Coronado 575 Volume Control Issue

[Winky Dink]

I just finished the electronics on a Coronado Model 575 (Gamble-Skogmo, Nostalgia Air http://www.nostalgiaair.org/Resources/072/M0007072.htm). I powered up the set and immediately got good reception, but the volume control doesn't work right. At the lowest setting, where I should have zero volume I get low volume. Then, as I turn the control the volume level stays the same until I reach a particular point at which the volume jumps to a very high level.

I assumed the problem was the 75K ohm volume control. In the first quarter of its range it went from 70 to 800 ohms, the jumped to several Megohms.





Mechanically, it appeared to work properly. So I tried a good, used 100K pot, and I got the same result as before. A third pot also gave the same result.

This is the volume control.





All electrolytics and paper caps were replaced. The remaining components and tubes were tested and replaced as needed. Continuity through all coils was checked.

So, I must have done something wrong. I hope there's an obvious answer to this problem, and I'd appreciate any advice on the matter.

Thanks,
Henry