‘Technical Shorts’ by Gerry O’Hara, G8GUH
|‘Technical Shorts’ is a series of (fairly) short articles written by Gerry O'Hara, a CVRS Director and vintage radio enthusiast, each focussing on a technical issue of relevance in repairing, restoring or using Eddystone valve radios. However, much of the content is also applicable to non-Eddystone valve receivers. The articles are the author’s personal opinion, based on his experience and are meant to be of interest or help to the novice or hobbyist – they are not meant to be a definitive or exhaustive treatise on the topic under discussion….
References are provided for those wishing to explore the subjects discussed in more depth.
AC/DC Set Lore
Why on earth would a company with Eddystone’s philosophy on manufacturing premium-quality sets produce several lines of AC/DC sets for over two decades? - this type of set usually being considered to be the bottom rung of the radio quality ladder. This is a good question – and one asked by many (check out comments on the Gerard’s Radio Corner website http://www.cs.uu.nl/~gerard/RadioCorner/Sets/Eddy670.htm).
Well, the answer lies in Eddystone spotting an opening in the market that was theirs to fill back in the late forties and well into the sixties - namely the marine receiver market. To quote Graeme Wormald in the EUG Quick Reference Guide (QRG) “Stratton’s north-eastern agent, Alf Willings of West Hartlepool had suggested that such a market existed. Most ships’ power supplies were 110v DC and the only sets available for such [supply] voltages were American midgets. These had no hash filter nor did they have short-waves or arrangements for a low-interference aerial. There would be a market for a decent general coverage receiver, he said, and there was.” The first set of this type bearing the Eddystone marque, targeted at ship’s officers and first class passengers as ‘cabin sets’, was the Eddystone S.670 in 1948 sporting 7 miniature B8A valves and a selenium rectifier. This model had a ‘half moon’ dial (photo, right), as fitted to the S.740, and was uperseded by the S.670A with a ‘slide rule’ dial in 1954 and then by the S.670C in the ‘MkII style’ case in 1962 through 1964, all with basically the same circuit. Again to quote the QRG “The whole 670-series was eminent over a twenty-year period and was probably the most...
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