[Coco] Bad news, good news...

John Kowalski sock at axess.com
Tue Dec 13 23:05:14 EST 2005

At 09:09 PM 13/12/2005 -0600, Boisy Pitre wrote:
>> The S-Video looks very nice.  Not quite as perfect as RGB, but  
>> much, *MUCH*
>> better than the U.S. CoCo3's regular composite video.
>No joke!  How did you do the S-Video conversion?
>I still think S-Video would be a cool video option for the CoCo 3.   
>The pictures show that it is quite nice!

Nick Marentes was nice enough to rip the RGB-to-PAL daughter board out of
one of his PAL CoCo3s and sent it to me.  I just changed the crystal to
3.58Mhz, cut a trace to switch the chip to NTSC mode, added a power supply
and cables and put it in a project box.
This generates very nice composite video, but the chip inside also generates
a chroma signal, so I simply tapped that for S-Video.  I didn't find any
place to tap a luma signal, so I have a seperate circuit that mixes RGB into
monochrome video which I use as luma.

S-Video is definitely good enough for 80 columns.  It's very close in
clarity to RGB - except in certain rare cases when two different colors that
happen to have the same luma value are side-by-side.  That's the only case
I've noticed where there is any smudging/color bleeding.

                                         John Kowalski (Sock Master)

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