[Elecraft] K1 no sidetone

[Don Wilhelm]

David,

I know you changed the DAC which was the most logical failure point 
based on your problem description.
Yes, it is possible that the TONE/XIL signal is now stuck at a low level 
instead of high (or vice-versa) which would select a wide filter.

Since resetting the MCU did not help, my next suspect is the MCU itself 
or the EEPROM (front panel U3) - unless something is awry with the SCL 
signal from the MCU.  It is strange that the Power Control works 
properly, but the sidetone does not.

If you can locate another K1, you could try swapping the MCU to see if 
that is the problem, or you could arbitrarily replace the MCU with a new 
one.  Without doing some in-depth analysis of the digital signals and 
their relative timing with a dual trace 'scope, I can only guess at the 
probable causes.

73,
Don W3FPR

On 7/12/2013 3:44 PM, David L DuPuy wrote:
> Don,  still no sidetone or ability to change XFIL !  I have done the
> following:
>
> 1)  I checked C72 and RP3 solder joints carefully (with a magnifier), and
> although they looked fine, I reheated them briefly.
>
> 2)  I checked the solder joints on U2 two ways:  I reheated the joints
> carefully.  I also checked continuity, e.g., U2 pin 1 to J1 pin 5
> connector;  U2 pin 7 to top of R13, etc.  I also examined the joints with a
> glass.
>
> 3)  I then made a change in STP and also STL, but no sidetone.  I then
> reset to factory defaults per page 57; no sidetone.  I then had to
> recalibrate the OPF per page 53, as expected. I also checked VDD on U2 pin
> 7 and it's 6.14 volts.
>
> 4) XFIL is also (still) not changing, so I think the problem is on the
> XFIL/TONE line. However, the filter position sounds like the 'wide' FL1
> position,whereas it sounded like FL3 when I started to work on it this past
> week.  I changed the power out again to make sure it's still working fine
> after installing U2, and confirmed the power change on the S-meter on the
> FT-950, so OUTB is working fine.
>
> The XFIL switch and sidetone worked perfectly from the start, until my
> camping trip.
>
> What surprises me most is that the K1 was held in a 'cradle' which was
> screwed down to the dinette table in my camper, at an angle of perhaps 70
> degrees.  So it seems hard to believe the "loose nut" (which may or may not
> have caused the problem, and which was lodged behind the leads of RF U5
> LM2930T-8) could have gotten into the Front Panel.  I checked the voltage
> output of the LM2930 early on and it's fine.
>
> The receiver and transmitter appear to be operating normally, using my
> FT-950 as a reference.  Sorry for such a long email !  and I greatly
> appreciate your help.  David
>
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