html