US2162350A - Universal receiver without transformer - Google Patents

Description

June 13, 1939. P; KAPTEYN 2,162,350

UNIVERSAL RECEIVER W ITHOUT TRANSFORMER Filed Aug. 3, 1935 Patented June 13, 1939 PATENT OFFICE UNIVERSAL RECEIVER WITHOUT TRANSFORMER Paul Kapteyn, Berlin, Germany, assignor to Radioaktiengesellschaft D. S. Loewe, Berlin-Steglitz, Germany, a corporation of Germany Application August 3,

1933, Serial No. 683,423

In Germany August 4, 1932 8 Claims.

In the case of universal receivers, which after slight alteration in the connections require to be capable of use in connection with all supply potentials and all kinds of current, various aspects 5 must be taken into consideration, which constitute subject matter of the present invention.

Since receivers of this nature should still perate even in the case of very low supply potentials (for example, 110 volts D. C.), the dimen- 1o sions of the house-circuit connection portions above all require to be such that an excessive loss of potential is unable to take place in the steadying resistances. It is, therefore, desirable to employ relatively small steadying resistances,

' and to obtain the requisite steadying action by the use of relatively large condensers. For reasons associated with the cost and weight it is advisable to employ for this purpose electrolytical condensers. When using condensers of this nature, however, there is encountered the disadvantage that consideration requires to be paid to the poling, as the condensers in the case of incorrect poling are quickly destroyed.

This danger exists when employing the receiver in connection with, direct current circuits, as it is not to be recognised immediately (above all when using indirectly heated, i. e., relatively slowly heated tubes) which poling is correct.

To overcome these difficulties, .1 have devised a novel arrangement, a typical example of which is illustrated by the accompanying drawing, which shows a three-tube system adapted for use either with alternating current (as by direct connection with a house circuit) or with direct current.

An antenna system of conventional type, shown at the extreme left, transmits the received impulses to the detector tube I connected in any well-known or approved manner to the first-stage audio-amplifier tube 2 and the second-stage 5 rectifier tube 4 may be excluded from the circuit for a purpose explained below; ordinarily, the switch 5 is in its lower position, so as to include the rectifier tube in the circuit. The anode of the rectifier tube 4 is connected with a terminal I0, adapted for connection with one D. C. lead (the positive lead) or one of the A. C. leads, the other D. C. or A. C. lead being connected to a common terminal 9. Each of the three tubes I, 2, and 3 is shown as having an anode, a grid, and

I a cathode, the three cathodes being connected in series and heated heaters, indicated below the respective cathodes. These heaters are connected in series, the righthand heater being connected with the terminal III, while the left-hand heater is connected with the terminal 9. The last-mentioned terminal is also connected, through a connection including a condenser, with the lower one of the two contacts adapted to be engaged by the switch 5, and through another connection said terminal 9 is connected with the switch 5, said second connection including an electrolytic condenser 6, a lamp 1, and a protective resistance 8, these three parts being arranged in series. The anode of the tube 3 is connected with the switch 5 through the resistance 8 and through a condenser shown directly above said tube, and loud-speaker connections are indicated from the opposite terminals of said condenser. Through suitable connections including a smoothing resistance l2, the switch 5 is connected with the anodes of the other two tubes I and 2. These two anodes are connected, by connections including condensers, with the grids of the tubes 2 and 3 respectively. The grids of the three tubes are connected, in the manner illustrated, with a device for producing grid bias, said device comprising the resistances l4, I5, l6 and the condenser I1. At I3 I have shown a by-pass condenser. Connections for a phonograph pick-up are indicated at 20 and 2|, with a protective condenser [9 in one of these connections and a resistance l8 in the other, said resistance being employed to diminish hum.

The following features are of particular importance in securing the results for which my invention was designed:

1. Upon changing over to direct current care is taken that none of the fitted electrolytic condensers is able to be applied to the supply circuit in direct fashion, but that in each case the resistance 8 of, for example, 2000 ohms or more is connected in front of the electrolytic condensers remaining in operation as compared with the supply terminals. Experiments have shown that when using a guard resistance of this nature incorrect poling even if continued for a relatively long period of time has no detrimental effect on the electrolytic condenser.

