Radio Road

Which tuner to get and getting the most from it. Thank God, for the radio!

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RE: 10.7 mHz Discriminator Transformer Repair

Posted by strijw426 on September 21, 2011 at 18:15:02:
Thanks for that suggestion. I joined that group and just downloaded and read the article. I have been in contact with Edward J Engelken of San Antonio who has done some of these repairs. He is mentioned at the bottom of the last page in regard to responses to the "Farago Letter". Ed is into restoring antique radios and has been a great deal of help in this project.

There are many variations on exact construction of IF and Discriminator and/or Ratio Detector transformers. Each one may have to be taken as an individual example although there are lots of similarities between manufacturers. The GL3654577 discriminator transformer in my tuner was made by Automatic Mfg. Co. There were no numbers on the schematic to identify pins, so I had to make a detailed drawing before I removed the unit from the chassis, and again at each stage of disassembly. Otherwise I would have made a mistake on reassembly. The one unknown in this unit is the value of the coupling capacitor between the 6BN6 plate circuit and the center tap of the secondary winding. Since the capacitor was shorted, I had no chance to measure capacitance as recommended in the article. Now it will be a matter of tacking across different values underneath the transformer afte reinstallation in the chassis. I have ordered an array of small pfd value disc ceramic 5% NPO capacitors to try one by one. When I get the right value the alignment should be very close as no adjustment slugs have been moved.