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City: Fountain Hills, Arizona
I'm rebuilding a Model 80 (Philco Junior). The primary of the audio transformer measures ~4.4k; the schematic calls for 364 ohms. Obviously needs replacement.
I have a same physical size scrap transformer with a primary resistance of 210 ohms.
Can this transformer be used safely as a substitute? Should I expect lower power output? The output tube is a 42.
Thanks, Don
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City: Roslyn Pa
Resistance is meaningless in this situation. What you need to know this the impedance of the pri and secondary. What you are looking for is one that has a 7000 ohm to 2 ohm (impedance not dc resistance). In reality a transformer that will match a 2A5, 6AQ5, 6BQ5,6K6, 6F6, 6L6, 6V6, 41, 42, 47, 6005 ect.. to a 4 ohm spkr is fine. Most of the aa5 transformer are kinda low in impedance (abt 1.5K)
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 11-05-2018, 06:07 PM by
Radioroslyn.)
Posts: 95
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City: Fountain Hills, Arizona
Thanks, Terry. My substitute transformer came from a 50L6 circuit and should work per your comments.
Don
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City: Sandwick, BC, CA
Quote Radioroslyn: "In reality a transformer that will match a 2A5, 6AQ5, 6BQ5,6K6, 6F6, 6L6, 6V6, 41, 42, 47, 6005 ect.. to a 4 ohm spkr is fine."
An output transformer for a #41 or a 6K6 is not a very good match for a #42, the plate load impedance is different, but one intended for the others should work, including one for a 50L6, though it may be too small in other ratings.
Regards
Arran
