K1 Intermittent Frequency Instability

[AJ1G]

My 40 and 20 meter K1 has developed intermittent frequency instability and sometimes complete loss of ability to tune (frequency display jumps and stays on 68.0 nominal on 40 and 63.0 nominal on 20). Lightly “mechanically agitating” the circuit board just behind the front panel will bring it back into stable operation, but any sort of movement (I run it QRP mobile in a Tacoma 4x4) will throw it out of whack again.  Three modes - normal stable, squiggly unstable, and locked at nominal 68 or 63 above 7.0 or 14.0 as noted above.  Seems like a bad solder joint or solder whisker somewhere.  Any suggestions on where to look?  K1 S/N 0291.

Chris, AJ1G Stonington CT
 from my iPhone
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[VE3NR]

Hi Chris,

Instead of spending time troubleshooting I would start with re-soldering
the Front Panel Board and connections. There are not that many
components so it shouldn't take that long. I had an intermittent
problem on my K1 and re-soldered the whole RF Board. Not very
sophisticated but it works.

Good luck!

Bert VE3NR




On 7/5/2019 7:01 PM, Christopher Bowne wrote:

> My 40 and 20 meter K1 has developed intermittent frequency instability and sometimes complete loss of ability to tune (frequency display jumps and stays on 68.0 nominal on 40 and 63.0 nominal on 20). Lightly “mechanically agitating” the circuit board just behind the front panel will bring it back into stable operation, but any sort of movement (I run it QRP mobile in a Tacoma 4x4) will throw it out of whack again.  Three modes - normal stable, squiggly unstable, and locked at nominal 68 or 63 above 7.0 or 14.0 as noted above.  Seems like a bad solder joint or solder whisker somewhere.  Any suggestions on where to look?  K1 S/N 0291.
>
> Chris, AJ1G Stonington CT
>   from my iPhone
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

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[Don Wilhelm]

Chris,

First check the 10 turn VFO pot and its connections on the front panel
board.  If the pot itself is the older one with a blue plastic shaft
(remove the knob to check), replace it with the newer metal shaft pot.

If that is not the problem, turn to sheet 1 of the RF Board schematic.
Reflow the soldering for all the components in the VFO area.

73,
Don W3FPR

On 7/5/2019 7:01 PM, Christopher Bowne wrote:
> My 40 and 20 meter K1 has developed intermittent frequency instability and sometimes complete loss of ability to tune (frequency display jumps and stays on 68.0 nominal on 40 and 63.0 nominal on 20). Lightly “mechanically agitating” the circuit board just behind the front panel will bring it back into stable operation, but any sort of movement (I run it QRP mobile in a Tacoma 4x4) will throw it out of whack again.  Three modes - normal stable, squiggly unstable, and locked at nominal 68 or 63 above 7.0 or 14.0 as noted above.  Seems like a bad solder joint or solder whisker somewhere.  Any suggestions on where to look?  K1 S/N 0291.
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