[Elecraft] K1 sidetone problem still

[David L DuPuy]

Followup on my post about a week ago.  After a nut fell off inside the K1,
I lost the sidetone and the selectivity seemed to be on #3 (most
selective).  I'm receiving signals on the air just fine, so it's clearly a
sidetone/audio problem, and not an RF problem.  I can set the power level
just fine, so OUTB on the D/A U2 is working fine.

I ordered a new MAX518 (U2 on FP) D/A from Elecraft and installed it.  No
problems are visible.  And I still have no sidetone.

I put a 'scope on U2 OUTA and when keying slowly (set to 8 wpm) I see a
signal, but the scope will not trigger on it (on timebase 0.2 ms/div, and a
1 kHz test signal is clean).  The same messy signal appears on the AF Amp
IN2 (pin 2) on RF board.  I can see the bars on the LCD, so I am pretty
sure the transmitter is keying just fine, and I can hear a clean signal on
an adjacent receiver.

Unrelated (to my sidetone problem):  just below AF Preamp/Mute on the
diagram I see to pins marked AF2 and AF1.  Are these points connected?  It
looks to me like the audio signal has to pass through between these points,
but I don't see where they are located.  Any insight into this is greatly
appreciated, David