[Elecraft] K3 VFO encoder temperature sensitive?

[Stan Gibbs]

Yesterday was a pretty warm day and I had left my K3 (SN#4181) on into the
evening.  When I sat down last night, I was very surprised to see that the
VFO was incrementing in a non-uniform and sometimes very erratic manner.  I
tried all the resolutions and different bands, but the behavior was the
same.  Sometimes, several complete turns of the VFO knob would yield 0 (or
even inverted!) frequency change.

 

I turned the rig off and this morning I powered it up again.  It seemed to
be behaving normally, with the various resolutions appearing to be pretty
accurate for a single knob rotation.  Not completely spot-on, but close.  In
1 Hz mode, I might see 195 Hz change for a complete revolution.  How does
this compare with other K3's?  Should I expect exactly 200 Hz?

 

Finally, thinking maybe that temperature was the culprit, I left the rig on
all day today, monitoring the front panel (FP) temperature.  The temperature
in the morning was mostly around 35C after a short warm-up.  Is this a
reasonable temperature for a K3 out on a table with lots of ventilation and
the stand extended?

 

In the afternoon, as the FP temperature approached 40C, the erratic behavior
returned, unfortunately.

 

Has anybody else seen this kind of temperature related misbehavior?  I
wonder if the VFO A encoder has a problem.  The VBO B does not seem to
display the same problem.

 

Any insight would be appreciated.

 

73, Stan

KR7C