Abstract: A circuit which compensates for the effects of drift that occur during the operation of a cathode ray tube because of temperature changes or aging and which produces changes in intensity of the picture on the cathode ray tube by sensing the intensity changes and varying the bias on the second grid of the cathode ray tube to restore the desired intensity.

Abstract: A voltage at a control grid of a cathode ray tube is generated at a blanking level to provide beam current blanking when horizontal deflection loss occurs. The control grid voltage at the blanking level is developed in a capacitor prior to an instant in which the horizontal deflection loss occurs. When the capacitor voltage is applied to the control grid to provide the blanking level, the capacitor is discharged slowly. To maintain the capacitor charged, prior to such instant when horizontal deflection is lost, the capacitor voltage is not applied to the control grid as long as the horizontal deflection is normal, regardless of whether vertical deflection loss occurs. Either horizontal deflection loss or vertical deflection loss will disable a video driver stage that controls the cathode of the cathode ray tube for providing additional beam current blanking capability.

Abstract: A projection cathode ray tube burn protection circuit includes a buffer transistor supplied with a 60 Hz square wave signal from an optical coupler. A PNP and NPN combination of transistors full wave rectifiers the buffer output. The rectified signal is divided down to reduce the magnitude of the alternating current components therein and applied to the base of a switch transistor that is normally maintained in saturation for swamping out the alternating current components. The switch transistor drives a high voltage shut down transistor and a blank transistor for shutting down the high voltage generating system and for blanking the cathode ray tube, respectively, in the event the power input to the optical coupler is disrupted.

Abstract: A CRT phosphor burn protection arrangement has an RC delay circuit coupled between the power supply and the video amplifiers for maintaining B+ potential to the video amplifiers after turn off of the power supply. The video amplifiers drive the cathodes of the CRT. A capacitor is connected between the B+ terminal of the power supply and the common control grid of the CRT for driving the control grid in a negative direction upon turn off of the power supply. The combination of the CRT cathodes being maintained positive and the CRT control grid being driven more negative assures that the CRT is held in cutoff until potential phosphor burn producing energy in the CRT is dissipated.

Abstract: A shutdown circuit for a projection type CRT comprises a transistor switch for operating a relay, responsive to a turn-off signal, to immediately break the high B+ operating voltage connection to a horizontal deflection system. A switched mode power supply is supplied with the turn-off signal, after a delay caused by a resistance-capacitance circuit, for shutting down the low voltage drive voltage to the horizontal deflection system after occurrence of the turn-off signal.

Abstract: A transistor with its collector connected to a point near the screen grid in the resistor network which feeds voltage from the high voltage rectifier of a picture tube to the screen grid electrode and its emitter connected to ground has two control circuits connected to its base electrode. The first control circuit (56) is a threshold circuit responsive to a voltage proportional to the beam current of the picture tube for making the control transistor provide a short circuit between the picture tube screen grid and ground, and thereby preventing a burnout when there is persistent excessive beam current. The second control circuit (58) acts on the base electrode of the control transistor to set the screen grid voltage of the picture tube at a desired value in normal operation, for example in accordance with the pulse width of a train of pulses of settable pulse width.

Abstract: In a video camera, "shading ears" resulting from charge build-up beyond the ends of the scan lines of the normally scanned area of a camera tube target are eliminated by applying a voltage pulse to a lens electrode of the camera tube, the timing, amplitude, duration, and shape of the pulse being predetermined to extend the scan lines, and also to de-focus the electron beam.

Abstract: During the horizontal retrace scan period of a scanning beam in a television pickup tube, the beam current is increased to the maximum possible value to recharge the target layer, and the cathode voltage is raised by a few volts to prevent readout of normal video. Also, the scanning beam path may be modified to insure that every area of the image is scanned by the retrace scan prior to being scanned by the active picture scan.

