[HAM] Does the BC have a volume gain?

[Dave Bishop]

There are lots of places where changes in passive components could cause low 
pre-amp output.  I guess I'd spray the rheostat with De-Oxit to clean off 
the contacts, then check resistors for drift.  There is a 20K and a 140K 
under the matching transformer shield, a 140K in the rheostat box and a 150K 
under the pre-amp chassis that I'd look at first.  There should also be a 
100K tone pot that you can clean and rotate.  If you are actually loosing 
bottom end, you might try replacing the .25 cap in the rheostat box.  You 
could swap the 57 tube if you can find a replacement.  Its a fairly 
straightforward project to rebuild the pre-amp, replacing the caps as 
needed.  You might see an improvement in the tone, as well.

Regards,

Dave Bishop