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SHORTWAVE CONVERTER

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Front view [17K]

  • Circa 1933
  • Unknown Waveband(s) .
  • 2 Valves - (VO4 + 1821 rectifier)
  • A.C. Mains
  • Original cost unknown
NOTES Tuning is accomplished via a two-speed dial, the outer control being fine tuning with the inner control providing coarse tuning.

The veneered cabinet is certainly professional, however the plywood back is very amateur. Yet the case has the number 5727 impressed into the wood and the plywood back is marked with a hand written "5727". The chassis metalwork is also professional with many items riveted to the chassis as if it had been on a production line. I'm in two minds about the component assembly itself.

The set looks identical to that illustrated in the book "Radio Radio" (figure 397) and described as being made by Eddystone, however this is probably incorrect. Site vistor "Mike", who owns an almost identical unit, adds the following comments :-

"I agree that the converter looks more like the result of a semi-professional backroom production line than a full commercial offering. This could make sense, and explain the Eddystone connection. It is known that Eddystone's retail arm (Webbs, who had stores in London and Birmingham) did make up items to customer orders, usually these were to designs published in the Eddystone Short Wave Manuals and intended for the home constructor. The only catch is this converter does not match up with any known Eddystone circuit, but if made by Webbs would explain why it may have been seen as an official Eddystone product in the past. The tuning dial is definitely Eddystone".

1935 Advert - Click for larger view [110K][December 2004] The puzzle is finally solved. The unit is almost certainly produced by Unit Radio of London, whose advert from the Television and Shortwave Magazine of August 1935 is dhown opposite (link to larger view [110K]). Although not identical the appearance is remarkably close.
SERVICE DATA Click on image for full size view [56K]Mike has also supplied a sketch of the circuit which, give or take an equivalent valve, seems to match my unit. Follow this link for larger schematic [56K].
CURRENT STATE Dusty but overall not too bad. Although the shades of the left and right hand veneers look quite different, this is probably just the lighting as they look much better matched in reality.
WHERE FOUND The watery skip antique shop for £11.
Under chassis view [15K]H.T. Smoothing chokeDry electrolytic, 4uF+4uF   Top chassis view [11K]1821 Rectifier ValveVO4 Valve

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J.Evans 2003,2004
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Last updated
11th December 2004