[TenTec] Triton IV low 80 meter output

[flyingsub at att.net]

               I have a Triton IV that works ok on all bands except on 80 meters where the power output drops to 60 to 70 watts.Unlike the other bands I have to rotate the drive control to the one o'clock before getting any output.The alc light will go on and off after ajustment on cw and power will go up and down.I've cleaned the pots and switch contacts to no effect. Has anyone else had this problem or a fix. Thank             
                                 Pete AA6ZE