[Coco] Re: [Color Computer] Re: i've almost found.

[Torsten Dittel]

> > I have also a version with RF but RBG is much better quality of
> picture, no
> > interference.

Bon soir Cedric,

I'm from Aachen (Aix-la-Chapelle), Germany. Je regrette, mais
malheureusement je ne parle pas francais... (I learnt a little bit in
school but not very successful ;-)).

I've got several PAL 240V 50Hz MC-10, CoCo1, CoCo2 & CoCo3 but I can't
imagine how to get an RGB signal out of a CoCo2.

The CoCo's 6847 chip does not present RGB outputs (which would be very
useful but require more pins than available). Instead it presents the
colour information using two signals that are convenient for NTSC colour
carrier modulation (not PAL, needs some additional cicuits).

The 6847's video signals Y, CHA and CHB have 3 possible levels during
the active display area: low, medium or high. Medium is about 1.5V. So
extracting the RGB colour information from a 6847 involves level
comparators for the CHA, CHB signals then applying some boolean logic
through individual TTL gates. This will lead to a TTL RGB signal, still
not what you need for a TV RGB in. It won't display the "Buff" and
"Orange" colors correctly neither.

Could you send me the model no. of your CoCo2 and describe what you made
exactly?

Thanks and regards,
Torsten