[Coco] Bad news, good news...

John Kowalski sock at axess.com
Sun Dec 11 13:27:53 EST 2005

At 12:17 AM 11/12/2005 -0500, Roger "Merch" Merchberger wrote:
>Now y'all are telling me that I'm going to have to:
>1) attempt (and prolly fail at this point) to find my CoCo3 Service Manual 
>(to try to figure out where to pick off Chroma & Luma)
>2) burn my fingers yet again with my soldering iron...
>3) and have some fun in the process??? ;-)

Hi Roger,

#1 could be done on older CoCos, but not on the CoCo3 - unless maybe you
have one of them PAL versions.  In the CoCo3, the composite video is
generated directly inside the GIME, so there is no way to tap seperate
chroma/luma signals.

There is a neat way to cheat that, though.  Disto used to sell a monochrome
adapter for the CoCo3, which plugged into the RGB port and output regular
monochrome video.  If you could get your hands on one of those, the
monochrome output is exactly the same as Luma.  If I recall correctly, the
circuit is simply a some resistors and a transistor or two - it takes the
Red, Green, Blue and Sync lines and combines them together into one
monochrome video signal.

The next part is a cheat, but just plug the Coco3's normal color video
output to your monitor's chroma input.  The monitor won't care if there are
extra sync signals and stuff in there, it'll still decode it as a chroma signal.

I've tried this trick a few times and the results were always *much* better
than the CoCo3's regular composite video out alone.  80 column text is sharp
and clear.

                                         John Kowalski (Sock Master)

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