[Elecraft] K3s problem

[Saul Broudy]

<<<< My K3s has been working wonderfully since bought new in 2015.  I use it for CW only and run it at 75 - 85 watts.  It has a new problem on 15 meters only.  After a short period of transmission the power will disappear.  Turning the power off and on restores full functions for another amount of time.  The receiver section is not affected.  Any suggestions for where I should start looking?  Thank you 73.Jerry W6RKE>>>>
I've been having the exact same problem with my K3S on 15m, except it now happens on occasion on 20m too.  I am operating at 100 watts.  Like Jerry, power returns for a while when I turn the rig off and on; haven’t tried switching bands,  I thought it might be an antenna matching problem(I'm using a half blown-down G5RV), but the SWR looks to be OK.  
 I will check the TX POWER setting as suggested by K8CN, and will be anxiously awaiting any other suggestions.
Thanks,
Saul W3WHK