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Ralph Mowery

In article ,
says...

This radio had an open speaker field coil. I subbed a choke from my junk pile in place of the coil and used a PM magnet speaker. I have no idea what the specs on the OEM field coil were or those of the choke for that matter. I just grabbed something to try. The choke is about half the size of a baseball if that makes any sense.
The choke came out of something God only knows what and how long ago and measures about 40 ohms. The filter, a three section twenty UF, two at 450V and one at 25 volts was replaced at some point and seems to be OK. I mention this because there is a very slight hum out of the speaker and I'm thinking that perhaps the elimination of
the hum bucking coil in the OEM speaker is the cause of this. The hum isn't that bad. as soon as you turn the volume up a bit it's really not noticeable but without using another electro dynamic speaker can I do anything about this? I'm also wondering if I sized the choke properly. Does anyone have any thoughts on these two
concerns? Thanks, Lenny

Did it have a slight hum before the coil opened up ? Could be the choke
is the wrong size, or unless the filter capacitors have been changed
lately, they are bad, weak, or whatever you want to call it. It could
even be some heater to cathode leakage in the tubes.