Apparatus and method for spot-knocking television picture tube electron guns

A spot-knocking apparatus for an electron gun enclosed in the evacuated envelope of a cathode ray picture tube, said apparatus inducing beneficial arcing between selected electrodes of said gun, said envelope including a base, a neck, a funnel having a feed-through conductor for conducting a high voltage to a conductive coating deposited on an inner surface thereof, and a faceplate with a luminescing screen, said electron gun projecting at least one electron beam on said screen, said gun having a first electrode proximate to said faceplate and connected to said conductive coating, a third electrode proximate to said base connected to a second lead-in pin through said base, and a second electrode between said first and third electrodes connected to a first lead-in pin, said picture tube having an inherent capacitance that can store energy in an amount capable of supporting a destructive arc during said spot-knocking, said spot-knocking apparatus comprising:

• a first high-voltage source connected to said feed-through conductor for supplying a first potential to said first electrode, said first source providing a first potential having a value at least long-term average which is many kilovolts positive relative to a predetermined ground:
• a second high-voltage source connected to said first lead-in pin for supplying a second potential to said second electrode through a series-connected first resistor nearest said lead-in pin and a second resistor, said second potential having a value at least long-term average which is many kilovolts negative relative to said ground, the difference between said first and second potentials being such as to induce beneficial arcing between said electroes;
• capacitive means connected between said ground and said second lead-in pin leading to said third electrode, and to a point between said first and second resistors;
• and,
• spark-gap means in parallel connection with said first resistor;
• whereby, by the application of the bipolar potential across said electrodes, the amount of energy in the induced arcing, for a given applied potential, is very much less than would be the case if a unipolar potential were applied;
• and whereby said spark gap means provides for discharging the voltage between said lead-in pins before a destructive arc can occur therebetween.

A spot-knocking apparatus for an electron gun enclosed in the evacuated envelope of a cathode ray tube, said apparatus inducing beneficial spot-knocking arcing between selected electrodes of said gun, said evacuated envelope including a base, a neck, a funnel having a feed-through conductor for conducting a high-voltage to a conductive coating deposited on an inner surface thereof, and a faceplate with a luminescing screen, said electron gun projecting at least one electron beam on said screen, said gun having a first electrode proximate to said faceplate and connected to said conductive coating, a third electrode proximate to said base connected to a second lead-in pin through said base, and a second electrode between said first and third electrodes connected to a first lead-in pin, said picture tube having an inherent capacitance that can store energy in an amount capable of supporting a destructive arc during said spot-knocking, said spot-knocking apparatus comprising:

• a high-voltage source connected to said feed-through conductor for providing a potential to said first electrode, said potential having a value at least long-term average that is many kilovolts positive relative to a predetermined ground;
• a first resistor and a second resistor series-connected between said first lead-in pin leading to said second electrode and said ground, said first resistor being nearest said first lead-in pin;
• capacitive means connected between said ground and said second lead-in pin leading to said third electrode, and to a point between said first and second resistors;
• spark gap means in parallel connection with said first resistor;
• whereby, the difference in potential between said electrodes is such as to induce beneficial arcing between said electrodes, and whereby said spark gap means provides for discharging the voltage between said lead-in pins before a destructive arc can occur therebetween.

A method for spot-knocking an electron gun enclosed in the evacuated envelope of a cathode ray picture tube by inducing beneficial arcing between selected electrodes of said gun, said evacuated envelope including a base, a neck, a funnel having a feed-through conductor for conducting a high-voltage to a conductive coating deposited on an inner surface thereof, and a faceplate with a luminescing screen, said gun having a first electrode proximate to said faceplate and connected to said conductive coating, a third electrode proximate to said base connected to a second lead-in pin through said base, and a second electrode between said first and third electrode connected to a first lead-in pin, and wherein said picture tube has an inherent capacitance that can store energy in an amount capable of supporting a destructive arc during said spot-knocking, the method comprising:

• applying a first potential to said first electrode through said feed-through conductor, said potential having a value at least long-term average which is many kilovolts positive relative to a reference potential;
• applying a second potential to said second electrode through said first lead-in pin through a series-connected first resistor nearest said lead-in pin and a second resistor connected to the source of said second potential, said potential having a value at least long-term average which is many kilovolts negative relative to said first potential, the difference between said first and second potentials being such as to induce said beneficial arcing between said electrodes;
• connecting said second lead-in pin to a point between said first and second resistors, and to a ground through capacitive means;
• discharging the voltage across said first and second lead-in pins before a destructive arc can occur therebetween.

