[Coco] RGB video on CoCo3

[Steven Hirsch]

On Wed, 11 Feb 2009, Phill Harvey-Smith wrote:

> Ok, so I've pulled my CoCo3 out of storage because I need to test something 
> on it, and am really quite disapointed with the quality of the  composite 
> video display on my LCD TV. Though the TV is fine with other machine's 
> composite (Dragon included, but then that like the CoCo 1/2 uses a 6847 
> instead of the Gime).
>
> So I know the CoCo3 has an RGB port on the underside of the board, that I can 
> hopefully use to drive the TV/monitor, which as well as composite and ariel 
> input also has SCART and PCVGA inputs, both of which I know work fine and 
> display a nice crisp picture with a variety of retro systems.
>
> So how can I go about utilizing this port, if it's going to be a problem the 
> CoCo3 is of a US NTSC model, and though the TV is a UK PAL model, it is also 
> capable of displaying an NTSC picture fine (tested with a Tano Dragon, and an 
> MC-10).

The main problem you're facing is that RGB SCART requires composite sync, 
while NTSC CoCo 3 systems (and maybe PAL, but I've never seen one) have 
separate H & V sync.  I ran into this trying to interface my CoCo to a 
scan converter that uses SCART.  If you're handy, there's a simple circuit 
to recombine H & V to composite.  I plan to knock this together Real Soon 
Now and play with it further.

Steve


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