[R-390] R 390A range of RF gain

[ngietz at mymts.net]

    Still working on this 1963 Teledyne radio, and since it’s my first 390A, I’m not
totally familiar with it.  So... how much of a control range should I expect on
the RF gain control?  I get nothing until I dial it up to about 6 on the scale.  I
tried subbing the original (I believe) with a nice Allen Bradley 5K pot and it
seems to operate about the same.  Is this typical?
    The pot swings the cathode bias measured at the pot from 0V (max gain) to 
+21.5 (min gain).  Does that sound right?
   Nelson