05-27-2010, 12:47 PM
Hello John, and welcome.
The article on my website about modifying the interstage circuit of Philco radios came mostly from posts made by John Grady, who is (or was) a regular poster on ARF. With his permission, I used his ideas to make the page on my site on this subject; all of his ideas and text is credited to him on my page.
http://www.philcoradio.com/tech/audio.htm
It is up to you whether or not you wish to use one of these mods. If I had any question about the audio transformer, I would not hesitate to use one of these mods. In fact I recently completed an early five-band 16B cathedral. Initially, I could only barely hear one local station - and then, after I carefully checked the circuitry, took voltage measurements, and had the thing set up to do circuit tracing with my signal tracer, it decided to suddenly start working on its own. Upon further checking, I noticed the screen grid of the 42 driver tube was glowing cherry red. The screen is tied to the plate in this circuit. So I subbed another 42, and the screen no longer glowed red. I then performed Mod B on this radio as I did not want to take any chances on it quitting again.
John Grady suggested using a 27K to 33K, 2 watt resistor. I did not have a 2 watt resistor in that range in my parts stock so I used a 30K, 1 watt resistor. The radio worked fine with the subbed resistor. I have to say though, I did notice a very small drop in volume after I performed the mod to the radio. But since the 16 has so much power anyway, I would say this is noticeable only to the very discriminating ear. Your 37-116 will also have power to spare, so a very slight loss of volume can be lived with, I think.
The article on my website about modifying the interstage circuit of Philco radios came mostly from posts made by John Grady, who is (or was) a regular poster on ARF. With his permission, I used his ideas to make the page on my site on this subject; all of his ideas and text is credited to him on my page.
http://www.philcoradio.com/tech/audio.htm
It is up to you whether or not you wish to use one of these mods. If I had any question about the audio transformer, I would not hesitate to use one of these mods. In fact I recently completed an early five-band 16B cathedral. Initially, I could only barely hear one local station - and then, after I carefully checked the circuitry, took voltage measurements, and had the thing set up to do circuit tracing with my signal tracer, it decided to suddenly start working on its own. Upon further checking, I noticed the screen grid of the 42 driver tube was glowing cherry red. The screen is tied to the plate in this circuit. So I subbed another 42, and the screen no longer glowed red. I then performed Mod B on this radio as I did not want to take any chances on it quitting again.
John Grady suggested using a 27K to 33K, 2 watt resistor. I did not have a 2 watt resistor in that range in my parts stock so I used a 30K, 1 watt resistor. The radio worked fine with the subbed resistor. I have to say though, I did notice a very small drop in volume after I performed the mod to the radio. But since the 16 has so much power anyway, I would say this is noticeable only to the very discriminating ear. Your 37-116 will also have power to spare, so a very slight loss of volume can be lived with, I think.
--
Ron Ramirez
Ferdinand IN
