Hi folks, I have a query regarding a ballast tube for my Automatic radio. Schematic is pending right now but this radio has a Hytron BM-49B Ballast tube. Now I came across another tube that is listed as an RCA BK-49B. Would the BM versus BK designation be interchangable and okay to use in my radio? Oh and there is no reference as to what model number I have, however it has 5 tubes (includes the magic eye) plus the ballast tube. Any help anyone can throw my way would be greatly appreciated. Thanks Paul

Here is a quick link about the numbers on your ballast tube. Seems that it's just a difference in the dial lamp current.

http://www.radioremembered.org/ballast.htm