![]() For normal low-voltage working the centre tapping point is used so that the 3,000 Volts indicated on the HT transformer is only some 1,500 and the 1,500 terminal becomes 750, Between the two transformers is a heavy duty potentiometer which provides further sub-division. Filament heating and HT windings are carried by separate transformers and the former by means of a centre tapping on its primary provides for halving the primary voltage applied to the latter. Rectification is by a half-wave valve and the variation of output is obtained from a pair of transformers, Fig. The current drawn is exceedingly small, so that this high voltage eliminator. Up to 3,000 Volts may be required and an almost continuous variation up to this value is provided. Tapping points on the transformers in conjunction with a heavy duty potentiometer permit of continuous DC voltage variation from zero to over 3 kV. A protective 10,000 Ω resistance is included in the HT+ lead, while a high resistance effects the discharge of the smoothing capacitors of the HT supply unit. The pin connections and wiring are given in Fig 2, A negative bias of some 200 Volts is applied to the shield by means of a voltage dropping resistance in the negative HT lead and takes the form of a leak resistance between the F and SH terminals. The filament heating accumulator must be insulated from earth. Negative biasing of the shield is effected through a resistance in the filament to HT negative lead. Critical control of filament current is provided. Just over a Volt is dissipated in the pair of filament resistances which provide fine and coarse adjustment. the precise value is shown on the tube used. A current of about 1 Ampere is required and. This protects the tube from damage, shades the screen and interior from light and gives accommodation for the filament resistances and ammeter, the last-named being an essential. The output is continuously adjustable up to some 3,000 Volts.Ī simple form of housing for the tube is a plywood box with a hole exposing the screen of the tube. The Tube Unit HT unit for providing the gun potential. the high voltage eliminator which produces the gun potential and shield bias and.the tube with its mounting, 2-Volt filament accumulator, filament resistances and filament ammeter.The complete equipment may be considered as three units:. In this article the endeavour will be made to put into practical form constructional details of the apparatus required for operating the tube, The internal construction of a Cossor tube is shown in Fig. Internal arrangement of the electrodes in the Cossor tube. It can be synchronised by electrical means, thereby removing the severe limitations in picture analysis by the use of revolving apparatus. To those who aspire to the possibilities of high definition television the cathode ray oscillograph appears an essential. Response curves of HF circuits are shown at a glance instead of by the laborious system of taking innumerable meter readings. ![]() Only the cathode ray tube can reveal the widely varying load conditions of a moving coil loud speaker due to the characteristics of its diaphragm. On the screen of the tube can be observed both the amplitude and frequency distortion which an LF signal may suffer in the process of amplification. In the hands of the experimenter the cathode ray tube opens up a vast new field of interest and instruction in a manner which has no ready parallel among the meter methods of test. ![]() The visual indication which it can provide as a guide to receiver performance reveals instantaneously many properties of a set where the more complicated method of observing by the aid of several meters and deducing the results might well be expected to take some hours. Recent months have shown a rapid growth in the popularity of the cathode ray tube among set manufacturers and experimenters. The inclusion of a filament ammeter or voltmeter is essential. Those readers who may not wish to acquire such an equipment at the moment will, nevertheless, be interested in understanding its operation. The purpose of this article is to give the reader practical information to enable him to set up a cathode ray oscillograph, with its associated apparatus, so that it can be used for a variety of experimental investigations into the behaviour of wireless receivers and other apparatus. Practical details of the subsidiary apparatus required for operating the Cossor tube.
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