[RodB]

David, your might want to take a slower and more cautious approach to your project. Your speaker field coil gets it's energy by being wired into the power supply filter circuit where it performs double duty. It is a filter choke coil reducing the ripple on the high voltage DC supply and it provides the magnetic field for the speaker voice coil. Since one wire of the field coil is B+ and one wire of the output transformer is connected to B+ there is only three wires required to operate the speaker. It's not always evident when looking at the schematic but you should be able to trace it. The main thing to be cautious about is the B+ voltage is a couple hundred volts and it's on a wire external from the chassis. Potentially hazardous (tongue in cheek). Nice strip job on the cabinet. Please don't use polyurethane. IMHO, I much prefer lacquer and for darker areas I like to stain rather than lacquer tinting. Thanks for showing us your progress.