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Control grid should be negative (usually in the -50V to -75V range). Refer to the schematic for correct value. If control grid isn't sufficiently negative the osc is dead or it's signal isn't getting to the output tube.
Screen grid should be positive in the 75 to 200V range. Again refer to schematic.
Part of me wonders if you have the two mixed up.... regardless it looks like you're missing horizontal oscillator signal and or the osc isn't working.
If the screen grid is truly negative like that it means that the damper, flyback fuse or flyback is open. The screen grid voltage drops below spec when the plate isn't drawing current and the screen acts as a stand in plate...If it has dropped that low then the screen current is dangerously high and the tube may already be damaged. It could possibly get that low if there's no osc signal at the grid and the plate is not drawing current from an open circuit.
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