[Elecraft] K2 distorted audio on certain freq.

[Don Wilhelm]

Mike,

This is the Weird At One Frequency (WAOF) problem.  It occurs at the 
point where the PLL and VFO frequencies cross, and that usually occurs 
near 7185kHz.

First step in the cure is to flush cut every lead in the vicinity of
RF Board U4 and the VFO - so that those small leads cannot act as an 
antenna.
Then retest.
If the problem still exists, try removing C88 (soldered on the bottom of 
U4 between pins 12 and 13).  Retest again.

If still present, remove RFC15 - again on the bottom of the board 
between U4 pin 16 and the adjacent solder pad just to the right of pin 
16 - replace with a very short jumper wire.

Good luck with it - not all K2s suffer this 'malady', but unfortunately 
yours does have the problem.

Does your noise problem occur if you disconnect the antenna?  That does 
sound like some noise being picked up by the antenna.  I have never seen 
that behavior in a K2 before, and I have repaired over 1000.

73,
Don W3FPR


On 5/23/2020 10:38 PM, Mike Duke wrote:
>       I have a new acquisition. I traded my Corsair II for a K2. Going
> through it and finding small issues that need to be addressed.
>       Besides just needing a thorough alignment, have noticed that on 40
> meters at 7184.00, the audio is extremely distorted but not on any other
> part of that band. I have the owners manual, nothing in trouble shooting
> about distortion.
>       Ser. #3631.  K2 IOC 1.07.  K2 MCU 203.   KSB2 1.07
> 
>       Every 5 minutes I also here a noise like a quick cyclic pulsing for
> about 5 seconds and it goes away.
> 
>        Does anyone know of a  regimen of procedures I could start to
> troubleshoot and check these issues?
> 
>       Thank you
> 
> Mike
> Kj4pom
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