A method for spot-knocking an electron gun enclosed in the evacuated envelope of a cathode ray picture tube by inducing benefical arcing between selected electrodes of said gun, said evacuated envelope including a base, a neck, a funnel having a feed-through conductor for conducting a high-voltage to a conductive coating deposited on an inner surface thereof, and a faceplate with a luminescing screen, said gun having a first electrode proximate to said faceplate and connected to said conductive coating, a third electrode proximate to said base connected to a second lead-in pin through said base, and a second electrode between said first and third electrode connected to a first lead-in pin, and wherein said picture tube has an inherent capacitance that can store energy in an amount capable of supporting a destructive arc during said spot-knocking, the method comprising:

• applying a first potential to said first electrode through said feed-through conductor, said potential having a value at least long-term average which is many kilovolts positive relative to a predetermined ground;
• applying a second potential to said second electrode by way of said first lead-in pin through a series-connected first resistor nearest said lead-in pin and a second resistor connected to the source of said second potential, said potential having a value at least long-term average which is many kilovolts negative relative to said ground, the difference between said first and second potentials being such as to induce said beneficial arcing between said electrodes;
• connecting said second pin to a point between said first and second resistors, and to said ground through capacitive means;
• discharging the voltage across said first and second lead-in pins before a destructive arc can occur therebetween;
• whereby, by the application of the bipolar potential across said electrodes, the amount of energy in the induced arcing, for a given applied potential, is very much less than would be the case if a bipolar potential were applied;
• and destructive arcing between said pins is prevented.

A method for spot-knocking a three-beam, unitized, extended field lens electron gun enclosed in the evacuated envelope of a cathode ray picture tube having a resistive arc-suppression zone and static elimination system, said envelope including a base, a neck, a funnel having a feed-through conductor for conducting a high voltage to an inner conductive coating deposited on said funnel, and a faceplate with a luminescing screen, said gun being located in said neck and having discrete electrodes connected to lead-in pins extending through said base, said gun having lower-end electrodes proximate said base including heater and cathode electrodes, and first and second prefocus electrodes;

• and upper-end main focus lens third, fourth, fifth and sixth electrodes proximate said faceplate, with said third and fifth electrodes electrically inter-connected internal to said envelope and connected to a first lead-in pin, with said sixth electrode connected to said inner conductive coating through said resistive arc-suppression means, and wherein said picture tube has an inherent capacitance that can store energy in an amount capable of supporting a destructive arc during said spot-knocking, the method comprising:
• applying a first potential to said sixth electrode through a resistor, an on/off switch, and said feed-through conductor, said potential having a value at least long-term average which is many kilovolts positive relative to a predetermined ground;
• applying a second potential to said interconnected third and fifth electrodes by way of said first lead-in pin and through a first resistor nearest said pin and a second resistor connected in series between said second lead-in pin and the source of said potential, said second potential having a value at least long-term average which is many kilovolts negative relative to said ground;
• interconnecting the lead-in pins of said lower-end electrodes and said fourth main focus lens electrode, and connecting said interconnected pins to said ground by way of a capacitor, and to a point between said first resistor and said second resistor;
• applying said second potential while cyclically applying said first potential and adjusting said first potential to provide a difference between said potentials effective to induce beneficial arcing between said electrodes;
• discharging the voltage across said first lead-in pin and said inter-connected pins before a destructive arc can occur therebetween;
• whereby, by the application of the bipolar potential across said electrodes, the amount of energy in the induced arcing, for a given applied potential, is very much less than would be the case if a unipolar potential were applied and whereby destructive arcing between said lead-in pins is prevented, and the total potential across the electrodes to be spot-knocked is at a level high enough to overcome the resistance of said arc-suppression means.