Be sure coupling caps between audio stages are same as original values. These are caps from plate of one tube to grid of the next stage. Increase values if necessary.
A tone control reduces high frequency response. It's can't actually increase bass.
As glasdave said, try another speaker. If the cone is frozen you won't have enough bass.
Model 115 has 15 tubes:http://www.grillecloth.com/sylvania/tub ... ubmit&db=5