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I guess that I am a tweekoholic. As per the last post I had it working (almost) per spec.
But then I noticed that the video amp 6AC7 was working well beyond specs.
So I added two more Zener diodes (well, chains), one to regulates its B+ to 250 volts and one to regulate the screen to 85 volts.
This of course also adds thr reduction in B+ to the effective HV, which helps brightness a bit. Clamping the screen means that
since the black level set by the signal is clamped by the diode action at the 6AC7 grid its level at the plate (and CRT grif) is clamped too. This means full DC restoration
(at sync tip level, not black level of course. So now you can set black level and then the contrast more or less only adjusts the white level
(until it too gets clamped). The white clamp means I could remove the focus voltage clamp. So this tweek on average only adds one Zener chain.
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