[Coco] vertical lines on screen

[Steve Bjork]

What you are seeing is the video noise of the CoCo's analog video 
system.  As the logic chips (CPU, memory, registers and others) do their 
work, the power supply levels change ever so slightly.  While this 
change does not effect the computer logic chips, it does play havoc with 
the analog circuits.  You can see it from the juggle in joysticks to the 
background noise coming from the cassette out line.

Better filtering on the part of the video circuit would have clean all 
the that video noise.  But so would a more powerful power supply with 
more capacitors on the power supplies pins of the digital parts.  I had 
one CoCo 3 (per-production unit) that I needed to add/replace a few 
capacitors to get the video to a point that I could see my game in all 
the noise.

Steve

P.S. Before you jump in about juggle on the joystick is caused by other 
sources.  Yes, I know that many problems with the joysticks on the 
CoCo,  from unshielded wire to dirty pots to poorly written ADC code 
will cause the joystick  to wiggly all over the place.

On 4/12/2010 4:33 PM, Jeremy Michea wrote:
>
>
>   Hi all, I have a question about the coco 3. I noticed some vertical lines
> on the screen via the video out on the coco 3, particularly when the screen
> is green. Now they seem much more apparent when I'm using a device called
> "easycap" to capture video for youtube videos, such as you can see here:
> http://www.youtube.com/watch?v=F6nrurd29cI
>
> I don't however notice it unless I really look closely if I just have it
> hooked up to my Commodore 1802 monitor. Are these vertical lines a normal
> thing for the coco even when not using the RF out?
>