David, There is a resistor that is switched in on 10 and 15 meters to form a divider with the ALC pot and lower the RF power out required for the ALC to compensate for the lower gain of the PA on those bands ( Thats why 2SC2879's are a popular replacement, more high frequency gain). The predriver pot is normally turned CW from CCW less than 1/2 turn to get ALC on 10 meters with 40 meters set at 145 to 150 watts out. If I remember correctly the explaination I got from Drake for lowering the power to 120 watts was for PA stability on 40 meters, keeping the predriver below 1/2 turn. I set up TR-7's for 140 to 150 watts myself with the predriver initially set at full CCW, then turn the predriver CW until I just get the ALC LED at 29.0 hmz. I have had no issues with any of them. With 2SC2879's the predriver gain will remain nearly full CCW.
73, Gary W8PU http://home.roadrunner.com/~w8pu
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