[Coco] Bad news, good news...

[John Kowalski]

Hi Steven,

Roger was asking if there were a place to simply tap the chroma & luma lines
inside a CoCo3, and there isn't because they do not exist inside the CoCo3.
I just mentioned that a way to cheat and generate "chroma" & "luma" signals
on the CoCo3 is simply to take the RGB video and turn it into monochrome
video (use as luma) and use the regular unmodified video output as the
chroma signal.

Yes, an RGB to composite encoder chip will give you chroma/luma too (and a
better quality chroma at that).  My suggestion was just a quick way to try
out S-video on the monitor without having to order or wait for parts.


At 09:09 PM 11/12/2005 -0800, Stephen H. Fischer wrote:
>Hi,
>
>I am getting confused as to what the problem is or what is trying to be 
>done.
>
>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.
>
>http://www.analog.com/en/prod/0,2877,AD723,00.html
>http://www.analog.com/en/prod/0,2877,AD724,00.html
>http://www.analog.com/en/prod/0,2877,AD725,00.html
>
>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/ 
                                         John Kowalski (Sock Master)
                                         http://www.axess.com/twilight/sock/