________________________________ From: Tony Duell <ard at p850ug1.demon.co.uk> ? I am wondering just why this is a 'stupid suggestion'. Why won't fidding with the black level / offset and maybe the gain fo the green video amplifier in the monitor improve matters? -tony C: I have to say it's gratifying to have someone on the list that at the least has poked their head inside a monitor (evidently Gene has not). I am no expert on monitors, but I've at least the amount of experience to suggest, given I properly understanding the op, this might be the easiest way by far to remedy the situation. Actually, and it's been a long time, I had thought there would be a single trimpot to adjust the "green level". But like I said it's been a long time.

On 16 Jul 2012 at 20:15, Chris Tofu wrote: Well, I can think of a possible explanation. See, for example, the waveforms in this Maxim app note about creating SOG from discrete green and sync inputs: http://www.maxim-ic.com/app-notes/index.mvp/id/4116 Note that the sync pulse creates a "sub-black" level. If the monitor is capacitively coupled, this could create a false black "floor". A sync separator could be used to clamp the SOG green level during this period to 0V, eliminating the fake green floor. Just a guess... --Chuck

On 16 Jul 2012 at 21:03, Chris Tofu wrote: Yes, but VGA has separate sync. When you combine sync with a video signal on the same line, sub-black is usually the way it's done. As far as I know. --Chuck

________________________________ From: Tony Duell <ard at p850ug1.demon.co.uk> Sync-on-green means that the green video signal actually looks like a composite video signal, the sync pulses are 'blacker than black' (they ahve a voltage level below the black level). if the monitor is poorly designed, then the circuit may well take the bottom of the sync signal as the black level (being the lowest voltge on that input), so when the input is at the real black level the montiro displays a dim green. - ?C: the essence of what Chuckers said. Makes sense now, sort of. Like I said though, I have in the past added sync signals to the green line w/a haphazardly selected resistor. Never had a problem. But these were Sony monitors, monsters in their day, so I'll assume they were designed well enough that something like that wouldn't be a problem. Still have a couple of those monitors (16" actual diagonal). One 48khz, one 64khz. They say HP, but Sony made them.

________________________________ From: Chuck Guzis <cclist at sydex.com> On 17 Jul 2012 at 18:40, Chris Tofu wrote: Chrissy, I'd rather you not refer to me that way.? I find it denigrating. --Chuck C: Ok you big baby. I can't see what's denigrating about it though. Years ago, when I was less mature LOL, I frequented a chat room where everyone added -er to someone's name. Of course I needed to find some way to embellish even that. I have to imagine though that if we dug deep into your childhood, we'd find some deep dark secret associated w/the usage of Chuck***. LMHO

From: Tony Duell <ard at p850ug1.demon.co.uk> Hang on... The other day you called me a 'moron' I think... You can't have it both ways :-) I was working on monitors ebfore this list even existed. And I shall continue to do so. I don;t believe there's any reason not to, the dangers are much exagerated. In fact the most dangerous voltage you'll meet is the mains (and possibly rectified mains), something you find in many other devices too. I guess the fact that they're mostly analogue circuitry puts some people off, but much of it is not that complicated. It depends on the monitor. You need to be able to control the gain and offset (black level) of each colour to get both the highlights and lowlights a neutral grey. Some monitors, particularly the better ones, have 6 presets for this In other cases, one of the presets is not there, in that you can get the right effect using the 5 you do have. Be warned that the official procedure for settign these controls is often involved. Both HP and Barco seem to require the use fo a photomter, something that few people own (I don't have one). But if you're just going for 'it looks OK' then it's not hard to tweak them. Just don't have excessive beam current (brightness) to avoid damage to the CRT and maybe the high voltage supply components (flyback transofrmer, horizontal output transistor, etc). -tony

Ah, OK... I didn't rememrb that you were sharing this monitor. Have you tried it without the KVM switchj, just temporarily, in case that's messing about with the signal? I suppose you coudl add extra presets inside the monitor with relays to switch in either hte origianl or new set depending on which grey scale you want, but that _is_ a bit silly... Be casreful. Most such circuits (based on the LM1881 or improved versions thereof) simply extract the sync signals from the Sync-on-green composite signal, but leave the signal unchaged to be fed to the green input of the monitor. They do not clip off the sync signals and thus leave a green video signal where the most -ve value is the black level. If that's the case with the circuit you are using, it will nto make much (if any) difference. -tony

On Wed, 18 Jul 2012, Cameron Kaiser wrote: Unintended resistance/impedance and capacitance?

On Tue, 17 Jul 2012, Tony Duell wrote: Why not? Is poking on's head inside a monitor mutually exclusive with being a moron? NB: Tony is not a moron. But he knows more about monitors, computers, and electronics in general than anybody else that I know. OK I'll stick my head back into one