Have a puzzleing situation.Can't seem to maintain setting on Cyber 211 mono block[right channel only].Left channel set at 5.25 requires set screw at 6 o'clock position,right channel requires full set screw position[say 11 o'clock] Both settings will vary during the day in accordance with the voltage out of the wall[118V-127V].Sometimes I just cannot get the right channel to reach 5.25,even on full setting. Could it be a tube,cap or what HELP. rollo