Tips and Jottings

Radio Record, Volume IV, Issue 26, 9 January 1931, Page 15

Tips and Jottings

Short-Circuiting Dangers HE use of a metal "chassis," panel, or screen, in a modern set necessitates the greatest care in ensuring that only those metal parts of the components touch the panel (or screen) that are intended so to do. Unless all other parts clear the panel by a safe margin, there is always the chance of a short-circuit occurring, which might pe a serious matter. On Choosing Screws OOD screws with countersunk heads are generally unsuitable for use on such articles as small fixed condensers, as they are liahle to break off the moulded fixing lugs or "feet." A round-headed screw will clamp the part quite firmly without damage. It is likewise not advisable to use thin brass screws in hardwood such.as oak unless the screw threads are greased, or a pilot hole drilled beforehand. Lack of these precautions may’ result

in the screw twisting in halves-an awkward happening. A good idea is to use steel screws, which are stronger and also allow of easy manipulation in awkward corners by means of a magnetised. screwdriver. An Interference Filter CORRESPONDENT writes enclosing a clipping from an overseas paper. It. describes a hook-up for ‘an-interference eliminator. It comprises a coil of 100 turns of No. 26 D.C.C. wire, wound on a 3in. cardboard former, and a fixed condenser of. about .0002 mfds. The exact capacity of the condenser will be found .by experiment. The connections are quite clearly shown in the —

accompanying diagram, and it is stated that the circuit is quite a good one for reducing machine interference. I¢ "is really a type of tuned circuit and should improve selectivity. Marking Out Panels JLPONITE panels may be quite eas= . ily- spoilt by over-heavy use of the centre punch when marking out. If, however, a finely. pointed bradawl is pressed firmly into the panel and twisted like a gimlet, it will make quite a sufficient mark to start a drill, and will not slip and mar the panel, while there is no danger of cracking the ebonite. Any burrs produced by drilling should be removed. Useful Tips OQ not allow a flexible battery cord to rub against the side of an accumulator, or stray acid may affect the insulation and ruin the connection, HERE hum is troublesome a different earth is always well worth trying. (HANGING your "B" battery plugs | may cause an unpleasant. click in | your neighbour’s receiver. \ O not use a baffle-board or a cabinet which has a hole smaller than the one specified for the cone you | are using as this will make for muffled + reproduction.