The Ultradyne (Phenix) IF transformers

TEST RESULTS

I purchased some of the original Phenix Ultraformers from PTOP and here are my findings.

I have one Type A and three Type B.  The only difference between the two is that the "A" has lighter coupling, about 1/4" between primary and secondary while in the "B" the coils are right next to each other.  These transformers are sealed, with the "REL" logo , and I didn't want to go butchering them up but the "A" that I received had previously been opened and one of the "B"s had the logo already broken.

     
There are simply two windings inside.  No caps.  They are wound very well and are very solid components compared to the Victoreens I had mentioned earlier.  The connection points on mine showed a trace of green at the terminals so corrosion COULD be a factor if a transformer were to measure open.  The wire is in the mid-30s gauge, enamelled.  The tolerance between transformers was good.



There was some question before about the actual IF frequency of the Ultradyne circuit.  It appears to be based on 120 kc.
Abt 250 pf will resonate the secondary at that freq and 1000pf will resonate the primary.

Here are my measurements:

 Pri L mH
 Sec L mH
 Pri R
 Sec R
1(B)
 1.621
 6.178
 7.4
 15.7
2(B)
 1.595
 6.192
 7.1
 16.0
3(B)
 1.579
 6.178
 7.2
 15.9
4(A)
 1.543
 6.124
 7.1
 16.0
Measured with brass screw in place


Now to tune these as precisely as I did the Victoreens.  I also bought four NOS 250 pf mica caps from Gary.  They measure from 207 to 233 pf.  Using some in-place secondary measurements I can see how a guy *could*  wind up with these IFs peaking as much as 10 kc apart even with careful wiring.  Matching xfmrs is touched upon in the old texts but there isn't much said about how to tweak it out in circuit because they simply didn't have the accurate techniques to do so.  Nowadays we think signal generator and trimmer cap and its pretty simple.
So what we'll do here is use a similar wire gimmick as we did with the Victoreens hidden behind the mica caps to match them to the particular coil.  Given the generally low capacitance of the NOS Muter mica caps I plan to standardize on 130 kc just for simplicity, the goal is to get them all within 1 or 2 kcs, something I suspect was luck-of-the-draw back in 1924.

       


Back to the Ultradyne Project page

15 Jan 2006