I have used the T725 to solve my 500R and 5000R speaker blues:
http://makearadio.com/misc-stuff/t-725.php
At $8.00-$10.00 USD they are a deal.
Quote:
Originally Posted by Station X
I had an SX28 push pull output transformer transformer with an open circuit primary winding which was the same size as the output transformer missing from this set.
Forum member Ed Dinning rewound it for me to the original spec with a 5000R secondary winding tapped at 500R. Why Hallicrafters decided to use these high impedances I don't know.
Before fitting the transformer to the chassis I scraped off the hideous gold paint from the chassis in the area where the transformer is fitted. I left some slack in the connecting leads so that I can lift the transformer enough to paint under it later.
Of course I also needed a 5000R speaker, so I made one using an 8" diameter 8 ohm speaker along with a 25:1 turns ratio transformer also supplied by Ed. This is how Hallicrafters made their own high impedance speakers.
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