Abstract: The picture tube of a television receiver includes, inter alia, a plurality of electrodes to develop and accelerate an electron beam, and a phosphor screen on which the electron beam impinges. A deflection generator is coupled to a deflection winding for generating scanning current to produce a sweep of the electron beam across the phosphor screen. A remote control circuit develops an on/off command signal for switching the television receiver between normal run and standby modes of operation. A first switch is responsive to the command signal and disables normal generation of the scanning current upon the occurrence of the off-state of the command signal to inhibit normal sweep of the electron beam.

Abstract: An article of manufacture is disclosed comprising a cathode ray tube having a glass face panel with a cathodoluminescent screen on the inner surface thereof. The screen has a phosphor constituent vulnerable to patterned discoloring known as character burn. Character burn is caused by static area electron bombardment of such time and intensity as to discolor the phosphor, but not appreciably degrade phosphor efficiency. The tube according to the invention is characterized by having a conditioned screen uniformly burn-discolored throughout at least in the visible portion of the screen to render substantially imperceptible patterned character burn resulting from use. A process is also disclosed for use in the manufacture of cathode ray tubes and display monitors, and the reclamation of character-burned cathode ray tubes to render character burn substantially imperceptible.

Abstract: In projection television apparatus in order to prevent burning of the phosphor screen of at least one of the television projection tubes a display is not produced should there be an interruption or substantial reduction in the deflection current through one of the line or field deflection coils. Each deflection coil is connected in series with sensing means for separately sensing the deflection current flowing therethrough. In the event of one of the currents through one of the deflection coils being interrupted or substantially reduced means responsive to said sensing means prevents picture information from being applied to the control grids of the projection tubes.

Abstract: An integratable CRT spot cut-off network is described for use in a television receiver. The network establishes a reference current for biasing up the receiver's G.sub.1 grid when the supply voltage comes up, and a bypass capacitor coupled to the grid charges toward the supply voltage. When the receiver is turned off, the network terminates the reference current as the supply voltage starts to collapse and prevents the bypass capacitor from discharging. The charge stored on the capacitor reverse biases the grid to cut off the receiver's beam current.

Abstract: A voltage buffering coupling circuit for coupling a ground-referenced control signal to a high voltage biased CRT includes all solid state elements, thereby avoiding the tendency of the arc breakdown characteristic of gaseous voltage regulator tubes. The circuits include temperature compensating elements of opposite thermal coefficient characteristics.

Abstract: A system for preventing CRT phosphor burn in a multiple CRT projection type television system is disclosed. The absence of an electron beam deflection signal in the deflection yoke of a CRT is detected and used to provide a signal to CRT shutdown circuitry by means of an unbalanced transformer approach in which the various deflection yoke signals energize a plurality of primary transformer coils with a shutdown signal provided by the transformer secondary when a primary coil flux unbalance occurs.

Abstract: A video amplifier circuit for a cathode ray tube in a video display includes an anti-spot burn protection system for preventing damage to the fluorescent screen when deflection voltages are removed as in tube turn-off. A diode network in the video amplifier circuit controls the rate of voltage decay on the CRT's cathode and brightness control grid following the removal of power, maintaining a pre-determined brightness control grid-cathode voltage differential thereby precluding tube turn-on.

Abstract: For the periodic suppression of the beam of a cathode-ray tube in a television receiver during flyback, in response to a blanking pulse V.sub.2 normally accompanied by a flyback pulse V.sub.1 of shorter duration, a control transistor T.sub.11 is saturated to render conductive a master transistor T.sub.7 in series therewith, together with several slave transistors T.sub.6, T.sub.8 and T.sub.13 forming current mirrors with transistor T.sub.7. Slave transistor T.sub.13 lies in series with a Zener diode DZ across which the beam-suppressing signal V.sub.3 is generated; slave transistor T.sub.6 activates a comparator CMP having an input A connected to a biasing circuit PL1 including slave transistor T.sub.8. Another input B of the comparator receives from a voltage divider PL2 a biasing voltage of such magnitude that an output C of the comparator feeds back a holding signal to another control transistor T.sub.12, in parallel with transistor T.sub.11, to maintain the conduction of master transistor T.sub.

