01-26-2011, 09:17 AM
Philco Service Bulletin 180-B, Data on All Philco Speakers (also available as a free download here), gives the impedance as 5,700 ohms.
I just looked up the specifications of the audio output transformer used in Model 70, part no. 2673. In the 1946 Philco parts catalog, it states a primary impedance of 6,000 ohms.
I also looked up the 47 tube and I see a 7,000 ohm load is called for.
My information is only as accurate as the original Philco data I obtained it from. That does not make the messenger into a dummy.
Further...the 1946 catalog calls for a turns ratio of 91:1, and a secondary impedance of 0.62 ohm.
A quick look at the Hammond transformers on the Radio Daze site did not reveal any suitable replacements.
I think you've already solved your problem, though, with either of the transformers you currently have. With the Stancor, I think I would try the 0.42 ohm output first; if the sound was not to my liking, I would then try the 1.78 ohm output.
I just looked up the specifications of the audio output transformer used in Model 70, part no. 2673. In the 1946 Philco parts catalog, it states a primary impedance of 6,000 ohms.
I also looked up the 47 tube and I see a 7,000 ohm load is called for.
My information is only as accurate as the original Philco data I obtained it from. That does not make the messenger into a dummy.
Further...the 1946 catalog calls for a turns ratio of 91:1, and a secondary impedance of 0.62 ohm.
A quick look at the Hammond transformers on the Radio Daze site did not reveal any suitable replacements.
I think you've already solved your problem, though, with either of the transformers you currently have. With the Stancor, I think I would try the 0.42 ohm output first; if the sound was not to my liking, I would then try the 1.78 ohm output.
--
Ron Ramirez
Ferdinand IN
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