[Coco] vertical lines on screen

[Gene Heskett]

On Tuesday 13 April 2010, Steve Bjork wrote:
>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

Unforch, those comments apply equally well to the coco mice Steve.  I finally 
gave up an switched to a serial mouse, total end of problem.

>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?
>
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>


-- 
Cheers, Gene
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