Recently I found an arcade CRT monitor. It supports a range of frequencies between 15 to 25Khz. But it has a thing that I don't understand. This monitor have a connector for video in with these inputs signals : - Red - Green - Blue - GND - VS - HS or composite syncrho All jamma PCB that I have tested works fine and all of these are RGB+composite synchro. However when I try to hook up a video game console ( tried with AES Neogeo, Genesis, XBox and PAL Gamecube) the image is not synchronised. Yet, RGB on these consoles is also a composite synchro like arcade PCB. but maybe diferent... :shrug: I can obtain a image with a synchro separator. But this does not tell me why consoles synchro signals does not works with this monitor. Someone can explain me this strange thing ?
Video console (basically any TV signal) use 31 Khz (also known as high, 15 low, 25 med) then without converter it will not work.
You're wrong, all console output signal is 15Khz except when you output via vga connector (like dreamcast, xbox 360 etc ...)
Ohhh you're right its the other way around. You can't use computer on these monitors fi you don't have 31Khz.
Basically you are feeding the monitor Composite Video rather then Composite Sync, so obviously you aren't going to get anything. Consoles use Composite video rather then Composite Sync, so that any TV that doesn't support RGB will still display a picture (on most consoles), TVs will strip the sync out of the video signal. Blame the French as they invented SCART due to SECAM being useless. You will need a Sync Stripper. Look up LM-1881 anywhere to find a circuit to strip Composite Sync.
With the Xbox, you'll be doing extra work as well if you want VGA out of it. Three pairs of pins on the A/V header need to be closed, AND you have to have a VGA (hacked) BIOS running. I never did it myself, but you WILL have to run the green signal through an LM-1881 circuit (via a hacked together cable) to separate the sync signal from the green color signal. Your screen at that point might be a bit green tinted though (I believe the problem was not enough signal separation so it threw the monitor off a bit). I remember looking into taking the sync signals from as close to either the GPU or video encoder chip as possible, but my notes are long gone. *EDIT* Sorry for bringing topic from the dead...
