[Coco] RGB video on CoCo3

[Phill Harvey-Smith]

Steven Hirsch wrote:
> On Wed, 11 Feb 2009, Phill Harvey-Smith wrote:
> 
[snip]
> 
> 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.

Ok some progress, I made up some leads to go from CoCo to veroboard and 
veroboard to SCART so I can do some patching. So far I have :-

RGB on CoCo direct connected to RGB on SCART (plus grounds connected as 
needed).

H & V Sync on the CoCo XOR'd together with an LS86, and the the output 
inverted with an LS04 and passed to CSYNC on the SCART.

This produces a stable picture that is pretty crisp *BUT* in shades of 
almost white, Ii.e. the colour is all wrong :( I tried putting some 
resistors in line incase the voltage out of the CoCo was the wrong 
level, seemed higher than 0.7V when measured with my scope, looked more 
in the 2V range.

Any thoughts anyone ?

Cheers.

Phill.

-- 
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !

"You can twist perceptions, but reality won't budge" -- Rush.