I'm finally going to break down and start doing my own soldering, and thought that maybe I'd make some adapters so that I can use other sorts of tubes in my Singlepower (tube complement == 3 x 6sn7's). 7n7's should be easy --they're just a rewire. It was suggested that I try 5687's. Based on this:

the 5687 adapters have a network to keep them from oscillating, it's not just a straight pin to pin job.

and other posts (mostly from Jacob), it seems that it's not a straight rewire. Anyone have any idea what the "schematic" would be?

Any others that are straight rewires that I should also try?

Thanks for any info.

If it's oscillation then my guess is resistors on the grid pins. For the 5687 this would mean resistors from a few hundred to maybe a few thousand ohms on pins 2 & 7.