US2179111A - Cathode ray tube circuit - Google Patents

Cathode ray tube circuit Download PDF

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Publication number
US2179111A
US2179111A US7736A US773635A US2179111A US 2179111 A US2179111 A US 2179111A US 7736 A US7736 A US 7736A US 773635 A US773635 A US 773635A US 2179111 A US2179111 A US 2179111A
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United States
Prior art keywords
valve
cathode ray
anode
grid
tube
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Expired - Lifetime
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US7736A
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English (en)
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Young Arthur James
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RCA Corp
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RCA Corp
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Publication date
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/52—Arrangements for controlling intensity of ray or beam, e.g. for modulation

Definitions

  • This invention relates to cathode ray tube circuitarrangements and more specifically to circuit arrangements embodying cathode ray tubes and wherein it is required that the cathode ray be modulated in intensity and the modulated ray caused to scan a predetermined area.
  • cathode ray tube television receivers wherein the received picture is built up upon a fluorescent screen at the end of the tube, it is required that the spot of light caused by the incidence of the ray upon the screen be modulated in intensity in accordance with received signals and at the same time scan the said screen so as to build up a received picture in the Well known way.
  • the higher the anode voltage the less'the deflection caused by a given potential applied to the deflecting means, the result of modulating the cathode ray beam by varying the anode voltage only, is to produce an additional undesired modulation of the speed of movement of the scanning spot.
  • This effect is undesirable because the mean value of the modulating input may not be zero, whence it follows that the length of the scanning lines may not be constant.
  • An important object of the present invention is to meet the above mentioned diificulties and to provide an anode modulation system in which undesired modulati'onof scanning speed shall be substantially reduced or eliminated.
  • a cathode ray tube circuit arrangement comprises meansfor modulating anode voltage in the tube in dependence upon modulating potentials and means for simultaneously varying,also in dependence upon modulating potentials, the E. M. F.s applied to the deflector means provided for scanning purposes, the
  • Fig. 1 shows diagrammatically a circuit arrangement for applying operating potentials to a cathode ray tube (not shown)
  • Figs. 2 and 3 are valve characteristic curves relating to the apparatus of Fig. 1;
  • Fig. 4 shows. a modification of Fig. 1;
  • Fig. 5 shows a still further modification.
  • the cathode ray tube (not shown) intended to be employed in co-operation with circuit arrangements in accordance with this invention is assumed to be of the well known type comprising a cathode, a Wehnelt cylinder or like electrode adjacent said cathode, an apertured anode on the sideof the said Wehnelt cylinder remote from said cathode, and two mutually perpendicular pairs of electrostatic deflecting plates arranged in succession along themean' path of the cathode ray; the tube having-a gasfilled envelope with a fluorescent screen at its end as in the usual way. It is assumed that'the tube is to be employed for reconstructing received television pictures.
  • a thermionic valve V1 shown as of the pentode type.
  • the valve V1 is provided with an indirectly heated cathode 2, a control grid 3, a screen grid 3, a suppressor grid 5 and an anode t.
  • the anode 6 is connected through a resistance R1 to a point i upon apotentiometer resistance which is connected between the positive and negative terminals of asource of high tension potential.
  • a by-pass condenser 8 is so arranged that one terminal is connected to the point I and the other terminal to earth.
  • a variable tapping point 9 upon the resistance R1 is connected to a resistance R2 across which are applied potentials-from a suitable electrical time base circuit (not shown) which is connected to terminals iii and may be, for example, a periodic generator of the electric gas discharge type.
  • a variable tapping point it upon the resistance R2 is connected to the control grid l2 of a further thermionic valve V2 also of the pentode type.
  • This valve V2 in addition to the control grid 12, is provided with an indirectly heated cathode l3, a screen grid M, a suppressor grid I5, and an anode H3.
  • the valve V2 is preferably of the so-called variable mu type.
  • the anode of the valve V2 is connected through a re-- sistance I"!
  • the bias of the valve V2 is determined by a battery or other source EG2 shunted by the condenser 28 which is inserted in a lead between the cathode E3 of the valve V2 and the anode 6 of the valve V1.
  • the valve V1 receives bias from a suitable source EG1 shunted by the condenser H9.
  • the valve V1 is biased to cut-ofi so that the anode current of this valve, and hence the voltage drop in resistance R1 will depend upon the signal input at terminals I, the said voltage drop across R1 being fluctuating direct current.
  • the source EG2 is of such value as to bias valve V2 normally to cut-off and this valve V2 is of such nature as to have a mutual conductance characteristic as shown by Fig. 3 of the drawings.
  • the input to the control grid of valve V2 is made up by a fixed direct current bias, a varying direct current bias in correspondence with the signal strength at the terminal points i and a time base signal derived from the apparatus connected at the terminal points it].
  • the effect of the varying direct current bias is to shift the operating point of the valve V2 from a point given by the line B of Fig. 3 to a point given by the line EVE! of the said Fig. 3.
  • the output from the valve V2 as set up across the resistance H is applied to one pair of electrostatic deflecting plates of the cathode ray tube (not shown), and it is to be understood that signals corresponding to those applied at terminals I and of suitable amplitude are also applied as in the manner usual in anode modulation schemes to the anode of the cathode ray tube, 1. e. between the anode and cathode thereof as shown in the above referred to patent to Kell.
  • an auxiliary high tension supply may be used in series in conjunction with the anode modulation voltage, being connectedin such manner that the changed sensitvity of the oscillograph due to the anode modulation is substantially compensated.
  • Fig. 2 of the drawings shows the characteristic of the valve V1, the line XX of the said Fig. 2 representing the point at which the said valve is operated
  • the valve now known under the trade designation RCA 41 is a suitable valve for the valve V1
  • the valve known under the trade designation RCA 58 is a suitable valve for the valve V2 and with these paiticular valves, screen grid voltages as indicated in Fig. 1, may be employed.
  • the parts of a circuit arrangement in accordance with this invention, to obtain a very high degree of modulation (theoretically 100%) without distortion, i. e. the modulation. may be arranged to be substantially rectilinear throughout; the cathode ray spot should not be displaced or defocused as a result of modulation; and a standard pattern of a cathode ray tube may be employed for receiving purposes in almost any known television system of the intensity modulation type Whether the transmitter be of the cathode ray tube or of the mechanical type.
