Sparton 39 Equasonne

Sparks-Withington Co., (Sparton); Jackson, Michigan

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  • Year
  • 1928/1929
perfect model
  • Category
  • Broadcast Receiver - or past WW2 Tuner
  • Radiomuseum.org ID
  • 58604

Click on the schematic thumbnail to request the schematic as a free document.

 Technical Specifications

  • Number of Tubes
  • 9
  • Main principle
  • TRF without regeneration; 3 AF stage(s)
  • Tuned circuits
  • 4 AM circuit(s)
  • Wave bands
  • Broadcast only (MW).
  • Power type and voltage
  • Storage and/or dry batteries
  • Loudspeaker
  • - For headphones or amp.
  • Material
  • Wooden case
  • from Radiomuseum.org
  • Model: Sparton 39 Equasonne - Sparks-Withington Co., Sparton
  • Shape
  • Tablemodel, Box - most often with Lid (NOT slant panel).
  • Dimensions (WHD)
  • 610 x 267 x 318 mm / 24 x 10.5 x 12.5 inch
  • Notes

  • The Sparton model 39 has one dial (primary tuning control knob). The models 39, 69, 79-A, 89, 89-A, 99, 109 and 930 are the first "Equasonne" models. The tubes are the original line up, not replacement, according to the page "The quantity and types of tubes used in Sparton receiving sets" and of Rider's page Sparton 5-6, displacement would be the tube 486. The model 39 and (later) model 49 share the same tubes (and schematic).
    See also the article here about different radio seasons.

    The history to the Equasonne line: In February 1928 RCA sued Sparks-Withington for using the Alexanderson TRF patent. After that, Sparton began using a circuit not covered by that patent, a circuit invented by Lester Jones (Technidyne Corp.). A tube with tightly controlled grid-to-plate capacitances was needed and Sparton-Cardon created the type 484, 485 and 486 and produced them too. Before, Sparton used Kellogg tubes. The Equasonne is a two chassis construction. The RF chassis with 6 tubes used (also?) a phenolic board, not metal. The trick is a 4-circuit pre-selector followed by a broadband amplifier system. Then follows the audio unit with a power-detector (plate detector) with a very high value cathode resistor for a non-linear detector which amplifies.
    The next season followed the Equasonne models 49, 101, 110, 111, 111-A, 301, 301-DC, 931 and 931-DC. The last Equasonne appeared in 1930/31 as models 103, 235, 564, 570, 574, 589, 591, 593, 600, 600-DC, 610, 610-DC, 620, 620-DC, 737, 740, 740-DC, 750, 750-DC, 870.
     

  • External source of data
  • Ernst Erb
  • Circuit diagram reference
  • Rider's Perpetual, Volume 1 = 1931/1934 (for 1919-1931)

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