Television apparatus having kinescope spot burn protection circuit with extended grid cut-off time constant

A grid bias control circuit for use with a kinescope, comprising:

• an input terminal coupled to a source of switched supply voltage and coupled via a pulse forming capacitor to an output terminal for producing at said output terminal a given positive grid bias voltage for said kinescope when said supply voltage is present and for producing a negative grid cut-off bias pulse at said output terminal upon termination of said supply voltage for blanking said kinescope;
• a potential divider coupled between said input terminal and a source of ground potential and having an output for providing said given positive grid bias voltage when said supply voltage is present and a ground level voltage upon said termination of said supply voltage;
• a transistor having a conduction path coupled between said output of said potential divider and said output terminal of said grid bias control circuit, said transistor having a control electrode coupled to said source of ground potential;
• and wherein
• said grid bias control circuit having no discharge path, other than leakage paths, for said pulse forming capacitor.