[Coco] composite / s-video to hdmi

[Luis Antoniosi]

Not true. Most of the TVs supports 15.75 Khz only through s-video,
while the VGA port accepts only 31 Khz.

It's only a matter of firmware but that's the way they work. Very few
will support VGA 15.KHz and when does so, doesn't support coco3
inverted sync. You still need to mod your coco3.


On Mon, Dec 17, 2012 at 1:46 AM, John E. Malmberg <wb8tyw at qsl.net> wrote:
> On 12/16/2012 11:48 PM, Gene Heskett wrote:
>>
>> On Monday 17 December 2012 00:26:02 John E. Malmberg did opine:
>>
>>> Which means that they can handle the 15.75 NTSC time signal.
>>
>>
>> Thru the composite jack?  Have you ever tried to read the coco3's 80
>> column
>> screen thru a composite hookup, or on an ntsc tv?  Difficult if not near
>> impossible.  The bandwidth in the NTSC circuit simply is not there.
>
>
> No, through the SVGA jack.
>
>>> There are reports that the COCO 3 could work with Multi-sync monitors if
>>> they supported 15.75 Khz sync, and I previously posted a link.
>>
>>
>>> And all the flat screen TVs that I have come with an SVGA connector.
>>
>>
>> Which, with Chris Hawks adapter, should work noticeably better than any
>> composite setup, whether direct composite or rf modulated composite.
>
>
> If the TV supports 15.75 Khz, then it probably supports it through the SVGA
> jack.
>
> The reason it was scarce in computer monitors is that it required a more
> expensive flyback circuit.
>
> But as you know, there is no flyback circuit in modern LCD TVs.  So no real
> reason for the multi-sync circuit to not support 15.75 Khz from any the
> sources on the TV.
>
> Now this also may be something that works in most TVs and not others. It
> just may depend on what is cheaper, having the multi-sync circuit work down
> to NTSC frequencies or having to double the NTSC lines from the composite
> video stream.  My guess would be not having the doubler circuit would be
> cheaper.
>
>>> Unfortunately my COCOs are still boxed up, so I have not been able to
>>> try it a SVGA to COCO cable to see if it just works.
>>>
>> Don't forget John, that I am a broadcast engineer, who has been making
>> sure
>> there was a picture there when you turned on the tv, from 1962 to 2002, 40
>> years.
>
>
> I only did the broadcast engineering for my last year of college, about 1981
> to 1982.  To give you a hint as to where, along with the TV transmitter at
> the site I was at, there also was the most powerful commercial FM
> transmitter in the U.S.
>
> Regards,
> -John
>
>
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