03-15-2013, 01:06 AM
I enjoyed the Atwater-Kent video.
Be careful not to confuse the fact that the 46 radio is powered by DC with the concept of radio frequency and audio frequency signals across any capacitor. There's lots of AC at radio frequencies and audio frequencies in any radio, or else it wouldn't work.
It looks from my schematic of the model 46 that cap 34 (pins 4 and 6) blocks the + and - power from shorting, but it also provides a return path for AC audio frequencies from the plate of the #17 tube through the primary of transformer 26. I think those AF voltages are attenuated by resistors 37 and 38, but because the same line carries the DC bias for the screen grid from all of the #14 RF amplifier tubes, there could be considerable RF and AF voltages across capacitor 34.
Philco engineers wouldn't have put high voltage capacitors in this radio if they didn't need to, for reasons of cost, so be careful about changing them. As I said before, though, modern capacitors might handle high voltage transients better than the old ones, but I think I'd still defer to the original design specs.
Wiser heads than mine, with more experience with TRF receivers, might advise you differently.
Be careful not to confuse the fact that the 46 radio is powered by DC with the concept of radio frequency and audio frequency signals across any capacitor. There's lots of AC at radio frequencies and audio frequencies in any radio, or else it wouldn't work.
It looks from my schematic of the model 46 that cap 34 (pins 4 and 6) blocks the + and - power from shorting, but it also provides a return path for AC audio frequencies from the plate of the #17 tube through the primary of transformer 26. I think those AF voltages are attenuated by resistors 37 and 38, but because the same line carries the DC bias for the screen grid from all of the #14 RF amplifier tubes, there could be considerable RF and AF voltages across capacitor 34.
Philco engineers wouldn't have put high voltage capacitors in this radio if they didn't need to, for reasons of cost, so be careful about changing them. As I said before, though, modern capacitors might handle high voltage transients better than the old ones, but I think I'd still defer to the original design specs.
Wiser heads than mine, with more experience with TRF receivers, might advise you differently.
John Honeycutt
