US2026800A - Receiver circuit arrangement - Google Patents

Description

Jan. 7, I R. RECHNITZER 2,026,800

RECEIVER CIRCUIT ARRANGEMENT Filed June 28, 1954 INVENTOR PUDOLF AE H/V/fZE/P ATTORNEY Patented Jan. 7, 1936 RECEIVER CIRCUIT ARRANGEMENT Rudolf Rechnitzer, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphie m. b. H., Berlin, Germany, a corporation of Germany Application June 28, 1934, Serial No. 732,751 In Germany May 23, 1933 4 Claims. (01. 250-27) In broadcast receivers comprising indirectly heated-receiver tubes, undesirable actions often occur during what is called the incipient stage or period of heating. For instance, in the presence of fixed regeneration, the receiver during the said period may be caused to start oscillating as a consequence of the greater slope or mutual conduotance of the tube and, as a result may whistle. It also happens rather often that when directly heated power tubes are used the high audio frequency amplification during the incipient heating state occasions intense bubbling in the loudspeaker which, however, disappears after the working process has been completed.

According to the present invention these actions are to be obviated by that the prematurely active tubes, i. e., the regenerative tube or the ,power tube, etc., are impressed during the incipient heating period automatically with an abnormally high grid biasing voltage. This abnormal biasing voltage may consist of a high positive or negative voltage according to which one is most suitable in a given case. The desired automatic action is to be secured by that the biasing voltage, or part thereof, is obtained in the form of a drop of potential of the apparatus current dependent upon the incipient heating period.

Figure 1 illustrates in circuit diagram form one embodiment of the present invention as incorporated in a regeneratively connected circuit, and

Figure 2 shows diagrammatically a preferred embodiment of the invention in connection with an amplifier circuit provided with indirectly heated tubes and a filamentary type tube.

Figure 1 shows an exemplified embodiment of the first case where during the incipient heating stage a high positive grid biasing potential prevails, that is, in connection with a regenerative audion. L, C, is the input circuit which by way of the audion condenser K is associated with the control grid of a screen-grid tube. This grid is moreover connected by way of the leak resistance RI with the negative terminal of the working 'voltage. Regeneration is insured by way'of a circuit comprising Ll, CI. The plate circuit includes, between anode and positive source of working voltage, the output resistance R. In parallel relation to the tube there is connected with the voltage source a series arrangement comprising R4, R3, and V. The screen grid is united with a point between R4 and R3, whence there is established at the same time a connection, by way of a resistance R2, with the control grid. The latter is here fed with two partial bias voltages. One of these-occasioned by virtue of the drop of potential across resistance V, at the beginning of the heating period, is equal to zero and. thereafter grows gradually. It compensates incidentally the positive biasing voltage on the potentiometer R4, R3, V impressed upon the con- 5 trol grid by way of the resistance R2.

Figure 2 shows the case of a directly heated power tube and illustrates how the high negative biasing potential required according to this invention is created. A biasing voltage of the negative sign oifers the merit that overloading of the power tube will be avoided under all circumstances. At the time of switching in, the biasing potential of the power tube is given and deter, mined by the fall of potential across the reresistance R, and thus the tube will be blocked. Later on, the increasing plate currents of the tubes 1 and 2 raise the fall of potential across V and thus gradually eliminate the blocking.

I claim:

1. In amplifying apparatus and the like provided with indirectly heated cathode and directly heated cathode type tubes the latter type being provided with at least one grid electrode, and wherein the energization of all the cathodes is started simultaneously, means for delaying the operation of a directly heated cathode type tube during the interval of time taken to heat the cathode of an indirectly heated type tube to substantially the normal operating value comprising means for applying a biasing potential to the grid electrode of the directly heated cathode type tube desired to be controlled which potential is of such value so as to render the tube substantially non-conductive at the beginning of the heating period of the cathodes of the tubes and means when the cathode of one of the indirectly heated cathode type tubes is energized sufliciently to allow normal plate current to flow through the tube for generating and impressing a bias potential upon the grid of the directly heated cathode type tube of such direction and magnitude to render the first named bias inefiective and to place a normal operating bias upon the directly heated cathode type tube.

2. In amplifying apparatus and the like of the type having a plurality of tubes at least one of which is provided with a cathode which takes an appreciable time to reach its normal operat-- ing temperature and at least another of which is provided with a cathode which takes less time to reach its normal operating temperature than the first mentioned cathode and a grid electrode and wherein the energization of all the cathodes of the tubes is started simultaneously, means for delaying the operation of at least one of the other of said plurality of tubes during the interval of time taken to energize the cathode of said firstnamed tube substantially to its normal operating temperature comprising means for biasing the grid electrode of said other tube so as to prevent operation thereof from the beginning of the cathode energizing period and means acting when the cathode of the first named tube reaches substantially its normal operating temperature and controlled by the flow of current therethrough for automatically changing the efiective bias on said other tube to render said other tube op erative.

3. In combination, an electric translating circuit including a thermionic tube provided with an indirectly heated cathode and a thermionic tube provided with a filamentary cathode and a grid electrode, means for biasing the grid of the second named tube with respect to its cathode so as to maintain said tube non-conductive after the energization of said circuit for a time sufiicient for said indirectly heated cathode to reach substantially its normal operating temperature and means controlled by the flow of current resulting when said last named cathode reaches substantially its normal operating temperature for changing the effective bias on the second-named tube to render the tube conductive.

4. In combination with an electrical translating circuit including at least two thermionic tubes and an energizing means therefor, said tubes being provided with anode, cathode and grid electrodes, the cathodes of said tubes having different heating characteristics whereby one of the cathodes takes substantially less time to arrive at its normal operating temperature than the other thereof, means for biasing the grid of the tube provided with the faster heating cathode so as to maintain said tube substantially non-conductive after the application of energizing potentials to said circuit for a time suificient for said slower heating cathode to reach substantially its normal operating temperature, and means controlled by the flow of current resulting when 2 said slower cathode reaches substantially its normal operating temperature for changing the effective bias on the grid of the faster heating tube to render the tube conductive.

RUDOLF RECHNITZER.

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