  • valve V1 (which is shown as a pentdoe but may be a triode or a tetrode) is biased to cut off by means of voltage set up across a condenser 19' shunted by battery EG1, the input signals being applied across the terminal points I. Accordingly, there is developed across a resistance R1 in the oathode lead of the tube V1 a rectified component of the input voltage and a desired portion of this voltage is applied from tapping point 9 on the resistor R1 through resistance R2 to the control grid of a so-called variable mu valve V2.
  • the valve V2 has its gain controlled by the grid bias developed in the resistor R1.
  • valve V1 may be performed by a diode or some other form of rectifier e. g. a metal rectifier, and types of valves other than those illustrated may be employed for V2.
  • the rectifier at V1 is of rectilinear characteristic and the valve at V2 has a grid bias/mutual conductance characteristic which is rectilinear over the working range rectilinear correction-which is required for tubes employing electrostatic defiectionwill be obtained.
  • electro-magnetie deflection of the cathode ray beam is employed rectilinear correction will not be required but instead square law correction will be required and the described arrangements should be suitably modified.
  • the device V1 may be a square law detector and the device V2 a rectilinear amplifier (e. g. as already described) or the device V1 may be a rectilinear detector and the device V2 a valve-having a square law grid voltage/mutual conductance characteristic.
  • the use of electro-magnetic deflection is, however, not preferred in carrying out this invention owing to the difficulties introduced by reason of the high impedance which deflecting coils present at high frequencies.
  • the additional. modification illustrated by Fig. is a combined compensating device and time base unit.
  • a condenser C1 is charged from the source connected at HT+ and I-IT- through valve V2.
  • the valve V1 is a rectilinear rectifier which feeds to the control grid of V2 a voltage derived by rectifying picture signals applied at the terminal points I, this voltage being fed to the grid by reason of the provision of a common cathode resistance R1".
  • the charging current for condenser C1 will accordingly vary rectilinearly with the amplitude of the picture signals at the terminals I if the anode current/grid voltage characteristic of the tube V2 is rectilinear.
  • the sweep stroke of the cathode ray tube occurs during the charging of condenser C1.
  • the device V3 is a gas filled discharge device of the nature of that known under the registered trademark Thyratron. As will be seen from an inspection of the circuit the tube V3 has its grid maintained highly negative with respect to its cathode until the voltage across condenser C2 which is charged through resistance R4 rises to the ignition potential of the neon or other glow discharge device N which is in shunt with C2 whereupon said device glow tube N flashes.
  • a pair of valves arranged in a circuit as described in British patent specification No. 25,026 dated August 20, 1934, could be employed for the function of discharging the condenser and/or such an arrangement could be utilized instead of the device N in the auxiliary time base circuit.
  • Fig. 5 The operation of the accompanying Fig. 5 may be summed up as follows: Picture signals are supplied at terminal points I to a rectilinear rectifier V1 from which a part of the output is fed to the control electrode [2 of the valve V2.
  • the valve V2 has a rectilinear anode current/grid voltage characteristic and operates as a constant current device in the sense that it passes constant anode current assuming constant grid voltage.
  • the tube V2 may, for example, be a tetrode or a pentode.
  • the constant current tubevzserves to charge a condenser C1'whicl1 is periodically discharged under the control of an auxiliary time base circuit including the glow tube N, a shunting capacity C2 and a resistor R4, and this circuit may be synchronized from the picture signals in the usual way.
  • the control by the auxiliary time base circuit is effected by triggering a discharging device Va associated with the condenser C1.
  • Any combination of rectifier and amplifier devices at V1 and V2 other than the rectilinear rectifier and rectilinear amplifier combination described may be employed so long as the combination is such that the anode current of tube V2 varies rectilinearly with the signal amplitude at the terminal points I.
  • a cathode ray tube circuit arrangement wherein a cathode ray is modulated and caused to scan a predetermined area comprising, in combination, means for modulating the anode voltage of the cathode ray tube in accordance with modulating potentials, and means for simultaneously modulating the ray deflecting forces applied to said tube to cause scanning action of the ray therein in accordance with the modulating potentials, whereby scanning speed variation resultant upon the anode voltage modulation is substantially prevented by compensating modulation of the ray deflecting forces.
  • the arrangement claimed in claim 1, comprising, in addition, a multi-grid thermionic rectifier, means for applying the modulating potentials for producing anode modulation to the input electrode of said multi-grid thermionic rectifier, a multi-grid amplifying tube, means for applying the output energy from the rectifier to the input electrode of said multi-grid tube to vary the mutual conductance thereof, and means for controlling the deflecting forces in accordance with the output from said multi-grid amplifier tube.
  • the system claimed in claim 1 and comprising in addition a multi-grid thermionic rectifier having an anode and a cathode, an input and an output circuit, means for applying modulating potentials to the input circuit of said rectifier, a multi-grid thermionic rectifier having an input and output circuit, means for applying energy from the output circuit of said rectifier to the input circuit of said amplifier, an impedance connected between the cathode of the rectifier and a source of anode potential therefor, a second impedance connected to at least a portion of said first named impedance and connected to the input circuit of said amplifier, and means for supplying across said second named impedance voltages for causing deflection of the said cathode ray.
  • An anode voltage modulated cathode ray system comprising means for simultaneously modulating the anode voltage and varying the deflection sensitivity of the cathode ray in accordance with signal energy, and thermionic control means kind wherein a cathode ray is caused to scan a predetermined area which comprises means for modulating the anode voltage of the cathode ray tube in dependence upon modulating potentials, and means for simultaneously varying, also in dependence upon modulating potentials, the ray deflecting forces applied to said tube to cause scanning action of the ray therein, whereby scanning speed variation resultant upon anode voltage moduation is prevented.
  • the arrangement as claimed in claim 6 comprising in addition, a rectifier, means for applying the modulating potentials for producing anode modulation-to the input circuit of the rectifier, an amplifier, and means for supplying the rectifier output to the amplifier to control the gain thereof whereby a deflecting force for defiecting the cathode ray in a coordinate scanning direction is derived from the amplifier output.

