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Studied the -9 schematic some more over the past few days, and made some realizations.
1. the video output tube is DC coupled to the CRT cathodes
2. the video output tube is AC coupled to the video amp tube via .1uf capacitor, with DC bias being set by the brightness control
3. between the amp and output is where the DC resto of the signal needs to happen
I going to be looking into this more in depth in the coming weeks, so if anyone has circuit specific input I'd love to hear it.
From what I've read, the black level must be reset before the beginning of each horizontal scanning line, and it's usually done during horizontal retrace. This is what makes the diode a bad choice, because it clamps the entire signal (including any sync pulses) to ground. What this means is that with a diode, the black level is being inluenced by the amplitude of the sync pulses, so you are not seeing 'true black'.
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