🚀 go-pugleaf

All You Video Hackers:

Recently, I posted a request for help converting a CGA RGB signal to a
video signal suitable for a Xerox 820-II screen.  The Xerox monitor has nice
white phosphor, and happens to run at the same sync frequency as IBM CGA.
Several people sent mail with helpful suggestions on how to combine the 
required signals.

What I ended up doing was hooking up 1K pots to the R, G, B, and I (intensity)
outputs to a common point with a 75 Ohm resistor to ground at the Xerox's 
video input.  Hsync and Vsync were hooked up separately.  Some quick math shows
that if the pots are set to 225 Ohms, each signal will be weighted equally, 
and if they're all on, it adds up to 5V (or whatever TTL really is).

This gives you a good signal with highlighting and low video for word
processing, and a reasonable gray scale for games (perhaps even more 
important).  If this combination doesn't work for a particular software 
package, you can always adjust the pots accordingly.  The G input seems to
have the greatest effect.

If anyone needs to know pinouts, etc, email me at the address below.

Thanks Again,

Dev Palmer
Duke University Electrical Engineering
wdp@dukee.egr.duke.edu
(919) 660-5283