[Elecraft] K3/10 low power output, fails TX calibration?

[Ross Primrose N4RP]

My K3 #5143 has suddenly developed a low power output problem. Even with 
tune power set to 7W, it can only generate 3.5W or so on all bands 
except 40 & 80, where it can still produce 7W. Running the TX 
calibration in the K3 utility generates a failure when it starts as it 
can only do 3.7W on 160.

Ideas?

-- 
FCC Section 97.313(a) “At all times, an amateur station must use the minimum transmitter power necessary to carry out the desired communications.”