|:Sorry for the lack of info - it's a Grunow 660. This is for the volume control and not the tone because the radio already has a separate tone control. Ed's right - I need to determine if this is indeed a linear taper or an audio taper. I assumed it was linear but could very well be wrong. But it sounds like planigan's idea would be worth trying. I am getting a fixed resistance from that tap of about 230k from the 0 ohm terminal.
Now that I've seen the schematic, I can tell you that the tap is for loudness control, that is, the ear hears frequencies at different volume levels. You will need a log pot, and if there is not a tap, you probably will not ever notice the difference. But if you are like me, you will want a one meg pot with a loudness tap. Not an uncommon animal.