[Elecraft] K2DSP puzzle

[Lyle Johnson]

Hello!

Two days ago Brendan, EI6IZ, noticed an occasional pop in the sidetone of
his K2 w/KDSP2 that wasn't present when the KDSP2 was not installed.

> When keying on a noisy band or when calling in a pile up the leading
> character element sometimes starts with a pop in the side tone, as a
> sound engineer I am pretty fussy about how things sound and I decided to
> take a look on the scope and see why the K2DSP sounded different to the
> K2AF in this area.

Working together, we came up with a solution that works for Brendan's K2.
It might work for yours, if you are noticing similar symptoms.

Then again, it might not...

THIS IS NOT AN AUTHORIZED MOD!

Parts required:

2 each 1.5 megohm, 5%, 1/4 watt resistors (brown-green-green-gold).

Remove the Control board from the K2.

1) Remove R17 (3.3M orange-orange-green-gold).

2) On the component side of the board, cut the trace between C23 and U6 pin
17.

3) On the solder side of the board, add a 1.5M (brown-green-green-gold)
resistor from the pad of R17 nearer C23 to U6 pin 17.

4) On the solder side of the board, add a 1.5M (brown-green-green-gold)
resistor from the other pad of R17 to U6 pin 17.

Reinstall the Control board in your K2.

OLD               R17
                 +------+
   /MUTE------+--| 3.3M |----(Q7 Source)
              |  +------+
              |
              +--- (Q6, Q7 Gates)
              |
            -----
     C23    0.01 uF
            -----
              |
              |
           (earth)

NEW               R17
                 +------+
   /MUTE------+--| 1.5M |----(Q7 Source)
              |  +------+
              |
            +---+
            |   |  new resistor
            |   |  1.5M
            |   |
            +---+
              |
              |
              +--- (Q6, Q7 Gates)
              |
            -----
     C23    0.01 uF
            -----
              |
              |
           (earth)

REMEMBER, THIS IS NOT AN AUTHORIZED MOD!

73,

Lyle KK7P