[Elecraft] KPA100 Power Output Problem

[John Grimm]

   K2  #4842  has  been fb for over a year, and I've been working between
   baby  diaper  changes to complete my KPA100.  Everything has proceeded
   smoothly through the bias current adjust, but having problems with the
   transmit  tests.   All proceeds okay to about 20 watts.  With K2 power
   control  set  to  50W output,  I hit TUNE and power output reads 20-25
   watts on  both  K2  and  external meter.  While TUNING, I increase the
   power  control pot clockwise, and power quickly jumps up to the higher
   (50W) output  level.  Toggle  TUNE  off  then back on again, and power
   again  drops  to  20-25 watts until I tweak/increase the power control
   pot and power out then jumps to a level >50W.  Toggle again, output is
   back  to 20-25 watts out until I tweak/increase the power control pot,
   and  power  then  again jumps  up  to  an  even higher  level.  Toggle
   TUNE off again and back on, and power out is back to 20-25 watts until
   I  move  the  power  control  pot,  etc. etc..  With the power control
   pot full clockwise the unit is putting out a full ~110W.  I re-did R26
   alignment and  all  seems okay.  Checked  the common reflector section
   and  didn't  see  anything  similar to this, so I'm hoping to get some
   investigation suggestions from any willing higher powers.

   Thank you in advance.

   John / K0YQ