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
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[Don Wilhelm-4]

David,

Those AF1 and AF2 signals are indeed connected - but not directly. They
go to the AF Gain control on the Front Panel.

Sorry that the MAX518 replacement did not bring the sidetone back. The
signal from FP U2 pin 1 should be a square wave at your sidetone pitch.

You might want to check the soldering on RF Board C72 and RP3.

There is a chance that the MCU is sending correct data to the power
control circuits, but not to the sidetone generation.  I would first try
changing the sidetone pitch in the menu to write new information into
the MCU memory, and if that fails, reset to the default conditions (see
page 57 of the manual) - after which you will have to do some
calibration for those values that were retained in the menu.

73,
Don W3FPR

On 7/11/2013 8:37 PM, David L DuPuy wrote:

> 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
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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