Abstract: A spot killer circuit wherein when a power switch is turned off, a transistor interconnected between the first gird of a picture tube and a low voltage supply is driven into the cut-off region so that the first grid voltage may be abruptly raised so as to cause the discharge of the picture tube.

Abstract: A color picture display device having a circuit for generating a screen grid voltage derived from the line deflection generator, while the high tension generator is separated. Via a resistance element, the screen grid is coupled to a source which generates a parabolic voltage of the field frequency with a curvature opposite to that obtained by rectifying the line flyback pulses owing to the east-west modulation, the resistance element, for example a voltage-dependent resistor, having in operation, a dynamic resistance which is many times lower than the static resistance thereof.

Abstract: An improved circuit for suppressing the occurrence of a sharply-focused light spot on the screen of a television receiver when the set is turned off is described. A normally conductive, controllable electronic switch is normally effective to maintain the brightness control grid of the cathode ray tube blocked, such switch assuming its non-conductive state only during the presence of the normal forward sweep portion of the deflection voltage to impart a positive step in voltage to the control grid to permit the now-moving light spot to be visible on the screen. During the flyback portion of the deflection voltage, or equivalently during the disabling of the TV set so that no forward sweep voltage is present, the controllable switch reverts to its "fail-safe" conductive condition to immediately restore the negative blocking voltage on the control grid to inhibit the beam current and thereby the formation of the now-stationary light spot.

Abstract: An intensity control system for a cathode ray tube (CRT) is disclosed. The system provides precise intensity control for a CRT whose control characteristics are only slowly varying. Precise intensity control is provided by measuring the cathode ray tube beam current. The beam current is set at a desired value without producing an image on the tube face. Thus, tube intensity can be set without fogging photoresponsive media which is in position for exposure by images on the cathode ray tube screen. The intensity may be set to a value determined by a manually adjustable intensity control. The intensity is preferably set by iterative threshold comparison of the actual beam current with the value corresponding to the setting of the intensity control. A unique threshold comparison circuit provides precise comparison between the reference level set by the intensity control and the actual beam current.

Abstract: An amplifier for driving a color image reproducing device includes a first transistor the base of which is capacitively coupled to a source of color difference signals. The emitter of the first transistor is direct current coupled to the base of a second transistor. The collector of the second transistor is direct current coupled to the base of the first transistor. The emitter of the second transistor is coupled to a source of a predetermined voltage. The emitter of the first transistor is direct current coupled to the emitter of a third transistor of opposite conductivity type which serves as a luminance signal amplifier. The first and third transistors form a matrix amplifier operative to generate a color signal at the collector of the first transistor.

Abstract: The phosphor screen of a cathode ray tube (CRT) has its phosphor coating protected against damage caused by a stationary or low sweep velocity electron beam that strikes its surface, by removal of the video signal that controls the beam whenever there is a simultaneous presence of video signal and absence of a proper horizontal or vertical sweep signal.

Abstract: Both velocity and x-y deflection magnitude of a cathode ray tube (CRT) electron beam are continuously sensed, and beam intensity is limited to prevent damage to the CRT during periods of insufficient beam deflection.

Abstract: A video amplifier for driving an electron beam intensity controlling electrode of a cathode ray tube comprises at least one solid state high speed binary switch which is connected via a coupling capacitor to the controlling electrode while a D.C. restoration means eliminates the chance of any droop in D.C. level of the signal fed to the controlling electrode.

Abstract: A cathode ray tube device includes a cathode ray tube of which cathode is heated in a waiting state as well as a normal operating state to emit an electron beam. The emitted electron beam in the waiting state is prevented from impinging the fluorescent surface of the tube by supplying a predetermined voltage or current independent of a signal for the normal operation to the grid of an electron gun assembly or a deflecting device.

Abstract: An electron gun comprising a changeover chamber and changeover circuit between the gun chamber and the insulated cable which connects the power supply circuits to the electrodes which enables adjustment of electrode potentials to accomplish electrode treatment without excessive gun currents.