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  • Geophysics And Detection Of Objects (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Details Of Television Scanning (AREA)
US7736A 1934-02-23 1935-02-23 Cathode ray tube circuit Expired - Lifetime US2179111A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB6034/34A GB434199A (en) 1934-02-23 1934-02-23 Improvements in or relating to cathode ray tube circuit arrangements

Publications (1)

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US2179111A true US2179111A (en) 1939-11-07

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US (1) US2179111A (enrdf_load_stackoverflow)
BE (1) BE408025A (enrdf_load_stackoverflow)
FR (1) FR786030A (enrdf_load_stackoverflow)
GB (1) GB434199A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2438717A (en) * 1943-05-28 1948-03-30 Du Mont Allen B Lab Inc Beam switch for single trace observance
US2448771A (en) * 1943-09-23 1948-09-07 Du Mont Allen B Lab Inc Cathode-ray oscillograph circuit
US2569289A (en) * 1945-08-31 1951-09-25 Rca Corp Automatic gain control system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2438717A (en) * 1943-05-28 1948-03-30 Du Mont Allen B Lab Inc Beam switch for single trace observance
US2448771A (en) * 1943-09-23 1948-09-07 Du Mont Allen B Lab Inc Cathode-ray oscillograph circuit
US2569289A (en) * 1945-08-31 1951-09-25 Rca Corp Automatic gain control system

Also Published As

Publication number Publication date
FR786030A (fr) 1935-08-24
GB434199A (en) 1935-08-23
BE408025A (enrdf_load_stackoverflow)

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