[Elecraft] K3s problem

[Gerald Finn]

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