[Coco] GBS-8200 RGB to VGA

[Barry Nelson]

You could try using the chip below. It extracts just the sync signal from a composite video line.

http://www.ti.com/lit/ds/symlink/lm1881.pdf
George Ramsower georgera at gvtc.com 
Wed Sep 2 21:38:30 EDT 2015
I wired it almost exactly as each wire is designated except for the 
Horizontal line. I cheated and used the video output from the coco to 
steal a proper H sync from. However, in OS9, I had to use "Montype M" to 
turn off the color burst because it was messing with the sync in the 80 
column mode. 32 and 40 were fine. When I feel like it, I'll put a proper 
7402 chip in line with the H sync line from the coco to invert that 
signal. Gene Heskett thinks he may have used a 7406 which does the same 
thing but for more power on the output.
George R.