has anyone used or installed the new LT2N-COMBO board.. i installed the board in a cobra 29 ..the echo part of the board works fine ..the problem im having is with the talkback side of the board.. it works and is clear but the control pot does nothing..will not lower or add to the loudness of the talkback..i can unplug the control pot and it still will have the same db's on the talkback..basically its using the board as a resistor..any help or suggestions to this problem would be greatly appreciated .is this a factory defect?