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SW-717


The General Coverage 550kHz to 30MHz SWL Receiver SW-717 was a Low End or Beginners Receiver that came on the market in 1971 and was produced until 1982. The SW-717 was a Solid State design and it replaced the Tube design GR-64 that came on the market in 1964, which in turn replaced the GR-91 that came on the market in 1961.

SW-717

My receiver suffered heavily from hum. The main reason was that the aluminum chassis was used as the zero voltage reference and also as a conductor between components. I have connected copper wires between the components and also replaced the original mains transformer with a toroid transformer. The toroid transformer is better in general but the difference it made in this case is negligible. Instead it was the use of the aluminum chassis as a conductor that caused the hum. The band-spread mechanism was of poor design and did not work. I have redesigned it and now it works.
SW-717 schematic


               
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