Power Supply

Radio Record, Volume III, Issue 27, 17 January 1930, Page 11

Power Supply

ONCE the "B" battery voltage has dropped below 20 or 25 per cent. of its rated voltage it is best to discard it altogether. .A "dry" battery consists of certain chemical constituents such-as sal-ammoniac, manganese dioxide, zine, etc. The sal-ammoniac paste dries up and the zine container is usually partly "eaten away." It is really a waste of time to try and give new life to the cells, and it is more economical and generally satisfactory to purchase a new battery. A par-. tially run-down battery produces all kinds of troubles in the set. A POWERFUL mains unit in which heavy currents are dealt with should be built on a teak, baseboard, and provided with a bakelite or paxolin panel. When heavy currents and high voitages are handled, considerable warmth will be generated, unless the resistances employed are of an extremely substantial character. Teak is one of the less inflammable woods, and the panel materials mentioned do not easily burn or warp. It is always worth while remembering that oak, unless it is extremely well seasoned, has a very bad reputation for warping. If your set has to be used in a room where there is often a fire, choose mahogany instead of oak for wireless -cabinets. Brass screws are better than _ steel screws for radio sets. Steel and fron have magnetic qualities which to some 2 very smali extent may interfere with ' the operation of a receiving set. The effect, even when a large number of screws are used, will be a slight one, but, nevertheless, it is best avoided.