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

mike at borncoco.com mike at borncoco.com
Fri Oct 3 12:17:10 EDT 2014 

Ed, I ordered some of your boards from OSHpark. Nice layout! I'll have to open up a Korean CoCo 2 this weekend to see how you made the connections to the motherboard. Any info on what you must remove? If you already discussed this here, just say so and I'll look in the archives later. As you said, it would not be difficult to use clip leads to make the connections for any CoCo2. I am still interested in creating a version that can be plugged into the 6847 socket. I know the other puzzle is that some models of the CoCo 2 have the RF modulator box mounted in different ways - some at 90 degrees to the motherboard. 

Great work on the board and I appreciate the time and effort you put into this and sharing it with all of us! I look forward to assembling the boards when they arrive.

Cheers,
-Mike

-----Original Message-----
From: "Zippster" <zippster278 at gmail.com>
Sent: Friday, October 3, 2014 11:53am
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Subject: Re: [Coco] video composite on korean coco 26-3134A

There was when it was sent, not sure what’s stripping them out.

I’ll list them this way…

https://sites.google.com/site/thezippsterzone/home/coco2-projects

https://oshpark.com/shared_projects/lHtMJ67Z

-Ed


On Oct 3, 2014, at 10:48 AM, Al Hartman <alhartman6 at optonline.net> wrote:

> There's no link in that message...
> 
> -[ Al ]-
> 
> -----Original Message----- From: Zippster
> Sent: Friday, October 03, 2014 10:34 AM
> To: CoCoList for Color Computer Enthusiasts
> Subject: Re: [Coco] video composite on korean coco 26-3134A
> 
> 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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>>> 
>>> -- 
>>> 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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