My Second Radialva Groom Restore

[Yorkie]

Thanks Gary, as a rough guide would you know what the typical inductance value would be for a field coil designed for series connection, it is something I have not really looked into as I rarely do domestic radios, however one day I would like a 1930's domestic radio for our living room, hence my interest in these vintage circuit techniques.

Lawrence.

A good example of a mid 1930s UK set would perhaps be the Philco 444 'People's Set', so called as it was aimed at the 'ordinary wage earner' rather like the German VW 'People's Car' in production by then. It was an AC only 3 valve plus rectifier set at a very keen price by 1930s standards, of £6.6.0, which - when adjusted for inflation, equates to £370 in 2012. To put that price into perspective, the average price of a radio in the UK in 1929 was £24.00 (£1,200 equivalent in 2012). By 1933 the average price had dropped to £15.00 (equal to £860 in 2012), so the People's set really did bring radio within the range of 'the working man' during the depression years.

The field coil on that set, which carried the full HT, was 2,000 Ohms. The circuit is rather oddly drawn, but the power supply section is attached.

The fact that until after WW2 they hadn't really developed permanent magnet strong enough to not require a field coil to energise the speaker, meant that mains energised speakers in the 1930s were a significant part of the overall cost of a radio. Clearly, with a PM speaker and just a high wattage resistor across the reservoir and smoothing caps, a significant cost reduction was possible in later years as compared to a mains energised speaker.

Rewinding field coils isn't an easy DIY task as they use thousands of turns of fine wire - 48 SWG or thereabouts, but at least two BVWS members can udertake that task, (one being the chairman).