[Elecraft] [K1] Internal Noise Bursts every 12 seconds or so

[Don Wilhelm]

Bob,

That is not a normal situation for the K1.

The "standard" answer is that it is the result of a poor solder connection.
I cannot guess at where it could be other than to say due to the 
periodic nature of the occurrence that it is associated with the MCU in 
some manner.
So check the soldering of the Front Panel board closely.

There is only one CPU in the K1, and it is on the Front Panel Board - 
the firmware on the band board responds only to the band change 
information from the basic K1.

Soldering Tutorial 101:
All solder connections should show that the solder has flowed out fully 
onto the solder pad as well as onto the component lead.  If you can see 
a ring around a component lead, that component has not been heated 
sufficiently.
If your solder connections result in a solder "blob" that is a bad 
connection (again resulting from insufficient heat to the connection).

Solder connections should look like mountains, but not like a volcano.  
In other words, there should be a small and nice fillet of solder 
between the solder pad and the component lead.

Some builders seem to worry about heating the component leads.  The fact 
is that modern components and boards with thru-plated holes will 
withstand soldering temperatures for 5 seconds with no damage.
Watch the solder.  It should flow out onto the solder pad and the 
component lead in 2 to 3 seconds.  If it does not, the iron temperature 
is too low, and if that happens in less then 2 seconds, the iron is too hot.

I have repaired many transceivers where the problem was soldering - 
usually because the iron temperature was too low or the builder did not 
dwell long enough on the connection to allow the solder to flow out onto 
the solder pad and the component lead.

Modern components and through-plated boards will sustain a soldering 
temperature of 800 degF for 5 seconds or longer.

I recommend an iron temperature of 750 degF except for the KPA100 and XV 
transverters which have a large ground plane - for those, 800 degF will 
work much better.

73,
Don W3FPR

On 12/28/2015 8:16 PM, Bob wrote:
> I just completed assembly of a 30m/20m K1 up through the point of Receiver
> calibration.  Everythings has gone smoothly and all tests and alignment
> steps were completed successfully.  I can hear a 1 uV signal very clearly
> on both bands.
>
> However, there appears to be some internal periodic noise.  It is very
> raspy in nature and it repeats every 12 seconds.  I'm guessing it is being
> generated by one of the two internal CPUs.  I hear it on battery power with
> a shorting plug installed on the antenna, on any frequency and on both
> bands.
>
> Basically I hear a low level burst noise that lasts for 1/2 second, with
> about a 1/2 second gap, followed by a 3 second burst, then silence for
> about 8 seconds.  The entire pattern repeats every 12 seconds
>
> While it is very low level, comparable to the 1 uV signal that I aligned
> the receiver with, it seems to modulate even strong S9 signals.
>
> Does anyone know what this noise is and how to get rid of it?
>
>