[Patrick]

Fortunately, I had another 20 to check out. One that works. The pots were identical. So as OZ4 mentioned, I started swapping 24's. I first used the 3 good ones, and it worked. Then I put the 3 suspect ones in the good unit, and they worked!

Something else must be going on. But after going through about 10 tubes, I found a combination that worked. But the volume does level off at the top end, but no one listens full blast anyway, so I'm going to consider it fixed so I can move on. Not that curious. Life's too short.

Thanks to all.

Pat