04-26-2018, 08:39 PM
The out put transformer on this radio was a general replacement that did not match the impedance of the speaker (39 ohms). One of the members on the EH Scott forum kindly supplied an original transformer that had an open primary. Another transformer to rewind! This one is interesting in that the 2 halves of the primary are separated by the secondary windings. Half the primary is wound in the center, then the secondary windings on top of that, then the second half of the primary. Both parts of the primary have the same number of layers and turns, but obviously the outside half of the primary will have considerably more wire and, therefore, higher resistance. The primary resistance for one side is only about 120 ohms. The outside half was the open half so I couldn't measure it but it could wind up being maybe 30% higher. How does this affect the push-pull amplifier? Maybe the actual impedance of the longer half is really not that different than the inside half. Your thoughts on this. I could wind the primary in the "normal" way making the discrepancy somewhat less. One has to assume, though, that Scott had a reason for designing it this way.