GB1143006A - Improvements in or relating to electronic tubes - Google Patents

Abstract

1,143,006. Cathode ray tube circuits. MULLARD Ltd. 31 March, 1967 [19 May, 1966], No. 22422/66. Heading H4T. [Also in Divisions H1 and H2] In an electric discharge device, e.g. a television C.R.T., in which an envelope containing electrodes has an external array of contact pins for at least some of the electrodes, a metal ring or ring segment 6 is provided which passes close to at least three of the contact pins to form a number of air spark gaps 8 therewith, the ring or ring segment being electrically connected to an additional pin 7. Preferably contact pins 1-5 are in a circular array and ring 6 is disposed concentrically about them such that each gap is, for example, 0À5 mm. wide to give a breakdown voltage of 2¢ kV., which voltage is less than the normal maximum operating potential difference of about 20 kV. between the final anode and control grid but is sufficient to withstand potentials applied to electrodes other than the final anode. If, in a television C.R.T., interval and external conductive coatings on the envelope are employed as the electrodes of an E.H.T. smoothing capacitor the ring should be connected to the external coating. Large resistances should also be connected in series between the electrodes and external circuitry to speed ignition of the spark gaps and afford some protection for the circutry during the flashover.