[Elecraft] K3 displayed power out is incorrect

[Keith Trinity WE6R]

Hi Gary;
Look in from with the top off at the RF board where the KAT3 or KANT3 
board plugs in.
Check T4 for darkening, it gets cooked if DC is applied to the antenna 
connector (like a remote preamp power connected backwards or similar).
You mentioned a remote tuner? Does it get power up the coax?
T4 is our# E690126, FT37-61x2,18T #26,PREWND


Also we went to beefier D36&D37 somewhere in the early serial # range. 
Suggest shotgun replacing them if you don't find anything burnt.
They are on the bottom just opposite the KAT3/KANT3.
Our part # E560048 BAS70 Diode, 70V, SOT23     Infineon  BAS 70 E6327    
Digi-Key    BAS70INTR-ND

You mentioned arcing, if in the K3, it is most likely the SA1 spark 
arrestor on the KAT3 or KANT3 board.
With the top off, watch for it glowing when running higher power.
Our #   E980130  SURGE ARSTR,350VDC,800V PULSE    Digikey 495-1879-ND

When you get it fixed, you will want to run the TX gain cal again, and 
after that, remember to never transmit at exactly 1.0MW, 5.0 or 50watts!
It will cause an inadvertent manual TX gain cal that can mess up the 
gain cal.
Keith WE6R K3/K4 Tech