• Country
• United States of America (USA)

• Manufacturer / Brand
• Sparks-Withington Co., (Sparton); Jackson, Michigan

• Year
• 1929/1930

• Category
• Broadcast Receiver - or past WW2 Tuner

• Radiomuseum.org ID
• 58957

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

• Number of Tubes
• 8

• Valves / Tubes
• 484 484 484 484 484 484 182 182

• Main principle
• TRF without regeneration; 1 AF stage(s)

• Tuned circuits
• 4 AM circuit(s)

• Wave bands
• Broadcast only (MW).

• Power type and voltage
• Direct Current supply (DC) / 115-125 Volt

• Loudspeaker
• Electro Magnetic Dynamic LS (moving-coil with field excitation coil)

• Material
• Wooden case

• from Radiomuseum.org
• Model: Sparton 931DC Equasonne - Sparks-Withington Co., Sparton

• Shape
• Console with any shape - in general

• Notes

• The Sparton 931DC Witherington model has one dial (primary tuning control knob) and offers a push-pull audio amplifier. Tubes according to the "Quantity and Types of Tubes" by Sparks-Withington for season 1929/30 would be 6 x  485_Sparton and 2 x 483 as model 301DC, but we show tubes 484 and 182 mentioned in the schematic. It does not make sense: 182 is a rectifier - this is a DC set only and 182 must be a special Sparton tube. See the article here about different radio seasons.

  In "Radio Retailing" May 1933, page 47, "Tricks of the Trade" we can read for models Sparton 69-A, 79-A, 930AC, 931AC, 931DC, 301DC and 301AC: "Fourth section of band-pass selector, just preceding RF sometimes cannot be tuned to resonance with first three sections, producing weak reception and loss in selectivity. Give first, second and third selector trimmers 3 turns clockwise. This makes slightly less tuning capacity necessary for given frequency and fourth section selector can not be adjusted for resonance. Balance set in customary manner with oscillator and output meter and re-adjust kilocycle scale on dial by loosening it on shaft and re-setting."

• External source of data
• Ernst Erb

• Source of data
• Radio Collector`s Guide 1921-1932

• Circuit diagram reference
• Rider's Perpetual, Volume 1 = 1931/1934 (for 1919-1931)

• Mentioned in
• The Radio Collector's Directory and Price Guide 1921 - 1965 (Rider's 1-22)

• Literature/Schematics (1)
• Radio Manufacturers of the 1920's, Vol. 3 (page 122)

• Literature/Schematics (2)
• Sparton Radio Service Manual (Sparton Manual 1, Bulletin 17-1, 2, Bulletin 6-3, 4)

• Other Models

• Here you find 817 models, 365 with images and 754 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
  All listed radios etc. from Sparks-Withington Co., (Sparton); Jackson, Michigan