[Elecraft] K3 power fluctuation

[Randy Thompson K5ZD]

I have a factory built K3 (s/n 3668, Nov 2010) that has developed a problem.
Looking for suggestions or remedies.

 

For the past year the radio will occasionally have a fluctuation in power
output.  I will be transmitting on CW and the power will suddenly jump to
120+ watts out.  Then it will drop way down.  I assume something senses the
overpower and cuts back.  The power will oscillate a bit before finally
settling at normal.  It happens at any power level and when connected to an
antenna or a dummy load.  The problem will happen a few times and then I may
not see it again for a hours or days.

 

This weekend in the RTTY contest it got increasingly worse.  Seemed to be at
its worst when the radio was cold, but still would happen at random times.
I originally thought the problem was only on 10 and 40 meters, but later saw
it on any band.

 

This morning I turned the radio on and the power output is only 40 watts or
so.  If I send for a while the power output will climb towards 100W, and
then it will suddenly spike to 120+ watts. Once it spikes it begins the
oscillation of high output and then low output.  It doesn't fix itself any
more.

 

So I probably broke whatever was only partly broken.  Suggestions?

 

Randy, K5ZD