[Alex KL-1]

Just remembered something: I have a notebook with S-Video output, and it have almos all systems in vigence at it's time, so I believe that have NTSC-J (well, it have the PAL-M...). So, I need to check it. If have it, I will compare it with NTSC or PAL-M using my old B&W TV's tha't I've added DC clamping (using only Y signal from S-Video as usual for B&W).

I noticed for making a usable passive (not switched) DC clamping (eg. diode) I need a very large RC time constant, ie, for example, if I clamp at grid of video out tube, need to have some 1M and 560nF cap, or DC drifts fast with some scenes, making the restoration partial.

For some small B&W I clamped at base of video out, and needed at least 100µF for not tilting the DC level under certain conditions.

Then I assume that active (switched) clamping will be more stable with it, since it can be able to clamp at correct waveform position/time.

Oddly as it seems, some CRT monitors from last era in fact have simple DC restoration at the cathodes, and uses large time constant anyway. But it works good.