A schematic with B (135 volts) & C (-9 volts) voltage can be found here:
http://www.nostalgiaair.org/PagesByModel/192/M0018192.pdf
Tubes require 2 volts on the filaments. This radio has a ballast in series with your tubes. Adjust filament voltage on tubes until it reads 2 volts.
Norm
:I am working on a Musicaire 38b92 battery set(Sentinel 33b chassis?). I need to know the A, B, and C voltages.Thanks, Phil