RGB-VGA Converter -- buy or build?

----- Original Message ----- From: <liste(a)artware.qc.caTo: <classiccmp(a)classiccmp.orgSent: Thursday, February 08, 2001 1:20 PM Subject: Re: RGB-VGA Converter -- buy or build? monitor. Sync-on-Green and VGA, as far as I know, shouldn't appear in the same clause (except for this type of clause) since it's like saying it's a black shade of white or a round square. They are VERY different. Until you KNOW, absolutely, what the frequency requirements are, and that you can't get a proper replacement monitor at the junkyard, I think your efforts would be best spent trying to get a schematic of the video adapter circuit. I've tossed out several very nice large fixed frequency monitors after trying to give them away, simply because nobody wanted either to come and get them or pay the shipping costs. I think this is a natural consequence of chosing to center your hobby around these formerly VERY costly systems, carefully designed to prevent you from using another vendor's hardware in case it might cost less. If you find a compatible monitor, it's unlikely it will cost more than $50, in addition to the cost of shipping. You can produce a separate, ttl-compatible composite sync easily enough, but the fact that it's a composite sync (with horizontal and vertical sync combined in the same signal) means that you'll need to separate the signals it might seem, and I've normally gone back into the video adapter circuitry to look for suitable timing, which, due to the current tendency to integrate everything into a single LSI, tends to be more difficult these days. In systems that were designed to be used with sync-on-green monitors, the DAC normally had the capability to put the negative-going sync pulses right on the green video signal was common. You should be able to handle that with software. However, if you don't know the DAC or other circuitry because it's all stock-numbered, you may be up the proverbial creek, and even more so if the DAC is internal to the LSI. Dick > -Philip