[NJARC] Fw: A little radio theory question ...

[Jim Whartenby]

Al


I had a Majestic console that had a open interstage transformer.  I used a small power transformer as a replacement that was rated 117 volt primary to about 375 to 425 volt secondary.  Worked like a champ.  In looking at some industrial 120 volt primary to 24 volt secondary transformers with welded E & I laminations; I found that they were not as good for audio.  If you have an audio oscillator and o'scope, you can do a quick check to see what you might have around that will work.Good luck,Jim I wonder why people argue over the 10% of their differences and ignore the 90% they agree on?

      From: Al Schapira <w2ads at verizon.net>
 To: Al Klase <ark at ar88.net>; njarc at mailman.qth.net 
 Sent: Friday, July 20, 2018 11:52 AM
 Subject: [NJARC] A little radio theory question ...
  
... concerning interstage audio transformers in TRF sets.
Say you have a UX-200 detector stage transformer coupled to the following UX-201A stage.Typically, the transformer ratio is 1:3 or 1:4 (primary:secondary) for an impedance ratio step up of 9 or 16 to one.
Now, the plate resistance spec for the UX-200 is 30k and the UX-201A grid is otherwise open and the 201 is usually biased at -4.5 volts. So1) How critical is the turns ratio?2) How critical are DC resistances in the primary and in the secondary?3) What are typical values for the DC resistances in the primary and secondary windings?
You guessed it. I have three TRF sets with open transformers. Anyone have any to spare?
Thanks.
 -Al, W2ADS www.gamma-five.com

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