I always like it when a mystery is solved! As long as the screen is sufficiently negative to not attract electrons it won't affect the triodes, as all electrons will end up on the anode as they should. A very negative screen could at most discourage electrons from landing on the anode near the hole. A sufficiently positive screen will steal electrons, especially when the anode voltage is low. I suppose there will be some capacitive coupling to the screen too.
depends on the circuit:
when you powerup the tube, static voltage will elevate pin9 voltage to a point where the other cathode may conduct to pin9 (like a diode). Once you discharge it, it'll keep lower voltage, that will buld much slower or not att all than when powerup.
Always keep pin 9 to ground or a dc steady reference, and also reduce the chance for oscilating.
when you powerup the tube, static voltage will elevate pin9 voltage to a point where the other cathode may conduct to pin9 (like a diode). Once you discharge it, it'll keep lower voltage, that will buld much slower or not att all than when powerup.
Always keep pin 9 to ground or a dc steady reference, and also reduce the chance for oscilating.
Let us be clear: it is not pin 9 which needs to be grounded, but the shield/screen (if present) which may be connected to pin 9.
A quite separate issue is establishing a DC voltage reference for the heater, so the heater does not become another floating electrode within the valve. Using a capacitor is not sufficient for this, unless the capacitor is quite leaky.
A quite separate issue is establishing a DC voltage reference for the heater, so the heater does not become another floating electrode within the valve. Using a capacitor is not sufficient for this, unless the capacitor is quite leaky.
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