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I had never seen a cardboard IF transformer and so here are some pictures of two that I repaired in a Westinghouse W-683-A. The primaries and secondaries of both IF transformers were all open, again a new experience for me. The attached pictures show how the transformers are constructed and why they failed.
The ‘can’ of the transformers looks like metal but is in fact painted cardboard with a copper liner. I slit the cardboard cans lengthwise to access the internal coils and mica capacitors. Over the past eighty years, wax had solidified inside the cardboard coil former tubes, securely ‘welding’ the internal powdered metal cores in place. Because the cores could no longer rotate freely inside the tube, turning the adjusting screws rotated the entire tube inside the can, along with both coils, tearing the fine wires off the capacitors.
I soaked the inside of the coil former tubes overnight with mineral spirits to dissolve the old wax and free the cores. Luckily, the fine coil wires tore away from their solder joints on the mica capacitors, and not where they emerged from the coils, so I was able to solder them back in place. I epoxied the bottom of the coil former tubes securely to the inside of the base to prevent them from rotating again. And I coated the inside of the tubes with a light film of white lithium grease to lubricate the motion of the cores.
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