Abstract: A synchronizing pulse separator for a video apparatus provides horizontal and vertical synchronizing pulses from a composite video signal. The sync separator incorporates a compensation circuit that achieves noise immune operation with composite video signals that provide progressive field display and consequently lack synchronization equalizing pulses. The compensation circuit maintains a sufficient bias level on the sync separator transistor during the vertical blanking interval to prevent premature triggering of the vertical deflection circuit due to noise.

Abstract: A degaussing circuit for a video display apparatus eliminates residual degaussing current flow during operation of the video display apparatus. A capacitor is connected between coil of the degaussing relay and the source of energizing voltage. Application of the energizing voltage to the relay coil energizes the relay and initiates degaussing of the cathode ray tube of the video display apparatus, and also causes the capacitor to begin charging. As the capacitor becomes charged, the degaussing relay becomes deenergized, thereby terminating degaussing current flow. The capacitor charging time constant is selected to allow sufficient time for degaussing to occur before deenergization of the degaussing relay.

Abstract: A power supply for a video display apparatus includes circuitry that produces a pulse width modulated signal in response to the selected horizontal deflection rate. The pulse width modulated signal controls the switching of an FET through a transformer to provide a load circuit operating voltage representative of the deflection frequency. A turn-off signal for the FET is provided to a turn-off transistor from the primary winding of the transformer to insure rapid turn off of the FET.

Abstract: In a video display apparatus, the high voltage generating circuitry responds to trigger pulses derived from horizontal deflection retrace-related pulses. During normal horizontal deflection operation, the trigger pulses produced are of sufficient amplitude to cause normal triggering of the high voltage generating circuits resulting in normal high voltage levels being produced. Under abnormal horizontal deflection operation in which the horizontal deflection current is not produced, the trigger pulses will be of insufficient amplitude to trigger the high voltage generating circuit, and hence no high voltage level is produced.

Abstract: A switched mode power supply for a video apparatus having an electrically isolated chassis incorporates a switching FET that has its conduction interval controlled by pulses of varying frequency. An inductor is connected between the FET and hot ground to provide a low impedance path for line conducted interference signals generated by the switching of the FET and to provide a sufficient impedance path to prevent damage to the FET due to current flow caused by a high voltage discharge, such as a lighting strike to the cold ground referenced antenna.

Abstract: A video display apparatus includes a protection circuit for preventing damage due to the application of excessively high line voltage. The video display apparatus includes a start-up circuit that provides power to initiate operation of a switching voltage regulator. In response to an improperly high line voltage, the start-up circuit is disabled and the video display apparatus does not become operative.

Abstract: A vertical deflection circuit for a video display apparatus includes a service switch that collapses vertical or field rate scan in order to facilitate adjustment of cathodes ray tube electron beam drive levels. The service switch operates by referencing the vertical sawtooth signal generator, the AC feedback, and the DC feedback to ground potential so that no input is applied to the vertical drive circuitry.

Abstract: A power supply for a video apparatus includes a transformer incorporating windings that supply power to load circuits. A primary side winding provides power to the power supply regulator circuit. In the event a fault occurs in one of the load circuits and insufficient voltage is developed to power the regulator control circuitry, a protection circuit disables the regulator control circuitry in order to prevent damage to the power supply regulator switching transistor. The protection circuit operates within a wide range of input voltage with little power dissipation.

Abstract: A synchronizing circuit for a video display apparatus provides inputs for a composite sync signal or separate horizontal and vertical sync signals. The composite sync signal and the separate horizontal sync signal are applied to a sync separator that provides horizontal and vertical sync pulses in response to a composite sync input or horizontal sync pulses in response to a separate horizontal sync input. The separate vertical sync input is caused to bypass the sync separator. The bypass circuitry provides that the separate vertical sync input will take precedence over the separated vertical sync pulses of a composite sync signal in the event both signals are present.

Abstract: A mounting and retaining assembly for a degaussing coil and ground strap for use on a cathode ray tube includes a flexible wire form that is held in place by the tube tension band. The wire is bent to form separate regions that receive the degaussing coil and ground strap. When the degaussing coil and ground strap are in place, the wire is under tension which holds the degaussing coil and ground strap firmly against the rear surface of the tube. The mounting and retaining assembly also includes retaining clips that cooperate and are held in place by the tube mounting lugs. The clips incorporate retaining loops that also receive and retain the degaussing coil and ground strap at other points.

Abstract: A deflection yoke for a video display system incorporates an arrangement for the introduction and distribution of adhesive to effect assembly of the yoke and mounting of the yoke to a cathode ray tube. A single adhesive inlet location transports adhesive through delivery channels to various locations about the deflection yoke to fix the relative positions of the horizontal and vertical deflection coils as well as mounting the yoke to a cathode ray tube.

Abstract: A video display apparatus includes a diode modulator for correcting side pincushion raster distortion. The diode modulator drive circuit produces a vertical deflection rate parabolic voltage that modulates the horizontal deflection current to effect pincushion correction. The drive circuit includes a transistor that has its base bias established by the combination of a width control resistor and a diode. The diode has the same thermal characteristics as the transistor to provide accurate temperature compensation. A resistor is connected between the emitter of the transistor and a supply voltage to change the transistor bias point in order to enable the transistor to be cutoff.

Abstract: A regulating power supply for a video display apparatus includes a switching transistor that periodically energizes a transformer winding. Input switching pulses for the transistor are varied in width and frequency to optimize power transfer via the transformer. The charge and discharge rates of a capacitor determine the pulse width and frequency. The capacitor charging current is selectively switched to be connected to the capacitor while the capacitor discharge current is controlled in response to a feedback signal derived from the regulated voltage level.

Abstract: A progressive scan video display apparatus incorporates beam landing error correction circuitry. Beam landing error correction may be accomplished prior or subsequent to video information interpolation and prior or subsequent to video information speedup. The correction circuits utilize sample interpolation techniques to provide accurate beam landing error correction for each of the red, green and blue video information signals.

Abstract: A regulating switched mode power supply for a video display apparatus provides electrical isolation between the load circuits and the AC line. A power transformer incorporates a regulator winding referenced to AC line ground potential. First and second feedback circuits develop first and second feedback signal components that are applied to a regulator control circuit which controls the conduction of the power supply switching transistor. The two feedback circuits have different time constants to accurately monitor load circuit loading conditions in order to maintain load circuit voltage level regulation.

Abstract: A video display apparatus incorporates a start-up and control circuit that is responsive to a bilevel signal indicative of the desired operating state of the video display apparatus. One state of the bilevel signal is effective to permit operation of the horizontal deflection circuitry and to generate a gating pulse for a voltage regulator circuit. The other state of the bilevel signal disables the horizontal deflection circuit which in turn disables the video display apparatus load circuits.

Abstract: A raster distortion corrector for a cathode ray tube includes magnetically permeable corrector pieces that are located on opposite sides of the deflection yoke. A part of each corrector piece is located within the external field of the vertical deflection coils and presents a low reluctance path to the external field flux. The flux is directed via a flux channelling arm of each corrector piece to a field shaper that causes a distortion correcting field to be formed between the corrector pieces. The flux channelling arms are formed and located so that there is no significant interaction of the corrector pieces with the horizontal deflection field.