[Kenwood] TS-830s ALC voltage

[James Barrie]

Hi... I'm new to this list...  have a problem... when I tune up my 
830s, my ALC voltage
fluctuates wildly. I've cleaned the drive caps, and all rotatary 
swtitches.
Exchanged the 12BY7 with a know good one.  I get 125 watts output. I
tested with a fellow ham about 2 miles away and my output never varied.
This happens on all bands, but seems to be  worse on 10 meters.

Any suggestions?
Thanks.
                      Jim
                      WA8SDF