keith@reed.UUCP (Keith Packard) (01/18/86)
A number of people have been wondering about hooking up their ST to a non-Atari RGB monitor. I have successfully done this, with little difficulty. Since I was unable to locate one of those strange connectors used for the video, I opened my box and found the necessary signals readily accessible. Directly behind the video connector inside are 3 rows of pads, with each of the 3 rows tied together (for whatever reason). Each row has the R, G, B, VSync and Hsync signals. Unfortunately I can't seem to find the layout, but it's pretty easy to trace. Also, there is no ground on the pads, so you'll need to grab it elsewhere. The pads are on .1 centers, so you can use BERG pins and a harmonica connector with ribbon cable to bring it out. There is some blank space between the pins, so it looks (as I recall) like: OOO O OO or thereabouts. The monitor I used was a BARCO GD33 analog RGB. It required composite sync, so I tied the Hsync and Vsync together through 330 ohm resistors to achieve this. Also there is no audio on this monitor, so for now I'm doing without till I kludge something together. I imagine most medium resolution analog RBG monitors should work without much trouble. As far as also being able to use the monochrome monitor, no real problem there. A signal (grounded Monochrome Detect) from the mono monitor signals the ST to go with monochrome. The RGB can remain hooked up, but the RGB signals are turned off resulting in a blank screen. To use color, just unplug the mono monitor cable and reboot. Note the RGB signals have a peak amplitude of about 1.7 volts, while the sync (as I recall) is TTL. A local group is developing a RGB to color composite video converter. It was demoed at a recent user'g group meeting and seemed to work fairly well. I have a composite to RGB converter I use with my Atari 800, and as a TV monitor, which works very well. I suspect it would work well with the ST color monitor too. If I can ever track down the Atari video connectors, I may build some boxes based on the board I am using. Or sell the board seperately. Either video conversion is expected to run about $100-125. Since I can't post news to the net directly for the moment, please forward any questions or remarks to me at: Bob Ankeney tektronix!reed!omsi