[Coco] CoCo2 black and gray video only -- need help!

[Kevin Becker]

On Sun, Oct 24, 2021, at 9:52 PM, Keith Monahan via Coco wrote:
> I have yet to find a service manual or associated schematic/BOM list for 
> a 26-3127B. If anyone knows where to find one? Color Computer Archive 
> does not seem to have it, but maybe I'm not searching good enough.
> 

This page has the best breakdown of the various CoCo models that I've found.
http://users.digitalindigo.net/techno/coco2.html

According to that page there were multiple different motherboards all used in machines called 3127B.  I have a Korean 3127B and I'm pretty sure that one of the two NTSC service manuals (26-3026/26-3027 or 26-3134/26-3136) on the archive matched mine but I'm not in a place that I can check it right now.  Maybe, as you said, it was just similar to mine but not an exact match.

Do you have the MC6847T1 VDG?  Starting on page 89, the following book has some info about changes to machines that have the new VDG.

https://colorcomputerarchive.com/repo/Documents/Magazines/Rainbow,%20The%20-%20Full%20turn%20of%20the%20screw/FullTurn.pdf