[Coco] Re: Will the *real* artifact colors please stand up?

[Robert Gault]

John Kowalski wrote:
> Brad wrote:
> 
>>Hi John,
>>
>>I dug out the 64k CoCo 2 and typed in your program.
>>
>>Box 1:  Blue
>>Box 2:  A VERY light red pattern (almost white)
>>Box 3:  Red
>>Box 4:  A VERY light blue pattern (almost white)
> 
> 
> So far, it looks like only CoCo 1s generated green and purple in PMODE4.
> CoCo 2s and 3s seem to display very little color for those pixel patterns.
> 
> Well, maybe earlier CoCo 2s displayed green and purple as well..  How old is
> your CoCo 2?  Does it say Tandy or Radio Shack on the metal label?
> 
>                                          John Kowalski (Sock Master)
>                                          http://www.axess.com/twilight/sock/
> 
> 

I believe this can be "corrected" by bleeding some of the video clock 
signal into the output of the MC1372. This was discussed in some Rainbow 
issue, I think.

I had a composite output added to my Coco1 tapped to pin 13 of the 
MC1372, U6. The artifact color was very weak until I connected a small 
ceramic cap to the junction of R37 and pin 33 MC6847 (U9). The other 
lead of the cap was wrapped around (not connected to) the lead to my 
composite output.

The intensity of the artifact colors was greatly increased by this bleed 
through. The procedure (bleed through) may work with a Coco2 but I don't 
see where you could tap a video clock on a Coco3.