[Coco] video composite on korean coco 26-3134A

Fri Oct 3 10:46:54 EDT 2014

Cool. I will check it out. Thanks.

Zippster <zippster278 at gmail.com> wrote:

>Hey guys,
>
>You may have missed my earlier post.  I did a version of this circuit in Eagle.
>Sound output is included.
>
>The files are in the zip on this page.  CoCo2 Projects (Tandy Color Computer 2) - The Zippster Zone
>
>I put it up as a shared project on OSHPark.  OSH Park ~ Coco2 Composite Out (Type 01) Rev 03
>
>I laid the board out to replace the RF modulator in my Korean CoCo2’s, but as long as you get
>the signals to it, you could mount it anywhere.
>
>-Ed
>
>
>On Oct 3, 2014, at 7:20 AM, Michael Rowen <mike at borncoco.com> wrote:
>
>> John is indeed correct. I have built the simple circuit that includes a 1372 that connects to the signal from the 6847. It works well on every monitor I've used with a CoCo 2. The circuit is in the data sheet for the 6847. I have not had the time to create a PCB with Eagle. Some CoCos have the 6847 socketed, so it would be easy to make a board that plugs into that 40 pin socket, with the 6847 plugging into the board. CoCo 2s with a soldered 6847, would require 7-8 clip leads, but can be done. I have bread boarded this on a CoCo 2. This was the same method used by the Colorware adapter. I scored one of these at last year's CoCo fest. Its circuit uses more caps, but the principle is the same. I have not found any significant quality differences using the reference circuit. Clean and sharp. Any Eagle experts with some time on their hands to create the PCB files?? :) It will probably be Christmas time before I get the chunk of time to tackle this. I'm a newbie with Eaglecad. I'll try to post a video this weekend.
>> 
>> Cheers,
>> Mike Rowen
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> "John W. Linville" <linville at tuxdriver.com> wrote:
>> 
>>> NTSC CoCo2's use a modulator that does _not_ take a composite video
>>> input.
>>> 
>>> The 6847 outputs signals called Y, phiA, and phiB.  These are (very)
>>> roughly analogous to the YIQ signals that form a composite video signal.
>>> A Motorola 1372 chip is used to combine those signals into something
>>> useful.  The 1372 chip can produce either a baseband composite video
>>> signal or (by use of an RF tank circuit) a TV-compatible radio signal.
>>> 
>>> On the Coco1, the 1372 only produced a composite video signal that
>>> was then fed (along with the audio signal) to an off the shelf RF
>>> modulator.  On the CoCo2, the 1372 chip is only included as part of
>>> the RF modulator itself.  The Y, phiA, and phiB signals go straight to
>>> the modulator where the RF-equipped 1372 turns them into a TV signal.
>>> 
>>> I'm not sure if there is a pristine composite video signal available
>>> anywhere inside the RF modulator on a CoCo2.  I was never able to
>>> find one, FWIW.  You probably need to pull the modulator and build
>>> a new 1372-based circuit to replace it.
>>> 
>>> Good luck!
>>> 
>>> John
>>> 
>>> P.S.  It sounds like the PAL CoCo2 might be designed more like the
>>> CoCo1 in this regard.  Of course, that only helps you if you are
>>> using a PAL CoCo2... :-)
>>> 
>>> On Thu, Oct 02, 2014 at 09:56:31PM +0200, didier derny wrote:
>>>> Hi,
>>>> 
>>>> I tried but no success...
>>>> 
>>>> I don’t have any image on tv (connected to the antenna)
>>>> No idea if the coco 2 is broken or if my tv is unable to process the signal
>>>> 
>>>> With the oscilloscope I've not been a able to find a composite signal 
>>>> Inside the modulator...
>>>> 
>>>> Any idea ?
>>>> 
>>>> Thanks
>>>> 
>>>> 
>>>> --
>>>> didier
>>>> 
>>>> -----Message d'origine-----
>>>> De : Coco [mailto:coco-bounces at maltedmedia.com] De la part de Simon Jonassen
>>>> Envoyé : samedi 27 septembre 2014 16:26
>>>> À : 'CoCoList for Color Computer Enthusiasts'
>>>> Objet : Re: [Coco] video composite on korean coco 26-3134A
>>>> 
>>>> Hey....
>>>> 
>>>> I did mine by tapping into the feeds that go directly to the rf
>>>> modulator....
>>>> 
>>>> A couple of shielded wires soldered on to the pins and 2 rca jacks on the
>>>> rear of the case (audio/video)
>>>> 
>>>> Works fine... No extra components needed (PAL machine)... 
>>>> 
>>>> /Simon :-)
>>>> 
>>>> 
>>>> -----Oprindelig meddelelse-----
>>>> Fra: Coco [mailto:coco-bounces at maltedmedia.com] På vegne af didier derny
>>>> Sendt: 27. september 2014 13:23
>>>> Til: 'CoCoList for Color Computer Enthusiasts'
>>>> Emne: [Coco] video composite on korean coco 26-3134A
>>>> 
>>>> Hi
>>>> 
>>>> Is there an easy way to get a video composite signal on this machine ?
>>>> 
>>>> I guess a video composite signal or something approaching should be found
>>>> Somewhere near the modulator or inside the modulator ?
>>>> 
>>>> 
>>>> Thanks
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> --
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>>>> 
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>>>> 
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>>> 
>>> -- 
>>> John W. Linville		Someday the world will need a hero, and you
>>> linville at tuxdriver.com			might be all we have.  Be ready.
>>> 
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>> 
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