[Coco] CoCo2 black and gray video only -- need help!

[Dave Philipsen]

Yeah, the truth be known, I suppose the spec is a little more loose than 
that but I've never sat down and measured at which point the average 
television will stop displaying color. So that's one good thing about 
the RGB output on the CoCo 3.  You could be out of tolerance on the 
crystal but the color would still display ok.

Dave


On 10/23/2021 11:12 AM, Keith Monahan via Coco wrote:
> Yeah, will do Dave. What doesn't fill me with joy, however, is that 
> even a brand new in-spec crystal is potentially already too slow. If 
> it still meets spec.
>
> I'm sorry if I'm fixating here, but the Jamco/Arndt Electronics 
> XTAL-14.31818MHZ-HC49U I ordered is a 50ppm crystal. That puts the 
> minimum, but still in-crystal-spec value at 14.31818 * .999950 = 
> 14.31746. This is below the needed 14.31814 that is needed for the VDG.
>
> Digi-key offers better parts -- a 30ppm crystal, which improves 
> things, but the math still doesn't work out.
>
> Maybe that's precisely why they include that trimcap in the design.
>
> Keith
>
>
> On 10/23/2021 11:51 AM, Dave Philipsen wrote:
>> Let us know if the new crystal fixes the problem. I'm curious to know 
>> the outcome.
>>
>>
>> Dave
>>
>>
>> On 10/23/2021 10:43 AM, Keith Monahan via Coco wrote:
>>> Removed TC1 completely. No effect. I think the crystal is too far out.
>>>
>>> Thanks
>>>
>>
>>
>


-- 
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus