[Elecraft] K2- Lost Sidetone?

[W3FPR]

Paul,

With that SN, you must use U8-4 as the sidetone source.  That is wired 
into the K2 Control Board.
There may be something else in the sidetone path if that menu selection 
does not set it right for you.
If you have a 'scope and can follow the schematic, you should be able to 
find the source of the failure.

If it worked once, I have no idea why it did not work the next day (but 
I have some guesses).
If you upgrade the firmware to 204R there is no choice, the sidetone 
source is fixed at U8-4.
U6-25 is used for the RS232 TXD if the K2 has the KIO2 or the kPA100 
installed, so that is not a visble option for your K2 (unless it has an 
unmodified Rev A Control Board) - not likely, but there may be a few 
where the Control Boar was replaced with an earlier Rev A one - hard to 
tell if yours was one of those.
Only earlier (prior to SN3000) K2s need to be rewired to change the 
wiring to match the wiring on the later boards.

Before version 2.04R firmware was intorduced, we had a lot of "sidetone 
lost" queries.  That was likely because the user did a "button dance" 
and did not exit the menu after changing the menu source - tapping the 
Display button after the change was the most common - powering down 
after making the change with no other actions would result in the same 
behavior.

73,
Don W3FPR

On 6/14/2025 2:27 PM, Paul Ecker wrote:
> I recently acquired a K2, serial #04028. This K2 has MCU 2.04P and IOC 1.09
>
> When it arrived the sidetone was working fine. Now I have no sidetone. I am
> hoping that somehow in attempting to learn the menu system – I somehow
> turned it off?
>
> If I press Menu>STL>Edit> Display; I see either U8-4 or U6-25. If I exit
> using the menu button, after either – I still have no sidetone. It seems I
> want U8-24  as a source.
>
> At one point in me trying the menu sequence I described above, I got the
> sidetone back, but when turning on the radio on the next day, it was gone
> again.
>
> Wondering if  anyone has any suggestions on how I can fix the loss of
> sidetone. I am mostly a CW operator, so no sidetone on the K2 – kind of
> stops me from using the K2.
>
>