[Coco] Bad news, good news...

Stephen H. Fischer SFischer1 at MindSpring.com
Mon Dec 12 00:09:49 EST 2005


I am getting confused as to what the problem is or what is trying to be 

The chip that I used to convert the CoCo 3's RGB output to S-Video for my 
NTSC TV has additional outputs in addition to the luma signal which is part 
of the S-Video signal set  (Chroma & Luma). It may help, It does a great job 
for me putting the CoCo 3 display on my S-Video TV.


Stephen H. Fischer

John Kowalski wrote:
> 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)
> http://www.axess.com/twilight/sock/ 

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