[Coco] [HW] Coco 3 video output corrupt when using cart port

[Robert Gault]

Brian Sturk wrote:

>   On a black screen I can see hints of orange 
> and blue.  It's almost like random repainting of the screen *and* the 
> magnetic field effect.  Definitely weird.
> 
> thanks for the help, I'll report back,
> ~telengard
> 

As Tim suggested, re-seating all socketed chips is a good idea even if 
it does not help with this problem. Tandy did not use gold plated 
contacts so a fresh surface can't hurt and could help.

The orange and blue, is that fringing around text with a 40 or 80 column 
screen? If so, it is artifact colors typical of composite video. Some 
screen colors will make the effect worse than others. There is only one 
way to get rid of it completely and that is by patching Basic.
If this is the source of your colors, I'd suggest using a 40 column 
screen with a white background and black letters. Enter
WIDTH40
CLS5

If the orange and blue is artifacts and you get a disk system to make it 
easy to SAVE and RUN programs, the following will turn off the color 
burst signal and remove artifacts.

10 POKE&HE033,16:REM width 32 screen
20 POKE&HE03C,19:REM width 40 screen
30 POKE&HE045,19:REM width 80 screen