My Kenwood TS870 is drawing too much current. At 50W CW output it is drawing
20A. If I go for 100W it just keeps going up and kills the supply at 25A. Specs
say that it should take no more than 20A at 100W.

This excess current is when the rig is fed into a dummy 50 load as well when
into different antennas when matched to 1:1. The current varies slightly band to
band but only by a couple of amps or so. One clue: on 80M I can detune the
external tuner antenna cap (to 2:1) in one direction and the rig current can be
brought down to 14A with the power out staying at 50W. Under this condition I
can then increase the drive back to a current reading of 20A and get 100W. I can
reproduce this effect on 40 and 30M but to a lesser extent.

It has 2SC2879 finals. Is this a final problem? I don't have much test equipment
or expertise but I suppose I could change the finals if I had to. Actually 50W
is quite adequate for me (only 3DB down) and I have been using it this way for
quite some time with no noticeable differences in the quality of my operation.
Still it bugs me as to what is causing this excess current.