[Coco] video composite on korean coco 26-3134A
didier derny
didier at aida.org
Fri Oct 3 15:16:15 EDT 2014
I'll probably order a pcb
My main problem, is that I have absolutely no idea if the coco 2 is working
at all
I tested inside the modulator but I've not seen any signal looking like a
video signal
(no synchro seen)
Is there any other way to know if it is dead or alive ?
--
didier
-----Message d'origine-----
De : Coco [mailto:coco-bounces at maltedmedia.com] De la part de Zippster
Envoyé : vendredi 3 octobre 2014 19:21
À : CoCoList for Color Computer Enthusiasts
Objet : Re: [Coco] video composite on korean coco 26-3134A
Mike,
I made this board to replace the RF modulator box that was in my Korean
CoCo2.
I removed the modulator, and soldered pin headers in where the inputs to the
modulator are. Y, øA, øB, CHB, CLK, Sound, and +5v are all in these
headers.
The area underneath the modulator is pretty much all ground plane, allowing
me to drill mounting holes for the board, and use standoffs to attach it.
Corresponding female headers on the board then just plug into the
motherboard (except for
1 ground wire that needs to be attached). Then I made a cutout in the back
of the CoCo case, basically expanding where the RF connector was. It makes
for a pretty neat installation.
(I’ll put some more pics up later).
I’m not sure if all Korean CoCo2 main boards have the same layout in the
modulator area, but I think we may have the same model, so it should fit.
I know other CC2’s have differing layouts for the modulator area, but it’s
easy enough to lay out a board to fit those (with measurements).
I had also thought of the idea of a board plugging into the MC6847 socket,
and moving it to onto the board, which is a good one. I’m planing on this
approach for a Component Video board I’m working on. It would be pretty
easy to socket non-socketed 6847’s if you’re willing to sacrifice the chip
(utsource has them, I think I paid $5ea for five).
- Ed
On Oct 3, 2014, at 11:17 AM, mike at borncoco.com wrote:
> 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
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Coco mailing list
>>>>> Coco at maltedmedia.com
>>>>> https://pairlist5.pair.net/mailman/listinfo/coco
>>>>> -----
>>>>> Ingen virus fundet i denne meddelelse.
>>>>> Kontrolleret af AVG - www.avg.com
>>>>> Version: 2012.0.2247 / Virusdatabase: 4031/7782 - Udgivelsesdato:
>>>>> 27-09-2014
>>>>>
>>>>>
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>>>>>
>>>>>
>>>>> --
>>>>> Coco mailing list
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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.
>>>>
>>>> --
>>>> Coco mailing list
>>>> Coco at maltedmedia.com
>>>> https://pairlist5.pair.net/mailman/listinfo/coco
>>>
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>>
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