2. Since in the case of incorrect poling the insulation. current through the electrolytic condenser is considerably greater than in correct poling, a small lamp 1 (for example, a suitably dimensioned pocket-lamp bulb) may be connected in series with the electrolytic condenser 6. This lights in the case of incorrect poling, and prevents indirectly by filamentary lengthy operation with poling of an incorrect kind if its filament is so selected that the same fuses if heated for a long time (more than (0 hour).

3. Since the total current of the receiver is greater in the case of incorrect poling, the fuse connected in series with the receiver may be so selected that the same burns out in the case of incorrect poling over a relatively long period.

4. The best ensurity against incorrect poling is constituted by the rectifier tube 4 which is connected in series with the electrolytic condenser, and allows current to pass only in the one direction. This rectifier tube necessary for A. C. operation should accordingly preferably be allowed to remain in the receiver when changing over to direct current.

Further difliculties in connection with universal receivers are encountered as a result of the requisite potential guard, for example for talking machine connection such as indicated at 20, 2|, as the: steadying condensers allow alternating current to pass. In this case separation of the outwardly leading terminals from the supply circuit may be obtained either by an intermediate transformer or (and this is cheaper) by suitably connected series resistances such as indicated at 18, or condensers such as indicated at H].

In the prior art, one of the sound-box leads is usually applied in direct fashion to the grid, or the anode, of the first low-frequency tube, and is secured to a sufiicient extent against danger of contact by the series-connected audion combination, or the highly ohmic resistances sit-u ated in the anode circuit (in the case of resistance amplification), as the current occurring is unable to exceed a value which would be detrimental. The other lead is usually connected with the grid bias, the cathode or the anode potential of the receiver. These points owing to the necessary steadying condensers are dangerous to touch. It is, therefore, desirable to connect in this lead resistances which limit the occurring current in the case of contact.

The practical examination of receivers connected in this fashion has shown. that owing to the high A. C. potentials in the apparatus a humming noise occurred by reason of capacitative dispersion. This is caused above all by the fact that the sound-box is connected with the zero point in the apparatus, not in direct fashion, but through the medium of the guard resistance. The dispersion is particularly disturbing as the same, owing to their capacitative nature, favour quite particularly the greatly audible overtones of the supply circuit.

According, therefore, to the invention, there is not employed a guard resistance, but a guard condenser 19, the capacitative resistance of which in the case of 50 cycles is approximately equal to the value necessary for limitation of the current. As regards the higher disturbing irequencies, which above all cause the humming noise, this condenser forms practically a shortcircuit, so that the humming noise occurring is greatly diminished.

In order to reduce still further the humming noise occurring upon connection of the soundbox, the reception of humming disturbances is reduced in accordance with the invention by the fact that a distribution of potential is produced by means of the (ohmic) series resistance I8 in the lead to the grid or the anode. This resistance diminishes at the same time the amplification for the sound-box amplification, and must, therefore, be selected in such fashion that in the case of fully opened sound regulator the intensity of the sound in the loud-speaker is just sufficient.

In the case of tub-es having high voltage cathodes for universal receiversv of this nature a humming dispersion also takes place by reason of capacitative coupling of grid and heating connections. This is avoided to a considerable extent in accordance with the invention by the use of indirectly heated cathodes with double-wound arrangement of the filament, i. e., cathodes in which the heat requires to be supplied only from the one side. At the other end of the tube the free end of the filament there present is preferably screened oif by corresponding construction of the nickel jacket.

The elements 6, 1, 8 constitute a steadying filter. The resistances employed in the filters are of the order of 1000 ohms, and the condensers (preferably of the electrolytic type) used in conjunction with these resistances have a capacity of more than 6 microfarads, for instance between 6 and 8 microfarads.

I claim:

1. A universal receiver operable by connection with either alternating current or direct current mains, said receiver being provided with smoothing means consisting of ohmic resistances in the order of 1000 ohms and condensers, preferably electrolytic condensers, of more than 6 microfarads, said receiver further including, in the lead to one of said electrolytic condensers, a signal lamp acting as guard device and lighting in the case of incorrect connection of the receiver with direct current mains.

