On Fri, 15 Jan 2016, martin.heppe...@dlr.de wrote: > I have got a HP 9000/217 machine with a standard video card. This card > has a monochrome composite output (resolution is as low as about > 512x400, but I might replace it with a higher resolution card). A > small 9" HP monitor that I used for testing only shows me 2 or 3 bands > of the image and cannot capture the signal properly. > > All I have are modern TFT monitors which usually have VGA and/or DVI > inputs, no separate R-G-B or monochrome jacks. > > What is the preferred way to connect "old" composite video signals to > a modern TFT monitor without losing too much sharpness? I understand > that interpolation is an unavoidable problem.
I don't know what the preferred way is, but as long as voltage levels are compatible (which I suppose could be tweaked with some circuitry anyway) you might be able to track down a standard VGA monitor that does sync on green and also has an option to switch to the greyscale mode. That's what I've been doing with a TURBOchannel MX monochrome graphics adapter which outputs an analogue composite 1V p-p signal (0.7V video, 0.3V sync), 1280x1024@72Hz, on a TNC connector (the adapter is a pile of weirdness of its own BTW). I have wired it via a TNC to BNC adapter and then a 5xBNC to DE-15 adapter (both off the shelf) to the green input of the monitor (obviously 4 of the 5 BNC inputs are loose), and in monitor configuration I chose the greyscale mode with input from the green line. It works just fine, and obviously there's no interpolation involved as the monitor simply applies the single signal to all the three colour components. It seems that with the switch to LCD panels sync on green support has become more common than it used to be with CRT displays; I don't know if this has to do with input circuitry commonly used with them or is it just that I've been lucky though. If you were happy with a green rather than white image (which would certainly add spice to the vintage look of the system, as a green phosphor was not uncommon in the old days), then any sync-on-green display should do. HTH, Maciej