[Elecraft] K1 sidetone problem

[Don Wilhelm]

David,

I would rather think that you have a problem with the T/R switch and the 
transmit signal is getting into the receiver.

But then, the receiver *should* be muted when in transmit, so check the 
muting circuit as well.
Q10 should provide a short circuit between the balanced input pins of U3 
during transmit.  The 2N7000 FETs are easily damaged by static during 
installation, and if Q10 is not fully conducting during transmit, you 
may hear a bit of the transmitted signal as well as the sidetone.

For checks on the muting circuit, first check the voltage at the gate of 
Q10 during transmit, it should be near 6 volts.  That is more than 
sufficient for Q10 to conduct fully.  If that condition is true, then as 
a test, solder a wire between pins 2 and 3 of U3.  If the problem goes 
away, then Q10 is not doing its job - replace it. Note: there will be no 
receive with that test wire in place.

73,
Don W3FPR

On 3/21/2013 8:57 PM, David L DuPuy wrote:
> Has anyone else had any problems with the sidetone on the K1?  I've just
> finished building and at low power (0.5 watts) I have heavy key clicks when
> sending.  At higher outputs, I'm getting a dual tone with heavy clicks,
> sounds like RF is getting into the audio.  The problem is worse on 20m, but
> it's a big problem on 40m too.  Any ideas on where to look for a problem?
>   The transceiver appears to be working normally otherwise.  thanks, David
>