Model 80 audio transformer - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Model 80 audio transformer (/showthread.php?tid=19195)

---

Model 80 audio transformer - 45philcodon - 11-05-2018

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

---

RE: Model 80 audio transformer - Radioroslyn - 11-05-2018

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)

---

RE: Model 80 audio transformer - 45philcodon - 11-06-2018

Thanks, Terry. My substitute transformer came from a 50L6 circuit and should work per your comments.

Don

---

RE: Model 80 audio transformer - Arran - 11-07-2018

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

---