[Coco] Composite Video Mod for CoCo1

[Daniel Campos]

Hi Fedor,

Yes, I saw your post some time ago but the hand written schematics are
not so clear to understand. For the pictures, I can guess that some
wireup got loose on transport.

I just have done the mod described on the MC6847 datasheet, and after
a fine tunning using trimpots, a believe I came with a good overall
image. The pictures bellow, shown the final result on my Color64:

https://picasaweb.google.com/109345699838454178536/LZColor64#5818574442902576802

https://picasaweb.google.com/109345699838454178536/LZColor64#5818574744878407410

https://picasaweb.google.com/109345699838454178536/LZColor64#5818575311739711346

https://picasaweb.google.com/109345699838454178536/LZColor64#5818575226684298914

https://picasaweb.google.com/109345699838454178536/LZColor64#5818574448002174674

https://picasaweb.google.com/109345699838454178536/LZColor64#5818574792157143906

https://picasaweb.google.com/109345699838454178536/LZColor64#5818574797580859266

https://picasaweb.google.com/109345699838454178536/LZColor64#5818575156296252562


Tweaking the trimpots yesterday I came with a good improve on contrast
since those pictures were taken.

Thanks,
Daniel


2012/12/6 Fedor Steeman <petrander at gmail.com>:
> Hi Daniel,
>
> If you search the list, you can read that I posted about this subject a few
> times already earlier.
>
> In short, I acquired a CoCo2 with such a composite video mod that worked
> fine, until I transported it somewhere at a certain moment. I think
> something came loose or short-circuited, because now I only get a black
> screen. It can probably easily be fixed, but I am not that skilled enough to
> do it.
>
> The video mod is based on the following manual (in Dutch):
> http://www.steeman.dk/CoCoManuals/VideoMod_(KoenVaartjes).pdf
>
> Here are some pictures of it:
> https://picasaweb.google.com/115146243402896969496/CoCoVideoMod?authuser=0&authkey=Gv1sRgCKCWiaq64ompugE&feat=directlink
>
> Cheers,
> Fedor
>
> On 3 December 2012 13:48, Daniel Campos <daniel.campus at gmail.com> wrote:
>>
>> Hello,
>>
>> Since I got the Color64 (Coco1 clone) his image, even already having a
>> composite video output, have always disturbed me with a crap image
>> compared to other CoCo machines. So I began to try to correct that and
>> removed the entire transcoder analog pcb that came with the computer
>> and used the schematic bellow to try to have a better composite
>> output:
>>
>> http://www.victortrucco.com/Diversos/MC1000/SaidaAV.JPG
>>
>> The schematic above is largelly based on the driver for color
>> composite video that is showed on the 6847 datasheet. After build the
>> mod, image is great on text mode, sharp and crispy, the problem begans
>> when I got to the graphics mode using artifacting. For example, on
>> Outhouse, the initial screen should be red, but appears with a very
>> pink saturated color, it's impossible to read. Other games, like
>> Draconian and Galagon got very saturated too.
>>
>> My question is, someone here have done any of the scematics bellow and
>> worked fine on a LCD monitor with composite video ?
>>
>>
>> http://www.retrocomputers.eu/wiki/index.php/Tandy_TRS-80_Color_Computer_(CoCo)_Composite_Video_Mod
>>
>>
>> http://sd2cx1.webring.org/l/rd?ring=coco;id=1;url=http%3A%2F%2Fwebspace%2Ewebring%2Ecom%2Fpeople%2Fvt%2Ftheother_bob%2Fcoco_page%2Fccprojects%2Ehtm
>>
>> Any suggestion would be higly appreciated. :)
>>
>> Thanks,
>> Daniel
>>
>> --
>> Coco mailing list
>> Coco at maltedmedia.com
>> http://five.pairlist.net/mailman/listinfo/coco
>
>