[jrblasde]

Good morning, folks:

    I have a question about dynamic speakers. I’ve got two sets that feature one—a 46-480 and a 48-482. Anyway, I noticed on both schematics that there are two coils for the audio path. There’s a V.C. and a B.C. I’m pretty certain that I’ve heard that V.C. stands for Voice Coil, but what about B.C.?

   

Side note, but I haven’t begun restoring the 48-482. That’s why I don’t include it on my signature.

[462ron]

The B.C. is the bucking coil or hum bucking coil. It’s in series with the output transformer secondary and the voice coil. It is wound along side the field coil and is there to introduce a small amount of AC out of phase with the AC or hum that the field coil causes to the speaker magnet, thus canceling out the hum heard. 

Ron

[jrblasde]

Oh, what a clever solution for hum! Thanks, Ron!