ELIMINATORS FOR SMALL SETS

Radio Record, Volume I, Issue 43, 11 May 1928, Page 12

ELIMINATORS FOR SMALL SETS

A FEW HINTS

AN eliminator for a two-valye set will not be called upon to give any very high plate voltage, and probably 100 to 135 will be the maximum required for the amplifier valve. It requires a considerable amount of resistance in the circuit to cut down the mains voltage, and in the case of the eliminator working with a bellringing transformer, it js necessary to either add resistance to the ‘high’? output lead, or else take the plate current from the ‘low’ terminal only. In order to reduce the maximum output, one of the fixed resistances of 100,000 ohims may be placed in the output lead by cutting the latter in front of its connection to the first resistance and connecting instead to the brass clip which connects the two resistances. A variable resistance may then be included in the high output circuit, and placed upon the panel "MNHE above remark apply to 230volt supplies, as where the yoltage is only 110, no resistance will be necessary in the high output lead, as the voltage available will be reduced to 80 or 90 by the resistance of the valve used for rectifying. Nothing is gained by placing too high a voltage upon the plates of any valve, and it will often be found that maximum results are obtained at a figure considerably below the miaximum actually recommended by the makers. UN DULY high B voltage shortens the life of a valve, so it pays to ascertain from the leaflets enclosed in the packing the maximum voltage recommended, and for economy, keep under rather than above that figure. INSULATING LAYERS, N° attempt should be made to wind one layer of wire upon. another without a layer of paper in between when putting the windings upon transformers. The care with which the ends of the layers are treated has much to’ do with the lasting qualities of the transformcr. ‘The best way of ensuring a fit for the paper used between layers is to have the strips cut by a printer, all an equal width, and then by using the width of these strips as a gauge, make the spool the exact width, inside. By this means there will be practically no space through which the 86’s wire can sink down to the layer below, but it is still necessary to use great vigilance so that not a single turn goes astray, and — thie safest way to eusure this is to leave a space of say one-sixteenth inch at each end of a layer N° doubt some readers interested in this subject would notice last week a paragraph stating that an article had been "held over until next weck." That paragraph was written to appear on March 16, and along with several others had been held over by the printers, and these have recently appeared, though out of date. It is hoped at an early date to present another type of simple eliminator of easy |