2. A universal receiver operable by connection With either alternating current or direct current mains, said receiver being provided with smoothing means consisting of ohmic resistances in the order of 1000 ohms and condensers, preferably electrolytic condensers, of more than 6 microfarads, said receiver further including, in the lead to one of said electrolytic condensers, a signal lamp acting as guard device and lighting in the case of incorrect connection of the receiver with direct current mains, the signal lamp being so chosen as to burn out when the incorrect connection continues for a relatively long time.

3. In a universal receiver having a supply circuit adapted to be fed with current derived either from alternating current mains or from direct current mains, smoothing means and a signal lamp in the supply circuit, said smoothing means consisting of ohmic resistances in the order of magnitude of 1000 ohms and condensers preferably electrolytic condensers of more than 6 microfarads and being connected in the lead line between the terminals for the mains supply, said signal lamp being also connected in the lead line between said terminals, said lamp acting as a guard device and lighting in the case of incorrect connection of the arrangement with the direct current mains.

4. In a universal receiver having a supply circuit adapted to be fed with current derived either from alternating current mains or from direct current mains, smoothing means and a signal lamp in the supply circuit, said smoothing means consisting of ohmic resistances in the order of magnitude of 1000 ohms and condensers preferably electrolytic condensers of more than 6 microfarads and being connected in the lead line between the terminals for the mains supply, said signal lamp being also connected in the lead line between said terminals, said lamp acting as a guard device and lighting in the case of incorrect Ill) connection of the arrangement with the direct current mains, said signal lamp being so chosen as to burn out when incorrect connection to the direct current mains continues for a relatively long time.

5. A universal receiver operable by connection With either alternating current or direct current mains, said receiver being provided with smoothing means consisting of ohmic resistances and condensers, said receiver further including, in the lead to one of said condensers, a signal lamp acting as a guard device and lighting in the case of incorrect connection of the receiver with the direct current mains.

6. A universal receiver operable by connection with either alternating current or direct current mains, said receiver being provided with smoothing means consisting of ohmic resistances and condensers, said receiver further including, in the lead to one of said condensers, a signal lamp acting as a guard device and lighting in the case of incorrect connection of the receiver with the direct current mains, said signal lamp being so chosen as to burn out when the incorrect connection continues for a relatively long time.

7. A universal receiver operable by connection with either alternating or direct current, said receiver having three potential supply terminals, the first of said terminals being properly connectable to the negative side of a source of direct current potential, or to one side of a source of alternating current potential, the second of said terminals being connectable to the other side of said source of alternating current potential, the third of said terminals being properly connectable to the positive side of said source of direct current potential, said receiver being provided with smoothing means including ohmic resistances in the order of 1000 ohms and at least one electrolytic condenser of more than 6 microfarads, said resistances and condenser being so connected together that in case of incorrect poling of said source of direct current potential with said first and third terminals, at least one of said resistances prevents the destruction of said electrolytic condenser.

8. A universal receiver operable by connection with either alternating or direct current, said receiver having three potential supply terminals, the first of said terminals being properly connectable to the negative side of a source of direct current potential or to one side of a source of alternating current potential, the second of said terminals being properly connectable to the other side of said source of alternating current potential, the third of said terminals being connectable to the positive side of said source of direct current potential, said receiver including a plurality of coupled multi-electrode vacuum tubes containing anodes and heatable cathodes, a rectifier having a heatable filament and an anode potential means, the input to said rectifier being through said second terminal and a connection system including all of said means and adapted to be energized by direct or alternating current, a filter, a resistor, said filter being connected through said resistor to the output of said rectifier, said filter including an electrolytic condenser, and connections from the filter and anodes of said vacuum tubes, whereby a substantially constant potential is supplied either from said direct current or said alternating current source of potential, the destruction of said electrolytic condenser being prevented in case of incorrect poling of said source of direct current potential with said first and third terminals, by said resistance.

PAUL KAPTEYN.

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